JPS60187779A - Variable displacement pump - Google Patents

Abstract

PURPOSE:To reduce necessary power when the pump is not loaded by providing first and second control devices so as to be opposed under pinching the guide ring of the pump. CONSTITUTION:The hydraulic pressure chamber 46 of the first control device (a) is provided with an auxiliary piston 42 slidably. The auxiliary piston 42 is provided with a rod member 43 slidably. First control piston 40 is operated by first spring 47, supported by the auxiliary piston 42, and the rod member 43. The first control piston 40 makes the guide ring 4 eccentric. The hydraulic pressure chamber 57 of the second control device (b) is provided with the second control piston 50 having a pressure receiving area larger than the rod member 43. Further, second spring 56, having an energizing force larger than the same of the first spring 47, is effected on the piston 50. The second control piston 50 decreases the eccentricity of the guide ring 4. The delivery pressure of the pump is applied on both of the hydraulic pressure chambers 46, 57.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable displacement pump, and is effective when used as a hydraulic power source for, for example, a power steering device.

(Prior art) When a conventional pump is used as a hydraulic power source for a power steering device, when a steering operation is performed, that is, when a high load is applied to the pump, which is the hydraulic power source, high-pressure hydraulic oil is used according to the load. supply is required. However, at times other than those mentioned above, for example, when the vehicle is stopped or moving straight, supply of hydraulic oil from the pump is unnecessary, and thus the pump hydraulic oil is simply returned to the oil tank. In other words, even when there is no load on the pump,
Pumps always discharge a fixed amount of hydraulic oil, which results in wasted energy.

(Object of the Invention) In view of the above points, the present invention reduces the discharge amount when no load is applied to the pump, that is, when the discharge pressure of the working fluid discharged from the pump is low, so that no load is applied to the pump. The object of the present invention is to provide a variable displacement pump that reduces the required power when the pump is used.

Therefore, the present invention achieves the above object by providing a first control device +al and a second control device (bl, described below) so as to face each other across the guide ring (4) of the pump.

The first control device +a+ includes a first control hydraulic chamber (46) that receives the discharge pressure of the working fluid discharged from the pump chamber, and an auxiliary piston that is slidably housed in the 11iIII control hydraulic chamber in an oil-tight manner. (42), a loft member (43) that extends through the auxiliary piston and has an end surface that receives pressure from a first control hydraulic chamber, and a first spring (47) that is supported by the auxiliary piston. A first control piston (40) that abuts the guide ring by this first spring.
It is composed of. And, this first control device is
Control is performed to increase the distance between the centers of the rotating rotor 2 housed in the housing and the guide ring 4 provided on the outer periphery of the rotor, that is, the eccentricity (1111), in accordance with the discharge pressure from the pump.

The second control device (b) includes a second control hydraulic chamber (57) that receives the discharge pressure of the working fluid discharged from the pump chamber, and a second spring (56) housed and supported in the second control hydraulic chamber. ), receives the biasing force of the second spring, and receives the biasing force of the second spring.
It consists of a second control piston (50) having an end face that receives the pressure of the control hydraulic chamber. This second control device is
Control is performed to reduce the eccentricity (el) in accordance with the discharge pressure from the pump.

The pressure receiving end surface (S+) of the loft member (43) of the first control device (al) has a smaller area than the pressure receiving end surface (S2) of the second control piston (50) of the second control device (bl). .Furthermore, the spring constant (K
2) is set larger than the spring constant (K+) of the first spring (47).

(Example) Next, one embodiment of the present invention will be described based on the first drawing.

This embodiment is an embodiment in which a radial plunger pump, which is a variable displacement pump, is used as a hydraulic power source for a power steering device, and FIG. 1 is a partial sectional view of the radial plunger pump of the above-mentioned usage example.

2 is a housing that forms the outer shape of the pump, and 2 is a rotor that is built into the housing 1 and rotates around 0 in response to external power. The rotor 2 has seven cylinder holes 21 arranged radially.
A plunger 3, which is biased outward from the center 0 by a cylinder spring 22, is inserted into each of the plungers 1 in an oil-tight and slidable manner. Also, inside the rotor 2 is a pump chamber 2 formed by a cylinder hole 21 and a plunger 3.
The number of fluid passages 24 communicating with the plungers 3 is equal to the number of plungers. This fluid passage 24 communicates with the discharge port 11 by a switching valve (not shown) during a discharge stroke in which the plunger 3 provided on the rotor 2 is in the upper half of the rotation center 0 in FIG.

Further, during the suction stroke in which the plunger 3 is in the lower half of the rotation center O, it is communicated with the suction port 12 by a switching valve (not shown). Note that the suction port 12 communicates with the oil tank 100 to suck in oil for operation.

On the other hand, the outer circumference of the rotor 2 includes an inner ring 4a and an outer ring 4b.
, and steel balls 4c, the outer tip of the plunger 3 contacts the inner periphery of the inner ring 4a and rotates at approximately the same speed as the rotor 2. Further, the outer ring 4b is provided so as not to rotate in contact with the housing 1.

Here, O' is the center of the guide ring 4, which is provided eccentrically from the center 0 of the rotor 2 by an eccentric amount e.

In addition, the housing 1 on the right side of the guide ring 4 in the figure has
A first control device a is provided that controls the eccentricity e of the guide ring 4 to increase, and the first piston 4
0 is slidably inserted into the first insertion hole 13 of the housing 1. The outer ring 4b of the guide ring 4 rolls into contact with one end of the first piston 40.
1 is provided. Further, an introduction control hole 14 is provided on the right side of the first insertion hole 13, and an auxiliary piston 42 is inserted therein in an oil-tight manner and slidable therein. A stepped portion 15 is formed in the housing (2) between the first insertion hole 13 and the first control hole 14. This step part 1
5 serves as a stopper for the auxiliary piston 42. A ront piston 43, which is a rond member, is inserted into a hole provided in the center of the auxiliary piston 42. This long piston 43 is connected to a first control hydraulic chamber 46 which will be described below.
A pressure receiving end surface 43a is formed to receive the working hydraulic pressure.

A circlip 43b is provided at one end of the front piston 43 to prevent removal during assembly. A first nipple 44 having a first pressure introduction hole 44a in the center is screwed into one end of the first control hole 14 via a washer 45. Further, the space surrounded by the auxiliary piston 42 and the first nipple 44 forms a first IIJIII hydraulic chamber 46, and the discharge pressure of the working fluid is introduced into this first control hydraulic chamber 46 through a pilot communication passage 18a branched from the discharge port 11. It will be destroyed. The first spring 47 is supported by the auxiliary piston 42 and urges the first piston 40 to the left in the figure. Note that 91 is a drain hole that communicates with the oil tank 100.

On the other hand, a second control cylinder 51 of a second control device is press-fitted into the second insertion hole 16 of the housing 1 provided on the left side in the figure, and a second control piston 50 is inserted into the center hole of the control cylinder 51. is inserted so that it remains oil-tight and can slide freely. One end of the second control piston 50 has a pressure receiving end surface 50 that receives pressure from a second control hydraulic chamber 57, which will be described below.
a is formed. This pressure receiving end surface 57a has a larger area than the pressure receiving end surface 43a of the front piston 40 of the first control device a. Further, at the other end of the second control piston 50, a 20th rotor 52 is provided which is in rolling contact with the guide ring 4. Furthermore, a second
A second nipple 53 having a second pressure introduction hole 53a in the center is screwed into one end of the control hole 17 via a washer 54.

A second control hydraulic chamber 57 is formed by the second second sople 53 and the second control hole 17. This second control hydraulic chamber 57 is provided with a spring seat 55 and a second spring 56. This second spring 56 is supported by the second nipple 53 and urges the spring seat 55 to the right in the figure. Further, a pressure passage 55a is provided in the center of the spring seat 55, and the hydraulic pressure is guided to the pressure receiving end surface 57a of the second control piston 50 through this pressure passage 55a. Note that the discharge pressure of the working fluid is guided to the second control hydraulic chamber 57 via a communication path 18b branched from the discharge port 11.

The device provided on the left side of the figure described above is called a second control device. Further, the working fluid discharged from the discharge port 11 of the variable displacement pump described above is supplied to the power steering device through the discharge communication passage 18.

*This power steering device is steering 10.
11 control valve 102, power piston lO3
, a power cylinder 12o1 rack 105, and when the steering wheel 101 is rotated, the control valve 102 is operated, and which of the space 104 or the space 121 in the power cylinder 120 is connected to the discharge port 1.
It will be communicated with 1. At this time, the other space is structured to communicate with the oil tank 100. Further, when the working fluid is not supplied to the power cylinder 120, a passage is provided to drain the working fluid to the oil tank 100.

Next, the operation of the embodiment will be explained based on the above-described configuration.

FIGS. 2 to 4 are schematic diagrams of essential parts for explaining the operation, and FIGS. 5 and 6 are characteristic diagrams for explaining the operation.

First, the stepped portion 15 of the auxiliary piston 42 of the first control device a
The distance from the spring seat 55 of the second control device to the control cylinder 51 is a second distance X2. Further, the maximum eccentricity between the guide ring 4 in the housing 1 and the rotor is assumed to be e (m'ax).

FIG. 2 shows a state before the start of the pump or when the discharge pressure of the hydraulic oil discharged from the pump is at its lowest, that is, when the steering 101 of the power steering device is not operated.
Indicates that the pump is not under load. At this time, the pilot communication path 18a.

The first control hydraulic chamber 4 receives the pressure of hydraulic oil through 18b.
(6) The pressure in the second control hydraulic chamber 57 is low.

Therefore, the operating force generated by the first control device a is small, and the urging force of the second spring 56 of the second control device a is larger. Therefore, the spring seat 55 abuts against the control cylinder 51 .

The guide ring 4 is eccentric with respect to the center of the rotor 2 by half of the maximum eccentricity e(max), and the pump is operated at a discharge rate that is half of the maximum discharge rate. At this time, the first distance
+ is a distance determined by the free length of the first spring 47, for example, 1/2·e (max), and the second distance X2 is zero. This corresponds to point α in FIGS. 5 and 6.

Then, when the steering wheel 101 of the power steering device is operated from the above-mentioned state, a load is applied to the pump.
A case in which the discharge pressure P gradually increases will be explained.

At this time, the auxiliary piston 42, which has a relatively large area, starts to move downward in FIG. 2 under pressure from the first control hydraulic chamber 46. Along with this, the front piston 43 provided at the center of the auxiliary piston 42 also moves. Then, the set load of the first spring 47 increases, and the first control piston 40 receives the biasing force in the downward direction in FIG. When the load becomes larger than the set load, the first control piston 40 starts to move.In other words, the eccentricity increases from 1/2·e(max) to e(max), and the discharge amount Q of the pump increases.

Then, the auxiliary screw 42 moves until it comes into contact with the stepped portion 15. One end of the front piston 43 of the first control device a comes into contact with the first control piston 40 . At this time, as shown in FIG. 3, the eccentricity described above becomes maximum (e(max)), and the discharge amount Q from the pump also becomes maximum. At this time,
The first distance XI is zero, the second distance is 1/2・e(rnax
). This corresponds to point β in FIGS. 5 and 6, and for example, the pump discharge pressure at this time is about 5 kg/-.

Next, a case will be described in which the load is further applied to the pump and the discharge pressure increases to more than P (for example, P = about 75 kg/cra).

The discharge pressure from the pump is applied to both the first control device a and the second control device S, but the auxiliary piston 42 of the first control device a has a structure in which it cannot move after it comes into contact with the stepped portion 15. It becomes.

Therefore, the force acting on the guide ring 4 by the first control device a, that is, the force that increases the eccentricity e, is a combination of the constant biasing force from the first spring 47 and the acting force by the front piston 43 having the pressure receiving end surface 43a. It is the resultant force. However, the pressure receiving end surface 50a of the second control piston 50 of the second control device has a larger area than the pressure receiving end surface 43a of the front piston 43. Therefore, when the discharge pressure from the pump increases, the operating force of the second control piston 50, that is, the force that reduces the eccentricity e increases, and eventually becomes greater than the operating force of the first control device a.

Then, the second control piston 50 moves upward in FIG. 3 and begins control to reduce the eccentricity e.

This corresponds to one point in FIGS. 5 and 6. At this time, the long piston 43 projects from the auxiliary piston 42 into the first control hydraulic chamber 46 . Then, as the pump discharge pressure P increases, the eccentricity e and the discharge amount Q decrease. Finally, when the discharge pressure P reaches about 80 kg/c+a, the eccentricity e and the discharge amount Q become zero. This prevents damage to the pump, communication passage, etc. this is,
This corresponds to point ε in FIGS. 5 and 6.

In addition, in the above-mentioned embodiment, when no load is applied to the pump, the discharge amount of the pump is set to half of the maximum discharge amount; It is not limited to the amount, and can be adjusted by changing the dimensions of each component. Further, by changing the spring constant of each spring and the area of the pressure receiving end surface of each piston, the discharge pressure from the pump used as input to the above-mentioned control device can be arbitrarily set.

(Effects of the Invention) As described above, the present invention includes the first and second control devices that control the amount of eccentricity between the rotor and the guide ring provided in the housing, so that negative pressure is applied to the pump. When this is not the case, that is, when the discharge pressure of the working fluid discharged from the pump is low, the discharge amount from the pump can be set small.

Further, when a load exceeding a certain setting is applied to the pump, that is, when the discharge pressure of the working fluid discharged from the pump increases, the discharge amount of the pump can be changed to the maximum discharge amount.

This allows, depending on the load on the pump,
In other words, the discharge amount of the pump can be changed according to the discharge pressure of the working fluid discharged from the pump. Furthermore, since the first control device and the second control device have a simple structure and are integrally formed with the pump housing, they are highly reliable and cost effective. In addition, by changing each component of the first control device and the second control device, for example, by changing the spring constants of the first spring and the second spring, and the areas of the pressure receiving end surfaces of the long piston and the second control histon, the driving force can be changed. It is possible to easily provide a variable displacement pump with suitable characteristics as a hydraulic power source for the device.

[Brief explanation of the drawing]

FIG. F is a sectional view of a variable displacement pump showing an embodiment of the present invention, FIGS. 2 to 4 are schematic diagrams of essential parts for explaining the operation of an embodiment of the present invention, and FIG. FIG. 6 is a characteristic diagram showing the characteristics of the present invention and the conventional variable displacement pump. DESCRIPTION OF SYMBOLS 1... Housing, 2... Rotor, 4... Guide ring, 40... First control piston, 42... Auxiliary piston, 43... Rondo member (ronto piston),
46... First control hydraulic chamber, 47... First spring, 50... Second control piston, 56... Second spring, 57... Second control hydraulic chamber.

Claims (1)

[Claims] In a variable displacement pump, the volume of the pump chamber is changed by changing the amount of eccentricity between the rotating rotor built into the housing and the guide ring provided on the outer periphery of the rotor.
A first control hydraulic chamber and a second control hydraulic chamber are provided to face each other with a guide ring in between and receive the discharge pressure of the working fluid discharged from the pump chamber, and are slidable to the first control hydraulic chamber. an auxiliary piston housed in the auxiliary piston, a rond member that is slidably provided through the piston and has an end face that receives pressure from a first control hydraulic chamber, a first spring supported by the auxiliary piston, and the rond member. a first control piston that acts to increase eccentricity by a member and abuts the guide ring; and a first control piston that has an end surface having a larger pressure receiving area than the end surface of the rond member, and that controls the hydraulic pressure of the second control hydraulic chamber. a second control piston that receives and slides thereon and acts to reduce the amount of eccentricity; and a second control piston that has a larger biasing force than the first spring and biases the second control piston to contact the guide ring. A variable displacement pump characterized by comprising two springs.