JPH064973B2 - Running hydraulic pressure control device for hydraulically driven vehicle - Google Patents

Description

Detailed Description of the Invention A. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling hydraulic control device for a hydraulically driven vehicle such as a wheel hydraulic excavator.

B. 2. Description of the Related Art FIG. 3 shows an example of a traveling hydraulic circuit of a conventional hydraulically driven vehicle.

The pressure oil discharged from the hydraulic pump 1 is controlled in its direction and flow rate by the hydraulic pilot control valve 2, and is supplied to the hydraulic motor 4 via the counter balance valve 3. A traveling drive shaft (not shown) is connected to the output shaft of the hydraulic motor 4, and the vehicle is driven by the rotation of the hydraulic motor 4.

The stroke amount of the pilot control valve 2 is controlled by the pilot pressure from the pilot hydraulic circuit. The pilot hydraulic circuit includes a pilot hydraulic pump 5 and a pilot valve 6 that controls the traveling speed of the vehicle by controlling the stroke amount of the control valve 2 following the hydraulic pump 5.
And a slow return valve 7 that follows the pilot valve 6 and delays return oil to the pilot valve 6, and a forward / reverse switching valve 8 that follows the slow return valve 7 and selects forward, reverse, or neutral of the vehicle. Have.

FIG. 3 shows a state in which the forward / reverse switching valve 8 is in the neutral position (N position) and the pilot valve 6 is not operated. Therefore, the pilot control valve 2 is in the neutral position, and The pressure oil returns to the tank 9 and the vehicle is stopped. When the forward / reverse switching valve 8 is switched to the forward (F position) or the reverse (R position) and the pedal 6a of the pilot valve 6 is operated, the oil discharged from the hydraulic pump 5 is discharged from the pilot control valve 2
When reaching the pilot port 2a or 2b, the control valve 2 is switched by a stroke amount according to the pilot hydraulic pressure, and the hydraulic motor 4 is driven by the oil discharged from the hydraulic pump 1 to drive the vehicle. Vehicle speed is pilot valve 6
Depends on the amount of depression.

When the pedal 6a is released during traveling, the pilot valve 6 shuts off the pressure oil, and its outlet port communicates with the tank 10. As a result, the pressure oil acting on the pilot port 2a or 2b returns to the tank 10 via the forward / reverse switching valve 8, the slow return valve 7, and the pilot valve 6. At this time, since the return oil is throttled by the throttle 7a of the slow return valve 7, the pilot control valve 2 is gradually switched to the neutral position. When the pilot type control valve 2 returns to the neutral position, the discharge oil of the hydraulic pump 1 returns to the tank 9, the counter balance valve 3 switches to the illustrated neutral position, and the hydraulic brake is applied to the hydraulic motor 4 by the throttle effect.

Although not shown, this type of hydraulically driven traveling device is provided with a brake device that brakes the traveling wheels rotated by the traveling drive shaft by stepping on the foot brake pedal.

C. Problems to be Solved by the Invention In this conventional circuit, the pedal 6 of the pilot valve 6 is in motion during traveling.
The pilot type control valve 2 is configured so as not to immediately return to the neutral position due to the action of the throttle 7a even when a is suddenly released, thereby preventing cavitation and sudden action of the hydraulic brake.

Therefore, during the predetermined time from the release of the pedal 6a until the pilot type control valve 2 returns to the neutral position, the pedal 6a
Despite the release, the oil supply to the hydraulic motor 4 is continued and the traveling drive shaft is driven. Therefore, when the driver feels dangerous while traveling and releases the pedal 6a and depresses the brake pedal, the braking force by the operation of the foot brake pedal and the traveling driving force by the hydraulic motor 4 are within the delay time described above. Together, the desired braking force is not obtained and the travel distance until stopping is increased, and abnormal heat generation and early abnormal wear of the brake device become noticeable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling hydraulic pressure control device for a hydraulically driven vehicle that solves the above-mentioned problems by immediately returning the traveling pilot type control valve to the neutral position when the brake pedal is depressed.

D. Means for Solving the Problems A hydraulically driven vehicle to which the present invention is applied will be described with reference to FIG. 1 showing a first embodiment.
Is operated to control the stroke amount of the pilot-type control valve 2, thereby controlling the direction and flow rate of the oil discharged from the hydraulic pump 1 to drive the hydraulic motor 4. When the operation of the pilot valve 6 is neutral, the return oil from the pilot port of the pilot control valve 2 is throttled by the throttle means 100. Further, the brake is activated by the operation of the brake device 30.
Therefore, in the present invention, the return passage cross-sectional area of the throttle means 100 can be selectively set to either large or small, and the braking device 30
The detecting means 51 for detecting the operation of the above and the selecting means 21 for setting the passage sectional area of the throttle means 100 to be large when the operation of the brake device 30 is detected by the detecting means 51 are provided.

E. When the action detecting means 51 detects the operation of the brake device 30, the selecting means 21 selects the throttle means 100 so that the return oil passage sectional area becomes large. Therefore, when the pilot valve 6 is released and the brake device 30 is operated during traveling,
The pilot control valve 2 immediately returns to the neutral position.

F. First Embodiment First Embodiment A first embodiment of the present invention will be described with reference to FIG.
Note that, in FIG. 1, the forward / reverse switching valve 8, the hydraulic pump 1, the pilot control valve 2, the counter balance valve, and the hydraulic motor 4 shown in FIG. 3 are shown in a simplified manner, and the same as in FIG. The same reference numerals are given to the parts and the description thereof will be omitted.

The outlet port of the pilot valve 6 is connected to the inlet port of the electromagnetic switching valve 21, and one of the outlet ports of the switching valve 21 is connected to the forward / reverse switching valve 8 via the slow return valve 7 shown in FIG. Of the slow return valve, which is connected to the inlet port of the
Connected to 22 entrance ports. This slow return valve 22
The outlet port of is joined with the outlet side of the slow return valve 7. Here, the throttle 22a in the slow return valve 22
Is larger than the cross-sectional area of the throttle 7a in the slow return valve 7. Both throttles may have the same cross-sectional area, or the slow return valve 22 may be omitted to provide a simple passage.

FIG. 1 also shows a brake device 30 for braking the running wheels and a pneumatic circuit 40 for controlling the operation thereof.

The brake device 30 includes a brake assembly 31 installed on each traveling wheel, and a pneumatic-hydraulic booster 32 that controls the brake assembly 31, a pressure source 41 and a foot-operated brake valve 42 for traveling. The brake is adapted to be actuated by the compressed air supplied from the pneumatic circuit 40 consisting of.

A pressure switch 51 that opens and closes according to the pressure of the conduit 43 communicating with the pneumatic-hydraulic power booster 32 is installed, and the battery 52 is connected to the solenoid section of the electromagnetic switching valve 21 via the pressure switch 51.

In the above configuration, the slow return valves 7 and 22 are the throttle means 100, the pressure switch 51 is the detection means, and the electromagnetic switching valve 2
1 constitutes the selection means.

Next, the operation of this embodiment will be described.

FIG. 1 shows a state where neither the pilot valve 6 nor the traveling brake valve 42 is operated. Therefore,
The hydraulic motor 4 is stopped and the vehicle is also stopped. When the pedal 6a of the pilot valve 6 is depressed, similarly to the above, the pilot type control valve 2 is switched according to the switching position of the forward / reverse switching valve 8 and the hydraulic motor 4 is rotated to drive the vehicle.

When the pedal 6a is released during traveling, the outlet port of the pilot valve 6 communicates with the tank 10, and the pressure oil acting on the pilot port of the pilot type control valve 2 is transferred to the forward / reverse switching valve 8, the slow return valve 7, the electromagnetic valve. Return to the tank 10 via the switching valve 21. Up to this point, the process is exactly the same as the conventional one.

When the pedal 42a of the traveling brake valve 42 is depressed at the same time when the pedal 6a is released, pressure is applied to the pipe line 43 to activate the brake device 30. At this time, the pressure switch 51 is closed, the solenoid 52 of the electromagnetic switching valve 21 is supplied with power from the battery 52, and the electromagnetic switching valve 21 is switched to "B". As a result, the slow return valve 7 is disconnected from the tank 10 and the slow return valve 22
Is connected to the tank 10, the return oil from the pilot port of the pilot type control valve 2 has a large cross-sectional area.
Return to the tank via. As a result, the pilot control valve 2 is immediately switched to the neutral position, the hydraulic brake is applied to the hydraulic motor 4, and the vehicle is immediately stopped together with the mechanical braking on the traveling wheels.

-Second Embodiment- A second embodiment of the present invention will be described with reference to FIG.
The same parts as those in FIG. 1 are designated by the same reference numerals, and the hydraulic pump 1, the pilot control valve 2, the counter balance valve 3, and the hydraulic motor 4 are not shown.

In this embodiment, the passage that bypasses the slow return valve 7 is used.
61 is provided, and the slow return valve 22 and the electromagnetic switching valve 62 are provided there.
Are connected in series, and the electromagnetic switching valve 62 is switched by opening / closing the pressure switch 51.

In this embodiment, since the electromagnetic switching valve 62 is switched to "B" during brake operation, the return oil from the pilot port of the pilot control valve 2 returns to the tank 10 from both the slow return valves 7 and 22, and The pilot control valve 2 returns to the neutral position more quickly than in the above embodiment. In this embodiment, two slow return valves having throttles of the same cross section may be installed in parallel.

The present invention is also applied to a hydraulic traveling vehicle in which the forward / reverse switching valve 8 is omitted and a pair of forward and backward pilot valves 6 are provided to move forward when one lever is tilted forward and to move backward when tilted backward. Applicable.

G. EFFECTS OF THE INVENTION According to the present invention, when the brake device for braking the traveling wheels is operated by operating the operation member such as the brake pedal,
Since the pilot type control valve that controls the direction and flow rate of pressure oil to the traveling hydraulic motor quickly returns to the neutral position, the braking force and traveling hydraulic driving force do not act at the same time as in the past, and the braking force is effective. There is provided a device that can be used and that prevents abnormal heat generation and early abnormal wear of the brake device, prolongs the life of the brake device and improves safety.
When the brake is activated, the hydraulic brake also works to improve the brake feeling.

[Brief description of drawings]

1 and 2 are block diagrams showing the first and second embodiments of the present invention, and FIG. 3 is a block diagram showing a conventional example. 1: Hydraulic pump, 2: Pilot type control valve 3: Counter balance valve 4: Hydraulic motor, 5: Hydraulic pump 6: Pilot valve 7,22: Slow return valve 8: Forward / reverse switching valve, 21, 62: Electromagnetic switching valve 30: Brake device, 41: Pressure source 42: Travel brake valve, 51: Pressure switch 61: Bypass passage

Claims (1)

[Claims] 1. A hydraulic pump driven by a prime mover, a hydraulic motor driven by pressure oil discharged from the hydraulic pump to drive a traveling drive shaft, and pressure oil from the hydraulic pump flowing into the hydraulic motor. A hydraulic pilot control valve for controlling the flow rate and direction, a pilot valve for controlling the stroke amount of the hydraulic pilot control valve according to the operation amount, and the hydraulic pilot control when the operation amount of the pilot valve is reduced. A throttle means for throttling the return oil from the pilot port of the valve to delay the return of the control valve to the neutral position, and a brake device for decelerating and stopping the vehicle by braking the member on the output side of the hydraulic motor. In the traveling hydraulic control device for a hydraulically driven vehicle, the return passage cross-sectional area of the throttle means can be selectively set to either large or small. And a selecting means for detecting that the braking device is in a braking state, and a selecting means for setting a large passage cross-sectional area of the throttle means when the braking state of the braking device is detected by the detecting means. A traveling hydraulic control device for a hydraulically driven vehicle characterized by: