US3583285A

US3583285A - Pressure responsive direction control valve

Info

Publication number: US3583285A
Application number: US842459A
Authority: US
Inventors: Bruce Leland Johnson
Original assignee: Deere and Co
Current assignee: Deere and Co
Priority date: 1969-07-17
Filing date: 1969-07-17
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

A hydraulic control system for a remote, double-acting piston motor in which a normally hydraulically balanced, springcentered, spool-type direction control valve is shifted from the centered position in which the opposite work ports of the motor are simultaneously pressurized to first and second positions in which fluid under pressure is selectively admitted to one or the other ends of the motor while the opposite end is exhausted. The opposite ends of the direction control valve are connected to the inlet pressures of a respective one of a pair of variable flow resistance valves and the control valve is shifted from the centered position to a selected one of the other positions by changing the resistance, hence the inlet pressure, of one of the flow valves and the control valve is returned to the centered position as a result of a feedback from the motor which shifts the other flow resistance valve until the forces on the opposite ends of the control valve are again equal.

Description

United States Patent 3,415,163 12/1968 lnabaetal.

ABSTRACT: A hydraulic control system for a remote, double-acting piston motor in which a normally hydraulically balanced, spring-centered, spool-type direction control valve is shifted from the centered position in which the opposite work ports of the motor are simultaneously pressurized to first and second positions in which fluid under pressure is selectively admitted to one or the other ends of the motor while the opposite end is exhausted. T opposite ends of the direction control valve are connected to the inlet pressures of a respective one of a pair of variable flow resistance valves and the control valve is shifted from the centered position to a selected one of the other positions by changing the resistance, hence the inlet pressure, of one of the flow valves and the control valve is returned to, the centered position as a result of a feedback from the motor which shifts the other flow resistance valve until the forces on the opposite ends of the control valve are again equal.

I PRESSURE RESPONSIVE DIRECTION CONTROL VALVE BACKGROUND OF THE INVENTION This invention relates to a hydraulic system for controlling a remote, double-acting motor, such as used in steering and manipulation of implement parts, and more specifically relates to a system wherein a normally hydraulically balanced, springcentercd, spool-type direction control valve is provided for simultaneously pressurizing both ports of the motor and for selectively admitting fluid to one or the other of the ports while exhausting the opposite port and wherein an input force operates on a variable flow resistance valve in the system for changing the pressure on one end of the control valve to shift the control valve, and a feedback from the motor operates on another variable flow resistance valve in the system for changing the pressure on the other end of the control valve so as to again hydraulically balance the control valve.

Hydraulic systems similar to that of the invention are known, for example in U.S. Pat. No. 2,974,639 to OConner et al. issued 14 Mar. I961. Such systems are, however, somewhat complicated and, therefore, lack hydraulic stability. Also in the known systems, no provision is made to compensate for variances between manufactured and design dimensions.

SUMMARY OF THE INVENTION According to the present invention there is provided a hydraulic system for controlling a remote, reversible hydraulic motor which includes a spring-centered spool-type direction control valve wherein the inlet to a first variable flow resistance valve is connected to a fluid chamber at one end of the control valve and a second variable flow resistance valve is connected in series with the first flow resistance valve and has its inlet connected to a fluid chamber at the other end of the control valve.

An object is to adapt one of the variable flow resistance valves for connection to an input signal while interconnecting the output of the hydraulic motor with the other variable flow resistance valve by means of a feedback signal.

An object of the invention is to provide a system in which the flow resistance valves may be placed remotely from each other. A

Another object is to provide normally closed adjustable flow restriction valves for bypassing fluid from the inlets of the flow resistance valves for compensating for differences in manufactured dimensions from design dimensions.

Still a further object is to provide a simplified, inexpensive 4 control for a two-way hydraulic cylinder which is hydraulically stable and reliable.

These and other objects will be apparent from the following detailed description and accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE shows a hydraulic system embodying the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT The system includes a valve body which defines a pair of

similar bores

12 and 14 respectively having closed ends 16 and I8, and a bore 20 having first and second

cylindrical portions

21 and 22 of different diameters and opposite closed ends 23 and 24. The valve body 10 also defines a bore 26 which has opposite closed

ends

28 and 30.

The

bores

12 and 14 are intersected adjacent their respective closed ends by inlet passages 32 and 34 respectively. The bore 12 is connected to an outlet passage 36 spaced axially from the inlet passage 32 and leading to a sump (not shown). The inlet 32 of the bore 12 serves as an outlet for the bore 14 and is spaced axially from the inlet passage 34. The inlet passage 34 intersects the portion 21 of the bore 20 adjacent the closed end 23, and diametrically opposite from the intersection of the passage 32 with the bore 14 is a passage 37 which joins a passage 38 which interconnects the inlet passage 34 and the right end of the portion 22 of the bore 20.

Also intersecting the portion 21 of the bore 20 are axially spaced sump-connected passages 40 and 42, a passage 44 midway between the passages 40 and 42 connected to a source of fluid under pressure (not shown) and work passages 46 and 47 between the passages 40 and 44 and 42 and 44 and respectively leading to the cylinder bore 26 adjacent its respective closed

ends

28 and 30. A passage 48 interconnects the passage 44 and the inlet passage 32 and contains a manually preset restriction 49 which may be an adjustable needle valve.

The bores 12 and I4 respectively carry variable

flow resistance valves

50 and 52. The

flow resistance valves

50 and 52 respectively have reduced

piston portions

54 and 56, which bridge the respective outlet passages 36 and 32 of the

bores

12 and 14, and

piston rods

58 and 60 extending respectively through the

bore ends

16 and 18. O-

ring seals

62 and 64 respectively encircle the other ends of the

pistons

54 and 56.

A pressure responsive control valve 66 is axially movable in the bore 20 and includes leftand right-

hand pistons

68 and 70 respectively slidably fitting

bore portions

21 and 22. The purpose of the enlarged bore portion 22 and piston 70 will be explained below. The control valve 66 further includes a pair of axially spaced

lands

72 and 74 respectively at the leftand right-hand sides of the passage 44. Springs 76 and 78 are respectively positioned between the opposite ends 23 and 24 of the bore 20 and the oppositely directed faces of the

pistons

68 and 70 and normally center the control valve 66 at the position illustrated wherein the

lands

72 and 74 respectively block the passages 42 and 44. A screw element 79 combines with the spring 78 for adjusting the centered position of the valve 26.

The cylinder bore 26 carries a piston 80 having oppositely extending

piston rods

82 and 84 which respectively extend through the

bore ends

28 and 30. A feedback 86, here shown as mechanical, moves the flow resistance valve 52 in response to movement of the piston 80 and includes a lever 88 fulcrumed at 90 intermediate its ends and having lost

motion connections

92 and 94 at opposite ends connected respectively to the

piston rods

60 and 82. While the inputand

feedbackconnected valves

50 and 52 respectively are shown in a common valve block, it is significant that they may be mounted remotely from each other.

In order to compensate for any difference in the dimensions of the manufactured device from the design dimensions, which would cause undesired flow to the

flow resistance valves

50 and 52, a bypass 96 to the sump is provided in the inlet passage 32 and contains a manually adjustable restriction 98 and a similarly manually adjustable restriction 100 is located in the passage 38 adjacent to the inlet passage 34 for bypassing fluid from the passage 34 to the passage 38.

The operation of the system is described here as applied to power steering. In such application, the piston rod 58 of the flow resistance valve 50 would be connected to receive steering wheel movement for moving the flow resistance valve in the bore 12. The restriction 49 is adjusted to insure the provision of enough fluid to operate the hydraulic motor and to adequately supply flow to the

flow resistance valves

52 and 54. Although the preferred embodiment shows connections to a single source of fluid pressure, it should be understood that separate sources may be used for the flow resistance valves and hydraulic motor and the fluid for valve operation need not be hydraulic fluid.

Assuming that the steering gear of the vehicle is positioned for straight ahead travel, the hydraulic system will be in the equilibrium condition illustrated wherein the

flow restriction valves

50 and 52 occupy positions with respect to the respective outlet passages 36 and 32 which establish a preselected ratio of pressure drops corresponding to a preselected ratio of the distance the piston portion 54 extends upstream from the outlet 36 as compared to the distance the piston portion 56 extends upstream from the outlet 32, and the control fluid pressures existing in the passages 34 and 38 respectively wiil. in conjunction with the pressure existing in the sump-connected passages 40 and 42, exert equal and opposite forces on the smaller diameter piston 68 and the larger diameter piston 7Q.

The pressure-responsive control valve 66 is thus hydraulically balanced and is centered by the springs 76 and 78. In this position the

lands

72 and 74 block the respective passages 46 and 47.

If it is desired to steer the vehicle to one side or the other, the steering wheel is merely turned so as to shift the flow resistance valve 50 either to the left or right from the position illustratcd. Assuming that the valve 50 is shifted to the right, the left end of the piston 54 will move closer to the outlet passage 36, and the resistance to fluid flow from the passage 32 to the sump passage 36 will be decreased. With a decrease in resistance to flow, the pressure of the fluid in the passage 32 will correspondingly decrease and this decrease in fluid pressure will occur in the passage 38 and result in a lesser force being applied to the larger piston 70 of the control valve 66. Since the forces on the opposite end of the control valve are no longer equal, the control valve will shift to the right and connect the passages 46 and 47 respectively to the sump passage 40 and to the pressure passage 44. Since the right end of the hydraulic motor cylinder 26 is now pressurized, the piston 80 will shift to the left to turn the wheel being steered and simultaneously cause the feedback lever 88 to pivot clockwise and shift the restriction valve 52 to the right until the pressure in the inlet passage 34 decreases enough to again balance the force exerted by fluid pressure on the opposite ends of the control valve 66, allowing the compression springs to again center the control valve whereby the hydraulic motor will be held in its shifted position. The design of the system is such that the position that the left end of the piston 56 of the flow resistance valve 52 now occupies with respect to the outlet 32 as compared to the position occupied by the piston 54 of the flow resistance valve 50 with respect to the outlet passage 36 will be the ratio preselected. Also, the preselected ratio of pressure drops will again be established.

An operation similar to that described above when shifting the flow resistance valve 50 to the right will occur if the flow resistance valve is shifted to the left from the position illustrated, but the directions of movement will of course be reversed. That is to say, pressure will increase in the passage 38 and the control valve 66 will shift to the right. In this position of the control valve, fluid under pressure is connected to the left end of the cylinder 26 and the right end is connected to sump; thus the piston 80 will shift to the right and pivot the lever 88 counterclockwise to shift the flow resistance valve 52 to the left until fluid forces on the opposite ends of the control valve 66 are again equalized and the control valve is moved by the compression springs to the centered position.

In the event that the manufactured dimensions of the various bores and passages differ from the designed values for a preselected flow, the flow into the bores and passages, and, hence the pressures, may be adjusted by opening the normally closed restriction valves 98 and 100 to bypass such fluid as is necessary to achieve pressures at the opposite ends of the control valve 66 to apply equal forces to its opposite ends for a preselected position of the

flow resistance valves

50 and 52.

it should be understood that the hydraulic system may be used for applications other than power steering, for example, for adjusting and holding an agricultural implement at a selected working position. In such an application, the piston rod 58 of the flow resistance valve 50 would be attached to a means which would follow the contour of the ground s surface while the piston rod 78 of the hydraulic actuator would extend between the implement and the support frame to hold the implement a preselected distance relative to the surface of the ground and would be automatically actuated to raise and lower the implement to compensate for variations in ground contour.

lclaim:

l. A hydraulic system comprising: a control conduit means including variable flow resistance means for establishing control pressures at first and second series connected locations, a valve bore means, conduit means for connecting a source of fluid under pressure to said control conduit means upstream from said first location and to said valve bore means, return fluid passage means intersecting said valve bore means, a reversible hydraulic motor having a pair of work passages connected to said valve bore means, a control valve means axially shiftable in said valve bore means between a neutral position wherein fluid is blocked to the work passages of the hydraulic motor and active positions wherein one or the other of the work passages is connected to fluid pressure while the opposite work passage is connected to the return passage means, bias means normally holding said control valve means in said neutral position, said control valve means including means for sensing the control pressures at said first and second locations and for directing forces represented by the pressures in opposite axial directions, means for adjusting said variable flow resistance means to a preselected position for causing a ratio of control pressures which will result in equal and opposite forces being applied to said control valve whereby said bias means will hold said control valve in said neutral position, said flow resistance means being adapted for connection to an input signal for disturbing the preselected ratio of control pressures so that the control valve means will shift to one of said active positions to cause actuation of said hydraulic motor, and feedback means interconnecting the output of said motor with said flow resistance means for adjusting the latter for reestablishing the preselected control pressure ratio whereby the bias means will again return the control valve means to its neutral position.

2. The invention defined in claim 1 wherein the variable flow resistance means comprises first and second valve bores respectively at said first and second series connected locations, each of said valve bores having an inlet and an outlet, the series connection between the locations being between the outlet of the first bore and the inlet of the second bore, first and second pistons being of lesser diameters than said first and second bores, respectively, and being positioned for axial movement in at least the portions of the bores between the respective inlets and outlets for causing a variable pressure drop between the respective inlets and outlets, and one of said pistons being adapted for connection to said input signal and the other of said pistons being connected to said feedback means.

3. The invention defined in claim 1, said control conduit means further including adjustable means for bypassing selected amounts of fluid around said first and second locations for aiding in establishing said preselected ratio of pressure drops.

4. The invention defined in claim 2, said control conduit means further including adjustable means for bypassing selected amounts of fluid around said first and second pistons for aiding in establishing said preselected ratio of pressure drops.

5. The invention defined in claim 1 wherein the means for sensing the pressure drops includes piston means.

6. The invention defined in claim 5 wherein the valve bore means includes first and second portions, the first portion being of a smaller diameter than the second, said piston means comprising first and second pistons positioned respectively in and being of diameter sufficient to span said first and second bore portions, said control conduit means connecting the inlet of said first bore to one side of the smaller piston for exerting a force in one axial direction and connecting the inlet of said second bore to one side of the larger piston for exerting a force in the other axial direction.

7. A hydraulic system comprising: a valve bore, supply and return conduit means intersecting said valve bore, a reversible hydraulic motor having a pair of work passages, a pressure responsive control valve means positioned in said valve bore for axial shifting movement from a normally maintained neutral position wherein said work passages of the motor are blocked to either of two active positions wherein said supply conduit means is connected with one or the other of said work passages of said motor while simultaneously interconnecting the opposite work passage with said return conduit means,

bias means tending to maintain said control valve means in said neutral position, control conduit means being adapted for connection to a source of fluid under pressure and including first and second series connected flow resistance valve means, each having an inlet connected to said control valve means so as to normally apply equal and opposite acting forces on the control valve whereby said bias means maintains said control valve means in said first position, one of said flow resistance valve means being adapted for connection to and being responsive to an input signal for selectively causing changes in pressure at its inlet for causing an unbalance of said oppositely acting forces on said control valve thereby causing the control valve to shift axially to one of said active positions for operating said hydraulic motor and a feedback means interconnecting the output of said hydraulic motor and the other of said flow resistance valve means for causing adjustment of said other flow resistance valve means for creating a pressure at its inlet for again producing an equal and opposite force on said control valve means whereby the bias means will again restore said control valve means to said neutral position.

8. The invention defined in claim 7 wherein said flow resistance valve means includes first and second bores each being intersected by an inlet and an outlet port, conduit means interconnecting the outlet port of said first bore with the inlet port of said second bore, said control valve means including pistons at its opposite ends, said control conduit means further including first and second conduits respectively interconnecting the inlet ports of said first and second bores with one of the opposed faces of said pistons, said pair of flow resistance valve means each being positioned in a respective one of said bores and including an axially shiftable piston portion of lesser diameter than the bore bridging the outlet port and having one end positioned between the inlet and outlet ports and a fluidtight seal annularly disposed about the other end and means for connecting the piston portion of one of said flow resistance valves to said input signal means and said feedback means being connected to the piston portion of the other of said flow resistance valves.

9. The invention defined in claim 8 and further including a normally closed adjustable restrictor valve interconnecting said first and second conduits, and said conduit means connecting the outlet port of said first bore with the inlet port of said second bore also including an adjustablenormally closed restrictor valve joining the conduit means with the sump, whereby said restrictor valves may be opened to bypass fluid for adjusting the pressure in the first and second conduits.

Claims

1. A hydraulic system comprising: a control conduit means including variable flow resistance means for establishing control pressures at first and second series connected locations, a valve bore means, conduit means for connecting a source of fluid under pressure to said control conduit means upstream from said first location and to said valve bore means, return fluid passage means intersecting said valve bore means, a reversible hydraulic motor having a pair of work passages connected to said valve bore means, a control valve means axially shiftable in said valve bore means between a neutral position wherein fluid is blocked to the work passages of the hydraulic motor and active positions wherein one or the other of the work passages is connected to fluid pressure while the opposite work passage is connected to the return passage means, bias means normally holding said control valve means in said neutral position, said control valve means including means for sensing the control pressures at said first and second locations and for directing forces represented by the pressures in opposite axial directions, means for adjusting said variable flow resistance means to a preselected position for causing a ratio of control pressures which will result in equal and opposite forces being applied to said control valve whereby said bias means will hold said control valve in said neutral position, said flow resistance means being adapted for connection to an input signal for disturbing the preselected ratio of control pressures so that the control valve means will shift to one of said active positions to cause actuation of said hydraulic motor, and feedback means interconnecting the output of said motor with said flow resistance means for adjusting the latter for reestablishing the preselected control pressure ratio whereby the bias means will again return the control valve means to its neutral position.

7. A hydraulic system comprising: a valve bore, supply and return conduit means intersecting said valve bore, a reversible hydraulic motor having a pair of work passages, a pressure responsive control valve means positioned in said valve bore for axial shifting movement from a normally maintained neutral position wherein said work passages of the motor are blocked to either of two active positions wherein said supply conduit means is connected with one or the other of said work passages of said motor while simultaneously interconnecting the opposite work passage with said return conduit means, bias means tending to maintain said control valve means in said neutral position, control conduit means being adapted for connection to a source of fluid under pressure and including first and second series connected flow resistance valve means, each having an inlet connected to said control valve means so as to normally apply equal and opposite acting forces on the control valve whereby said bias means maintains said control valve means in said first position, one of said flow resistance valve means being adapted for connection to and being responsive to an input signal for selectively causing changes in pressure at its inlet for causing an unbalance of said oppositely acting forces on said control valve thereby causing the control valve to shift axially to one of said active positions for operating said hydraulic motor and a feedback means interconnecting the output of said hydraulic motor and the other of said flow resistance valve means for causing adjustment of said other flow resistance valve means for creating a pressure at its inlet for again producing an equal and opposite force on said control valve means whereby the bias means will again restore said control valve means to said neutral position.

9. The invention defined in claim 8 and further including a normally closed adjustable restrictor valve interconnecting said first and second conduits, and said conduit means connecting the outlet port of said first bore with the inlet port of said second bore also including an adjustable normally closed restrictor valve joining the conduit means with the sump, whereby said restrictor valves may be opened to bypass fluid for adjusting the pressure in the first and second conduits.