JPS5840056B2 - controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a controller for varying the control pressure for a variable control valve used for supplying fluid to a variable displacement pump or a servo of a motor.

When designing a controller for a hydrostatic transmission, it is common to design individual controllers, each with the required functionality.

For example, a pressure override controller (P, 0.R) is designed to detect high pressures on the transmission in order to avoid overloading the transmission.

P, 0. R-controllers are known, some of which are described herein, and anti-stall controllers reduce the stroke of a pump swashplate in response to a load on the pump prime mover. It is commonly used in

Anti-stall controllers directly control the movement of the valve spool, and thereby control fluid pressure, and are generally equipped with regulators (
U.S. Patent Nos. 2,516,662 and 2,976
．． 685) is used.

Another type of controller increases the displacement of the rotating swashplate of the pump in the fluid transmission first to its maximum value and then decreases it to its minimum value, and maintains such a displacement throughout the deceleration. There is a phase controller used to reverse the process.

Phase controllers are generally cams (U.S. Pat. No. 2,516,66
(See No. 2) is used.

Input torque limiter (1, T, L) that matches the torque of the fluid transmission device with the torque of the prime mover as another controller
There is.

1. T, L generally uses a cam to reset the compensation override pressure for each swashplate position to maintain a constant value of system pressure times pump volume.

Another known 1, T, L is hydraulic, in which the pressure drop across the compensating or overriding spool is kept proportional to the volume of the pump.

This is generally accomplished with a variable orifice.

Still other known 1. T and L are electrical types.

In this, the pump volume and system pressure are measured and then multiplied to generate a signal that is used to control the pump volume.

Electric type known to the applicant 1. T and L all use pressure transducers.

Although each of the above-mentioned controllers performs its individual functions satisfactorily, they are fairly complex, difficult to adjust, and expensive.

Furthermore, there are separate and independent controllers for each purpose.

Generally, each part of a controller cannot be used as parts of other controllers.

Therefore, when controlling the operation of a hydrostatic blade transmission including a variable displacement pump, a variable displacement motor, or a pump/motor combination, a simple and inexpensive controller that performs multiple functions, as well as a hydrostatic blade transmission. It would be desirable to provide a simple and easily installed controller that performs any of the numerous functions of either a pump or a motor.

Figures 1 and 2 show a device that can meet the above expectations, and this has already been filed in the patent application filed in 1982-4 by the applicant.
It has been filed as No. 3092 (Japanese Unexamined Patent Publication No. 53-5365).

The hydrostatic blade transmission includes a variable displacement rotating swash plate axial piston pump 10 fluidly coupled to a constant displacement motor 12 via conduits 14,16.

This pump 10 drives rotating parts and has check valves 22.
24 and a pair of known piston-cylinder type servos 28.3 used to drive the charge pump 20, each in communication with a conduit 14.16.
includes a rotating swash plate 26 movable across the center by 0;

A known control mechanism 34 is then coupled in parallel with the motor 12.

The charge pump relief valve 36 is in communication with the output side of the fuel pump 20.

Pump 10, motor 12 and charge pump 20 are all in communication with reservoir 38.

Filter 40 connects pump 10 and motor 12 to storage tank 3
It is provided in the middle of the relief conduit leading to No.8.

The servos 2B, 30 are in communication with a manual servo control valve 46 via conduits 42, 44.

Conduit 48 connects the spring chamber of control valve 46 to the reservoir.

Another conduit 50 connects the bore of control valve 46 to a known charge pump.

Control valve 46 includes a linkage that connects control valve spool 54 to the swashplate when the position of control lever 52 and swashplate correspond to the desired position set by control lever 52.

Electrical/pressure controller 56 connects first bore 58 and second bore 6
Including cases with 0.

A plurality of axially disposed annular grooves 62, 64, 66 are provided within the first bore 58 and communicate with the refueling pump 20, the servo control valve 46, and the reservoir 38, respectively.

A spool 68 is disposed in bores 58, 60 and includes a pair of axially disposed lands 70, 72 in bore 58 and another land 74 in bore 60. Adjustable spring 76 1 elastically pushes the spool 68 to the right in FIG.
communicate between.

A pair of chambers 80,82 are formed within bore 60 on opposite sides of land 74.

Chamber 80 is maintained in constant communication with the reservoir, while chamber 82 is in fluid communication with charge pump 20 through orifice 84 and with reservoir 38 through conduit 86 and variable force valve 88.

Valve 88 includes a spool 90 on which a varying force is applied.

The leftward movement of the spool 90 in FIG.
Port 92 is gradually closed, thereby creating a variable orifice.

Accordingly, the rightward movement of spool 90 in FIG. 1 gradually opens port 92.

The leftward force acting on the spool 90 is controlled by the electric controller 9
It is directly related to the amount of current flowing out from 4.

Electrical controller 94 is connected to a power source 96 and to a rotating swashplate position indicator 98 .

The rotating swash plate position indicator includes a variable resistor 100 and a pointer 10
Contains 2.

Accordingly, an electrical signal indicating the position of the swashplate is supplied to the electrical controller 94 through the swashplate position indicator 98.

The position of the rotary swash plate 26 of the pump 10 depends on the displacement of the pump 10,
It is therefore directly related to the volume of fluid flowing from pump 10 to motor 12 at a given speed of input shaft 18.

The electric pressure controller 56 further includes a roller needle 1 having one end in contact with the land 74 and the other end communicating with the high pressure oil conduit 14 or 16 via a shuttle valve 106.
Including 04.

Therefore, the leftward force exerted on spool 68 by roller needle 104 will be directly proportional to the maximum pressure within conduit 14.16.

In most cases, this pressure is the pressure of fluid flowing from pump 10 to motor 12 to drive output shaft 32.

Electrical/pressure controller 56 is shown in a state similar to that of a hydrostatic blade transmission input torque limiter connected.

Many other methods can be used to control the operation of the hydrostatic blade transmission by including the electrical controller 94, as will be discussed below.

Electrical and pressure controller 56 operates as follows.

It is well known in the fluid pressure art that system pressure times volume (volume of fluid) is directly related to the torque of a pressure system.

Therefore, by keeping the value of system pressure times volume constant, one provides a torque limiting device for the system, thereby reducing the maximum torque of the fluid system to the maximum torque provided by the prime mover used to drive input shaft 18. can be matched.

As shown, the varying volume of pump 10 is provided to electrical controller 94 via rotary swashplate position indicator 98.

System pressure is provided to roller needle 104 via shuttle valve 106.

As the system pressure acting on the roller needle increases and overcomes the force of spring 76, the pressure of fluid delivered from charge pump 20 to servo control valve 46 decreases.

This means that the land 7 is located at the position where the annular grooves 64 and 66 communicate.
2 is caused by movement.

As the pressure on the servo control valve 46 decreases, the centripetal moment of the pump 10 and the forces within the servo 28,30 reduce the volume of the pump to the volume required to maintain the aforementioned system pressure.

As this volume decreases, an electrical signal is provided to electrical controller 94 via rotary swashplate position indicator 98.

This reduces the leftward force on spool 90, thereby reducing the pressure of the fluid in chamber 82 and allowing spool 68 to move back to the right in FIG. resulting in flow to servo control valve 46.

Similarly, as system pressure decreases, spool 68 increases the pressure of fluid from charge pump 20 to control valve 46, thus increasing the volume of pump 10.
Move to the right in FIG.

However, while this phenomenon is occurring, the rotating swash plate position indicator 9
8 moves the spool toward port 92, thereby increasing the pressure within chamber 82, increasing the leftward force acting on spool 90, and providing an electrical signal to the electrical controller.

This pressure increase causes the spool 68 to move to the right in FIG.
is set to maintain the maximum charge pump pressure of si.

Variable force valve 88 varies the fluid pressure within chamber 82 from 10 psi to 1 psi.
It is provided to remain linear in response to a signal from an electrical controller 94 up to 50 psi.

The high pressure relief valve in the control mechanism 34 is typically 3,500 p.
si to 6,000 psi.

Appropriate modifications to the area of land 74 that is subject to fluid pressure within chamber 82 and the area of roller needle 104 that is subject to system pressure can be made by one skilled in the art.

The operational design for the electronic circuitry used in electrical controller 94 is performed by those skilled in the art of electrical controllers.

In FIG. 2, charge pump 20 is shown in passage 108.1.
10 and to controller 56 .

Passage 111 communicates with servo control valve 46 via conduit 50 .

A passageway 112 communicates chamber 80 with the reservoir.

The spool 68 is disposed within the multi-stage bore 114, 116° 118 and lands 120, 122° 124, 126, 1
Contains 28,130.

The land 120 has a spring 7 that allows fluid to be adjusted from the inner hole 114.
6 is prevented from flowing into the room containing the 6.

Lands 122 or 124 contact the wall of bore 114 depending on the position of spool 68.

The land 126 allows fluid to flow from the passage 111 to the inner hole 114°11.
6 into chamber 80 and then through conduit 112 to the reservoir spaced from the wall of bore 116 .

Lands 128 and 130 are in contact with the walls of bore 118.

The variable force valve 88 is shown as a standard proportional pressure control valve model 80 supplied by Fima Corporation of Voltage, Michigan, USA.

In FIG. 1, the variable orifice formed by spool 90 and port 92 is connected to variable orifice 1 within valve 8B of the figure.
Illustrated as 32.

Orifice 132, like orifice 84, is a component of a flamer valve.

Passages 134, 136 in controller 56 extend from passageway 110 through bore 118 to orifice 84 and from passageway 86 to orifice 84, depending on the extent to which variable orifice 132 is opened.
12 so as to guide the fluid to either of them.

Adjustable spring 76 is locked to an adjustable stop 138 that is threaded into or removed from controller 56 .

The position of the stop controls the rightward force on spool 68 by spring 76.

During operation, fluid pressure within chambers 82, 140 of shuttle valve 106 acts against land 130 and roller needle 104 to move spool 68 to the left in FIG. 2 against the force of spring 76.

As the spool 6B is moved to the left, the land 12
Fluid flowing from the refueling pump 20 through the passage 108 around the 2 to the passage 111 and further to the servo control valve 46 gradually flows until a point is reached where the land 122 contacts the wall of the bore 114 to stop such flow. limited to.

At this point, land 124 has moved away from the wall of bore 114 to allow communication between passage 111 and bore 116 for fluid to return from passage 111 to the reservoir.

It will therefore be readily determined that the fluid pressure conducted through passage 111 from refueling pump 20 is directly related to the position of spool 68 within controller 56.

The position of spool 68 is directly related to the force it receives from spring 76, the force it receives from the fluid pressure in chamber 82 relative to the area of land 130, and the force it receives from the fluid pressure in chamber 140 relative to the area of needle roller 104. do.

Shuttle valve 106 is a separate housing 142 secured to housing 146 of controller 56 by bolts 144.
including.

If desired, the shuttle valve 106 can be removed and the plate bolted onto the housing 146 in its place.

In this latter arrangement, fluid pressure within chamber 82 and the force of spring 76 are two factors used to position spool 68 within valve 56.

Various electrical controls are designed to operate variable force valve 8B and control fluid pressure within chamber 82.

These controllers can take input from the position of the rotating swashplate of the variable displacement pump and/or variable displacement motor.

Additionally, the pressure of the fluid in chamber 82 directly blocks passageway 110 and moves needle roller 104 at the valve shown in FIG. 2 due to system pressure.

The electrical controller is also actuated by the prime mover to rotate the input shaft 18 of the pump 10 and the position of the swash plate 26 to prevent the prime mover from stalling during overloads.

Additionally, fluid chamber 82 is connected to the spring end of spool 68;
It is used to apply a force against the force received from the roller needle 104.

The operation of orifice 132.84 may also be interchanged in FIG. 2, thereby allowing orifice 83 to be a variable orifice controlled by variable force valve 88 and orifice 132 to be a fixed orifice.

Additionally, instead of using variable force valve 88, an on-off valve such as the Model 103 B5-12VDC 12-way NC cartridge available from AMBAC Industries, Inc.'s Fluid Systems Division may be used.

In FIG. 2, this on-off valve operates to either fully open or completely open a restriction formed in passage 132.

By reversing the on-off valve, this pressure is reduced to chamber 8.
2, thereby performing substantially the same function as that performed by variable force valve 88.

Also, the operation of orifice 132.84 is similar to that of orifice 1
Interchangeability can be achieved by making 32 a fixed orifice and orifice 84 being fully opened, fully closed, or alternately by the operation of an on-off valve.

FIG. 3 shows a device according to the invention that can be used in place of valve 46 and controller 56 in FIG.

Electrical and pressure controller 198 in FIG.
Contains 00.

Controller 198 includes a housing 206 having a second port 208 for receiving oil from charge pump 20 of FIG.

The second port 208 communicates with a bore 210 via a passageway 212 at right angles, within which the spool 204 is disposed perpendicularly to the port 208 .

The second port 208 has a passageway 214 and an orifice 216.
It communicates with the annular groove 218 of the spool 220 via.

Spool 220 is disposed within bore 222 of housing 224, which is attached to housing 206 by bolts 226.

First port 228 and fourth port 2 of housing 206
30 are connected to piston and cylinder servos 28 and 30 via holes 232 and 234, respectively.

The first port 228 and the fourth port 230 are further connected to the passage 2.
12 at spaced locations on either side of the bore 210 .

Enlarged third port communicating with inner hole 210) 236°275
communicates with the storage tank 38.

The exact connections are illustrated in detail in FIG.

Housing 224 includes a passageway 238 that communicates with a passageway 239 provided in an on-off valve 240, such as that previously described and manufactured by Fluid Power Systems.

Passage 242 in housing 224 connects passage 239 to annular groove 244 in spool 220 .

The annular groove 244 communicates with the inner bore 222, the third port 236, and the reservoir 38 via a passageway 246 in the spool 220.

Internal bore 2222 forms a chamber 248 at one end of spool 220.

The annular groove 218 of the spool 220 defines the passageway 25 of the spool.
The other end of the spool 220 communicates with the chamber 252 via the spool 220.

Chambers 248, 252 in FIG. 3 function similarly to chambers 80, 82 in FIG.

Reciprocating valve 25 similar to shuttle valve 106 in FIG.
4 is attached to housing 206.224 by bolt 226
mounted on.

The function of reciprocating valve 254 is the same as that of reciprocating valve 106 in FIG.

Passage 239 of valve 240 is shown in FIG.

Valve 240 is used to open and close the passageway in response to electrical input sent via lines 258 and 260.

By opening and closing passageway 239, the pressure within chamber 252 is controlled to change the position of spool 204 in a manner similar to that described for controller 56 of FIG.

The input to valve 240 is at a relatively high frequency, e.g.
ps and is controlled by appropriate electrical circuitry responsive to controlled inputs similar to those sent to electrical controller 94 of FIG.

In this manner, on-off valve 240 can act similarly to variable force valve 88.

It is contemplated that the housing portions of FIG. 3 may be replaced with corresponding portions shown in FIG. 2.

Also, by appropriately designing housing 224, variable force valve 88 can replace on-off valve 240.

Additionally, the reciprocating valve 254 can be removed and replaced with a flat plate as described with respect to FIG.

The advantages of the device of the invention shown in FIG. 3 over that shown in FIG. 2 will be explained in detail in the description of FIGS. 4-6.

Some of these advantages reside primarily in the construction of housing 206 and spool 204.

The same parts shown in FIG. 4 as in FIG. 1 are given the same numbers.

The motor 12 of FIG. 1 is shown in FIG. 4 as a variable displacement motor 262 controlled by piston-cylinder servos 264,266 in a known manner.

Conduits 268 and 270 direct fluid to servos 264 and 2, respectively.
66.

The spool 204 has a pair of axially spaced lands 272.
, 274.

Spacing between lands 272 and 274 and the first port 228, second port 208, and fourth port 2 in the inner hole 210
30, first, from the second port 208 to the inner hole 210.
to the fourth port 230 via the conduit 44 to the servo 30 while simultaneously accommodating the reservoir 38 and the spring 202 from the servo 28 to the first port 228 via the conduit 42 and from the bore 210. 3rd port 2
75.

When the spool 204 moves to the left from the position shown in FIG.
The land 274 first connects to the fourth port 23 as shown in FIG.
0 and the second port 208 is cut off.

Then, when the spool 204 moves further to the left, the sixth
As shown in the figure, communication between the first port 228 and the storage tank 38 is cut off, and the first port 228 is connected to the second port 228 through the inner hole 210.
communicates with port 208 and at the same time communicates with fourth port 23
0 communicates with the storage tank 38 via the inner hole 210 and the third port 236.

Spool 204 is land 274 or land 272
It is designed to be weighed.

In this way, high pressure fluid can be transferred to either servo 30 or servo 28.
The capacity of the pump 10 is changed by flowing toward the pump 10.

By using the apparatus of FIG. 3, the control valve 46 of FIG. 1 can be eliminated.

Control valve 198 is also used to control the displacement of motor 262 by directing fluid to servos 264 and 266.

Controller 198 replaces valve 46 and controller 56 in the circuit shown in FIG.

The fourth port 230 corresponds to the passage 111, and the second port 208 corresponds to the passage 108.

The land 274 has the first port 228 connected to the second port 208.
Since the spool 204 is metered before communicating with the second
It operates in the same manner as spool 68 shown.

Hole 232 is used to seal first port 228 from the atmosphere.
A plug is placed inside.

The variable force valve 88 is the on-off valve 240 of the housing 224.
can be easily interposed.

It can be seen that in the apparatus of FIG. 3, orifice 216 replaces orifice 84 of FIG.

Passage 136.86 in FIG. 2 corresponds to passage 23 in FIG.
8, and the passage 242 in FIG. 3 corresponds to the passage 112 in FIG.

Orifice 132 of valve 88 in FIG. 2 can be seen to be located between passageways 238 and 242 in FIG.

This can be easily achieved by implementing a suitable design.

Thus, by varying the orifice 132, the pressure within the chamber 252 will cause the fluid to flow into the passages 238, 242 . Groove 24
4° passage 246. The change can be made by sending fluid through chamber 248 to reservoir 38 .

Such design capabilities are within the knowledge of those skilled in the art.

Valve 240 also opens or closes passageway 239 between passageway 238 and passageway 242.
Used to control the operation of spool 204.

In this manner, the spool 204 routes fluid from the second port 208 to the fourth port 230 when the pressure of the fluid within the chamber 252 is relatively low and when the pressure of the fluid within the chamber 252 is relatively high. When the fluid is transferred from the second port 208 to the first
Used to flow to port 228.

Valve 240 is either turned on to open passage 239 between passage 238 and passage 242 or turned off to open passage 239 between passage 238 and passage 242 when no electrical signal is sent. Will it be closed?

In this manner, lines 258, 260 are easily connected to a power source 96 and known electrical on/off switches as shown in FIG.

The apparatus shown in FIGS. 3-6 can be driven to displace a variable volume unit or to return it to a neutral state.

It may be used with a variable displacement pump or motor, with or without a reciprocating valve, and with or without a variable force valve 88 or an on-off valve 240.

If desired, the 71 housing 224 of FIG. 3 may be bolted directly to the housing 206 to form a pressure compensating valve.

With the aforementioned components in mind, Figures 7 through 18:
These components, namely 206, 240, 254 in FIG.
Component 88 of FIG. 2 and component 224 modified as heretofore proposed to accommodate component 88 or 240 are shown.

Other variations are also possible.

Simply put, the controllers shown in FIGS. 7 to 19 are as follows:
It works like this:

Figure 7 shows P, 0. R controller is shown with reciprocating valve 254 connected through line 14.16 and housing 206
is interposed between the oil supply pump 20 and the valve 46 shown in FIG.

When the pressure in line 14 or 16 exceeds a predetermined value, valve 46 allows fluid flow to reservoir 38 and discharges from pump 10.

An anti-stall controller is shown in FIG. 8, with the reciprocating valve 254 replaced by a flat plate.

A suitable electrical signal is sent into variable force valve 88 to direct fluid flow in the circuit of FIG. 1 from charge pump 20 to reservoir 38.
1160 between valves 46 that communicate with each other.

The input signal to valve 88 is controlled by inputs from the rotational speed of input shaft 18, the given throttle setting of prime mover drive shaft 18, and the desired throttle setting.

Thus, as the speed of the prime mover decreases, valve 88 increases the pressure in chamber 252, for example, FIG.
This causes the pump 10 to discharge fluid.

A horsepower limiter is shown in FIG. 9 and has already been described in connection with the devices of FIGS. 1 and 2.

The device of FIG. 10 is a pressure override that operates in a manner similar to the device of FIG. 7 when power is sent to the on-off valve 240.

When power is shut off from the on-off valve 240, pressure increases within the chamber 252 of FIG. 3, for example, thereby causing the reservoir 38
from the valve 46.

The controller of FIG. 11 is similar to the controller of FIG. 10, except that it reduces the J positive stroke when power is supplied to valve 240.

Fig. 12.13'□The ϕ controller is the same as that described for the embodiments of Figs. 3 to 6, except that the reciprocating valves 2's, 4' +It is lacking.

In the controller of FIG. 12, when no electrical signal is sent to valve 240, the pump is directly returned to the neutral state by this controller, and the pump is returned to the neutral state, and in the controller of FIG. When supplied, □ returns to neutral state and is driven.

The controller of FIG. 14 utilizes the spool apparatus of FIGS. 3-6 and is therefore directly connected to the variable displacement pump as shown in FIG.

Movement of spool 204 is controlled solely by the pressure of the fluid in line 14 or 16.

The controller of FIGS. 15 and 16 further adds an on-off control aspect to the controller of FIG. 14 so that the spool 204 is controlled not only by the pressure of the fluid in lines 14 or 16, but also by the passage 239 being opened. Depending on whether the
It responds to the pressure of the fluid within chamber 252 of the figure.

In the controller of FIG. 15, passage 239 is powered by valve 2.
40, and in the controller of FIG. 16, passage 239 is open when no power is sent to valve 240.

The controller of FIGS. 17-18 eliminates the reciprocating valve 254 of the controller of FIGS. 15-16, but continues to utilize the on-off valve 240 and associated housing 224.

In these latter two controllers, the ports of the controllers of FIGS. 3-6 are connected to the servo 2 of motor 262 of FIG.
66.264 to vary the output of the motor in response to an electrical signal sent to valve 240.

In the controller of FIG. 17, passage 239 of FIG. 3 is open when power is delivered to valve 240, while in the controller of FIG. 18, it is open when power is not delivered to valve 240.

As previously mentioned, many of the controllers of FIGS. 7-18 can be used to control either a pump or a motor in response to a given input.

In view of the above examples, another variation of these controllers is valve 8.
Those skilled in the art will appreciate that this can be implemented in response to a given electrical signal sent to the 8,240.

[Brief explanation of drawings]

Fig. 1 is a diagrammatic layout of a previously proposed hydrostatic transmission device similar to the present invention, Fig. 2 is a sectional view of the main parts of the same, and Fig. 3 is a main part of an embodiment of the present invention. 4 to 5 of the cross-sectional views are drawings showing the operating state of a further part of the same as above, and Figs. 7 to 18 are diagrams showing the circuit assembled to control either the variable displacement pump or the motor of the circuit shown in Fig. 4. FIG. 3 is a schematic diagram showing various aspects of the electrical/pressure controller. 10...Pump, 12...Motor, 14,16...
・Line, 18...Input shaft, 20...Pump, 28
．． 30... Servo, 38... Storage tank, 42, 44...
・Conduit, 46...controller, 56...controller, 68・
... Spool, 80°82 ... Chamber, 88 ... Variable force valve, 94 ... Electric controller, 96 ... Power source, 106
... Reciprocating valve, 108... Passage, 111... Passage,
132... Orifice, 198... Controller, 200
...adjustment stopper, 202...spring, 204...spool, 206...housing, 208...port, 210...inner L 212...passage, 214...
- Passage, 216... Orifice, 218... Annular groove, 220... Spool, 222... Inner hole, 224...
... No\Using, 226, 228, 230... Port, 232... Hole, 234... Hole, 236... Inner hole, 238... Passage, 239... Passage, 240...
・Valve, 242...Passage, 244...Groove, 246...
・Aisle, 248...Room, 250...Aisle, 252・
...Chamber, 254...Reciprocating valve, 258.260...Line, 262...Motor, 264.266...Servo, 268,270...Conduit, 272.274...
Rand, room 275.

Claims (1)

[Scope of Claims] 1. A controller for a fluid device comprising a fluid device such as a variable fluid pump or motor having a fluid operating member for changing the discharge amount, a pressure fluid source, and a storage tank, comprising: (4) a housing having an internal bore; (B) a first port in the housing in communication with the internal bore and a fluid actuating member; (C) a first port in communication with the internal bore and a source of pressurized fluid; a second port provided in the housing; (0) a third port provided in the housing so as to communicate with the inner hole and the storage tank; (g) a third port provided in the housing so as to communicate with the inner hole and the fluid operating member; a fourth port (Pi) for selectively communicating the respective ports with each other,
a first position communicating the first port with the second port and communicating the third port with the fourth port; a second position in which the fourth port is at substantially the same pressure; and the fourth port is at the second port;
It also has a third position that communicates the first port with the third port, and is configured to move from the first position to the second position to the third position, and from the third position to the second position to the first position. a first resilient valve member biasing said valve member toward a first position;
a biasing member, 0 a member for biasing the valve member toward a third position, the member comprising: a fluid chamber; an inlet passage communicating a source of pressurized fluid with the fluid chamber; Third
a second member including a biasing member biasing the position and a responsive member responsive to the signal to change the pressure of the fluid within the fluid chamber;
A controller comprising: a biasing member; 2 the second biasing member is within the inlet passageway 214 and includes an inlet restriction member 216 that restricts fluid flowing therethrough, and an outlet passageway 250 that moves fluid from the fluid chamber 252 to the reservoir 38.
238, 239, 242, 244, 246 and an outlet restriction member within the outlet passageway for restricting fluid flow therethrough, the signal responsive member including an outlet restriction member for varying the pressure within the fluid chamber 252. 2. The controller according to claim 1, wherein the controller is configured to change the limit amount of the controller. 3. one of the biasing members includes an additional fluid chamber and a member communicating the additional fluid chamber with a source of pressurized fluid; and one of the biasing members biases the valve member to one of the first and third positions in response to fluid pressure within the additional fluid chamber. A controller according to claim 1, comprising a member. 4. The valve member has one land that controls the flow of fluid flowing to or from the first port, and the other land that controls the flow of fluid flowing to or from the fourth port. Claim 1: A spool-type valve having lands, each land being adapted to assume a similar position in the first and fourth ports, respectively, when the valve member is in the second position. Controller as described.