JPS58222991A - Constant power control device for variable delivery pump - Google Patents

Abstract

PURPOSE:To prevent a circuit from heating due to the operation of a relief valve and save energy by automatically minimizing the discharge of a variable delivery pump through the operation of a cutoff control system when the discharge pressure of said variable delivery pump exceeds a set pressure determined by said control system. CONSTITUTION:The main elements of a cutoff control system (a) are a spool 39 whose outer end is applied to a pressure introducing passage 35, a spring holder 40, and a No.3 spring 41. When the discharge pressure of a variable pump 34 exceeds a prescribed pressure determined by the No.3 spring 41, the spool 39 is moved against the spring 41. As its land 44 passes through a pilot passage 45, a pressure-introducing passage 33 is connected to the pilot passage 45. Accordingly, a high pressure oil from a pump 1 flows into a pilot chamber 36 allowing a piston 18 to move further toward the left on the figure and minimizes the discharge of the pump 1 automatically, thereby preventing the circuit from heating due to the operation of a relief valve.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device that adjusts the tilt angle to keep the horsepower of the variable pump constant.

(Conventional Control Device) The conventional control device shown in FIG. 1 has a piston 2 built into its cylinder 1, and a spool 3 and a rod 4 arranged in series within the piston.

A first spring 5 is interposed between the spool 3 and the piston 2, and the inner end of the spool is normally held in the state shown in the drawing.

In the above state, oil flowing from the auxiliary pump 6 into the first annular groove 7 of the spool flows into the pressure chamber 9 through the oil passage 8 and moves the piston to the right in the drawing.

The piston 2 moves according to the pressure in the pressure chamber as described above.
The cylindrical portion 1O faces into the spring chamber 11 of the cylinder 1, and the tip of the rod 4 projects from the cylindrical portion 10.

The spring chamber 11 is provided with two long and short second and third springs 13 and 14 between it and the spring holder 12.

A plunger 15 is installed inside the spring holder 12, and this plunger 15 is connected to a variable pump 16.
The relationship is such that it senses the pressure and moves.

When the variable pump 16 is driven and the auxiliary pump 6 is driven at the same time, the oil of the auxiliary pump 6 first flows into the pressure chamber and moves the piston 2 as described above. As the piston moves, the tilt angle of the variable pump changes, changing its discharge amount from the minimum to the maximum. At this time, when the tip of the rod 4 that has stroked together with the piston 2 hits the spring holder 12, the rod 4 and the spool 3
and stop, and both of them and the piston 2 move relative to each other.

When the spool and piston move relative to each other as described above,
Communication between the auxiliary pump 6 and the pressure chamber 9 is cut off, and the piston 2 stops at the position.

At this time, the discharge pressure of the variable pump 16 is
Therefore, the spring holder 12 is moved together with the plunger 15, and the first to third springs are deflected.

Then, the spool is pushed to a position where the resultant force of each spring and the pressure acting on plunger 15 are balanced, and the piston is stroked to this balanced position to control the discharge amount according to the discharge pressure of the variable pump. In other words, the horsepower of the variable pump is controlled at a constant level.

Conventional control devices such as slippers not only require an auxiliary pump, but also require separate installation of a biston and a plunger, which has the disadvantage of complicating the structure.

In addition to having a complicated structure, the piston has the disadvantage that the outer diameter in contact with the cylinder and the inner diameter in contact with the spool must be finished with high precision, which increases manufacturing costs accordingly.

Furthermore, as is clear from FIG. 2, which shows the characteristics of this conventional device, there is a drawback in that cut-off control cannot be performed on the high pressure side of the pump.

Since cut-off control is not possible on the high pressure side, pressure must be controlled on the high pressure side using a relief valve installed in the circuit, which causes the circuit pressure to become high temperature, resulting in large energy loss. was there.

(Objective of the present invention) The purpose of the present invention is to provide a control device with a simplified structure while eliminating the need for an auxiliary pump. The purpose is also to provide.

(Embodiment of the present invention) In the first embodiment shown in FIG.
8 is installed inside to be able to freely reciprocate, and this piston 18
Rod portions 19 and 20 are formed on both sides of the rod.

The rod portions 18.20 are slidably inserted into support holes 21.22 formed in the main body 17, with one rod portion 19 having a smaller cross-sectional area than the other rod portion 20.

A spring holder 23 is slidably housed in the support hole 21 into which one of the rod sections 19 is inserted, and there are two long and short sections between the spring holder 23 and the end surface of the rod section 18. First and second springs 24.2
5 is interposed. The first spring 24 is in constant contact with the end surface of the rod portion 18 and the spring holder 23, and the second spring 25 is made shorter than the first spring.

The spring holder 23 housed in the support hole 21 has slide rods 26 and 27 formed on both sides thereof, and one slide rod 26 is inserted into a slide hole 28 formed in the main body 17. The other slide rod 27 is inserted into a slide hole 29 of the rod portion 18 facing the support hole 21.

Slide inserted into the sliding hole 28 on the main body side as shown above
The inner end of a spool 30 is brought into contact with the end face of the spool 28, and the spool 30 is held in the state shown in the figure by the action of the first spring of the spring holder 23. At times, the relationship is such that the neutral position shown in the figure is maintained.

When the spool 30 is held at the neutral position, the land 31 intersects with the pilot passage 32 so that the pilot passage 32 is communicated with the tank passage 33.

When the spool 30 moves a little to the right in the drawing from the illustrated state, the land 3I completely aligns with the pilot passage 32 and closes the pilot passage 32, while
When further moved to the right in the drawing, the land 31 passes through the pilot passage position, and the pressure introduction passage 35 communicating with the variable pump 34 is brought into communication with the pilot passage 32.

The pilot passage 32 configured as described above communicates with a pilot pressure chamber 3B formed on the end surface side of the other rod portion 20. Further, the pressure introduction passage 35 is connected to the support hole 21.
It communicates with a pressure chamber 37 formed between the one rod portion 18 and the spring holder 23 .

Note that the reference numeral 38 in the figure is a tank connected to the tank passage 33.

However, when the variable pump 34 is driven now, the oil of the variable pump flows into the pressure introduction passage 35,
It acts on the end face of the 1'□' spool 30 and also flows into the pressure chamber 37.

When the pump pressure becomes equal to or higher than the set pressure, the spool 30 moves together with the spring holder 23 against the second spring 24, causing the pressure introduction passage 35 and the pilot passage 32 to communicate with each other.

When both roads 35 and 32 communicate with each other, pressure oil from the variable pump 34 flows into the pilot pressure chamber 36, but at this time, since the pressure receiving area of one rod part 18 is larger than that of the other rod part 22, the piston 18 moves in the direction of the arrow to reduce the discharge amount of the variable pump 34 while bending both springs.

”-The piston moves as shown in the figure. Since the second spring is deflected, its spring force increases. Therefore, the spool 3o moves to the left in the drawing, and the land 31 blocks the pilot passage 32, so that no pressure oil is supplied to the pilot pressure chamber 36. Since no pressure oil is supplied to the pilot pressure chamber 36, the piston 18 stops at this position. In other words, the variable pump 34 maintains the discharge amount at the stop position.

When the discharge pressure of the variable pump further increases from the above state, the spool 30 moves rightward in the drawing again to open the pilot passage 32 and guide the increased pump pressure to the pilot pressure chamber 3G, so that the piston 18 further increases. Move in the direction of the arrow to decrease the discharge amount of the variable pump 34.

Conversely, when the discharge pressure of the variable pump decreases, the spool 32 is acted upon by the springs 24, 25, so that the land 31 moves to the illustrated position which is different from the pilot passage position. When the land of the spool reaches the illustrated position, the pilot pressure chamber 36 communicates with the tank 38, so the pressure in the pilot pressure chamber 36 decreases. When the pressure in the pilot pressure chamber decreases, the piston 18 is moved by the spring 24.
．． 25, the variable pump 34 moves in the opposite direction to the arrow, that is, in the direction of increasing the discharge amount of the variable pump 34.

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.

The second embodiment shown in FIGS. 4 and 5 differs from the first embodiment only in that a control mechanism is provided to perform cut-off control when the discharge pressure of the variable pump becomes high. , the other configurations are the same as those of the first embodiment.

Therefore, components common to those in the first embodiment will be described using the same reference numerals.

The main body 17 of this second embodiment includes a cut-off control mechanism a.
This cutoff control mechanism has a spool 39, a spring holder 40, and a third spring 41 as main elements.

That is, the main body 17 is formed with a spring chamber 43 which is closed with a plug 42, and this spring chamber 4 is
3 has a spring holder 40 inside, and the third spring 41 is interposed between the spring holder 40 and the plug 42.

The spool 39, whose inner end is connected to the spring holder 40, has its outer end facing the pressure introduction passage 35. ' When the spool 39 thus constructed is in the neutral position shown, the land 44 of the spool is in the pilot passage 45.
The opening end of the pilot passage 45 and the relay passage 46 communicate with each other.

The pilot passage 45 is substantially the same as the pilot passage 32 of the first embodiment, and has the other end communicating with the pilot pressure chamber 3B. Further, the relay passage 46 communicates with the tank passage 33 or is interrupted depending on the movement position of the spool 30 described in the first embodiment.

When the variable pump 34 is driven, the piston 18 moves in the same manner as in the first embodiment, and the horsepower of the pump is controlled to be constant.

However, in this second embodiment, when the spool 30 moves rightward in the drawing and communicates with the pressure introduction passage 35, pressure oil flows into the pilot passage 45.

The discharge pressure of the variable pump is increased by the third spring 41.
When the pressure exceeds the set pressure determined by the spool 39, the third
, moves against the spring 41. If the spool moves like this, the land 45 will move into the pilot passage 45.
The pressure introduction passage 35 and the pilot passage 45
communicate directly with

Therefore, high pressure oil from the pump flows into the pilot pressure chamber 36, causing the piston 18 to further move to the left in the drawing, thereby minimizing the discharge amount of the variable pump. In other words, as is clear from the horsepower diagram shown in FIG. 5, when the discharge pressure of the variable pump exceeds the set pressure determined by the third spring 41, the discharge amount of the variable pump is gradually reduced.
Cutoff control will be performed.

(Structure and effect of the present invention) The control device according to claim 1 has one end of the piston for adjusting the tilt angle of the variable pump facing the pressure chamber, and the other end facing the pilot pressure chamber. At the same time, the pressure receiving area of one end of the piston facing the pressure chamber is made smaller than the pressure receiving area of the other end facing the pilot pressure chamber, and a spring holder is installed inside the pressure chamber, and this spring holder and the above A spring is interposed between the spring holder and one end of the piston, and one end of the slide rod of the spring holder, that is, the end opposite to the pressure chamber, is brought into contact with a spool, and this spool responds to the discharge pressure of the variable pump. The pressure introduction passage communicating with the variable pump is configured to communicate with the viroft pressure chamber or to cut off the communication.

In the above configuration, no auxiliary pump 2 like the conventional one is required. Since no auxiliary pump is required, energy efficiency is improved accordingly.

Further, in this invention, since the spool is provided outside the piston, there is no need to finish the inner diameter with high precision, unlike the conventional piston in which the spool is internally installed, and its processing becomes easy.

The control device according to claim 2 has one end of the piston for adjusting the tilt angle of the variable pump facing the pressure chamber, and the other end facing the pilot pressure chamber and the pressure chamber. The pressure receiving area at one end of the piston is made smaller than the pressure receiving area at the other end facing the pilot pressure chamber, and a spring holder is installed inside the pressure chamber, and a spring is inserted between the spring holder and the one end of the piston. On the other hand, one end of the slide rod of the spring holder, that is, the end opposite to the pressure chamber, is brought into contact with a spool, and this spool is connected to the variable pump according to the discharge pressure of the variable pump. The passage is configured to communicate with the pilot pressure chamber or to cut off the communication, and the spool of the cut-off control mechanism faces the pressure introduction passage indicated in -, and the cut-off control mechanism includes: When the maximum pressure of the variable pump exceeds the set pressure,
The pressure is guided to the pilot pressure chamber.

Therefore, when the discharge pressure of the variable pump becomes equal to or higher than the set pressure determined by the cut-off control mechanism, the cut-off control mechanism acts and automatically reduces the discharge amount of the variable pump. It can prevent fever.

Being able to prevent heat generation in the circuit means that 1. This reduces energy loss.

[Brief explanation of drawings]

Figure 1 is a sectional view of the conventional device, Figure 2 is a graph showing the same conventional control characteristics, Figure 3 is a sectional view of the first embodiment of the present invention, and Figures 4.5 are the second embodiment of the present invention. An example is shown in which FIG. 4 is a sectional view and FIG. 5 is a graph showing its control characteristics. 18...Piston, 23.40--Spring holder, 24.25...Spring, 28-Life slide rod, 30.39-No. spool, 34...Variable pump, 35-φ-Pressure Introduction passage, 36φ...Pilot passage, 37...Pressure chamber. Representative Patent Attorney Nobuyuki Shima 1,'1

Claims (2)

[Claims] (1) One end of the piston that adjusts the tilt angle of the variable pump faces the pressure chamber, the other end faces the pilot pressure chamber, and the pressure receiving area of the one end of the piston facing the pressure chamber is determined by the pilot pressure The pressure receiving area is smaller than the pressure receiving area of the other end facing the chamber, and a spring holder is installed inside the pressure chamber, and a spring is interposed between the spring holder and one end of the piston. One end, that is, the end opposite to the pressure chamber, is brought into contact with a spool, and the spool connects a pressure introduction passage communicating with the variable pump to the pilot pressure chamber, depending on the discharge pressure of the variable pump. , a constant power control device for a variable pump configured to cut off the communication. (2) One end of the piston that adjusts the tilt angle of the variable pump faces the pressure chamber, the other end faces the pilot pressure chamber, and the pressure receiving area of the one end of the piston facing the pressure chamber is determined by the pilot pressure The pressure receiving area is smaller than the pressure receiving area of the other end facing the chamber, and a spring holder is installed inside the pressure chamber, and a spring is interposed between the spring holder and one end of the piston. One end, that is, the end opposite to the pressure chamber, is brought into contact with a spool, and the spool connects a pressure introduction passage communicating with the variable pump to the pilot pressure chamber, depending on the discharge pressure of the variable pump. , the communication is cut off, and a spool of a cut-off control mechanism faces the pressure introduction passage, and the cut-off control mechanism controls when the maximum pressure of the variable pump exceeds the set pressure. A constant force control device for a variable pump configured to guide the pressure to the pilot pressure chamber.