JPH075281Y2 - Hydraulic motor capacity controller - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention uses a hydraulic motor used for general machinery, construction machinery, etc. as a 2nd speed motor by controlling switching to the 2nd speed, and if necessary, increases the capacity. The present invention relates to a displacement control device for a hydraulic motor that is fixed and can be used even with a fixed motor.

[Conventional technology]

Normally, as the hydraulic motor used for the construction machine or the like, a fixed motor having a fixed motor capacity according to the design specifications of the construction machine is selected. However, depending on the actual operating conditions, there are times when it is desired to obtain high torque because it may be low speed, and conversely, where it is desirable to obtain high speed because low torque may be used. In such a case, there is a problem that the function is limited in the case of the fixed motor.

Therefore, in order to effectively exert the function of the hydraulic motor within the limited output horsepower range, the hydraulic motor may be switched to the second speed and used.

For example, considering a traveling motor for a construction machine, in the case of frequent flatland traveling, there is a demand for high-speed traveling although the torque may be low. In this case, the hydraulic motor must have a small capacity to rotate at high speed. Correspond. On the other hand, when climbing a slope or loading cargo, there is a demand that the traveling speed be slow but a large torque is required. In this case, the hydraulic motor may be switched to a large capacity to cope with the demand.

Conventionally, as such a displacement control device for a hydraulic motor, those shown in FIGS. 6 and 7 are known.

First, in FIG. 6, reference numeral 1 denotes a variable displacement type hydraulic motor. For the hydraulic motor 1, for example, a swash shaft type, a swash plate type or a radial piston type hydraulic motor is used. The motor capacity can be changed by displacing the portion 1A. 2A and 2B are hydraulic pipes for supplying pressure oil to the hydraulic motor 1, and the hydraulic pipes 2A and 2B are connected to a hydraulic source (neither is shown) via a brake device and a direction switching valve. Reference numeral 3 is a high-pressure selection valve that selects the high-pressure side of the hydraulic pipes 2A and 2B, and the drive pressure derived by the high-pressure selection valve 3 is input to a capacity control device 4 described later.

Reference numeral 4 denotes a displacement control device attached to the hydraulic motor 1. The displacement control device 4 has a casing 4A and one end side slidably provided in the casing 4 and the other end side protruding outside the casing 4A. It is composed of a control piston 4B connected to the variable volume portion 1A, and a large oil chamber 4C and a small oil chamber 4D defined in the casing 1A by the control piston 4B.

Reference numeral 5 is a pressure introducing pipe that connects between the high pressure selection valve 3 and the capacity control device 4, and 6 is a control valve which is provided in the middle of the pressure introducing pipe 5 and includes a 4-port 2-position switching valve. 6
Drive pressure to the small oil chamber
Driven by introducing to 4D and connecting the large oil chamber 4C to the tank 7 and setting the control piston 4B in the reduction direction shown in the drawing to switch the motor capacity to a small capacity and the control valve 6 to the switching position (b). The pressure is introduced into the large oil chamber 4C, and the small oil chamber 4D is connected to the tank 7 so that the control piston 4B is extended and the motor capacity is increased.

The displacement control device for the hydraulic motor configured as described above switches the control valve 6 based on the hydraulic pressure command output from the command control valve (not shown) on the cab side, and controls the control piston 4B of the displacement control device 4. By expanding and contracting, the capacity of the hydraulic motor 1 can be switched in two stages, and the characteristics shown in FIG. 7 are obtained.

[Problems to be solved by the device]

However, according to the above-mentioned conventional technique, the control valve 6 is switched by the command control valve on the cab side.
There is a problem that it is not possible to automatically switch to the 2nd speed according to the level of the driving pressure of.

Further, it is necessary to integrally incorporate the capacity control device 4 and the control valve 6 in addition to the capacity varying section 1A on the hydraulic motor 1 side, which causes a problem that the number of parts increases and the size becomes large. In particular, when the hydraulic motor 1 is a traveling motor for a track-type construction machine, the traveling motor protrudes in the width direction from between the shoes of the crawler track as a result of an increase in shape and size, and a so-called "in-shoe" occurs. There is a problem that it cannot be achieved.

The present invention has been made in view of the above problems of the prior art, and can automatically switch the hydraulic motor to the second speed by the motor driving pressure itself, and further, as necessary, fix the hydraulic motor to a large capacity or a small capacity as a fixed motor. Another object of the present invention is to provide a displacement control device for a hydraulic motor that can be used as a fixed motor and that can be used as a fixed motor without a control valve or the like.

[Means for Solving the Problems]

In order to solve the above problems, the present invention defines a casing having a cylinder inside, and one end side slidably provided in the cylinder of the casing to define the inside into a large oil chamber and a small oil chamber. , A control piston, the other end of which protrudes out of the casing and is connected to a variable capacity portion of a hydraulic motor, and a slidable cylinder provided in the spool cylinder formed in the control piston. A spool in which a spool annular chamber that is in constant communication with the oil chamber is formed at an intermediate position in the axial direction, a spring chamber that is located inside one of the two end sides of the spool and that is defined in the spool cylinder, and the other A spool end chamber defined on the shaft end side and defined in the spool cylinder, and provided in the spring chamber,
A spring for constantly urging the spool toward the spool end chamber, and a bottomed command piston cylinder formed in the spool so as to open into the spool end chamber;
A piston is provided slidably in the command piston cylinder so as to define a working chamber on the bottom side of the command piston cylinder that is in constant communication with the spool annular chamber, and the piston is spring-loaded in accordance with the pressure in the working chamber. And a pressure introducing port for introducing the driving pressure of the hydraulic motor into the small oil chamber, the spool annular chamber and the working chamber, and the control piston, which is normally formed by the spool. When the large oil chamber communicates with the spring chamber and the spool is slidably displaced toward the spring chamber against the spring,
A switching port for communicating the large oil chamber with the spool annular chamber, a communication port for communicating the spring chamber with the outside of the casing or the control piston, and another communication port for communicating the spool end chamber with the casing or the outside of the control piston. Among the connecting ports, one connecting port is configured to be selectively switched and connected to an external hydraulic power source and a drain by a switching valve, and the other connecting port is always connected to the drain. ing.

[Action]

With the above configuration, when the switching valve and the drain side are switched and connected, the spring chamber and the spool end chamber both communicate with the drain. In this case, the displacement of the hydraulic motor is automatically adjusted according to the driving pressure. It becomes possible to switch.

That is, when the driving pressure of the hydraulic motor introduced from the pressure introduction port into the working chamber through the small oil chamber and the spool annular chamber is low, the spool is urged by the spring in the spring chamber toward the spool end chamber side, and the switching is performed. Since the large oil chamber communicates with the spring chamber via the port, the large oil chamber is in the tank pressure state, and the control piston slides and displaces into the casing due to the pressure in the small oil chamber, which causes the displacement of the hydraulic motor. The variable portion can be driven to the small capacity (large capacity) side. Further, when the driving pressure becomes high, the pressure in the working chamber also rises, and the command piston slides the spool against the spring according to the pressure in the working chamber. Through the annular ring chamber, the driving pressure of the hydraulic motor is introduced into the large oil chamber, and the control piston is slidably displaced by the pressure in the large oil chamber so as to extend from the casing. The variable capacity part can be driven to the large capacity (small capacity) side.

On the other hand, when the switching valve is switched and connected to the hydraulic pressure source side,
One of the spring chamber and the spool end chamber is supplied with pressure oil from the hydraulic pressure source through one communication port, and the other chamber is connected with the drain through the other communication port. Regardless of the drive pressure of the hydraulic motor, the spool is held at a fixed position in the spool cylinder of the control piston, and the control piston is also fixed at a fixed position, so that the displacement part of the hydraulic motor has a large capacity. (Small capacity) Can be fixed in a fixed position.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5. The same components as those of the conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

1 and 2 show a first embodiment of the present invention.

In the figure, 11 is a casing of the present embodiment, the casing 11 has a casing body 12 having one end opened and the other end serving as a bottom, and a lid body 13 closing the one end side opening of the casing body 12. A cylinder 14 is formed in the casing body 12 in the axial direction, and a rod insertion hole 15 is formed in the bottom.

Reference numeral 16 is a control piston, and the control piston 16 has a piston portion 16A having one end side slidably inserted in the cylinder 14 and a rod portion 16B having the other end side protruding outside the casing body 12 through a rod insertion hole 15. Is integrally formed from the piston part 1
6A divides the inside of the cylinder 14 into a large oil chamber A on the lid 13 side and a small oil chamber B on the bottom side, and the rod portion 16B defines the hydraulic motor 1
Is connected to the variable capacity unit 1A. The control piston 16 has an opening 17A at one end and a bottom 1 at the other end.
A spool cylinder 17 closed by 7B is formed in the axial direction, and the one end side opening 17A is closed by a plug 18.

Reference numeral 19 denotes a spool slidably provided in the spool cylinder 17, and the spool 19 has two lands in the axial direction.
19A and 19B are formed separately, and one land 19A and plug
18, a spring chamber C is defined, a spool annular chamber D is defined between the lands 19A and 19B, and a spool end chamber E is provided between the other land 19B and the bottom portion 17B of the spool cylinder 17.
Are formed. Reference numeral 20 is a compression spring provided in the spring chamber C. The compression spring 20 is a land 19 of the plug 18 and the spool 19.
It is stretched between A and A, and always urges the spool 19 to the left side indicated by the arrow X and holds it in the state shown.

Reference numeral 21 denotes a command piston cylinder that is located at the other end of the spool 19 and has an end face opening formed in the axial direction.
A command piston 22 is slidably provided on the 21 and abuts on a bottom portion 17B of the spool cylinder 17. The command piston 22 defines a working chamber F on the bottom (rear side) side of the command piston cylinder 21, and the working chamber F is always in communication with the spool annular chamber D via the oil hole 23. here,
As for the spool 19, even if a driving pressure is introduced into the spool annular chamber D as described later, the spool 19 is hydraulically balanced, and the driving pressure acts on the working chamber F through the oil hole 23. Then, the reaction force of the hydraulic pressure acting on the command piston 22 acts on the spool 19 and presses the spool 19 to the right side indicated by the arrow Y against the compression spring 20.

Further, 24 is a pressure introducing port formed near the bottom of the casing body 12, and the pressure introducing port 24 is the pressure introducing pipe 5.
Is connected to the high pressure selection valve 3 via. Reference numeral 25 is a communication port bored on the base end side of the rod portion 16B of the control piston 16, and the communication port 25 constantly communicates between the small oil chamber B and the spool annular chamber D, so that the driving pressure is kept constant. Leads to D and working chamber F.

On the other hand, 26 is a switching port formed in the piston portion 16A of the control piston 16, and the switching port 26 communicates with the large oil chamber A via a communication passage 27 formed in the axial direction of the piston portion 16A. Here, the driving pressure is low and the spool 19
In the state where the switching port 26 is displaced in the X direction indicated by the arrow, the switching port 26 is opened in the spring chamber C to communicate with the large oil chamber A, and the land 19A of the spool 19 allows the switching port 26 to communicate with the spool annular chamber D. The period is cut off. Further, when the drive pressure increases and the spool 19 is displaced in the Y direction shown by the arrow, the switching port 26 opens in the spool annular chamber D to communicate with the large oil chamber A, and the land 19A of the spool 19 is formed. The spring chamber C is shut off by the.

Next, 28 is a circumferential groove formed on the outer periphery of the piston portion 16A of the control piston 16 located on the lid 13 side of the switching port 26, and 29
Is a communication port formed in the piston portion 16A so as to communicate the spring chamber C with the circumferential groove 28, and 30 is a communication port formed in the casing body 12 so as to communicate the circumferential groove 28 with the tank 7. In this embodiment, the communication port 30 is always connected to the tank 7, and the spring chamber C is irrespective of the displacement state of the control piston 16.
Is always connected to the tank 7.

On the other hand, 31 is a peripheral groove formed on the inner peripheral surface of the rod insertion hole 15 of the casing body 12, 32 is a communication hole formed in the rod portion 16B of the control piston 16 so as to communicate the spool end chamber E with the peripheral groove 31. Ports, 33 connect the circumferential groove 31 to a switching valve 34 described later,
Shows another communication port drilled in the casing body 12,
The internal pressure of the spool end chamber E is controlled by the switching valve 34 via the communication port 33.

Further, 34 is a 3-port 2-position switching valve provided in, for example, an operator's cab, the inflow side of the switching valve 34 is connected to the external hydraulic power source 35 and the tank 7, and the outflow side is a communication port via a pipe 36.
Connected with 33. By setting the switching valve 34 to the switching position (C), the spool end chamber E and the tank 7 are communicated with each other, and by setting the switching position (D), the spool end chamber E and the hydraulic power source 35 are communicated with each other.

The present embodiment is configured in this way, and its operation will be described next.

First, the operation when the hydraulic motor 1 is automatically switched between a large capacity and a small capacity by using the drive pressure of the hydraulic motor 1 and is driven as a second speed motor will be described.

For this purpose, the switching valve 34 is set to the switching position (C), the spool end chamber E is brought to the same pressure state as the tank 7, and is balanced with the spring chamber C side. In addition, FIG. 1 shows the state of automatic switching,
Moreover, the drive pressure of the hydraulic motor 1 is low, and therefore the motor capacity is in a small capacity state.

Among the pressure oil supplied to drive the hydraulic motor 1 to rotate, the drive pressure introduced from the high pressure selection valve 3 to the pressure introduction port 24 via the pressure introduction pipe 5 is the small oil chamber B and the communication port 25. While being guided to the spool annular chamber D via
It is also led to the working chamber F from the oil hole 23. Then, the control piston 16 is pressed rightward in the drawing by the pressure oil acting on the small oil chamber B, and the spool 19 is also pressed rightward in the drawing by the pressure oil acting on the working chamber F. .

Now, when the driving pressure is low, the oil pressure acting on the spool 19 in the working chamber F is also small, so that the spool 19 is held in the illustrated state by the spring force of the compression spring 20, and the switching port 26 has a large oil pressure. The chamber A and the spring chamber C communicate with each other, and they are in a drain pressure state. Therefore, the control piston 16 is displaced in the Y direction indicated by the arrow due to the driving pressure introduced into the small oil chamber B, and the motor displacement is small.

Next, when the driving pressure rises, the pressure in the working chamber F also rises, so that the oil pressure acting on the spool 19 (= the sectional area of the command piston 22 × the pressure) becomes larger than the set load of the compression spring 20. , The spool 16 starts moving in the Y direction shown by the arrow. When the pressure further rises, the spool 19 also moves accordingly, and the switching port 26 blocks communication with the spring chamber C by the land 19A of the spool 19 and at the same time communicates with the spool annular chamber D. Therefore, the pressure oil in the spool annular chamber D is guided to the large oil chamber A via the switching port 26 and the communication passage 27, and makes the large oil chamber A have the same pressure as the small oil chamber B. As a result, the control piston 16 is acted on by the oil pressure due to the difference in pressure receiving area between the large oil chamber A and the small oil chamber B, and the control piston 16 is displaced in the X direction indicated by the arrow, and the hydraulic motor 1 is moved to a large level. Switch to capacity. Thus, as shown by the solid line in FIG. 2, the motor capacity can be automatically switched according to the driving pressure, and the motor can be used as a second speed motor.

On the other hand, the hydraulic motor 1 must be fixed at a low speed when climbing on the lifting plate while performing fine operation, such as when the construction machine is placed on a transport trailer.

Therefore, the operation when the hydraulic motor 1 is fixed to a large capacity at a low speed and used as a fixed motor will be described.

In this case, the switching valve 34 is switched to the switching position (d), and the pressure oil from the external hydraulic power source 35 is supplied to the pipe 36, the communication port 33, and the circumferential groove 3.
1. Introduced into the spool end chamber E via the communication port 32. As a result, the oil pressure from the external hydraulic power source 35 is constantly applied to the end surface of the spool 19 on the other end side, and the spool 19 is set to the spring 20.
The spring force is overcome to move in the Y direction shown by the arrow, and this state is maintained.

Therefore, the switching port 26 keeps the spool annular chamber D and the large oil chamber A always in communication with each other, and the driving pressure is introduced into the large oil chamber A regardless of the magnitude of the driving pressure of the hydraulic motor 1. Then, the control piston 16 extends in the X direction shown by the arrow, and sets the displacement variable portion 1A of the hydraulic motor 1 to a large displacement. Thus, as shown by the dotted line in FIG. 2, the motor capacity can be fixed to a large capacity, and low speed and large torque can be obtained.

Next, FIG. 3 shows a second embodiment of the present invention. The same components as those of the first embodiment are designated by the same reference numerals.

However, the feature of this embodiment resides in that the switching valve 34 is connected to the communication port 30 via the pipe 41 and the other communication port 33 is connected to the tank 7.

Although the present embodiment is configured in this way, when the switching valve 34 is set to the switching position (c), the spring chamber C communicates with the tank 7, and both the spring chamber C and the spool end chamber E are connected to the tank pressure. Therefore, the same operation as the operation at the time of automatic switching in the first embodiment is exhibited.

On the other hand, when the switching valve 34 is set to the switching position (d), the external hydraulic power source
The pressure oil from 35 is introduced into the spring chamber C via the communication port 30. As a result, the spool 19 is indicated by the arrow X by the hydraulic pressure difference acting on the spring chamber C and the spool annular chamber D and the spring force of the spring 20.
Pressure oil in the spring chamber C is constantly displaced in the direction
Is introduced into the large oil chamber A. Therefore, by setting the pressure of the external hydraulic power source 35 to a predetermined pressure or higher, the control piston 16
Can be held in an extended state at all times, and the hydraulic motor 1 can be fixed to a large capacity and used as a fixed motor.

Further, FIG. 4 shows a third embodiment of the present invention, and the same components as those of the first and second embodiments are designated by the same reference numerals.

Therefore, the feature of this embodiment is that the circumferential groove 31 in the above embodiment,
Communication port 32 and communication port 33 are abolished and control piston 16
Another connecting port 51 that extends in the axial direction and opens to the protruding end side is formed in the rod portion 16B of the above, the external hydraulic power source 35 is abolished, and the switching valve 34 of the switching valve 34 is connected via the pipe 52 connected to the pressure introducing pipe 5. The configuration is such that it is connected to the inflow side and the drive pressure obtained from the high pressure selection valve 3 is used as a hydraulic pressure source.

Although this embodiment is constructed in this way, the operation is the same as that of the second embodiment. However, in this embodiment, the motor drive pressure can be introduced as self-pressure, which simplifies the configuration.

Further, FIG. 5 shows a fourth embodiment of the present invention. The same components as those in the second embodiment described above are designated by the same reference numerals and the description thereof will be omitted.

Therefore, in the figure, 61 is the spool of this embodiment.
Is formed with two lands 61A and 61B spaced apart from one side in the axial direction to the other side, and a spool end chamber G is defined between the one land 61A and the plug 18, and between the lands 61A and 61B. A spool annular chamber H is defined therein, and a spring chamber J is formed between the other land 61B and the bottom portion 17B of the spool cylinder 17.

Reference numeral 62 denotes a command piston cylinder which is located at one end side of the spool 61 and has an end face opening formed in the axial direction.
A command piston 63 is slidably provided on 62 and is in contact with the end surface of the plug 18. And the command piston 63
Defines a working chamber K on the bottom (back) side of the command piston cylinder 62, and the working chamber K is always in communication with the spool annular chamber H via an oil hole 64. Here, regarding the spool 61, even if a drive pressure is introduced into the spool annular chamber H as described later, the spool 61 is hydraulically balanced and is driven into the working chamber K via the oil hole 64. When pressure is applied, the reaction force of the hydraulic pressure that acts on the command piston 63 is spooled.
It acts on 61 and presses the spool 61 to the left side indicated by the arrow X against a compression spring 65 described later.

On the other hand, 65 is a compression spring provided in the spring chamber J, and the compression spring 65 includes a bottom 17B of the cylinder 17 and a land 61B of the spool 61.
And is always tensioned to the right side indicated by the arrow Y to hold the spool 61 in the illustrated state.

Further, 66 is a communication port formed in the control piston 16 in a tilted state in place of the communication port 25 of each of the above-described embodiments, and the communication port 66 constantly connects between the small oil chamber B and the spool annular chamber H. It communicates and guides the driving pressure to the spool annular chamber H and the working chamber K.

On the other hand, 67 is a switching port formed in the piston portion 16A of the control piston 16, and the switching port 67 communicates with the large oil chamber A via a communication passage 68 formed in the axial direction of the piston portion 16A. Here, the driving pressure is low and the spool 61 is compressed by the compression spring 65.
In the state where the switching port 67 is displaced in the Y direction by the arrow, the switching port 67 opens in the spring chamber J to communicate with the large oil chamber A, and the land 61B of the spool 61 allows the switching port 67 to communicate with the spool annular chamber H. The period is cut off. Further, when the driving pressure increases and the spool 61 is displaced in the X direction shown by the arrow, the switching port 67 is opened in the spool annular chamber H to communicate with the large oil chamber A, and the land 61B of the spool 61. The spring chamber J is shut off by the spring.

Next, 69 is a circumferential groove formed on the outer periphery of the piston portion 16A of the control piston 16 located on the lid 13 side of the switching port 67, and 70
Is a communication port bored in the piston portion 16A so as to communicate the spool end chamber G with the circumferential groove 69. The communication port 70, the circumferential groove 69, and the one communication port 30 are provided in the spool end chamber G. The pressure is controlled by the switching valve 34.

Further, 71 is another communication port formed in the rod portion 16B of the control piston 16 so as to communicate the spring chamber J with the circumferential groove 31 of the casing body 12. The communication port 71, the circumferential groove 31, and the communication port 33.
The spring chamber J is always in communication with the tank 7 via the valve regardless of the displacement state of the control piston 16.

The present embodiment is configured as described above, and its operation will be described next.

First, the operation when the hydraulic motor 1 is automatically switched between a large capacity and a small capacity by using the drive pressure of the hydraulic motor 1 and is driven as a second speed motor will be described.

For this purpose, the switching valve 34 is set to the switching position (C), the spool end chamber G is brought to the same pressure as the tank 7, and is balanced with the spring chamber J side. In addition, FIG. 5 shows the state of automatic switching,
Moreover, the drive pressure of the hydraulic motor 1 is low, and therefore the motor capacity is in a small capacity state.

Of the pressure oil supplied to drive the hydraulic motor 1 to rotate, the drive pressure introduced from the high pressure selection valve 3 to the pressure introduction port 24 via the pressure introduction pipe 5 is the small oil chamber B and the communication port 66. Is guided to the spool annular chamber H via
It is also led to the working chamber K from the oil hole 64. Then, the control piston 16 is pressed rightward in the drawing by the pressure oil acting on the small oil chamber B, and the spool force is exerted by the compression spring 65.
61 is also pressed to the right in the figure.

Now, when the driving pressure is low, the oil pressure acting on the spool 61 in the working chamber K is also small, so that the spool 61 is held in the illustrated state by the spring force of the compression spring 65, and the switching port 67 is filled with large oil. The chamber A and the spring chamber J communicate with each other, and they are in a drain pressure state. Therefore, the control piston 16 is displaced in the Y direction indicated by the arrow due to the driving pressure introduced into the small oil chamber B, and the motor displacement is small.

Next, when the driving pressure rises, the pressure in the working chamber K also rises, so that the oil pressure acting on the spool 61 (= the cross-sectional area of the command piston 63 × the pressure) becomes larger than the set load of the compression spring 65. , The spool 61 starts moving in the X direction shown by the arrow. When the pressure further rises, the spool 61 moves accordingly, and the switching port 67 blocks communication with the spring chamber J by the land 61B of the spool 61, and at the same time, communicates with the spool annular chamber H. Therefore, the pressure oil in the spool annular chamber H is guided to the large oil chamber A through the switching port 67 and the communication passage 68, and makes the large oil chamber A have the same pressure as the small oil chamber B. As a result, the control piston 16 is acted on by the oil pressure due to the difference in pressure receiving area between the large oil chamber A and the small oil chamber B, and the control piston 16 is displaced in the X direction indicated by the arrow, and the hydraulic motor 1 is moved to a large level. Switch to capacity. Thus, as shown by the solid line in FIG. 2, the motor capacity can be automatically switched according to the driving pressure, and the motor can be used as a second speed motor.

On the other hand, the hydraulic motor 1 must be fixed at a low speed when climbing on the lifting plate while performing fine operation, such as when the construction machine is placed on a transport trailer.

Therefore, the operation when the hydraulic motor 1 is fixed to a large capacity at a low speed and used as a fixed motor will be described.

In this case, the switching valve 34 is switched to the switching position (d), and the pressure oil from the external hydraulic power source 35 is supplied to the pipe 41, the communication port 30, and the circumferential groove 6.
9, introduced into the spool end chamber G through the communication port 70. As a result, the hydraulic pressure from the external hydraulic power source 35 is constantly applied to the end surface of the spool 61 on one end side, and the spool 61 is rotated by the spring 65.
The spring force is overcome to move in the X direction shown by the arrow, and this state is maintained.

Therefore, the switching port 67 always keeps the spool annular chamber H and the large oil chamber A in communication with each other, and the driving pressure is introduced into the large oil chamber A regardless of the driving pressure of the hydraulic motor 1. Then, the control piston 16 extends in the X direction shown by the arrow, and sets the displacement variable portion 1A of the hydraulic motor 1 to a large displacement. Thus, as shown by the dotted line in FIG. 2, the motor capacity can be fixed to a large capacity, and low speed and large torque can be obtained.

Although this embodiment is as described above, as in the first embodiment, one communication port 30 may be connected to the tank 7, and the switching valve 34 may be connected to another communication port 33 via a pipe. Good. With this configuration, when the switching valve 34 is set to the switching position (c), the spring chamber J communicates with the tank 7, and both the spring chamber J and the spool end chamber G become tank pressure, so that the first The same operation as the operation at the time of automatic switching in the above embodiment is exhibited.

On the other hand, when the switching valve 34 is set to the switching position (d), the external hydraulic power source
The pressure oil from 35 is introduced into the spring chamber J via the communication port 33, and the pressure oil in the spring chamber J is introduced into the large oil chamber A from the switching port 67. Therefore, by setting the pressure of the external hydraulic power source 35 to be equal to or higher than the predetermined pressure, the control piston 16 can be constantly maintained in the extended state, and the hydraulic motor 1 can be fixed to a large capacity and used as a fixed motor.

By the way, in each of the above-described embodiments, the spools 19 and 61 in the spool cylinder 17 are allowed to operate smoothly in response to changes in the driving pressure, and the cylinders 17 and the lands 19A of the spools 19 and 61 are provided. It is necessary to prevent the leakage loss of the pressure oil introduced into the spool annular chambers D and H by setting the gap between the spools 61A, 19B and 61B smaller. To this end, in addition to improving the machining accuracy of the outer peripheral surface of each land 19A, 61A, 19B, 61B of the spool 19, 61, the machining accuracy of the inner surface of the cylinder 17, that is, surface roughness, roundness, straightness, It is necessary to improve dimensional tolerances. However, it is extremely difficult to accurately machine a bottomed hole having a small hole diameter and a deep depth like the spool cylinder 17 shown in the embodiment over the entire length, especially in the inner part of the cylinder 17 on the bottom part 17B side. Since it is difficult to maintain machining accuracy as much as 1 spool 1
The slidability of 9,61 and the prevention of pressure oil leakage may be impaired.

Therefore, in this embodiment, the opening 17A side of the inner surface of the spool cylinder 17 capable of high processing accuracy is set as the sliding portion of the spool 61, and the lands 61A and 61B of the spool 61 are connected to the opening 17A side of the cylinder 17. The bottom 17B of the cylinder 17 on the side of the bottom 17B serves as a spring chamber J. Therefore, it suffices to perform high-precision machining only on the opening 17A side of the inner surface of the cylinder 17, and it is possible to further improve the machining accuracy and the efficiency of the machining work,
It is possible to improve slidability of the spool 61 and prevent leakage loss of pressure oil.

In each embodiment, the spring chamber C, (J) is connected to the communication port 29,
Although it has been described that the casing body 12 is opened through the (71), the circumferential grooves 28, (31) and the communication ports 30, (33), the rod is provided through the communication port formed in the axial direction of the control piston 16. You may open directly to the other end side protrusion part of the part 16B. Further, the third embodiment may be applied to the first embodiment and self-pressure may be used. Furthermore, depending on the expansion and contraction of the control piston 16,
Of course, the capacity of the hydraulic motor 1 may be reversed.

[Effect of device]

The hydraulic motor displacement control device according to the present invention is as described above in detail, and has the effects of the following items.

Since the control piston can be slidably displaced between the large displacement side and the small displacement side according to the high and low driving pressures of the hydraulic motor to control the motor displacement of the hydraulic motor, the displacement of the displacement can be controlled by the driving pressure of the hydraulic motor itself. Automatic control is possible.

Since the capacity can be fixed to a large capacity or a small capacity only by switching the valve of the switching valve, it can be used as a second speed motor or a fixed motor depending on the usage conditions of the hydraulic motor, and it is possible to achieve multiple functions. .

A single displacement control device may be attached to the hydraulic motor, which eliminates the need for a control valve as in the prior art and allows a compact and compact structure. Therefore, when used as a traveling motor, the entire casing of the hydraulic motor can be accommodated within the shoe width of the crawler belt.

[Brief description of drawings]

1 and 2 show a first embodiment, FIG. 1 is a longitudinal sectional view showing a motor displacement control device according to this embodiment, and FIG. 2 is a diagram showing the relationship between drive pressure and motor displacement. 3 is a vertical sectional view similar to FIG. 1 showing a second embodiment, FIG. 4 is a vertical sectional view similar to FIG. 1 showing a third embodiment, and FIG. FIG. 6 is a longitudinal sectional view similar to FIG. 1 showing an embodiment, FIGS. 6 and 7 relate to a conventional technique, and FIG. 6 is a circuit configuration diagram showing a hydraulic motor displacement control device according to the conventional technique, and FIG. It is a diagram which shows the relationship between drive pressure and motor capacity. 1 ... hydraulic motor, 1A ... variable capacity part, 2A, 2B ... hydraulic piping,
3 ... High pressure selection valve, 11 ... Casing, 12 ... Casing body, 13 ... Lid, 14 ... Cylinder, 16 ... Control piston, 17 ...
Cylinder for spool, 19,61 ... Spool, 20,65 ... Compression spring, 21,62 ... Cylinder for command piston, 22,63 ... Command piston, 23,64 ... Oil hole, 24 ... Pressure introducing port, 25,29, 32,6
6, 70, 71 ... Communication port, 26, 67 ... Switching port, 27, 68 ... Communication passage, 28, 31, 69 ... Circumferential groove, 30, 33 ... Communication port, 34 ... Switching valve, 35 ... External hydraulic power source, A ... Large oil chamber, B ... Small oil chamber, C, J ...
Spring chamber, D, H ... spool annular chamber, E, G ... spool end chamber,
F, K ... Working room.

Claims (1)

[Scope of utility model registration request] 1. A casing whose inside is a cylinder, and one end side of which is slidably provided in the cylinder of the casing,
A control piston that defines the inside into a large oil chamber and a small oil chamber, and has the other end protruding outside the casing and connected to the variable capacity portion of the hydraulic motor; and a spool cylinder formed in the control piston. A spool in which a spool annular chamber that is slidably provided and is always in communication with the small oil chamber in the spool cylinder is formed at an intermediate position in the axial direction, and is located on one of the two end sides of the spool. A spring chamber defined within the spool cylinder and a spool end chamber located on the other shaft end side and defined within the spool cylinder; and a spool end chamber provided in the spring chamber. Side, a bottomed command piston cylinder formed on the spool so as to open into the spool end chamber, and the bottom side of the command piston cylinder with the spring. And a command to displace the spool in a sliding manner against the spring according to the pressure in the working chamber so as to define a working chamber that is in constant communication with the circular chamber. A piston, a pressure introducing port for introducing the driving pressure of the hydraulic motor into the small oil chamber, and the control piston are formed, and the spool is normally in communication with the large oil chamber by the spool so that the spool resists the spring. And a sliding port to the spring chamber side, a switching port for communicating the large oil chamber with the spool annular chamber,
A communication port for connecting the spring chamber to the outside of the casing or the control piston, and another communication port for connecting the spool end chamber to the outside of the casing or the control piston, one of the communication ports being a switching port A hydraulic motor displacement control device configured to selectively switch connection between a hydraulic power source and a drain by means of a valve, and the other communication port always connected to the drain.