JP4870476B2 - Hydraulic traveling device for work vehicle - Google Patents

Description

The present invention relates to a hydraulic travel drive device used for a work vehicle such as a rough terrain crane, a track travel crane, a wheel loader, and the like, and more particularly, a hydraulic travel drive device for a work vehicle using a variable displacement travel hydraulic motor. It is about.

As shown in FIG. 2, a hydraulic travel drive device for this type of work vehicle includes a hydraulic pump 3 driven by a prime mover 1 whose rotational speed is controlled by an accelerator pedal 1a, a forward / reverse switching valve 4, and a pair of main pipes. A variable displacement traveling hydraulic motor 7 connected by paths 5 and 6 and driven by hydraulic oil supplied from the hydraulic pump 3 through the forward / reverse switching valve 4 to rotate the wheels 2 of the work vehicle.
A capacity control means 8 for changing the capacity of the traveling hydraulic motor 7, a counter balance valve 9 interposed in the main pipelines 5 and 6, and a main circuit between the counter balance valve 9 and the traveling hydraulic motor 7. 5 and 6, and bypass valves 10 and 11 connected to the bypass pipes 10 and 11 and brake valves (relief valves) 12 and 13 interposed therebetween.

The capacity control means 8 is configured to increase or decrease the capacity of the traveling hydraulic motor 7 in accordance with the increase or decrease of the hydraulic pressure generated on the high pressure side of the main pipelines 5 and 6 downstream of the counter balance valve 9.

The hydraulic travel drive device for a work vehicle configured as described above controls the rotational speed of the prime mover 1 by depressing the accelerator pedal 1a after switching the forward / reverse switching valve 4 from the neutral position to the forward position or the reverse position. Thus, the amount of hydraulic oil supplied from the hydraulic pump 3 to the traveling hydraulic motor 7 is controlled, and the rotation of the traveling hydraulic motor 7, that is, the traveling speed of the work vehicle is controlled.

The counter balance valve 9 operates the amount of oil discharged from the main circuit 5 or 6 on the hydraulic oil discharge side (the side from which hydraulic oil is discharged from the traveling hydraulic motor 7) when the traveling hydraulic motor 7 rotates. When the pressure in the main pipeline 6 or 5 (pressure between the counter balance valve 9 and the forward / reverse switching valve 4) on the oil supply side (side supplying hydraulic oil to the traveling hydraulic motor 7) increases, it opens, and when it decreases, it narrows down. To function.

When driven by the pressure of the main pipeline 6 or 5 on the hydraulic oil supply side of the traveling hydraulic motor 7 (hereinafter simply referred to as “motor drive”), the flow of hydraulic oil in the main pipeline 5 or 6 on the hydraulic oil discharge side is counterbalanced. The back pressure of the traveling hydraulic motor 7 is low without being regulated by the valve 9. Therefore, the traveling hydraulic motor 7 is driven by the hydraulic pressure of the main pipeline 6 or 5 on the hydraulic oil supply side.

At the time of “motor drive”, the displacement control means 8 controls the displacement of the traveling hydraulic motor 7 according to the hydraulic pressure of the main pipeline 6 or 5 on the hydraulic oil supply side. When the driving resistance to be applied is large, low speed and high torque driving is performed, and when the driving resistance acting on the driving resistance is small, the traveling hydraulic motor 7 is driven to high speed and low torque.

When the accelerator pedal 1a is loosened while the work vehicle is traveling, or when the work vehicle is traveling downhill, the traveling hydraulic motor 7 is self-propelled and the main oil supply side main passage is provided. The pressure of 6 or 5 is lowered. In this case, the hydraulic oil discharge through the main oil line 5 or 6 on the hydraulic oil discharge side is throttled by the counter balance valve 9, and a back pressure is generated in the main pipe line 5 or 6 on the hydraulic oil discharge side. It acts as a brake (hereinafter referred to as “hydraulic brake”) against self-running of the vehicle (travel hydraulic motor 7).
In the “hydraulic brake”, the counter balance valve 9 is connected to the main oil line 5 on the hydraulic oil discharge side so that the amount of oil discharged from the traveling hydraulic motor 7 does not exceed the amount of oil supplied to the traveling hydraulic motor 7. Alternatively, the control is performed by controlling the amount of oil supplied to the motor, that is, by adjusting the amount of depression of the accelerator pedal 1a.

Note that the maximum braking force of the “hydraulic brake” is that the amount of oil discharged from the motor exceeds the flow rate through the counterbalance valve 9 and a part or all of the amount of oil discharged from the motor is installed in the bypass pipes 10 and 11. It is generated in a state where the fluid flows through the main oil passage 6 or 5 on the hydraulic oil supply side through 12 and 13. In this state, the back pressure of the traveling hydraulic motor 7 is the maximum pressure that is the set pressure (set relief pressure) of the brake valves 12 and 13, and the capacity of the traveling hydraulic motor 7 is maximized according to this pressure. ing.

That is, the “hydraulic brake” has a maximum capacity of the traveling hydraulic motor 7 and the pressure (back pressure) of the main pipeline 5 or 6 on the hydraulic oil discharge side from the traveling hydraulic motor 7 is the set pressure of the brake valves 12 and 13. The braking force at the time of being the maximum braking force is varied from zero to the maximum braking force (see, for example, the following patent document).
JP-A-63-266201

The hydraulic travel device for a work vehicle configured as described above drives the work vehicle (travel hydraulic motor 7) at a required direction and speed by switching the forward / reverse switching valve 4 and adjusting the amount of depression of the accelerator pedal 1a. Alternatively, the drive can be braked.

However, since the work vehicle (travel hydraulic motor 7) is braked only by the “hydraulic brake” controlled by adjusting the amount of depression of the accelerator pedal 1a, the work vehicle (travel hydraulic motor 7) is arbitrarily set. There is a problem that it is extremely difficult to brake at a deceleration of 2 mm.

  The hydraulic traveling device for a work vehicle according to the present invention is configured to apply a friction brake by the friction braking means 15 to the above-described conventional hydraulic traveling device so as to be superposed on the hydraulic brake by the traveling hydraulic motor 7 and the accelerator pedal 1a. An accelerator pedal non-depressing detection means 16 for detecting non-depression of the accelerator pedal is provided, and a detection signal of the accelerator pedal non-depressing detection means 16 is input to the capacity control means 8. When the detection signal is received from the vehicle, the capacity of the traveling hydraulic motor 7 is limited to a small capacity.

The hydraulic travel device for a work vehicle of the present invention configured as described above can apply an arbitrary braking force to the wheels 2 of the work vehicle by the friction braking means 15 by depressing the brake pedal.

Incidentally, in general, the brake pedal 14 and the accelerator pedal 1a are operated with the same foot.
Therefore, the depression operation of the brake pedal and the release of the depression of the accelerator pedal are simultaneously performed, and the braking of the wheel 2 by the friction braking means 15 and the braking of the traveling hydraulic motor 7 by the “hydraulic brake” are simultaneously performed. For this reason, when the friction braking means 15 is simply provided independently of the “hydraulic brake”, the maximum braking force of the “hydraulic brake” (maximum capacity of the traveling hydraulic motor 7 is determined from the traveling hydraulic motor 7. Pressure of main pipeline 5 or 6 on the hydraulic oil discharge side (back pressure)
Braking force when the brake valve 12 or 13 is at the set pressure) and the braking force by the friction braking means 15 are superimposed, and the wheel 2 of the work vehicle locks and the running speed of the work vehicle cannot be effectively braked. Things happen frequently.

  In order to solve such a problem, the hydraulic travel device for a work vehicle according to the present invention is provided with friction braking means 15 that operates in response to the operation of the brake pedal 14 and brakes the rotation of the wheel 2, so that the travel hydraulic pressure is increased. In addition to being configured to apply the friction brake by the friction braking means 15 to be superimposed on the hydraulic brake by the motor 7, the accelerator pedal non-depression detecting means 16 for detecting non-depression of the accelerator pedal 1a is provided, and this accelerator pedal non-depression detection means is provided. When the detection signal from the accelerator pedal non-depressing detection unit 16 is received, the displacement control unit 8 limits the displacement of the traveling hydraulic motor 7 to a small amount. I am doing so.

  In the hydraulic travel device for a work vehicle configured as described above, when the friction braking means 15 is operated, the accelerator pedal 1a is in a non-depressed state, so that the capacity control means 8 is restricted to a capacity of the travel hydraulic motor 7. As a result, the braking force by the “hydraulic brake” is limited to a small value. Therefore, the occurrence of a situation in which the wheel 2 is locked can be reduced, and braking can be performed at an arbitrary deceleration mainly depending on the operation of the friction braking means 15.

An embodiment of a hydraulic traveling device for a work vehicle according to the present invention will be described below with reference to FIG.

The hydraulic traveling device for a work vehicle according to the present invention is a conventional hydraulic traveling device shown in FIG.
Friction braking means 15 that operates in response to the operation of the brake pedal 14 and brakes the rotation of the wheel 2 is provided so that the friction brake by the friction braking means 15 acts on the hydraulic brake by the traveling hydraulic motor 7. In addition, the accelerator pedal non-depressing detection means 16 for detecting non-depression of the accelerator pedal 1a is provided, and the detection signal of the accelerator pedal non-depressing detection means 16 is input to the capacity control means 8, and the capacity control means 8 The configuration is characterized in that when the detection signal from the accelerator pedal non-depressing detection means 16 is received, the capacity of the traveling hydraulic motor 7 is limited to a small capacity.

Therefore, in the following explanation, we will focus on the explanation of this characteristic part,
For the description of the configuration and function of the conventional hydraulic traveling apparatus shown in FIG.
The following description will be incorporated as it is.

In FIG. 1, 15 is a friction braking means for braking the wheel 2 of the work vehicle in response to an operation (depression operation) of the brake pedal 14.

In this embodiment, the friction braking means 15 includes the brake drum 15a disposed on the wheel 2 and the brake shoe 1 pressed against the brake drum 15a by the output of the brake cylinder 15b.
5c. Brake operating pressure is supplied to the brake cylinder 15b from a master cylinder 14a connected to the brake pedal 14 via a conduit 14b.

  Reference numeral 16 denotes accelerator pedal non-depression detecting means 16 for detecting non-depression of the accelerator pedal 1a.

  In this embodiment, the accelerator pedal non-depressing detection means 16 is an example of a limit switch that detects the position of the accelerator pedal 1a that returns when the accelerator pedal 1a is not depressed.

  The detection signal of the accelerator pedal non-depressing detection means 16 (detection signal for detecting non-depression) is input to the capacity control means 8, and the capacity control means 8 receives the detection signal from the accelerator pedal non-depression detection means 16. In this case, the capacity of the traveling hydraulic motor 7 is limited to a predetermined small capacity.

In the state where no detection signal is input from the friction braking detection means 16, the capacity control means 8 travels according to the hydraulic pressure on the high pressure side of the pair of main pipelines 5, 6 after the counter balance valve 9 as described above. It functions to increase or decrease the capacity of the hydraulic motor 7 for use.

In the example of FIG. 1 (also in FIG. 2), the capacity control means 8 includes check valves 8a and 8b for taking out the high pressure side hydraulic pressure of the pair of main pipes of the traveling hydraulic motor 7, and the output thereof is the traveling hydraulic motor. 7
The capacity increasing cylinder 8c connected to the capacity converting mechanism of the traveling hydraulic motor 7 so as to increase the capacity of the traveling hydraulic motor 7, and the output thereof is connected to the capacity converting mechanism of the traveling hydraulic motor 7 so as to decrease the capacity of the traveling hydraulic motor 7. A capacity reduction cylinder 8d and a pilot control valve 8e for controlling the hydraulic pressure supplied to the capacity reduction cylinder are provided.

The capacity increasing cylinder 8c is connected to the subsequent stage of the check valves 8a and 8b through an oil passage 8f.
The pilot control valve 8e is interposed between an oil passage 8g connected to the capacity reduction cylinder 8d, an oil passage 8f connected to the subsequent stage of the check valves 8a and 8b, and a tank oil passage 8h.
The pilot control valve 8e is configured such that the oil pressure in the oil passage 8g increases as the oil pressure in the oil passage 8f increases.
The pilot pressure application portion 8i is connected to the oil passage 8f through the pilot oil passage 8j so that the internal pressure of the oil chamber of the capacity reduction cylinder is switched to decrease.

The effective pressure receiving area of the capacity decreasing hydraulic cylinder 8d is set larger than the effective pressure receiving area of the capacity increasing cylinder 8c.

  In the present invention, the capacity control means 8 is configured to limit the capacity of the traveling hydraulic motor 7 to a predetermined small capacity when receiving the detection signal (energization signal) of the accelerator pedal non-depressing detection means 16. In order to realize this, in the example of FIG. 1, the pilot oil passage 8j that connects the pilot pressure application portion 8i of the pilot control valve 8e and the oil passage 8f is connected to the pilot oil passage 8j at all times (when the solenoid is not energized). In communication, when energizing (when energizing the solenoid), a solenoid switching valve 8l that connects the pilot control valve 8e side (pilot pressure application unit 8i side) of the pilot oil passage 8j to the tank oil passage 8k is interposed, The solenoid switching valve 8l is controlled to be switched by a detection signal (energization signal) from the accelerator pedal non-depressing detection means 16.

    In the above embodiment, when the accelerator pedal 1a is depressed, the detection signal (energization signal) is not output from the accelerator pedal non-depressing detection means 16, and the hydraulic pressure of the oil passage 8f (the high-pressure side main pipeline 5) is output via the solenoid switching valve 8l. Or the hydraulic pressure of 6) acts on the pilot pressure application portion 8i of the pilot control valve 8e. For this reason, the capacity control means 8 increases or decreases the capacity of the traveling hydraulic motor 7 in accordance with the oil pressure on the high pressure side of the pair of main pipelines 5 and 6 at the rear stage of the counter balance valve 9.

  When the accelerator pedal 1a is not depressed, a detection signal (energization signal) is output from the accelerator pedal non-depressing detection means 16, and the solenoid switching valve 8l connects the pilot pressure application portion 8i of the pilot control valve 8e to the tank oil passage 8k. To do. For this reason, the capacity control means 8 limits the capacity of the traveling hydraulic motor 7 to a predetermined small capacity regardless of the hydraulic pressure fluctuation of the main pipelines 5 and 6.

  Accordingly, when the friction braking means 15 is activated by depressing the brake pedal 1a, the accelerator pedal is not depressed before that, so the braking force of the "hydraulic brake" by the traveling hydraulic motor 7 is restricted, and the wheel 2 is locked. You can reduce the occurrence of such a situation. Further, the traveling of the work vehicle can be braked at an arbitrary deceleration depending on the operation of the friction braking means 15 whose brake force can be easily adjusted.

The circuit diagram which shows the Example of the hydraulic traveling apparatus of the working vehicle which concerns on this invention. The circuit diagram of the hydraulic traveling apparatus of the conventional work vehicle.

Explanation of symbols

Prime mover; 1, accelerator pedal; 1a, wheel (work vehicle); 2, hydraulic pump; 3,
Forward / reverse switching valve; 4, a pair of main pipelines; 5, 6; (variable displacement type) traveling hydraulic motor; 7,
Capacity control means; 8, counter balance valve; 9, bypass line; 10, 11,
Brake valves; 12, 13, brake pedal 14, master cylinder 14a,
Friction braking means; 15, brake drum; 15a, brake cylinder; 15b,
Brake shoe; 15c, accelerator pedal non-depressing detection means; 16, check valve; 8a, 8b,
Capacity increasing cylinder 8c, capacity decreasing cylinder 8d, pilot control valve 8e,
Oil passage (after the check valves 8a, 8b); 8f,
Oil passage (connected to the capacity reduction cylinder 8d); 8g,
Tank oil passage; 8h, 8k, pilot pressure application section (of pilot control valve 8e); 8i,
Solenoid switching valve; 8 l
Pilot oil passage (connecting pilot pressure application section 8i and solenoid valve 8l); 8j,

Claims (1)

A hydraulic pump 3 driven by a prime mover 1 whose rotational speed is controlled by an accelerator pedal 1a, a forward / reverse switching valve 4 and a pair of main pipelines 5 and 6 are connected to the hydraulic pump 3 via the forward / reverse switching valve 4. A variable displacement traveling hydraulic motor 7 that is driven by the supplied hydraulic oil to rotationally drive the wheels 2 of the work vehicle, a capacity control means 8 that changes the capacity of the traveling hydraulic motor 7, and main pipes 5 and 6. The intervening counterbalance valve 9, the bypass lines 10 and 11 connecting the main circuits 5 and 6 between the counterbalance valve 9 and the traveling hydraulic motor 7, and the bypass line 1
And brake valves 12 and 13 interposed between 0 and 11,
The capacity control means 8 is configured to increase or decrease the capacity of the traveling hydraulic motor 7 in accordance with the hydraulic pressure on the high pressure side of the pair of main pipes 5 and 6 following the counter balance valve 9. In the device
Friction braking means 15 that operates in response to the operation of the brake pedal 14 and brakes the rotation of the wheel 2 is provided so that the friction brake by the friction braking means 15 acts on the hydraulic brake by the traveling hydraulic motor 7. In addition, the accelerator pedal non-depressing detection means 16 for detecting non-depression of the accelerator pedal 1a is provided, and the detection signal of the accelerator pedal non-depressing detection means 16 is input to the capacity control means 8, and the capacity control means 8 A hydraulic travel device for a work vehicle, characterized in that when the detection signal from the accelerator pedal non-depressing detection means 16 is received, the capacity of the travel hydraulic motor 7 is limited to a small capacity.

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