JPH076523B2 - Speed change device for hydraulic motor for vehicle running - Google Patents

Description

TECHNICAL FIELD The present invention relates to a speed switching device for a hydraulic motor for traveling of a construction machine or other vehicle.

[Conventional technology]

Conventionally, this type of speed switching device includes, for example, a crawler driving device (actually No. 62-45401) as shown in FIG. 3, a speed switching valve and hydraulic circuit of a swash plate type two-speed speed motor as shown in FIG. JP-A-56-96181).

FIG. 3 shows a pair of a swivel joint 53 that connects a manual switching valve 51 connected to a pump and a tank and a variable displacement hydraulic motor 52 to a traveling frame and a turning frame of a crawler vehicle. It is connected by the supply and discharge paths 54 and 55.

The pilot valve 63 takes the left position when the pilot pressure acting on it is less than a predetermined pressure, and the small cylinder 57 and the large cylinder
Since the motor drive pressure is introduced to 58, the hydraulic motor 52 rotates at high speed (small capacity) due to the difference in cylinder diameter. When the pilot pressure becomes equal to or higher than the predetermined pressure, the pilot valve 63 takes the right position, and the large cylinder 58 communicates with the drain passage 64, and the small cylinder 57
Since the motor drive pressure is introduced to, the hydraulic motor 52 rotates at a low speed (large capacity).

What is shown in FIG. 4 is the swash plate 7 of the left and right hydraulic motors 71, 71 '.
Cylinders 73, 74, 73 ', 74' are provided in 2, 72 ', and rod chambers 75, 75' of one cylinder 73, 73 'are connected to pilot switching valve 7
6, 76 ', the pilot switching valves 76, 76' communicate with the tank 77 at position a, and the check valves 78, 78 'at position b.
Counter balance valve 79, 79 ', multiple control valve 80, 8
Connect to pumps 81, 81 'through 0'. Further, the head chambers 82, 82 'of the other cylinders 74, 74' have pilot switching valves 76, 7 '.
It is connected to an electromagnetic switching valve 83 together with a pilot port 6 ', and the electromagnetic switching valve 83 is connected to the tank 77 at position a and is connected to both pumps 81 and 81' via a shuttle valve 84 at position b.

In this device, when the electromagnetic switching valve 83 is switched to the position a according to the operator's command, the head chambers 82, 82 'of the cylinders 74, 74' and the pilot ports of the pilot switching valves 76, 76 'are communicated with the tank 77, Since the pilot switching valves 76, 76 'are switched to the position b and guide the pressure oil from the counter balance valves 79, 79' to the rod chambers 75, 75 'of the cylinders 73, 73', the swash plates 72, 72 'are used.
And the hydraulic motors 71, 71 'rotate at a low speed. When the electromagnetic switching valve 83 is switched to the position b according to the operator's command, the pressure oil from the shuttle valve 84 is transferred to the cylinder.
74, 74 'head chamber 82, 82' and pilot switching valve 76, 7
Guided to 6'pilot port, pilot switching valve 76,
76 'is switched to the position a and the rod chamber 7 of the cylinders 73, 73' is changed.
Since 5,75 'is connected to the tank 77, the tilt angle of the swash plates 72, 72' is minimized, and the hydraulic motors 71, 71 'rotate at high speed.

[Problems to be Solved by the Invention]

The hydraulic motor 52 shown in FIG. 3 switches from high-speed rotation to low-speed rotation when the pressure fluid guided to the hydraulic motor 52 is equal to or higher than a predetermined pressure, and low-speed rotation when the pressure fluid is less than the predetermined pressure, regardless of other hydraulic motors. Since it switches from high speed to high speed, the left and right hydraulic motors are switched depending on the machine pressure difference between the left and right hydraulic motors of the crawler vehicle and the difference in the setting spring 65 of the pilot valve 63. The tamping of the vehicle is often misaligned, in which case the vehicle makes a turn.

In the structure shown in FIG. 4, the left and right hydraulic motors 71, 71 'can be simultaneously switched to low speed rotation and high speed rotation according to an operator's command, so that the vehicle can be prevented from bending. However, this method requires switching to low speed running each time when a vehicle encounters a torque shortage such as a slope, a corner, or a wetland during high-speed running. There is a problem that the operator gets tired.

The present invention has been made in view of the above points, and when the high-pressure side pressure of at least one hydraulic motor becomes higher than a predetermined pressure during high-speed traveling, both hydraulic motors are automatically switched to low-speed rotation, and By switching, even if the load pressure drops slightly, it will not return to the high speed side to stabilize running and simplify operation, and even if instantaneous high pressure (surge pressure) occurs at startup etc., low speed An object of the present invention is to provide a speed switching device for a hydraulic motor for vehicle traveling that does not switch to the side.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, the pilot pressure is supplied to and discharged from the pilot port of the suction amount control means provided in each of the variable displacement type hydraulic motors by means of a switching valve so that both hydraulic motors can be operated. In a speed switching device for a hydraulic motor for vehicle traveling that is rotated at a low speed or a high speed, a shuttle valve that selects and takes out the high-pressure side pressure from the supply and discharge passages of both hydraulic motors, the switching valve and the both intake amounts When the high pressure side pressure from the shuttle valve is equal to or higher than a predetermined pressure, the pilot ports of the both suction amount control means are connected to the tank, and are connected to the pilot port of the control means. Both the automatic switching valve connected to the switching valve and both suction amount control means when the high pressure side pressure from the shuttle valve after the automatic switching valve has switched over a predetermined pressure is lower than the predetermined pressure In which it characterized in that a self-holding circuit for holding a connection state between the pilot port and the tank.

A surge pressure absorption valve may be provided in a passage connecting the shuttle valve and the pressure oil inlet of the automatic switching valve.

[Work]

If the pilot ports of both suction amount control means are connected to the tank by the switching valve, the suction amount control means increases the suction amount of the hydraulic motor, so that both hydraulic motors simultaneously rotate at low speed. When the pilot pressure is introduced to the pilot ports of both suction amount control means, the suction amount control means reduces the suction amount of the hydraulic motor, so that both hydraulic motors simultaneously rotate at high speed.

Now, when the high-pressure side pressure of at least one hydraulic motor rises above a predetermined pressure during high-speed running of the vehicle, the automatic switching valve operates and the pilot ports of both intake amount control means are connected to the tank, so The motors automatically rotate at the same low speed. This low-speed state is held by the self-holding circuit as long as the pressure on the high-pressure side of the hydraulic motor falls below the predetermined pressure but is within the specified pressure.

Further, even if an instantaneous high pressure (surge pressure) is generated in the circuit at the time of start-up, since it is absorbed by the surge pressure absorption valve, both hydraulic motors do not switch to the low speed side.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the pumps 1, 1 ′ together with the pilot pump 2 are
Control valve 4, while being connected to the engine 3
4'and counterbalance valves 5, 5'through variable displacement hydraulic motors 6, 6 '.

The hydraulic motors 6, 6'are provided with suction amount control means 8, 8'for increasing / decreasing the suction amount of the hydraulic motors by supplying / discharging pilot pressure. In this embodiment, the suction amount control means 8, 8'includes swash plate tilting cylinders 9, 10, 9 ', 10' connected to the swash plates 7, 7 '.
And shuttle valves 13, 13 'connected to the supply / discharge paths 11, 12, 11', 12 'of the hydraulic motors 6, 6', and the swash plate tilting cylinders 9, 1 '
Shuttle valve 0, 9 ', 10' by supplying and exhausting pilot pressure
13, 13 'and the pilot switching valves 15, 15' of four ports and two positions which are alternately communicated with the tanks 14, 14. Of course, as the inhalation amount control means 8 and 8 ', known means other than this embodiment can be appropriately adopted.

The pilot chambers 16, 16 'of the pilot switching valves 15, 15' are connected in parallel to the automatic switching valve 17 by the pilot passage 18, and the automatic switching valve 17 is a switching valve connected by the pilot passage 19, which is an electromagnetic switching in this embodiment. Pilot pump 2 and tank 21 are alternately connected via valve 20.

In the pilot chamber 24 of the automatic switching valve 17, the control valve 4
From the shuttle valve 22 connected to the supply / discharge paths 11 and 12 between the counter balance valve 5 and the supply / discharge paths 11 'and 12' between the control valve 4'and the counter balance valve 5 '. The pressure is guided through a passage 33 having a surge pressure absorption valve 23 interposed. When the spool pressing force due to the high pressure side pressure from the shuttle valve 22 overcomes the setting spring 25, the automatic switching valve 17 switches from the position a that communicates the pilot passages 18 and 19 to the position b and blocks the pilot passage 19. The pilot passage 18 communicates with the tank 21. When the automatic switching valve 17 is switched to the position b, even if the high pressure side pressure from the shuttle valve 22 is lowered to a specified pressure lower than the pressure (hereinafter, referred to as a predetermined pressure) for switching the automatic switching valve 17 to the position b, the position b is kept. , Held by the self-holding circuit 34. This self-holding circuit 34
Is a pilot chamber 27 arranged in parallel with the pilot chamber 24 at one end of the spool 26, and a passage connecting to the pilot chamber 27.
Since 28 and this passage 28 and the passage 29 connected to the pilot chamber 24 are constituted by the passage 30 of the spool which communicates at the position b, when the automatic switching valve 17 is switched to the position b, the high pressure from the shuttle valve 22 is increased. The side pressure also acts on the pilot chamber 27, reducing the limit of the high pressure side pressure that holds the position b. The specified pressure which is the lower limit pressure is determined by the size of the pilot chamber 27. When the high-pressure side pressure from the shuttle valve 22 falls below the specified pressure, the automatic switching valve 17 switches from the position b to the position a.

When the automatic switching valve 17 is switched to the position a, the pilot passage 18
And 19 communicate with each other, passage 29 is blocked, passage 28 is a tank
Connect to 21.

Next, the operation of this embodiment will be described. In FIG.
With the control valves 4 and 4'in the functional position, the solenoid switching valve 20
When both the automatic switching valve 17 and the automatic switching valve 17 are switched to the position a, the pilot switching valves 15 and 15 'are set to the position a by the springs 31 and 31', and the swash plate tilting cylinders 10 and 10 'are connected to the tank 21. ,
Since the pressure fluid from the shuttle valves 13, 13 'is guided to the swash plate tilting cylinders 9, 9', the swash plates 7, 7 increase the suction amount of the motor, and the hydraulic motors 6, 6'rotate at high torque and low speed. become.

When the electromagnetic switching valve 20 is switched to the position b, the pilot switching valves 15 and 15 'are simultaneously switched to the position b by the pilot pressure from the pilot pump 2 introduced to the pilot chambers 16 and 16', and the swash plate tilts. The transfer cylinders 9 and 9'communicate with the tank 21, and the shuttle valves 13 and 13 'are connected to the swash plate tilt cylinders 10 and 10'.
Since the pressure fluid from the swash plate is introduced, the swash plates 7 and 7'reduce the suction amount of the motor and the hydraulic motors 6 and 6'become a small torque high speed rotation.

When the hydraulic motors 6 and 6'are rotating at high speed with small torque,
For example, when the high-pressure side pressure of the hydraulic motor 6 rises above a predetermined pressure, the automatic switching valve 17 switches from position a to position b,
As shown in FIG. 2, since the pilot chambers 16 and 16 'of both pilot switching valves 15 and 15' are communicated with the tank 21, the pilot switching valves 15 and 15 'are returned to the position a, and the hydraulic motors 6 and 6 are driven. ′ Has large torque and low speed rotation. In this case, the pilot passage 19
Is blocked, the oil discharged from the pilot pump 2 is discharged to the tank 21 via the relief valve 32. Meanwhile, the passage
Since 28 and 29 communicate with each other through the passage 30, the shuttle valve 22
The high-pressure side pressure also acts on the pilot chamber 27, and the low-speed state is maintained when the high-pressure side pressure acting on the automatic switching valve 17 is equal to or higher than the specified pressure.

Since the surge pressure absorption valve 23 absorbs the surge pressure generated in the circuit at the time of starting, it is possible to prevent the automatic switching valve 17 from being switched to the position a due to the surge pressure.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

When the high-pressure side pressure of at least one of the hydraulic motors exceeds a predetermined pressure when the vehicle is running at high speed, both hydraulic motors automatically rotate at the same time at low speed, and this low-speed state causes the high-pressure side of both hydraulic motors. Even if the pressure drops below the predetermined pressure, it will be maintained above the specified pressure, which simplifies the driving operation and helps stabilize the running.

Even if a momentary high pressure (surge pressure) is generated in the circuit at the time of start-up, both hydraulic motors do not switch to the low speed side, so that traveling can be stabilized.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention, FIG. 2 is a hydraulic circuit explanatory diagram when self-holding in a low speed running state, and FIGS. 3 and 4 are hydraulic circuit diagrams of a conventional device, respectively. . 6,6 ′ …… Hydraulic motor, 8,8 ′ …… Suction amount control means, 11,1
1 ', 12,12' ... Supply / discharge path, 17 ... Automatic switching valve, 20 ... Switching valve, 22 ... Shuttle valve, 23 ... Surge pressure absorption valve, 33
...... passage, 34 ...... self-holding circuit.

Claims (2)

[Claims] 1. A variable displacement dual hydraulic motor (6),
Inhalation amount control means (8) disposed in each of (6 '),
A hydraulic motor for vehicle running in which a pilot pressure is supplied to and discharged from a pilot port of (8 ') by a switching valve (20) to rotate both hydraulic motors (6) and (6') at low speed or high speed. In the speed switching device of, both hydraulic motors (6),
The shuttle valve (22) for selecting and extracting the high-pressure side pressure from the supply / discharge passage of (6 '), the switching valve (20), and the pilot ports of the both intake amount control means (8), (8') When the high pressure side pressure from the shuttle valve (22) is equal to or higher than a predetermined pressure, the pilot ports of the both suction amount control means (8) and (8 ') which are interposed between the tanks are connected to a predetermined pressure. If the automatic switching valve (17) is connected to the switching valve (20) when it does not reach, and the high-side pressure from the shuttle valve (22) after the automatic switching valve (17) has switched over a predetermined pressure is higher than the predetermined pressure. When the pressure is lower than the specified pressure, both suction amount control means (8),
(8 ') A self-holding circuit (34) for holding the connection state between the pilot port and the tank, wherein a speed changing device for a hydraulic motor for vehicle traveling is provided. 2. A surge pressure absorption valve (23) in a passage (33) connecting the shuttle valve (22) and the pressure oil inlet of the automatic switching valve (17).
The speed switching device for a hydraulic motor for vehicle traveling according to claim 1, further comprising: