JPH0732222Y2 - Vehicle drive hydraulic circuit - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for driving and driving a vehicle such as a crawler vehicle.

[0002]

2. Description of the Related Art Conventionally, a vehicle such as a crawler vehicle is driven to run.
The hydraulic circuit to be used is, for example, JP-A-56-96181.
Those described in the report are known. This one too
Can be switched to two different suction volume positions.
2nd-speed hydraulic pressure with a swash plate
A motor, a control valve, the hydraulic motor and co
A pair of oil passages connecting the control valve and the
If the hydraulic pressure is high, pull the swash plate and
And a tilting cylinder for switching to
Between the cylinder and the pair of oil passages,
Connected first port and drain connected to the drain path
Connected to the port and the high pressure side oil passage of the pair of oil passages
The second port and the movement of the first port, the drain port
Communication between the two ports or the first port and the second port
The spool to be passed through and the spool are the same for the first and second ports.
The high pressure oil and the spring that pushes in the direction of communication
The spool against the spring, the first port, drain
Port to move the communication ports
And a pilot switching valve having
High pressure oil that is the pump discharge pressure when switched to open
Is equipped with an electromagnetic switching valve that guides the
It

[0003]

[Problems to be solved by the device] However, this
For such a thing, tilt the swash plate of the 2nd speed motor to 2 positions.
Therefore, an electromagnetic switching valve is required, and this electromagnetic switching valve
There is a problem that a person must switch between the two.

An object of the present invention is to provide a traveling drive hydraulic circuit for a vehicle capable of achieving automatic second speed with a simple structure.

[0005]

SUMMARY OF THE INVENTION Such an object is to provide a second speed hydraulic motor having a suction amount control member capable of switching between two different suction amount positions and for applying a traveling driving force to a vehicle. A switching valve, a pair of main supply / discharge passages connecting the second speed hydraulic motor and the switching valve, and when the introduced hydraulic pressure is high, the suction amount control member is pressed to move one of the suction amount positions. In the traveling drive hydraulic circuit of the vehicle including a piston for switching to, between the piston and the pair of main supply / discharge paths,
The first port connected to the piston, the drain port connected to the drain path, the second port connected to the main supply / discharge path on the high-pressure side of the pair of main supply / discharge paths, and the first port due to the movement thereof. A spool for communicating the ports and the drain ports with each other or with the first port and the second port for communicating with each other, a pressing means for pressing the spool in a direction in which the first and second ports communicate with each other, and a high pressure of the main supply / discharge passage. is connected to the side of the main supply drainage path, when the fluid pressure derived from the main supply and discharge path of the high pressure side is not less than a predetermined pressure, the first port against the spool in the pressing means, the drain port each other communicates It can be achieved by interposing a two-position pilot valve having a pilot port that moves so that

[0006]

Now, it is assumed that the hydraulic pressures in the pair of main supply / discharge passages are both less than the predetermined pressure. At this time, since the hydraulic pressure guided to the pilot port is also less than the predetermined pressure, the spool of the two-position pilot valve is moved by the pressing means to the position where the first and second ports communicate with each other. As a result, the hydraulic pressure, which is less than the predetermined pressure but is high pressure, is guided to the piston through the second port and the first port from the high pressure side main supply / discharge path, and the suction amount control member switches to one suction amount position. I am crossing.
Next, when the hydraulic pressure in the main supply / discharge passage on the high-pressure side rises above a predetermined pressure, the hydraulic pressure guided to the pilot port also rises above a predetermined pressure, so the spool moves against the pressing means, and Connect 1 port and drain port to each other. As a result,
The hydraulic pressure guided to the piston is discharged to the drain passage through the first port and the drain port, whereby the hydraulic pressure acting on the piston becomes low and the suction amount control member switches to the other suction amount position. In this way, the suction amount control member of the hydraulic motor is automatically switched to two positions and the hydraulic motor, that is, the vehicle is switched to the second speed. Such automatic second speed is paired with the piston as described above. simply interposed 2 position pilot valve between the main supply and discharge passage, i.e.
This can be achieved without providing an electromagnetic switching valve , and the structure can be simplified.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, Oite to 3, the attachment 1 is a cylindrical portion attached to the running frame 2 of the crawler vehicle, rotatably fitted on the outer side of the cylindrical portion, than the running frame 2 above the revolving frame 80 The swivel joint is a vertical swivel joint that is formed by connecting the traveling frame 2 and the swivel frame 80 to each other, and swivels the swivel frame 80 relative to the traveling frame 2 in a horizontal plane. it can. Further, a cab 81 of the swivel frame 80 is provided with a pump 82 and a manual switching valve 3 connected to a tank (not shown).

On the other hand, the traveling frame 2 has a casing 6 of a hydraulic motor including a spindle 4 and a rear flange 5.
And a crawler vehicle inside the casing 6.
A swash plate type variable displacement type second speed hydraulic motor 7 for applying a traveling driving force is housed therein. The hydraulic motor 7 and the manual switching valve 3 are connected by a pair of main supply / discharge passages 8 and 9 passing through the swivel joint 1. The hydraulic motor
7 is a semi-circular surface with an obtuse angle to the front and intersects at the center.
Has a swash plate 13 as an inhalation amount control member. The swash plate 13 swings about a pin 14 as a fulcrum, and the semicircular surface 11 contacts the spindle 4 at the minimum inhalation amount position A and the semicircle. The maximum suction amount position B shown in FIG. 3 where the surface 12 contacts the spindle 4,
With two different suction amount stably switching switched this <br/> and can the position of the small to be described later, it can also be stopped at an intermediate position by the large-diameter piston 49 and 50. Reference numeral 15 denotes a rotary shaft that penetrates the swash plate 13 and is rotatably supported by the casing 6 via bearings 16 and 17. The rotary shaft 15 has a plurality of pistons.
A cylinder body 19 in which 18 is inserted is attached. High-pressure fluid is supplied to the cylinder body 19 from the main supply / discharge passages 8 and 9 through the timing plate 20, whereby the piston 18 is pressed against the slope 22 of the swash plate 13 through the shoe 21, and the cylinder body 19 is rotated. Rotate with 15. In addition, 23 is a seal. A case rotation type speed reducer 31 is connected to the rotary shaft 15, whereby the rotation of the rotary shaft 15 is decelerated and taken out to a case 32 of the speed reducer 31. The case 32 is rotatably supported by the spindle 4 via a pair of bearings 33 and 34, and a sprocket 36 that meshes with a shoe 35 of a crawler is integrally formed on the outer periphery of the case 32.
In addition, 37 is a seal.

Reference numeral 41 denotes a casing 6 of the hydraulic motor 7, more specifically, a high pressure selection valve having a counter balance function housed in the rear flange 5. The high pressure selection valve 41 is a fluid pressure from pilot passages 42 and 43. And spring 4
It has a switching valve 46 that switches to three positions of I, II, and III by the restoring force of 4, 45, and a pair of check valves 67, 68. A small cylinder chamber 47 and a large cylinder chamber 48 are formed on the inner surface of the spindle 4 facing the semicircular surface 11 and the semicircular surface 12, respectively.
A small-diameter piston 49 and a large-diameter piston 50, which press the semicircular surfaces 11 and 12 and are parallel to the rotary shaft 15, are slidably inserted in the. Since the small diameter piston 49 and the large diameter piston 50 are arranged axially forward of the swash plate 13 in this way, it is possible to prevent the hydraulic motor 7 from increasing in size in the radial direction. In the casing 6, an intermediate passage 51 through which the high-pressure fluid selected and taken out from the high-pressure main supply / discharge passages 8 and 9 by the high- pressure selection valve 41 passes is formed. The intermediate passage 51 and the small cylinder chamber are formed. whereby the pair of high-pressure passage 52 and 53 and 47 and the large cylinder chamber 48
Each is connected. Here, the high pressure passage 53
If the fluid supplied to the binder chamber 48 has a high pressure, the large diameter piston
The ton 50 presses the swash plate 13 to one suction amount position, here
Then, switch to the minimum suction amount position A.

The high pressure selection valve 41 , in other words, the main supply / discharge passages 8 and 9
A two-position pilot valve 54 is provided in a high-pressure passage 53 between the large-diameter piston 50 and the large-diameter piston 50 .
As shown in FIG. 4 , it is housed in the casing 6 of the hydraulic motor 7, more specifically, in the stepped chamber 55 formed in the rear flange 5. This pilot valve 54 has a stepped spool 56,
A high-pressure passage 53 is opened in the large-diameter piston 50 by opening to the stepped chamber 55.
To the first port 85 and via the stepped spool 56
Formed annular groove-shaped second port 61 and stepped spool
An annular groove-shaped drain port 62 formed in 56,
There is. Here, the second port 61 is mainly supplied through the intermediate passage 51.
Connected to the main supply / exhaust passages 8 and 9 on the high-pressure side of the exhaust passages 8 and 9,
On the other hand, the drain port 62 is formed in the stepped spool 56.
The drain passage 60 is connected to the drain passage 59.
Then, the stepped spool 56 moves to move the pilot valve.
When 54 is switched to the IV position, the first port 85 and the second port
When the switch 61 is switched to the V position, the first
The port 85 and the drain port 62 communicate with each other. Where the
The stepped spool 56 has a spring 57 as a pressing means.
Pressed in the direction in which the first and second ports 85 and 61 communicate with each other
Energized. On the other hand, this stepped spool 56 pilot port
86, more specifically on the side of the spring 57 side of the second port 61
Is the main supply / discharge passage 8 through the pilot passage 58 and the intermediate passage 51.
Main supply / discharge paths 8 and 9 on the high voltage side of 9 are connected, and
When the fluid pressure in the main supply / discharge passages 8 and 9 is higher than a specified pressure,
Stepped spool 56 against spring 57 and first port
Move so that 85 and the drain port 62 communicate with each other. And, the second drain port 61, 62 of this stepped spool 56
The land 63 between and the first port 85 are overlapped. As a result, the pilot valve 54 is provided with a neutral point and is provided with hysteresis (differentiating the switching pressure when increasing the pressure and the switching pressure when decreasing the pressure). That is, in this embodiment, when the pressure of the high-pressure fluid taken out by the high-pressure selection valve 41 rises to a predetermined pressure, the switching position of the pilot valve 54 switches to the V position as described above, and the first port 85 and the drain port are switched . 62 communicates with. After such a state, that is, after the pressure of the extracted high-pressure fluid becomes equal to or higher than the predetermined pressure, until the pressure of the high-pressure fluid decreases to a predetermined set pressure that is equal to or lower than the predetermined pressure, Even if the spool 56 moves to the right in FIG. 4 , the land 63 continues to block the first port 85 , so that the small and large diameter pistons 49 and 50 do not move.
That is, the switching position of the pilot valve 54 is small, and the large-diameter pistons 49, 50 are held at positions where they do not move in the direction in which the suction amount of the hydraulic motor 7 decreases. Thus, the pilot valve
Even if the pressure of the high-pressure fluid fluctuates between a predetermined pressure and a predetermined set pressure after the switching position is switched from the IV position to the V position, the 54 is maintained in the same state, so that some load fluctuation may occur. Also, the crawler vehicle can smoothly transition from high-speed running to low-speed running without hunting (switching repeatedly in a short time).

Next, the operation of the embodiment of the present invention will be described. When the crawler vehicle is moving forward on flat ground, the high-pressure fluid discharged from the pump below the predetermined pressure is supplied to the main supply / discharge path 8 by the manual switching valve 3, and the returned low-pressure fluid is supplied to the main supply / discharge path. Flowing through 9. At this time, the switching valve
46 is switched to the position III by the high pressure fluid flowing into the pilot passage 42, whereby the high pressure fluid in the main supply / discharge passage 8 passes through the check valve 67 and becomes the cylinder body of the hydraulic motor 7.
While flowing into the inside 19, it is selected and taken out to the intermediate passage 51. The high-pressure fluid flowing into the intermediate passage 51 acts on the pilot port 86 of the pilot valve 54, but since the acting fluid pressure is less than a predetermined pressure, the spring 57 is attached.
The force overcomes the fluid force and the pilot valve 54 is switched to the IV position, and the first and second ports 85 and 61 communicate with each other.
There is. As a result, the fluid that is under high pressure
Large silin through the second and first ports 61 and 85 and the high pressure passage 53
To the small chamber 48 and through the high pressure passage 52.
Supplied. At this time, the large-diameter piston 50 is the small-diameter piston.
Since the pressure receiving area is wider than the pressure receiving area 49, the large diameter piston 50 projects and the small diameter piston 49 retracts, and the swash plate 13 has a small tilt angle, that is, a minimum stroke volume position A of the motor.
It has switched to (one suction amount position) . Therefore, when a fixed amount of pressure fluid flows into the hydraulic motor 7 per unit time, the rotary shaft 15 of the hydraulic motor 7 rotates with a small torque and a high speed, and the crawler vehicle travels at a high speed with a small running force.

Next, when the crawler vehicle starts uphill,
The load acting on the hydraulic motor 7 increases and the main supply / discharge path 8
The pressure inside rises. Then, when the pressure fluid rises above a predetermined pressure, the stepped spool 56 is passed through the pilot passage 58.
Fluid force acting on the pilot port 86 of the spring 57
Chi surpasses the in resiliency, the first port 85 and the drain port 62
The stepped spool 56 moves so that the
The valve 54 switches to the V position. As a result, the large cylinder chamber 48
A drainage path 59 and the high pressure passage 53, and communicates through drain passage 60, the fluid that has been led to the large-diameter piston 50 is the first port
It is discharged to the drain passage 60 through 85 and the drain port 62.
Therefore, the fluid pressure acting on the large-diameter piston 50 becomes low.
However, since the high-pressure fluid force above the predetermined pressure still acts on the small-diameter piston 49, only the small-diameter piston 49 projects and moves to press the swash plate 13 to increase the tilt angle ,
Switch 13 from the minimum suction volume position A (one suction volume position) to the maximum suction volume position B (other suction volume position).
Change. Then, as the intake amount increases as described above , the pressure in the main supply / discharge passage 8 taken out from the high-pressure selection valve 41 returns to just below the predetermined pressure, so that the fluid pressure acting on the stepped spool 56 is increased through the pilot passage 58. Do small spool 56
Is pushed back in FIG. 4 rightward by a spring 57, the pilot valve 54 is the state shown in FIG. 4, i.e., the first port 85 is in a neutral state that will be closed by the land 63. As a result, the large-diameter piston 50 in the large cylinder chamber 48 is hydraulically locked, and the swash plate 13
Is held by the large-diameter and small-diameter pistons 50 and 49 in the middle of the minimum and maximum suction amount positions A and B. Furthermore, as the climb angle increases, the pilot valve 54, small and large pistons 49, 5
0, the swash plate 13 performs the same operation as described above. In addition, the load acting on the hydraulic motor 7 may decrease when climbing such a slope, and the pressure of the extracted high-pressure fluid may drop below the predetermined pressure. At this time, the land 63 and the first port may be reduced. Since 85 overlaps with each other, the land 63 continues to shut off the first port 85 until the pressure of the high-pressure fluid taken out by the high-pressure selection valve 41 decreases from a predetermined pressure to a predetermined set pressure. The small and large pistons 49, 50 do not move, and therefore the swash plate 13 of the hydraulic motor 7 does not move either. Therefore, in such a pressure range, the traveling speed of the crawler vehicle (the rotation speed of the hydraulic motor 7) does not slow down or speed up. Then, the above-described operation is continuously repeated until the uphill angle reaches a predetermined value, and the swash plate 13 moves to the maximum suction amount position B. Therefore, the hydraulic motor 7 gradually shifts to a large torque low speed rotation,
The crawler vehicle is driven at low speed with a large running force. During such automatic shifting, the fluid pressure acting on the small diameter piston 49 and the stepped spool 56 for controlling the tilt angle of the swash plate 13, that is, the pressure in the main supply / discharge passage 8 becomes substantially constant. Therefore, the crawler can automatically shift smoothly. In this way
The swash plate 13 of the hydraulic motor 7 automatically switches to two positions.
Hydraulic motor 7, that is, the crawler vehicle is switched to the 2nd speed.
However, such an automatic second gear is a large diameter fix as mentioned above.
2-position pilot between the engine 50 and the pair of main supply / discharge paths 8 and 9.
Only by interposing the valve 54, i.e. without providing an electromagnetic switching valve.
Can be achieved easily and the structure can be simple
It

Next, when the vehicle moves from uphill to flatland and the high-pressure fluid taken out from the high-pressure selection valve 41 falls to a predetermined set pressure, the pilot valve 54 switches to the IV position and the intermediate passage 51 and the high-pressure passage 53 are connected. , Small and large diameter pistons
A high-pressure fluid having a predetermined set pressure is introduced into both 49 and 50, and the large-diameter piston 50 projects. As a result, the swash plate 13 of the hydraulic motor 7
Tilts in a direction in which the suction amount of the hydraulic motor 7 decreases. In this way, the crawler vehicle gradually shifts from low speed running to high speed running. FIGS. 6, 7, 8 and 9 are graphs showing the characteristics of the above-described operation of the hydraulic motor 7. In the figure, Pa represents the predetermined pressure.

FIG . 5 shows another embodiment of the present invention. In this embodiment, the pilot valve 71 and a pair of pistons 72, 73 having the same diameter are connected by passages 76, 77 having throttles 74, 75 in the middle. When the high-pressure fluid is below a predetermined pressure, it guides the high-pressure fluid to the piston 73 and holds the swash plate 13 at the minimum suction amount position A. It guides to the piston 72 and moves the swash plate 13 toward the maximum suction amount position B. In this embodiment, a passage for connecting the passages 76 and 77 may be provided, and a throttle may be provided in the middle of the connection passage to prevent hunting.

In the present invention, the pump for supplying fluid to the hydraulic motor is of a variable displacement type so that the output range of the hydraulic motor is widened and the output speed or the output torque can be increased without increasing the pump displacement. Can be increased. The output characteristics of the hydraulic motor in this case is shown in FIG. 10, 11. FIG. 10 shows the characteristics when operating the suction amount varying mechanism of the hydraulic motor in the low speed and high torque region .
1 shows the characteristics when operating the suction amount variable mechanism of the hydraulic motor in the high speed and low torque region. The shaded area in the figure represents the variable output range that is expanded by making the hydraulic motor variable, compared to the combination of the variable pump and the fixed motor. Further, in this invention, one of the swash plates 13 may be pressed by the piston and the other may be biased by the spring to change the tilt angle.

[0016]

As described above, according to the present invention, the automatic second speed can be achieved with a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a partially cutaway side view of a crawler vehicle.

FIG. 3 is a sectional view of the vicinity of a hydraulic motor.

FIG. 4 is a sectional view of the vicinity of a pilot valve.

FIG. 5 is a circuit diagram showing another embodiment of the present invention.

FIG. 6 is a graph showing output characteristics of a hydraulic motor.

FIG. 7 is a graph showing the output characteristic of the hydraulic motor.

FIG. 8 is a graph showing the output characteristic of the hydraulic motor.

FIG. 9 is a graph showing the output characteristic of the hydraulic motor.

FIG. 10 is a graph showing the output characteristics of the hydraulic motor when the pump is a variable displacement type.

FIG. 11 is a graph showing the output characteristic of the hydraulic motor when the pump is a variable displacement type.

[Explanation of Codes] 3 ... Switching valve 7 ... Hydraulic motors 8, 9 ... Main supply / discharge passage 13 ... Suction amount control member (swash plate) 50 ... Piston 54 ... 2-position pilot valve 56 ... Spool 57 ... Pressing means 59 ... Drain path 61 ... Second port 62 ... Drain port 85 ... First port 86 ... Pilot port

Claims (1)

[Scope of utility model registration request] 1. A switch for switching between two different suction amount positions.
It has a suction amount control member 13 that can
The second speed hydraulic motor 7 for applying force, the switching valve 3, and the above 2
A pair of main supply / discharge paths that connect the high-speed hydraulic motor 7 and the switching valve 3.
 8, 9 and suction pressure control when the guided fluid pressure is high
A piston that presses the member 13 to switch to one suction amount position
In the drive hydraulic circuit of the vehicle equipped with
Between the piston 50 and the pair of main supply / discharge passages 8 and 9, the piston
First port connected to Ston 5085And the drain road59Contact
Drain port followed62And a pair of main supply and discharge channels 8 and 9
2nd port connected to main supply / discharge paths 8 and 9 on the high voltage side61
And the move, the first port85, Drain port62One another
Communication or the first port85, Second port61Communicate with each other
Spool 56 that causes it and the spool 56 to have the first and second ports
85, 61The pressing means 57 for pressing in the direction in which they communicate with each other,
Main supply on the high-voltage side of supply / discharge paths 8 and 9.Discharge route Connected to 8, 9
The hydraulic pressure introduced from the main supply / discharge paths 8 and 9 on the high
When the above is reached, push the spool 56 against the pressing means 57.
1st port85, Drain port62Move to communicate with each other
Pilot port86And a two-position pilot with
Drive hydraulic pressure of the vehicle characterized by interposing a valve 54
circuit.