US 2926615 A
Description (OCR text may contain errors)
March 1960 I. E. CQFFEY 2,926,615
ELECTRO-DYNAMIC FUEL PUMP Filed Jan. 28, 1954 2 Sheets-Sheet 1 78 V 5/ GD & 5/ F l 6.6. F IG.7. FIG.8. 52 77 INVENTOR.
IRVEN E. COFF'EY VATTORNEZL 2 Sheets-Sheet 2 l. E. COFFEY ELECTRO-DYNAMIC FUEL PUMP March 1, 1960 F l G. 3.
INVENTOR. IRVEN E. COFFEY g v7 FM ATTORNEY United States Patent ELECTRO-DYNAMIC FUEL PUMP Irven E. Colfey, Clayton, Mo., assignor, by mesne'assignments, to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Application January 28, 1954, Serial No. 406,762
20 Claims. (Cl. 103-152) This invention relates to electrically driven reciprocating pumps, and more particularly to pumps for the fuel supply system on automotive equipment.
Electric pumps adapted for this purpose are well known in the art, and several commercial types are readily available on the market. Generally speaking, such pumps are constructed with a flexible pumping element of some kind connected directly with the core of a solenoid motor or the armature of an electromagnetic type which, during operation, moves the flexible pumping element during the suction stroke against the resistance of a strong spring. At the end of the suction stroke, a pair of breaker points is operated to break the electric circuit to the field of the solenoid motor, whereupon the spring takes over exclusive control of the flexible pumping element during the discharge stroke. With this type of pump, serious diificulties have been encountered in preventing arcing and consequent burning of the breaker points during opening movement. In order to minimize this defect, numerous mechanisms, both electrical and mechanical, have been suggested and some resorted to in commercial devices. The art will reveal to those interested many mechanical devices for producing a fast breaking action at the points to reduce the duration of arc, chambers of inert gas to reduce oxidation, and many electric devices including resistors and/or capacitors. All of these devices are deemed necessary because of inherent characteristics of the type of motor, as the following careful analysis will establish.
The advantages of the instant invention can best be explained by a comparison of its electrodynamic and hydraulic characteristics with prior art devices. It becomes apparent for such a comparison that a vast improvement has been made by this invention, not only in the function and results achieved, but also in the expected life of the motor and the duty cycle of the pump.
Electric drive motors The electric motors customarily used and deemed acceptable in the prior art were either of the non-polar soleacid type or of the modified clapper type. All of these are high inductance types of electric machines in which the force generated varies inversely as the square of the ratio between the number of ampere turns and the length of the air gap in inches. This is expressed by the following equation:
2 P= 1AA X pounds (Equation 23, Pender and Delmar, 6-35, fourth edition.)
If the motor is an electromagnet and is bi-polar, then a similar, more exact equation applies wherein the cross- .section (A) of either equal-area poles in square inches must be taken into account. The equation then becomes:
In these equations (P) is the total pull in pounds, (NI) completion of the power stroke.
is the total ampere turns of the coil, (1,) is the length of the air gap in inches, and (1 is the airgap equivalent of the reluctance of the iron, thus including a correction in the first equation for the magnetic character of the core.
From this equation it becomes apparent that, for the constant pull, the required ampere turns varies directly with the air gap, because the pull in pounds depends upon the square of the flux density produced by the field coil. For a motor of this type, assuming a predetermined stroke, the maximum air gap will be a fixed amount. If the initial required pull (P) in pounds is known, then the number of ampere turns is fixed by the above equation. Whatever number of turns is required to produce the initial pull, this number will create a variable force increasingapproximately inversely as the square of the length of gap so that it becomes excessive towards the The longer the gap, the greater is this effect. Concomitantly, the inductance of the field coils or windings similarly increases as the gap decreases, regardless of the number of ampere turns. These facts are determined characteristics of the nonpolar type of motor. They are invariable, and necessarily determine its operating characteristics.
The above deductions apply to any practical design for a motor of a non-polar type, and it must be taken into account that the force generated varies directly as the square of the ratio of the number of ampere turns to the length of the air gap in inches. It follows that, in a practical design, (NI) must be large enough to overcome both the initial resistance of the spring to compression and the resistance of the pump. In other words, the motor design for this type of machine must have sufficient pull (P) on the armature at the beginning of the suction stroke, which is the most unfavorable condition for power generation, but, nevertheless, one of the design criteria. Since the turns on the coil (N) for a given current (I) will increase directly with the length of the air gap, it becomes obvious that it would be economically unfeasible to use anything but an extremely short stroke.
Motor design based upon the above equation also dictates the use of a very short stroke motor because the current (I) is also a direct function of the length of the air gap for a given number of turns (N). Because of these design criteria, it can be said that the longer the stroke used, the greater number of turns required, and the larger the wire gauge inth'e coil to maintain a given curent (I) for a constant voltage source. This implies .an increase in overall coil dimensions.
Concomitantly with the increase in (NI), it follows that the inductance of the field coils or windings similarly increases, and the inductance is similarly a function of the gap distance. This is easily seen from the following considerations: Firstly, a defining relation for inductance is (where L is the inductance and p is the total flux linking the N turns of the winding). Now, since the pull of the magnet may be written as Thus, the minimum inductance (L increases linearly Patented Mar. 1, 1960 5 both with the required pull (P) and gap length-or useful motion(l), for a constant current in the coil.
But, this is the minimum inductance at maximum air gap'opening. As the motor operates, closing the gap, this minimum inductance L is exceeded greatly, as deduced below.
High inductance is a characteristic in a motor design of the non-polar type producing other etfects which must be taken into consideration because it can 'be shown that operating speed will depend on the inductance of the coil when the gap is open.
It is a fact that the inductance will increase directly as the square of the number of turns in the coil, that the rate of flux development determining the strength of the mechanical pull -is variable directly with inductance, and that, therefore, the inductance of the coil determines maximum motor speed.
For, if '(L) is the inductance, (Q) the total reluctance, i.e., (Q) being the sum of (Q the reluet'ance er the gap, and (@Qthe reluctance of'the iron, where (N) is the number of turns in the field coil, then the inductance is determined by the equation 1 i 2 L N a+ a It can be assumed that is small and that, when the gap is open, (fi will have finite value. As the ap is closed, however, (fi must diminish towards zero. Consequently, the inductance (L) must vary inversely as the width of the gap, and the maximum inductance L greatly exceeds L It follows that the rate of current buildup in the coil will vary according to the amount of inductance in the circuit. Since the flux generated is a function of the current, the motor speed depends upon the rapidity with which the current reaches full value. The time required for the current to reach its full value upon the quotient inductance (L) divided by the effective resistance v (R) of the circuit. The larger this ratio of L)/ (R), which is called the time constant of the circuit, the longer the time required for the current to reach its full value. A typical current-time curve plotted first for a condition when the gap is open would indicate a current rise (di/dt), depending upon the ratio of inductance to resistance (L (R) at the instant of closing the switch E dt Z This curve may be plotted from the equation:
(i) being the current, (E) the voltage, (R) the resistance, (e) the base of natural logarithms, (t) the time, and (L the (minimum) inductance at maximum air gap.
As the plunger moves, the flux increases, thereby causing a counter electromotive force which tends to reduce the current an amount depending upon the speed of operation of the plunger. At this point in the curve, for a condition of actual load on the plunger or armature, the current in the coil may remain constant or drop slightly as the plunger moves toward the end of its stroke. After the plunger reaches the end of its stroke, say at a time (T) milliseconds after closing the switch, however, the current again increases and gradual- 1y reaches a value which is dependent upon terminal voltageand the resistance of the coil (R). This portion of the curve can be plotted from the equation:
"where -L,, is the maximum inductance with the air gap closed, and i(T) is the instantaneous current at the end of the stroke. This part of the current-time curve will have a much more gradual slope (di/dt) than that portion of the curve when the gap is open, because of the fact discussed that (L) increases as the gap decreases. It follows from this that, if a high speed device is desired, then it is advantageous to maintain low inductance in the coil so as to provide "a rapid rate of increase of mechanical pull (P).
The high inductance of the non-polar type motor also adversely affects electrical commutation by any mechanism for making and breaking the circuit by contact points mechanically operated by the action of this motor.
The expected life of thepoints will depend in great measure upon the counter electromotive force generated by the collapse bf the aux around the coil, when the coil circuit is opened. This voltage (a is a function of the product of inductance :(L), in henr'ys, and the time rate of change of amperage (di/a'f), in amperes per second. The larger the current in the coil to actuate the plunger, and the greater the inductance of that coil due to the number of ampere turns required for the designed initial pull (P), then the greater, of course, will be the counter electromotive force (a generated by the opening of the coil circuit by the points. This high counter-electromotive force is the major cause of arcing and 'pitt'ingof the contact points. It is well known that anindu'cta'nce free circuit is easily interrupted.
It is clear that this is 'the principal cause for the great difiiculty in commutation, that is, opening of the coil circuit by means of mechanically actuated switches in the form of circuit breaker poirits. In other words, the solenoid type of motor requires 'breakingof the coil circuit at the point of maximum inductance, maximum current, maximum pull, and maximum "counter 'electromotive force, all of which contribute to commutation difficulties.
As above pointed out, the non-polar type of motor design would be a compromise determined by the parameters set forth in the above equations, and it can be easily deduced therefrom that the life of the coil circuit breaking points will necessarily be comparatively short if the motor is to have a stroke longenough to be eftective in a pump. The 'lifeo f "the 'points can be extended by the use of some or all of the means aforementioned, but experience has shown the life of the points, neverthelessyto be definitely limited.
The disadvantages inherent in prior motors can be contrasted directly with ap'plica'hts elec'tro-dyn'amic type of motor, wherein the gap length is constant, and the circuit opened is not the high inductance field circuit, but the armature which is 'a coil of comparatively few turns and very low inductance. The force generated throughout the stroke by the electrodynamic motor is constant, which is mechanically beneficial in pump actuation.
Brief description of the invention In order to avoid the disadvantages of extremely limited stroke imposed by motor characteristics inherent in prior art devices, the present invention substitutes an electro-dynamic type of motor for the non-polar solenoid types and similar machine's previously used. An electrodynarnic motor provides a motive power capable of unlimited stroke and satisfactory operation from a source of current that is either 'direct or reversing direct current,
in either case when appropriately interrupted in the machine. A source 'of alternating current of low frequency is also suitable as a power source. This is a radical depar-tore from the prior art, and solves many of "the problems which attach to the solenoidtype of motor, as will be subsequently pointed out.
According to the present invention, an electric motor is provided for actuating the flexible pumping element on the suction stroke. This motor is provided with an electrically or permanently magnetized stationary field, and a movable armature mechanically connected to the fiexible pumping element. The field of this motor is constantly energized, or is permanentlymagnetized, as the case may be, to provide a magnetic flux across an air gap which is of constant strength and within which the armature winding operates. The armature winding may be intermittently energized by a pair of breaker points connected to a unidirectional direct current source and operated through a lost motion connection with the armature support. At the beginning of each suction stroke, the points close, energizing the armature, and thereby compressing a spring. At the end of each suction stroke, the points are opened and the armature de-energized, so that the pump discharge may be effected by the compressed spring, which can operate the flexible pumping means and return the armature to a position wherein the points are automatically closed to effect the beginning of the suction stroke. Where the power source is a reversing direct current, double contact points can selectively reverse the current in the armature at the end of each stroke, and the drive connection between the armature and the pump can be through a suitable spring. Where the power source is an alternating current of approcontribute to this characteristic of small inductance.
(l) The small number of turns necessary in the armature to produce the desired pull.
(2) The complete independence of the flux systems set up by thefield coil or winding and the armature coil or winding.
Considering, first, point (1) above, the pull generated in any motor is expressed by the equation P=kBli where (B) is equal to the air gap flux density produced by the independent field winding, (1) is the total length of the turns on the armature, and (i) is the current in the armature. The factor (k) is a suitable constant depending upon the system of units used. Since (I) is equal to 211- times the radius of the coil times the relatively small number of turns (N) of the armature, this expression may be substituted into the above equation. Then the equation becomes P=k21rrBNi. From this last equation, if k21rr is regarded as a constant for a given machine, then pull (P) becomes a function of the three variables, (B), which is the independently produced gap flux density of the field, times (Ni), the ampere turns of the armature. It follows that, if (B) is independently produced by a separate field coil of comparable size and strength and generates the same air gap flux density as the coil in a solenoid such as those above discussed, then the initial pull (P) of the electrodynamic motor armature can be attained with a small NI in the armature circuit. This naturally leads to a lower inductance for the latter motor.
With respect to point (2) above, the armature winding which is supported on a core of paramagnetic material is so arranged that its magnetic lines of force are generally at right angles to those generated by the field winding. This means that there is no mutual inductive coupling between the armature coil and the field 6 winding, and therefore inductance of the armature coil is not affected by the design of the field windings. It remains a constant which in the present design is independent of the armature motion, and is independent of the design of the field coil, even though the latter is of relatively high inductance.
In a machine in which the inductance of the circuit to be interrupted is small and constant, it follows that the induced counter-electromotive force will be but a small fraction of that produced by the interruption of the circuit of other magnetic machines of the solenoid type, for example. To substantiate, the equation for the counter electromotive force as previously given Where the inductance is small, it is obvious that (e will be markedly reduced in amount from that in prior types of machines. As a consequence, this machine lends itself readily to the use of a small capacitor in the circuit. The advantage fiowing therefrom is that it becomes economically feasible in this machine to obtain the well known advantages and results with only a small, inexpensive capacitor in the circuit.
Where a small capacitor is used in parallel with the armature winding in the instant invention, the effect will be similar to and have all the advantages of a large capacitor in the circuit with the field coil of an electromagnet. These advantages are well known and are set forth on page 391 of Electro-Magnetic Devices, by Roters, published by John Wiley & Sons (1941). It will also have additional mechanical effects otherwise unattainable by any commercial, non-polar type motor. In an electrodynarnic type, wherein the circuit is interrupted under load, the collapse of the magnetic field charges the capacitor with a polarity opposite that of the power source. Instantly thereafter, the charge taken on by the capacitor discharges into the armature coil, producing a momentary current and a reversal of the armature flux. Due to the mechanical or hydraulic loading on the machine and the internal electric resistance of the armature winding, the discharge of the capacitor will have the effect in the armature of a unidirectional and clamped surge. The energization of the armature winding or coil by the capacitor discharge creates sufficient reaction in most instances to help arrest the movement of the armature and assist the spring action at the beginning of the discharge stroke of the pump because the surge is opposite in polarity to the applied current.
According to this invention, the mechanism for operating the breaker points to interrupt the circuit to the armature coil is so constructed that, not only a rapid and complete circuit breaking action is obtained, but also a wiping action is produced between the point surfaces, all of which will benefit the action of the points materially and improve their service life. Due to this novel arrangement, the points are self-cleaning in action and, in order to enhance their etficiency in this respect, the point surfaces are made discontinuous in a novel manner, so that a sure contact will be made by facilitating a convenient path of escape for any foreign matter which may be present on the constant surfaces and subsequently removed by the cleaning action.
According to this invention, the motor circuit is provided with a separate pair of contacts in parallel with the breaker points which may be operated by a manual button exposed through the casing of the pump. By the manual operation of this button, the pump may be primed, or may be manually operated to clean the breaker points should they fail to properly function due to the temporary poor contact between the breaker points.
In direct contrast to the function produced by the non-polar type of motor, this invention has electric motor characteristics which materially contribute to long life '3' and durability. The use of a motor having a constant air gap and low inductance when the coil circuit is opened will minimize arcing of the points when the armature circuit is opened, and low inductance makes it practical both electrically and economically to enhance this characteristic by the use of a capacitor. The mechanical features for actuating the points, and their special design, contribute to reliability. V
In direct contrast to the pump operation by the non polar electric motor, the instant invention applies forces to the pumping element which are constant and uniform throughout the suction stroke. This is important to the durability of the mechanism and hydraulic elements of the pump.
The drawings show several embodiments to illustrate difierent modes contemplated for carrying out this invention. The description and illustration is not intended to limit this invention, but is merely exemplary. v
Fig. 1 is a vertical section of an electrodynamic fuel pump according to the present invention.
Fig. 2 is a vertical section of a modified form of an electro-dynamic fuel pump according to the present invention.
Fig. 3 is a diagrammatic view illustrating the electric circuit used in Figs. 1 and 2.
Fig. 4 is a fragmentary sectional view illustrating the mechanical action which takes place during separation of the breaker points.
Fig. 5 is an enlarged view of a part of 'the circuit breaking mechanism.
Figs. 6 to 8 show separate embodiments, of breaker points usable with the present invention.
Fig. 9 is a detailed view of the support for the breaker points.
in Fig. 1 is shown an electrodynamic fuel pump accord ing to the present invention, which has a motor casing generally indicated as 1, a pump valve body generally indicated as 2, and a dust cap generally indicated as 3 for enclosing an electric switching mechanism. The
valve body 2 may be secured to the motor casing 1 in any suitable manner, usually by cap screws (not shown) in the abutting flanges 4 and 5. The valve body 2 is provided with an inlet 6 suitably threaded for connection with the fuel line leading to the tank. An outlet 7 in the valve body 2 is likewise suitably threaded for connection with a line leading to the engine of the motor vehicle. From the inlet connection 6 a passage 8 connects with a valve port 9 containing an inlet valve 10 and its valve cage and spring mechanism. The inlet passage 8 may be provided with an air dome, if desired, such as conventionally used in the mechanical types of fuel pumps, as shown in Coffey application Serial Number 317,498, filed October 29, 1952, for Fuel Pump Dome Structure. The discharge connection connects by way of a passage 12, similar to passage 8, with an outlet valve port 13 containing outlet valve 14 and its supporting cage and spring.
It is contemplated that in the manufacturing process, the valve body 2 will be formed with a central aperture 16 extending therethrough from the exterior into the pump chamber below the valves 10 and 14. This aperture or bore 16 receives a nylon bushing 17 within a countersunk portion 18 of the bore 16. This bushing is suitably sized to slidably receive a portion of the stem 20 for guiding its upper end during its reciprocating motion. In order to limit this motion, it is desirabie to provide a resilient stop such as the rubber cushion 22 secured in place by the plug 23.
A diaphragm 24 is clamped in sealed relation between the flanges 4 and 5 of the motor casing and the valve body, respectively. The stem 20 of the motor is secured centrally of this diaphragm 24 between flanges 25 and 26 on the stem 20 by suitable fibre washers adjacent the flanges, which maintain the backing plate 28 and the motor armature 29 in Snug and sealing engagement with the diaphragm 24. Stem 20 extends downwardly through a bore 30 of a field core 31 within the motor casing. Within the bore 30 is a spring 32 seated at the bottom of the bore and biased against the lower diaphragm retaining washer 33 adjacent the flange 26 on the stem 29. The stem, in turn, is guided at its lower end by a nylon bearing 35 and extends completely through the core 31 for 'actuaing the switch mechanism for the motor. In order to limit the movement of the stem 20 on the suction stroke, a rubber'O-rin'g 36 is exposed to contact by the lower surface of the motor armature 29. A recessed seat 37 is provided in the upper surface of pole piece 39 to retain the rubber Q-ring 36. Pole piece 39 of soft iron can be secured to the iron core 31 by pressfitting, or the like, and the iron motor casing 1, the core, 31, and the pole piece 39, form a single unit defining a cavity 49 to receive the field windings 41 for the electrodynamic motor. The armature is a molded plastic body supporting a cylindrically formed armature winding 43 for the electrodynamic motor. This winding is located within an annular space formed by an air gap between the two pole faces of the field for the motor, and, during the pumping stroke, the windings 43 are limited in their travel to a path wholly enclosed within the projected area of the pole piece 39.
When the field coil 41 is suitably energized, opposite magnetic poles will be set up across the gap between the motor casing and the pole piece 39. On energization of the winding 43 by the circuit breaker mechanism later described, an 'electromotive force will be generated by the flow of current in the winding 43in a suitable direction to draw the stem 20 and diaphragm 24 downwardly, thereby pulling fuel through the connection 6, passage 8, and intake valve 10 to fill the pump chamber. Before the windings 43 emerge from between the field pole faces, the. circuit through the armature coil 43 is deenergized by the circuit breaking mechanism above referred to, thus permitting the spring 32, which was compressed during the suction stroke, to expand, forcing the fuel through outlet valve 14, passage 12, and outlet connection 7. At the end of the discharge stroke, the circuit breaker is again closed to energize the winding 43 of the armature, and the duty cycle of the pump is repeated. Ordinarily, during the operation of the pump, the bumpers 22 and 36 will have very little limiting effect 'upon the stroke of the pump, since the length of stroke will be controlled almost exclusively by the opening and closing of the circuit breaker. However, it is contemplated that, due to mechanical or hydraulic conditions, or due to maladjustments which can occur, it would be desirable to provide these resilient stroke-limiting means for a commercially acceptable design.
The circuit-breaking mechanism for interrupting the circuit in the armature winding 43 is enclosed within a dust cap 3 suitably secured to the motor casing 1. This circuit-breaking mechanism may comprise either single or dual fixed contacts 50 suitably supported as by riveting, or otherwise, to a bracket 49 connected with ground terminal 60. Cooperating therewith are single or dual movable points '51 mounted on a flexible spring steel support 52 by rivets or other suitable means. A bar 53 of insulating material is removably secured 'to the motor casing 1 by the screws 54, or the like, and to its outer end is riveted the spring support 52 by a suitable rivet, or the like, 55. A connection from rivet 55 extends to the positive terminal 70.
In order to hold the fixed and the movable contacts 50 and 51 securely in engagement and maintain a dependable electric contact therebetween, the circuit-breaker mechanism is provided with a magnet 71 formed as a part of the motor casing 1. The spring support 52, which is of steel and flexible, as abovepointed out, has an outboard end whieh is attracted to the magnet 71. The action of the magnet tends to deflect the outboard end of the steel strip slightly when the points are in contact,
so as to place the contact points 50 and 51 in compression in a resilient manner.
In order to actuate the circuit breaker, stem 20 carries a flanged ferrule 74 of insulating material, which may be secured to the lower end of stem 20 by a pair of snap rings 75 and 76 engaging suitable grooves in the stem 20. Ferrule 74 is received in an aperture 77 formed in an enlarged portion 78 of the contact support 52.
Referring to Figs. 6, 7, and 8, which show various forms of contact faces for the points 51 and 52, it is apparent that the surface of the points may be variously modified to provide an interrupted contactsurface. This may be done by forming a rectangular groove, a V- shaped groove, or grooves which intersect. The purpose is to allow for theescapefrom the contact surfaces of any foreign particles which may become lodged therebetween. This cleaning action is aided by the particular breaking action imparted'to the points by the action of the magnet 71 and flexible point support arm 52, which is shown in a slightly exaggerated form in Fig. 4. During the downward movement of the stem 20 and ferrule 74 on the intake stroke of the pump, a stage of action will be reached wherein the upper flange of the ferrule 74 engages the point supporting spring arm 52. Because of the action of magnet 71, the points will not immediately separate, and continued downward motion of the stem 20 merely deforms the center portion of the flexible spring support for the points, forming therein a shallow loop. As a result, it follows that the point surfaces, instead of separating immediately, will be wiped together in the manner shown in Fig. 4. This is due to several features of the flexible spring support and its co-action with the permanent magnet. The flexible spring support for the contact points has a wide, relatively stiff portion supporting the points, and this portion may be of equal dimension whether single or double points are used. Obviously, because of its area, it will resist separation of the points during the initial action of the stem 20. On the other hand, the apertured portion of the flexible spring support is of much less width, and therefore relatively flexible, so that deformation will take place in this portion, and not in the point-supporting portion. As the stem descends, therefore, the first action is, not to separate the points, but to wipe the point surfaces, one over the other, and this will be permitted by the action of. the magnet, the resistance of which to direct separation by openingthe points is strong, but is characteristically weak to resist forces in sheer between the surfaces. This initial wiping action will simultaneously tension spring arm 52 to produce a load and fire action for direct separation of the points. Due to the loading of the spring arm 52, breaking of the circuit to the armature coil by separation of the points will be rapid. This cycle of operation'insures smooth point contact surfaces throughout the life of the pump, and rapid breaking ofthe circuit.
Within the dust cap 3, and attached thereto, is a condenser 80 with leads extending therefrom connected in parallel with the points of the circuit breaker, as described hereafter in the explanation accompanying Fig. 3.
The modified form of the invention shown in Fig. 2 differs from that above described in Fig. 1 in the hydraulic circuit rather than in motor construction. Only these differences will be described here in detail, it being understood that in further respects Figs. 1 and 2 are the same. Where the parts are the same, the same reference characters will be applied.
The motor casing 100 is flanged at opposite ends for assembly with a flanged pump section 101 containing. a pump chamber 103 and for assembly with a flanged dome section 102. Abutting flange 104 on the pump section is fastened to flange 105 onthe motor casing by cap screws'or the like (not shown). The flanges 106 and 107 on the motor casing and the fluid dome section 102. are similarly fastened together.
The dome section 102 forms a casing for the circuit breaker mechanism and also mounts condenser 80, all in the same fashion as does dust cap 3 in Fig. 1. In this modification of the invention, the circuit breaker and motor casing are filled with fuel for motor cooling purposes. The fuel enters a suitably threaded connection 109. A plurality of fluid passages 110 connect fluid dome 102 to the interior ofthe motor casing by way of a bore 30. The passages 110 and bore 30 are, in turn, connected to the pump chamber 103 by fluid passages 111 which penetrate the armature support 29, diaphragm 24, and the backing plate 28, etc. The fluid flow through these passages is controlled by flexible intake valve 112, of rubber or the like, mounted on the stem 20 within the pump chamber 103. An outlet port 113 for this pump chamber is controlled by an outlet valve 114 and connects by way of a passage 115 with a suitably threaded outlet connection 116.
In this modified form of pump shown in Fig. 2, the operation of the motor is the same as described in Fig. 1, and as the stem 20 is reciprocated, the fluid will be drawn into the fluid dome 102 through inlet connection 108. When the dome fills, the fluid will enter the motor casing, and continued operation of the pump will expel any air or gases from the casing. Eventually, fluid will enter the pump chamber past check valve 112 and will be expelled past the outlet valve 114 to the outlet connection 116.
Once the pumps shown by Figs. 1 and 2 are fully primed, the delivery pressure at the outlet will be substantially constant, because the discharge stroke is spring-powered by the uniform tension produced by the expansion of spring 32. The effect on discharge pressure of pump pulsations can be practically eliminated by use of an air dome or the like in the discharge passages 12 or 115.
The volume of fluid delivered depends upon the dis charge pressure head imposed by outlet restrictions upon the diaphragm 24 to resist the expansion of spring 32. Thus, the rate of operation of the pump, and, of course, its power consumption, are controlled by outlet pressures, and its rate of operation will be in inverse ratio to back pressure at the outlet. Accordingly, the frequency will vary widely in the usual fuel supply systems and is not dependent on cranking or running speeds of an engine, as is its mechanically operated counterpart. Such a pump will respond automatically to demand conditions and can be installed in a favorable location away from engine heat, for example between the radiator grill and the radiator of a motor vehicle.
In Fig. 3 is shown diagrammatically an electric circuit applicable to the modifications of the invention illustrated in Figs. 1 and 2. A battery B has One terminal connected to ground, and its other terminal connected directly with field coil 41, andthence to ground, so as to be constantly energized to provide a permanent magnetic field for the movable armature. In actual practice, the battery connection may be controlled by a switch, such as shown in Cofley application Serial Number 262,788, filed December 21, 1951, now abandoned, for Electric Fuel Pump Control. A lead also connects the battery to the flexible point supporting arm 52 to energize the armature 43 when the points 50 and 51 are closed. To this end, a lead 126 connects the points 50 and 51 with the armature coil 43. Coil 43 is grounded by way of lead 127. A condenser 80 is connected in parallel with the circuit breaker points 50 and 51 by a pair of leads 129 and 130.
A manually operated push button type of switch is connected in the circuit in parallel with points 50 and 51. This push button may be located on the pump or on the instrument panel so that in case points 50 and 51 do not make a good electric contact the push button can be used to operate the pump for a few cycles to clean the surface of the points.
This circuit, when closed, provides for constant energization of the field coil 41 and intermittent energize- Electra-dynamic motor design calculation One manner in which some of the advantages of the present invention can be best emphasized is by an illustrative example based on theoretical calculations for a proposed motor of the electrodynamic type as compared with a calculated example for a motor of the non-polar type such as shown by the patent to Dilig, 2,179,925, of November 14, 1939, for both are based upon the same mechanical requirements such as a certain force (P) for the suction stroke, and a certain stroke (1). Any design for the electrodynamic motor based on these mechanical requirements would correspond to iuil load 100% at a given amperage in the armature, deemed practical, having due regard for operating temperature limits. These calculations will consequently take this into account, and the motor design will be one giving the same initial force (P) as the non-polar type, but at a given current (5 amps.) as full load rating for the motor. Unlike a non-polar type, the electrodynamic type of motor is capable of operating even if overloaded. The amount of overload over the full rating will, of course, increase the amount of current in the armature proportionately. The point is, however, that overload will not necessarily stall the eleetrodynamic type of motor as it will a non-polar type, and good design would allow for increases in current above full load rating (P) at a given current. Excessive overload can be readily prevented by use of a thermal circuit brefler.
If we assume that the maximum force required to compress the spring on the suction stroke is 6 pounds, thestroke is /4, the diameter of the core 1.25, the maxi mum coil diameter permitted is 2.50, the coil length 1", the flux required in the gap of 0.1 is 5000 gausses, then the first step would be to determine the number of ampere turns for the field Winding of the electrodynamic type of motor.
To determine NI for a flux density of 5000 gausses (equals 0.5 Weber per square meter) in the gap from the relation The next step is to determine the resistance of field coil in ohms (Q) for 1000 ampere turns. To do this for a given coil having the dimensions within the limits of those given above is a matter of trial and error.
With #20 wire of 10.169/1000, the number of turns per square'inch will be 30.
inch, then the length of wire required for 1000 turns:
To determine the resistance,
206 (R) -.F)'66X 1016-2089 The current (I) will vary with variations in voltage from 4 to 8 volts, normal battery voltage being 6 volts.
d or 6 or 8 NI=450 (2 or 3 or 4) =900 or 1350 or 1800.
In the above field circuit we have established a flux density of at least 5000 gausses across the gap of 0.1". The armature coil must produce at least 6 pounds of force (P). In solving such a problem, it is expedient to calculate first the number of ampere turns or length of Wire for a given armature current. Assuming 5 amps, which appears to be a practical value because of commutation problems, P=6=kBli as stated above where k is (5.65 X10 a conversion factor to mixed units, and l=21r times the mean radius of the gap.
=approx. 2 or 3 or 4 amps.
Assuming No. 20 AWG with diameter of 33.4 mills for enamel insulation, with two layers of 34 turns each, the axial length (x) of the coil =34X33.4 mills =1.17 inches Thickness of the coil =2 33.4=.0668 inch. With a coil of these dimensions, an allowable clearance is provided for coil and former .033 inch approximately. Obviously, the axial length of the coil will give adequate stroke and still remain in a constant field with a pole face width of 1.5" and a stroke of 0.25". 7
It becomes important to know the inductance of the armature coil, since the service life of the points depends upon this value at the time the circuit is interrupted. From a comparison of this value between motors of the two types discussed here, a measure of expected life of similar contacts can be made.
The inductance in henrys of the armature coil in the air gap space can be computed from the equation:
Where (m) is the axial length of the armature coil, (l) is the air gap, n is (47rX10 Where the mean diameter is (1.05") and length of armature coil (1.1"), then:
The area of the coil in cross-section= l"XO.5"==0.5 ij
or thirty turns in depth and fifteen in width, thus L 0.90 ,millihenry ,Non-polar motor design calculations .For substantially the same size of coil to produce the 30 15==450 T is. Where the mean coil diameteris 0.875 same initial force (F) tor a gap of M1" in a non polar 13 type of magnetic motor, calculations give a 'requirednfiux density (B=3220 gausses for a. pull of 6 pounds and a cross-section area of gap as 1 sq. inch.
The solenoid winding could'have 288 turns of No. 18 wire at'24 turns per inch, or a total length of-13 feet with a resistance of 0.83 ohm.
Where the voltage varies from 4 to 8 volts:
4 or 6 or 8 NI=4.8 288=1400 ampere turns NI=7.2 288=2070 ampere turns NI=9'.6 288=2770 ampere turns Thus, the motor should develop 6 pounds pull at 6 volts.
With an open gap, the inductance of the solenoid winding is given by the equation above set forth, which is:
=4..s or 7.2 eras am s.
L =6.5 millihenrys for open gap The ratio of flux density with gap closed to that open is not over 3:1 (approx.,3220:l0,000) because of the saturation effect in the, iron, This means that L with gap closed will be at least of the order of 3 6 .5=l9.5 millihenrys.
To get a comparison between the average counter electromotive forces during that portion of the commutation cycle when the energizing current is interrupted, use can be made of the relationship between inductance and counter-electromotive force from the equation:
which, for comparison purposes, can be modified to obtain the average voltage (E,,) as a measure of commutator life.
AI E -L For electrodynamic type:
B 0.9O l0- amps. 4.5 0
At 4 At For the non-polar type at closed gap position:
E l9.5 l0 7.2 amps. ll0. l0-
At At A! will, of course, be substantially identical for both machines. Therefore, the ratio vwinding generating a magnetic force, a low inductance motor winding generating a magnetic force within but independent of said high inductance motor winding, and
' 1 4 a' commutator means in said low inductance motor winding actuated by said motor to intermittently energize said low inductance motor winding.
2. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature,
means actuated by said motor for intermittently producing a polar magnetic force in said armature from a substantially constant current source, a connection between said armature and said pumping element, and a magnet providing a. field for said armature having oppositely spaced poles internally and externally of said armature for producing a constant flux density about said armature, whereby a substantially uniform force is applied to said pumping element by said armature when said armature is energized by said intermittent means.
3. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electric motor connected thereto for operating said pumping element, having an electric circuit comprising a first energized winding of low inductance, a second energized winding of high inductance, means actuated by said motor for intermittently interrupting the circuit to said low inductance winding so as to end the thrust produced by said motor on said pumping element in one direction, and a capacitor in shunt relation with said low inductance wind ing for blocking the current flow from said winding upon actuation of said means and reversing the thrust produced by said motor.
4. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump comprising an armature having an energized winding, a connection between said armature and said pumping element, a magnet having opposite poles located internally and externally of said armature, producing a field surrounding said winding of constant flux density whereby a substantially uniform force is applied to said pumping element by said armature, and means for de-energizing said motor armature winding and reversing the thrust produced thereby, including a circuit breaker and a condenser.
5. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature having an energized winding, a connection between said armature and said pumping element, a magnet producing a field surrounding said winding of substantially constant flux density, whereby a substantially uniform force is applied to said pumping element, and means for de-energizing said motor armature winding and reversing the thrust produced thereby, including a circuit breaker and a condenser.
6. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature having an energized helical winding of low inductance, means actuated by said motor for intermittently producing a polar magnetic force in said armature from a substantially constant current source, a connection between said pumping element and said armature, and an energized field of higher inductance having an energized winding and oppositely spaced poles internally and externally of said armature forming a gap of constant Width for said helical winding throughout the stroke of said armature, whereby a substantially uniform force is applied to said pumping element by said armature when said armature is energized by said intermittent means.
7. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature having an energized helical winding of low inductance, a connection between said pumping element and said armature, a pair of opposite polarity poles, an energized winding of high inductance on said poles providing a magnetic field surrounding said helical winding, and a circuit breaker actuated by said armature for de-energizing said low inductance winding.
8. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature having an energized helical winding of low inductance, a connection between said pumping element and said armature, a pair of opposite poles concentrically arranged with respect to said helical winding, an energized winding on said poies providing a magnetic field of constant flux density, and a circuit breaker actuated by said motor for de-energizing said low inductance winding.
9. in a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump comprising an armature having an energized helical winding, means actuated by said motor for intermittentl producing a polar magnetic force in said armature from a substantially constant current source, a connection between said armature and said pumping eiernent, a pair of opposite magnetic poles concentricaliy arranged with respect to said helical winding and forming a uniform gap to produce a constant flux density surrounding said helical winding whereby a su stantially uniform force is applied to said pumping element by said armature when said armature is energized by said intermittent means.
10. In a reciprocating type of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for said pump, comprising an armature having an energized helical winding of low inductance, a connection between said armature and said pumping element, a pair of opposite magnetic poles concentrically arranged with respect to said helical winding and forming a uniform gap to produce a constant flux density surrounding said helical winding whereby a substantially uniform force is applied to said pumping element and means for de-energizing said low inductance winding actuated by said motor.
11. In a reciprocating type of fuel pump, the combination of a pump body, a flexible diaphragm pumping element in said body, and an actuator for said element, con prising an electrodynamic motor including an armature having a cylindrical armature winding, a stem mounting said winding on said diaphragm and extending into said body, a field magnet, concentrically spaced poles in said magnet forming a gap of constant flux strength for said armature winding, a guide in said magnet receiving said stem, and a circuit breaker for said armature winding adjacent said guide and actuated by said stem.
12. In a reciprocating type of fuel pump, the combination of a pumping element and an electrodynamic motor for operating said pumping element, comprising an energized winding, means connected to said pumping element and operable upon energization of said winding to move said pumping element, a circuit breaker for said winding including a pair of contacts, and mechanism supporting said contacts and engaged by said means including additional means for imparting a wiping action between said contacts during their operating cycle.
13. In a reciprocating type of fuel pump, the combination of a pumping element and an electrodynamic motor for operating said pumping element, comprising an energized winding, first means connected to said pumping element and operable upon energization of said windmg to move said pumping element, a circuit breaker for said winding including a pair of contact surfaces, a mechanism supporting said contact surfaces including a spring device and additional means actuated by said first means for imparting a Wiping action between said contact surfaces during their operating cycle.
14. In a reciprocating type of fuel pump, the combination of a pumping element and an electrodynamic motor 'for operating said pumping element, comprising an energized winding, means connected to-said pumping element and operable upon energization of said winding to move said pumping element, a circuit breaker for said winding including a pair of contact surfaces, a mechanism supporting said contact surfaces including a spring device actuated by said means and a trigger device retaining contact between said surfaces, thereby imparting a wiping action during the loading of said spring device and preceding the release of said spring device by said trigger device to separate said contact surfaces.
15. ,In a reciprocating type of fuel pump, the combination of a pumping element and an electrodynamic motor for operating said pumping element, comprising an energized winding, means connected to said pumping element and operable upon energization of said winding to move said pumping element, a circuit breaker for said winding including a pair of contact surfaces, a mechanism supporting said contact surfaces including a spring device actuated by said means, a trigger device retaining contact between said surfaces for imparting a wiping action during their opening cycle, and a manual switch in shunt relation with said contacts.
16. In a reciprocatingtype of fuel pump, the combination of a pumping element and a reciprocating electrodynamic motor for providing a substantially uniform force on said pumping element throughout the pump stroke comprising an armature having an energized helical winding of low inductance, a connection between said armature and said pumping element, a pair of opposite magnetic poles concentrically arranged with respect to said helical winding and forming a uniform gap to pro- ,duce a constant flux density surrounding said helical winding whereby a substantially uniform force is applied to said pumping element, and means including a circuit breaker actuated by said motor for de-energizing said low inductance winding whereby arcing in said circuit breaker is minimized.
17. In a reciprocating type of fuel pump, the combination of a pumping element, a reciprocating electrodynamic motor for operating said pumping element in one direction, and a spring compressed by said motor for moving said pumping element in the opposite direction, said motor comprising an armature having an energized winding, a connection between said armature and said pumping element, a magnet having opposite poles located internally and externally of said armature producing a field surrounding said winding of constant flux density whereby a substantially uniform force is applied to said pumping element by said armature during operation of said motor, a circuit breaker for de-energizing said motor, and a condenser connected in shunt relation with said circuit breaker for temporarily reversing the thrust of said motor when said armature is de-energized by said circuit breaker to aid the action of said spring and increase the operating frequency of said motor.
18. In a reciprocating type of fuel pump, the combination of a pumping element and an electric motor of the reciprocating type for operating said pumping element comprising a winding connected to said pumping element, means for energizing said winding to move said pumping element including fixed and movable contacts, a resilient means mounting said movable contact, a mechanical means operated by said motor acting on said resilient means to separate said contacts, and a holding means disposed adjacent said contacts and applying a force thereto tending to resist opening movement whereby the action of said mechanical means on said resilient means causes initial distortion of said resilient means preceding opening of said contacts to produce a wiping action between said contacts during their operating cycle.
19. in a reciprocating type of fuel pump, the combination of a pumping element, a spring for moving said pumping element in one direction, and an electric motor of the reciprocating type for operating said pumping element in the opposite direction comprising an energized winding, means operated by said motor on energization of said winding to move said pumping element, a circuit breaker for de-energizing said winding including fixed and movable contacts, a resilient means mounting said movable contact, means operated by'said motor acting on said resilient means to separate said contacts, and a holding means disposed adjacent said contacts and applying a force thereto tending to resist opening movement whereby the action of said mechanical means on said resilient means causes initial distortion of said resilient means preceding opening of said contact for impartinga wiping action between said contacts during their operating cycle.
20. In a reciprocating type of fuel pump, the combination of a pumping element, a spring for moving said pumping element in one direction, and anelectric motor of the reciprocating type for operating said pumping element in the opposite directio'ncomprising an energized winding in said motor, means operated by said motor on energization of said winding to move said pumping element, a circuit breaker for said winding including fixed 20 2,669,937
and movable contacts, a leaf spring mounting said movable contact adjacent one end thereof and secured to a fixed support adjacent its other end, a means operated by said motor acting on said spring intermediate its length to separate said contacts, and a magnet disposed adjacent said contacts and applying a force to said spring adjacent said contacts tending to resist opening movement of said contacts by said spring whereby the action of said mechanical means on said spring causes initial distortion of said spring preceding opening of said contacts to produce a wiping action between said contacts during their operating cycle.
References Cited in the file of this patent UNITED STATES PATENTS 1,737,387 Redmond Nov. 26, 1929 2,169,827 Whitted Aug. 15, 1939 2,169,862 Whitted Aug. 15, 1939 Presentey Feb. 23, 1954