JPS581310B2 - Seisui Atsushiki Dendo Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrostatic transmission device in which the capacity of a fluid can be varied and the rate of variation thereof can be varied.

It is well known in hydrostatic transmission systems to control the pump or motor using various control valve systems.

Control valve systems are described in US Pat. No. 3,129,645 and US Pat. No. 2,891,516.

Neither of these patents contemplates the use of their valve systems in combination with hydrostatic transmissions.

In U.S. Pat. No. 3,129,645, a plurality of single acting solenoids actuate a master control valve that varies the flow of fluid to the motor.

This main valve spool must be moved to vary the operating speed of the fluid motor.

Therefore, this valve device does not change the operating speed of the motor when the main control valve is in a steady state of operation.

Other control valve arrangements are described in U.S. Pat. Nos. 3,589,242, 3,499,284 and 2,307,544.

By the way, these control valve devices have the advantage that fluid control by moving the main valve spool is performed relatively quickly, and therefore capacity control in the pump unit or motor unit can be performed quickly. Because the displacement is so rapid that the variable member moves beyond the predetermined position due to inertia, the flow rate to the unit becomes too much or too little, and the capacity of the unit becomes inaccurate. Since this kind of thing happens, there was a drawback that the exact capacity could not be changed unless this was corrected.

The object of the present invention is to eliminate the drawbacks of the conventional ones as described above, and to provide a hydrostatic transmission device that can quickly and accurately change the capacity.

The above-mentioned purpose is to generate a fluid flow with a large flow rate when the variable capacity is large, and to rapidly displace the variable member.
It is equipped with a control valve device that can reduce the flow rate of the fluid when the fluid becomes small and make the displacement of the variable member gentle, thereby making it possible to accurately stop the variable member and obtain an accurate variable capacity. This can be achieved by providing a pressure transmission, so that the transmission of the invention is as follows.

This invention contemplates the invention of a control device for varying the effective displacement of one or more units of a hydrostatic transmission.

The control device includes two pilot valves and a main control valve that is actuated from a neutral position to one of two operating positions to increase or decrease the capacity of the combination unit.

Each pilot valve can be used to operate a master control valve or vary the flow rate of fluid through the master control valve.

It is desirable to carry out sequential actuation of the pilot valves.

Therefore, the control circuit for operating the pilot valves has a time delay characteristic such that a predetermined time elapses between the start of operation of one pilot valve and the start of operation of the other pilot valve.

Therefore, the object of this invention is to vary the volume of fluid,
It is an object of the present invention to provide a hydrostatic transmission device equipped with a pair of pilot valves that performs the dual function of changing the capacity fluctuation rate.

Another object of the present invention is to provide a hydrostatic transmission device that includes a control circuit that prevents the operation of one pilot valve until a predetermined time has elapsed after the start of operation of the other pilot valve. It is.

A hydrostatic transmission 12 with a control device 10 is shown in FIG. 1 and includes a variable displacement pump 14 having an input shaft 16 driven at a substantially constant speed by a main motor. There is.

To initiate a change in the volume of pump 14, control handle 18 is moved.

When handle 18 is moved, electrical control circuit 20 operates, activating control valve arrangement 22 to direct fluid from pump 24 to actuator 26 .

Actuator 26, when actuated, moves rotary swashplate 28 to vary the displacement of pump 14 and the rate at which fluid is transferred to fixed displacement motor 30, thereby varying the rate at which input shaft 16 is driven by the main motor. The speed of the output shaft 32 that is driven is varied.

Under low load or no-load operating conditions, the transmission 12
The output rate of will vary as a direct function of the change in pump 14 displacement.

One of the features of this invention is that the control valve device 22 is connected to the main control valve 3.
6 (FIG. 2) and two pilot valves 38, 40.

When the first pilot valve 38 operates, the main valve spool 44
to the left (as viewed in FIG. 2) to flow pressurized fluid from input conduit 46 through valve passage 48 and into conduit 50.

Conduit 50 is in flow chamber relationship within actuator 26 with an upper cylinder 54 (FIG. 1) of a first rotating swashplate motor 56 .

Additionally, as a result of the leftward movement of valve spool 44 from the neutral position shown in FIG.
and a drain through a second passageway 68 (FIG. 2) within valve spool 44.

When valve spool 44 is in the left or forward operating position, passageway 68 directs fluid from rotating swashplate motor 62 to passageway 72.
This passageway 72 is connected to a passageway 74 that communicates with a passageway 76 in the valve spool 44 .

Passage 76 is fluidly connected to a flow restriction conduit 80 that is connected to a drain through an orifice 84 .

Orifice 84 is sized so that fluid exits lower piston 60 at a relatively low velocity.

Thus, the rotating swashplate motor 56 accurately positions the rotating swashplate 28 at a relatively low speed in a position corresponding to the desired forward displacement of the pump 14.

When the displacement of pump 14 is varied by a large amount, second pilot valve 40 is actuated after main control valve 36 is moved to the forward actuation position, thereby draining fluid from bypass conduit 88 through valve passage 90. Flow to tube 92.

The resulting flow restriction conduit 80 and bypass conduit 8
The parallel flow of fluid through 8 causes fluid to exit lower piston 60 at a relatively high velocity.

This causes upper swashplate motor 56 to move swashplate 28 at a relatively high speed to increase the displacement of pump 14.

When the displacement of pump 14 approaches the displacement indicated by the position of control handle 18, pilot valve 40 is returned to the inoperative condition shown in FIG.

The fluid therefore flows through flow restriction conduit 80 and orifice 84.
through the chisel to drain, thereby reducing the operating speed of the rotating swashplate motor 56.

The swashplate 28 is thereby precisely moved to a position corresponding to the desired displacement of the pump 14.

When the pump 14 reaches the desired displacement, the first pilot valve 38 is returned to the inoperative state shown in FIG. 2, moving the valve spool 44 from the left position to the neutral position.

When the displacement of pump 14 is to be reduced from the maximum displacement condition shown in FIG. 1, control handle 18 is rotated from a forward operating position shown in solid lines in FIG. 1 toward a neutral position shown in dashed lines.

This actuates control circuit 20 to actuate second pilot valve 40 (FIG. 2) to move valve spool 44 from a neutral position and permit high pressure fluid to flow from pump 24 through valve passage 98 and into conduit 66. Move it to the right working position.

As a result, swash plate 28 is rotated clockwise (as viewed in FIG. 1), reducing the displacement of pump 14.

When the capacity of pump 14 is reduced, fluid flows from upper cylinder 54 through conduit 50 to passage 1 in valve spool 44.
00 (Figure 2).

Fluid from passageway 100 is communicated to passageway 72 which is connected by passageway 104 to passageway 106 in main valve spool 44 .

Passage 106 communicates the exhaust fluid to a flow restriction conduit 108 that is connected to a drain through an orifice 110.

Since this allows fluid to flow from the upper cylinder 54 at a relatively low speed, the rotating swashplate motor 56 is operated at a relatively low speed to facilitate accurate positioning of the rotating swashplate 28.

If the capacity of pump 14 is reduced from a forward operating condition by a relatively large amount, control circuit 20 activates pilot valve 38 to connect bypass conduit 114 to drain through passage 116 within pilot valve 38. .

The resulting parallel flow of fluid through flow restriction conduit 108 and bypass conduit 114 causes fluid to exit upper cylinder 54 at a relatively high rate.

Therefore, lower swashplate motor 62 can move swashplate 28 at a relatively high speed, thereby rapidly reducing the displacement of pump 14.

When the swashplate 14 is moved to a position near the capacity commanded by the control handle 18, the control circuit 20 causes the pilot valve 38 to be in the inoperative position so that the bypass conduit 1
Fluid flow through 14 is blocked.

Thereafter, fluid can be pumped out of the upper cylinder 54 only at relatively low speeds.

Thus, the swashplate motor 62 is operated at a relatively low speed to accurately position the swashplate 28.

Once the swashplate 28 is moved to a position corresponding to the desired displacement, the control circuit 20 actuates the pilot valve 40 to move the valve spool 44 to the neutral position.

The valve spool 44 is held in a neutral position by fluid pressure within a pair of pressure chambers 120, 122 located at opposite ends of the main valve spool 44.

Chamber 120122 is in communication with pump 24 through a pair of conduits 124,126.

When the valve spool 44 is in the neutral position, the pair of valve spool passages 128, 130 connect the chambers 120, 122 in fluid communication with the flow restriction passages 108, 80.

Flow restrictors 134, 136 in conduits 124, 126 connect chambers 120, 12 to maintain valve spool 44 in a neutral position.
dimensioned to provide equal pressure within 2.

Because flow restrictors 110, 84 are made significantly smaller than flow restrictors 134, 136, when pilot valves 38, 40 are inactive and valve spool 44 is in the neutral position, fluid Pressure is maintained within chambers 120,122.

With valve spool 44 in the neutral position, when pilot valve 38 is actuated, chamber 120 is connected to a drain through bypass passage 114 and pilot valve spool passage 116.

As this reduces the fluid pressure within chamber 120, the relatively high pressure within chamber 122 causes valve spool 44 to move to the left actuated position.

Once the valve spool 44 has been moved to the left, the chamber 120 is in fluid communication with the bypass conduit 114 through the valve spool passage 140.

To move valve spool 44 back to the neutral position, pilot valve 38 is actuated to block fluid flow through bypass conduit 114.

Because flow restrictor 110 is made relatively compact, fluid pressure is rapidly regenerated within chamber 120.

The valve spool 44 is therefore moved to the right under the combined action of the pressure within the chamber 120 and the biasing spring 144.

Right bias spring 1 when valve spool 44 is in left position
46 is in the released state, when the pilot valve 38 moves to return to the neutral position, the compressed bias spring 1
The combined force of 44 and the fluid pressure in chamber 120 overcomes the fluid pressure in chamber 122.

When the valve spool 44 is moved from the neutral position to the right operating position, the pilot valve 40 is actuated to direct fluid into the pressure chamber 1.
22 through bypass conduit 88 and valve passage 90 to drain.

As a result of this, the fluid pressure within chamber 122 decreases, so that chamber 122
2 causes biasing spring 146 and chamber 1
The valve spool 44 moves to the right against the combined effect of the relatively low fluid pressure in the valve spool 22.

When the valve spool 44 is moved to the right operating position, the valve spool passage 150 maintains the pressure chamber 122 in fluid communication with the activated pilot valve 40, thereby reducing the fluid pressure within the chamber 122 to the pressure within the chamber 120. Maintain a relatively low pressure compared to the

When valve spool 44 is moved to the left from the right operative condition, pilot valve 40 is returned to the inoperative condition shown in FIG. 2 to prevent fluid flow through bypass conduit 88.

As a result, fluid pressure within chamber 122 increases rapidly.

When this condition occurs, valve spool 44 is moved to the left under the combined force of this pressure in chamber 122 and biasing spring 146.

When the output shaft 32 is driven in the reverse direction, the swash plate 28 moves from the maximum forward excursion position shown in FIG. It is rotated clockwise through the deflection position and into the reverse operating position.

This rotation of the rotating swashplate 28 reverses the flow of fluid to the motor 30, thereby reversing the direction of the transmission 12.

To move the swashplate 28 to the reverse operating position, the pilot valve 40 is actuated to move the valve spool 44 to the right operating position.

This causes pressurized fluid to flow through valve passage 98 to conduit 66 to lower swashplate motor 62, thereby rotating swashplate 28 in a direction that reduces the forward excursion of pump 14.

When the reverse operating speed of transmission 12 is reduced, pilot valve 38 is actuated to move control valve 44 to the left operating position and direct high pressure fluid from pump 24 through valve passage 48 to upper servo motor 56 . Distribution to 50.

When valve spool 44 is in either actuated position, inactive pilot valve 38 or 40 can be actuated to increase the rate at which the displacement of pump 14 is varied.

Manual override buttons 147 and 149 are connected to valve spool 4
Connected to both ends of 4.

If pilot valve 38,40 is inoperative due to a power failure, one of buttons 147 or 149 can be actuated to move valve spool 44 to either operating position.

If fill pump 24 is unable to supply fluid to main control valve 36, safety control valve 151 is activated to fluidly interconnect conduits 50.66 leading to rotating swashplate motors 56, 62.

When this fluid connection is made, springs 153, 155 in motors 56, 62 act to move swashplate 28 to a neutral position.

Valve 151 connects chamber 159 from conduit 46 through conduit 161.
It has a spool 157 which is held in the position shown in FIG. 2 under the action of pressure introduced therein.

When the spool 157 is in the position shown in FIG. 2, the spool 157 blocks fluid flow through the pair of conduits 163,165.

As the fluid pressure in chamber 159 decreases, the relatively higher fluid pressure in pressure chambers 167 or 169 acts to move spool 157 downwardly, so that fluid conduits 163 and 165 are brought into communication with each other through valve passage 171. Become.

Fluid conduits 163, 165 are connected to conduits 50.66 so that cylinders 54.6 of rotating swash plate motors 56, 62.
The fluid pressure within 60 is equalized so that biasing spring 15
3,155 can return the rotating swash plate 28 to the neutral position.

When swashplate 28 is in a position other than the neutral position, only one of lines 163 or 165 is pressurized, the other containing fluid at a relatively low pressure.

When the swash plate 28 is at maximum capacity, the conduits 50,
163, relatively high pressure fluid is present within the pressure chamber 167.

Further, relatively low pressure fluid exists within the conduits 66, 165 and the pressure chamber 169.

Chamber 159 has an effective area twice that of either pressure chamber 167 or 169.

The fluid pressure in chamber 159 therefore overcomes the fluid pressure in chamber 167 when pump 24 is activated to provide high pressure fluid to control valve 36.

If pump 24 fails with swash plate 28 in its maximum displacement position and control valve 36 in its neutral position, a decrease in output pressure from pump 24 will be transmitted to chamber 159.

The pressure in chamber 167 therefore causes valve spool 157 to move.

When valve 151 is actuated, relatively high fluid pressure within cylinder 54 is placed in fluid communication with cylinder 60 .

As a result, motor 62 operates under the influence of increased fluid pressure within cylinder 60 and spring 155 to rotate swashplate 28 clockwise to a neutral position.

Control circuit 20 is shown in FIG. 3 and includes a command circuit 160 that generates a command signal representative of the set displacement of pump 14.

This command signal is transmitted to a connection point 162 connected to a position feedback circuit 164.

Feedback circuit 164 generates a feedback signal representative of the actual displacement of pump 14.

If the set displacement of pump 14 differs from its actual displacement, an error signal is communicated via conduit 166 to valve actuation circuit 170.

Actuation circuit 170 includes a first
It includes a solenoid 174, a second solenoid 176 that actuates the pilot valve 40, and a main control circuit 180 that energizes one of the pilot valve solenoid coils 174 or 176 in response to an error signal.

When coil 174 or 176 is energized, control valve 36
to the left actuating state or the right actuating state and actuator 2
6 to change the capacity of the pump 14 in accordance with the capacity indicated by the command signal.

If there is a relatively large difference between the command signal and the feedback signal, the speed control circuit 182
The second one of 8 or 40 is actuated to operate the actuator 26 at a relatively high speed.

A delay circuit 183 in the speed control circuit 182 provides a predetermined time between when the main control circuit 180 starts operating one of the pilot valves 38 or 40 and when the speed control circuit 182 starts operating the other pilot valve. Provide spacing.

When pump 14 is in a neutral state, working surface 154 of rotating swash plate 28 is perpendicular to the central axis of input shaft 16 .

If control handle 18 is in the neutral position, input lead 1
84 and 186 are connected to the same potential.

This is because the wiper 188 coupled to the handle 18 is in a neutral position.

If conductors 184, 186 were to break, the command signal would appear as a neutral signal since the same potential would be applied to both conductors.

The reference potential from the voltage divider 190 is applied to the amplifier 19 via a resistor.
Applies to the positive terminal of 2.

The negative feedback of amplifier 192 causes a signal with a potential equal to the reference potential to be transmitted via conductor 194 to node 162.

Feedback circuit 164 includes a potentiometer 196 having a pointer 198 coupled to rotating swashplate 28 .

Pointer 198 moves relative to coil 200 to generate a feedback signal that varies as a function of the position of rotating swashplate 28.

This feedback signal represents the actual displacement of pump 14.

Neutral adjustment potentiometer 208 is combined with feedback potentiometer 196 to adjust pump rotation swash plate 2.
When 8 is in the neutral position, the potential of the position feedback signal can be adjusted to a potential equal to the reference potential.

When control handle 18 and swashplate 28 are in their neutral positions, the error signal communicated to valve actuation circuit 170 has a potential equal to the reference potential.

This is because the reference potential command signal and the reference potential feedback signal are communicated from connection point 162 to the negative terminal of amplifier 212.

A positive terminal of amplifier 212 is connected to a reference potential.

Due to negative feedback, the error signal from amplifier 212 has a potential equal to the reference potential.

An error signal with a reference potential is applied to the negative terminal of amplifier 216.

An input potential ■1 higher than the reference potential is applied from the voltage divider 190 to the positive terminal of the amplifier 216.

Amplifier 216 will have a high potential output that cannot be passed through reverse polarity diode 218 to amplifier 220.

Similarly, a potential 2 below the reference potential is applied to the negative terminal of the amplifier 224.

A reference potential error signal applied to the positive terminal of amplifier 224 causes amplifier 224 to have a relatively high potential output signal.

The reverse polarity diode 228 connects this output signal to the amplifier 230.
prevent it from being passed on.

A signal 3 having a relatively high potential higher than the potential of the reference signal is applied to the positive terminal of the amplifier 234.

Therefore, a relatively high potential signal is transmitted to the positive terminal of amplifier 230 via conductor 236.

This causes the amplifier 230 to
Since the output potential is greater than the zero emitter potential, the coil 176 is maintained in a demagnetized state.

Similarly, since a relatively low potential 4 is applied to the negative terminal of the amplifier 242, a relatively high potential signal is applied to the conductor 242.
4 to the positive terminal of the amplifier 220.

Since a relatively low potential 5 is applied to the negative terminal of amplifier 220, amplifier 220 has an output signal above the potential of the emitter of PNP transistor 248.

Coil 174 is therefore maintained in a demagnetized state.

Since the coils 174 and 176 are demagnetized, the pilot valves 38 and 40 remain in the inoperative condition shown in FIG. It is maintained.

To increase the forward output speed of transmission 12, move handle 18 counterclockwise from the neutral position.

This moves the wiper 188 upwards and
A high potential command signal higher than the reference potential is applied to 84.

This high potential command signal is conveyed to the negative terminal of amplifier 192 so that amplifier 192 has a low potential output signal that is lower than the reference potential conveyed to node 162 via conductor 194.

At the same time, the low potential output signal from amplifier 192 is transferred to conductor 25.
4 to the negative terminal of high gain amplifier 256, and amplifier 256 quickly becomes saturated.

Prior to saturation, amplifier 256 provides a dead band with an output signal that opposes the output signal of amplifier 192, so command circuit 160 does not respond to relatively small changes in the command signal.

When a substantial change in the command signal occurs, the low potential output signal conveyed from amplifier 192 to connection point 162 is transferred to amplifier 21.
One low potential output signal is transmitted to the negative terminal of No. 2.

The resulting high potential error signal higher than the reference potential is transmitted to the negative terminal of the amplifier 216.

The resulting low potential output signal from amplifier 216 is transmitted through diode 218 to the positive terminal of amplifier 220.

As a result, the output potential of the amplifier 220 becomes lower than the emitter potential of the PNP transistor 248, making the second PNP transistor 269 conductive and exciting the solenoid coil 174.

When coil 174 is energized, pilot valve 38 is actuated to move control valve 36 to the left operating position.

If the control lever 18 is moved a relatively small distance so that the command signal corresponds to a relatively small variation in the displacement of the pump 14, the high potential error signal will cause the amplifier 2
The potential applied to the positive terminal of 34 has a lower potential than 3.

Therefore, amplifier 234 continues to have an output potential that is substantially higher than the low potential 5 applied to the negative terminal of amplifier 230.

The output amplifier 230 continues to apply a higher potential to the base than the emitter potential of the PNP transistor 240 and
76 maintains the demagnetized state.

If handle 18 is moved such that a relatively large high potential error signal is applied to the negative terminal of amplifier 234, the resulting low potential output signal from amplifier 234 is routed through conductor 236. is communicated to connection point 264.

If the signal transmitted from delay circuit 183 to connection point 264 is at a relatively low potential compared to the reference potential, amplifier 230 applies a relatively low potential to the base of PNP transistor 240 .

Coil 176 will therefore be energized at the same time as coil 174 is energized.

This causes control valve 36 to operate erratically, since both pressure chambers 120, 122 are in communication with the drain through bypass conduits 114, 88, respectively.

To provide sequential operation of pilot valves 38.40,
Delay circuit 183 operates to transmit a relatively high level signal to connection point 264 for a predetermined period of time after excitation of coil 174 begins.

The low potential output signal from amplifier 216 is transmitted through reverse polarity diode 270 to the negative terminal of amplifier 274 in delay circuit 183 .

This produces a high potential output signal from amplifier 274 for a time sufficient to charge capacitor 276.

The output signal from amplifier 274 is shown schematically in FIG.

After sufficient time has elapsed to finish charging capacitor 276, the output signal from amplifier 274 is reduced in potential by having a very low potential applied to its positive terminal.

As a result, a low potential output signal is communicated to connection point 264.

The low potential output signal from amplifier 274 is combined with the low level signal from amplifier 234 at node 264.

The resulting signal is applied to the positive terminal of output amplifier 230.

After sufficient time has elapsed to charge capacitor 276,
Amplifier 230 has a low potential output voltage that causes transistor 240 to conduct, thereby causing second transistor 2
80 is made conductive and the coil 176 is energized.

As a result, the pilot valve 40 is activated after a predetermined period of time has elapsed since the pilot valve 38 was activated.

When the capacity of the pump 14 is very close to the capacity corresponding to the command signal, the error signal has a potential lower than potential 3,
Amplifier 234 also has a high potential output signal.

As a result, the signal from amplifier 230 changes from a potential lower than the potential of the emitter of PNP transistor 240 to a potential higher than the potential of the emitter of transistor 240.

The coil 176 is thereby demagnetized and the return spring 28
4 (see FIG. 2) returns pilot valve 40 to an inoperative state to prevent fluid from passing through bypass conduit 88.

When the rotating swash plate 28 moves to a position corresponding to the capacity indicated by the command signal, the potential of the error signal transmitted to the amplifier 216 decreases to below the potential ■1, so the high potential output signal increases. It is transmitted from the width container 216.

As a result, the relatively low potential 5 applied to the negative terminal of amplifier 220 causes amplifier 220 to generate a high potential output signal to PNP transistor 248.

This demagnetizes the coil 174 and returns the pilot valve 38 from the activated state to the inactive state under the action of the biasing spring 288.

Immediately after this, the control valve spool 44 returns to the neutral position, resting the swash plate 28 in a position where the pump 14 has a capacity corresponding to the position of the lever 18.

If the forward working capacity of pump 14 is to be reduced, lever 18 is moved clockwise toward a neutral position.

This causes wiper 188 to move downwardly, reducing the potential of the command signal applied to conductor 184 and increasing amplifier 192.
Decrease the potential applied to the negative terminal of.

If the movement of the lever 18 corresponds to a change larger than the dead band, the amplifier 256 will quickly become saturated, so that the resulting increased signal from the amplifier 192 will be reduced by one increased signal to the amplifier 256. Apply to the negative terminal of 212.

The resulting low potential error signal is conveyed to the positive terminal of amplifier 224.

The low potential output signal from amplifier 224 is connected to diode 228.
The signal is transmitted to the positive terminal of amplifier 230 via .

As a result, the output potential of amplifier 230 is changed to
40 becomes smaller than the potential at the emitter of transistor 240, causing transistor 240 to conduct and energizing coil 176.

If a large change in the displacement of pump 14 is applied, pilot valve 38 is actuated to increase the rate of fluid flow to motor 62.

The low potential error signal is also routed to connection point 2 by conductor 244.
The signal is transmitted to the positive terminal of the amplifier 242 connected to the amplifier 90.

To provide a time delay between the actuation of pilot valve 40 and pilot valve 38, delay circuit 183 conveys a relatively high level signal to connection point 290 so that the output signal from amplifier 220 is , remains at a potential higher than the potential of the emitter of the PNP transistor 248 until a predetermined time has elapsed.

Thereafter, the potential of the high-potential output signal from the delay circuit 183 decreases, and the output of the amplifier 220 is transferred to the transistor 24.
The potential is reduced to a lower potential than that of 8.

This causes the coil 174 to be energized.

To provide a time delay, the low potential output signal from amplifier 224 is communicated via conductor 294 to a reverse polarity diode 296 connected to the negative terminal of amplifier 274.

This transmits a high potential output signal from amplifier 274 to connection point 290 .

After capacitor 276 is charged, the output signal from amplifier 274 is switched to a low potential output signal;
A relatively low potential is transmitted from amplifier 274 to connection point 290 .

This causes the output of amplifier 220 to be transferred to transistor 248.
is changed to a potential lower than that of the emitter of , thereby energizing coil 174 and actuating pilot valve 38 to increase the rate at which fluid flows to motor 62 .

Once the capacity of the pump 14 is reduced to a capacity very close to the set capacity represented by the command signal, the potential of the error signal is higher than the level of the potential 4 applied to the negative terminal of the amplifier 242. level will be increased.

This conveys a high potential output signal from amplifier 242 to connection point 290 .

The output of amplifier 220 then changes to a potential higher than the potential of the emitter of transistor 248, demagnetizing coil 174.

In this state, the pilot valve 38 is returned to its non-operating state.

Fluid is then communicated between control valve 36 and actuator 26 at a relatively low velocity to accurately position rotating swashplate 28 at a volume corresponding to the position of handle 18.

When the swash plate 28 is moved to a position where the pump 14 has a capacity corresponding to the capacity represented by the command signal,
The feedback and command signals correspond to this capacitance and no error signal is generated that would cause amplifier 224 to have a low potential output signal.

As a result, the relatively high potential output from amplifier 224 is blocked by diode 228, and amplifier 230 is turned into a relatively high potential output.

Therefore, transistor 240 is disconnected, and coil 17
6 is demagnetized and the return spring 284 returns the pilot valve 40 to its inoperative state.

Main control valve spool 44 is then moved to the neutral position.

When output shaft 32 is driven in the reverse direction, control circuit 20 operates control valve 22 in a manner very similar to that described for forward operation.

However, if the output speed is increased in the opposite direction, conductor 184
The potential of the command signal applied to conductor 186 is reduced to a lower level than the potential applied to conductor 186.

The obtained low potential error signal is sent to the amplifier 2 via the conductor 166.
It is transmitted to the positive terminal of 24.

The output signal from amplifier 230 will be lower than the potential at the emitter of transistor 240, energizing coil 176.

Since the low potential output signal from amplifier 224 is passed to delay circuit 183, amplifier 274 has a relatively high output potential while capacitor 276 is being charged.

Therefore, if a relatively large change is applied to the reverse actuation speed, the coil 174 will be energized a predetermined time after the energization of the coil 176, thereby sequentially actuating the pilot valves 38, 40 in the manner previously described. will be implemented.

When the displacement of pump 14 is reduced during reverse operation of the hydrostatic transmission, handle 18 is moved toward the neutral position, thereby increasing the potential of the command signal applied to conductor 184.

As a result, a high potential error signal is transmitted from amplifier 212 to the negative terminal of amplifier 216.

The resulting energization of coil 174 activates pyrosoto valve 38 to move control valve 36 to the left operating state, and activates motor 56 to rotate swash plate 28 counterclockwise to reverse pump 14. Reduces directional effective actuation capacity.

If a relatively large reduction is implemented in the reverse operating capacity, delay circuit 183 prevents energization of coil 176 until a predetermined time has elapsed after coil 174 has been energized.

After this predetermined time has elapsed, the amplifier 274
The low potential signal conveyed to the negative terminal of causes a low potential output signal to be conveyed to node 264 and amplifier 230 causes transistor 240 to conduct.

This causes the coil 176 to be energized and the actuator 26 to operate at high speed.

The operating conditions necessary to effectuate the energization of coils 174, 176 are represented by negative logic pool algebraic expressions in FIG.

Therefore, in order to apply a relatively low potential output signal D to the amplifier 220 and make the PNP transistor 248 conductive,
Either the A signal carried from the amplifier 216 to the positive terminal of the amplifier 220 has a relatively low potential, or the B', C signals carried from the amplifiers 274, 242 to the connection point 290 have a relatively low potential. It is necessary to have

Similarly, in order to cause amplifier 230 to have a relatively low potential output signal E to conduct transistor 240 and energize coil 176, a comparison signal is transmitted from amplifier 224 to the positive terminal of amplifier 230. A relatively low potential signal O from amplifier 274 to node 264 and a relatively low potential signal O from amplifier 234 to node 2.
It is necessary to have a relatively low potential signal A' transmitted to 64.

In the embodiment shown in FIG. 4, both pump 14a and motor 30a are of the variable displacement type.

Since the embodiment shown in FIG. 4 has many components that are the same as those of the embodiment shown in FIGS. Add a subscript a to this number to avoid this.

In the embodiment shown in FIG. 4, movement of handle 13a activates control circuit 20a to actuate control valve 22a and pump 14a in a manner similar to that previously described for the embodiment shown in FIGS. 1-3. Vary.

A feature of the embodiment shown in FIG. 4 is that a large amount of handle 18a must be actuated to change the output speed;
Simply changing the capacity of the pump 14a does not provide a desired change in output speed.

In this state, the control circuit 310 operates to operate the main control valve device 312, and the pump 24a is activated by the actuator device 31.
4 to operate the swash plate 316 of the pump 30a between a maximum displacement condition (as shown in FIG. 4) and a minimum displacement condition.

If the displacement of motor 30a is varied by a relatively large amount, control circuit 310 operates control valve 312 to increase the velocity of fluid delivered to actuator 314, thereby causing swashplate 316 to change to the desired displacement. Increase the speed at which you are moved towards a state.

When the swashplate 316 approaches the desired volume, the control circuit 310 actuates the control valve 312 so that fluid flows into the actuator 31.
4, thereby reducing the speed sent to rotating swash plate 31.
6 more slowly and precisely to the desired volume position.

Control valve 312 has the same structure as control valve 22.

Control valve 312 includes a main control valve having the same structure as control valve 36 .

The main control valve of control valve 312 includes a valve spool that corresponds to valve spool 44 , which is moved from a neutral position to a left actuated position during actuation of a first pilot valve that corresponds to pilot valve 40 . When the second pilot valve corresponding to the second pilot valve is activated, the neutral position is shifted to the right operating position.

The interaction between the main control valve and the two pilot valves of control valve 312 in actuator 314 is similar to that of control valve 36 and pilot valve 38 . of actuator 26 in the embodiment shown in FIGS.
40.

Therefore, no further description of the structure and interaction of these components will be provided.

Although pump actuator 26a and motor actuator 314 can be constructed in a variety of different ways, these actuators are constructed in a manner substantially similar to that described in U.S. Pat. No. 3,795,109. Ru.

Motor displacement control circuit 310 is substantially similar to control circuit 20 of the embodiment of FIGS. 1-3.

Therefore, the motor capacity control circuit 310 receives the command signal from the same input as the control circuit 20a, and the main circuit 320 (fifth
(Figure) included.

The command signals applied to leads 326, 328 of command circuit 320 are the same as the command signals applied to the input leads of pump control circuit 22a, and also represent the set displacement of motor 30a.

During relatively low speed operation, the set displacement of the motor 30a remains substantially constant at its maximum displacement condition, and the output speed of the hydrostatic transmission is varied by varying the displacement of the pump 14a in the manner described above. There will be.

Position feedback circuit 332 is connected to command circuit 320 and includes a potentiometer 334 having a pointer 336 coupled to rotating swash plate 316 of motor 30a.

Pointer 336 cooperates with resistor 338 to provide a feedback signal that varies as a function of the capacity of motor 30a.

A sequencing potentiometer 342 is connected to position feedback potentiometer 334 .

Sequence potentiometer 342 is adjusted so that pump 14a and motor 30a operate in sequence.

By properly adjusting potentiometer 342, motor displacement control circuit 310 activates control valve 312 to increase the displacement of motor 30a when pump 14a has been actuated a predetermined displacement in either direction. Decrease.

In addition to the command circuit 320 and the position feedback circuit 332, the motor displacement control circuit 310 provides a control circuit between the set motor displacement represented by the command signal and the actual motor displacement represented by the signal from the feedback control circuit 332. Valve actuation circuit 34 energizes pilot valve solenoid coils 348, 350 when there is a difference.
Contains 6.

The coil 348 is connected to the control valve 3 corresponding to the pilot valve 38.
It is connected to the pilot valve in 12.

Similarly, coil 350 is connected to a pilot valve within control valve 312 that corresponds to pilot valve 40.

When coil 348 is energized, the pilot valve is actuated to actuate the main control valve within control valve 312 and direct high pressure fluid through conduit 351 to cylinder 354 of upper rotating swashplate motor 356 .

Similarly, energization of coil 350 actuates a master control valve within control valve 312 to flow high pressure fluid through conduit 352 to cylinder 360 of rotating swashplate motor 362 .

The main control circuit 370 energizes the coil 350 to operate the main control valve in the control valve 312 when the capacity represented by the command signal is smaller than the actual capacity represented by the feedback signal from the feedback signal circuit 332. Reduce the capacity of pump 30a.

Similarly, if motor swashplate 316 is in a position other than the maximum capacity state and the command signal represents a motor displacement greater than the actual motor displacement represented by the feedback signal from circuit 332, main control circuit 37
0 excites the coil 348 and operates the main control valve, causing fluid to flow to the rotating swash plate motor 356 and causing the motor rotating swash plate 31 to flow.
6 to the maximum capacity state.

A speed control circuit 374 is connected to the main control circuit 370 and energizes the coil 350 when the capacity of the pump 30a is reduced by a relatively large amount.

When the coil 350 is energized, it actuates the pilot valve corresponding to the pilot valve 40, causing the control valve 312 and the actuator 3 to operate.
14.

When coil 348 is energized, it actuates a pilot valve to open a bypass passage so that fluid can be expelled from cylinder 354 at a relatively high rate.

Similarly, when the capacity of pump 30a is increased by a significant amount, coil 350 is energized to increase the velocity of fluid pumped between control valve 312 and actuator 314.

When coil 350 is energized, a pilot valve corresponding to pilot valve 38 can be actuated to open a bypass passage and allow fluid to exit cylinder 360 at a relatively high rate.

Delay circuit 378 cooperates with main control circuit 370 and speed control circuit 374 to effect sequential actuation of the pilot valves of control valve arrangement 312 in the same manner as previously described for the embodiment shown in FIGS. 1-3. .

Therefore, when the capacity of the motor 30a is rapidly reduced, the coil 348 is energized after a predetermined time has elapsed since the coil 350 was energized.

Similarly, when the capacity of motor 30a is rapidly increased, coil 350 is energized a predetermined time after coil 348 is energized.

The manner in which valve actuation circuit 346 cooperates with coils 348, 350 is similar to that previously described with respect to the embodiment shown in FIGS. 1-3 and will not be described in detail.

However, the pooling algebra shown in FIG. 5 is in negative logic form, meaning that whenever low potential signal A or low potential signals C, B' are present, a low potential signal D is provided which energizes coil 348. You should be careful.

Similarly, whenever low potential signal B or low potential signal C, A' is present, low potential signal E energizes coil 350.
exists.

Unlike the command circuit 160, the command circuit 320 is different from the command circuit 160.
A relatively high potential error signal is provided on conductor 384 whenever 8a is placed in the neutral position.

This high potential error signal is communicated to valve actuation circuit 346 to maintain coil 348 energized so that the main control valve of control valve 312 remains actuated to the left, directing high pressure fluid through conduit 351 to the rotating swashplate. Cylinder 354 of motor 356
be distributed to.

This high-pressure fluid acts as a bias force and pushes the rotating swash plate 316.
to maintain maximum capacity position.

When lever 18a is in the neutral position, conduits 326, 32
The same potential is applied to 8.

The positive terminal of amplifier 390 is grounded.

Therefore, amplifier 390 is biased to the saturation point and
It has a low potential output delivered to connection point 392.

Since the positive terminal of amplifier 396 is also grounded, control lever 18a is in the neutral position and conductor 326
, 328 is grounded, amplifier 396 is biased to its saturation point and has a low potential output signal, which is also passed to node 392.

When swashplate 316 is in its maximum capacity state, feedback position potentiometer 334 is in the state shown in FIG. 5 and has a relatively high potential output signal communicated to node 392.

Because of the low potential signals from saturated amplifiers 390, 396, the potential applied from connection point 392 to the negative terminal of amplifier 400 is lower than the reference potential applied to the positive terminal of amplifier 400. It's on the level.

Therefore, amplifier 400 has a relatively high potential output signal when control lever 18a is in the neutral position.

This high potential output signal is transmitted to the negative terminal of amplifier 404 to provide a relatively low potential at the output of amplifier 404, and this low potential is transmitted to the positive terminal of amplifier 406 to cause transistor 408 to conduct. to energize the coil 348.

When coil 348 is energized, control valve 312 is actuated to direct fluid from pump 24a to conduit 351 to maintain rotating swashplate 316 in the maximum capacity position.

When the forward output speed of transmission 12a is increased by a relatively large amount, control handle 18a is moved such that the electrical potential applied to lead 326 is increased by a relatively large amount.

The resulting high potential output signal is transmitted to the negative terminal of amplifier 390 to further saturate the amplifier.

This high potential output signal is also applied to the positive terminal of amplifier 396 to saturate the amplifier, so that one high potential output signal is communicated from amplifier 396 to node 392.

As a result, a low potential error signal is transmitted to the negative terminal of amplifier 404 to demagnetize coil 348.

As a result, the pilot valve is actuated and the main valve spool is moved toward the neutral position.

The low potential error signal is also communicated to the positive terminal of amplifier 410 to energize pilot valve solenoid coil 350.

This causes the main valve spool to move and direct pressurized fluid into conduit 352 leading to motor 362 .

If the error signal is of a sufficiently low potential, amplifier 414 in speed control circuit 374 transfers the low potential signal to node 41.
Tell 8.

After sufficient time has elapsed to charge capacitor 420, the low potential output signal from amplifier 422 is also communicated to node 418, energizing coil 348 and causing control valve 3
12 to the motor 362.

When the rotary swashplate 316 approaches a position corresponding to the set operating position, this relatively resistive error signal will exceed the bias voltage applied to the negative terminal of the amplifier 414.
I can't overcome the influence of 4.

Coil 348 is thus demagnetized and fluid is routed from main valve 312 to motor 362 at a relatively low rate.

When the feedback signal from circuit 332 corresponds to the command signal, the output from amplifier 400 is output from amplifier 410.
The potential 2 applied to the negative terminal of will be increased to a potential that will demagnetize the coil 350.

Once this condition is reached, the second pilot valve is closed and the main valve spool is moved to its neutral position to hydraulically lock the motor 316 from further operation.

When the operating speed of motor 30a is reduced, conductor 32
The potential applied to 6 decreases.

The resulting low potential command signal reduces the potential of the output signal from amplifier 396, thereby increasing the potential of the error signal conveyed from amplifier 400.

This high potential error signal is communicated to the negative terminal of amplifier 404 to move the main valve spool of valve 312 to direct fluid to motor 356 and increase the capacity of motor 30a.

If there is a relatively large change in the capacity of motor 30a, the relatively high potential error signal voltage applied to the negative terminal of amplifier 428 will cause capacitor 420 to charge and coil 348 to be energized. It is of sufficient size to energize coil 350 after a predetermined period of time.

Of course, when 350 is energized, the pilot valve is actuated to increase the rate of flow between valve 312 and actuator 314.

When motor 30a is at maximum capacity and pump 14a is operated in the reverse direction, control handle 18a can be moved over a relatively large distance and conductor 326
greatly increases the absolute value of the negative voltage applied to the

This low potential command signal is transmitted to the positive terminal of amplifier 396 to drive the amplifier further into saturation.

The low potential command signal is also conveyed to the negative terminal of amplifier 390 so that the amplifier is saturated and applies a high potential output signal to node 392 and the negative terminal of amplifier 400.

The resulting low potential error signal is transmitted to coils 348 and 35.
0 is demagnetized to shift the main valve spool and flow high pressure fluid to the motor 362 in a manner similar to that previously described.

If a relatively large increase is to be applied to the reverse speed, coil 348 is re-energized after a predetermined period of time and actuator 314 is re-energized in the same manner as previously described.
Implement high-speed operation.

When the swashplate 316 of the motor 30a is moved to a position very close to the set position, the potential of the error signal is increased enough to demagnetize the coil 348.

When the rotating swash plate 316 is accurately positioned at the position corresponding to the set capacity, the coil 350 is demagnetized and the control valve 3
12 to lock the rotating swash plate 316 in place.

When the reverse operating speed of transmission station 12a is reduced and rotating swashplate 316 is in a position other than the maximum capacity position, the resulting decrease in the absolute value of the negative voltage applied to conductor 326 is reduced by amplifier 390. is transmitted to the change in the error signal and the change in the coil 3
48 is applied to move the main valve spool to flow pressurized fluid to the motor 356.

If a relatively large reduction is applied to the reverse speed of the transmission, after a predetermined period of time, coil 350 is re-energized to increase the rate at which fluid is pumped to motor 356.

The present invention is as described above, in which the pump unit and the motor unit are fluidly connected, and the actual fluid capacity of one of the units and the set fluid capacity are extracted using separate signals and compared. , means are provided for controlling the actuating device to cause the fluid to flow at a high speed if the difference is greater than a predetermined value, and to flow the fluid at a lower speed if the difference is smaller than a predetermined value;
Since this actuating device is designed to vary the fluid capacity of one unit, the actuating device for the unit is designed to quickly bring them closer together while the difference in both capacities is large, and to slowly bring them closer together when the difference becomes smaller. operation is carried out, so that when the difference between the two capacities disappears, the operation of the unit is precisely stopped and the capacity in the unit corresponds to that precisely determined, during which operation of the unit is rapid. There is an effect.

Furthermore, in order to quickly and accurately change the capacity of the unit as described above, the present invention comprises a main control valve and a pair of pilot valves disposed in the same fluid system, and the cooperation of both pilot valves with respect to the main control valve is provided. Since it is controlled by actuation, there is no need for different pressure sources for each valve, and the configuration is extremely simple if the control can be achieved simply by devising the piping. It also has economical effects.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the hydrostatic transmission device of the present invention equipped with a control device, FIG. 2 is a schematic diagram of the control valve device shown in FIG. 1, and FIG. 3 is a schematic diagram of the electric control circuit shown in FIG. 1. 4 is a schematic diagram of a hydrostatic transmission device according to a first embodiment of the invention, which is equipped with a control device for varying the capacities of a pump unit and a motor unit, and FIG. 5 is a schematic diagram of a hydrostatic transmission device shown in FIG. It is a diagram of a control circuit. 10... Control device, 12, 12a...
Hydrostatic transmission device, 14, 14a...pump,
16.16a... Input shaft, 18.18a...
...Control handle, 20,20a...Electric control circuit, 22.22a...Control valve device, 24,
24a...Pump, 26, 26a...
Actuator, 28.28a...Rotary swash plate, 30,3
0a...Motor, 32.32a...Output shaft, 36...Main control valve, 38, 40...
...Pilot valve, 44...Main valve spool, 4
6.46a... Input conduit, 50.50a, 66
, 66a... conduit, 54.54a...
Upper cylinder, 56.56a, 62.62a...
- Rotating swash plate motor, 60.60a... lower cylinder, 80, 108... flow rate restriction conduit, 84,
110... Orifice, 88, 114...
... Bypass conduit, 92 ... Drain conduit, 12
0122...pressure chamber, 124,126...
... Conduit, 134,136 ... Orifice, 1
44,146... biasing spring, 147,149.
...Manual override button, 151...
・Safety control valve, 153, 155...Spring, 15
4...Rotary swash plate action surface, 160...Command circuit, 164...Feedback circuit, 17
0... Valve operation circuit, 174, 176...
・Solenoid coil, 180... Main control circuit,
182... Speed control circuit, 183...
Delay circuit, 190... Voltage divider, 196...
...Feedback potentiometer, 208...
・Potentiometer for neutral adjustment, 248, 288...
... Spring, 310 ... Control circuit, 312.
... Main control valve device, 314 ... Actuator,
316... Rotating swash plate, 320... Command circuit, 332... Feedback circuit, 334
...Feedback potentiometer, 342
...Sequence adjustment potentiometer, 346...
... Valve actuation circuit, 348, 350 ... Solenoid coil, 351, 352 ... Conduit, 354
, 360... cylinder, 356, 362...
... Rotating swash plate motor, 370 ... Main control circuit, 374 ... Speed control circuit, 378 ...
・Delay circuit.

Claims (1)

[Scope of Claims] 1. A pump unit that converts mechanical power into hydrostatic pressure, a motor unit that is fluidly connected to the pump unit and converts the hydrostatic pressure into mechanical power, and one of the pump unit and the motor unit. an actuator for varying the fluid capacity of the unit; and first means for generating a first electrical signal representative of the actual fluid capacity of the one unit;
a second means for generating a second electrical signal representing a set fluid capacity of the one unit; and comparing the first and second electrical signals to determine the actual fluid capacity of the one unit and the set fluid capacity. third means for generating an electrical output signal indicating whether the capacitances differ and whether the difference is greater than a predetermined amount; actuating the actuating device at a first speed when the fluid volume and the set fluid volume differ by at least the predetermined amount; control means for operating the actuating device at a second speed lower than the first speed when the fluid capacity and the set fluid capacity differ by less than the predetermined amount. A hydrostatic transmission device characterized by: 2. A pump unit that converts mechanical force into hydrostatic pressure, a motor unit that is fluidly connected to the pump unit and converts the hydrostatic pressure into mechanical force, and a variable fluid capacity of one of the pump unit and the motor unit. an actuating device for causing fluid to flow through the actuating device, the actuating device being actuated so that the fluid capacity of the one unit increases by transitioning from a neutral state to a first state; a main control valve device that operates the actuating device so that the fluid capacity of the one unit decreases by transitioning from a neutral state to a second state; and a device that transitions the main control valve device from a neutral state to a first state. And,
and when the main control valve device is in a second state, the rate at which the actuating device reduces the fluid capacity of the one unit is varied by varying the flow rate of fluid flowing through the main control valve device. A first pilot valve device and a device for shifting the main control valve device from a neutral state to a second state, the device being configured to flow through the main control valve device when the main control valve device is in the first state. and a second pilot valve device for varying the rate at which the actuating device increases the fluid capacity of the one unit by varying the flow rate of fluid.