JPH01176852A - Vehicle incorporating continuously variable transmission - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vehicle equipped with a continuously variable transmission device that can be used in various fields such as agricultural vehicles and passenger cars.

[Prior Art] In this type of vehicle, one fluid pump/motor is operated by the power of a prime mover, and the working fluid discharged from this fluid pump/motor is sent to the other fluid pump/motor via a fluid pressure circuit. It is equipped with a continuously variable transmission that can drive the wheels with the power output from the other fluid pump/motor, and the output rotation speed/input rotation is controlled by controlling the displacement of the fluid pump/motor. There are some devices that can start shifting from a state where the speed ratio expressed by speed is zero or close to zero.

In such a device, a relief valve is provided in the fluid pressure circuit to define an upper limit of the fluid pressure.

[Problems to be Solved by the Invention] By the way, the relief setting pressure of a conventional relief valve is generally set to a value as high as possible within a range that can ensure circuit safety, etc. , cannot be changed while the vehicle is in operation. Therefore, in a vehicle equipped with a continuously variable transmission that can shift gears from a speed ratio of zero or close to zero, when the accelerator is strongly operated at the time of starting, the pressure in the fluid pressure circuit changes to the relief setting. The pressure will rise to a high level, and the wheels will be driven with high torque.

However, if high torque is applied to the wheels in places where the coefficient of friction between the road surface and the wheels is low, such as on snowy roads or muddy roads, the wheels will slip and the vehicle will not be able to start properly. There is.

The present invention aims to solve these problems.

[Means for solving the problems] In order to achieve the above objects, the present invention employs the following configuration.

That is, the vehicle according to the present invention operates one fluid pump/motor using the power of the prime mover, and supplies the working fluid discharged from the fluid pump/motor to the other fluid pump/motor via the fluid pressure circuit. , this other fluid pump/
It is equipped with a continuously variable transmission device that can drive the wheels with the power output from the motor, and by controlling the displacement volume of the fluid pump/motor, the speed ratio expressed by the output rotation speed/input rotation speed is zero. Alternatively, in a device that can start shifting from a state close to zero, a relief mechanism capable of changing the relief setting pressure is connected to the fluid pressure circuit, and the relief setting pressure of this relief mechanism is set by the driver. It is characterized in that it is constructed so that it can be adjusted by an operating means disposed at an operable position.

[Operations] With this kind of configuration, on normal roads where wheel grip can be ensured, by setting the relief setting pressure to a high value, the wheels can be rotated with high torque as before. The vehicle can then be started.

On the other hand, when starting on a snowy road or muddy road, the relief setting pressure is adjusted to a low value by operating the operating means. Then, regardless of how the accelerator is operated, the pressure in the fluid pressure circuit cannot rise above the lowered relief set pressure. As a result, the wheels are driven with lower torque and are less likely to slip and lose grip.

Therefore, it becomes possible to start the vehicle smoothly.

[Example 1] An example of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 schematically shows a vehicle. In the figure, 1 is an engine as a prime mover, 2 is a continuously variable transmission, and 3 is a wheel.

The continuously variable transmission 2 includes a pair of a variable displacement first fluid pump/motor 4 driven by the engine 1 and a variable displacement second fluid pump/motor 5 connected to the wheels 3. The fluid pressure circuits 6 and 7 are connected in a closed loop. A high voltage terminal 11 is connected to the fluid pressure circuit 6.7 via a pair of check valves 8, and a high pressure terminal 11 is connected to both hydraulic pressure circuits 6.7 via a pair of check valves 9. A relief mechanism 13 is interposed between these terminals 11 and 12, and a boost pump 14 is connected to the low voltage terminal 12. As shown in FIG. 2, the relief mechanism 13 includes a pilot pressure-controlled relief valve 1.
5 and the pilot pressure introduction port 1 of this relief valve 15
5a, and a pilot pressure control circuit 16 connected to the pilot pressure control circuit 5a. The pilot pressure control circuit 16 is connected to the relief valve 1.
5 pilot pressure introduction port 15a and the low voltage terminal 12
A throttle 18 and an electromagnetic on-off valve 19 are interposed in the middle of a conduit 17 that communicates with the two, and the electromagnetic on-off valve 19 can be opened and closed by a changeover switch 21 serving as an operating means. The changeover switch 21 is placed near the driver's seat 22, which can be operated by the driver, and the changeover signal generated by operating the changeover switch 21 is amplified by the amplifier 23 and then transferred to the electromagnetic on-off valve 19. By transmitting the signal to the solenoid 19a, the electromagnetic on-off valve 19 can be opened and closed.

With such a configuration, the displacement volume of the first fluid pump/motor 4 and the displacement volume of the second fluid pump/motor 5 can be controlled in the manner shown in FIG. 3, for example. Accordingly, it is possible to continuously change the speed ratio (output rotational speed/input rotational speed) of the continuously variable transmission 2 from a zero state. Then, when the changeover switch 21 is operated, the electromagnetic on-off valve 1 of the pilot pressure control circuit 16
9 opens and closes, and the pilot pressure introduced into the pilot pressure introduction port 15a of the relief valve 15 changes in two stages. As a result, the relief setting pressure of this relief valve 15 is set to a value for high torque or a value for low torque. When the relief setting pressure is set to a value for high torque, as shown by the solid line A in Fig. 4, in the region where the speed ratio is small, the wheel 3 However, when set to a low torque value, as shown by imaginary line B in Figure 4,
Even in the starting region where the speed ratio is small, the wheel drive torque is kept at a relatively low value.

However, on normal roads where the grip of the wheels 3 can be ensured, by setting the relief setting pressure to a value for high torque, the wheels 3 can be rotated with high torque as before and the vehicle can be driven. It can be launched.

On the other hand, when starting on a snowy road or muddy road, the changeover switch 21 is operated to adjust the relief setting pressure to a value for low torque. Then, regardless of how the accelerator is operated, the pressure in the fluid pressure circuit 6.7 cannot rise above the lowered relief set pressure. Therefore, the wheels 3 are driven with low torque, reducing the possibility of slipping and losing grip. Therefore, it becomes possible to start the vehicle smoothly.

Note that the configuration of the relief mechanism is of course not limited to that of the embodiment described above, and may be, for example, as shown in FIGS. 5 to 7.

That is, the relief mechanism 113 shown in FIG. A stepping motor-driven valve (which can be adjusted) is interposed, and a signal from a dial 121, which is an operating means disposed near the driver's seat, is transmitted to this electromagnetic proportional control valve 115 via an amplifier 123. This is what I did. Thus, by operating the dial 121, the relief set pressure of the electromagnetic proportional control valve 115 can be adjusted steplessly.

Furthermore, the relief mechanism 213 in FIG. 6 has a safety relief valve 201 interposed between the high voltage terminal 11 and the low voltage terminal 12 in the first embodiment, and
A control relief valve 215 is provided between the tank 202 and the tank 202 . The control relief valve 21.5 is of a pilot pressure control type similar to that shown in FIGS. 1 to 4.
Pilot pressure introduction port 215 of this relief valve 215
A pilot pressure control circuit 216 is connected to a.

The pilot pressure control circuit 216 is connected to the relief valve 215.
pilot pressure introduction port) 215a and the low voltage terminal 12
An electromagnetic on-off valve 219 is interposed in the middle of a conduit 217 communicating with the electromagnetic on-off valve 219, and the electromagnetic on-off valve 219 can be opened and closed by a changeover switch 221 serving as an operating means. The changeover switch 221 is placed in a driver's seat or the like that can be operated by the driver, and the changeover signal generated by operating the changeover switch 221 is amplified by an amplifier 223 and sent to the solenoid 219 of the electromagnetic on-off valve 219.
By transmitting the signal to a, the electromagnetic on-off valve 219 can be opened and closed. However, this relief valve 21
5, by operating the changeover switch 221, the relief setting pressure changes into two levels, a value for high torque and a value for low torque, and the value for bulk torque is as follows. It is set at a value slightly lower than the relief setting pressure of the safety relief valve 201. In this embodiment, the control relief valve 215 and the tank 20
A relief valve 203 for pilot pressure adjustment is interposed between the relief valve 203 and the pilot pressure adjusted by the relief valve 203. 2) is supplied via a conduit 204. That is, this accelerator modulator includes a differential mechanism having first, second, and third input/output terminals, and a fluid pressure actuator connected to the third input/output terminal of the differential mechanism. The actuator is operated by pilot pressure supplied from the pipe line 204. Then, the accelerator wire that transmits the mechanical operation amount of the accelerator operated by the driver to the fuel operating end of the engine is separated into a front part and a rear part, and the end of the front part of the accelerator wire is connected to the differential mechanism. The starting end of the latter part is connected to the second input/output end. However, when the control relief valve 215 is closed, the actuator is stopped at the reference position,
The amount of accelerator operation is directly transmitted to the fuel operation end of the engine via the front stage of the accelerator wire, the differential mechanism, and the rear stage of the accelerator wire, but when the relief valve opens, pilot pressure is supplied to the actuator. The actuator operates and changes the position of the third input/output terminal of the differential mechanism, so the amount of operation of the accelerator is subtracted by the amount of operation of the actuator in the differential mechanism and transmitted to the fuel operation end of the engine. will be done. Therefore,
Unnecessary revving of the engine is prevented.

In the embodiment shown in FIG. 6, the accelerator modulator is used to correct excessive operation of the accelerator, so that control is performed with the characteristics shown in FIG. 7.

That is, when the relief setting pressure is set to a value for high torque, the wheels can be driven with relatively high torque in the region where the speed ratio is small, as shown by the solid line a in FIG. However, if it is set to a value for low torque, the wheel drive torque will be suppressed to a relatively low value even in the starting region where the speed ratio is small, as shown by the imaginary line in Figure 7. .

Furthermore, the relief mechanism 313 shown in FIG. 8 replaces the pilot pressure control type relief valve 215 shown in FIG.
This uses an electromagnetic proportional control valve 315 (a stepping motor driven valve may also be used). In this system, a signal from a dial 321, which is an operating means disposed near the driver's seat, is transmitted to the electromagnetic proportional control valve 315 via an amplifier 323. , the relief set pressure of the electromagnetic proportional control valve 315 can be adjusted steplessly. Here, 301 is a safety relief valve.

In the above explanation, the present invention was applied to a continuously variable transmission of a so-called H8T (hydrostatic transmission) type, but the present invention is applied to a C1 so-called HMT (hydromechanic transmission) type. The present invention can be similarly applied to a vehicle equipped with a continuously variable transmission.

[Effects of the Invention] Since the present invention has the above-described configuration, it is possible to suppress slips and perform a smooth start even on snowy roads or muddy roads. Accordingly, it is possible to provide a vehicle equipped with a continuously variable transmission device capable of energy-saving operation.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic overall explanatory diagram, FIG. 2 is a circuit diagram showing main parts, FIG. 3 is a diagram showing a control mode, and FIG. FIG. 4 is a characteristic diagram. Fifth
The figure is a circuit diagram corresponding to FIG. 2 showing a second embodiment of the present invention,
FIG. 6 is a circuit diagram corresponding to FIG. 2 showing a third embodiment of the present invention, and FIG. 7 is a characteristic diagram of the same embodiment. FIG. 8 is a circuit diagram corresponding to FIG. 2 showing a fourth embodiment of the present invention. 1... Prime mover (engine) 2... Continuously variable speed, device 3... Wheels 4.5... Fluid pump/motor 6.7... Fluid pressure circuit 13... Relief mechanism 21... - Operating means (selector switch) 113... Relief mechanism 121... Operating means (dial) 213... Relief mechanism 221... Operating means (selector switch) 313... Relief mechanism 321... Operating means (Dial)

Claims (1)

[Claims] One fluid pump/motor is operated by the power of the prime mover,
The working fluid discharged from this fluid pump/motor is supplied to the other fluid pump/motor via a fluid pressure circuit, and the wheels can be driven by the power output from the other fluid pump/motor. A speed change device is provided, and by controlling the displacement volume of the fluid pump/motor, the speed change can be started from a state where the speed ratio expressed by the output rotation speed/input rotation speed is zero or close to zero. In the vehicle, a relief mechanism capable of changing the relief setting pressure is connected to the fluid pressure circuit, and the relief setting pressure of the relief mechanism can be adjusted by an operating means disposed at a position operable by the driver. A vehicle equipped with a continuously variable transmission characterized by comprising: