JP2808356B2 - Crawler vehicle brake operation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of operating a brake on a traveling device of a crawler vehicle.

[Conventional technology]

Conventionally, a device related to this type of brake actuation method is described in
FIG. 1A (JP-A-51-37380).

This brake device is provided between a counter balance valve 70 connected to the hydraulic motor 3 and supply / discharge circuits 3a and 3b of the hydraulic motor 3, and has brake valves 71 and 72 having characteristics shown in FIG. When the counter balance valve 70 is at the switching position 70b or 70c, the supply / discharge circuits 5a, 5
b, which is connected to the high pressure side to release the braking force to the hydraulic motor 3 and the directional control valve 73 becomes the neutral position, and the supply / discharge circuit 5a,
When both 5b are connected to tank 7, the counter balance valve
70 returns to the neutral position 70a, and after a predetermined time, the hydraulic motor 3
And a mechanical brake device 4 for applying a braking force to the motor.

According to this brake device, the braking force applied to the hydraulic motor 3 is applied to the hydraulic motor 3 as a dynamic braking force (dynamic braking force).
Then, after the hydraulic motor 3 is stopped, a braking force by the mechanical brake device 4 is applied as a parking brake. Therefore, it has a complicated structure that requires two types of fluid brake device and mechanical brake device. Therefore, there is a brake device disclosed in FIG. 6 (Japanese Utility Model Laid-Open No. 57-122801) which was developed with a view to simplifying the structure. This brake device intends to use the mechanical brake device 4 as a dynamic braking force. The configuration is such that a high-pressure selection valve 81 is provided between supply / discharge circuits 3a and 3b connecting between the direction switching valve 80 and the hydraulic motor 3,
The operation of the mechanical brake device 4 is controlled by the high-pressure selection valve 81.

When the hydraulic motor 3 is driven by switching the direction switching valve 80 from the neutral position 80a, the high pressure selection valve 81 connects the high pressure side of the supply / discharge circuit 3a or 3b to the pressure chamber 4a of the mechanical brake 4. Therefore, the braking force on the hydraulic motor 3 of the mechanical brake device 4 is released.

When the hydraulic motor 3 is driven, the direction switching valve 80 is
When returning to the neutral position 80a, the supply / discharge circuits 3a and 3b are both connected to the tank, so the high-pressure selection valve 81 returns to the neutral position 81a, and connects the pressure chamber 4a of the mechanical brake 4 to the tank. Therefore, although the supply / discharge circuits 3a and 3b of the hydraulic motor 3 are both connected to the tank, the braking force of the mechanical brake device 4 acts on the hydraulic motor 3, and the hydraulic motor 3 is stopped by this braking force.

[Problems to be solved by the invention]

The first prior art described above (the one shown in FIG. 5 (a))
Has both a fluid brake device (a brake device using the brake valves 71 and 72) and the mechanical brake device 4, and the structure is complicated. In this regard, the structure of the second prior art (FIG. 6) utilizing the mechanical brake device for the dynamic braking force seems to be simple at first glance.
However, in the second prior art, a mechanical brake is provided with a brake shoe at an output portion of a hydraulic motor, that is, a cylinder block of a swash plate type hydraulic motor to apply a braking force, as shown in, for example, Japanese Utility Model Publication No. 2-10062. It is a configuration to make it. Most of the braking force is converted to heat. Therefore, when a braking force is applied for a long time to prevent self-propelled operation, such as when the construction machine descends on a slope, the heat generated by the braking force does not affect other parts of the hydraulic motor. Need to be cooled sufficiently. If this cooling is not carried out with sufficient spare power, heat will concentrate on a part of the brake shoe of the mechanical brake, and the oil will burn in that part.If the carbon generated by the burning of the oil adheres to the brake shoe, the friction coefficient will decrease significantly. Problems such as a decrease in braking force occur.

A device for this cooling also needs to be provided around the mechanical brake. Therefore, there is a problem that the hydraulic motor itself becomes large.

From the above points, the conventional technology has a problem that the number of parts for the brake device is large, and there is a problem that if the number of parts is reduced, the hydraulic motor becomes large.

[Means for solving the problem]

The technical means of the present invention for solving the problems of the prior art described above includes a supply / discharge circuit for supplying / discharging oil pressure to / from a hydraulic motor for driving a traveling device of a crawler vehicle, and a main relief valve via a counter balance valve. And a hydraulic pressure chamber connected to a direction switching valve connected to the hydraulic pump, and a hydraulic chamber of a mechanical brake device provided in the hydraulic motor is connected to a tank when the counter balance valve is in a neutral position, and is connected to a tank when the counter balance valve is in a switching position. A traveling device for a roller vehicle connected to a high-pressure supply / discharge circuit on the upstream side of the vehicle, wherein when the directional control valve is returned from an operation position to a neutral position, the mechanical brake device applies a braking force to the hydraulic motor. At the same time, the counter balance valve is returned to the neutral position after a certain time from when the directional control valve is returned to the neutral position. The hydraulic pressure on the discharge side of the hydraulic motor at the time of is set to be equal to or less than the set value of the main relief valve so that both the hydraulic braking force by the counterbalance valve and the mechanical braking force by the mechanical brake device act on the hydraulic motor. And when the directional control valve is returned from the operating position to the neutral position, the mechanical brake device applies a braking force to the hydraulic motor, and the counterbalance valve substantially stops when the rotation of the hydraulic motor stops. At the same time, it is returned to the neutral position.

(Operation)

The present invention having the above technical means is characterized in that when the directional control valve is returned to the neutral position, the hydraulic motor is acted on by the braking force of the mechanical brake device, and the directional control valve is returned to the neutral position for a fixed time. Later, the counterbalance valve was returned to the neutral position, and the hydraulic braking force of the counterbalance valve was applied to the hydraulic motor.
The mechanical brake device can be used as a short-time dynamic brake only when the construction machine stops. For this reason, a conventional mechanical brake device for a parking brake can be used. In addition, when the slope of the construction machine is descending, the fluid brake by the counterbalance valve is actuated to control the descending speed of the construction machine, so that the brake valve is omitted to simplify the configuration and the operating conditions of the mechanical brake device. To minimize heat generation,
This makes it possible to make a small hydraulic motor.

〔Example〕

Hereinafter, examples of the present invention will be described. In FIG. 1 showing a hydraulic circuit of a first embodiment, a hydraulic motor 3 has a mechanical brake device 4 and is connected to the counterbalance valve 1 by supply / discharge circuits 3a and 3b. A direction switching valve 5 is provided between the counter balance valve 1 and the pump 6.
Is provided.

The mechanical brake device 4 has a piston 4a that receives both a pressing force by the hydraulic pressure of the pressure chamber 4b and a pressing force by the spring force of the spring 4c. As shown in FIG. 3 (a), the specific structure of the piston 4a is such that its tip abuts on a separator plate 33 movably arranged in the axial direction of the main body 31 of the hydraulic motor 3, and the pressure of the pressure chamber 4b is reduced. When the oil is discharged to the tank, it is provided on the main body so that the oil can be moved in the axial direction of the cylinder block 35 of the hydraulic motor 3 via the separator plate 33 by the pressing force of the spring 4c, and alternately with the separator plate 33. In this configuration, the arranged friction plate 34 is pressed to apply a braking force to the cylinder block 35.

The pressure chamber 4b of the mechanical brake device 4 has a first
As shown in the figure, when the counter balance valve 1 is in the neutral position, the pilot circuit 8 connected to the tank 9 is connected. 8a provided in the pilot circuit 8 is a check valve 8c
And the throttle 8b are connected in parallel, and the supply / discharge circuit 5a or
This is a restrictor for supplying pressure oil from 5b to the pressure chamber 4b of the mechanical brake device. This restrictor
When the switching valve 5 is switched from the neutral position 51a to the switching position 51c or 51b by 8a, the release of the braking force of the mechanical brake device is slightly delayed from the start of the hydraulic motor 3.

The counterbalance valve 1 has a neutral position 1a and two switching positions 1b and 1c, and has a pilot chamber connected via a restrictor 1e to a supply / discharge circuit 5a connected to the direction switching valve 5.
1g, a pilot chamber 1h connected to the supply / discharge circuit 5b via a restrictor 1f, and springs 1i and 1j are provided so as to correspond to pressing forces by hydraulic pressure acting on the pilot chambers 1g and 1h. The specific structure of this counterbalance valve 1 is the third
As shown in FIG.
13 is slidably fitted therein, and springs 1i
It has pilot rooms 1g and 1h provided with 1j. The pilot chambers 1g, 1h are connected to the supply / discharge circuits 5a, 5b through restrictors 1e, 1f passages 13e, 13f provided at both ends of the spool 13.
Connect to As shown in FIG. 3 (d), the restrictor 1e is a check valve 1e2 which abuts a valve seat 13b provided in a passage 13e.
And a restrictor 1e1, which restricts the flow of pressure oil from the pressure chamber 1g toward the passage 13e. Therefore, the time required for the spool 13 to return from the switching position 1b to the neutral position 1a is adjusted by the throttle 1e1. Although FIG. 32 (d) describes the configuration of the restrictor 1e, the same applies to the restrictor 1f. Therefore, from the switching position 1c of the counter balance valve 1 to the neutral position
The return time to 1a is adjusted by the aperture 1f1.

A passage 15 connected to the pilot circuit 8 and a passage 16 connected to the pilot circuit 9a connected to the tank 9 are provided in the counterbalance valve main body 11 so that the spool 13 is in a neutral position as shown in FIG. When in position, slit 13a
Is communicated with. The passages 17a and 17b communicating with the supply / discharge circuits 5a and 5b via the passages 13e and 13f of the spool 13 are closed by the inner hole 12 at the neutral position of the spool 13 as shown in FIG. Have been. Note that the slit 13a and the passages 17a and 17b have a 90 ° position difference as shown in FIG. 3 (a), but in FIG. 3 (c), the slit 13a is shifted by 90 ° and the passages 17a and 17b are shifted. It is indicated by a broken line on the same plane as 17b.

When the directional control valve 5 is not operated and the neutral position 51a is at the neutral position 51a, the supply / discharge circuits 5a and 5b are connected to the tank 7, so that both the pilot chambers 1g and 1h have the tank pressure. And the spool 13 has springs 1i at both ends thereof,
1j holds the neutral position 1a (the position in FIG. 3 (b)). When the spool 13 is at the position shown in FIG. 3B, the pilot circuit 8 of the mechanical brake device 4 is connected to the tank 9 via the passage 15, the slit 13a, and the passages 16 and 9a. The oil pressure in the pressure chamber 4b becomes the tank pressure, and the hydraulic motor 3 receives a braking force due to the pressing force of the spring 4c.

When the direction switching valve 5 is operated to the switching position 51c, the discharge hydraulic pressure of the pump 6 is changed from the supply / discharge circuit 5b to the counter balance valve 1
This acts on the supply / discharge circuit 3b via the check valve 14b of the balance circuit. However, since the counterbalance valve 1 is at the neutral position 1a, the supply / discharge circuit 3a is not connected to the supply / discharge circuit 5a, and the hydraulic pressure of the supply / discharge circuits 5b, 3b rises. The supply / discharge circuit 5b
Since the middle passage 13f communicates with the pilot chamber 1h via the restrictor 1f, the hydraulic pressure of the pilot chamber 1h also increases in accordance with the increase in the hydraulic pressure of the supply / discharge circuit 5b. Then, when the pressing force of the hydraulic pressure of the pilot chamber 1h exceeds the pressing force of the spring 1j, the counterbalance valve 1 switches to the switching position 1c.

Thus, the counter balance valve 1 is switched to the switching position 1c.
, The supply / discharge circuit 3a is connected to the supply / discharge circuit 5a.
The pilot circuit 8 is also connected to the supply / discharge circuit 5b of the pressure chamber 4b of the mechanical brake device 4 via the passage 13f and the passage 17b of the spool 13. Accordingly, although the hydraulic pressure also acts on the pressure chamber 4c, the pressure chamber 4c operates with a delay in the time that it is restricted by the restrictor 8b of the restrictor 8a. In the above state, the hydraulic motor 3 starts to rotate, but the braking force of the mechanical brake device 4 is slightly delayed from the start of the hydraulic motor 3 so as to be released. In other words, the timing of starting the hydraulic motor and the timing of releasing the braking force of the mechanical brake device 4 are overlapped, and when the construction machine starts from a state of climbing a hill, the hydraulic motor 3 starts with sufficient torque generated. This makes it possible to perform a smooth start. When the direction switching valve 5 is operated from the neutral position 51a to the switching position 51b, the supply / discharge circuit 5a and the supply / discharge circuit 3a are connected via the check valve 14a,
The hydraulic pressure in the pilot chamber 1g rises and the counterbalance valve 1
From the neutral position 1a to the switching position 1b. By this switching, the supply / discharge circuit 5a is connected to the pilot circuit 8 of the mechanical brake device 4 as described above, and the braking force is released slightly after the start of the hydraulic moat 3.

In the circuit of FIG. 1, reference numeral 60 is a main relief valve which limits the discharge oil pressure of the pump 6 to a constant value. FIG. 3 (a) shows a swash plate type hydraulic motor. In FIG. 3 (a), reference numeral 37 denotes an output shaft which is supported by a bearing on a main body 31 and a cylinder block 35 is spline-coupled. Yes,
It penetrates a swash plate 38 fixed inside the main body 31. A plurality of pistons 39 provided on the cylinder block 35 are in contact with the slopes 38a of the swash plate 38 via the shoes 39a. Further, 40 is a valve plate for supplying pressure oil from the supply / discharge circuits 3a and 3b,
Supply / discharge to the cylinder block.

With respect to the operation of the first embodiment shown in FIG.
FIG. 4 shows the relationship between the number of rotations and the change in the hydraulic pressure of the supply-side circuit and the discharge-side circuit and the braking force.

In FIG. 4, assuming that the direction switching valve 5 is now operated from the neutral position 51a to the switching position 51c at time t1, the discharge port pressure oil of the hydraulic pump 6 is supplied from the supply / discharge circuit 5b to the counterbalance valve 1 in the opposite direction. It flows into the hydraulic motor 3 from the supply / discharge circuit 3b via the stop valve 14b. At this time, the supply / discharge circuit 3a and the supply / discharge circuit 5a are shut off because the spool 13 of the counterbalance valve 1 has not moved yet, so the hydraulic pressure on the supply / discharge circuit 3b side rises, and the counterbalance valve 1 is switched. Switch to position 1c. Since the time during this period is extremely short, it can be considered that the time has been switched to approximately the time t1. By this switching, the supply and discharge circuit
3a and 5a are connected, and a supply / discharge circuit 5b and a pressure chamber 4b of the mechanical brake device 4 are connected via a pilot circuit 8. Therefore, the brake is released at time t2 after the set time T11 of the restrictor 8a is delayed from time t1. However, since a large inertial load acts on the hydraulic motor 3, the rotation speed of the hydraulic motor 3 gradually increases as indicated by M1 in the curve M. Therefore, the discharge hydraulic pressure of the hydraulic pump 6 rises to the set pressure of the relief valve 60 as shown by b1 in the curve b. When the hydraulic pressure of the hydraulic pump 6 is maintained at the set pressure of the relief valve 60 for a while, the hydraulic motor 3 rotates against the load and changes its rotation speed to a speed (M2) corresponding to the discharge oil amount of the hydraulic pump 6. ). At this time, since the speed slightly increases, the hydraulic pressure of the supply / discharge circuit 3b drops rapidly, and the counterbalance valve throttles the supply / discharge circuit 3a and the supply / discharge circuit 5a. Rises as shown by a1 in the curve a, and a braking force by hydraulic pressure acts on the hydraulic motor 3, so that the temporary rotation speed of the hydraulic motor 3 decreases as shown by the curve M3. However, the hydraulic pressure of the hydraulic pump 6 rises again as indicated by b2 in the curve b because the supply / discharge circuit 3a on the discharge side is throttled. Due to this hydraulic pressure, the rotation speed of the hydraulic motor 3 increases again.

In this manner, the rotation of the hydraulic motor 3 is such that the output of the hydraulic motor 3 and the inertial load are balanced and settle to a constant rotation indicated by M4 in the curve M.

As described above, when the rotation speed of the hydraulic motor 3 becomes M4 and the start of the inertial load ends, the hydraulic pressure of the supply / discharge circuit 3b on the supply side becomes
b3. When the direction switching valve 5 is returned to the neutral position 51a at time t3 to stop the hydraulic motor 3 in this state, the supply / discharge circuits 5a and 5b are both connected to the tank 7, so that the hydraulic pressure of the supply / discharge circuit 3b is Becomes the tank pressure as shown by b4 of the curve b. Pilot chamber 1h for counterbalance valve 1
Is connected to the tank 7 from the supply / discharge circuit 5b via the throttle 1f1. At the same time, the pressure chamber 4 b of the mechanical brake device 4 is also moved from the pilot circuit 8 to the spool 13 of the counterbalance valve 1.
Are connected to the tank 7 from the supply / discharge circuit 5b through the passages 17b and 13f. Therefore, the counterbalance valve 1 is provided with the direction switching valve 5
From the time when the lever is operated to the neutral position at 51a, and the pressing force of the spring 1j,
The pilot chamber 1h returns to the neutral position after a time T31 determined by the relationship between the volume of the pilot chamber 1h and the opening area of the restrictor 1f1 of the restrictor 1f.

Further, the pressure oil in the pressure chamber 4b of the mechanical brake device 4 becomes almost the tank pressure at the same time when the pressure oil in the supply / discharge circuit 5b becomes the tank pressure. That is, when the pressure oil in the pressure chamber 4b flows out to the supply / discharge circuit 5b via the pilot circuit 8 as shown in FIG. 3 (e), the piston 4a is pressed by the spring 4c to generate the pressure oil in FIG. 3 (a). , And presses the right separator plate 33. Therefore, the braking force increases as shown by BR1 on the curve BR. At this time, the braking force is applied to the separator plate 33 because the friction plate 34 is rotating.
Is a dynamic friction coefficient, and is a braking force indicated by BR1 which is smaller than the braking force in the case of the static friction coefficient indicated by BR3 in the curve BR of FIG. In addition,
BR2 on the curve BR between BR1 and BR3 is a fluid braking force applied to narrow the supply / discharge circuit 3a.

In this manner, the counterbalance valve 1 returns to the neutral position 1a after the rotation speed of the hydraulic motor is reduced due to the application of the braking force of the mechanical brake device 4, so that the pressure increase of the hydraulic circuit 3a is changed to a3 of the curve a. It can be reduced as shown. Therefore, the impact on the operator is reduced. If the operator prefers the one having a larger impact at the time of stopping according to the preference of the operator, the interval of the time T31 may be made shorter according to the size of the aperture 1e1. When the directional control valve 5 is returned to the neutral position and the counterbalance valve 1 is returned to the neutral position almost at the same time as the curve a4 shown by the chain line, the hydraulic motor 3 rotates high and a large inertia load acts. Since the hydraulic circuit is sometimes closed, a large impact is generated. Therefore, as a rough guide, if the impact at the time of starting and the impact at the time of stopping are made substantially equal, the time T31 is set so that the height of a3 of the curve a is almost equal to the height of b1 of the curve b.
Should be adjusted.

When the load driven by the hydraulic motor 3 is large or when the inertial load is large as in a traveling device of a large construction machine, as shown in FIG. 4, time T31 is changed to time t3 during rotation of the hydraulic motor. When set within the range of ~ t5, the mechanical brake device and the counterbalance valve 1
Is returned to the neutral position, and both of the fluid brakes operate simultaneously. For this reason, the shock at the time of stoppage increases. In such a case, by stopping the time T31 from the time t3 when the direction switching valve 5 returns to the neutral position to the time t5 when the rotation of the hydraulic motor stops, the shock can be stopped with less shock. At that time, the height of the curve a3 becomes the tank pressure as shown by the broken line.

In the above, the direction switching valve 5 is moved from the neutral position 51a to the switching position 5
1b and returning from the switching position 51b to the neutral position 51a.
The same applies to the case of returning to 1a. In FIG. 4, curves a and b are interchanged, and t6 corresponds to t1.

When the construction machine descends on the slope, the situation is as follows.
That is, when the pilot pressure of the counter balance valve is reduced, the supply / discharge circuit 3a on the discharge side of the hydraulic motor 3 and the supply / discharge circuit 3
5a or between the supply and discharge circuit 3b and the supply and discharge circuit 5b,
The fluid brake force is applied to the hydraulic motor 3, but the pressure chamber 4c of the mechanical brake device 4 is connected to the high pressure side of the supply / discharge circuit 5a or 5b. At this time, the brake force of the mechanical brake device 4 is released. .

Next, a second embodiment shown in FIG. 2 will be described. First
The difference between the embodiment and the second embodiment is that the switching valve 50 is inserted into the pilot circuit 8 'of the pressure chamber 4b of the mechanical brake 4, and the pilot circuit 51 of the switching valve 50 is connected to the counterbalance valve 1. It was done.

The switching valve 50 is located at the switching position 50a when the pressing force by the hydraulic pressure of the pilot chamber 50c is smaller than the pressing force of the spring 50d, and connects the pilot circuit 8 'to the tank 9. When the pressing force of the pilot chamber 50c due to the oil pressure is stronger than the pressing force of the spring 50d, the position is switched to the switching position 50b, and the pilot circuit 8 'and the pilot circuit 51 are connected.

The above configuration is different from that of the first embodiment, in which the switching valve 50 is not affected by the fluctuation of the hydraulic pressure of the unload circuit 5c.

In the case of the first embodiment, when the directional control valve 5 is returned from the operating position to the neutral position, the pilot circuit 8
Unloading circuit from 5a or 5b via directional control valve 5
Connect to 5c. Since the unload circuit 5c actually doubles as the unload circuit of the hydraulic circuit that operates another device, the unload circuit 5c may be unstable. (The oil pressure of the unload circuit rises when the amount of oil discharged from other devices becomes large.) Therefore, when the oil pressure fluctuation of the unload circuit 5c acts on the hydraulic chamber 4b of the mechanical brake device 4, the braking force changes. The second embodiment is to prevent this point, and the switching valve 50 is used.
When the set pressure of the spring 50d is set to the maximum value of the fluctuation of the unload circuit 5c, the pilot circuit 51 operates via the counter balance valve 1 to unload the supply / discharge circuit 5a or the 5b directional switching valve 5. The hydraulic chamber 4b of the mechanical brake device 4 can be connected to the tank 9 so that the braking force can be maintained at a predetermined value even when the hydraulic pressure is changed in the unload circuit 5c.

〔The invention's effect〕

According to the brake operating method of the present invention, when the drive of the hydraulic motor for driving the inertial load is stopped from the operating position of the direction switching valve to the neutral position, the return time from the operating position of the counter balance valve to the neutral position is reduced. Adjust and
Since the braking force of the mechanical brake device is applied to the hydraulic motor from the time of operation of the directional control valve to the neutral position, when the inertia load is extremely large as in a traveling device of a large construction machine, the counterbalance valve 1 is not used. By adjusting the return time to the time when the rotation of the hydraulic motor stops, it is possible to reduce the shock due to the inertial load when the hydraulic motor stops.

In the case of a traveling device of a small construction machine having a small inertia load, the return time of the counterbalance valve is set to a value before the hydraulic motor is stopped, so that the maneuverability (counter balance in response to an operator's travel bending command) is reduced. Quick return of the valve to the neutral position provides good response to commands.
Even in the case of moving down a slope, if the return of the spool of the counter balance valve to the neutral position is accelerated, the self-propelled time is shortened. ) Will be better.

Compared with a conventional brake device shown in FIG. 5 (a) which uses a mechanical brake device as a dynamic brake device, a fluid brake using a counterbalance valve and a mechanical brake device are used in combination to reduce the slope of a construction machine. When long-term speed control is required, such as when descending, the mechanical brake is used without using the fluid brake by the counterbalance valve (the discharge side is throttled according to the operation amount of the direction switching valve). Since the mechanical brake device is used as a dynamic brake for a very short time at the time of the stop, the capacity of the mechanical brake may be as small as that of a conventional parking brake. The heat generated by the mechanical brake is also small.

Therefore, even if the device is simplified (the brake valve is omitted),
This has the effect that it is not necessary to increase the size of the hydraulic motor.

In the conventional brake device shown in FIG. 5 (a), when the directional control valve 73 is operated to the neutral position, the counter balance valve 70 is connected to the discharge side supply / discharge circuit (in the case of rotation in the direction of the arrow 90, supply / discharge is performed). The circuit 3b) is closed, and the hydraulic pressure of the supply / discharge circuit on the discharge side is controlled by the brake valve as shown in FIG. 5 (b). At this time, the supply / discharge circuit 3a on the suction side of the hydraulic motor 3 is connected to the tank via the check valve 91, and the oil in the tank is sucked. At this time, since the pressure for suction is 1 kgf / cm ² at the maximum, the hydraulic motor 3 cannot supply necessary oil, and cavitation occurs on the suction side. Transferred and destroyed. When cavitation occurs on the suction side of the hydraulic motor 3 and is crushed on the discharge side, erosion occurs at the cylinder block of the hydraulic motor and at the valve plate. In this regard, the present invention allows the return of the counter balance valve to the neutral position after a certain period of time from when the directional control valve is set to the neutral position, or until the rotation of the hydraulic motor stops. Therefore, even if cavitation occurs on the suction side of the hydraulic motor 3, the cavitation is only discharged to the discharge side, so that erosion can be prevented.

Further, in the prior art shown in FIG. 5 (a), the cavitation generated on the suction side is destroyed by a high pressure, so that the cavitation noise is increased. However, the present invention reduces the hydraulic pressure generated on the discharge side to a small value. , So there is almost no destruction sound. Further, since a high pressure (more than the set pressure of the relief valve) is not generated at the time of stop, it is not necessary to adopt a configuration that can withstand a higher pressure, so that the counterbalance valve and the hydraulic motor can be made thinner and lighter.

In addition, the present invention overlaps the braking force of the mechanical brake device 4 with the braking force of the counterbalance valve (the overlapping portion of the portion BR1 indicating the mechanical braking force and the portion BR2 indicating the fluid braking force of the curve BR in FIG. 4). )
Thus, as shown in FIG. 5 (b), it is possible to obtain the same brake characteristics as the conventional brake characteristics (in FIG. 5 (b), the pressure becomes equal to the brake torque).
Therefore, there is an effect that even if the brake valve is omitted, the same brake feeling as when there is a brake valve can be obtained.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a first embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of a second embodiment of the present invention, and FIG. 3 (a) is a hydraulic motor and a counterbalance of the present invention. FIG. 3 (b) is a cross-sectional view of the counterbalance valve, FIG. 3 (c) is an enlarged cross-sectional view of a portion of FIG. 3 (b), FIG. (D) shows the restrictor 1e of the counterbalance valve
FIG. 4 is a characteristic curve diagram showing the relationship between the hydraulic pressure of the supply / discharge circuit, the rotation of the hydraulic motor, and the braking force when the drive of the hydraulic motor is stopped by operating the direction switching valve; 5 (a) is a hydraulic circuit diagram of the prior art, FIG. 5 (b) is a characteristic curve diagram of the brake valve in FIG. 5 (e), and FIG. 6 is a hydraulic circuit diagram of the prior art. 1 ... Counter balance valve, 3 ... Hydraulic motor, 3a, 3b
…… Supply / discharge circuit, 4 …… Mechanical brake device, 4a ……
Piston, 4b Pressure chamber, 4c Spring, 5 Directional valve, 6 Pump 60 Main relief valve 7, 9
…tank.

Claims (2)

(57) [Claims] A directional switching valve in which a hydraulic motor with a mechanical brake device for driving a traveling device of a crawler vehicle is connected to a hydraulic pump having a main relief valve via a counterbalance valve with a supply and discharge circuit for supplying and discharging pressure oil. The hydraulic chamber of the mechanical brake device provided in the hydraulic motor is connected to the tank when the counter balance valve is in the neutral position, and the high pressure supply and discharge on the upstream side of the counter balance valve is in the switching position. A traveling device for a crawler vehicle configured to be connected to a circuit, wherein when the direction switching valve is returned from an operating position to a neutral position, the mechanical brake device applies a braking force to the hydraulic motor, and the counter balance valve moves in a direction. After a certain period of time from when the switching valve is returned to the neutral position, the switching valve is returned to the neutral position. The discharge side oil pressure is set to be equal to or less than the set value of the main relief valve, and both the hydraulic brake force by the counter balance valve and the mechanical brake force by the mechanical brake device act on the hydraulic motor. Crawler vehicle braking method. 2. A hydraulic motor with a mechanical brake for driving a traveling device of a crawler vehicle, a supply / discharge circuit for supplying / discharging pressure oil is connected to a direction switching valve via a counterbalance valve, and provided on the hydraulic motor. A traveling device for a crawler vehicle having a configuration in which a hydraulic chamber of a mechanical brake device is connected to a tank when the counterbalance valve is in a neutral position, and is connected to a high-pressure supply / discharge circuit upstream of the counterbalance valve when the counterbalance valve is in a switching position. In the above, when the directional control valve is returned from the operating position to the neutral position, the mechanical brake device applies a braking force to the hydraulic motor, and the counter balance valve is moved to the neutral position almost simultaneously when the rotation of the hydraulic motor stops. A brake actuation method for a crawler vehicle, characterized by returning to a normal state.