JPH10311400A - Hydraulic continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic continuously variable transmission of high transmitting efficiency. SOLUTION: An input shaft 3 of a radial piston pump 2 is connected to an engine 1, an output shaft 6 is connected to forward/reverse switching gear box 30. Pump action is performed such that by an input from the engine 1, in the radial piston pump 2, hydraulic fluid is sucked from a suction passage 9, to be delivered to a delivery path 10. During pumping action of the radial piston pump 2, by restricting a delivery side passage by a proportional control solenoid valve 14, flow resistance is given to delivery fluid, relating to the input shaft 3, the output shaft 6 is rotated by reduction ratio corresponding to a restriction, when the delivery side passage is fully closed, the input/output shafts 3, 6 are directly connected. Delivery oil of an accelerating variable pump 19 is supplied to the delivery system passage of the radial piston pump 2, it is operated as a motor, rotational speed of the output shaft 6 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a hydraulic continuously variable transmission used for, for example, a power transmission device of an automobile.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic type continuously variable transmission used in an automobile, all the power of an engine is converted into fluid energy by a hydraulic pump, and then returned to mechanical energy again by a hydraulic motor and transmitted to a load. 2. Description of the Related Art A hydrostatic continuously variable transmission of a type is known, and the continuously variable transmission changes the speed by changing the discharge amount of a hydraulic pump and the capacity of a hydraulic motor.

[0003]

The hydrostatic continuously variable transmission described above has the advantage that there is no shock at the time of gear shifting and that the riding comfort is good as compared with a gear type mechanical transmission. On the other hand, there is a disadvantage that the transmission efficiency peculiar to the hydraulic type is low. The transmission efficiency of a hydrostatic continuously variable transmission is mainly governed by the efficiency of a hydraulic pump, and the total efficiency of the hydraulic pump is generally expressed by: total efficiency = volume efficiency × mechanical efficiency. That is, in the case of a hydraulic pump, mechanical loss due to the loss due to leakage of hydraulic fluid and frictional resistance between sliding surfaces (for example, in the case of an axial piston pump of a swash plate type, mechanical resistance due to frictional resistance between a piston and a swash plate). Loss occurs, which results in low efficiency.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a hydraulic continuously variable transmission using a hydraulic pump as a power transmission means, which eliminates mechanical loss due to frictional resistance among losses occurring in the hydraulic pump. To increase the transmission efficiency.

[0005]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows. That is, the invention of claim 1 is a hydraulic type continuously variable transmission, which comprises an input shaft connected to a driving device and an output shaft connected to a driven device, and between the two shafts, the rotation of the input side. A rotary hydraulic pump in which a force in the circumferential direction acts on the output side, and an opening for continuously controlling the opening of the discharge system passage of the rotary hydraulic pump between a fully open position and a fully closed position. A control means is provided.

According to the first aspect of the present invention, when the input shaft of the rotary hydraulic pump is rotated by the power of the driving device, the opening degree of the discharge system passage is reduced and the flow of the working fluid is reduced. , A circumferential force is applied from the input shaft side to the output shaft side, and the output shaft is rotated at a reduced speed with respect to the input shaft. The speed reduction ratio (speed ratio) at that time corresponds to the throttle amount of the discharge system passage. When the discharge passage is fully closed, the flow of the working fluid is locked, and the input shaft and the output shaft rotate integrally and are directly connected. As described above, according to the first aspect of the present invention, by continuously controlling the throttle of the discharge system passage, it is possible to continuously change the speed at the input / output shaft, and to smoothly transmit the power without a shift shock. it can. The hydraulic continuously variable transmission according to the present invention employs a system in which mechanical energy is converted into hydraulic energy by a rotary hydraulic pump, and then the hydraulic energy is taken out again as mechanical energy. The conventional hydrostatic stepless transmission employs a frictional force, which causes a mechanical loss, as a force for assisting the torque transmission in the power transmission between the motor and the output shaft, which only involves a loss related to hydraulic pressure. Transmission efficiency can be increased as compared with the device.

According to a second aspect of the present invention, in the hydraulic stepless transmission according to the first aspect, a speed increasing pump driven by the driving device and a hydraulic fluid discharged from the speed increasing pump. And a speed-increasing switching means for introducing the hydraulic pump into the discharge system passage of the rotary hydraulic pump and operating the hydraulic pump as a motor.

Therefore, according to the second aspect of the present invention, when the input shaft and the output shaft of the rotary hydraulic pump are directly connected to each other, the hydraulic fluid discharged from the speed increasing pump is rotated by the rotary hydraulic pump. By feeding the pump into the discharge passage of the pump, the rotary hydraulic pump acts as a motor. for that reason,
The rotation speed of the output shaft can be increased to the rotation speed of the input shaft plus the rotation speed of the motor.

According to a third aspect of the present invention, in the hydraulic stepless transmission according to the second aspect, the speed increasing pump is constituted by a variable displacement pump, and the pump capacity of the speed increasing pump is changed. And a speed increasing ratio control means capable of continuously controlling the operating pressure of the hydraulic displacement changing means. According to such a configuration, the speed increase ratio between the input and output shafts can be changed by changing the capacity of the speed increasing pump to increase or decrease the discharge flow rate.

[0010] The invention of claim 4 is the invention of claim 2 or 3.
In the hydraulic continuously variable transmission according to the above, when the discharge system passage of the rotary hydraulic pump is in an open state, the discharge pump from the speed increasing pump is sent to a suction system passage of the rotary hydraulic pump as a charge pump. It is characterized in that it is used. With such a configuration, it is possible to prevent the occurrence of cavitation due to an increase in suction negative pressure into the suction passage of the rotary hydraulic pump during deceleration operation.

According to a fifth aspect of the present invention, in the hydraulic continuously variable transmission according to the third aspect, the opening degree control means and the speed increasing switching means are constituted by a proportional control solenoid valve.
The speed increase ratio control means is constituted by a proportional control electromagnetic valve for speed increase control. When such a configuration is adopted, for example, when a hydraulic type continuously variable transmission is applied to an automobile, a throttle of a discharge system passage of a rotary hydraulic pump or a discharge system of a rotary hydraulic pump is increased from a speed increasing pump. The amount of hydraulic fluid sent to the passage can be controlled in accordance with a gear ratio set based on the engine speed, vehicle speed, accelerator pedal depression amount, and the like.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. The hydraulic continuously variable transmission according to the present embodiment uses a radial piston pump as a power transmission means, and will be described as applied to a transmission in an industrial vehicle traveling drive device such as a forklift. . FIG. 1 is a circuit diagram illustrating a hydraulic type continuously variable transmission, and FIG. 2 is a schematic cross-sectional view of a radial piston pump.

As shown in the figure, an input shaft 3 of a radial piston pump 2 of a constant displacement type used for transmitting the power of an engine 1 as a driving device to a driven device is provided with a large number of pistons 4 in a radial manner. The cylinder block 5 is fixed. On the other hand, the output shaft 6 of the radial piston pump 2
The cylinder block 5 has a case 7 fixed therein and a thrust ring 8 housed and fixed in the case 7.
Are eccentrically arranged. The output-side end of the output shaft 6 is provided with a forward / reverse switching gearbox 30 as a driven device side.
Gear shaft.

In the output shaft 6, two passages, a suction passage 9 and a discharge passage 10, are provided along the axial direction.
And one end of the discharge path 10 is provided on the outer peripheral surface of the shaft.
And an opening as the discharge port 10a. On the other hand, the cylinder block 5 is rotatably fitted to a portion of the output shaft 6 where the suction port 9a and the discharge port 10a are set,
A cylinder chamber 5a is opened on the inner peripheral surface of the fitting portion.
Therefore, when the cylinder block 5 rotates eccentrically in the thrust ring 8 together with the input shaft 3 by the power from the engine 1,
The hydraulic fluid is sucked and discharged by the piston 4 reciprocating in the cylinder chamber 5a.

The output shaft 6 has a swivel joint 11
The other end of the suction path 9 and the other end of the discharge path 10 are always communicated with the off-axis suction pipe 12 and the discharge pipe 13 by the swivel joint 11, respectively.
The suction passage 9 and the suction pipe 12 constitute a suction passage, and the discharge passage 10 and the discharge passage 13 constitute a discharge passage.

The suction line 12 and the discharge line 13 are connected to a proportional control solenoid valve 14 provided as opening control means for controlling the opening (throttle amount) of the discharge system passage. The proportional control solenoid valve 14 has a fully-open position (a) and a fully-closed position (b) of the discharge system passage, as well as a speed-up position (c), and a fully-open position (c) by a control signal from a controller (not shown). It is continuously displaced between a) and the fully closed position (b), and controls the throttle amount of the discharge path in accordance with the reduction ratio (speed ratio). Further, the proportional control solenoid valve 14 is designed to be switched to the speed increasing position (c) at the time of speed increasing. Therefore, the speed increasing position (c) of the proportional control solenoid valve 14 constitutes the speed increasing switching means. The suction side and the discharge side are communicated with each other between the fully open position (a) and the fully closed position (b). A check valve 17 and a relief valve 18 are provided in a pipe 16 connecting the proportional control electromagnetic valve 14 and the oil tank 15.

As a speed increasing pump for increasing the rotation speed of the output shaft 6 of the radial piston pump 2, for example, a variable displacement type swash plate type axial piston pump 19 (hereinafter, referred to as a variable pump) is provided. The variable pump 19 is driven from the input shaft 3 of the radial piston pump 2 via a gear train 20 (may be configured to be driven by another route from the engine 1), and the hydraulic fluid discharged from the variable pump 19 is It is sent to the proportional control solenoid valve 14 via a pipe 22 having a check valve 21.

The liquid discharged from the variable pump 19 is sent to the proportional control solenoid valve 14 and further from the upstream side of the check valve 21 to the control cylinder 24 for changing the pump capacity via the pipe 23. ing. The capacity of the variable pump 19 is adjusted by the balance between the pushing force of the control cylinder 24 acting in the capacity increasing direction and the spring 25 acting in the opposite direction. That is, the control cylinder 24 and the spring 25
This constitutes a hydraulic displacement changing means that varies the displacement by changing the inclination angle of the swash plate in the variable pump 19.

The line 23 is provided with a relief valve 26 for maintaining the charge pressure.
Is the pilot pressure and spring 27 that are guided from the upstream side.
Variable pressure pump 1 by keeping the pressure in the control cylinder 24 always at the set pressure by the balance with
9 is maintained in a small capacity state to prevent power loss.

The pipe 23 is provided with a pilot line 28 for applying a pilot pressure to the relief valve 26 on the side of increasing the set pressure.
The pilot line 28 is provided with a proportional control solenoid valve 29 as a speed increasing ratio control means for controlling the operating pressure of the control cylinder 24.
Numeral 9 is proportionally controlled by a control signal at the time of speed increase from the controller. The control signals output from the controller to the proportional control solenoid valves 14 and 29 are the reduction ratio and the speed increase that are set based on the engine speed, the vehicle speed, or the amount of depression of the accelerator pedal, as in the case of a normal automobile. It is configured to output according to the ratio.

Next, the operation of the present embodiment configured as described above will be described.

When the input shaft 3 of the radial piston pump 2 is rotated by the "stop" engine 1, the cylinder block 5 rotates eccentrically in the thrust ring 8 together with the input shaft 3, and the piston 4 reciprocates accordingly. The liquid is sucked from the suction port 9a and discharged to the discharge port 10a. That is,
The radial piston pump 2 performs a normal pumping operation. At this time, if the proportional control solenoid valve 14 is held at the fully open position (a), the flow path resistance of the discharge system is small, and the working fluid only circulates. Is not transmitted to the output shaft 6, and the drive wheels of the vehicle are not driven. At this time, the speed increase control solenoid valve 2
9 is held at the illustrated drain position. Therefore, the variable pump 19 acts as a charge pump, and keeps the pressure in the circuit of the suction system of the radial piston pump 2 constant.

During the operation of the "deceleration" radial piston pump 2, the proportional control solenoid valve 14 is continuously switched between the fully open position (a) and the fully closed position (b) based on a control signal output from the controller. And the discharge system passage is narrowed according to the reduction ratio. This throttle action adds resistance to the flow of hydraulic fluid in the discharge system of the radial piston pump 2, so that when the piston 4 rotates eccentrically in the thrust ring 8 together with the cylinder block 5, the tip of the piston 4 and the thrust ring during the discharge stroke 8 (the pressing force of the piston 4) with respect to the inner peripheral surface increases. That is, in the discharge stroke, the piston 4 discharges the hydraulic fluid while exerting a force such that its tip bites into the inner peripheral surface of the thrust ring 8, so that the thrust ring 8 has a circumferential force (rotational force). It acts, but its force corresponds to the amount of restriction of the discharge system passage. Therefore, the thrust ring 8 is rotated at a speed corresponding to the throttle amount, and the rotation is output to the case 7 and the output shaft 6 and then from the gear in the forward / reverse switching gear box 30 through a differential device (not shown) to drive the wheel. Is transmitted to

Thus, the power of the engine 1 is shifted by the radial piston pump 2 at a reduction ratio corresponding to the throttle amount of the discharge passage and transmitted to the driving wheels. At this time, the variable pump 19 acts as a charge pump in the same manner as when stopped, but the proportional control solenoid valve 29 for speed-up control is used.
Is held at the drain position, so that the pressure of the control cylinder 24 is kept constant by the relief valve 26 even when the rotation speed of the engine 1 increases.

The proportional control solenoid valve 14 is held at the fully closed position (b) based on the control signal output from the "direct connection" controller. As a result, the discharge system passage of the radial piston pump 2 is closed, so that the reciprocating motion of the piston 4 with respect to the cylinder block 5 is locked. That is, the pumping action of the radial piston pump 2 is locked, and the cylinder block 5 and the thrust ring 8 rotate integrally. Therefore, the rotation of the input shaft 3 is transmitted to the output shaft 6 without being decelerated. Note that, also at this time, since the proportional control electromagnetic valve 29 for speed increase control is held at the drain position, the variable pump 19 acts as a charge pump. Also, at the time of "deceleration" and "direct connection", the discharge liquid from the variable pump 19 is sent to the suction side of the radial piston pump 2, so that the suction load of the radial piston pump 2 when the engine 1 is rotated at high speed. Cavitation due to an increase in pressure can be prevented.

The proportional control solenoid valve 14 is switched to the speed increasing position (c) by a control signal output from the "speed increasing" controller. For this reason, the hydraulic fluid discharged from the variable pump 19 is sent to the discharge system passage of the radial piston pump 2, and the piston 4 is pressed against the inner peripheral surface of the thrust ring 8 by this hydraulic fluid, so that the thrust ring 8 is displaced. It rotates under the circumferential component force. That is, the radial piston pump 2 is acted as a motor by the variable pump 19, and the output shaft 6 is rotated at an increased rotational speed at the rotational speed of the input shaft 3 plus the motor rotational speed.

At the same time, the proportional control solenoid valve 29 for speed-up control is continuously displaced to the pilot pressure introduction side by the control signal output from the controller, and the pump port communicates with the valve port. Pressure acts. For this reason, the relief valve 26 uses the difference between the pilot pressure of the pilot line 28 and the resultant force of the spring 25 and the pilot pressure acting on the opposite side to cause the discharge of the variable pump 19
4 and the set pressure is adjusted. In this case, the proportional control solenoid valve 29 is continuously displaced in such a manner that the opening of the pump port to the tank port is reduced as the opening of the pump port to the valve port is increased. As the displacement increases, the pilot pressure acting on the relief valve 26 increases, and the set pressure of the relief valve 26 increases.

Thus, when the pump port communicates with the cylinder port due to the displacement of the relief valve 26, the liquid discharged from the variable pump 19 is sent to the control cylinder 24, and the control cylinder 24 changes the inclination angle of the swash plate to change the angle. The capacity of the pump 19 is changed. in this case,
The displacement amount of the relief valve 26 corresponds to the pilot pressure controlled by the proportional control solenoid valve 29, and the communication port opening degree of the pump port to the tank port is reduced as the communication port opening degree to the cylinder port is increased. , So that the control cylinder 24
Is increased or decreased in accordance with the displacement amount of the relief valve 26. That is, the capacity of the variable pump 19 is changed by the proportional control of the proportional control solenoid valve 29, and the rotation speed of the motor of the radial piston pump 2 is changed by changing the discharge amount of the working fluid supplied to the radial piston pump 2. be able to.

As described above, according to the fluid type continuously variable transmission according to the present embodiment, since the power transmission means for transmitting the power of the engine 1 to the load side by the radial piston pump 2 is constituted, the fluid unique to the pump is provided. Pressure loss (leakage)
And no mechanical loss (sliding resistance generated on the rotating sliding surface) occurs. This is because at the time of deceleration, the frictional resistance generated between the tip of the piston 4 and the inner peripheral surface of the thrust ring 8 acts in a direction that assists the transmission of the rotational force. Therefore, the transmission efficiency of the radial piston pump 2 becomes substantially equal to the volumetric efficiency, and can be improved as compared with the conventional hydrostatic continuously variable transmission. In particular, at the time of direct connection, the flow of the hydraulic fluid in the radial piston pump 2 is locked, and the input shaft 3 and the output shaft 6 rotate mechanically integrally. In this case, there is almost no loss in hydraulic pressure. , Higher transmission efficiency can be obtained.

According to the present embodiment, the speed is increased by adding the motor speed of the radial piston pump 2 to the speed of the input shaft 3, so that a high speed increase ratio can be obtained.
In addition, high-speed input rotation becomes possible. Furthermore, since the transmission according to the present embodiment is of the hydraulic transmission type, it can be smaller and transmit higher torque than a belt-driven continuously variable transmission.

It should be noted that the present invention is not limited to the above-described embodiment, and the configurations relating to the speed increasing system and the speed increasing ratio control system may be omitted, respectively, or may be applied to other than the vehicle. The hydraulic pump used as a power transmission means
Not only the radial piston pump 2 but also a type in which a mechanical force acting to rotate the hydraulic fluid on the output side by the rotation of the input side acts on the output side in the discharge stroke of the hydraulic fluid, for example, an axial piston pump can be applied. . Also,
A variable displacement pump may be used as the radial piston pump 2, or the speed increasing variable pump 19 may be changed to a fixed displacement pump. In the present embodiment, the radial piston pump 2 has been described in the case where the cylinder block 5 is provided on the input shaft 3 side and the thrust ring 8 is provided on the output shaft 6 side. Is also good. Furthermore,
The speed control means is not limited to the proportional control electromagnetic valve 14, but may be a manual (or foot force) operated type, for example.
In the present embodiment, the variable pump 19 is driven by a mechanical power transmission means such as the input shaft 3, but may be driven by an electric power transmission means via a generator / motor. Good.

[0032]

As described in detail above, according to the present invention,
In the hydraulic type continuously variable transmission, the transmission efficiency of power transmitted from the input side to the output side can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a hydraulic continuously variable transmission.

FIG. 2 is a schematic cross-sectional view of a radial piston pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Radial piston pump 3 ... Input shaft 4 ... Piston 5 ... Cylinder block 6 ... Output shaft 7 ... Case 8 ... Thrust ring 9 ... Suction path 10 ... Discharge path 11 ... Swivel joint 14 ... Proportional control solenoid valve 19 ... Variable pump for speed increase 29… Proportional control solenoid valve

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hideaki Igarashi 2-1, Toyota-cho, Kariya-shi, Aichi Prefecture Inside Toyota Industries Corporation

Claims (5)

[Claims] An input shaft connected to a driving device and an output shaft connected to a driven device, and between the two shafts, a circumferential force acts on an output side by rotation of the input side. A hydraulic continuously variable transmission, comprising: a hydraulic pump; and an opening control means for continuously controlling an opening of a discharge system passage of the rotary hydraulic pump between a fully open position and a fully closed position. 2. A speed increasing pump driven by the driving device, and hydraulic fluid discharged from the speed increasing pump is introduced into a discharge system passage of a rotary hydraulic pump to use the hydraulic pump as a motor. 2. The hydraulic type continuously variable transmission according to claim 1, further comprising: a speed-increasing switching unit that operates. 3. The speed increasing ratio control means, wherein the speed increasing pump is constituted by a variable displacement pump, and further capable of continuously controlling the operating pressure of a hydraulic displacement changing means for changing the pump capacity of the speed increasing pump. The hydraulic continuously variable transmission according to claim 2, further comprising: 4. When the discharge passage of the rotary hydraulic pump is in an open state, the discharge pump is used as a charge pump for feeding the discharge liquid from the speed increasing pump into a suction passage of the rotary hydraulic pump. The hydraulic stepless transmission according to 2 or 3. 5. The apparatus according to claim 3, wherein said opening control means and said speed-up switching means are constituted by a proportional control solenoid valve, and said speed-up ratio control means is constituted by a proportional control solenoid valve for speed-up control. The hydraulic stepless transmission according to any one of the preceding claims.