JP2001324015A - Transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that in HST having a fixed displacement motor, power loss is large, at loading and reproducibility of speed is bad, and the power transmission efficiency in low speed operation is remarkably lowered so that it is necessary to provide an auxiliary transmission. SOLUTION: This transmission is a hydraulic continuously variable transmission 9 provided with an HST(hydro static transmission formed by a pair of a variable displacement pump 3 and a variable displacement motor 4. In a low speed operation, a motor displacement Vm is made maximum and a pump displacement Vp is changed by an actuator 6 for a pump to change the speed, while in high speed operation, the pump displacement Vp is made maximum and the motor displacement Vm is changed by the actuator 7 for the motor to change the speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic continuously variable transmission equipped with a variable displacement pump and a variable displacement motor.

[0002]

2. Description of the Related Art Conventionally, a hydraulic continuously variable transmission incorporating an HST (hydrostatic transmission) comprising a variable displacement pump and a constant displacement motor has been used as a main transmission such as a tractor. The shift is performed by operating the inclination angle of a swash plate provided in the variable displacement pump.

As shown in FIG. 13, a hydraulic continuously variable transmission 20 has an HST 21 composed of a variable displacement pump 3 and a constant displacement motor 23. The input shaft 11 is inserted into the variable displacement pump 3. The output shaft 12 is inserted into the constant displacement motor 23. The input shaft 11 is connected to the crankshaft of the engine 1 so that the driving force of the engine 1 can be input to the variable displacement pump 3. Further, the swash plate provided in the variable displacement pump 3 is connected to the speed change means 24, and the inclination angle of the swash plate can be changed by operating the speed change means 24. Each of the variable displacement pump 3 and the constant displacement motor 23 is provided with two discharge ports,
Each discharge port is connected by oil passages 26a and 26b to form a closed circuit. Thus, the mechanical power from the input shaft 11 is output as hydraulic power by the variable displacement pump 3,
The oil is transmitted to the constant displacement motor 23 through the oil passages 26a and 26b. Then, it is outputted again from the output shaft 12 as mechanical power by the constant displacement motor 23.

[0004]

In the above-mentioned HST, although the agricultural tractor needs to run at a constant speed, the power loss when a load is applied is large, and the reproducibility of the speed is poor. In addition, the power transmission efficiency at a low speed is significantly reduced.
Will be enlarged. For this reason, it is necessary to provide the tractor with an auxiliary transmission in addition to the HST. As shown in FIG. 13, the auxiliary transmission 25 is provided on the output shaft 12 side of the HST 21.
Is provided.

[0005]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. In other words, the present invention provides a transmission having a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the displacement of the variable displacement motor is maximized at a low speed, The speed is changed by changing the displacement of the pump by a pump actuator of the pump. At high speed, the displacement is changed by maximizing the displacement of the pump and changing the displacement of the motor by the actuator for the motor.

According to a second aspect of the present invention, an input speed detecting means for detecting a speed of an input shaft of the variable displacement pump, an output speed detecting means for detecting a speed of an output shaft of the variable capacity motor, Rotation speed target value setting means, comprising the actuator, a control device for controlling these,
The motor actuator and the pump actuator are operated and controlled so that the output rotation speed approaches a target value.

According to a third aspect of the present invention, there is provided a transmission having a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the input rotation for detecting the rotation speed of the input shaft of the variable displacement pump is provided. Number detection means, output rotation number detection means for detecting the rotation number of the output shaft of the variable displacement motor,
Output speed target value setting means, a motor actuator and a pump actuator, and a control device for controlling the same are detected, the current value of the output speed is detected, and the motor actuator is operated to change the displacement of the motor. Then, control is performed to bring the current value closer to the target value within a certain range.

According to a fourth aspect of the present invention, there is provided a transmission having a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the input for detecting the rotation speed of the input shaft of the variable displacement pump is provided. Rotation speed detection means, output rotation speed detection means for detecting the rotation speed of the output shaft of the variable displacement motor, output rotation speed target value setting means, motor actuator and pump actuator, and a control device for controlling these In response to a change in the input rotation speed, the motor actuator and the pump actuator are driven to change the displacement of the motor and the displacement of the pump, and control is performed so that the output rotation speed matches the target output rotation speed. Things.

According to a fifth aspect of the present invention, the minimum value of the displacement of the motor can be set, and the displacement of the motor is controlled to be equal to or more than the minimum value, thereby limiting the output speed to a certain upper limit or less.

According to a sixth aspect of the present invention, the output displacement is detected to change the displacement of the motor and the displacement of the pump to the target output revolution, and the displacement of the motor and the pump in response to a change in the input revolution. Two or more types of control are selected and controlled so that control is performed to change the displacement and set the target output speed, and to change the minimum value of the motor displacement to a value equal to or less than the maximum output speed.

In the present invention, a plurality of the variable displacement pumps and the variable displacement motors are respectively arranged in parallel, and a switching device is provided for each of the input port and the output port of each of the variable displacement pumps and the variable displacement motors, and can be selectively used. It is what was constituted.

[0012]

Next, embodiments of the present invention will be described.
FIG. 1 is a circuit diagram showing a variable displacement pump / variable displacement motor type HST, and FIG. 2 is a diagram showing a relationship between speed change and motor displacement / pump displacement, and a swash plate in the variable displacement pump / variable displacement motor HST. FIG. 3 is a diagram showing the magnitude of the inclination angle, FIG. 3 is a diagram showing a relationship between a speed ratio and a motor displacement / pump displacement in a variable displacement pump / variable displacement motor type HST, and FIG. FIG. 5 is a diagram showing a control procedure in a second embodiment, and FIG. 6 is a diagram showing a control procedure in a variable displacement pump / variable displacement motor type HST when the motor displacement is not maximized. , FIG. 7 is a diagram showing a control procedure in a third embodiment, and FIG. 8 is a diagram showing a control procedure in a fourth embodiment. FIG. 9 is a diagram showing a control procedure in the fifth embodiment, and FIG. 10 is a diagram showing a speed ratio and a motor in a variable displacement pump / variable displacement motor type HST when upper and lower limits are given to the motor displacement. FIG. 11 is a diagram showing the relationship between displacement and pump displacement.
12 is a circuit diagram showing an HST provided with a plurality of variable displacement pumps and a plurality of variable displacement motors. FIG. 12 is a control circuit diagram of a switching valve in a sixth embodiment, and FIG. 13 is a variable displacement pump / constant displacement motor. FIG. 3 is a circuit diagram showing a type HST.

As shown in FIG. 1, a hydraulic continuously variable transmission 9 according to the present embodiment has an HST comprising an axial variable displacement pump 3 and an axial variable displacement motor 4.
(Hydrostatic transmission) 10. The input shaft 11 is inserted into the variable displacement pump 3, and the output shaft 12 is inserted into the variable displacement motor 4. Input shaft 11 is engine 1
And the driving force of the engine 1 can be input to the variable displacement pump 3. The swash plate 3a provided on the variable displacement pump 3 is connected to a pump actuator 6, and the swash plate 4a provided on the variable displacement motor 4 is connected to a motor actuator 7. The swash plate 3a of the variable displacement pump 3 and the swash plate 4a of the variable displacement motor 4 are configured to be able to change the tilt angle by operating the pump actuator 6 and the motor actuator 7, respectively. However, the actuator is constituted by a cylinder, a motor, a solenoid, or the like, and is not limited.

The variable displacement pump 3 and the variable displacement motor 4 are each provided with two discharge ports, and the respective discharge ports are connected by oil passages 16a and 16b. The mechanical power from the input shaft 11 rotates the cylinder block of the variable displacement pump 3 to reciprocate the piston, and the reciprocating motion of the piston causes the pressure oil to be transmitted to the variable displacement motor 4 through one of the oil passages 16a and 16b. The return oil is supplied to the variable displacement pump 3 from the other side. Then, the piston is slid by the pressure oil sent to the variable displacement motor 4, and the cylinder block is rotated by this sliding, and the output shaft 12 is rotated to output.

An input rotation sensor 2 as an input rotation speed detecting means constituted by a potentiometer or the like is provided on the side of the input shaft 11, and the input rotation sensor 2 is connected to the rotation speed of the input shaft 11. Thereafter, the input rotation speed) is detected. Similarly, the rotation speed of the output shaft 12 (hereinafter, the output rotation speed) is detected by the output rotation sensor 5 as output rotation speed detecting means disposed on the side of the output shaft 12. The input rotation sensor 2 and the output rotation sensor 5 are connected to a control device 30. Therefore, the control device 30 calculates the input rotation speed and the output rotation speed per unit time by the input rotation sensor 2 and the output rotation sensor 5, so that the rotation speeds of the input shaft 11 and the output shaft 12 are obtained. (The output shaft 12 rotation speed / the input shaft 11 rotation speed) can be obtained.

The shift by the HST 10 is performed as shown in FIG. First, at low speed, the motor displacement Vm of the variable displacement motor 4 is set to the maximum motor displacement Vm_max. Then, the pump displacement Vp of the variable displacement pump 4 is changed to change the speed ratio R. Here, the motor displacement Vm is the amount of hydraulic oil discharged per one revolution of the output shaft 12 in the variable displacement motor 4, and similarly, the pump displacement Vp is the discharged amount of hydraulic oil per revolution of the input shaft 11 in the variable displacement pump 3. It is. Further, the pump displacement Vp and the motor displacement Vm change depending on the inclination angles of the swash plates 3a and 4a, respectively.
(In other words, the direction perpendicular to the axis of the output shaft is the lowest, and the direction parallel to the axis is the maximum). The speed ratio R can be expressed as R = Vp / Vm using the displacement Vm of the motor and the displacement Vp of the pump. In FIG. 2, the speed change operation in the HST 10
The manner in which the speed ratio R increases as going downward is shown. However, since the piston cannot reciprocate when the swash plates 3a and 4a are vertical, the hydraulic oil cannot flow and cannot be taken out as a rotational output. Therefore, when the rotational output is obtained, the hydraulic oil flows through the oil passages 16a and 16b. It shall be inclined to the extent.

At low speeds, the motor displacement V
m is a maximum and constant value, and Vm / Vm_max = 1. Here, in order to increase the pump displacement Vp, the swash plate 4a is inclined to increase the speed ratio R. The maximum value of the pump displacement Vp is the maximum pump displacement Vp_max. Where the speed ratio R
0 is R0 = Vp_max / Vm_max.

A state in which the speed ratio R is equal to or less than R0 is defined as a low-speed state, whereas a state in which the speed ratio R is larger than R0 is defined as a high-speed state. At high speed, the pump displacement Vp of the variable displacement pump 3 is kept at the maximum (Vm = Vm_max). Then, the motor displacement V of the variable displacement motor 4
The speed ratio R is changed by changing m. As described above, the displacement capacity Vm of the motor has the maximum value at this time, so that the displacement is gradually reduced. Therefore, the pump displacement Vp is a maximum and constant value, and Vp / Vp_max = 1. On the other hand, the motor displacement Vm draws a curve that is inversely proportional to the speed ratio R.

As shown in FIG. 3, in the HST 10,
By reducing the inclination angle of the swash plate 4a of the variable displacement motor 4, a speed ratio R larger than the speed ratio R0 can be obtained. On the other hand, in the case of the HST 21 having the constant displacement motor 23, the inclination of the swash plate of the constant displacement motor 13 cannot be changed, so that the speed ratio R can be changed only by the variable displacement pump 3. Will be Here, the pump displacement Vp of the constant displacement motor 13 is always Vm = Vm_max. HST
In the case of 21, it is not possible to obtain a speed ratio R larger than the speed ratio R0 that is Vp_max / Vm_max.
That is, the HST 10 including the variable displacement motor 4 can obtain a larger shift range on the high speed side than the HST 21 including the constant displacement motor 23.

Hydraulic continuously variable transmission 9 having HST 10
Are connected to the control device 30 as shown in FIGS. The control device 30 can perform any control of a plurality of control procedures described later,
The control switching device 28 can be arbitrarily selected and switched. The control device 30 is connected to the target output speed setting device 29, the input rotation sensor 2, the output rotation sensor 5, the pump actuator 6, and the motor actuator 7. Detection signals of the input rotation speed and the output rotation speed from the input rotation sensor 2 and the output rotation sensor 5 are transmitted to the control device 30, and the control device 30 performs processing related to control according to a control procedure described later. Based on the result, a signal for controlling the pump actuator 6 and the motor actuator 7 is transmitted from the control device 30 to the pump actuator 6 and the motor actuator 7. Then, as described above, the HST 10 including the variable displacement pump 3 and the variable displacement motor 4 performs the shift by driving the pump actuator 6 and the motor actuator 7.

Next, when the target output speed per unit time is set by the target output speed setting device 29, the output speed is detected and the hydraulic output of the second embodiment is controlled to approach the target output speed. The continuously variable transmission will be described. The control procedure in the second embodiment is shown in FIG. Control device 30
Is started (S1), and the target output speed (set speed) is set. The target value is input to the control device 30 (S2).
Detects the current output speed and outputs the signal to the control device 30.
(S3).

Next, it is determined whether or not the current value of the output rotation speed matches the target value (S4). If the current value is equal to the target value, the process returns to S2 and the control is repeated. If the current value is different from the target value, the displacement of the pump displacement Vp of the variable displacement pump 3 and the displacement Vm of the motor of the variable displacement motor 4 required for the present value to become the target value are calculated. Is performed (S5). Here, the required pump displacement Vp and motor displacement Vm are the capacities that give the speed ratio at which the HST 10 achieves the target output speed. This displacement calculation is based on the speed ratio R and the pump displacement V shown in FIG.
It is calculated based on the relationship with p · pump displacement Vp.

The control device 30 controls the variable displacement pump 3
The pump actuator 6 and the motor actuator 7 are driven so that the pump displacement Vp and the motor displacement Vm required by the variable displacement motor 4 are obtained (S6). When the current value of the output rotation speed matches the target value, the driving of the pump actuator 6 and the motor actuator 7 is stopped and the positions are maintained.

In the above control, the motor displacement Vm is reduced to the maximum motor displacement Vm_ at low speed (R0 or less).
max, and when shifting to high speed (R0 or higher)
The motor displacement Vm is the maximum motor displacement Vm
This is an operation for reducing the size from _max, and this operation is referred to as operation A. For such control, the upper limit of the motor displacement Vm at low speed is set to the maximum motor displacement V.
An operation of setting the value to less than m_max is also possible. If the operation in this case is operation B, the displacement V of the motor in operation B
The upper limit of m is a motor displacement upper limit capacity Vm_b which is reduced by a predetermined amount from the maximum motor displacement capacity Vm_max.

As shown in FIG. 6, in the case of operation B, the speed ratio R
Even at a speed ratio giving 0 (Vp_max / Vm_max), the pump displacement Vp does not become the maximum. Therefore, the speed ratio R can be increased to the speed ratio Rm by increasing the pump displacement Vp while keeping the motor displacement Vm fixed. Here, the speed ratio Rm is determined by the operation B
Is the speed ratio when the pump displacement Vp becomes the maximum pump displacement Vp_max. Operation A
In this case, the speed ratio Rm matches the speed ratio R0. In other words, by changing the capacity of the motor displacement upper limit capacity Vm_b for an arbitrary speed ratio R, it is possible to provide the motor displacement capacity Vm and the pump displacement capacity Vp at low speeds that realize this. That's it. Therefore, the variable displacement pump 3 and the variable displacement motor 4 for realizing a certain speed ratio R with respect to the control operation of the HST 10 as described later.
Is not limited to a single control operation, so that flexible control can be performed. That is, it is possible to lower the upper limit of the motor displacement Vm so that the variable displacement pump 3 can perform a shift on the speed increasing side (not synonymous with the high speed side) as in the case of the constant displacement motor. is there. Here, the range of the speed ratio change range T by the variable displacement motor 3 is theoretically infinitely larger than the speed ratio Rm.

Next, a description will be given of a third embodiment of the control in which, when the target output speed is set, the output speed is detected, and only the displacement of the motor is changed so as to approach the target output speed. In this case, the displacement of the motor is set lower than the maximum value, so that the displacement of the motor can be changed. As shown in FIG. 7, when control is started (S11) and a target value of the output rotation speed is input to the control device 30 (S12), the control device 30 outputs the output rotation speed detected by the output rotation sensor 5. Is input as a detection signal (S13).

Next, it is determined whether or not the current value of the output rotation speed matches the target value (S14). If the current value matches the target value, the process returns to S2 and the control is repeated. If the values are different, the displacement of the motor displacement Vm of the variable displacement motor 4 required to match the target value is calculated (S15). As shown in FIG. 6, when the displacement of the motor Vm is reduced while the displacement of the pump Vp is fixed, an operation for shifting from the operation A to the operation B is performed. For example, if the motor displacement is reduced from the maximum pump displacement Vp_max, the maximum motor displacement Vm_max, and the speed ratio R0 to the motor displacement upper limit Vm_b, the speed ratio shifts from R0 to Rm. Thus, the speed ratio R is changed by changing the displacement of the motor Vm.

The control device 30 controls the variable displacement pump 3
-The motor actuator 7 is driven so that the pump displacement Vp and the motor displacement Vm required by the variable displacement motor 4 are obtained (S16). When the current value of the output rotation speed matches the target value, the driving of the pump actuator 6 and the motor actuator 7 is stopped and the positions are maintained.

Next, a target output speed is set, the current values of the input speed and the output speed are detected, and even if the input speed fluctuates, the current value of the output speed matches the target output speed. A fourth embodiment of the control will be described. As shown in FIG. 8, when the control is started (S21) and the target output speed is indicated, the output speed (fixed value of the output speed) at that time is input to the control device 30 (S22). Then, the current value of the input rotation speed detected by the input rotation sensor 2 and the current value of the output rotation speed detected by the output rotation sensor 5 are input to the control device 30 (S23).

Next, it is determined whether or not the current value of the output rotation speed matches the fixed value (S24). If they match, the process returns to S22. if,
When the current value and the target value are different, the displacement of the pump displacement Vp of the variable displacement pump 3 and the displacement of the motor Vm of the variable displacement motor 4 required for the present value to match the target value are calculated. This is performed (S25). Here, the required pump displacement Vp and motor displacement Vm are the capacities at which the HST 10 provides a speed ratio for realizing the output rotation speed of the fixed value with respect to the current value.

The control device 30 controls the variable displacement pump 3
The pump actuator 6 and the motor actuator 7 are driven so that the pump displacement Vp and the motor displacement Vm required by the variable displacement motor 4 are obtained (S26). When the current value of the output rotation speed becomes equal to the fixed value, control is performed to stop the driving of the pump actuator 6 and the motor actuator 7.

Next, a description will be given of a fifth embodiment of the control for limiting the upper limit of the output rotation speed by changing the minimum value of the displacement of the motor. As shown in FIG. 9, when the control procedure is started (S31) and the target value of the output rotation speed and the upper limit rotation speed are input to the control device 30 (S32), the control device 30
Causes the current value of the output rotation speed detected by the output rotation sensor 5 to be transmitted as a detection signal to the control device 30 (S33).

Next, it is determined whether or not the current value of the output rotation speed matches the target value (S34), and if so, the process returns to S23. If the present value and the target value are different, the required displacement of the pump displacement Vp of the variable displacement pump 3 and the required displacement Vm of the motor 4 is calculated (S3).
5). This displacement calculation is performed based on the relationship between the speed ratio R, the pump displacement Vp, and the motor displacement Vm shown in FIG.

Subsequently, the control device 30 determines whether or not the motor displacement Vm calculated by the displacement calculation is equal to or greater than a minimum value corresponding to the upper limit rotation speed (S36). That is, it is compared with a value that is the lower limit of the change range of the motor displacement Vm and the minimum value Vm_min. HS
At T, as the inclination of the swash plate 3a of the input-side variable displacement pump 3 and the inclination of the swash plate 4a of the output-side variable displacement motor 4 decrease, the power loss increases and the power transmission efficiency decreases. Therefore, it is necessary to limit the speed changeover to the high-speed side to prevent inefficient running. Therefore, a lower limit is set for the change range of the motor displacement Vm, and an upper limit is given to a possible output rotation speed, so that unintended high-speed rotation can be prevented.

Motor displacement Vm is minimum value Vm_m
The speed ratio R when in becomes the value that becomes the speed ratio Rm_max. Therefore, the range of the speed ratio change range Tm by the variable displacement motor 3 is a range of the speed ratio Rm_max rather than the speed ratio Rm as shown in FIG.

If the motor displacement Vm calculated by the displacement calculation is equal to or greater than the minimum value Vm_min, the control device 30 determines the pump displacement Vp and the motor displacement required for the variable displacement pump 3 and the variable displacement motor 4. The drive of the pump actuator 6 and the motor actuator 7 is commanded so as to achieve the displacement Vm (S37). If the motor displacement Vm calculated by the displacement calculation is smaller than the minimum value Vm_min, an operation of substituting the minimum value Vm_min into the calculated value of the motor displacement Vm is performed (S38). Then, the control device 30 controls the variable displacement pump 3
The pump displacement Vp and the motor displacement Vm that require the variable displacement motor 4 are minimum values Vm_min.
Therefore, the pump actuator 6 and the motor actuator 7 are driven (S37). S36
In any case, if the operation of S38 is completed, the process of S32 is performed again.

Next, a description will be given of a hydraulic continuously variable transmission according to a sixth embodiment which comprises a plurality of variable displacement pumps and a plurality of variable displacement motors, wherein the variable displacement pump and the variable displacement motor are selectively operated in parallel. . In the hydraulic continuously variable transmission according to the present embodiment, an HST 42 in which three variable displacement pumps 3 and three variable displacement motors 4 are connected in parallel will be described. FIG.
As shown in the figure, the variable displacement pump 3 and the variable displacement motor 4
The two are connected by an oil passage. In the variable displacement pump 3, power is transmitted from the input shaft 11 to the input branch shaft 11a via a gear, a belt transmission, a chain transmission mechanism, or the like. The variable displacement motors 4 each protrude the output branch shaft 12.

The three variable displacement pumps 3, 3, 3 constitute a pump section, and the three variable displacement motors 4, 4, 4 constitute a motor section. Each of the discharge port and the input port of the variable displacement pump 3 and the variable displacement motor 4 has an oil passage 32.
33 is connected, and a switching valve 40 is connected to each port.
・ 40 ... are provided. The switching valve 40/4
.. Consist of electromagnetic valves, and as shown in FIG.
It is connected to a pump motor switching device 31. However, the switching valves 40 may be manually switched. According to the switching signal transmitted from the control device 30 to the pump motor switching device 31, the switching valve 40
.. Are switched to connect and disconnect the oil passage, and each variable displacement pump 3 and each variable displacement motor 4 are used independently or in an unused state.
A desired output can be obtained. Also,
The pump section and the motor section are connected by oil passages 36 and 37.

With the above arrangement, not only the inclination of the swash plates 3a, 4a of the variable displacement pump 3 and the variable displacement motor 4 but also the control operation of the switching valves 40, 40... Can be varied.

[0040]

According to a first aspect of the present invention, there is provided a transmission having a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the displacement of the variable displacement motor is maximized at a low speed. As the speed is changed by changing the displacement of the pump by the pump actuator of the variable displacement pump, and at high speed, the speed is changed by changing the displacement of the motor by the actuator for the motor by maximizing the displacement of the pump. I can do it. In addition, during shifting, one of the pumps and the motor can be used with the displacement being maximized, and the tendency of the efficiency to decrease when the displacement of the axial type pump / motor is small, that is, when the inclination angle of the swash plate is small, can be reduced.

According to a second aspect of the present invention, an input speed detecting means for detecting a speed of an input shaft of the variable displacement pump, an output speed detecting means for detecting a speed of an output shaft of the variable capacity motor, Output speed target value setting means, comprising the actuator, a control device for controlling them,
Since the motor actuator and the pump actuator are operated and controlled so that the output rotation speed approaches the target value, the reproducibility of the speed can be improved.

According to a third aspect of the present invention, there is provided a transmission having a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the input for detecting the rotation speed of the input shaft of the variable displacement pump is provided. Rotation speed detection means, output rotation speed detection means for detecting the rotation speed of the output shaft of the variable displacement motor,
Output speed target value setting means, a motor actuator and a pump actuator, and a control device for controlling the same are detected, the current value of the output speed is detected, and the motor actuator is operated to change the displacement of the motor. Since the control is performed to bring the current value closer to the target value within a certain range, the operator can control the target output rotational speed only by changing the displacement of the motor. This allows
Since the displacement of the pump can be handled independently as a manual operation and the displacement of the motor can be handled independently as speed control, it is possible to eliminate the sense of incongruity of the operator due to the difference when the displacement of the pump and the motor is changed.

According to a fourth aspect of the present invention, there is provided a transmission provided with a hydrostatic drive transmission comprising a pair of a variable displacement pump and a variable displacement motor, wherein the speed of the input shaft of the variable displacement pump is detected. Input rotation number detection means, output rotation number detection means for detecting the rotation number of the output shaft of the variable displacement motor, output rotation number target value setting means, motor actuator and pump actuator, and control for controlling these A control device that drives the motor actuator and the pump actuator to change the displacement of the motor and the displacement of the pump in response to the fluctuation of the input rotation speed, and to control the output rotation speed to coincide with the target output rotation speed. As a result, the state of the engine can be reflected in the shift control, and the reproducibility of the speed can be improved.

According to a fifth aspect of the present invention, the minimum value of the displacement of the motor can be set, and the displacement of the motor is controlled to be equal to or more than the minimum value and the output speed is limited to a certain upper limit or less. Speed can be regulated. Thus, the safety can be improved by regulating the speed, and it can be used as a mode switching between a work mode and a traveling mode.

According to a sixth aspect of the present invention, the output rotational speed is detected to change the displacement of the motor and the displacement of the pump to the target output rotational speed. Since two or more of the control for changing the displacement of the pump to the target output speed and the control for changing the minimum value of the displacement of the motor to the maximum output speed or less can be selected and switched, the driving mode is selected. Necessary control can be performed according to the above.
Thereby, it becomes easy to respond to various kinds of work used by the tractor or the like, and requests due to differences in workers.

According to a seventh aspect of the present invention, a plurality of the variable displacement pumps and the variable displacement motors are respectively arranged in parallel, and a switching device is provided at each of the input port and the output port of each of the variable displacement pumps and the variable displacement motor to be selectively used. Since the configuration is made possible, the change in the displacement of the entire displacement by the pump and the motor can be increased as compared with the case where the pair of pumps and the motor are provided. Therefore, a flexible shift is possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a variable displacement pump / variable displacement motor type HST.

FIG. 2 is a diagram showing a relationship between a shift and a motor displacement / pump displacement in a variable displacement pump / variable displacement motor type HST, and a magnitude of a swash plate inclination angle.

FIG. 3 is a diagram showing a relationship between a speed ratio and a motor displacement / pump displacement in a variable displacement pump / variable displacement motor type HST.

FIG. 4 is a control circuit diagram of the hydraulic continuously variable transmission.

FIG. 5 is a diagram showing a control procedure in the second embodiment.

FIG. 6 shows a variable displacement pump / variable displacement motor type HST in the case where the displacement of the motor is not maximized.
The figure which shows the relationship between a speed ratio, the displacement of a motor, and the displacement of a pump.

FIG. 7 is a diagram showing a control procedure in the third embodiment.

FIG. 8 is a diagram showing a control procedure in a fourth embodiment.

FIG. 9 is a diagram showing a control procedure in the fifth embodiment.

FIG. 10 is a diagram showing a relationship between a speed ratio and a motor displacement / pump displacement in a case where an upper limit and a lower limit are given to a motor displacement in a variable displacement pump / variable displacement motor type HST.

FIG. 11 is a circuit diagram showing an HST including a plurality of variable displacement pumps and a plurality of variable displacement motors.

FIG. 12 is a control circuit diagram of a switching valve according to a sixth embodiment.

FIG. 13 is a circuit diagram showing a variable displacement pump / constant displacement motor type HST.

[Explanation of symbols]

 Reference Signs List 2 input rotation sensor (input rotation number detecting means) 3 variable displacement pump 4 variable displacement motor 5 output rotation sensor (output rotation number detecting means) 6 pump actuator 7 motor actuator 9 hydraulic stepless transmission 10.42 HST ( (Hydrostatic transmission) 11 input shaft 12 output shaft 28 control switching device 30 control device 31 pump motor switching device 32, 33, 36, 37 oil passage 40 switching valve Vm pump displacement Vp motor displacement Vm_min minimum value

Claims (7)

[Claims] 1. A variable displacement pump comprising a hydrostatic transmission including a pair of variable displacement pumps and a variable displacement motor, wherein the displacement of the variable displacement motor is maximized at low speeds. Speed by changing the displacement of the pump by the actuator for
A speed change device wherein the displacement is changed by changing the displacement of the motor by a motor actuator by maximizing the displacement of the pump at a high speed. 2. An input rotation speed detection means for detecting a rotation speed of an input shaft of the variable displacement pump, an output rotation speed detection device for detecting a rotation speed of an output shaft of the variable displacement motor, and an output rotation speed target value. The apparatus according to claim 1, further comprising a setting unit, the actuator, and a control device for controlling the actuator, wherein the motor actuator and the pump actuator are operated and controlled so that the output rotation speed approaches a target value. Item 4. The transmission according to Item 1. 3. A transmission having a hydrostatic drive transmission comprising a pair of variable displacement pumps and a variable displacement motor, comprising: an input rotation speed detecting means for detecting a rotation speed of an input shaft of the variable displacement pump; Output rotation speed detection means for detecting the rotation speed of the output shaft of the variable displacement motor; output rotation speed target value setting means; a motor actuator and a pump actuator; and a control device for controlling these. A transmission apparatus comprising: detecting a current value of a number, operating a motor actuator to change a displacement of the motor, and performing control to bring the current value closer to the target value within a certain range. 4. A transmission device comprising a hydrostatic drive transmission comprising a pair of variable displacement pumps and a variable displacement motor, wherein an input rotation speed detecting means for detecting a rotation speed of an input shaft of the variable displacement pump. An output rotation speed detecting means for detecting the rotation speed of the output shaft of the variable displacement motor, an output rotation speed target value setting means, a motor actuator and a pump actuator, and a control device for controlling these. In response to a change in the input rotation speed, the motor actuator and the pump actuator are driven to change the displacement of the motor and the displacement of the pump, and control is performed so that the output rotation speed matches the target output rotation speed. Transmission. 5. The system according to claim 2, wherein a minimum value of the displacement of the motor is settable, and the displacement of the motor is controlled to be equal to or more than the minimum value to limit the output speed to a certain upper limit or less. The transmission according to any one of claims 3 and 4. 6. A control for detecting the output rotation speed and changing a displacement of the motor and a displacement of the pump to a target output rotation speed, and changing a displacement of the motor and a displacement of the pump in response to a change in the input rotation speed. 3. The method according to claim 2, wherein two or more of the control to set the target output rotation speed and the control to change the minimum value of the displacement of the motor to be equal to or less than the maximum output rotation speed are selected and switched. The transmission according to any one of claims 3, 4, and 5. 7. The variable displacement pump and the variable displacement motor are each arranged in a plurality in parallel, and a switching device is provided at each of the input port and the output port of each of the variable displacement pump and the variable displacement motor so as to be selectively usable. The transmission according to any one of claims 1 to 6, characterized in that: