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Publication numberUS3871178 A
Publication typeGrant
Publication dateMar 18, 1975
Filing dateSep 6, 1973
Priority dateOct 31, 1972
Publication numberUS 3871178 A, US 3871178A, US-A-3871178, US3871178 A, US3871178A
InventorsHiroyoshi Tominaga
Original AssigneeKomatsu Mfg Co Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Variable output pump control circuit using a remote control
US 3871178 A
Abstract
A variable output pump control circuit using a remote control valve for switching two control valves which control the operation of hydraulic actuators and control the switching of the servo motor of a variable output pump by means of pilot pressure from the remote control valve. A control circuit is provided in the pilot circuit of the variable output pump for controlling switching by means of the pilot pressure from the remote control valve. Thus, insufficient hydraulic pressure in the pilot circuit, which occurs when the flow rate in the remote control valve is small, is eliminated.
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Description  (OCR text may contain errors)

United States Patent 1 [111 3,871,178 Tominaga Mar. 18, 1975 VARIABLE OUTPUT PUMP CONTROL 3,486,334 12/1969 Miller 60/445 x CIRCUIT USING A REMOTE CONTROL 3,672,I6l 6/l972 Krusche et al 60/445 X Hiroyoshi Tominaga, Osaka, Japan Kabushiki Kaisha Komatsu Seisakusho, Tokyo, Japan Filed: Sept. 6, 1973 Appl. N6; 394,664

Inventor:

Assignee:

Foreign Application Priority Data Oct. SI, 1972 Japan 47-108463 References Cited UNITED STATES PATENTS 6/1960 Carlson et a] 60/433 X Primary Examiner-Edgar W. Geoghegan Attorney, Agent, or FirmArmstrong, Nikaido & Wegner [57] ABSTRACT A variable output pump control circuit using a remote control valve for switching two control valves which control the operation of hydraulic actuators and control the switching of the servo motor of a variable output pump by means of pilot pressure from the remote control valve. A control circuit is provided in the pilot circuit of the variable output pump for controlling switching by means of the pilot pressure from the remote control valve. Thus, insufficient hydraulic pressure in the pilot circuit, which occurs when the flow rate in the remote control valve is small, is eliminated.

2 Claims, 2 Drawing Figures PATEHTEU 1 8 I975 SHEET 1 [If 2 VARIABLE OUTPUT PUMP CONTROL CIRCUIT USING A REMOTE CONTROL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a hydraulic circuit of a hydraulic power shovel, and more particularly to a variable output pump control circuit using a remote control valve for controlling the control valve and the variable output pump of the hydraulic power shovel.

2. Prior Art Conventional variable output pump control circuits for the hydraulic circuit of a hydraulic power shovel have a pilot pump, two control valves for controlling the operation of two actuators for the power shovel, a variable output pump with a servo motor, and a remote control valve having four control valves connected at the secondary ports thereof to the pilot ports of the two control valves. The two control valves each have two opposite springs for urging spools at both sides thereof. This control circuit also has a throttle valve in the drain circuit of the pilot circuit of the variable output pump.

In a variable output pump control circuit as described above, when the remote control valve receives hydraulic oil from the pilot pump, it blocks the pilot pressure with a handle positioned in neutral. If one of the control valves of the remote control valve is operated, the secondary output pressure thereof is linearly varied from zero to a predetermined pressure responsive to the stroke of the spool thereof or to the inclining angle of the manually operated lever. When the other three control valves of the remote control valve are operated, a similar operation is performed. Then, when the hydraulic pressure is changed from zero to a predetermined pressure by the remote control valve the pressure is applied to the spools of the two control valves, the spools of the control valves are varied linearly in such a manner that the hydraulic pressures applied thereto and the tensions of the springs are balanced. However, when the servo motor of the variable output pump is also controlled by the pilot pressure from the remote control valve, the discharge amount of the pump is varied linearly with respect to the stroke of the spool of the remote control valve. Further, after the hydraulic pressure from the remote control valve operates the servo motor of the variable output pump, the throttle valve provided in the drain circuit of the pilot circuit of the variable output pump neutralizes the remote control valve and returns the servo motor to its initial state by allowing the hydraulic fluid in the pilot circuit to escape while the passage to the remote control valve is blocked by a check valve.

However, the conventional variable output pump control circuit which has the throttle valve in the drain circuit of the pilot circuit has the following disadvantages: (1) When the hydraulic flow rate from the remote control valve is small such as when the engine speed is low, the leaking rate of the hydraulic oil from the throttle valve becomes large thus the hydraulic pressure in the pilot circuit becomes insufficient. (2) If the throttle valve is excessively throttled in order to avoid the above situation, the returning of the servo motor of the variable output pump is slow with the result that the returning of the inclined plate angle of the pump to neutral position becomes slow, thus the responsiveness of the system is slow.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a variable output pump control circuit using'a remote control valve which may normally operate the servo motor thereof even if the engine speed is low.

It is another object of the present invention to provide a variable output pump control circuit using a remote control valve which may quickly return the servo motor to its initial state, thus greatly improving the re sponsiveness thereof.

It is a further object of the present invention to provide a variable output pump control circuit using a remote control valve which may freely adjust the returning speed of the servo motor.

In order to perform the aforementioned and other objects of the present invention, there is provided a variable output pump control circuit using a remote control valve for switching two control valves which control the operation of hydraulic actuators and also which switch the servo motor of the variable output pump by means of pilot pressure from the remote control valve. A control circuit is provided in the pilot circuit of the variable output pump for switching, by means of the pilot pressure from the remote control valve, so that the total flow from the pilot circuit is to the servo motor when controlling the servo motor of the variable output pump and all the hydraulic oil is drained from the servo motor when returning the servo motor to its initial state. This eliminates the disadvantages of the conventional variable output pump control circuit.

DETAILED DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the present invention will become more fully apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a hydraulic control circuit of a conventional variable output pump control circuit using a remote control valve; and

FIG. 2 is a hydraulic control circuit of a variable output pump control circuit according to the present invention.

PREFERRED EMBODIMENTS For better understanding of the present invention, the conventional variable output pump control circuit willnow be described with reference to FIG. 1, which shows a hydraulic circuit of a conventional variable output pump control circuit.

The conventional variable output pump control circuit has, as in FIG. 1, a pilot pump 2, two control valves 7 and 8 for controlling the operation of two actuators for a power shovel. The circuit also includes a variable output pump 10 with a servo motor 11, and a remote control valve 1 having four control valves 10, lb and 1c, 1d connected at the secondary ports thereof to the pilot ports of the two control valves 7 and 8, respectively. The two control valves 7 and 8 each have two opposite springs 9 for urging the spool thereof at both sides. The control circuit also has a throttle valve 13 in the drain circuit of the pilot circuit 12 of the variable output pump 10.

In this variable output pump control circuit, when the remote control valve 1 receives hydraulic oil from the pilot pump 2, it blocks the pilot pressure with a handle (not shown) manually positioned in neutral. If one of the control valves 1a, 1b, 1c and 1d of the remote control valve 1 is operated, the secondary output pressure thereof is varied linearly from zero to a predetermined pressure P responsive to the stroke of the spool thereof or to the inclining angle of the manually operated lever (not shown). If the other three control valves of the remote control valve 1 are operated, a similar operation is performed. The hydraulic pressure from the remote control valve 1 is applied to the spools of the two control valves 7 and'8, and the spools of the control valves 7 and 8 are varied linearly in such a manner that the hydraulic pressures applied thereto and the tensions of the springs 9 are balanced. The servo motor 11 of the variable output pump 10 is also controlled by the pilot pressure from the remote control valve 1, the discharge amount of the pump 10 is also varied linearly with respect to the stroke of the spool of the remote control valve 1. Further, after the hydraulic pressure from the remote control valve 1 operates the servo motor 11 of the variable output pump 10, the throttle valve 13, provided in the drain circuit of the pilot circuit 12 of the variable output pump 10, neutralizes the remote control valve 1 to return the servo motor 11 to its initial state by permitting the escape of the hydraulic fluid in the pilot circuit 12 when the passage to the remote control valve 1 is blocked by a check valve (not shown).

Referring now to FIG. 2, which shows a hydraulic circuit of one embodiment of a variable output pump control circuit using a remote control valve constructed according to the present invention, wherein the like numerals correspond to those shown in FIG. 1, the variable output pump control circuit of this invention comprises a control circuit 15 provided in the pilot circuit 12 for supplying the pilot pressure to the servo motor 11 of the variable output pump 10 from the remote control valve 1. The control circuit 15 includes a valve 16 having a communication position or section 16a for connecting the pilot circuit 12 with the servo motor 11 and a drain position or section 16b for blocking the pilot circuit 12 and also for connecting the return fluid or oil of the servo motor 11 to the drain circuit. The circuit also includes a spring 18 coupled to a control valve 16 disposed at one end of the spool thereof to urge the spool for connecting the section 16b with the drain circuit l7, and a control passage 19 for automatically switching the state of the control valve. The control passage 19 connects the pilot circuit 12 between the control valve 16 and the remote control valve 1 to the drain circuit 17. A pilot passage 20 is provided in the control passage 19. The passage 20 is connected to side end surface of the section 16a of the control valve 16, and a throttle valve 21 is provided at the drain circuit 17 side of the pilot passage 20.

In FIG. 2, numerals 22 and 23 represent hydraulic actuators.

In the variable output pump control circuit thus constructed, when the remote control valve 1 is operated so as to supply hydraulic fluid or oil to the pilot circuit 12, the hydraulic fluid flows to the control passage 19, and is throttled by the throttle valve 21 thus increasing the pilot pressure in the pilot passage 20. Thus, the control valve 16 normally urged by the spring 18 to the position shown in FlG. 2 is switched so that the section l6a is connected to the pilot circuit 12 with the result that all the fluid or oil from the remote control valve 1 flows into the servo motor 11 of the variable output pump 10 to operate the variable output pump 10.

When the remote control valve 1 is operated to shut off the supply of hydraulic fluid to the pilot circuit 12, the pilot pressure in the control passage 19 is released so that the control valve 16 is returned by the spring 18 with the result that the servo motor 11 is drained via section 16b through the drain circuit 17.

It should be understood from the foregoing description that the variable output pump control circuit uses a remote control valve 1 for switching two control valves 7 and 8 for controlling the operation of hydraulic actuators 22 and 23 and also for switching the servo motor 11 of a variable output pump 10. The circuit comprises a control circuit 15 in the pilot circuit 12 of the variable output pump 10 for connecting the remote control valve 1 with the servo motor 11 of the variable output pump 10. The control circuit has a control valve 16 having a section 16a for connecting the pilot circuit 12 to the the servo motor 11 and a section 16b for blocking the pilot circuit 12 and also for connecting the return fluid of the servo motor 11 with the drain circuit. A. spring 18 is so disposed at one end of the spool of valve 16 to urge the spool for connecting the section 16b with the drain circuit 17. A control passage 19 is connected to the pilot circuit 12 and has a throttle valve 21 provided at the drain circuit side of the pilot passage for throttling pressure at the other end of the control valve 16. The pilot pressure which operates the servo motor 11 of the variable output pump 10 is derived from all the hydraulic fluid supplied from the remote control valve 1. Thus even if the engine is at low speed, the servo motor 11 will operate normally. Particularly, even if the fluid flow rate is very low due to throttling of the throttle valve 21, no trouble is caused.

It should also be understood that when the servo motor 11 is returned to the neutral position, the hydraulic fluid of the servo motor 11 is drained to the drain circuit 17 without resistance with the result that the returning of the servo motor 11 is rapid so as to greatly improve its responsiveness.

It should also be understood that if the throttle valve 21 is so provided as to be adjustable, the returning speed of the servo motor 11 may be freely adjusted.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

l. A variable output pump control circuit using a remote control valve for switching two control valves which control the operation of hydraulic actuators and also for switching a servo motor of a variable output pump, comprising control circuit means in a pilot circuit of said variable output pump for connecting said remote control valve with said servo motor, said control circuit means including: switching a control valve, having a first section for connecting the pilot circuit with said servo motor, a second section for blocking the pilot circuit and for connecting said servo motor with a drain circuit, and a spring means disposed at one end other end of the switching control valve.

2. A variable output pump control circuit according to clairn 1, wherein said throttle valve is adjustable.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2941365 *Jul 23, 1957Jun 21, 1960Sundstrand CorpHydraulic transmission
US3486334 *May 16, 1968Dec 30, 1969Cessna Aircraft CoHydraulic power transmission control
US3672161 *Jan 13, 1971Jun 27, 1972Linde AgControl system for a stepless hydrostatic drive
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4208874 *Aug 28, 1978Jun 24, 1980Caterpillar Tractor Co.Apparatus for producing different flow rates of a fluid
US4420937 *Jul 24, 1981Dec 20, 1983Kabushiki Kaisha Komatsu SeisakushoHydraulic circuit for a variable displacement pump
US5052179 *Mar 16, 1990Oct 1, 1991Kabushiki Kaisha Kobe Seiko ShoPump discharge flow rate controlled by pilot pressure acting on vehicle drive valves
US5575148 *Nov 30, 1994Nov 19, 1996Hitachi Construction Machinery Co., Ltd.Hydraulic pump control system
US5907951 *Mar 5, 1998Jun 1, 1999Hitachi Construction Machinery Co., Ltd.Hydraulic control system for construction machine
US5992147 *Apr 24, 1998Nov 30, 1999Kabushiki Kaisha Kobe Seiko ShoHydraulic control system in construction machine
US6601386 *Feb 4, 2000Aug 5, 2003Komatsu Ltd.Lever-operated actuator drive unit and operating lever unit
CN100526658CApr 19, 2007Aug 12, 2009沈阳市中之杰机电设备制造有限公司Burning machine inlet guide blade adjusting device
Classifications
U.S. Classification60/443, 60/484, 60/445
International ClassificationF15B11/00, F15B11/16, E02F9/22, F16K11/00
Cooperative ClassificationF15B2211/6355, F15B2211/20553, F15B2211/329, F15B2211/255, F15B2211/71, F15B11/16, F15B2211/3116
European ClassificationF15B11/16