JPH0313408Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control device for a negative brake provided in a drive section of a hydraulically driven vehicle.

Applicable to hydraulically driven vehicles with a hydraulically driven transmission in which a hydraulic motor is driven by pressure oil discharged from a variable hydraulic pump driven by an engine, and its output shaft drives a driven part via a reduction gear. In this case, a negative brake is installed between the output shaft of the hydraulic motor and the reducer.

This negative brake is operated by the biasing force of a spring, and is released by supplying pressure oil into a hydraulic cylinder to deflect the spring. The brake cylinder of the brake is connected to a pressure source via a brake operating valve.

The brake operating valve is switched in conjunction with two operating mechanisms, one controlled by a hydraulically driven transmission and the other manually operated.

When the brake operating valve performs switching control in conjunction with the control of the hydraulically driven transmission, when the gear shift lever is switched to the neutral position, it is also switched to the brake position (drain position), which causes the hydraulic cylinder to switch to the brake position (drain position). The pressure oil inside is drained and the brake is activated by the spring force, resulting in a parking brake or stop brake state.

When the brake operating valve is manually switched and controlled, it is for stop braking while the vehicle is running, and after the brake pedal is depressed and pressure oil is restricted from the hydraulic source to perform hydrobraking, the brake operating valve is switched off. It is switched to the brake position and the brake is activated.

In a conventional negative brake control device of this type, means for interlocking switching between the control unit of a hydraulically driven transmission and a brake operating valve, and interlocking switching between a brake pedal and a hydraulic pump discharge flow rate restriction. In this system, a hydraulic pilot operated type brake operating valve is interposed in the circuit connecting the brake cylinder and the hydraulic power source, and the brake operating valve is connected to the control unit of the hydraulically driven transmission through a link within the hydraulic pilot circuit of the brake operating valve. It is equipped with a switching valve that is turned on and off by pilot pressure, and a pilot pressure pent valve that is connected to the hydraulic pilot pressure circuit by a mechanical link with a discharge flow rate control link of the hydraulic pump and is operated by a pedal. It controls switching of the hydraulic pilot operated type brake operating valve mentioned above.

Needless to say, such a conventional configuration is complicated. Since the brake operating valve is controlled by switching on, off and discharging the hydraulic pilot pressure, the brake operating valve is controlled by the flow resistance of the pilot pressure fluid in the pilot circuit, the discharge speed, time, etc. The switching operation varied and was unstable.

Furthermore, there was a problem in that the brake operation valve was not forced to be switched by artificial means, and emergency brake operation could not be obtained.

The present invention has been developed in consideration of the above-mentioned problems, and has a simpler configuration than conventional control devices, and also allows for reliable and smooth braking action, and also prevents emergency braking from being performed manually. It is an object of the present invention to provide a negative brake control device for a hydraulically driven vehicle that can perform the following steps.

In order to achieve the above object, the negative brake control device for a hydraulically driven vehicle according to the present invention connects a hydraulic motor 3 and a variable hydraulic pump 2 controlled by an electric/hydraulic servo valve 11 in a closed circuit 4, 5. A brake type brake 7 is provided on the output shaft 6 side of the hydraulic motor 3, which is actuated by spring force and released by hydraulic pressure. Also, between the closed circuits 4 and 5, it is shut off by pilot pressure. In a hydraulically driven vehicle equipped with a pilot bypass valve 10, the hydraulic pressure acting part of the brake 7 and the pilot bypass valve 10
A hydraulic pressure source 17 is connected to the pilot pressure acting section through a brake operating valve 16 which has a drain position 16a and a communication position 16b and is switched and operated by electromagnetic force.
, and a potentiometer 15a is connected to each operating fulcrum of the gear shift lever 13 and brake pedal 14.
15b, each potentiometer 15a,
15b is connected to each electromagnetic actuating portion of the brake operating valve 16 and the electric/hydraulic servo valve 11 via the control device 12, and the control device 12 controls the amount of operation of the shift lever 13 by forward/backward operation of the shift lever 13. A control signal corresponding to this is output to the electromagnetic actuating part of the electric/hydraulic servo valve 11, and when the gear shift lever 13 is operated for forward or backward movement, this becomes the communication position 16b to the electromagnetic actuating part of the brake operating valve 16, and the sonic lever When the brake pedal 14 is in the neutral position and the vehicle speed is close to zero, it outputs various signals to set the drain position 16a, and when the brake pedal 14 is depressed, the electric/hydraulic servo is activated depending on the amount of operation of the brake pedal 14. valve 1
This outputs a signal to the electromagnetic actuator 1 to control the state from the running state to the neutral state, and also outputs a signal to set the brake operating valve 16 to the drain position 16 when the vehicle speed reaches zero by depressing it more than a predetermined level. Further, the spool of the brake operating valve 16 and the brake pedal 14 are connected so that when the brake pedal 14 is tilted by a predetermined depression angle or more, the two are connected to switch the brake operating valve 16 in the drain direction. They are connected via a mechanical linkage.

In the above configuration, by operating the operating lever in the forward or reverse direction, a signal corresponding to the operating amount of the operating lever is output to the electromagnetic actuating portion of each of the electric/hydraulic servo valve and the brake operating valve. Vehicle speed is controlled according to the amount of operation. During this period, the brake operating valve is in the communicating position and the brake is released. When the gear shift lever is returned to the neutral position, the vehicle speed stops, but at this time, when the vehicle speed approaches zero, the brake operating valve is set to the drain position and the brake is operated. On the other hand, when the brake pedal is depressed, a signal corresponding to the amount of depression is output to the electrohydraulic servo valve and the electromagnetic actuator of the brake operating valve, and the vehicle speed is controlled according to the amount of depression of the brake pedal. When the temperature is close to zero, the brake operating valve is set to the drain position and the brake is operated. Also, at this time, the pilot bypass valve is in the bypass position, and the vehicle is stopped with the brakes applied.

Embodiments of the present invention will be described below based on the drawings.

In the figure, 1 is a hydraulically driven transmission configured with a closed-loop type hydraulic drive circuit, and 2 is shown with details omitted.
3 is a variable hydraulic pump driven by an engine (not shown), and 3 is a variable hydraulic motor, which are connected by closed circuits 4 and 5. A negative brake 7 is provided on the output shaft 6 of the hydraulic motor 3. The brake 7 is actuated by the biasing force of a spring 8 and released by pressure oil supplied into a brake cylinder 9. Ten
1 is a pilot bypass valve interposed between the closed circuits 4 and 5, and 11 is an electric/hydraulic servo valve for controlling the variable hydraulic pump 2.

The pilot bypass valve 10 has a bypass position 10a and a shutoff position 10b, and is switched to the bypass position 10a by a spring and to the shutoff position 10b by pilot pressure acting on a pilot pressure acting section.

12 indicates a control device, and this control device 12 includes:
a potentiometer 15a provided at each operating fulcrum of the gear shift lever 13 and the brake pedal 14;
15b, and based on this signal, a control signal is sent to the electric/hydraulic servo valve 11 and the brake operating valve 16 to control them.

The brake operating valve 16 is located at a drain position 16a that drains the brake cylinder 9 of the brake 7 and the pilot pressure acting part of the pilot bypass 10.
and a communication position 16b for supplying pressure oil from the hydraulic power source 17 to both of the operating parts. The brake operating valve 16 is switched to the drain position 16a by energizing the electromagnetic operating section 18. Further, a stem member 20 having a long hole 19 elongated in the switching operation direction is provided on the brake operation side of the brake operation valve 16.
An auxiliary lever 21 mechanically interlocked with the brake pedal 13 is engaged at 9, and the auxiliary lever 21
By rotating the lever over a certain rotation range, the auxiliary lever 21 engages and operates the stem member 20, and the brake operating valve 16 is placed in the drain position 16a. In addition, brake operating valve 1
6 is urged toward the drain position 16a by a spring 22.

FIG. 2 shows a specific example of a partial structure of the brake operating valve 16, in which a spring 22 is interposed between the spool valve 23 and the stem member 20. A spool valve 23 is operated by the stem member 20.

In the above configuration, when the gear shift lever 13 is operated to the forward (or reverse) side, the operation signal is transmitted to the control device 12, and from this control device 12 each electromagnetic actuation of the electric/hydraulic servo valve 11 and the brake operating valve 16 is performed. A switching signal is output to the section.

As a result, the electromagnetic actuator 18 of the brake operating valve 16
This resists the spring 22 and moves to the communication position 1.
6b, brake cylinder 9 of brake 7
Pressure oil acts on the pilot pressure acting portion of the pilot bypass valve 10, and the brake 7 is released, and the pilot bypass valve 10 is switched to the shutoff position 10b, allowing the vehicle to travel.

In this state, by changing the inclination angle of the speed change lever 13, the electric/hydraulic servo valve 1 of the hydraulic pump 2 is
1 is controlled, the discharge amount of the hydraulic pump 2 is changed, and the speed is changed.

Note that when the gear shift lever 13 is returned to the neutral position in order to stop the vehicle during the above-mentioned traveling, the energization to the electromagnetic actuating portion 18 of the brake operating valve 16 is not immediately cut off even when the gear shift lever 13 becomes neutral. , the control device 12 prioritizes the electric/hydraulic servo valve 11 of the hydraulic pump 2 to cause the vehicle speed to bottom out due to the hydrobraking action by decelerating the hydraulic pump 2;
When the vehicle speed approaches zero, the brake operating valve 1
The power supply to the electromagnetic actuating part 18 of 6 is cut off, the brake operating valve 16 becomes the drain position 16a, and at the same time the brake 7 is actuated, the pilot bypass valve 1
0 is the bypass position 10a, and the vehicle is stopped with the brakes applied.

Next, the braking action of the vehicle by the brake pedal 14 will be explained.

When the brake pedal 14 is depressed and tilted, a control signal is output to the electric/hydraulic servo valve 11 of the hydraulic pump 2 by the potentiometer 15b provided at the operating fulcrum of the brake pedal 14 and the control device 12, thereby controlling the hydraulic pump 2. A part, for example, a swash plate, is moved to a neutral position to limit its discharge amount, thereby applying a hydrobrake and applying primary braking to the vehicle speed.

When the vehicle speed becomes zero due to the primary braking by the hydrobrake, this is detected and a switching signal for the brake operating valve 16 is output from the control device 12, and the brake operating valve 16 is moved to the drain position 16a.
, and secondary braking is applied to the vehicle speed.

During the above-mentioned primary and secondary braking, the brake pedal 14
The linkage that mechanically connects the brake valve 16 and the brake operating valve 16 is freely movable through the elongated hole 19 of the stem member 20 and is not affected by the brake pedal 14.
A vehicle is braked using a hydrobrake and an electric signal.

On the other hand, when the brake pedal 14 is depressed while driving, the stem member 20 of the brake operating valve 16 is directly actuated via the linkage to the drain position 16.
a, the brakes are applied to the vehicle. This braking action is used as an emergency braking action. It is also used as a mechanical brake in the event of a runaway due to a failure of the electrical control mechanism.

Since the present invention is as described above, the brake 7 and the pilot bypass valve 10 are operated by one brake operating valve 16, so that the hydraulic circuit configuration can be simplified compared to the conventional one.
In addition, the brake operating valve 16 is connected to a potentiometer 15.
By being electrically operated via a, 15b and the control device 12, the switching operation can be performed stably without variation and can be performed smoothly. Furthermore, the brake operating valve 16 can be forcibly switched by manual means, thereby ensuring safety in an emergency.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram, and FIG. 2 is a partially cutaway explanatory view of a brake operating valve. 2 is a hydraulic pump, 3 is a hydraulic motor, 4 and 5 are closed circuits, 6 is an output shaft, 7 is a brake, 10 is a pilot bypass valve, 11 is an electric/hydraulic servo valve, 1
2 is a control device, 13 is a gear shift lever, 14 is a brake pedal, 15a, 15b are potentiometers,
16 is a brake operating valve, 16a is a drain position, 1
6b is a communication position, and 17 is a hydraulic power source.

Claims (1)

[Scope of utility model registration request] A closed circuit 4 connects a hydraulic motor 3 and a variable hydraulic pump 2 controlled by an electric/hydraulic servo valve 11.
A negative type brake 7 is provided on the output shaft 6 side of the hydraulic motor 3, which is operated by spring force and released by hydraulic pressure. In a hydraulically driven vehicle equipped with a pilot bypass valve 10 that is in a cutoff position,
The hydraulic pressure acting portion of the brake 7 and the pilot pressure acting portion of the pilot bypass valve 10 are connected to each other via a brake operating valve 16 which has a drain position 16a and a communication position 16b and is switched and operated by electromagnetic force. Potentiometers 15a and 15b are connected to the power source 17 and are connected to the brake operating valve 16 and the electric power source 17 through the control device 12. - Connected to each electromagnetic actuation part of the hydraulic servo valve 11, and the control device 12,
By operating the shift lever 13 in forward or backward motion, a control signal corresponding to the amount of operation of the shift lever 13 is outputted to the electromagnetic actuating section of the electric/hydraulic servo valve 11.
During the forward/backward operation of step 3, this becomes the communicating position 16b to the electromagnetic actuating part of the brake operating valve 16, and when the gear shift lever 13 is in the neutral position and the continuous speed is near zero, it becomes the drain position 16a. In addition, when the brake pedal 14 is depressed, a signal is outputted to the electromagnetic actuating section of the electric/hydraulic servo valve 11 to control it from the running state to the neutral state, depending on the amount of operation of the brake pedal 14. With,
It is configured to output a signal to set the brake operating valve 16 to the drain position 16 when the vehicle speed reaches zero by depressing it more than a predetermined value, and furthermore, the spool of the brake operating valve 16 and the brake pedal 1 are
4, when the brake pedal 14 is tilted beyond a predetermined depression angle, both are connected and the brake operating valve 1 is activated.
6. A control device for a negative brake of a hydraulically driven vehicle, characterized in that the negative brake of a hydraulically driven vehicle is connected via a mechanical linkage configured to switch operation in the drain direction.