JPH0348355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant horsepower control device that controls the horsepower of the variable pump to be constant and also enables cut-off control to minimize the discharge amount when the discharge pressure exceeds a predetermined value.

(Conventional Control Device) In the conventional control device shown in FIG. 1, oil discharged from the variable pump 1 flows into the passage 2, acts on the end surface of the spool 3, and also flows into the pressure chamber 4.

When the pump pressure exceeds the set pressure, the spool 3 moves together with the spring holder 5 against the first spring 6, and the passage 2 and the pilot passage 7
communicate with.

When both passages 2 and 7 communicate with each other, pressure oil from the variable pump 1 also flows into the pressure chamber 8. At this time, since the pressure receiving area of one rod part 9 is larger than that of the other rod part 10, the piston 11 moves in the direction of the arrow to reduce the discharge amount of the variable pump 1 while bending both springs.

As the piston moves as described above and deflects the first and second springs, the spring force increases. Therefore, the spool 3 moves to the left in the drawing, and the land 12 blocks the pilot passage 7, so that pressure oil is no longer supplied to the pressure chamber 8. Since no pressure oil is supplied to the pressure chamber 8, the piston 11 stops at this position. In other words, the variable pump 1 maintains the discharge amount at the stop position.

When the discharge pressure of the variable pump further increases from the above state, the spool 3 again moves to the right in the drawing, opens the pilot passage 7, and guides the increased pump pressure to the pressure chamber 8, so that the piston 11 further moves to the right in the drawing. direction to decrease the discharge amount of the variable pump 1.

On the other hand, if the discharge pressure of the variable pump decreases,
Since the spool 3 is acted upon by the first spring 6 and the second spring 13, its land 12 moves to the illustrated position which is different from the pilot passage position. When the land of the spool reaches the illustrated position, the pressure chamber 8 will be in communication with the tank 14, so the pressure in the pressure chamber 8 will drop. When the pressure in the pressure chamber decreases, the piston 11 moves in the opposite direction to the arrow, ie, in the direction of increasing the discharge amount of the variable pump 1, due to the action of the springs 6 and 13.

As described above, the relative relationship between the discharge amount and the discharge pressure of the variable pump is kept constant, and its horsepower is controlled to be constant.

When the discharge pressure of the variable pump 1 becomes equal to or higher than the set pressure, the cut-off control mechanism a functions.
It is as follows.

That is, when the discharge pressure of the variable pump 1 exceeds the set pressure determined by the third spring 15, the spool 16 moves against the third spring 15. If the spool moves in this way, the land 17 will pass through the pilot passage 7 position and move to the passage 2.
and the pilot passage 7 are directly communicated with each other.

Therefore, high pressure oil from the pump flows into the pressure chamber 8, causing the piston 11 to further move to the left in the drawing, thereby minimizing the discharge amount of the variable pump. In other words, the discharge pressure of the variable pump is
When the pressure exceeds the set pressure determined in step 5, the discharge amount of the variable pump is gradually reduced to perform cut-off control.

In the conventional control device as described above, the cut-off control mechanism a must be specially provided, which has the disadvantage of complicating the structure.

Especially in the above conventional case, two spools 3,
16, these spools sometimes interfered with each other, resulting in unstable performance.

(Objective of the Invention) The object of the invention is to provide a control device that eliminates the need for a cut-off control mechanism and can be controlled using a single spool.

(Embodiment of the present invention) In the embodiment shown in FIG.
The small diameter portion 21a of the first pressure chamber 22 faces the pressure chamber 22,
The large diameter portion 21b faces the other pressure chamber 23.

An arm 24 is fitted to the small diameter portion 21a, and the arm and the small diameter portion 21a are connected with a pin 25 so that the piston 21 and the arm 24 move integrally.

The arm 24, which moves integrally with the piston 21 as described above, is connected to the variable pump 26, and when the arm moves in the direction of the arrow 27 from the illustrated state, the discharge amount of the variable pump 26 is reduced. There is.

The one pressure chamber 22 communicates with the variable pump 26 via the passage 28, while the other pressure chamber 23 communicates with the passage 28→one pressure chamber 22→passage 29→spool housing 30→pilot passage 31. It communicates with the variable pump 26 via the above.

The spool housing 30 includes a spool 3
The inner end of this spool 32 is brought into contact with a spring holder 33.

This spring holder 33 is located in a control chamber 34 formed in the valve body 20, and one end of the arm 24 faces inside this control chamber 34, and an insertion hole 24a is formed in one end of this arm. There is. A slider 35 is slidably inserted into the insertion hole 24a, and an annular protrusion 35a having a larger diameter than the insertion hole 24a is formed on one side of the slider 35. The annular protrusion 35a is brought into contact with the outside of the arm 24, which is the side opposite to the spring holder 33.

Annular protrusion 35 of slider 35 as described above
A first spring 37 is interposed between the side wall 36 of the control chamber 34 and the annular protrusion 35.
A second spring 38 and a third spring 39 are interposed between a and the spring holder 33.

The initial load F ₁ of the first spring 37 and the initial loads F ₂ and F 3 of the second and third springs 38 and ₃₉ are set to have a relationship of F ₁ >F ₂ +F ₃ . .

Therefore, when no pressure is applied to both ends of the piston 21, the arm 24 is set at the minimum discharge position A by the action of the first spring 37.

By providing each spring as described above, the spring holder 33 comes into contact with the spool 32, and when the arm 24 etc. maintain the state shown in the drawing, the spool 32 maintains the relative position shown in the drawing. do.

That is, when the spool 32 maintains the state shown in the figure, its land 32a is offset from the pilot passage 31, and the pilot passage 31
is communicated with a drain passage 40 formed in the spool housing 30. When the spool 32 moves to the right in the drawing, the land 32a passes through the pilot passage 31 position, causing the passage 29 and the pilot passage 31 to communicate with each other.

Also, at the center of the slider 35 is an adjuster 4.
The adjuster 41 has an outer end protruding outward from the valve body 20, and a nut 42 is engaged with the protruding end. On the other hand, a flange-shaped stopper 41a is formed at the inner end of the adjuster 41. Therefore, the slider 35 can move within the range of stroke l from the illustrated position to the stopper 41a. However, this stroke 1 can be arbitrarily adjusted by adjusting the tightening position of the nut 42.

When the discharge pressure of the pump 26 is zero, the first spring 37 maintains the position where the slider 35 contacts the stopper 41a, that is, the minimum discharge position A.

However, when the pump 26 is driven, its discharge pressure flows into one pressure chamber 22 and the piston 2
It acts on the end face of the small diameter portion 21a of 1 and also acts on the end face of the spool 32. When pressure is applied to the small diameter portion 21a in this way, the piston 21 moves against the first spring 37 due to the action of the pressure, and the arm 24 reaches the maximum discharge position B, which causes the pump 26 to discharge. Maximize quantity.

When the pump discharge pressure rises from the above state and the pressure overcomes the spring force of the spring, the spool 32 moves against the second and third springs 38 and 39 and connects the passage 29 and the pilot passage 31. let

When the passage 29 and the pilot passage 31 communicate with each other, the pump discharge pressure also flows into the other pressure chamber 23 and acts on the large diameter portion 21b of the piston 21.

Therefore, the piston 21 has a small diameter portion 2
Due to the area difference between 1a and large diameter portion 21b, arrow 2
Move in 7 directions to decrease the pump discharge amount.

When the piston 21 moves as described above, the slider 35 is moved by the action of the first spring 37.
The second and third springs 38,
Flex 39. The spool stops at a position where the spring force of the spring thus bent and the force acting on the spool 32 are balanced.

If the land 32a coincides with and closes the pilot passage 31 at this stop position, then
The piston 21 stops at the position and maintains the pump discharge amount at that position.

Furthermore, when the land 32a is in the position shown in the balance position, the other pressure chamber 23 communicates with the drain passage 40, so the piston 21 moves in the direction opposite to the arrow 27 due to the pressure in one pressure chamber 22. and increase its discharge amount.

Furthermore, if the pump discharge pressure is high, the land 32a
remains in the position passing through the pilot passage 31, so that pump discharge pressure continues to be supplied to the other pressure chamber 23. Therefore, the piston 21
continues to move in the direction of the arrow, but at this time the slider 35 hits the stopper 41a of the adjuster 41, so it does not move beyond the stroke l.
When the slider stops in this way, the stopper 41
Second and third springs 38, 3 in position a
9 is specified, and the corresponding set pressure is also specified.

If the pump discharge pressure is higher than the set pressure determined in this way, the passage 29 and the pilot passage 3
Since the piston 21 and the arm 24 remain in communication with each other, only the piston 21 and the arm 24 move in the direction of the arrow, reducing the discharge amount of the pump and performing so-called cut-off control.

(Configuration of the present invention) The configuration of the present invention includes an arm that adjusts the tilting angle of a variable pump, an arm that moves integrally with the arm, and forms a small diameter portion and a large diameter portion, and the small diameter portion. A piston that faces one pressure chamber and a large diameter portion that faces the other pressure chamber, and is installed in a communication path between both pressure chambers, and opens and closes the communication path between both pressure chambers according to its movement position. and a spool that operates to switch so that the pressure chamber facing the large diameter portion communicates with the drain passage, a spring that determines a set pressure for the spool according to the amount of movement of the piston, and one end of the spring that supports the spool. and a slider configured to move integrally with the arm to determine the amount of deflection of the spring, stop when it moves to a predetermined position, and move relative to the arm; It is characterized by the fact that it consists of a passageway that leads to.

With the above configuration, when the pump discharge pressure increases, the piston moves to reduce the pump discharge amount. Furthermore, when the discharge pressure decreases, the piston moves in the opposite direction to the above to increase the discharge amount.

As the piston moves, the slider moves, and a set pressure corresponding to the amount of movement is specified. When the pressure exceeds a predetermined value, the slider stops, and the set pressure at that stop position is determined.

Therefore, when the discharge pressure of the pump exceeds the set pressure at the stop position of the slider, only the piston moves to reduce the discharge amount, performing so-called cut-off control.

(Effects of the Present Invention) Since the present invention is configured as described above, one spool is sufficient, and two spools are not required as in the conventional case.

This simplifies the configuration and eliminates the instability of performance due to mutual interference between the two spools as in the prior art.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a sectional view showing an embodiment of the present invention. 21...Piston, 21a...Small diameter part, 21b
...large diameter part, 22, 23 ... pressure chamber, 24 ... arm, 26 ... variable pump, 32 ... spool,
35...Slider, 38, 39...Spring,
40...Drain passage.

Claims (1)

[Claims] 1. An arm that adjusts the tilting angle of the variable pump, and an arm that moves integrally with this arm and forms a small diameter part and a large diameter part, with the small diameter part facing one pressure chamber, and the large diameter part a piston facing the other pressure chamber, and a piston provided in a communication path between the two pressure chambers,
and a spool that opens and closes a communication passage between both pressure chambers in accordance with the movement position thereof, and switches the pressure chamber facing the large diameter portion to communicate with the drain passage;
a spring that determines a set pressure for the spool according to the amount of movement of the piston; and a spring that supports one end of the spring and moves integrally with the arm to determine the amount of deflection of the spring;
A constant horsepower control device for a variable pump, comprising a slider configured to stop when it moves to a predetermined position and move relative to the arm, and a passage that guides the discharge pressure of the pump to the end face of the spool.