JPH11230333A - Plural hydraulic motors and clutch controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify construction and prevent shift shock and hydraulic motor load release. SOLUTION: The plural hydraulic motors and a clutch controller is provided with a second hydraulic motor 2 constantly connected a drive shaft 3, a variable capacity type first hydraulic motor 1 connected to the drive shaft 3 through a clutch 4, a tilt control means 5, 6 making the discharge capacity (cc/rev) of a first hydraulic motor 1 variable by means of controlling the tilting amount of the hydraulic motor 1 by receiving drive side oil pressure driving the first hydraulic motor 1, and a tilt fixing means 10 fixing the tilt amount of the first hydraulic motor 1 by tilt control means 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a plurality of hydraulic motors and clutches, and more particularly to a hydraulic drive device for a working machine such as a wheel loader or a hydraulic shovel, which controls the output torque of the plurality of hydraulic motors to a clutch. The present invention relates to a control device for a plurality of hydraulic motors and clutches, which are connected and output via a motor.

[0002]

2. Description of the Related Art Conventionally, in a hydraulic traveling drive system for a vehicle which is driven by connecting output torques of a plurality of hydraulic motors via a clutch, connection and disconnection of a clutch are controlled when a vehicle speed reaches a predetermined value. To control output torque, vehicle speed, etc. FIG. 7 is a control circuit diagram of a control device for a plurality of hydraulic motors and clutches of a conventional hydraulic traveling drive device. This control circuit includes a hydraulic pump 50, a first hydraulic motor 51, a second hydraulic motor 52, a clutch 53, a hydraulic pump 54, and the like. The first hydraulic motor 51 and the second hydraulic motor 52 are connected in parallel to the hydraulic pump 50 and are driven by the discharge pressure oil of the hydraulic pump 50. A motor gear 51b is fixed to the first output shaft 51a of the first hydraulic motor 51, and the motor gear 51b meshes with a drive shaft gear 55a of a drive shaft 55 that drives the vehicle. First
The output torque of the hydraulic motor 51 is supplied to the drive shaft 55 for driving the vehicle via the motor gear 51b and the drive shaft gear 55a.
Always communicated to

[0003] A clutch 53 is provided on a second output shaft 52a of the second hydraulic motor 52, and a second motor gear 53b is fixedly provided on the second output shaft 53a of the clutch 53, and a second motor gear 53b is provided. The gear 53b meshes with a drive shaft gear 55a of a drive shaft 55 that drives the vehicle. When the clutch is connected, the output torque of the second hydraulic motor 52 is transmitted to the drive shaft 55 that drives the vehicle via the clutch 53, the second motor gear 53b, and the drive shaft gear 55a. Each of the first hydraulic motor 51 and the second hydraulic motor 52 has a servo valve (not shown) attached thereto. The servo valve is provided by a signal pressure from a high / low valve (hereinafter, referred to as an HL valve) for selecting high speed or low speed. The discharge capacity D (cc / rev) of the hydraulic motor is controlled.

The hydraulic pump 54 is connected to a drive shaft gear 55a of a drive shaft 55 by a pump gear 54a and a second motor gear 53b. A throttle 54b and a shuttle valve 54c are provided between the Fp port and the Rp port of the hydraulic pump 54.
Are connected in parallel, and when the rotation speed (vehicle speed) of the drive shaft 55 exceeds a predetermined value, the discharge pressure of the hydraulic pump 54 reaches a predetermined value and acts on the clutch 53 via a pipe 54d.
When the clutch 53 is disengaged and the rotational speed (vehicle speed) of the drive shaft 55 falls below a predetermined value, the discharge pressure of the hydraulic pump 54 does not reach the predetermined value, so that the clutch 53 comes into contact. The hydraulic pump 50 and the first hydraulic motor 51 are always connected, but a communication / shutoff valve 56 is interposed between the hydraulic pump 50 and the second hydraulic motor 52.

The function of the communication / shutoff valve 56 will be described.
When the second hydraulic motor 52 has a tilt amount, the clutch 53
When the clutch 53 is shut off, a shift shock occurs.
Before turning off, the second hydraulic motor 52 is tilted to zero. However, since there is no means for holding the second hydraulic motor 52 at the zero tilt, the second hydraulic motor 52 is slightly tilted by a sudden shift or the like after the second hydraulic motor 52 is tilted to zero (see FIG. 9, S5), the second hydraulic motor 52 idles, and the first hydraulic motor 51 loses its load. After the second hydraulic motor 52 is tilted to zero to prevent this load loss, the clutch 53 is disconnected and the hydraulic pump 5
0 and the hydraulic pipe connecting the second hydraulic motor 52
It is shut off by the shutoff valve 56.

Next, the operation will be described. FIG. 8 shows the relationship between the discharge capacity D (cc / rev) of the hydraulic motor and the vehicle speed V (km / h) in the low-speed Lo range. The curve S1 is for the first hydraulic motor 51, and S2 is for the second hydraulic motor 52. It is. For example, in the loader, when the vehicle speed is up to 12 km / h, the discharge pressure of the hydraulic pump 54 does not reach the predetermined value, so that the clutch 53 is in the connected state, and the vehicle is driven by the sum of the discharge capacities of the first hydraulic motor 51 and the second hydraulic motor 52. (S1 + S2) drives with a large driving force. Further, L is controlled by an HL valve (not shown).
o When the range is set, the discharge capacity of the first hydraulic motor 51 and the second hydraulic motor 52 is limited, and the maximum vehicle speed is 12 km.
Only goes up to / h.

FIG. 9 shows the relationship between the displacement D (cc / rev) of the hydraulic motor and the vehicle speed V (km / h) in the high-speed Hi range. The curve S3 is the first hydraulic motor 51, and the curve S4 is the second hydraulic motor 5.
It is about 2. Until the vehicle speed reaches 15 km / h, the clutch 53 is in the engaged state because the discharge pressure of the hydraulic pump 54 does not reach the predetermined value. However, when the vehicle speed approaches 15 km / h, the discharge capacity S4 of the second hydraulic motor 52 becomes almost zero. It becomes 0. The high-speed Hi range is set by the HL valve 10 and the first
Since the limitation on the discharge capacity of the hydraulic motor 51 is released, the maximum vehicle speed of the vehicle is increased to 30 km / h or more by only the discharge capacity S3 of the first hydraulic motor 51. At this time, when the vehicle speed exceeds 15 km / h, the discharge pressure of the hydraulic pump 54 reaches a predetermined value, and the clutch 53 is disconnected.

[0008]

In the above-described conventional hydraulic traveling drive device, the communication / shutoff valve 56 needs to have a capacity capable of passing the entire discharge amount of the second hydraulic motor 52, so that only the space is required. However, there is a problem that the cost of the piping work and the communication / shutoff valve 56 increases. Further, since it is necessary to shut off the communication 53 and the shutoff valve 56 at the same time as shutting off the clutch 53,
If the delicate timing is not satisfied, there is a problem that a shift shock of the vehicle may occur. Further, when the first and second hydraulic motors 51 and 52 are fixed to a large amount of displacement and the braking torque is increased to reduce the speed, if the fixed amount of displacement is suddenly released at a high speed, the vehicle may be disengaged. It may overrun. For this reason, it is desired to hold the increased tilt amount during deceleration until a release command is issued.

The present invention relates to a control device for a plurality of hydraulic motors and clutches which focuses on the above-mentioned conventional problems, and in particular, simplifies the structure by omitting a communication / shutoff valve, and furthermore, to simplify the structure of the clutch and the communication / shutoff valve. It is an object of the present invention to provide a control device for a plurality of hydraulic motors and clutches, which can eliminate a control requiring delicate timing and can prevent a shift shock and a load drop of a hydraulic motor.

[0010]

In order to achieve the above object, a plurality of hydraulic motors and a clutch control device according to the first invention of the present application provide one drive shaft with outputs of a plurality of hydraulic motors. to drive, in a plurality of control device for a hydraulic motor and clutch one of the plurality of hydraulic motors driving the drive shaft through a clutch, a second hydraulic motor which is always connected to the drive shaft, the clutch drive shaft A variable displacement type first hydraulic motor connected via a first hydraulic motor, first tilt control means for receiving a hydraulic pressure on the driving side of the first hydraulic motor and controlling a tilt amount of the first hydraulic motor, and a first hydraulic motor And zero tilt fixing means for fixing the tilt amount of the first hydraulic motor in a state where the tilt angle is controlled to be substantially zero.

According to the first aspect of the present invention, when the first hydraulic motor is fixed to a state where the first hydraulic motor has a substantially zero tilt amount by the zero tilt fixing means, the amount of oil discharged from the hydraulic pump is only the second hydraulic motor. And the drive shaft is driven only by the second hydraulic motor. Therefore, the torque of the drive shaft decreases by an amount corresponding to the first hydraulic motor being tilted to zero, but the rotational speed of the second hydraulic motor (that is, the drive shaft) increases by an amount of oil that drives the first hydraulic motor. I do. Therefore, unlike the prior art, there is no need to provide a communication / shutoff valve, so that compact, low-cost, low-torque, high-speed driving is possible.

The control device for a plurality of hydraulic motors and clutches according to a second invention of the present application is the first invention, wherein the first tilt control means controls the tilt amount of the first hydraulic motor.
A tilt cylinder, and a first servo valve that receives a hydraulic pressure on the driving side of the first hydraulic motor and outputs a control pressure of the first tilt cylinder, and the first tilt cylinder has almost zero tilt amount. In the state, the zero tilt fixing means for surely fixing the tilt amount to almost zero is a zero tilt fixing for controlling the first servo valve in a direction in which the first tilt cylinder decreases the tilt amount of the first hydraulic motor. A valve,
And a stopper means for stopping the first tilt cylinder at a position of approximately zero tilt amount.

According to the second aspect of the present invention, the zero tilt fixed valve is the first type.
The tilting amount of the first hydraulic motor is reduced by the first tilting cylinder by controlling the servo valve. The tilt amount of the first hydraulic motor is stopped at a position of approximately zero tilt amount by the stopper means and fixed at that position. Therefore, the first hydraulic motor is almost zero.
The reliability can be improved because it is securely fixed to the tilt amount position, and the cost can be reduced because only the zero tilt fixing valve and the stopper means need be added as the zero tilt fixing means.

[0014] In the control device for a plurality of hydraulic motors and clutches according to a third aspect of the present invention, in the second aspect, the stopper means comprises a stopper fixed to a piston rod of the first tilt cylinder, and a piston abutting on the stopper. A stopper cylinder having a rod.

According to the third invention, the position where the stopper fixed to the piston rod of the first tilting cylinder abuts on the piston rod of the stopper cylinder, that is, the first position
The hydraulic motor stops when the position of the hydraulic motor is almost zero. for that reason,
The structure fixes the stopper to the piston rod of the existing first tilting cylinder, and a commercially available cylinder can be used as the stopper cylinder, so that the cost is reduced, and the reliability is high because it is purely mechanical. Also, commercially available cylinders are
For example, since the stroke end can be easily adjusted from the outside by additional processing such as a stopper bolt, adjustment of the zero tilt amount position of the first hydraulic motor becomes easy.

The control device for a plurality of hydraulic motors and clutches according to a fourth aspect of the present invention is the control device according to any one of the first to third aspects, wherein the clutch switching means for switching the clutch between a connected state and a free state; At the time of increasing the speed, the tilt amount of the first hydraulic motor is fixed to almost zero by the zero tilt fixing means, and then the clutch is released. When the drive shaft is decelerated, the tilt amount of the first hydraulic motor is reduced to almost zero. And a controller (30) for outputting a command to connect the clutch to the clutch switching means before releasing the fixed state.

According to the fourth aspect of the present invention, the amount of tilt of the first hydraulic motor is reduced to zero with the clutch connected regardless of whether the drive shaft is being accelerated or decelerated, even in the case of a sudden shift of the vehicle. It is fixed or released. Therefore, since the first hydraulic motor does not tilt from 0 while the clutch is in a free state, load loss of the second hydraulic motor due to idling of the first hydraulic motor is reliably prevented. In addition, since the clutch is disengaged during high-speed, low-torque driving, energy loss due to oil agitation resistance in the first hydraulic motor is eliminated, and
Oil temperature rise is prevented. Furthermore, as in the prior art,
Since there is no need to provide a communication / shutoff valve, space is not required, compactness and cost reduction can be achieved, and shift shock can be reliably prevented.

The control device for a plurality of hydraulic motors and clutches according to a fifth aspect of the present invention, in the first aspect, includes clutch switching means for switching the clutch between a connected state and a free state, and detects a rotational speed of a drive shaft. The rotation sensor and the rotation speed signal of the drive shaft are input from the rotation sensor, and when the speed of the drive shaft is increased, the fixing of the drive shaft to be less than the first predetermined rotation speed and the tilt amount of the first hydraulic motor to be substantially zero is released. Along with
When the drive shaft exceeds the first predetermined rotation speed, the tilt amount of the first hydraulic motor is fixed to almost 0, and at the time of deceleration of the drive shaft,
When the drive shaft is at or above the second predetermined rotation speed, the tilt amount of the first hydraulic motor is fixed to approximately 0, and when the drive shaft falls below the second predetermined rotation speed, the tilt amount of the first hydraulic motor is reduced to approximately 0. A command to release the fixation is output to the 0 tilt fixing means. Also, when increasing the speed of the drive shaft, the clutch is made free after fixing the tilt amount of the first hydraulic motor, and when decelerating the drive shaft, A controller for outputting a command to connect the clutch to the clutch switching means before releasing the fixing of the hydraulic motor to make the tilt amount substantially zero is provided.

According to the fifth aspect, in addition to the same operation and effect as the fourth aspect, the predetermined rotation speed for switching between fixing and releasing the tilt amount of the first hydraulic motor to substantially zero is set to the drive shaft. The controller can be set arbitrarily to different predetermined values during acceleration and deceleration, preventing hunting of control, minimizing shock during deceleration and maximizing acceleration performance during acceleration. So that they can be adjusted to their appropriate values. In addition, the controller can select and drive the optimal combination of the driving of the first hydraulic motor and the driving of the second hydraulic motor required at the time of speed increase or deceleration according to the rotation speed of the drive shaft, so that the power is efficiently reduced with less power loss. Driving can be performed with high accuracy.

The control device for a plurality of hydraulic motors and clutches according to a sixth aspect of the present invention is the control device according to the fifth aspect, wherein the second tilting cylinder for controlling the tilting amount of the second hydraulic motor;
A second hydraulic pressure output control pressure of the second tilt cylinder is received by receiving the higher hydraulic pressure of the suction pipe and the discharge pipe of the hydraulic motor.
A servo valve and a maximum tilt fixed valve that controls the second servo valve so that the second tilt cylinder fixes the second hydraulic motor to the maximum tilt amount. When releasing the tilting amount of the first hydraulic motor to almost zero, the tilting amount of the second hydraulic motor is fixed to the maximum,
When the tilting amount of the first hydraulic motor is fixed to almost zero, a signal for releasing the fixing of the tilting amount of the second hydraulic motor to a maximum is provided. When fixing the displacement amount to approximately 0, releasing the fixation to maximize the tilt amount of the second hydraulic motor and releasing the fixation to set the tilt amount of the first hydraulic motor to approximately 0 displacement amount , A signal for fixing the tilt amount of the second hydraulic motor to the maximum is transmitted to the maximum tilt fixed valve (2).
The feature is to output to 1).

According to the sixth aspect, at the time of increasing the speed of the drive shaft, even if the tilt amount of the second hydraulic motor remains at the maximum, the fixing of the tilt amount of the first hydraulic motor to zero is released. Because there is
Even if the amount of tilt of the first hydraulic motor decreases and the rotational speed of the drive shaft increases, and the amount of tilt of the first hydraulic motor becomes zero and remains fixed at zero, the tilt of the second hydraulic motor is maintained. Since the fixing to maximize the amount has been released, the amount of tilt of the second hydraulic motor decreases, and the rotation speed of the drive shaft increases. In addition, when the drive shaft is decelerated, the amount of tilt of the second hydraulic motor is maximized by the braking pressure while the amount of tilt of the first hydraulic motor remains zero, and a large braking torque is obtained. The performance is improved.
Thereafter, when the fixing of the tilt amount of the first hydraulic motor to zero is released, even if the tilt amount of the second hydraulic motor remains at the maximum,
The tilt amount of the first hydraulic motor increases and the rotation speed of the drive shaft decreases. Therefore, basically, the shift is controlled by the tilt amount of one of the two hydraulic motors, so that the accuracy of the shift control is improved.

A control device for a plurality of hydraulic motors and clutches according to a seventh aspect of the present invention is the control device according to the first aspect, wherein the clutch switching means for switching the clutch between a connected state and a free state, and a vehicle speed signal pressure proportional to the vehicle speed. When the vehicle speed is increased by inputting the vehicle speed signal pressure from the hydraulic vehicle speed detecting means for detecting the vehicle speed and the hydraulic vehicle speed detecting means, the tilt amount of the first hydraulic motor is substantially reduced when the vehicle speed signal pressure is equal to or less than the first predetermined value. When the vehicle speed signal pressure exceeds a first predetermined value, the amount of tilt of the first hydraulic motor is fixed to almost zero, and when the vehicle speed is reduced, the vehicle speed signal pressure is reduced to the first predetermined value. The tilt amount of the first hydraulic motor is fixed to substantially zero at a lower second predetermined value or more, and the tilt amount of the first hydraulic motor is fixed to substantially zero when the vehicle speed signal pressure falls below the second predetermined value. To release the signal pressure to zero Output, and, at the time of accelerating the vehicle speed,
A signal to connect the clutch before releasing the clutch to make the tilt amount of the first hydraulic motor substantially zero when the vehicle is decelerated when the vehicle speed is decelerated, after fixing the tilt amount of the first hydraulic motor to substantially zero and releasing the clutch. Control valve means for outputting pressure to the clutch switching means.

According to the seventh invention, the control valve means inputs the vehicle speed signal pressure from the hydraulic vehicle speed detecting means, and when the vehicle speed is increased, the control valve means determines the amount of tilt of the first hydraulic motor below the first predetermined vehicle speed. When the vehicle speed is decelerated, the fixing of releasing the tilt amount of the first hydraulic motor to substantially zero at a second vehicle speed or lower that is lower than the first predetermined vehicle speed is released. For this reason, the hunting of the control is prevented by making the first and second predetermined vehicle speeds different, and the tilt amount of the first hydraulic motor is fixed to 0 when the vehicle speed is reduced until it becomes lower than when the vehicle speed is increased. Because
As a result, the tilt amount of the first hydraulic motor at the time when the fixing of the tilt amount of the first hydraulic motor to zero is released is reduced, and the braking torque is reduced. Therefore, the deceleration shock can be prevented even if the acceleration performance at the time of speed increase is improved, in addition to the same operation and effect as the fourth invention. In addition, hydraulic control can be performed instead of electronic control, and the degree of freedom in selecting a control device is improved.

The control apparatus for a plurality of hydraulic motors and clutches according to an eighth aspect of the present invention is the control apparatus according to the seventh aspect, wherein the second tilting cylinder for controlling the tilting amount of the second hydraulic motor;
A second hydraulic pressure output control pressure of the second tilt cylinder is received by receiving the higher hydraulic pressure of the suction pipe and the discharge pipe of the hydraulic motor.
A servo valve; and a maximum tilt fixed valve for controlling the second servo valve so that the second tilt cylinder fixes the second hydraulic motor to the maximum tilt amount. The control valve means includes a first hydraulic motor. When the fixing of the tilting amount of the second hydraulic motor is released to a maximum value when the tilting amount of the second hydraulic motor is released to approximately zero, and when the tilting amount of the first hydraulic motor is It is characterized in that a signal pressure for releasing the fixing for maximizing the tilt amount of the motor is output to the maximum tilt fixed valve.

According to the eighth aspect, at the time of increasing the speed of the drive shaft, the fixing of the first hydraulic motor to the tilt amount of substantially zero is released even if the tilt amount of the second hydraulic motor remains at the maximum. Therefore, even if the amount of tilt of the first hydraulic motor is decreased and the rotational speed of the drive shaft is increased, and the amount of tilt of the first hydraulic motor is fixed to almost zero, the amount of tilt of the second hydraulic motor is reduced. Is released, the amount of tilt of the second hydraulic motor decreases, and the rotation speed of the drive shaft increases. In addition, when the drive shaft is decelerated, the amount of tilt of the second hydraulic motor is maximized by the braking pressure while the amount of tilt of the first hydraulic motor remains zero, and a large braking torque is obtained. The performance is improved. After that, even if the tilt amount of the second hydraulic motor remains at the maximum, the fixing of the tilt amount of the first hydraulic motor to almost zero is released, and the tilt amount of the first hydraulic motor increases to drive. The rotation speed of the shaft decreases. Therefore, basically, the shift is controlled by the tilt amount of one of the two hydraulic motors, so that the accuracy of the shift control is improved.

The control device for a plurality of hydraulic motors and clutches according to the ninth aspect of the present invention is the control apparatus according to the eighth aspect, wherein the tilting amount of the first hydraulic motor is fixed to a small tilting amount larger than 0 by a predetermined amount. A tilt-fixing means, and a small tilt-fixing valve for driving the small tilt-fixing means, wherein the control valve means changes the signal pressure for fixing the tilt amount of the first hydraulic motor to the small tilt amount by a small tilt. When outputting to the fixed valve, a signal pressure for fixing the tilt amount of the second hydraulic motor to the maximum is output to the maximum tilt fixed valve.

According to the ninth aspect, the tilt amount of the first hydraulic motor is fixed to a small tilt amount larger than 0 by a predetermined amount, and the tilt amount of the second hydraulic motor is fixed to a maximum. . Therefore, at this time, since the braking torque of the first hydraulic motor and the second hydraulic motor is large, overrun of the vehicle speed is prevented. Further, since the maximum tilt fixed valve is controlled by the signal pressure of the control valve means, the connection of the wiring including the connector is not sufficient at the time of maintenance and inspection as in the case where the maximum tilt fixed valve is an electromagnetic valve. Therefore, a contact failure caused by vibration of the vehicle is eliminated, and reliability for preventing overrun of the vehicle is improved.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The oil discharged from the hydraulic pump 16 driven by the engine 15 is supplied to the variable displacement first hydraulic motor 1 and the variable displacement second hydraulic motor 2 in parallel via the first main circuit 17 and the second main circuit 18. Connected to. An output shaft of the second hydraulic motor 2 is always connected to a drive shaft 3 for driving wheels of a vehicle (not shown) via a speed reducer 4, and an output shaft of the first hydraulic motor 1 is connected to a clutch 5 and a speed reducer 4.
Is connected to the drive shaft 3 via the. The pressure oil on the driving side of the first main circuit 17 or the second main circuit 18 is supplied to the first hydraulic motor 1 via the FR switching valve 6 which is switched by a hydraulic pressure from a not-shown forward / reverse operating valve (hereinafter referred to as an FR operating valve). A rod chamber 7a of a first tilt cylinder 7 for controlling the tilt amount;
The first pilot pressure receiving portion 8 a of the servo valve 8 is connected to the P port of the first servo valve 8, and the A port of the first servo valve 8 is connected to the bottom chamber 7 b of the first tilt cylinder 7.

The vehicle speed is classified into a Hi mode and a Lo mode. When the zero tilt fixed valve 11 that limits the permissible rotation speed in the Hi mode is in the shut-off position, the vehicle speed is proportional to the engine rotation speed supplied from the FR switching valve 6. The variable control pressure Pm is supplied via the shuttle valve 12 to the second pilot pressure receiving portion 8b of the first servo valve 8 which is larger than the first pilot pressure receiving portion 8a. The first servo valve 8 is connected to the P port according to the position where the biasing force of the driving-side pressure oil of the first pilot pressure receiving portion 8a and the control pressure of the second pilot pressure receiving portion 8b balances the spring force of the spring 8c. The depressurized oil is supplied to the A port to the bottom chamber 7b of the first tilt cylinder 7 to control the tilt amount of the first hydraulic motor 1.

The first main circuit 17 or the second main circuit 18
The high-pressure oil supplied via the shuttle valve 9 is supplied to the P port of the small tilt fixed valve 13 that limits the allowable rotation speed in the Lo mode, and the A port of the small tilt fixed valve 13 is connected to a stopper. The rod chamber of the stopper cylinder 14 is connected to the tank and the bottom chamber of the cylinder 14 is connected to the tank. When the small displacement fixing valve 13 is at the communication position between the P port and the A port, the piston rod 14a of the stopper cylinder 14 moves to the extended end to set the small displacement amount position of the first hydraulic motor 1. Further, when the small tilt fixing valve 13 is at the shutoff position between the P port and the A port, the piston rod 14a of the stopper cylinder 14 can move to the contracted end by an external force, and sets the zero tilt amount position of the first hydraulic motor 1. . As described above, when the small tilt fixing valve 13 is in the communication position between the P port and the A port and the first hydraulic motor 1 can reduce the tilt amount to the small tilt amount position, the Lo mode is set. Valve 13
Is at a position where the P port and the A port are shut off and the first hydraulic motor 1 can decrease the tilt amount to almost the zero tilt amount position.
i-mode.

When the zero tilt fixed valve 11 is in the communicating position,
The high-pressure oil of the first main circuit 17 or the second main circuit 18 supplied from the shuttle valve 9 via the communication position of the zero tilt fixed valve 11 is supplied via the shuttle valve 12 in preference to the variable control pressure Pm. Since the first servo valve 8 is supplied to the second pilot pressure receiving portion 8b, the opening of the first servo valve 8 communicating the P port and the A port is maximized. Therefore, the piston rod 7c of the first tilting cylinder 7 moves to the left by the pressure oil from the first servo valve 8 supplied to the bottom chamber 7b. Then, at the small tilt amount position or almost zero tilt amount position of the first hydraulic motor 1 set by the piston rod 14a, the stopper 7d contacts the piston rod 14a via the piston rod 7c, and the first hydraulic motor 1 It is fixed at the small tilting position of 1 or almost zero. Thus, 0
The first fixed valve 11, the first servo valve 8, the first tilt cylinder 7, the stopper 7d fixed to the first tilt cylinder 7, the small tilt fixed valve 13 and the stopper cylinder 14 make the first
The zero tilt fixing means 10 for fixing the tilt amount of the hydraulic motor 1 is configured.

On the other hand, the pressure oil supplied from the first main circuit 17 or the second main circuit 18 through the shuttle valve 29 is supplied to the second main circuit 17 or the second main circuit 18.
Second tilt cylinder 27 for controlling the tilt amount of hydraulic motor 2
, The first pilot pressure receiving portion 28a of the second servo valve 28, and the P port of the second servo valve 28, and the A port of the second servo valve 28 is connected to the bottom of the second tilt cylinder 27. It is connected to the chamber 27b.

A discharge port of a control pump 23 for discharging a constant control pressure Pm controlled to a constant pressure by a relief valve 22 is connected to the clutch 5 through a clutch switching valve 24 and a maximum tilt fixed valve. 21 through the second servo valve 2
8 is connected to the second pilot pressure receiving section 28b. Therefore, when the clutch switching valve 24 is in the cutoff position, no pressure oil is supplied to the clutch 5, so that the clutch 5 is connected by a spring (not shown) and the power of the first hydraulic motor 1 is transmitted to the drive shaft 3. When the clutch switching valve 24 is in the communication position, pressure oil is supplied to the clutch 5 so that the clutch 5
Is shut off, and the power of the first hydraulic motor 1 is not output to the drive shaft 3.

When the maximum tilt fixed valve 21 is in the shut-off position, no pressure oil is supplied to the second pilot pressure receiving portion 28b of the second servo valve 28, so that the pilot pressure of the first pilot pressure receiving portion 28a of the second servo valve 28 is The spool (not shown) of the second servo valve 28 moves to a position where the urging force of the second servo valve 28 and the spring force of the spring 28c balance. Depending on the spool position of the second servo valve 28, the P of the second servo valve 28
The pressure is reduced from the port to the port A, and pressure oil is supplied to the bottom chamber 27b of the second tilting cylinder 27 to set the tilting amount of the second hydraulic motor 2. When the maximum tilt fixed valve 21 is in the communicating position, pressure oil is supplied from the control pump 23 to the second pilot pressure receiving portion 28b of the second servo valve 28, thereby connecting the P port and the A port of the maximum tilt fixed valve 21. When the maximum opening is maximized, the second hydraulic motor 2 is fixed at the maximum tilt amount. As described above, the maximum tilt fixing means 20 for fixing the tilt amount (discharge capacity) of the second hydraulic motor 2 to the maximum by the maximum tilt fixing valve 21, the second servo valve 28, and the second tilt cylinder 27.
Is configured.

The controller 30 receives the Hi-Lo shift signal from the Hi-Lo shift switch 31 operated by the operator and the vehicle speed signal from the vehicle speed sensor 32, and receives the Hi-Lo shift signal and the vehicle speed signal as shown in FIG. The ON and OFF signals output to the solenoids of the valves 13, 11, 21 and 24 are calculated. A of the controller 30
The terminal is connected to the solenoid of the maximum tilt fixed valve 21, the terminal b is connected to the solenoid of the clutch switching valve 24, the terminal c is connected to the solenoid of the small tilt fixed valve 13, and the terminal d is connected to the solenoid of the 0 tilt fixed valve 11. 2 are connected so as to output an ON-OFF signal with respect to the vehicle speed as shown in detail in FIG.

In the graph of FIG. 2A, the horizontal axis represents the vehicle speed.
The vertical axis indicates the displacement amount of the first and second hydraulic motors by the discharge capacity (cc /
rev), and shows the relationship between the vehicle speed and the tilt amount of each hydraulic motor with respect to the discharge amount of the hydraulic pump when the accelerator is fully operated from a state where the vehicle is stopped, and does not relate to the load of the hydraulic motor. . For this reason, when the engine is partially operated, it moves in the direction of arrow Q in parallel. FIG.
(B) shows ON and O of solenoids of valves 13, 11, 21 and 24 shown in FIG. 1 with respect to the vehicle speed taken on the horizontal axis of (A).
It is a figure showing FF relation. FIG. 2 shows both (A) and (B)
Acceleration is indicated by a solid line, and deceleration is indicated by a broken line.

In FIG. 2B, when the controller 30 is inputting the Hi shift signal, the small tilt fixed valve 13 is turned off regardless of the vehicle speed both when increasing the speed and when decelerating.
Is set to In addition, when the vehicle speed is increased up to about 13 km / h, it can be freely switched between ON by a Hi shift signal and OFF by a Lo shift signal. If the vehicle speed is switched from Hi to Lo when the vehicle speed is about 18 km / h or more at the time of deceleration, it is automatically turned on when the vehicle speed is about 18 km / h or less. The zero tilt fixed valve 11 has a vehicle speed of about 16 k when the speed is increased.
It is turned off up to m / h and turned on when the vehicle speed exceeds about 16 km / h. When the vehicle speed is about 18km / h during deceleration,
N, OFF when the vehicle speed is lower than about 18 km / h.
The maximum tilt fixed valve 21 has a vehicle speed of about 16 km / h when the speed is increased.
Until the vehicle speed exceeds about 16 km / h. When the vehicle speed reaches approximately 18 km / h during deceleration, the vehicle automatically switches to ON when the vehicle speed exceeds approximately 18 km / h.
The clutch switching valve 24 has a vehicle speed of about 1 regardless of acceleration / deceleration.
It is turned on up to 9 km / h and turned off when the vehicle speed exceeds about 19 km / h.

Next, the operation of the first embodiment will be described. (1) Operation when increasing the speed of the vehicle (the vehicle speed shown in FIG. 2 is 16 km
When the Hi shift signal and the vehicle speed signal are inputted to the controller 30, the small tilt fixed valve 13 is turned off by the Hi shift signal as shown in FIG. The tilt fixed valve 11 is OFF, the maximum tilt fixed valve 21 is ON, and the clutch switching valve 24 is ON.

When the vehicle starts to be driven during forward movement (F), the driving pressure Pac of the first main circuit 17 which has become high is F
It is supplied to the rod chamber 7a of the first tilting cylinder 7, the first pilot pressure receiving portion 8a of the first servo valve 8, and the P port of the first servo valve 8 via the F position of the R switching valve 6. . The variable control pressure Pm proportional to the engine speed controlled by an accelerator pedal or the like (not shown) is supplied to the first servo valve 8 via the F position of the FR switching valve 6 and the shuttle valve 12.
Is supplied to the second pilot pressure receiving portion 8b. These second
The first servo valve 8 is controlled to a position where the variable control pressure Pm of the pilot pressure receiving portion 8b, the driving pressure Pac of the first pilot pressure receiving portion 8a, and the biasing force of the spring 8c are balanced.
Since Pm≪Pac when the vehicle starts to be driven,
An opening (hereinafter, referred to as a first opening) that connects the P port and the A port of the first servo valve 8 is reduced. Therefore, P
Since the pressure reduction amount of the port driving pressure Pac increases and the hydraulic pressure supplied to the bottom chamber 7b of the first tilting cylinder 7 is low, the first hydraulic motor 1 has the maximum tilting amount. Further, since the maximum tilt fixed valve 21 is ON, the control pressure of the control pump 23 acts on the second pilot pressure receiving portion 28b of the second servo valve 28. Therefore, an opening (hereinafter, referred to as a second opening) that connects the P port and the A port of the second servo valve 28 becomes large. Therefore, the driving pressure Pac of the P port is not reduced,
Since the hydraulic pressure supplied to the bottom chamber 27b of the second tilt cylinder 27 is high, the second hydraulic motor 2 is fixed at the maximum tilt amount. In this way, the vehicle starts to start with the maximum torque based on the maximum amount of tilt of the two hydraulic motors 1 and 2.

At the beginning of the start, most of the relief is performed by a relief valve (not shown) for limiting the maximum pressure of the driving pressure Pac, but the relief flow rate gradually decreases and the flow rate supplied to the hydraulic motors 1 and 2 increases. I do. Therefore, FIG.
As shown in (A), up to about 4 km / h, each hydraulic motor 1
The speed is increased even if the tilt amount of No. 2 is constant. Thereafter, the driving torque of the vehicle gradually decreases, and the driving pressure Pac decreases.
Since (the biasing force of Pm)> (the biasing force of Pac), and the first opening of the first servo valve 8 becomes large, the hydraulic pressure supplied from the A port to the bottom chamber 7b of the first tilting cylinder 7 increases. Therefore, the reduced driving pressure Pac is applied to the first piston 7
The piston rod 7c is moved to the left to reduce the tilt amount (discharge capacity D) of the first hydraulic motor 1. The vehicle speed is maintained at about 16
When the speed reaches km / h, the first hydraulic motor 1 has a substantially zero tilt amount.
At this time, since the stopper cylinder 14 is in the floating state, even if the stopper 7d abuts on the piston rod 14a, the tilt amount (discharge capacity D) of the first hydraulic motor 1 further becomes substantially zero. Continue to decrease.

(2) Operation when increasing the speed of the vehicle (high speed range where the vehicle speed shown in FIG. 2 exceeds 16 km / h) At the same time, as shown in FIG. 2, the small tilt fixed valve 13 is turned off by the Hi shift signal. As it is, the 0 tilt fixed valve 11 switches to ON and the maximum tilt fixed valve 21 switches to OFF for the high speed range.

The driving pressure Pac supplied through the zero tilt fixed valve 11 is supplied to the second pilot pressure receiving portion 8b of the first servo valve 8 via the shuttle valve 12, and drives the first pilot pressure receiving portion 8a. The control is performed until the first opening of the first servo valve 8 is maximized by overcoming the urging force of the pressure Pac and the urging force of the spring 8c. Therefore, the reduced driving pressure Pac is
It is also sent to the rod chamber 7a of the first tilt cylinder 7, but when it is sent from the A port of the first servo valve 8 to the bottom chamber 7b of the first tilt cylinder 7, the pressure receiving area of the rod chamber 7a and the bottom chamber 7b is increased. The piston rod 7c is moved to the left by the difference. At this time, since the small tilt fixed valve 13 is kept OFF, the piston rod 14 of the stopper cylinder 14
a is contracted, and the stopper 7 d fixed to the piston rod 7 c of the first tilt cylinder 7
Move until it touches a. For this reason, the tilt amount of the swash plate (not shown) of the first hydraulic motor 1 moves to approximately zero tilt amount, and the tilt amount (discharge capacity) of the first hydraulic motor 1 is fixed to approximately zero. Thereafter, when the vehicle speed reaches about 19 km / h, the clutch switching valve 24 is turned off and the drive shaft 3 is disconnected.

Since the maximum tilt fixed valve 21 is turned off, the second pilot pressure receiving portion 28b of the second servo valve 28 is turned off.
Since the control pressure of the control pump 23 does not act on the second tilting cylinder 27, the second opening of the second servo valve 28 decreases.
Of the bottom chamber 27b decreases. Therefore, the second hydraulic motor 2 is released from the fixed maximum tilt amount.

(3) Operation at the time of deceleration of the vehicle (high-speed region where the vehicle speed shown in FIG. 2 exceeds 16 km / h) As shown in FIG. Tilt fixed valve 13 is OFF, 0 tilt fixed valve 11 is ON, maximum tilt fixed valve 21 is OFF, clutch switching valve 2
4 remains OFF. For this reason, the first hydraulic motor 1 is fixed at a substantially zero tilt amount, but the second hydraulic motor 2 is released from being fixed at the maximum tilt amount, thereby increasing the braking pressure of the main circuit 28 due to deceleration. Pbr acts on the first pilot pressure receiving portion 28a of the second servo valve 28 via the shuttle valve 29 to maximize the second opening of the second servo valve 28. For this reason, the hydraulic pressure in the bottom chamber 27b of the second tilting cylinder 27 increases, and the second hydraulic motor 2 reaches the maximum tilting amount.
As shown by the broken line in FIG.
When the speed is reduced to 9 km / h, the clutch switching valve 24
After switching to N, the small tilt fixed valve 13 remains OFF, the zero tilt fixed valve 11 is turned OFF, and the maximum tilt fixed valve 21 is switched ON. Therefore, when the vehicle speed reaches about 19 km / h, the clutch 5 is connected, and then the first hydraulic motor 1 is released from being fixed to a tilt amount of almost zero.

(4) Operation at the time of deceleration of the vehicle (low speed region where the vehicle speed shown in FIG. 2 is 16 km / h or less) After the first hydraulic motor 1 is released from being fixed to a tilt amount of almost 0, the vehicle speed decreases. Accordingly, the driving pressure Pac starts to increase, and the first hydraulic motor 1 increases from the minimum displacement to the maximum displacement. Thus, the tilt amount of the first hydraulic motor 1 is zero.
The tilt amount is fixed to a small amount larger by a predetermined amount, and the tilt amount of the second hydraulic motor 2 is fixed to a maximum. Therefore,
At this time, the overrun of the vehicle is prevented since the combined braking torque of the first hydraulic motor and the second hydraulic motor is large. When the vehicle speed further decreases to 4 km / h or less, the first
The hydraulic motor also makes a maximum tilt, but the amount of oil relieved from a relief valve installed in a main circuit (not shown) increases, and the vehicle further decelerates.

The first hydraulic motor 1 and the second hydraulic motor 1
FIG. 3 shows the relationship between the rotation of the hydraulic motor 2 and the traction force. FIG.
Is displayed on the same scale as the vehicle speed in FIG.
The rotation of the first hydraulic motor 1 and the rotation of the second hydraulic motor 2 are coupled so as to be the same rotation by the reduction ratio of the speed reducer 4 and output to the drive shaft 3. The allowable rotation at the time of the zero tilt amount is the allowable rotation at the time of the Hi mode, and the allowable rotation at the time of the small tilt amount is the allowable rotation at the time of the Lo mode.

In FIG. 1, the first main circuit 17 and the second main circuit 18 for connecting the hydraulic pump 16 to the first hydraulic motor 1 and the second hydraulic motor 2 are shown as closed circuits, but are not limited thereto. It goes without saying that the present invention can be similarly applied to an open circuit instead of an open circuit.

A second embodiment of the present invention will be described with reference to FIGS. The control circuit diagrams of the second embodiment shown in FIGS.
In the first embodiment shown in FIG. 1, the zero tilt fixed valve 11 is 11A (the zero tilt fixed means 10 is 10A), and the small tilt fixed valve 13 is 13A.
A, the maximum tilt fixed valve 21 to 21A, the clutch switching valve 24 to 24A, and the controller 30 to control valve means 30A.
The vehicle speed sensor 32 is replaced with a hydraulic vehicle speed detecting means 32A. The other configuration is the same as that of the first embodiment, and the description is omitted. FIG. 6A is the same as FIG. 2A of the first embodiment, and a description thereof will be omitted.
(B) is a small tilt fixed valve 13A, zero tilt fixed valve 11A, tilt fixed control valve 11 with respect to the vehicle speed taken on the horizontal axis of (A).
B is a diagram showing the operation relationship of each valve of the clutch switching valve 24A, in which acceleration is indicated by a solid line and deceleration is indicated by a broken line.

The hydraulic vehicle speed detecting means 32A includes a vehicle speed detecting pump 32a driven by the speed reducer 4 and a vehicle speed detecting pump 32A.
A high-pressure selection valve 32b for selecting a vehicle speed signal pressure Pv to be discharged according to the direction of rotation of the high-pressure selection valve 32b;
9, a throttle 32c provided in a conduit connecting the
Valve 32d that draws oil into the vehicle speed detection pump 32a from the
And The hydraulic vehicle speed detection means 32A detects the vehicle speed based on a vehicle speed signal pressure Pv (proportional to the vehicle speed) generated when the oil discharged from the vehicle speed detection pump 32a drains through the hydraulic pressure selection valve 32b and the throttle 32c.

The control valve means 30A includes the tilt fixed control valve 11
B, Hi-Lo switching solenoid valve 13B and slow return valve 2
5 is provided. The tilt fixed control valve 11B uses the vehicle speed signal pressure Pv supplied via the slow return valve 25 as a pilot pressure, and as shown in FIG.
/ H until the vehicle speed reaches 16 km / h. When the vehicle speed is 16 km / h, the tilt fixed control valve 11B is immediately switched to the position b when the vehicle speed is increased, and is gradually switched to the position a when the vehicle speed is 16 km / h by the slow return valve 25 when the vehicle is decelerated. Tilt fixed control valve 11B
In the position a, the discharge port of the control pump 23 is connected to the inlet port of the maximum tilt fixed valve 21A, and the floating pilot pressure receiving portion of the small tilt fixed valve 13A and each pilot pressure receiving portion of the zero tilt fixed valve 11A are connected to the tank. Connect to 19. Further, the tilt fixed control valve 11B connects the discharge port of the control pump 23 with the inlet port of the clutch switching valve 24A and the small tilt fixed valve 13 at the position b.
A is connected to the pilot pressure receiving portion on the floating side of A and each pilot pressure receiving portion of the zero tilt fixed valve 11A, and the maximum tilt fixed valve 21A
Is connected to the tank 19.

The Hi-Lo switching solenoid valve 13B has a Hi-L
o When the solenoid is demagnetized by the shift switch 31, the position becomes Hi, and when the solenoid is excited, it becomes Lo. At the Hi position, the expansion-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portion of the maximum tilt fixed valve 21A are connected to the tank 19. At the Lo position, the discharge port of the control pump 23 is connected to the extension-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portion of the maximum tilt fixed valve 21A. In addition,
As shown in FIG. 6B, when the vehicle speed is 19 km / h or less, the clutch switching valve 24A is in the a position, and the vehicle speed is 19 km.
/ H, the position becomes b, and the outlet port is
Connected to. The outlet port of the maximum tilt fixed valve 21A is connected to the second pilot pressure receiving portion 28b of the second servo valve 28.

The operation of the second embodiment will be described. (1) Operation when increasing the speed of the vehicle (the vehicle speed shown in FIG. 6 is 16 km
When the Hi-Lo switching solenoid valve 13B is demagnetized to the Hi position, the extension-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portion of the maximum tilt fixed valve 21A drain. Further, since the vehicle speed signal pressure Pv is low, the tilt fixed control valve 11B and the clutch switching valve 24A are both at the position a.
In this way, the control circuit is in the state shown in FIG. 4, so that the floating pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portions of the zero tilt fixed valve 11A are drained. For this reason, the zero tilt fixed valve 11A is in the shut-off position, and the small tilt fixed valve 13A is switched to the floating position by the spring force, thereby bringing the stopper cylinder 14 into the floating state. In addition, the clutch 5 is connected to drain the clutch oil pressure via the position a of the clutch switching valve 24A. Further, the constant control pressure Pc is supplied to the second pilot pressure receiving portion 28b of the second servo valve 28 via the a position of the tilt fixed control valve 11B and the Hi position of the maximum tilt fixed valve 21A. The second opening for communicating the P port and the A port of the first port increases.

As shown in FIG. 4, when the vehicle starts to be driven at the time of forward (F), the high pressure first main circuit 17 is activated.
The driving pressure Pac of the first through the F position of the FR switching valve 6
It is supplied to the rod chamber 7 a of the tilt cylinder 7, the first pilot pressure receiving portion 8 a of the first servo valve 8, and the P port of the first servo valve 8. A variable control pressure Pm proportional to the engine speed controlled by an accelerator pedal or the like (not shown) is applied to the F position of the FR switching valve 6 and the second pilot pressure receiving portion 8b of the first servo valve 8 via the shuttle valve 12. Supplied. The first servo valve 8 is controlled to a position where the variable control pressure Pm of the second pilot pressure receiving portion 8b, the driving pressure Pac of the first pilot pressure receiving portion 8a, and the biasing force of the spring 8c are balanced. When the vehicle starts to be driven, P
Since m≪Pac, the first opening communicating the P port and the A port of the first servo valve 8 becomes small. Therefore, since the driving pressure Pac of the P port is reduced and the hydraulic pressure supplied to the bottom chamber 7b of the first tilt cylinder 7 is low, as shown in FIG. Amount. Further, since the second opening of the second servo valve 28 increases, the driving pressure Pac of the P port is supplied to the bottom chamber 27b of the second tilt cylinder 27 without being reduced, so that as shown in FIG. Then, the second hydraulic motor 2 is fixed at the maximum tilt amount. Therefore, since the two hydraulic motors 1 and 2 have the maximum amount of tilt, the vehicle starts to start with the maximum torque. If the constant control pressure Pc is set to be larger than the maximum value of the variable control pressure Pm, the zero tilt fixed valve 11A is omitted and the tilt fixed control valve 1 is omitted.
The 1B outlet port may be connected directly to the shuttle valve 12.

At the beginning of the start, most of the relief is performed by a relief valve (not shown) for limiting the maximum driving pressure Pac, but the relief flow rate gradually decreases and the flow rate supplied to the hydraulic motors 1 and 2 increases. I do. Therefore, FIG.
As shown in (A), up to about 4 km / h, each hydraulic motor 1
The speed is increased even if the tilt amount of No. 2 is constant. Thereafter, the driving torque of the vehicle gradually decreases, and the driving pressure Pac decreases.
Since (the biasing force of Pm)> (the biasing force of Pac), and the first opening of the first servo valve 8 becomes large, the hydraulic pressure supplied from the A port to the bottom chamber 7b of the first tilting cylinder 7 increases. For this reason, the reduced drive pressure Pac is also sent to the rod chamber 7a of the first piston 7, but the piston rod 7c is moved to the left due to the area difference, and the tilt amount of the first hydraulic motor 1 (discharge capacity D ) To decrease. At this time, since the stopper cylinder 14 is in the floating state, the stopper 7
Even if d comes into contact with the piston rod 14a, it continues to decrease until the tilt amount (discharge capacity D) of the first hydraulic motor 1 becomes substantially zero. At this time, the control valve means 30A sets the vehicle speed signal pressure Pv supplied through the slow return valve 25 to the value shown in FIG.
As shown in (B), the tilt amount is fixed to almost 0 at 16 km / h.

At this time, the amount of tilt of the first hydraulic motor 1 is 0
Until the predetermined small tilt amount larger than the tilt amount is reached,
When the solenoid of the Hi-Lo switching solenoid valve 13B is excited, L
In the o mode, the state shown in FIG. 5 is established, and the constant control pressure Pc is supplied to the extension-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portion of the maximum tilt fixed valve 21A. Therefore, the small tilt fixed valve 13A is switched to the extended position, and the stopper 7d abuts on the piston rod 14a extended so as to define the small tilt amount of the first hydraulic motor 1, and as shown in FIG. As shown, the tilt amount (discharge capacity D) of the first hydraulic motor 1 is reduced to the small tilt amount and is fixed to the small tilt amount. For this reason, as compared with the Hi mode, the first hydraulic motor 1 is slower by a larger amount of displacement (discharge capacity D),
High torque. At the same time, since the constant control pressure Pc is supplied to the second pilot pressure receiving portion 28b of the second servo valve 28, the amount of displacement (discharge capacity D) of the second hydraulic motor 2 increases until it reaches the maximum amount of displacement. Fixed. For this reason, the second hydraulic motor 2 also has a low speed and a high torque. As described above, when the vehicle speed is increased to about 13 km / h, the vehicle can be freely switched between the floating position and the extended position by the Hi-Lo mode signal.

(2) Operation when increasing the speed of the vehicle (high speed range where the vehicle speed exceeds 16 km / h shown in FIG. 6) The Hi-Lo switching valve 13B and the maximum tilt fixed valve 21A are Hi.
When the vehicle speed signal pressure Pv becomes high while being switched to the position, the clutch switching valve 24A becomes the b position after the tilt fixed control valve 11B has reached the b position. Therefore, the constant control pressure PC is supplied to the floating-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portions of the zero tilt fixed valve 11A. In addition, the extension-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot pressure receiving portions of the maximum tilt fixed valve 24A drain. Accordingly, as shown in FIG. 6B, the zero tilt fixed valve 11A is switched to the communication position, and the small tilt fixed valve 13A is switched to the floating position to bring the stopper cylinder 14 into the floating state. Also, the second servo valve 28
The pilot pressure receiving portion 28b is connected to the Hi of the maximum tilt fixed valve 21A.
Drain via the position and the b position of the tilt fixed control valve 11B. For this reason, as shown in FIG.
Is released from the maximum tilt amount.

When the 0 tilt fixed valve 11A is in the communicating position,
The driving pressure Pac is supplied to the second pilot pressure receiving portion 8b of the first servo valve 8 through the communication position between the shuttle valve 9 and the zero tilt fixed valve 11A and the shuttle valve 12, but the second pilot pressure receiving portion 8b Is larger than the first pilot pressure receiving portion 8a, the driving pressure Pac of the first pilot pressure receiving portion 8a
The control is performed until the first opening of the first servo valve 8 is maximized by overcoming the urging force of the first servo valve 8 and the urging force of the spring 8c. Therefore, the driving pressure Pac is applied to the rod chamber 7 of the first tilt cylinder 7.
a, but also from the A port of the first servo valve 8 to the bottom chamber 7b of the first tilting cylinder 7, the piston rod 7c moves to the left due to the pressure receiving area difference between the rod chamber 7a and the bottom chamber 7b. Move. At this time, since the small tilt fixing valve 13A remains in the floating position, the piston rod 14a of the stopper cylinder 14 is pushed by the stopper 7d fixed to the piston rod 7c of the first tilt cylinder 7, and tilts almost 0. The first hydraulic motor 1 is moved to the displacement amount and the displacement amount (discharge capacity) of the first hydraulic motor 1 is fixed to substantially zero. After that, when the vehicle speed was 19
When the speed reaches km / h, a constant control pressure PC is supplied to the clutch 5 through the position b of the clutch switching valve 24A, so that the clutch becomes free, and as shown in FIG. Alone drives the vehicle.

(3) Operation at the time of deceleration of the vehicle (high-speed range where the vehicle speed exceeds 16 km / h shown in FIG. 6) Like the operation at the time of increasing the speed of the vehicle (high-speed range), the Hi-Lo switching solenoid valve 13B and the When the maximum tilt fixed valve 21A is in the Hi position,
The zero tilt fixed valve 11A is in the communicating position, and the small tilt fixed valve 13A
Remains at the floating position, and the clutch switching valve 24A remains switched to the position b. Therefore, the first hydraulic motor 1 is fixed at a tilt amount of substantially 0, but the second hydraulic motor 2 is released from being fixed at the maximum tilt amount and is free. Accordingly, the braking pressure Pbr of the second main circuit 28, which is increased by the deceleration of the vehicle,
Acts on the first pilot pressure receiving portion 28a of the second servo valve 28 via the shuttle valve 29 to cause the second servo valve 28
Maximize opening. For this reason, the hydraulic pressure in the bottom chamber 27b of the second tilting cylinder 27 increases, and as shown in FIG. 6A, the second hydraulic motor 2 reaches the maximum tilting amount (indicated by a broken line) and the second hydraulic pressure The vehicle is decelerated with the maximum braking torque of the motor 2.

In this state, when the solenoid of the Hi-Lo switching solenoid valve 13B is excited to be in the Lo mode, the constant control pressure Pc is applied to the extension-side pilot pressure receiving portion of the small tilt fixed valve 13A and the pilot of the maximum tilt fixed valve 21A. It is supplied to the pressure receiving part. Further, the constant control pressure Pc is also supplied to the floating-side pilot pressure receiving portion of the small tilt fixed valve 13A and each pilot pressure receiving portion of the zero tilt fixed valve 11A. For this reason, the small tilt fixed valve 1
3A is switched to the floating position, the stopper 7d abuts on the extended piston rod 14a, and the tilt amount (discharge capacity D) of the first hydraulic motor 1 is reduced and fixed until it becomes zero tilt amount. At the same time, the constant control pressure Pc is
Is supplied to the second pilot pressure receiving section 28b,
The displacement amount (discharge capacity D) of the hydraulic motor 2 is increased and fixed until it reaches the maximum displacement amount. For this reason, the second hydraulic motor 2 also has a low speed and a high torque. Further, as shown in FIG. 6B, at the time of deceleration, when the vehicle speed is about 19 km / h or less, the clutch hydraulic pressure drains through the position a of the clutch switching valve 24A, so that the clutch 5 is connected. Control valve means 30A
Is the hydraulic vehicle speed detecting means 3 through the slow return valve 25
The vehicle speed signal pressure Pv is input from 2A. Therefore, when the vehicle speed is reduced, the vehicle speed signal pressure Pv when the pilot pressure of the tilt fixed control valve 11B is 16 km / h is equal to the first vehicle speed 1
The second vehicle speed is lower than 6 km / h. The second vehicle speed is a value determined according to the orifice diameter of the slow return valve 25, the deceleration of the vehicle speed, and the like, and is 15 km / h in the second embodiment. Note that at a vehicle speed of 15 km / h or more, L
When switching to the o mode, the tilt fixed control valve 11B
Switches to position a, but is the same as described above, and a detailed description is omitted.

(4) Operation at the time of deceleration of the vehicle (low speed range where the vehicle speed is 16 km / h or less as shown in FIG. 6) The vehicle speed is reduced to 15 km / h (the pilot pressure of the tilt fixed control valve 11B is 16 km / h). Then, since the tilt fixed control valve 11B is switched to the position a, the control circuit is in the state of FIG. 4 similarly to the operation at the time of increasing the speed (low speed range) of the vehicle described in the above (3). As shown in FIG. 6B, when the vehicle speed is 1
When the speed drops to 5 km / h, the first hydraulic motor 1 is released from being fixed so that the tilt amount is almost zero. In this way, the fixing of the first hydraulic motor 1 to make the amount of tilt almost zero is released up to 16 km / h when the vehicle is accelerating, but 15 km / h when decelerating the vehicle. h. As described above, the first vehicle speed (16 km / h) for switching from the release of fixing of the 0 tilt amount to the fixing at the time of increasing the speed and the second vehicle speed (15 km / h) for switching from the fixing of the 0 tilt amount to the fixing release at the time of deceleration
h), control hunting is prevented. At the time of releasing the fixing of the first hydraulic motor 1 so that the amount of tilt of the first hydraulic motor 1 becomes substantially zero when the vehicle speed is reduced (about 15 km /
The tilt amount of the first hydraulic motor 1 in h) is smaller than that at the time of increasing the speed, and the braking torque is reduced. Therefore, even if the acceleration performance at the time of increasing the speed is improved, the deceleration shock can be prevented.
In addition, since the hydraulic control can be performed instead of the electronic control, the degree of freedom in selecting the control device is improved. In this manner, the zero tilt fixed valve 11A is at the shut-off position, and the small tilt fixed valve 13A is switched to the floating position by the spring force, so that the stopper cylinder 14 is in the floating state. After the first hydraulic motor 1 is released from being fixed to a tilt amount of almost 0, the driving pressure Pac starts to increase as the vehicle speed decreases.
As shown in (A), the first hydraulic motor 1 increases from the minimum displacement to the maximum displacement. Therefore, the second hydraulic motor 2
The vehicle is decelerated by increasing the amount of displacement (discharge capacity D) of the first hydraulic motor 1 even if is maintained at the maximum amount of displacement. When the vehicle speed becomes 4 km / h or less, both the first and second hydraulic motors are tilted to the maximum, but the amount of oil relieved from a relief valve installed in a main circuit (not shown) increases and the vehicle further decelerates.

It should be noted that the vehicle speeds 13, 15, 16, and 1 are used to make the description of the first and second embodiments easy to understand.
The values of 8, 19 km / h are not limited to these values as long as the magnitude relation is satisfied. Also,
The relationship between the respective rotational speeds of the first and second hydraulic motors and the tractive force with respect to the vehicle speed is the same as in the first embodiment shown in FIG.

As described above, according to each of the embodiments, when the first hydraulic motor is fixed to the state of almost zero tilt, the amount of oil discharged from the hydraulic pump is supplied only by the second hydraulic motor and the drive shaft is driven. Is driven only by the second hydraulic motor. Therefore, the first
Although the torque of the drive shaft decreases by an amount corresponding to the zero tilt of the hydraulic motor, the rotation speed of the second hydraulic motor (that is, the drive shaft) increases by the amount of oil that drives the first hydraulic motor. Therefore, unlike the prior art, there is no need to provide a communication / shutoff valve, so that high torque / low speed drive and low torque / high speed drive can be obtained at a compact and low cost. Further, it is possible to reliably prevent a shift shock and a loss of load of the hydraulic motor.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram according to a first embodiment of the present invention.

FIG. 2 (A) is a discharge capacity D of each hydraulic motor shown in FIG. 1;
FIG. 3B is a diagram showing the relationship between the vehicle speed and the vehicle speed V. FIG. 3B is a diagram showing the relationship between each valve and the vehicle speed.

FIG. 3 is a diagram showing a relationship between a rotational speed and a tractive force of each hydraulic motor shown in FIG. 1 and a vehicle speed V;

FIG. 4 is a control circuit diagram (Hi) according to a second embodiment of the present invention.
Mode).

FIG. 5 is a control circuit diagram (Lo) according to a second embodiment of the present invention;
Mode).

6 (A) is a diagram showing a discharge capacity D of each hydraulic motor shown in FIG. 4;
FIG. 3B is a diagram showing the relationship between the vehicle speed and the vehicle speed V. FIG. 3B is a diagram showing the relationship between each valve and the vehicle speed.

FIG. 7 is a control circuit diagram of a conventional hydraulic motor and clutch control device.

8 is a diagram showing a relationship (Lo mode) between the displacement D of the hydraulic motor shown in FIG. 7 and the vehicle speed V. FIG.

9 is a diagram showing a relationship (Hi mode) between the displacement D of the hydraulic motor shown in FIG. 7 and the vehicle speed V.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st hydraulic motor, 2 ... 2nd hydraulic motor, 3 ... Drive shaft, 4 ... Reduction gear, 5 ... Clutch, 6 ... FR switching valve, 7 ...
1st tilt cylinder, 7d ... stopper, 8 ... first servo valve, 8c ... spring, 9 ... shuttle valve, 10 ... 0 tilt fixing means, 11, 11A ... 0 tilt fixing valve, 11B ... tilt fixing control Valve: 12: Shuttle valve, 13, 13A: Small tilt fixed valve, 13B: Hi-Lo switching valve, 14: Stopper cylinder, 14a: Piston rod, 15: Engine, 16:
Hydraulic pump, 17: first main circuit, 18: second main circuit, 1
9 ... tank, 20 ... maximum tilt fixing means, 21, 21A ...
Maximum tilt fixed valve, 22: relief valve, 23: control pump, 24, 24A: clutch switching valve, 25: slow return valve, 27: second tilt cylinder, 28: second servo valve, 29: shuttle valve, 30 ... controller, 30A ...
Control valve means, 31 ... Hi-Lo shift switch, 32 ...
Vehicle speed sensor, 32A: hydraulic vehicle speed detection means, 32a: vehicle speed detection pump, 32b: high pressure selection valve, 32c: throttle, 3
2d: suction valve, Pv: vehicle speed signal pressure, Pac: drive pressure, Pbr
... braking pressure, Pc: constant control pressure, Pm: variable control pressure.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masanori Ikari 1-9-9 Minamidai, Kawagoe-shi, Saitama Komatsu Ltd. Construction Equipment Second Development Center

Claims (9)

[Claims] An output of a plurality of hydraulic motors drives one drive shaft, and one of the plurality of hydraulic motors drives a drive shaft via a clutch. A second hydraulic motor (2) constantly connected to the shaft (3), a variable displacement first hydraulic motor (1) connected to the drive shaft (3) via a clutch (5), and a first hydraulic motor; First tilt control means (7, 8) for controlling the tilt amount of the first hydraulic motor (1) in response to the drive side hydraulic pressure (Pac) of the motor (1);
A plurality of zero-tilt fixing means (10, 10A) for fixing the amount of tilt of the first hydraulic motor (1) in a state where (1) is controlled to a substantially zero tilt amount. Control device for hydraulic motor and clutch. 2. The first tilt control means according to claim 1,
(7,8) is a first hydraulic motor (1) that controls the tilt amount of the first hydraulic motor (1).
Tilt cylinder (7) and hydraulic pressure on the drive side of the first hydraulic motor (1)
(Pac), and a first servo valve (8) for outputting the control pressure of the first tilt cylinder (7).
The zero tilt fixing means (10) for securely fixing the tilt amount to approximately zero when (7) is substantially zero tilt amount is provided by the first tilt cylinder.
(7) is a zero tilt fixed valve (11) for controlling the first servo valve (8) in a direction to decrease the tilt amount of the first hydraulic motor (1);
A control device for a plurality of hydraulic motors and clutches, comprising stopper means (7d, 14a) for stopping the tilt cylinder (7) at a position of approximately zero tilt amount. 3. The method according to claim 2, wherein the stopper means (7d, 14
a) includes a stopper (7d) fixed to the piston rod (7c) of the first tilt cylinder (7), and a stopper cylinder (14) having a piston rod (14a) abutting on the stopper (7d). A control device for a plurality of hydraulic motors and clutches, characterized in that: 4. A clutch switching means (24) for switching a clutch (5) between a connected state and a free state according to any one of claims 1 to 3, and a zero tilt fixed when the speed of the drive shaft (3) is increased. By means (10), the tilt amount of the first hydraulic motor (1) is reduced to almost zero.
And the clutch (5) is released, and when the drive shaft is decelerated, the tilt amount of the first hydraulic motor (1) is reduced to almost zero.
Controller (30) that outputs a command to connect the clutch (5) to the clutch switching means (24) before releasing the lock
And a control device for a plurality of hydraulic motors and clutches. 5. A clutch switching means (24) for switching a clutch (5) between a connected state and a free state according to claim 1.
And a rotation sensor (32) that detects the rotation speed of the drive shaft (3)
And a rotation speed signal of the drive shaft (3) from the rotation sensor (32). When the speed of the drive shaft (3) is increased, the first hydraulic motor (1) is driven when the drive shaft (3) is lower than the first predetermined rotation speed. ) Is released from being fixed to substantially zero, and when the drive shaft (3) exceeds the first predetermined rotation speed, the displacement of the first hydraulic motor (1) is fixed to substantially zero, and When the drive shaft (3) decelerates, the drive shaft (3) fixes the tilt amount of the first hydraulic motor (1) to substantially 0 at a speed equal to or higher than the second predetermined rotation speed, and the drive shaft (3) moves to the second predetermined rotation speed. When the rotation speed falls below the rotation speed, the amount of tilt of the first hydraulic motor (1) becomes almost zero.
Is output to the zero tilt fixing means (10), and when the speed of the drive shaft (3) is increased, the first hydraulic motor
After fixing the tilt amount of (1), release the clutch, and at the time of deceleration of the drive shaft (3), before releasing the fixing of the first hydraulic motor (1) to make the tilt amount almost zero, Clutch (5)
And a controller (30) for outputting a command to connect the clutches to the clutch switching means (24). 6. The second hydraulic motor (2) according to claim 5, wherein
A second tilting cylinder (27) for controlling the amount of tilting of the second tilting cylinder (27) according to the higher oil pressure of the suction line and the discharge line of the second hydraulic motor (2). The second servo valve (28) for outputting the control pressure and the second servo valve so that the second tilt cylinder (27) fixes the second hydraulic motor (2) to the maximum tilt amount.
And a maximum tilt fixed valve (21) for controlling the first hydraulic motor (28) when the drive shaft (3) is accelerated.
When releasing the tilting amount of (1) to almost zero, the tilting amount of the second hydraulic motor (2) is fixed to the maximum, and the tilting amount of the first hydraulic motor (1) is almost zero. When the drive shaft (3) is decelerated, the signal for releasing the fixation that maximizes the tilt amount of the second hydraulic motor (2) is released.
When the tilting amount of (1) is fixed to almost zero, the fixing of the second hydraulic motor (2) to maximize the tilting amount is released, and the tilting amount of the first hydraulic motor (1) is reduced to almost zero. A plurality of hydraulic motors, wherein a signal for fixing the tilt amount of the second hydraulic motor (2) to a maximum is output to the maximum tilt fixed valve (21) when releasing the fixing of the tilt amount. And clutch control device. 7. A clutch switching means (24) for switching a clutch (5) between a connected state and a free state according to claim 1.
A), hydraulic vehicle speed detecting means (32A) for detecting the vehicle speed with a vehicle speed signal pressure (Pv) proportional to the vehicle speed, and hydraulic vehicle speed detecting means (3
2A) from the vehicle speed signal pressure (Pv)
When the vehicle speed signal pressure (Pv) is equal to or less than the first predetermined value, the first hydraulic motor (1)
Is released, and when the vehicle speed signal pressure (Pv) exceeds a first predetermined value, the displacement of the first hydraulic motor (1) is fixed to substantially zero, and the vehicle speed is reduced. When the vehicle is decelerated, when the vehicle speed signal pressure (Pv) is equal to or higher than a second predetermined value that is lower than the first predetermined value, the amount of tilt of the first hydraulic motor (1) is fixed to approximately 0,
When the vehicle speed signal pressure (Pv) falls below the second predetermined value, a signal pressure for releasing the first hydraulic motor (1) from fixing the tilt amount to almost zero is output to the zero tilt fixing means (10A), In addition, when increasing the vehicle speed, the amount of tilt of the first hydraulic motor (1) is fixed to almost 0, and then the clutch (5) is released.
Before releasing the tilting amount of the first hydraulic motor (1) to almost zero, the control valve means (30A) for outputting the signal pressure for connecting the clutch (5) to the clutch switching means (24A) is provided. A control device for a plurality of hydraulic motors and clutches, comprising: 8. The second hydraulic motor (2) according to claim 7, wherein
A second tilt cylinder (27) for controlling the amount of tilt of the second hydraulic cylinder (27) and a second hydraulic cylinder (27) receiving the higher oil pressure of the suction pipe and the discharge pipe of the second hydraulic motor (2). A second servo valve (28) for outputting the control pressure of the second servo valve (28) and a second servo valve (28) so that the second tilt cylinder (27) fixes the second hydraulic motor (2) to the maximum tilt amount. A maximum tilt fixed valve (21A) to be controlled, and the control valve means (30A) reduces the tilt amount of the first hydraulic motor (1) to almost zero.
When the fixing is released, the tilt amount of the second hydraulic motor (2) is fixed to the maximum, and when the tilt amount of the first hydraulic motor (1) is fixed to almost zero, the second hydraulic motor (2) is fixed. (2) The signal pressure for releasing the lock that maximizes the tilt amount of the maximum tilt fixed valve (21
A) A control device for a plurality of hydraulic motors and clutches, characterized in that the output is output to the control unit. 9. The first hydraulic motor (1) according to claim 8, wherein
Tilting fixing means (14, 14a, 7d) for fixing the tilting amount to a small tilting amount larger than 0 by a predetermined amount, and small tilting fixing means (14, 14
a, 7d) for driving the first hydraulic motor (1) at a small tilt amount. The control valve means (30A) reduces the signal pressure for fixing the tilt amount of the first hydraulic motor (1) to the small tilt amount. When outputting to the tilt fixed valve (13A), a signal pressure for fixing the tilt amount of the second hydraulic motor (2) to the maximum is output to the maximum tilt fixed valve (21A).