JP2001336602A - Hydraulic driving system for plurality of motors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving system for a plurality of motors for preventing seizure of hydraulic motors connected to a clutch and restraining the occurrence of oil hammering at clutch releasing and engaging time. SOLUTION: In a driving system, at least one hydraulic motor 7 of the hydraulic motors is connected to a driving part 1 via a power transmission device 9, the other hydraulic motor 8 is directly connected to the driving part 1, and the two or more hydraulic motors 7 and 8 parallelly connected to a pressure oil supply conduit 6 of a hydraulic pump 3 are selectively driven according to required torque. Pressure oil of a very small flow rate is always supplied to the hydraulic motor 7 connected to the power transmission device 9 via a flow control means 13a arranged in the pressure oil supply pipeline 6a of the motor 7, and flow selecting operation of the pressure oil is gradually performed for a prescribed time via a flow selecting control means 13b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system capable of selectively driving two or more hydraulic motors connected in parallel to a discharge line of a hydraulic pump in accordance with a required torque.

[0002]

2. Description of the Related Art Work vehicles such as construction vehicles and mobile cranes are required to have a strong climbing ability on steep terrain and to be able to travel on flat terrain at a required vehicle speed. Also, for example, in various working machines such as a winch,
Operation switching between high-speed low-torque and low-speed high-torque is required. Usually, this type of driving is performed by driving a hydraulic motor with hydraulic pressure from a hydraulic pump. However, in order to respond to these changes by, for example, changing the discharge capacity of a variable displacement pump or simply switching gears, a large pump that matches the required maximum absorption torque must be used. In most operations, the pump will have more performance than necessary, which is inefficient.

In order to solve such a problem, for example, Japanese Patent Publication No. Hei 4-501992 proposes a system in which at least two hydraulic motors are connected in parallel to a hydraulic oil supply line of one hydraulic pump. . In this system, at least one axle is driven by a plurality of hydraulic motors. A part of the hydraulic motor is configured to be able to be separated from the axle by a clutch.

FIG. 7 shows a hydraulic drive system for a rope winch which is a specific example disclosed in the above publication. The engine 2 drives a variable displacement pump 3 having a continuously variable discharge volume and two flow directions as an energy source. The pressure oil supply line 6 in the closed circuit of the pump 3
Two variable displacement motors 7, 8 are connected in parallel.

[0005] The hydraulic motor 7 is connected to a rope winding cylinder 33 via a separation clutch 9 and a transmission device 31 having a required speed increase ratio. One hydraulic motor 8 is directly connected to the rope winding cylinder 33 via a transmission 32 having a required speed increase ratio. Transmission 3 connected to clutch 9
The speed increase ratio of 1 is larger than the speed increase ratio of the transmission 32. The hydraulic motor 7 connected to the clutch 9 and the pressure oil supply pipes 6a and 6a 'on the supply side and discharge side of the hydraulic motor 7
4, 35 are provided.

When the rope winding drum 33 is driven at low speed and high torque, the clutch 9 is engaged. The discharge flow rate of the variable displacement pump 3 is supplied to hydraulic motors 7 and 8, respectively. At this time, the number of rotations of each hydraulic motor 7 or 8 is smaller than when each hydraulic motor 7 or 8 is driven alone. In the illustrated example, the rotational speed of the winch decreases and the driving torque increases.

When the rope winding drum 33 is driven at high speed and low torque, the clutch 9 is released. Hydraulic motor 7 or 8
Is driven alone to increase its rotation speed. In the example shown in FIG. 7, the rotation speed of the winch is increased and the driving torque is reduced, and for example, an empty hook is raised at a high speed.

[0008] As described above, according to the hydraulic drive system disclosed in the above publication, the required torque is reduced, and the capacity of the hydraulic motor 7 connected to the clutch 9 is reduced. It is opened, and at the same time, the shutoff valves 34 and 35 are shut off, and the entrance and exit of the hydraulic motor 7 are closed. When the required torque increases and the capacity of the hydraulic motor 8 directly connected to the rope winding cylinder 33 increases to near the limit, the separation clutch 9 is engaged and the shut-off valve 3 is closed.
4 and 35 are opened to supply hydraulic oil to the hydraulic motor 7 engaged with the clutch 9. The engagement of the clutch 9 causes the hydraulic motor 7 to start rotating at a high speed.

[0009]

In the above system, when the required torque decreases, the clutch is released instantaneously. If the shut-off valve is momentarily closed at this time, not only will an oil hammer occur, but also the pressure oil that had been diverted to the parallel pipes will be transferred to the pressure oil supply pipe of the hydraulic motor directly connected to the axle. A large flow of hydraulic oil is instantaneously supplied, and the rotation of the axle is rapidly accelerated.

On the other hand, when the required torque increases and the output rotation decreases to engage the separation clutch and open the shutoff valve, the hydraulic motor connected to the separation clutch rotates at high speed. At this time, when there is a time lag between the engagement time of the separation clutch and the opening operation time of the shut-off valve, or when the hydraulic motor continues to rotate due to inertia, the motor is operated without supplying hydraulic oil to the hydraulic motor. It rotates at high speed and may cause seizure. Further, if the engagement of the separation clutch and the opening operation of the shut-off valve are performed simultaneously and instantaneously, not only oil hammer occurs and vibration occurs in the drive system, but also it takes time until the required torque is obtained. And work efficiency may be reduced.

A main object of the present invention is to prevent a seizure of a hydraulic motor connected to the clutch and to suppress the occurrence of oil hammer when the clutch is disengaged / engaged. Is to provide. Another object is to achieve an appropriate volumetric efficiency of the hydraulic pump applied to the hydraulic drive system.

[0012]

The invention according to claim 1 is connected in parallel to a hydraulic oil supply line of a hydraulic pump, and can selectively drive the same drive unit according to required torque. A drive system including two or more hydraulic motors, wherein at least one of the hydraulic motors is connected to the drive unit via a power transmission device, and connected via the power transmission device. Other hydraulic motors except the hydraulic motor are fixedly connected to the drive unit,
The hydraulic motor connected to the power transmission device is supplied with a small amount of pressure oil through a flow control means arranged in a pressure oil supply line of the motor at all times. In the drive system.

Now, when a large load is applied to the operating portion and it becomes necessary to operate the operating portion at a high torque and a low speed, the clutch is engaged by an operation of an operator or a detection signal from a load detector. By the engagement of the clutch, the required amount of pressure oil is supplied to the pressure oil supply line of the hydraulic motor to which the clutch is engaged, and two or more hydraulic motors are driven simultaneously, and the operating part is raised by the total output. Operates at low torque.

When the load on the operating portion is reduced and the operating portion is operated at a low torque and at a high speed, the clutch is released and a flow control means provided in a hydraulic oil supply line of a hydraulic motor connected to the clutch. Operates to continue supplying a minute flow of pressure oil to the same pressure oil supply line. At this time, when the variable displacement type is used for the hydraulic pump and the hydraulic motor, the displacement of the hydraulic pump is adjusted to the volume required for high-speed driving, and the capacity of the hydraulic motor connected to the clutch is fixed to zero. Here, the minute flow rate is a flow rate necessary for lubrication of the hydraulic motor connected to the clutch.

Therefore, according to the present invention, even when the operating section is operated at a low torque and a high speed, the pressure oil supply line leading to the hydraulic motor connected to the clutch is not completely closed as in the related art, but is always closed. Continue to supply a small amount of pressure oil. This minute flow of pressure oil functions as a lubricating oil, and even if the clutch is instantaneously engaged to switch to high-torque low-speed operation, seizure of the hydraulic motor can be prevented. Also, although a leak usually occurs in the hydraulic system, according to the present invention, as described above, even though the amount is small, the required flow rate is continuously supplied to the pressure oil supply pipe leading to the hydraulic motor connected to the clutch. In addition, the discharge flow rate of the hydraulic pump is always used effectively.

According to a second aspect of the present invention, the operation of switching from a large flow rate to a very small flow rate of the hydraulic oil supply line of the hydraulic motor based on the opening of the power transmission device is performed for a predetermined time after the power transmission device is opened. It is characterized by having flow rate switching control means for controlling so as to end after performing.

Normally, the clutch release operation is performed instantaneously. At this time, if the switching operation from the large flow rate to the minute flow rate for the pressure oil supply line by the flow rate control means is performed simultaneously and instantaneously with the release of the clutch, an oil hammer occurs and the drive system vibrates. Therefore, in the present invention, in the switching operation from the large flow rate to the small flow rate, the flow rate switching control means operates to start the switching operation simultaneously with the release of the clutch, and completes the switching after a lapse of a certain time. Control.

Specifically, for example, a switching operation is started at the same time as a clutch release signal is input to the flow rate switching control means, and while the flow rate supplied to the hydraulic motor with the clutch released is gradually reduced, Control is performed so as to reach a predetermined minute flow rate after a set time has elapsed. By such timing control of flow rate switching,
Oil flow does not occur, and the flow rate can be switched smoothly.

[0019]

FIG. 1 shows a first embodiment of the present invention. The axle 1 is taken as an example of the drive unit. The engine 2 drives a variable displacement pump 3 having two flow directions. This hydraulic circuit is called an HST (hydrostatic transmission) circuit.

In the variable displacement pump 3, first and second two variable displacement motors 7, 8 are connected in parallel to a pressure oil circulation line 6 having a closed circuit. The output shaft of the first variable displacement motor 7 is connected to a reduction gear 10 of the axle 1 via a clutch 9 which is a power transmission device in the present invention.
One second variable displacement motor 8 is directly connected to the speed reducer 10.

The opening and closing operation of the clutch 9 is controlled by the clutch control valve 1
1 controls its timing and the like. In the first embodiment, a pilot pressure for controlling the displacement (inclination angle) of the first and second variable displacement motors 7 and 8 during driving is connected to the clutch control valve 11. The rotation of the output shaft of the second variable displacement motor 8 connected to the axle 1 via the reduction gear 10 rotates the small pump 12 having a two-way flow, and changes the discharge flow rate of the small pump 12. Is transmitted to the clutch control valve 11. The sum of the outputs of the first and second variable displacement motors 7, 8 is transmitted to the axle 1.

The first pressure oil supply line 6a, which branches off from the pressure oil circulation line 6 and supplies the pressure oil to the forward port of the first variable displacement motor 7, has flow rate control means and flow rate switching control means. The lock valve 13 is provided. On the other hand, no special valves are provided in the second pressure oil supply line 6b that supplies pressure oil to the forward port of the second variable displacement motor 8,
It is directly connected to the forward port of the variable displacement motor 8.

In the present embodiment, the lock valve 13 is
The switching control of the supply of the pressure oil to the forward port of the first variable displacement motor 7 at the time of forward movement is performed by disposing only the pressure oil supply line 6a, but the lock valve 13 is connected to the first variable displacement motor 7 7
May be arranged in the pipeline 6a 'connected to the reverse port. In this case, it is possible to perform both control during forward and backward travel.

The lock valve 13 includes a main valve 13a and a slave valve 13b.
And The main valve 13a constitutes the flow control means, and the slave valve 13b constitutes the flow switching control means.
The main valve 13a is composed of a 2-port 2-position switching valve that switches between a fully open position (C) and a throttle position (D), and the slave valve 13b is a drain position (A) for draining the pressure oil in the first pressure oil supply line 6a. ) And a pilot pressure output position (B) in which the same pressure oil is used as the pilot pressure of the main valve 13a.
Consists of a position switching valve.

The main valve 13a always receives the pilot pressure from the first pressure oil supply line 6a and the line 6a '.
The sum of the pilot pressures and the spring force of the spring 13d are balanced and connected to the position shown in FIG. 1, that is, the fully open position (C) where the first pressure oil supply line 6a and the line 6a 'communicate. . The throttle position (D) of the main valve 13a is constituted by a flow control valve. In the present embodiment, this flow control valve is a fixed throttle. This flow control valve may be constituted by a variable throttle.

An output signal from the clutch control valve 11 is input to the slave valve 13b as an external pilot signal.
The input of the pilot signal overcomes the spring force of the spring 13e, and is switched from the drain position (A) to the pilot pressure input position (B). When the pilot signal is not input, the slave valve 13b stops at the drain position (A) due to the spring force of the spring 13e, and the pilot pressure to the main valve 13a is not output. A fixed throttle valve 13c is arranged in the pilot pressure output line of the slave valve 13b.

Next, the supply of pressure oil to the general first variable displacement motor 7 by the hydraulic drive system of the present invention, the displacement of the motor 7 and the operation of the lock valve 13 will be described with reference to FIG.

Now, in the section A in the figure, the vehicle is in a stopped state. The vehicle starts running from the starting point. At this time, the clutch 9 between the first variable displacement motor 7 and the axle 1 is in the engaged state, and the vehicle starts running by the sum of the outputs of the first and second variable displacement motors 7 and 8. Thereafter, at the point of acceleration, when the required torque decreases until the vehicle can be driven by the second variable displacement motor 8 alone, the clutch 9 is released and the first variable displacement motor 7 is disengaged.
At this time, the capacity of the first variable displacement motor 7 is controlled from the maximum to zero.

Switching of one lock valve 13 is started almost simultaneously when the clutch 9 is released. This lock valve 1
If 3 is instantaneously switched, oil hammer may occur or seizure may occur in the second variable displacement motor 7. Therefore, in the present invention, the switching operation of the lock valve 13 is performed by the clutch 9
Is completed after a predetermined time elapses after is released. At this time, the throttle opening of the main valve 13a is controlled by the slave valve 13b, and the throttle opening of the main valve 13a is gradually reduced.
First pressure oil supply line 6a supplied to variable displacement motor 7
Of the pressure oil is gradually decreased, and finally the supply amount of the minute flow rate is obtained.

In this way, after a predetermined time has passed after the clutch 9 is released, the lock valve 13 is closed (D).
Switch completely to. Since the lock valve 13 is not instantaneously switched, no oil hammer occurs. In addition, even after the lock valve 13 is switched, the first variable displacement motor 7 is supplied with a small amount of pressure oil through the flow control valve formed of a fixed throttle. No acceleration occurs and smooth acceleration is realized.

In this state, when the drive unit is decelerated to increase the required torque, the clutch 9 is engaged at the point (1), and the capacity of the first variable displacement motor 7 is sequentially increased from zero to the maximum.
At this time, the operation of switching the lock valve 13 to the communication side (C) is started almost simultaneously. Even at the time of this clutch engagement, the lock valve 13 is not instantaneously switched to prevent the pressure oil from being rapidly supplied to the first variable displacement motor 7 and the communication side is switched after a preset time has elapsed. Control is performed to end the switching to (C). As a result, not only no oil hammer occurs, but also smooth deceleration is performed.

The operation will be specifically described with reference to FIG. Now, the lock valve 13 has the main valve 13a at the fully open position and the slave valve 13b at the drain position. For example, when the vehicle climbs a steep slope, the axle 1 is required to rotate at a high torque at a low speed. Here, the clutch 9 is engaged, and the capacities of the first and second variable displacement motors 7, 8 are maximized.
The discharge flow rate of the variable displacement pump 3 is small, and the discharge pressure is set at or near the maximum pressure. The vehicle, not shown, runs at low speed with high horsepower. As the speed of the vehicle increases from this state, the discharge pressure of the variable displacement pump 3 gradually decreases accordingly. When the clutch 9 is engaged, no pilot signal is output from the clutch control valve 11 to the slave valve 13b.

During the running of the vehicle, the displacements of the first and second variable displacement motors 7, 8 and the discharge flow rate and pressure of the first variable displacement motor 7 are always detected. Is transmitted to When the required torque of the motor during acceleration is reduced to the required torque that can be sufficiently accelerated by the single driving of the second variable displacement motor 8,
A clutch release signal is output from the clutch control valve 11 to release the clutch 9 with a delay.

The clutch release signal from the clutch control valve 11 is simultaneously input to the slave valve 13b as a pilot signal. When a pilot signal is input, the slave valve 13b overcomes the spring force of the spring 13e and switches from the drain position (A) shown in FIG. 1 to a pilot pressure output position (B) for outputting pilot pressure to the main valve 13a. . At this time, the pilot pressure oil input to the main valve 13a is
The switching is completed after a lapse of a required time Δt because the current flows through the line c.

Therefore, during the switching time Δt, the main valve 13
The pilot pressure for a gradually increases, and the throttle opening of the flow control valve on the throttle position side of the main valve 13a is gradually reduced to gradually reduce the flow rate passing through the main valve 13a. In this way, the occurrence of oil hammer that is likely to occur when the main valve 13a is instantaneously switched to the closed side is prevented. At the same time that the clutch release signal is output, the capacity of the first variable displacement motor 7 is set to zero.

The flow rate of the pressure oil passing through the main valve 13a after being switched in this way, that is, the flow rate of the pressure oil supplied to the first variable displacement motor 7, is not completely shut off, and the fixed throttle of the main valve 13a is closed. The flow rate is very small. As a result, even if the clutch 9 is released, a very small amount of pressure oil is always supplied to the first variable displacement motor 7 through the first pressure oil supply line 6a. Burn-in of the variable displacement motor 7 is prevented.

In general, leakage occurs from the pressure oil supply / discharge path and also into the tank. Although the leak amount increases when the pressure in the supply / discharge path is high, in the present invention, even after the clutch 9 is released as described above, the pressure oil limited to a very small flow rate is supplied to the first pressure oil supply pipe. Since the power is supplied to the first variable displacement motor 7 through the passage 6a ', the amount of leakage is also reduced, and the volumetric efficiency of the variable displacement pump 3 on the system is improved.

When the acceleration of the vehicle is completed and the vehicle is running at a steady speed, the required torque of the second variable displacement motor 8 is reduced, and the discharge volume of the variable displacement pump 3 is adjusted to an appropriate value. Run your vehicle with maximum efficiency.

When the vehicle shifts from steady running to decelerating running, a large required torque is required gradually as in the case of starting. Based on the torque change, an engagement signal is output from the clutch control valve 11 during deceleration, and the clutch 9 is engaged to start driving the first variable displacement motor 7. The engagement operation of the clutch 9 is controlled not to be instantaneous but to be gradually engaged, and is controlled so that the engagement is completely terminated after a required time has elapsed. Therefore, the output of the pilot signal from the clutch control valve 11 to the slave valve 13b also continues in conjunction with the output of the clutch engagement signal.

In this embodiment, the switching of the slave valve 13b to the drain position (A) is controlled to be terminated when the clutch 9 is in the half-clutch state immediately before the clutch 9 is completely engaged. . On the other hand, the swash plate angle of the first variable displacement motor 7, the capacity of which has been reduced to zero at the same time as the release of the clutch, increases in accordance with the output time of the clutch engagement signal, and eventually increases to the maximum capacity.

In the description of the present embodiment, all the hydraulic pumps and the hydraulic motors are of the variable displacement type, and the hydraulic motors are all motors having the same maximum capacity. Any or all may be of a fixed displacement type, and two or more hydraulic motors having different maximum displacements may be employed. In the present embodiment, a closed circuit is described as the hydraulic circuit, but an open circuit may be used. The same applies to the description of the following embodiments.

FIG. 3 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment in three points. The first is that the valve on the closing side (D) of the main valve 13a is a fixed throttle valve, whereas in the present embodiment, the valve on the closing side (D) of the main valve 113a is a complete closing valve. It is. Second, a pressure compensating flow control valve 15 is arranged in parallel with the first pressure oil supply line 6a in addition to the main valve 113a. The third is the main valve 1
The point is that a pilot pressure control valve 14 composed of a pressure compensation type flow control valve is arranged in a pilot pressure control line from the slave valve 113b to the pilot valve 13a. These pressure-compensated flow control valves flow a constant flow of hydraulic oil with the differential pressure before and after the throttle valve always being constant, irrespective of the pressure on the input side.

In this embodiment, it is assumed that the required torque for the axle 1 is large and pressure oil is supplied to the first variable displacement motor 7 with the clutch 9 engaged. At this time, the slave valve 113b is output from the clutch control valve 11.
No pilot signal is input. Therefore, the slave valve 113b is at the drain position (A) shown in FIG.
No pilot pressure is output to the main valve 113a.
a maintains the communication position (C) of the first pressure oil supply pipe line 6a. At this time, a part of the pressure oil in the first pressure oil supply pipe line 6 a also flows to the flow control valve 15.

Next, when the required torque decreases and it becomes possible to operate the axle 1 independently by driving the second variable displacement motor 8, a clutch release signal is output from the clutch control valve 11 and the clutch 9 is released. It is released, and the capacity of the first variable displacement motor 7 becomes zero. The release signal of the clutch 9 is also sent to the slave valve 113b as a pilot signal, and switches the slave valve 113b to the pilot pressure output position (B). As a result, a part of the pressure oil in the first pressure oil supply line 6a is sent from the slave valve 113b to the main valve 113a via the pilot pressure control valve 14 as pilot pressure.

Even if the pilot pressure fluctuates and the pressure on the upstream side of the throttle 14a increases, the pressure on the downstream side increases at a similar rate, so that the pilot flow rate flowing into the main valve 113a is always maintained at a constant flow rate. The switching speed of the main valve 113a is also kept constant, the closing amount of the communication side port of the main valve 113a is gradually increased, and after a predetermined time has elapsed, the main valve 113a is completely switched to the closing position (D). Cut off.

That is, when the release signal of the clutch 9 is input, the main valve 113a starts switching from the communication side (C) to the disconnection side (D), and the pilot pressure control valve 14 functions as a timer. After a predetermined time, it will be completely shut off. Therefore, no oil hammer occurs due to the switching of the clutch 9, and no abnormal noise is generated, and a smooth shift operation can be performed.

Even after the supply of the pressure oil to the main valve 113a is completely shut off, the first variable displacement motor 7 is supplied to the first variable displacement motor 7 via the flow regulating valve 15 disposed in the bypass passage so as to maintain a small constant flow rate. Pressurized oil continues to be supplied. Therefore, even if the first variable displacement motor 7 rotates by inertia when the clutch 9 is released, the pressure oil with a small flow rate functions as lubricating oil, so that the occurrence of seizure is reliably prevented. You.

FIG. 4 shows a third embodiment of the present invention. In this embodiment, the operation as a hydraulic drive system is basically the same as in the first and second embodiments, and the structure and circuit of the lock valve are different. In FIG. 4, reference numeral 213 denotes the lock valve 13 in the first embodiment.
9 shows a lock valve which is a modification example of FIG.

The main valve 213a, which is one of the components of the lock valve 213, is a two-port, two-position switching valve, and has an inlet side and an outlet side for the communication side (C ') and closing side (D') valves. Flow control valves 16 are arranged in parallel on the sides. Further, the slave valve 213b is a three-port two-position spool valve, and a pilot pressure control valve 18 that functions as a timer for the main valve 213a is disposed in a branch line branched from the first pressure oil supply line 6a. . Both the flow control valve 16 and the pilot pressure control valve 18 are pressure-compensated flow control valves, and keep a constant flow at a constant pressure difference between the supply side and the discharge side irrespective of the pressure fluctuation on the supply side.

The first variable displacement motor 7 has a main valve 213a.
A constant minute flow rate of pressure oil is supplied through a flow control valve 17 disposed between the closed ports. When the vehicle is accelerated from this state, the clutch 9 is released, and the discharge volume of the variable displacement pump (not shown) is minimized, a pilot signal from a clutch control valve (not shown) is supplied similarly to the above-described embodiment. Is done. At this time, the child valve 213b is moved to the communication position (B ').
Switch to.

The switching speed of the child valve 313b at this time is determined by the throttle opening area of the pilot pressure control valve 18, and is gradually communicated. When the slave valve 213b is switched to the communication position (B '), the pilot control line 13 of the main valve 213a is switched.
Pressure oil having a constant flow rate is sent to f through the pilot pressure control valve 18 to control the switching speed of the main valve 213a to gradually switch to the communication side (C ') and the closing side (D'). .

FIG. 5 shows a fourth embodiment of the present invention. Reference numeral 313a in the figure indicates a main valve in the present embodiment corresponding to the main valve 13a in the first embodiment, and is a further modified example of the main valve structure and its hydraulic circuit in the third embodiment.

The main valve 313a shown in FIG. 3 is a two-port three-position switching valve, and is an opening position for completely connecting the first pressure oil supply line 6a and the supply side port of the first variable displacement motor 7 to each other. (E), an intermediate opening position (F) for reducing the flow rate by inserting a throttle, and a closing position (G) for completely closing the flow. Further, the respective supply-side ports and discharge-side ports at the respective switching positions (E to G) are connected in parallel by the flow rate adjusting valve 19. Child valve and main valve 313a not shown
A pilot pressure control valve 22 functioning as a timer is disposed in the pilot pressure control line between the two.

When the required torque decreases and a clutch release signal is output from a clutch control valve (not shown), the clutch is released and, at the same time, the signal is sent to a child valve (not shown). With this signal, the slave valve is switched from the closed side to the communicating side, and the pilot oil at a constant flow rate through the pilot pressure control valve 22 is supplied to the main valve 313a by the hydraulic oil from the first hydraulic oil supply line (not shown). To enter.

The switching speed of the main valve 313a is determined by appropriately selecting the flow rate of the pilot pressure control valve 22 at this time. At the switching speed, the main valve 313a is sequentially switched from the three positions (E to G) from the completely communicating position (E) to the closing position (G), so that instantaneous switching is not performed and occurrence of oil hammer is prevented. . Even if the clutch is released, the minute flow of the pressure oil flows through the flow regulating valve 19 of the main valve 313a, and the minute flow continues to be supplied to the first variable displacement motor 7. Therefore, the seizure of the motor 7 is effectively prevented even if the inertial rotation of the motor 7 continues. Here, when a large required torque is required, an operation opposite to the operation is performed,
When the clutch is engaged, the axle is operated by the first and second variable displacement motors (not shown).

FIG. 6 shows a fifth embodiment of the present invention. Reference numeral 413 in the figure indicates a lock valve corresponding to the lock valve 13 of the first embodiment. Other configurations and operations are basically the first
There is no difference from the embodiment.

The main valve 413a is connected to the main valve 41 shown in FIG.
A pilot switching valve having the same 2-port and 3-position as 3a is used, and the left and right pilot pressure working areas are smaller on the left than on the right. The spring 413g of the main valve 413a determines the initial position of the main valve 413a by a weak spring force.
On the other hand, the sub-valve 413b is composed of a pilot switching valve in a 3-port, 2-position position. In this embodiment, a pilot pressure control valve 23 functioning as a timer is disposed in the branch line 6a ″ in the present embodiment.

Now, the required torque decreases, and the second torque (not shown)
When the axle (not shown) can be rotated at a high speed by independent driving of the variable displacement motor, a clutch release signal is output from a clutch control valve (not shown), the clutch is released, and the capacity of the first variable displacement motor is increased. Is set to zero.

At this time, a clutch release signal is also input to the child valve 413b as a pilot signal, and the child valve 413b is switched from the closed position (B) to the communication position (A). The switching at this time is performed instantaneously. The flow rate of the pressure oil supplied to the slave valve 413b from the first branch line 6a "is controlled by a pilot pressure control valve 23 disposed in the branch line 6a" branching from the first branch line 6a ". are doing. The pressure oil at the constant flow rate is input as pilot pressure, and the main valve 413a
To the fully closed position (G). At this time, the main valve 413a is switched at a preset switching speed, and the main valve 413a is sequentially switched from the fully open position (E) to the fully closed position (G) through the half-open position (F) by the throttle.

As described above, the main valve 413a is switched while the passing flow rate is reduced over a required period of time, so that occurrence of oil hammer is prevented. In addition, even after the main valve 413a is completely closed, a small amount of pressure oil is continuously supplied to the first variable displacement motor via the flow control valve 19 in which the main valve 413a is disposed in the completely closed position (G). Can be For this reason, seizure of the motor that rotates by inertia when the clutch is released is also prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a main part showing a first embodiment of a hydraulic drive system of the present invention.

FIG. 2 is an explanatory diagram showing a general hydraulic drive sequence according to the present invention.

FIG. 3 is a hydraulic circuit diagram of a main part showing a second embodiment of the hydraulic drive system of the present invention.

FIG. 4 is a circuit diagram showing another embodiment of the lock valve.

FIG. 5 is a circuit diagram showing still another embodiment of the lock valve.

FIG. 6 is a circuit diagram showing still another embodiment of the lock valve.

FIG. 7 is a hydraulic circuit diagram showing an example of a conventional one-pump two-motor hydraulic drive system.

[Explanation of symbols]

 Reference Signs List 1 axle 2 engine 3 variable displacement pump 6 pressure oil circulation line 6a first pressure oil supply line 6b second pressure oil supply line 6a 'line 6a "branch line 6b' line 7 first variable displacement type Motor 8 Second variable displacement motor 9 Clutch 10 Drive gear train 11 Clutch control valve 12 Small pump 13 Lock valve 13a, 113a, 213a, 313a, 413a Main valve 13b, 113b, 313b, 413b Child valve 13c Fixed throttle valve 13d, 13e, 413g, 413h Spring 13f, 413f Pilot control line 14,18,22,23 Pilot pressure control valve 14a Restrictor 15,19 Flow control valve 31,32 Transmission 33 Rope winding cylinder 34,35 Shut-off valve

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiyuki Akasaka 400 Yokokura Nitta, Oyama City, Tochigi Pref. BC18 BD02 BD08 BD09 3J053 AA01 AA03 AB12 AB23 AB46 EA07 FB01 FB03

Claims (2)

[Claims] 1. A drive system comprising two or more hydraulic motors connected in parallel to a pressure oil supply line of a hydraulic pump and capable of selectively driving the same drive unit according to a required torque, At least one of the hydraulic motors is connected to the drive unit via a power transmission device, and other hydraulic motors except the hydraulic motor connected via the power transmission device are fixed to the drive unit. The hydraulic motor connected to the power transmission device is supplied with a very small amount of pressure oil through a flow control means disposed in a pressure oil supply pipe of the motor. Features a multi-motor hydraulic drive system. 2. A control operation for switching from a large flow rate to a small flow rate in a hydraulic oil supply line of a hydraulic motor based on the opening of the power transmission device so as to end after a lapse of a predetermined time after the opening of the power transmission device. 2. The hydraulic drive system according to claim 1, further comprising a flow rate switching control unit that performs the switching.