JPS58102809A - Hydraulic valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Known hydraulic actuation load reduction! ! What about the equipment? It can only work when the pressure of the lk pressure device is available.

This means that the load is reduced only when the hydraulic pump supplies fluid under pressure to the device. For example, l
The hydraulic pumps that operate the accessories associated with commercial tractors are driven from the engine power take-off and therefore operate only when the engine is running. If the operator forgets to reduce the load at all before shutting off the engine, and if the control handle of the remote valve that controls the load increase/decrease mechanism is inhibited in the decrease position, the operator may be in danger when operating the machine. A situation may occur. The control handle is placed in the decompression position even though the engine is stopped, resulting in a sudden drop in load.

It is an object of the invention to provide a load shedding device which allows the load to be reduced even when the engine is not running, thus avoiding the need to restart the machine to do so.

Another problem with known devices is the need to minimize leakage in hydraulic valves, particularly spool type hydraulic valves.

This is done by maintaining the gap between the spool and its hole close to manufacturing tolerances. The use of load restraint allows for larger clearances between the spool and the bore, and correspondingly larger tolerances during manufacturing can be used.

It is an object of the present invention to further reduce leakage by utilizing a bin actuated pole check and controlling the load suppression with a pilot valve.

The present invention relates to hydraulic valves for controlling the loading or changing of hydraulic fluid from a source of fluid under pressure, and the flow to and from a hydraulic motor in a hydraulic system.

The example is mechanically actuated and the second example is electronically controlled. Most of the parts are common to both valves. The primary application for these valves is in agricultural tractors.

Hydraulic valves include a valve body having an axially movable valve body for directing fluid through a selected one of a number of passageways extending through the valve body from a source of hydraulic power to one or more connections to a hydraulic motor. Contains the main spool means. The number of fluid connections depends on whether the motor has a fast-acting or dual-acting cylinder assembly. act to reduce the leakage of fluid through it when the leakage is not reduced.
Undesirable movement of the load from the holding position may occur.

Other objects, advantages, and features of the invention will become more apparent as the description proceeds with reference to the accompanying drawings.

The hydraulic valves described herein are utilized to control hydraulic fluid (which may be at high pressure) to and from a hydraulic motor coupled to the valve. Two embodiments of the valve are shown. 1st
An embodiment is mechanically actuated and a second embodiment is electrically controlled. Most of the parts are common to both valves. The primary application for these valves is in agricultural tractors.

FIG. 1 shows mechanically actuated valve 10 with main spool 11 in a neutral position. The inlet of the valve 10 and the pilot signal port 13 are connected to the outlet 14 and the signal port 15 of the discharge valve 16 when the hydraulic pressure supply is from the fixed displacement pump 17, and to the output of the regulated pressure flow when it is from the variable displacement pump 21. Connected to exit 1B and signal exit 19. It is possible to connect several valves similar to valve 10 to the outlet 14 or 18 and the signal port 15 or 17 of two hydraulic pressure sources at the same time. -For example,
Valve 22 is shown connected to ports 14 and 15. The valve outlets 23 and 24 are shown connected to any other hydraulic motor or two-port actuator.

It is also possible to connect the actuator to only one port to the valve, as shown in FIG. 1a, where a single actuating cylinder 2B is connected to port 23. The heavy duty cylinder can be deflated when connected to the outlet 23 or 24. However, in this design it is advantageous when a single working cylinder is connected to 023. This will be explained later.

The chambers 27 and 28 of the valve 10 are internally connected to each other and via a return to the tank of the hydraulic system.

In FIG. 1, outlets 23 and 24 are formed by quick-disconnect couplers 29 and 31 housed in the same body, such as valve 10. Couplers 2B and 31 act as true passages between port 23 and passage 32 and between port 24 and passage 33, respectively, if they are connected to the connecting hose from the hydraulic pressure -9.

When valve spool 11 is in the neutral position, load suppression valves 34 and 35 are seated and the load (in this case cylinder 25
(weight on top) from moving. The oil in passage 32 is also connected to chamber 38 through orifice 36 and passage 37. Oil in the chamber 38 is suppressed by a ball 39 that seals the orifice 41. In the neutral position, the sleeve 42 allows the pilot actuation pin 43 to
The absence of force on B prevents oil in chamber 38 from entering orifice 41 and thence to chamber 28. When sleeve 42 is in the neutral position, bottle 47 exerts a force on ball 4B and prevents oil in chamber 4B from entering orifice 49 and thence to chamber 28.

The sleeve 42 is attached to the spool 1 by the shim and the snap 1 ring.
1, the relative movement of the bins 43 and 47 with respect to the opening and closing of the pressure chamber and the tank closure is performed in the correct order. It is also possible for the sleeve to be structurally part of the spool itself, in which case a larger neutral zone can be accommodated, or other dimensions related to opening and closing of the mouth can be held to appropriate tolerances. An advantage of the construction of the present invention in which the sleeve 42 is a separate part from the spool is that side loads on the sleeve applied by the pins 43 and 47 and the detent plunger 51 are not transmitted to the spool, but directly to the body of the valve 10. It is a matter of This reduces the chance of binding of the main spool 11 since it is only subjected to axial loads.

In the absence of an external force, spool 11 is held in a neutral position by a spring arrangement within housing 52. The edges 53 and 54 of the spool 11 are connected via a passage 56, a slot in the eel control valve 57 and a hole in the pressure regulating spool 5B to a chamber connected to the inlet 12 to which a passage 58 and a pressure source are connected. 55.

The edges 61 and 62 of the spool 11 taper upward in their diameter and discharge from the chamber 63 into the chamber 27 and from the chamber 64 into the chamber 2B in the neutral position.

Chambers 63 and 64 are connected to a shuttle valve 65 so that only the greater of the two pressures is in chamber 66 and in chamber 68.
allows sensing through the orifice 67.

In neutral, the pressure in all of these chambers is tank pressure, and chamber 66 is connected to load sensing signal port 1 via inhibit valve 69.
3. If valve 22 is also neutral, the inlet pressure source will be at standby pressure when the load sense port pressure decreases to tank pressure. In this state,
In the case of a fixed displacement pump 17, all pump flow is bypassed to a tank or other circuit by leaving valve 1B. In the case of variable displacement pump 21, the displacement is sufficient to maintain leakage at standby pressure.

When the spool 11 moves to the left, the sleeve 42 also moves with it. The sleeve 4B joins the pin 43 after only a slight initial movement and lifts it out of the valve seat over its orifice 41. When the ball 38 disengages from its seat, the oil in the entire 88, passage 37 and chamber 71 can drain into the chamber 27 through the hole 36. This creates a pressure differential on either side of the poppet deterrent valve 34, thus unseating the valve and opening communication between the poppet 32 and the chamber 63.

When the spool 11 moves further to the left, the edge 54 moves into the chamber 55.
The flow path between the chamber 64 and the chamber 64 is opened.

Also, the edge 62 of the spool 11. closes the flow path between chamber 64 and chamber 28 . The edge 61 of the spool 11 is connected to the chamber 63 and chamber 2.
Open the flow path between 7 and 11i-d. Oil flowing to chamber 64 cannot flow into passage 33 until the pressure in chamber 64 is greater than the pressure in passage 33. The pressure in chamber 64 is increased to the required level as follows.

The pressure in chamber B4 is passed through shutoff valve 65, chamber 66, inhibit valve B9 and load sensing port 13 to port 14 and is raised to the level of the pressure in port 15 plus the standby pressure of the release valve. . The pressure of the port 15 is the port 12, the passage 5E1.5B,
55.64 and is returned to valve 10. Therefore, chamber 64
The pressure continues to rise until the check valve 35 opens and flow is directed to the cylinder 24.

Return flow from the cylinder enters valve 10 at port 23 and passes through passage 3
2 and chamber 63 and is discharged into chamber 16.

Pressure regulating spool 58 is provided with means to ensure that the flow of oil from chamber 55 to chamber 64 is proportional to the area opened by edge 54 of the spool. In the following discussion, it will be assumed that the flow control valve 57 is wide open so that the flow area of the flow control valve is significantly larger than the flow area exposed by the edge 54 of the spool. The flow area exposed by edge 54 is made to follow a suitable function of axial movement of spool 11. For example, area can be directly proportional to movement. Flow past a sharp edge orifice is generally determined by the formula o = K A#
Follow. In the formula, Q-flow, K=constant, 8-flow area, P-
is the pressure drop across the flow area. This formula shows that the flow rate Q is proportional to the flow area by keeping the pressure drop across the area constant.

The pressure regulating spool 5B is required to do this.

The pressure drop P is the pressure difference between the pressures in chambers 5, 5 and 64. The pressure in chamber 55 is sensed at the left end of spool 5B, and the pressure in chamber 6
4 pressure is sensed at the right end of the spool in cavity 6B.

The spool is connected to the force on the spool due to the pressure difference P across it, and when the force due to the force difference exceeds the spring force, the spool 58 blocks the inflow at the metering edge 73, restoring the force balance. Similarly,
If the pressure drop falls below that required to maintain equilibrium against the spring force, spool 58 will attempt to reduce the restriction at edge 73 and restore equilibrium. In this way,
The flow over the edge 54 of the main spool 11 remains nearly constant at a given location on the spool, regardless of variations in supply or load pressure. One advantage of keeping the pressure drop constant over the measured area of the main spool 11 is that the flow force on the spool is also constant and is usually lower than in a construction where the maximum possible pressure drop can occur across the spool. It is. Reducing the flow force means that the effort required to move the spool is reduced, which is advantageous during manual operation of the valve.

As the spool 11 continues to move further to the left, the discharge flow increases proportionally to the area opened by the edge 54. When the maximum flow position is almost reached, the sleeve 42 causes the vacuum piston to rise.

This is perceived by the operator as an increased resistance to further movement of the spool. By including this feature, the operator has a means of sensing when the spool is about to lock. If the operator wishes to lock the spool, he can push the spool a little further and the detent piston 51 continues to hold the sleeve 42 and spool 11 in that position. If the operator does not wish to lock the spool, there will be an indication that the maximum flow position of the spool has been reached. This feature is desirable when the valve is continuously stroked, such as in loader operation.

The spool 11 can be uninhibited and returned to neutral either manually by overcoming the resistance of the detent piston 51 or automatically when the system pressure reaches a preset value. When the pressure in chamber 55 exceeds the pressure set in safety valve 74, oil flows into chamber 75 and is forced back onto the restraining piston so that sleeve 42 (and spool 11) can return to the neutral position. This feature is necessary when the spool is restrained and the cylinder '25 moves until it reaches the end of its stroke, so that the pressure is not released by the pump when it returns the spool 11 to neutral. Increased to safe pressure. Once spool 11 returns to neutral, the power in chamber 55 drops to the standby level, safety valve 74 is reseated, and detent piston 51 is returned by its spring.

Throughout the leftward movement of spool 11 and sleeve 42, bottle 43 continues to hold ball 39 up from its seat, so that poppet deterrent valve 34 also disengages from its seat, returning oil from passageway 32 to chamber 63. and chamber 37 to allow free flow.

The function of the flow control valve 57 is to limit the maximum flow from the valve to the current value when the spool 11 is moved to the left and placed in the 1 detent position. This is the control lever 78
This is done by changing the flow area by rotating the valve 57 through the .

Since the flow through the valve is such that the pressure drop is proportional to the flow area maintained by the pressure regulating spool 58, the varying area 7B effectively controls the flow through the valve when the spool 11 is in its detent position.

As the spool 11 moves further to the left after reaching the first detent position, it reaches the second detent position, which corresponds to the float position of operation of the valve 10. Cam sleeve 42
has a groove corresponding to this position in which the detent piston 51 holds the sleeve and spool in restraint. Spool 1
In the float position of 1, the edge 77 of spool 11 has moved far to the left proximate the passageway between chambers 55 and 64. Edge 77 of spool 11 thus allows free flow between chamber 64 and chamber 28. Free flow is also room 63 and room 2
It is possible between 7. Spool edge 54 prevents any flow from chamber 55 to chamber 63. When sleeve 42 moves to the float position, bin 47 is moved to raise ball 48 from its seat, allowing flow from chamber 79 through passageway 45 and chamber 46, through A-refrigerator 49, and into chamber 28. becomes.

The pressure in channel 33 then pushes poppet 35 away from its seat, into chamber 64 and thence into chamber 28.
allow free flow of information.

In the float position, both outlets 23 and 24 are connected to chamber 27.
and 28, respectively. This allows the piston to float within the cylinder 25 at whatever position it is pushed to occupy as a result of an external force acting on it.

The sequence of events that occur when the spool moves to the right is similar to what occurs when the spool moves to the left.

There is only one detent position when the spool moves to the right. There are no float positions in this direction.

Spool edge 53 moves to the right, allowing flow from introduction chamber 55 to enter chamber 63.

The pressure in chamber 63 is returned to the pump through shuttle valve 65 and sensing port 13 and the pressure begins to build until it exceeds the pressure in passageway 32 and opens poppet suppression valve 34.

Flow can then proceed to the outlet 23 and the rod end of the cylinder 25. As the sleeve 42 moves with the spool 11 to the right, it moves the bottle 47 and raises the ball 48 from its seat. This allows the oil in chamber 79, passage 45 and chamber 4B to be discharged into chamber 28 through orifice 4B. When pressure is present in passageway 33, flow occurs across A-refit 44 and poppet 35
The resulting pressure difference on either side of the poppet moves the poppet off its seat, causing flow from passage 33 to enter chamber 64 and then through edge 62 of the spool and discharge into chamber 28. enable.

The flow control is controlled by chambers 55 and 6 when edge 53 moves to the right.
It can be obtained by changing the flow area between 3 and 3. Once the spool is in the right detent position, maximum flow can be set by rotating the flow control valve 57. When the pressure in the pressure chamber 55 exceeds the value set in the safety valve 74, the detent piston 51 returns and the spool 11 is released from the detent position.

It is possible for the valve to operate with a single-acting cylinder, such as cylinder 26 as shown in FIG. In this valve, it is preferable to attach such an actuating cylinder to the port 23 of the valve. In the differential mode, the valve 81 rotates 90'' and connects the shuttle valve 65 to the sensing port 13 on one side and the chamber 6 on the other side.
Communication with 4 is cut off. The advantage of this is that when the load is lifted (by moving the spool 11 to the left), the introduction chamber 5
5 flows into chamber 64 and from there is prevented from returning to load sensing port 13 by valve 81. Therefore, the pump output pressure will not rise to the safe pressure of the system as it would have if valve 81 had been opened to the left. This is because the chamber 64 becomes stuck due to the blockage of the outlet 24. Therefore, the pressure in chamber 64 cannot reach the equilibrium pressure corresponding to the load pressure. When the spool 11 moves to the right, oil flows into the single-acting cylinder 26, causing the piston to extend. What follows is similar to that described previously when the spool moves to the right.

The hydraulic valve shown in FIG. 1, which has been described so far, is constructed so that most of its parts and mechanical operation can be used in the electronic liquid valve shown in FIG.

The sleeve 42 used in FIG. 1 is replaced in FIG. 2 by a simpler sleeve 82.

This sleeve does not have an eyetent groove, but an O-ring groove 83.
is added. The detent piston 51 is not used since the detent characteristic is available in the III handle. Detent release safety valve 74 is eliminated. A pressure switch 84 is applied to the electronic hydraulic valve to provide a signal to the control handle to release the detent at a predetermined pressure. The manual flow I11 control valve 57 is eliminated since the same functionality can be achieved by electronic means. When the spool 11 is moved by a flow controlled by electro-hydraulic means, the ends 85 and 86 of the spool are used as pistons.

One method of electro-hydraulic actuation is shown in FIG. This is based on an earlier U.S. patent application entitled [Electronic Hydraulic Proportional Actuator], entitled Inventions by G. Rashagopal and H. Niss Basrai, assigned to the assignee of the present application.
U.S. Pat.
This is explained in detail in US Patent Application No. 301,789, filed in Japan. Solenoid type three-way valves 87 and 88
is used to direct oil to and from ends 85 and 86 to move spool 11 to the left or to the right, or to hold it in the one-stroke position. A position transducer 8B is used to transmit the position of spool 11 back to the electronic control unit. A pressure regulator control valve 91 is used to limit the speed of movement of the spool 11 to a maximum value.

A feature of the valve embodying the invention is a load restraint structure attached to the valve at ports 23 and 24 and used to lock a hydraulic motor or cylinder.

The poppet deterrent valves 34 and 35 and the pilot poppet balls 39 and 48, together with their corresponding seats, have very low leakage, and when the valve spool 11 is in the neutral position, the load attached to the valve changes little over time. It is not possible to issue aS+.

In valves without load restraint, leakage is reduced by keeping the clearance between the spool 11 and its bore at the lowest achievable value. The use of a load restraint device allows for larger clearances between the spool and the bore, allowing for correspondingly larger tolerances during construction without problems with leakage. In this valve, the main load restraint valves 34 and 35 are controlled by a pilot device mechanically actuated by a sleeve 42 or 82 that moves with the spool 11.

When increasing or decreasing tA, only the load suppression valve in the return oil passage is operated mechanically. Other load suppression valves are actuated by an increase in inlet pressure in the hydraulic system sufficient to displace the load.

A sudden drop in load due to insufficient introduction pressure is therefore not possible. Since the return load suppression valve is mechanically operated, it is possible to lower the MW even if the hydraulic pump is shut off. This feature is useful when the operator switches off the engine on the machine and the load or equipment is in the raised position. The operator can lower it to a safe position without having to switch the engine back on. If the valve is electro-hydraulic operated, hydraulic pressure is required to move the spool 11, so the load cannot be lowered by remote electrical control. However, the load can be lowered by mechanically moving the spool 11 if it is accessible.

Other features of the present structure are best illustrated by comparison with the approximate structure shown diagrammatically in FIG. This diagram shows a dual-actuating cylinder used to prevent the load from slowly dropping due to leakage through the valve spool of a control valve (not shown).
An operation suppression valve 83 is shown. The figure shows fluid flow as the control valve moves to extend the piston 96 of the dual actuation cylinder 84. Liquid pressure entering through conduit 95 is applied against floating piston 8B of deterrent valve 93, which due to its large volume overcomes spring 87 and returns pressure behind ball 9B in return passage 9B. This allows return flow through return conduit 101 to the control valve. Fluid flowing into conduit 85 unseats restraint ball 102 and extends the cylinder. That is, as shown in FIG. 3, the piston 82 is moved in one direction. piston 92
The direction of can be changed by redirecting the flow of fluid into and out of conduit 95101.

Hydraulic load suppressors only operate when hydraulic system pressure is available, which means that they cannot be lowered to a safe position only when the engine is on. If the operator forgets to reduce the load before turning off the engine and the valve control handle is left in the detented position, a dangerous situation will occur when the operator restarts the machine. Even though the engine is turned off, the load may drop suddenly because the control handle is in the detent position. When lowering a heavy load using a load restraint device as shown in FIG. If it is too large, you may run into a problem where there is no response at all. This limit does not exist with the valves shown in FIGS. 1 and 2.

Other features of the valve described here include the sleeve 4 for many functions.
2 is to be used. This reduces the overall length of the valve and reduces the number of parts. The sleeve 38 has the following functions.

1, it operates pilot actuation bins 43 and 47, thereby actuating main poppets 34 and 35;

2.Equipped with grooves for restraint in three positions: rising, descending and floating. Counter-groove angles are used on some surfaces to provide low resistance to initial movement and provide restraint to return spring forces.

3. The sleeve provides a sense of resistance before falling into the detent state, so that the operator who does not wish to detent the spool will activate the sensing means when stopping.

4. The same sleeve also provides actuation of both pilot actuation bins 43 and 47 when float type actuation is required.

5. The sleeve insulates the main spool 11 from side loads caused by the operation of the pilot operated valve and detent piston.

6. It works as a piston.

A further feature of the invention is that most of the mechanical components can be used in both mechanically and electro-hydraulically operated valves.

A further feature is that the device has a single-acting force type, so that the pressure of the device does not rise to a safe pressure when the single-acting cylinder is lowered.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a hydraulic valve according to a mechanically actuated embodiment of the invention, FIG. 1A shows another actuator attached to the hydraulic valve shown in FIG. 1, and FIG. 2 shows an electrically controlled hydraulic valve. 3 is a diagrammatic representation of a load restraint device according to the prior art, showing an alternative embodiment slightly different from that of FIG. 10: Valve body, 11: Main spool, 12: lJ
Inlet, 23.24: Outlet, 25 Niji Linda,
26: Single acting cylinder, 32.33: Passage, 34.35: Poppet suppression valve 38.48: Ball, 42 Ni sleeve, 43.47: Bottle, 56.51 Passage. Representatives Akira Asamura and 4 people

Claims (1)

[Claims] [a hydraulic valve for controlling the flow of hydraulic fluid from a source of fluid under pressure to at least one load transfer hydraulic motor and from a source of fluid under pressure, the valve comprising: a valve body; axially movable for directing fluid through a selected one of a number of passageways extending within said valve body from a fluid inlet connection connecting to a hydraulic motor to one or more fluid connections connecting to a hydraulic motor; a main spool arrangement housed within a front valve body, the hydraulic motor having a main spool arrangement in which the hydraulic valve has a single actuating cylinder assembly or multiple actuating cylinder assemblies; and a spool operating device operable to move said main spool device from a neutral position in either axial direction and actuate a hydraulic motor to move a load coupled thereto in a desired direction. , a load position holding device, the load position holding device reducing leakage caused by undesired movement of the load through the main spool device from the holding position when the main spool device is in the neutral position. A hydraulic valve adapted to have a pilot-operated poppet valve operated to.