JP5105845B2 - Hydraulic control device - Google Patents

Description

  The present invention relates to a hydraulic control apparatus that includes a link mechanism and performs feedback control based on the operation of an actuator.

A hydraulic control apparatus that performs feedback control based on the operation of an actuator is conventionally known. This type of hydraulic control apparatus will be described with reference to FIGS.
As shown in FIG. 5, the valve body 1 is formed with a pump passage 2 communicating with the pump P and an actuator passage 3 communicating with the single acting cylinder S. A spool hole 4 is formed in the valve body 1, and a main spool 5 is slidably incorporated in the spool hole 4.
The main spool 5 maintains a dimensional relationship in which one end protrudes from one side surface of the valve body 1 and the other end is located in the middle of the spool hole 4.
In addition, an operation lever 6 is connected to one end of the main spool 5, and by operating this operation lever 6, the main spool 5 slides in the spool hole 4, and the pump passage 2 is connected to the actuator passage 3. The pump passage 2 is communicated with the tank passage 7.

On the other hand, a discharge mechanism A is incorporated in the spool hole 4 on the same axis as the main spool 5 so as to face the main spool 5. In the discharge mechanism A, the valve body 8 is incorporated in the spool hole 4, and the discharge valve 9 is incorporated in the valve body 8. The valve body 8 is provided with a spring chamber 10, and a spring 11 is provided in the spring chamber 10 so that its elastic force is applied to one end of the discharge valve 9.
The discharge valve 9 is pressed against the main spool 5 side by the elastic force of the spring 11, and in this state, the seat portion 9 a of the discharge valve 9 is pressed against the seat surface 12, and the actuator passage 3, the tank passage 7, The communication of is blocked.
Note that the other end of the discharge valve 9 and the front end of the main spool 5 in the neutral position are opposed to each other with a slight interval in a state where the seat portion 9a is in pressure contact with the seat surface 12. Reference numeral 13 in the figure denotes a load check valve that permits only the flow from the pump passage 2 to the actuator passage 3.

An actuator (not shown) is connected to the single acting cylinder S, and a link mechanism L is connected to the actuator, and the operation of the actuator is fed back to the main spool 5 by the link mechanism L. Although the description of the specific configuration of the link mechanism L is omitted, the link mechanism L mechanically connects the main spool 5 and the actuator, and the main spool 5 is connected in accordance with the operation of the actuator. Return to the neutral position.
In other words, the actuator operates only according to the switching amount of the main spool 5, and when the actuator operates according to the switching amount of the main spool 5, the operation of the actuator is used as a driving force to return the main spool 5 to the neutral position. Thus, the operation of the actuator is stopped.

Next, the operation of the hydraulic control apparatus having the above configuration will be described.
When operating the actuator against a load acting on the actuator (here, when the single-acting cylinder S is extended upward), the operation lever 6 is operated to move the main spool 5 to the right in the figure. .
Then, as shown in FIG. 6, the pump passage 2 and the actuator passage 3 communicate with each other through the annular groove formed in the main spool 5. Accordingly, the hydraulic oil discharged from the pump P pushes the load check valve 13 in the actuator passage 3 and is guided to the single acting cylinder S. And with the said hydraulic fluid, while extending the single acting cylinder S against the load which acts on an actuator, an actuator can be operated by extension of this single acting cylinder S.

On the other hand, when operating the actuator in a direction in which a load is applied to the actuator (here, when the cylinder S is contracted), the operation lever 6 is operated to move the main spool 5 in the left direction in the figure.
Then, as shown in FIG. 7, the pump passage 2 and the tank passage 7 communicate with each other through an annular groove formed in the main spool 5. Accordingly, the hydraulic oil discharged from the pump P is directly returned from the pump passage 2 to the tank passage 7 and the tank through the annular groove.
When the main spool 5 moves leftward in the figure, the tip of the main spool 5 moves the discharge valve 9 leftward in the figure against the elastic force of the spring 11. Thus, when the discharge valve 9 moves to the left in the figure, the seat portion 9a of the discharge valve 9 is opened from the seat surface 12, and the actuator passage 3 and the tank passage 7 communicate with each other. The return oil can be discharged from the cylinder S. Therefore, when the actuator is operated in a direction in which a load is applied to the actuator, the single-action cylinder S is contracted by its own weight, and the actuator can be operated by the contraction of the single-action cylinder S.

As described above, when the single-acting cylinder S is expanded and contracted to operate the actuator, the main spool 5 gradually returns to the neutral position via the link mechanism L as the actuator is operated. In the state where the main spool 5 is returned to the neutral position, as shown in FIG. 4, the discharge mechanism A is kept in the closed state and the actuator passage 3 is blocked by the load check valve 13. The cylinder S can be firmly held.
In the neutral state, the pump passage 2 and the tank passage 7 communicate with each other via the annular groove of the main spool 5, so that the hydraulic oil discharged from the pump can be returned directly to the tank.
Thus, according to the hydraulic control device described above, the actuator can be operated according to the switching amount of the main spool 5, and the operation is automatically stopped by the link mechanism L when the actuator is operated by a predetermined amount. be able to.
Japanese Utility Model Publication No. 53-16791

According to the hydraulic control device described above, the operation of the actuator becomes a driving force for returning the main spool 5 to the neutral position. That is, since the main spool 5 gradually moves to the neutral position as the actuator is operated, the movement of the main spool 5 is also stopped immediately when the actuator is stopped.
Therefore, when a link mechanism that feeds back the operation of the actuator is used, there is a disadvantage that the main spool 5 cannot be reliably returned to the neutral position when the operation of the actuator is stopped.

More specifically, when the single-action cylinder S is extended and the actuator is operated, the main spool 5 is gradually returned to the neutral position in accordance with the operation of the actuator. As the main spool 5 returns to the neutral position, the opening degree of communication between the pump passage 2 and the actuator passage 3 gradually decreases, and the pressure in the actuator passage 3 gradually decreases.
Even when the pump passage 2 and the actuator passage 3 are in communication with each other, the extension of the single-action cylinder S stops when the pressure in the actuator passage 3 becomes equal to or lower than the load pressure acting on the single-action cylinder S. As a result, the main spool 5 cannot move any more in a state where the main spool 5 has not completely returned to the neutral position as the actuator is stopped.
Thus, in a state where the main spool 5 does not return to the neutral position completely, the communication between the pump passage 2 and the tank passage 7 is interrupted, or the communication opening degree becomes extremely small, and the pump passage 2 There was a problem that boost pressure was generated inside and the energy loss increased.

  An object of the present invention is to provide a hydraulic control device that compensates for the disadvantage of the link mechanism that the main spool cannot be completely returned to the neutral position and that reduces energy loss.

According to the present invention, a valve body having a spool hole is formed with a pump passage communicating with a pump, an actuator passage communicating with a single acting cylinder, and a tank passage communicating with a tank, and on the outer periphery of the main spool. Forms an annular recess that allows the pump passage and the tank passage to communicate with each other when the main spool is in a neutral position or a lowered position, and the main spool is slidably incorporated in the spool hole. A discharge mechanism that operates in association with the spool is provided, and when the main spool is switched to the raised position, the pump passage is connected to the actuator passage to raise the single-acting cylinder, and the main spool is switched to the lowered position. When the discharge mechanism is opened, the actuator passage is tanked through this discharge mechanism. The single-acting cylinder is operated by lowering the single-acting cylinder by communicating with the road, and the main spool and the single-acting cylinder are directly or indirectly linked via the link mechanism. It is premised on a hydraulic control device configured to stop the single-acting cylinder by returning the main spool to the neutral position when the operation amount is fed back.

Assuming the above configuration, the main spool is incorporated with a sub spool to which spring elasticity is applied, and one end of the sub spool is exposed to the first pressure chamber and the other end is exposed to the second pressure chamber. However, when the main spool is at or near the neutral position, the first pressure chamber communicates with the tank passage, and the second pressure chamber communicates with the port formed in the main spool and the communication passage formed in the sub spool. The sub-spool is moved by the balance between the pressure in the second pressure chamber and the elastic force of the spring, and the pump passage is communicated with the tank passage through the communication passage. The main spool is in the neutral position. located in the vicinity, when said annular recess communicating with said pump passage and the tank passage is shut off or opening thereof becomes small While ensuring the communication between the pump passage and the tank passage through the communication passage, when the main spool is switched to the raised position, the load pressure of the single acting cylinder acts on the first and second pressure chambers, and the spring The sub-spool is moved by the elastic force of the valve to close the communication passage, and the communication between the pump passage and the tank passage is blocked.

According to the present invention, when the main spool is in the neutral position or in the vicinity of the neutral position, the pump passage and the tank passage communicate with each other via the communication passage formed in the sub spool, so that the main spool is completely returned to the neutral position. Even without this, the pump passage can be reliably communicated with the tank passage.
Therefore, it is possible to compensate for the drawbacks of the link mechanism and reduce energy loss in the neutral state of the main spool.
Further, since the sub spool functions as an unload valve, it is not necessary to separately provide an unload valve in the valve body. Therefore, according to the present invention in which the sub spool is incorporated in the main spool, the valve body can be downsized as compared with the case where an unload valve is separately provided.

The hydraulic control device of this embodiment will be described with reference to FIGS. Note that the hydraulic control device of this embodiment is different only in the configuration of the main spool in the conventional hydraulic control device, and the other configurations are all the same. Therefore, the same components as those in the conventional hydraulic control device will be described with the same reference numerals.
As shown in FIG. 1, the valve body 1 has a pump passage 2 communicating with the pump P and an actuator passage 3 communicating with the single acting cylinder S. A spool hole 4 is formed in the valve body 1, and a hollow main spool MS is slidably incorporated in the spool hole 4.

The main spool MS maintains a dimensional relationship in which one end protrudes from one side surface of the valve body 1 and the other end is located in the middle of the spool hole 4.
An operation lever 6 is connected to one end of the main spool MS, and the main spool MS slides in the spool hole 4 by operating the operation lever 6.
The main spool MS is formed with first to third annular recesses 21, 22 and 23, and the annular recesses 21, 22 and 23 are connected to ports p 1, p 2 and p 3 communicating with the inside of the main spool MS. Respectively.

When the main spool MS is in the illustrated neutral position, the first annular recess 21 allows the actuator passage 3 and the tank passage 7 to communicate with each other via the tank communication portion 24. When the main spool MS is in the neutral position, the second annular recess 22 opens to the pump passage 2 side, while the third annular recess 23 maintains a dimensional relationship that allows the pump passage 2 and the tank passage 7 to communicate with each other. Yes.
The main spool MS having the above-described configuration slides in the spool hole 4 and communicates the pump passage 2 with the actuator passage 3 through the first annular recess 21 or pumps through the third annular recess 23. The passage 2 is communicated with the tank passage 7.

A sub spool SS is incorporated in the main spool MS, and one end of the sub spool SS faces the first pressure chamber 25 and the other end faces the second pressure chamber 26. The first pressure chamber 25 is provided with a spring 27, and the elastic force of the spring 27 is applied to one end of the sub spool SS.
Further, a communication passage 28 is formed in the main body of the sub spool SS, and a pilot hole 29 is formed at the end of the sub spool SS on the second pressure chamber 26 side. The second pressure chamber 26 communicates with the pump passage 2 through the communication passage 28 and the pilot hole 29.

On the other hand, a discharge mechanism A is incorporated in the spool hole 4 on the same axis as the main spool MS so as to face the main spool MS. In the discharge mechanism A, the valve body 8 is incorporated in the spool hole 4, and a discharge valve 9 is incorporated in the valve body 8. The valve body 8 is provided with a spring chamber 10, and a spring 11 is provided in the spring chamber 10 so that its elastic force is applied to one end of the discharge valve 9.
Then, the elastic force of the spring 11 pushes the discharge valve 9 toward the main spool MS, and in this state, the seat portion 9a of the discharge valve 9 presses against the seat surface 12, and the actuator passage 3 and the tank passage 7 The communication of is blocked.
Note that the other end of the discharge valve 9 and the front end of the main spool MS in the neutral position are opposed to each other with a slight interval in a state where the seat portion 9a is in pressure contact with the seat surface 12. Reference numeral 13 in the figure denotes a load check valve that permits only the flow from the pump passage 2 to the actuator passage 3.

  An actuator (not shown) is connected to the single-acting cylinder S, and a link mechanism L is connected to the actuator. The link mechanism L feeds back the operation of the actuator to the main spool MS. Although the description of the specific configuration of the link mechanism L is omitted, the link mechanism L mechanically connects the main spool MS and the actuator, and the main spool MS is connected according to the operation of the actuator. Return to the neutral position.

In other words, the actuator operates only according to the switching amount of the main spool MS, and when the actuator operates according to the switching amount of the main spool MS, the operation amount of the actuator is fed back to bring the main spool MS to the neutral position. The single action cylinder S is stopped by returning.
However, the link mechanism L may be linked to an actuator or may be linked to a single acting cylinder S. That is, the main spool MS and the single-acting cylinder S need only be linked directly or indirectly via the link mechanism L.

Next, the operation of the hydraulic control apparatus having the above configuration will be described.
When operating the actuator against the load acting on the actuator (here, when the single-acting cylinder S is extended upward), the operating lever 6 is operated to raise the main spool MS (rightward in the figure). ).
Then, as shown in FIG. 2, the pump passage 2 and the actuator passage 3 communicate with each other through the first annular recess 21 formed in the main spool MS, and the tank communication portion 24 is blocked by the main spool MS, The actuator passage 3 and the tank passage 7 are blocked.

The load pressure of the single acting cylinder S acts on the first pressure chamber 25 via the port p 1, and the single pressure acts also on the second pressure chamber 26 via the port p 2 → the communication path 28 → the pilot hole 29. The load pressure of the cylinder S acts.
Thus, since the load pressure of the single acting cylinder S acts on both pressure chambers 25 and 26 and both pressure chambers 25 and 26 become the same pressure, the sub spool SS is set to the second pressure by the elastic force of the spring 27. Move to the chamber 26 side.
In this state, one end of the communication path 28 formed in the sub spool SS is displaced from the opening of the port p3, and the communication path 28 is kept closed.

Further, at the raised position of the main spool MS, the third annular recess 23 blocks the pump passage 2 and the tank passage 7.
Therefore, at the raised position of the main spool MS, the pump passage 2 and the tank passage 7 are maintained in a completely blocked state.
As described above, when the main spool MS is switched to the raised position, the hydraulic oil discharged from the pump P pushes the load check valve 13 in the actuator passage 3 and is guided to the single acting cylinder S. And with the said hydraulic oil, while operating the single acting cylinder S against the load which acts on an actuator, the actuator can be operated by the raising operation of this single acting cylinder S.

On the other hand, when the actuator is operated as described above, the main spool MS is returned to the neutral position by the link mechanism L based on the operating force of the actuator. At this time, if the operation of the actuator is stopped before the main spool MS is completely returned to the neutral position, the main spool MS cannot move further in the vicinity of the neutral position.
As described above, in the vicinity of the neutral position of the main spool MS, the communication opening degree of the third annular recess 23 (indicated by the symbol x in FIG. 1) may be kept small. If the opening degree of the third annular recess 23 (reference numeral x in FIG. 1) is small, the communication opening degree between the pump passage 2 and the tank passage 7 becomes small, and the hydraulic oil discharged from the pump P is made into the third annular shape. There is a possibility that it cannot be discharged from the recess 23 to the tank passage 7.

However, in this embodiment, when the opening degree of the third annular recess 23 (reference numeral x in FIG. 1) is small and the pressure of the pump passage 2 becomes high, the sub-spool SS is performed as follows. The hydraulic oil in the pump passage 2 is discharged to the tank passage 7 via
That is, when the main spool MS is in the vicinity of the neutral position, the tank communication portion 24 is opened, so that the first pressure chamber 25 becomes the tank pressure. On the other hand, when the opening degree of the third annular recess 23 is small and the pressure of the pump passage 2 becomes high, the pressure acts on the second pressure chamber 26 via the communication passage 28. Then, the sub spool SS moves to the first pressure chamber 25 side against the elastic force of the spring 27.

Thus, if the sub spool SS moves to the first pressure chamber 25 side, both ends of the communication passage 28 open to the ports p2 and p3, so that the pump passage 2 communicates with the tank passage 7 via the communication passage 28. be able to. As a result of the communication of the pump passage 2 to the tank passage 7 by the communication passage 28, the pressure of the second pressure chamber 26 also decreases when the pressure of the pump passage 2 decreases. Move again to the right in the figure.
As described above, according to the hydraulic control apparatus of this embodiment, even when the main spool MS does not completely return from the raised position to the neutral position, the pump passage 2 and the tank passage 7 are communicated with each other via the sub spool SS. Thus, the hydraulic oil can be reliably returned to the tank. Therefore, no boost pressure is generated in the pump passage 2 and energy loss can be reduced.

On the other hand, when the actuator is operated in the load direction acting on the actuator from the neutral state shown in FIG. 1 (here, when the single-acting cylinder S is contracted downward), the operation lever 6 is operated to operate the main spool MS. Move in the downward direction (left direction in the figure).
Then, as shown in FIG. 3, the pump passage 2 and the actuator passage 3 are blocked by the main spool MS, and the pump passage 2 and the tank passage 7 communicate with each other through the third annular recess 23. Therefore, the hydraulic oil discharged from the pump P is returned to the tank from the third annular recess 23 via the tank passage 7.

  On the other hand, when the main spool MS moves in the downward direction, the tip of the main spool MS moves the discharge valve 9 in the left direction in the figure against the elastic force of the spring 11. Thus, when the discharge valve 9 moves to the left in the figure, the seat portion 9a of the discharge valve 9 is opened from the seat surface 12, and the actuator passage 3 and the tank passage 7 communicate with each other. The return oil can be discharged from the cylinder S. Therefore, when operating the actuator in a direction in which a load is applied to the actuator, the single-action cylinder S is lowered (contracted) by its own weight, and the actuator is moved by the downward-action (contraction) of the single-action cylinder S. Can be operated.

  As described above, when the single-acting cylinder S is lowered and the actuator is operated, the main spool MS gradually returns to the neutral position via the link mechanism L as the actuator is operated. As the main spool MS moves in the neutral direction, the discharge valve 9 returns to the closed position again, and the movement of the single acting cylinder S stops.

  In the lowered position of the main spool MS, the first annular recess 21 moves to open the tank communication portion 24 and the actuator passage 3 communicates with the tank passage 7, so that the first pressure chamber 25 becomes the tank pressure. On the other hand, since the ports p 2 and p 3 are also communicated with the tank passage 7, the tank pressure also acts on the second pressure chamber 26 via the communication passage 28 and the pilot hole 29. Thus, since both pressure chambers 25 and 26 have the same pressure, the sub spool SS is moved to the second pressure chamber 26 side by the elastic force of the spring 27, and the communication path 28 is kept closed. Yes.

In the above embodiment, the contraction direction of the single-acting cylinder S is made coincident with the lead-down direction (vertical direction in the figure), but the single-acting cylinder S does not necessarily have to be installed in the illustrated direction.
For example, as shown in FIG. 4, the single-acting cylinder S may be laid in the horizontal direction, and the single-acting cylinder S may be contracted in the horizontal direction due to a load. That is, as shown in the figure, the load is applied in the direction in which the single acting cylinder S contracts. Then, the rod is extended in the left direction in the figure against the load of the single action cylinder S, or the single action cylinder S is contracted in the right direction in the figure by a load acting on the single action cylinder S, that is, its own weight. May be.
However, in this case, the direction in which the single-acting cylinder S is elongated in the left direction in the figure is the “upward direction of the main spool MS”, and the extending operation of the single-acting cylinder S at this time is the “raising operation”. The direction in which the single-acting cylinder S is contracted rightward in the figure is the “lowering direction of the main spool MS”, and the contracting operation of the single-acting cylinder S at this time is the “lowering operation”.

It is a figure which shows the state which hold | maintained the main spool in the neutral position. It is a figure which shows the state which has a main spool in a raising position. It is a figure which shows the state which has a main spool in a lowered position. It is a figure which shows the state which placed the single acting cylinder horizontally. In the conventional hydraulic control apparatus, it is a figure which shows the state which hold | maintained the main spool in the neutral position. In the conventional hydraulic control apparatus, it is a figure which shows the state which hold | maintained the main spool in the raising position. In the conventional hydraulic control apparatus, it is a figure which shows the state which hold | maintained the main spool in the lowered position.

Explanation of symbols

Reference Signs List 1 valve body 2 pump passage 3 actuator passage 4 spool hole 7 tank passage 25 first pressure chamber 26 second pressure chamber 27 spring 28 communication passage A discharge mechanism L link mechanism P pump S single acting cylinder MS main spool SS sub spool p1 p3 port

Claims (1)

The valve body having the spool hole is formed with a pump passage communicating with the pump, an actuator passage communicating with the single-acting cylinder, and a tank passage communicating with the tank. Is in a neutral position or a lowered position, an annular recess for communicating the pump passage and the tank passage is formed, and a main spool is slidably incorporated in the spool hole and is associated with the main spool. When the main spool is switched to the raised position, the pump passage is connected to the actuator passage to raise the single-acting cylinder, and when the main spool is switched to the lowered position, the discharge mechanism is provided. And the actuator passage is connected to the tank passage via this discharge mechanism. The single-acting cylinder is lowered and the main spool and the single-acting cylinder are linked directly or indirectly via the link mechanism. In the hydraulic control apparatus configured to return the main spool to the neutral position by feedback of the operation amount and stop the single-acting cylinder, the main spool incorporates a sub spool to which the elastic force of the spring is applied. When one end of the sub spool faces the first pressure chamber, the other end faces the second pressure chamber, and the main spool is in the neutral position or near the neutral position, the first pressure chamber communicates with the tank passage, The second pressure chamber is connected to the pump through a port formed in the main spool and a communication path formed in the sub spool. The sub spool is moved by the balance between the pressure in the second pressure chamber and the elastic force of the spring, the pump passage is communicated with the tank passage through the communication passage, and the main spool is positioned near the neutral position. When the annular recess for communicating the pump passage and the tank passage is blocked or the opening thereof is reduced, the communication between the pump passage and the tank passage is ensured through the communication passage, while the main spool is When switched to the raised position, the load pressure of the single acting cylinder acts on the first and second pressure chambers, and the sub spool is moved by the elastic force of the spring to close the communication passage, and the pump passage and the tank passage Hydraulic control device configured to cut off communication with the machine.

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