JP2003083265A - Variable displacement type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a minimum flow required for urgent avoidance without reducing saving efficiency of energy consumption in a variable displacement type pump. SOLUTION: A cam ring 21 of a vane pump is radially movably disposed in an adapter 13. An inner pressure and a load presser before and after a variable orifice 54, introduced into acting chambers 51a, 51b, arranged on both sides are controlled by the differential pressure control valve 31, so that discharged flow is controlled by responding to a pump rotation speed. The differential pressure control valve is operated by the inner pressure and the load pressure introduced to the acting chambers 52a, 52b formed at both end sides, and a valve pressing spring 33 energizing the differential control valve to the inner pressure acting chamber 52a side. The energizing force by the valve pressing spring is increased and decreased depending on increase and decrease in the load pressure. The differential control valve introduces the load pressure to a second acting chamber, when a differential pressure before and after the variable orifice 54 is small. When the differential pressure is increased, communication between the second acting chamber and the portion where the load pressure is produced is closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement pump suitable for use in a vehicle power steering device and the like, and in particular, to a variable displacement pump provided with a vane pump portion having a rotor rotating in a cam ring and provided in a discharge passage. The present invention relates to a variable displacement pump in which the eccentricity of a cam ring with respect to a rotor is changed according to the pressure difference across an orifice to control the pump discharge flow rate characteristic.

[0002]

2. Description of the Related Art As such a variable displacement pump,
There is a technique disclosed in Japanese Patent No. 2932236 (see Japanese Patent Laid-Open No. 7-243385). This forms the first and second fluid pressure chambers between the cam ring and the pump body that are arranged so that the eccentric amount with respect to the rotor is variable, and urges the cam ring in the direction in which the pump displacement is maximized. A spool type control valve for controlling the fluid pressure supplied to the first fluid pressure chamber according to the differential pressure across the orifice provided in the pump discharge side passage is provided to give a displacement displacement in the direction that maximizes the pump capacity. The fluid pressure on the rear side of the orifice, which is guided to the second chamber at one end of the control valve, is introduced into the second fluid pressure chamber. In this conventional technique, the fluid pressure on the front side of the orifice (pump internal pressure, hereinafter simply referred to as internal pressure) is applied to the first chamber at the other end of the spool type control valve.
Is introduced, and when the control valve is pressed against the first chamber side at a low pump rotation speed, the cam ring is introduced by introducing a low pressure (= atmospheric pressure) continuous with the reservoir into the first fluid pressure chamber. Eccentricity of the cam ring by introducing the internal pressure on the front side of the orifice into the first fluid pressure chamber when the control valve moves to the second chamber side due to the increase of the pump displacement by maximizing the eccentricity of the pump valve. The volume is reduced to reduce the pump capacity.

The characteristic of the discharge flow rate with respect to the rotational speed of the variable displacement pump according to this Japanese Patent No. 2932236 increases proportionally as shown by the characteristic A of FIG. 5 up to a certain rotational speed, and at the rotational speeds higher than that, the characteristic increases. It becomes constant as shown in D. There is a variable displacement pump of this type in which the orifice provided in the pump discharge side passage is a variable orifice whose opening area decreases as the eccentricity of the cam ring decreases. The characteristic of the discharge flow rate in (1) has a speed sensitive function that gradually decreases as the rotation speed increases, as shown by the characteristic D1 in FIG.

Further, a load pressure sensitive function for reducing the degree of decrease of the eccentricity of the cam ring according to the increase of the load pressure given by the operating state of the equipment to which the working fluid is supplied such as the power steering device ( For example, see Japanese Examined Patent Publication No. 2-61638), and in this way, the characteristics shown by D and D1 when the load pressure is high are reduced when the load pressure is reduced (without steering). The characteristic is as shown by E1.

In the vehicle power steering system, a large steering assist force is required when the vehicle is stopped or traveling at a low speed, but the steering assist force becomes small during a high-speed traveling, and the load is increased when the steering assist force is not required during straight traveling. The pressure drops. Therefore, according to the variable displacement pump having the speed sensitive function and the load pressure sensitive function as described above, the discharge flow rate of the working fluid is reduced unless the working fluid needs to be supplied to the power steering device. Energy consumption by the variable displacement pump can be reduced.

[0006]

As described above, the pump discharge flow rate for giving the steering assist force is not essentially required during high speed traveling, but it is not possible to secure the predetermined minimum flow rate Qmin in preparation for steering for emergency avoidance. is necessary. However, in the variable displacement pump having the speed-sensing function of the above-mentioned prior art, the characteristic D1 becomes the minimum flow rate Qmin at the predetermined set rotation speed NE in the straight running state, and the predetermined gradient even if the set rotation speed NE is exceeded. Therefore, the discharge flow rate is excessively reduced by interrupting the minimum flow rate Qmin in a high-speed straight running state on a highway where the pump rotation speed increases. If steering is performed for emergency avoidance in such a state, the steering wheel torque becomes heavy.

As a means for avoiding this, the discharge flow rate characteristic D
It is conceivable to change 1 to D2, but this is not preferable because the effect of saving energy consumption in the variable displacement pump decreases. The present invention aims to solve such problems.

[0008]

SUMMARY OF THE INVENTION A variable displacement pump according to the present invention comprises a cam ring rotatably mounted in a housing, and a cam ring rotatably supported by the housing and sliding on an inner surface of the cam ring. A rotor for movably holding a plurality of vanes abutting against each other in a radial direction, an intake port and a discharge port formed in a housing or a member fixed to the housing, and an outer periphery of the cam ring, which face each other in the moving direction of the cam ring. The first working chamber and the second working chamber formed by the above, the cam pressing means that elastically biases the cam ring toward the first working chamber where the eccentric amount with respect to the rotor is maximum, and the discharge port communicates with the discharge port. Inside the housing and a variable orifice which is provided in the middle of the discharge passage and whose opening area decreases as the cam ring moves to the second working chamber side. The is moved by the pressure difference before and after the variable orifice provided to be axially moved first and second
In a variable displacement pump provided with a differential pressure control valve for controlling each pressure acting on the working chamber, the differential pressure control valve is a load on the second working chamber behind the variable orifice when the differential pressure before and after the variable orifice is small. When the pressure is introduced and the differential pressure before and after the variable orifice increases, the communication between the second working chamber and the portion where the load pressure is generated is closed.

The variable displacement pump according to the present invention is
A cam ring movably provided in the housing in a radial direction, and a rotor rotatably holding a plurality of vanes rotatably supported by the housing in the cam ring and slidably abutting an inner surface of the cam ring. A first action chamber and a second action formed between the suction port and the discharge port formed in the housing or a member fixed to the housing, and between the outer periphery of the cam ring and the housing so as to face each other in the moving direction of the cam ring. A chamber, a cam pressing means for elastically urging the cam ring toward the first working chamber where the eccentricity with respect to the rotor is maximum, and a cam ring provided in the middle of the discharge passage communicating the discharge port with the discharge port. A variable orifice whose opening area decreases as it moves to the working chamber side, and a valve orifice formed in the housing that is axially movable. Be equipped with a differential pressure control valve, which,
The internal pressure acting on the front side and the load pressure acting on the rear side of the variable orifice of the discharge passage are introduced into the internal pressure action chamber and the load pressure action chamber formed between both ends of the differential pressure control valve and the housing, respectively. In the variable displacement pump, the differential pressure control valve introduces a predetermined low pressure or a pressure reduced from the internal pressure into the first working chamber when the differential pressure before and after the variable orifice is small and is pressed against the inner pressure working chamber side. A portion in which the load pressure is introduced into the second working chamber, and when the differential pressure increases and moves to the load pressure working chamber side, the inner pressure is introduced into the first working chamber and the load pressure occurs with the second working chamber. It is characterized in that the communication with and is closed.

The variable displacement pump according to the present invention is preferably constructed so that the elastic pressing force for urging the differential pressure control valve in the direction against the differential pressure increases in accordance with the increase in the load pressure.

In the variable displacement pump according to the present invention, a valve pressing spring for urging the differential pressure control valve toward the internal pressure working chamber and a housing slidably fitted and supported by the housing are projected into the internal pressure working chamber. Further, a load pressure sensitive piston whose tip portion can come into contact with one end of the differential pressure control valve from the axial direction, and a piston pressing spring for urging the load pressure sensitive piston toward the differential pressure control valve,
It is preferable that the elastic pressing force that urges the differential pressure control valve toward the inner pressure action chamber side is a difference between the elastic pressing force of the valve pressing spring and the elastic pressing force of the piston pressing spring.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The variable displacement pump according to the present invention will be described with reference to the embodiments shown in FIGS. The variable displacement pump of this embodiment is used as a working fluid supply source of a power steering apparatus, and has an end cover 11
Housing 10 that is liquid-tightly covered by
Of the vane pump portion 20 having the rotor 22 and the cam ring 21 movable in the radial direction, which are rotatably driven by the pump shaft 26, the differential pressure control valve 31 for controlling the movement of the cam ring 21, and the vane pump portion 20. A variable orifice 54 provided in the middle of the discharge passages 53a, 53b, 53c is a main constituent member.

As shown in FIGS. 1 and 2, an intermediate portion and a rear end portion of a pump shaft 26 are rotatably supported by a housing 10 and an end cover 11 fixed to the housing 10 by means of bearings. ing. A cylindrical inner surface 10a formed on the housing 10 coaxially with the pump shaft 26.
The disk-shaped side plate 12 on the back side and the cylindrical adapter 13 on the front side are fitted and supported so as not to rotate, and are disposed between the end cover 11, the side plate 12, and the adapter 13. Is provided with a vane pump section 20 described below. A V-pulley 29 to which the power from the engine is transmitted is fixed to the tip of the pump shaft 26 protruding from the housing 10.

The vane pump portion 20 includes a cam ring 21 provided in the adapter 13, a rotor 22 coaxially spline-coupled to an intermediate portion of a pump shaft 26, and a rotor 2.
2 includes a vane 23 slidably held by a plurality of radial slits and constantly abutting on the cylindrical inner surface of the cam ring 21, and the side surfaces of each of the members 21 to 23 have end covers 11 and It is slidably abutted on the end surface of the side plate 12. The intake port 24 of the vane pump unit 20 is formed on the end surface of the end cover 11,
The working fluid from the reservoir 61 is supplied through the suction passage 14 and the suction port 15. Further, the discharge port 25 is formed on the end surface of the side plate 12, and discharge passages 53a, 53b, 53c in which a variable orifice 54, which will be described later, is provided on the way from the pressure chamber 16 located on the back side, and the through hole 3
It is led to the discharge port 55 through 4a.

The pin 17, which is provided in parallel with the pump shaft 26 and whose both ends are supported by the end cover 11 and the side plate 12, is engaged with the inner surface of the adapter 13 at a part of the outer periphery of the intermediate portion. The cam ring 21 is movable in the radial direction of the cam ring 21 when a recess 21a formed in a part of the outer peripheral surface is engaged with the pin 17 and swings around the pin 17, and the recess is formed on the outer peripheral surface of the cam ring 21. 21
The portion on the side opposite to a is slidably sealed by a Teflon (registered trademark) seal member 50 provided in a groove formed on the inner surface of the adapter 13 and backed up by rubber. The space between the adapter 13 and the cam ring 21 is partitioned by the pin 17 and the seal member 50 to form a first working chamber 51a and a second working chamber 51b that face each other in the moving direction of the cam ring 21. A plug 18 directed toward the pump shaft 26 is screwed and fixed to the housing 10 on the side of the second action chamber 51b in the moving direction of the cam ring 21, and a cam portion is axially slidably pressed onto a cylindrical portion 18a of the plug 18. Piston 27
Are fitted and are urged toward the pump shaft 26 by the cam pressing spring 28. This cam pressing piston 27
The projection 27a at the tip of the through hole slidably and slidably passes through the adapter 13 and contacts the outer peripheral surface of the cam ring 21, and elastically moves the cam ring 21 toward the first working chamber 51a where the eccentric amount with respect to the rotor 22 is maximum. I am biased.

The variable orifice 54 includes a communication hole 18b formed in the cylindrical portion 18a of the plug 18 and the cam pressing piston 2.
7 and a fixed orifice 27b provided in the cam pressing piston 27. Cam ring 21 is second
As the cam pressing piston 27 moves toward the action chamber 51b side and retracts against the cam pressing spring 28, the communication hole 18b is gradually closed by the trailing edge of the cam pressing piston 27 so that the opening area thereof is reduced. It has become. The communication hole 18b that forms the variable orifice 54 has a smaller diameter than the conventional conventional one, and the diameter of the fixed orifice 27b is increased by making the communication hole 18b smaller than the conventional one, so that the flow resistance of the variable orifice 54 when fully opened is conventionally. I am trying to be the same as that of the one. The working fluid from the vane pump unit 20 is discharged from the discharge passages 53a and 53b through the variable orifice 54.
The liquid is discharged from the discharge port 55 through (including the fixed orifice 27b), the discharge passage 53c and the conduction hole 34a.

When the variable displacement pump is operating and the working fluid is flowing, the pressure drops before and after the variable orifice 54 to generate a differential pressure, and the discharge passage 53c and the communicating hole on the rear side of the variable orifice 54. The pressure in 34a and the discharge port 55 is a load pressure given by the operating state of the equipment to which the working fluid is supplied, and the discharge passage 5 on the front side of the variable orifice 54.
The pressure inside 3a, 53b and the pressure chamber 16 is the internal pressure of the pump. This internal pressure is larger than the load pressure by the amount of the differential pressure generated before and after passing through the variable orifice 54. Therefore, if the load pressure changes, the internal pressure also changes in the same manner.

As shown mainly in FIG. 1, the pump shaft 26
A spool-shaped differential pressure control valve 31 is inserted into the valve hole 30 formed in the housing 10 so as to be three-dimensionally orthogonal to the valve hole 30 from one direction on the left side in the drawing, and is fitted so as to be movable in the axial direction. The union 34 is screwed and fixed to the insertion side of the 30, and working chambers 52a and 52b are formed between both ends of the differential pressure control valve 31 and the housing 10, respectively. The union 34 is formed with a discharge port 55 and a conduction hole 34a for guiding the discharge port 55 to the discharge passages 53a, 53b, 53c. The working chamber 52a opposite to the union 34 is an inner pressure working chamber, and the inner pressure in the pressure chamber 16 is always introduced through the pump inner pressure introducing passage 56. The working chamber 52b on the side of the union 34 is a load pressure working chamber, and the discharge port 55
The internal load pressure is always introduced through the throttle communication hole 59. The differential pressure control valve 31 has a valve pressing spring 33 interposed between the differential pressure control valve 31 and the union 34, so
It is biased toward the 2a side.

The housing 10 on the side of the internal pressure action chamber 52a.
The inlet passage 57a formed in a part of the differential pressure control valve 31
The movement of the first action chamber 51a selectively communicates the first action chamber 51a with the reservoir 61 and the inner pressure action chamber 52a. The introduction passage 57a is provided in the internal pressure action chamber 52 when the differential pressure control valve 31 is pressed to the end position on the internal pressure action chamber 52a side by the valve pressing spring 33 (see FIG. 1).
Although it is not communicated with a, the differential pressure control valve 31 is opened to the valve hole 30 at a position where it communicates with the internal pressure action chamber 52a as soon as the differential pressure control valve 31 begins to move toward the load pressure action chamber 52b side against the valve pressing spring 33. The introduction passage 57a is communicated with the first working chamber 51a on the outer peripheral side of the cam ring 21 via a damping orifice 58a formed in the adapter 13. Further, the communication passage 32 formed in the differential pressure control valve 31 is communicated with the introduction passage 57a in a state where the introduction passage 57a is not communicated with the internal pressure action chamber 52a, but the differential pressure control valve 31 is connected with the load pressure action chamber 52b. As soon as the introduction passage 57a starts moving to the side and the introduction passage 57a communicates with the internal pressure action chamber 52a, the introduction passage 57a is no longer communicated with. The communication passage 32 is always communicated with the reservoir 61 via the communication conduit 60.

Housing 1 on the side of load pressure acting chamber 52b
The load pressure introducing passage 57b formed in a part of 0 has a valve hole 30 at a position opened and closed by the movement of the differential pressure control valve 31.
It is open to. The load pressure introducing passage 57b communicates with the load pressure acting chamber 52b in an inoperative state where the differential pressure control valve 31 is pressed to the end position on the inner pressure acting chamber 52a side by the valve pressing spring 33, and the differential pressure control valve 31b is connected. Is opened to the valve hole 30 at a position where it is closed by moving to the load pressure acting chamber 52b side against the valve pressing spring 33 to some extent, and the load pressure introducing passage 57b is formed through the damping orifice 58b formed in the adapter 13. The outer periphery of the cam ring 21 communicates with the second working chamber 51b on the other side. Further, in the differential pressure control valve 31, when the load pressure excessively increases, the pressure in the load pressure action chamber 52b is relieved to the reservoir 61, and the differential pressure control valve 31 is moved to the load pressure action chamber 52b side. A pilot relief valve 65 that minimizes the pump discharge flow rate is provided.

The housing 10 on the side of the internal pressure action chamber 52a.
A load pressure sensitive piston 40 having a diameter smaller than that of the differential pressure control valve 31 is fitted and supported coaxially with the valve hole 30 so as to be fluid-tight and slidable, and a load pressure capable of appearing and retracting in the internal pressure action chamber 52a. The tip of the sensitive piston 40 can come into contact with one end of the differential pressure control valve 31 in the axial direction. A piston pressing spring 41 is interposed between the spring receiving member 40a fixed to the other end of the load pressure sensitive piston 40 penetrating the housing 10 and the plug 19 screwed and fixed to the housing 10, and the pressure in the internal pressure action chamber 52a is increased. Is lower than a predetermined value, the load pressure sensitive piston 40 urged by the piston pressing spring 41 contacts one end of the differential pressure control valve 31 and urges it toward the load pressure action chamber 52b. The pressing force of the piston pressing spring 41 is set to be smaller than the pressing force of the valve pressing spring 33.

The differential pressure control valve 31 is directed toward the internal pressure action chamber 52a side against the leftward force applied to the differential pressure control valve 31 by the differential pressure between the internal pressure acting on each of the action chambers 52a and 52b and the load pressure. The elastic pressing force biased by the force is the difference between the force applied by the valve pressing spring 33 and the force applied by the piston pressing spring 41 via the load pressure sensitive piston 40. Valve pressing spring 3
The force given by 3 is not influenced by the internal pressure and the load pressure. The force applied by the piston pressing spring 41 via the load pressure sensitive piston 40 is the force applied by the piston pressing spring 41 when the internal pressure is zero. However, the load pressure sensitive piston 40 generates a force against the piston pressing spring 41 when the internal pressure in the internal pressure action chamber 52a rises, and when the internal pressure becomes a predetermined pressure or more, the tip of the load pressure sensitive piston 40 has a differential pressure control valve. Apart from 31, the force exerted by the piston pressing spring 41 via the load pressure sensitive piston 40 becomes zero. Therefore, the differential pressure control valve 31 is urged toward the internal pressure action chamber 52a side against the leftward force applied to the differential pressure control valve 31 by the differential pressure between the internal pressure acting on each of the action chambers 52a and 52b and the load pressure. The elastic pressing force to be applied increases as the load pressure increases. As a result, the variable displacement pump is provided with a load pressure sensitive function of changing the eccentric amount of the cam ring 21 by changing the stroke position of the differential pressure control valve 31 according to the load pressure.

If the rotation of the engine of the vehicle is transmitted to the pump shaft 26 via the drive belt wound around the V pulley 29 and the rotor 22 of the vane pump 20 is rotated, the reservoir 6
The working fluid in the vane 1 passes through the suction port 15 and the suction passage 14 through the suction port 24 and each vane 2 of the vane pump unit 20.
3 is sucked into the pump operation chamber, discharged from the discharge port 25 into the pressure chamber 16, and discharged from the discharge port 55 through the discharge passages 53a, 53b, 53c provided with the variable orifice 54 and the conduction hole 34a. It is supplied to equipment such as power steering devices.

First, consider a case where the steering wheel is not operated and the load pressure is low. When the pump rotation speed is low, the flow rate through the discharge passages 53a, 53b, 53c is small, and therefore the differential pressure before and after the variable orifice 54 is small, so that the differential pressure control valve 31 is as shown in FIGS. 1 and 4 (a). The valve pressing spring 33 and the piston pressing spring 41.
It is pressed against the inner pressure acting chamber 52a side end position by the force due to the difference in spring force. In this state, a predetermined low pressure (usually atmospheric pressure) in the reservoir 61 is introduced into the first working chamber 51a through the introduction passage 57a and the communication passage 32, and the second working chamber 5
1b is connected to the load pressure acting chamber 52 via a load pressure introducing passage 57b.
Since the load pressure in b is introduced, the cam ring 21 is reliably pressed by the cam pressing spring 28 to the side of the first action chamber 51a where the discharge flow rate is the maximum, and is not separated. In this state, the discharge passages 53a, 53
The discharge flow rate of the working fluid discharged from the discharge port 55 through the b, 53c and the conduction hole 34a rapidly increases as the pump rotation speed increases, as indicated by the characteristic A in FIG.

If the discharge flow rate increases due to the increase in the pump rotation speed and the differential pressure before and after the variable orifice 54 increases, the differential pressure between the internal pressure in the internal pressure action chamber 52a and the load pressure in the load pressure action chamber 52b increases. The control valve 31 is connected to the load pressure action chamber 52
The force to move to the b side also increases. When this force exceeds the force due to the difference between the spring forces of the two springs 33 and 41, the differential pressure control valve 31 begins to move to the load pressure action chamber 52b side, and first, the internal pressure action chamber 52a and the introduction path 57a communicate with each other. The internal pressure in the internal pressure action chamber 52a is introduced into the first action chamber 51a. On the other hand, since the load pressure in the load pressure action chamber 52b is still introduced to the second action chamber 51b,
The cam ring 21 moves to the second working chamber 51b side against the cam pressing spring 28 due to the pressure difference between the internal pressure and the load pressure in the two working chambers 51a and 51b, and the eccentric amount with respect to the rotor 22 starts to decrease. As mentioned above, the variable orifice 54
The diameter of the communication hole 18b that forms the opening is smaller than that of the conventional one. Therefore, as the eccentricity of the cam ring 21 decreases, the opening area of the variable orifice 54 decreases more rapidly than in the related art. The flow rate sharply decreases as compared with the conventional characteristic D1 as shown by the characteristic B in FIG.

If the discharge flow rate increases due to the increase of the pump rotation speed and the differential pressure before and after the variable orifice 54 increases, the differential pressure control valve 31 moves further to the load pressure action chamber 52b side, as shown in FIG. 4 (b). When reaching the position shown, the opening of the load pressure introducing passage 57b to the valve hole 30 is closed, and the second working chamber 5
Introduction of the load pressure in the load pressure action chamber 52b to 1b is stopped. After this, as shown in FIG. 4 (c), the opening of the load pressure introducing passage 57b with respect to the valve hole 30 remains closed. Therefore, in the state where the rotational speed NS corresponding to the position shown in FIG. 4 (b) is exceeded. The pump discharge flow rate slightly decreases as the pump rotation speed increases, as indicated by the characteristic C in FIG. The discharge flow rate decreases despite the fact that the load pressure introducing passage 57b is closed because the working fluid from the gap between the valve hole 30 and the differential pressure control valve 31 is more than the increase in the pump discharge flow rate due to the increase in the pump rotation speed. This is because the leakage flow rate of

When the load pressure is increased by operating the handle or the like, the internal pressure in the internal pressure action chamber 52a is also increased, and this is applied to the load pressure sensitive piston 40, so that the spring force of the piston pressing spring 41 is offset. The elastic pressing force that presses the pressure control valve 31 to the end position on the inner pressure action chamber 52a side increases. Therefore, when the differential pressure control valve 31 starts to move to the load pressure action chamber 52b side, the first action chamber 5
The differential pressure before and after the variable orifice 54 increases when the internal pressure in the internal pressure action chamber 52a begins to be introduced into the valve 1a and when the opening of the load pressure introducing passage 57b with respect to the valve hole 30 is closed. The pump discharge flow rate also increases. That is, the characteristics when the load pressure increases are the characteristics B and C when the load pressure is low, which are moved to the higher pump discharge flow rate. There is a limit to the movement to the higher side, and the load pressure sensitive piston 40
Is increased and the distance from the tip of the differential pressure control valve 31 is increased, which is the limit of movement to the higher side.

According to the above-described embodiment, the differential pressure before and after the variable orifice 54 is small, and the differential pressure control valve 31 closes the communication between the second working chamber 51b and the load pressure working chamber 52b in which the load pressure is generated. The variable orifice 5 is provided in the first working chamber 51a and the second working chamber 51b when the variable orifice 5 is not provided.
Since the differential pressure before and after 4 is applied as it is, the pump discharge flow rate decreases with a relatively large gradient as shown in the characteristic B of FIG. 3 as the pump rotation speed increases, and the differential pressure before and after the variable orifice 54 increases. Second working chamber 51b and load pressure working chamber 52
After the communication with b is closed, the gradient of the decrease of the pump discharge flow rate with the increase of the pump rotation speed becomes small as shown by the characteristic C in FIG. As described above, as the pump rotation speed increases, the pump discharge flow rate decreases first with a relatively large gradient and then with a slight gradient. Therefore, the position of the set rotation speed NE at which the pump discharge flow rate becomes the minimum flow rate Qmin is the second action. The slope after the communication between the chamber 51b and the load pressure action chamber 52b is closed can be small.

As a result, the degree of decrease of the discharge flow rate in the state of exceeding the set rotational speed NE is reduced, and the discharge flow rate does not excessively decrease even in the high speed traveling state in which the pump rotational speed increases, so that the vehicle travels straight at high speed. It is possible to handle steering for emergency avoidance even when the vehicle is in a state of being operated.
Further, since the discharge flow rate in the state of less than the set rotational speed NE does not increase more than the minimum flow rate Qmin, the energy consumption of the variable displacement pump does not increase.

In the above-described embodiment, when the differential pressure control valve 31 is pressed against the inner pressure action chamber 52a side end position (see FIGS. 1 and 4 (a)), the first action chamber 51a does not move. Is introduced into the reservoir 61 via the introduction passage 57a and the communication passage 32, and the load pressure in the load pressure action chamber 52b is introduced into the second action chamber 51b via the load pressure introduction passage 57b. Therefore, the cam ring 21 is surely pressed by the cam pressing spring 28 toward the first working chamber 51a side where the discharge flow rate is maximum, and is not separated.
However, the present invention is not limited to this, and the differential pressure control valve 3
In the inoperative state of No. 1, the introduction passage 57a is communicated with both the internal pressure action chamber 52a and the communication passage 32 via the variable throttle, whereby the internal pressure in the internal pressure action chamber 52a is changed to the first action chamber 51a instead of the atmospheric pressure. May be carried out by introducing a reduced pressure.

Further, in the above-described embodiment, the differential pressure control valve urged in the axial direction by the valve pressing spring 33 in order to provide the load pressure sensitive function of changing the eccentric amount of the cam ring 21 according to the load pressure. 31 through a load pressure sensitive piston 40 and a piston pressing spring 41.
The differential pressure control valve 3
Although the elastic pressing force for urging 1 is changed according to the increase of the load pressure, the present invention is not limited to this, and the spool for receiving the opposite side of the differential pressure control valve 31 of the valve pressing spring 33. The load pressure sensitive function may be realized by a structure in which the element moves according to the load pressure.

[0032]

As described above, according to the present invention, first, the differential pressure before and after the variable orifice is small, and the communication between the second working chamber and the portion where the load pressure is generated is closed by the differential pressure control valve. In the absence of pressure, the differential pressure before and after the variable orifice is applied to the first and second working chambers, so the pump discharge flow rate decreases with a relatively large gradient as the pump rotation speed increases, and the differential pressure before and after the variable orifice increases. After the differential pressure control valve closes the communication between the second working chamber and the part where the load pressure is generated, the gradient of the decrease in the pump discharge flow rate according to the increase in the pump rotation speed becomes slight. In this way, as the pump rotation speed increases, the pump discharge flow rate first decreases with a relatively large gradient and then decreases slightly. It can be a small part. As a result, the degree of decrease in the discharge flow rate in the state of exceeding the set rotation speed is reduced, and the discharge flow rate does not decrease excessively even in the high-speed traveling state where the pump rotation speed increases. However, it is possible to handle steering for emergency avoidance. Further, since the discharge flow rate in the state below the set rotational speed does not increase much more than the minimum flow rate, the energy consumption of the variable displacement pump does not increase.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall structure of an embodiment of a variable displacement pump according to the present invention.

2 is a sectional view taken along line 2-2 of FIG.

3 is a diagram showing pump discharge flow rate characteristics of the variable displacement pump according to the embodiment shown in FIG.

FIG. 4 is a partial cross-sectional view illustrating an operating state of the embodiment shown in FIG.

FIG. 5 is a diagram showing an example of pump discharge flow rate characteristics of a variable displacement pump according to a conventional technique.

[Explanation of symbols]

10 ... Housing, 21 ... Cam ring, 22 ... Rotor,
23 ... Vane, 24 ... Suction port, 25 ... Discharge port,
28 ... Cam pressing means (cam pressing spring), 30 ...
Valve hole, 31 ... Differential pressure control valve, 33 ... Valve pressing spring, 40 ... Load pressure sensitive piston, 41 ... Piston pressing spring, 51a ... First working chamber, 51b ... Second working chamber, 52a ... Internal pressure working chamber , 52b ... Load pressure acting chamber, 5
3a, 53b, 53c ... Discharge passage, 54 ... Variable orifice, 55 ... Discharge port.

Claims (4)

[Claims] 1. A cam ring radially movably provided in a housing, and a plurality of vanes rotatably supported by the housing in the cam ring and slidably abutting an inner surface of the cam ring Rotatably held, a suction port and a discharge port formed on the housing or a member fixed thereto, a first working chamber formed on the outer periphery of the cam ring so as to face each other in the moving direction of the cam ring, A second working chamber, and a cam pressing unit that elastically biases the cam ring toward the first working chamber where the amount of eccentricity with respect to the rotor is maximum,
A variable orifice that is provided in the middle of a discharge passage that communicates the discharge port with the discharge port and has an opening area that decreases as the cam ring moves toward the second working chamber; and a variable orifice that is axially movable in the housing. The first and second movable members are moved by the pressure difference across the variable orifice.
In a variable displacement pump including a differential pressure control valve for controlling each pressure acting on the working chamber, the differential pressure control valve includes the variable orifice in the second working chamber when the differential pressure before and after the variable orifice is small. A variable displacement type characterized in that the communication between the second working chamber and the portion where the load pressure is generated is closed when a rear load pressure is introduced and the differential pressure across the variable orifice increases. pump. 2. A cam ring provided in a housing so as to be movable in a radial direction, and a plurality of vanes that are rotatably supported by the housing in the cam ring and that slidably abut the inner surface of the cam ring are moved in a radial direction. A rotor that holds the cam ring, a suction port and a discharge port formed in the housing or a member fixed to the housing, and an outer periphery of the cam ring and the housing that are formed to face each other in the moving direction of the cam ring. A first working chamber and a second working chamber, a cam pressing unit that elastically biases the cam ring toward the first working chamber where the eccentric amount with respect to the rotor is maximum, and the discharge port communicates with the discharge port. A variable orifice which is provided in the middle of the discharge passage and whose opening area decreases as the cam ring moves toward the second working chamber side. A differential pressure control valve fitted in a valve hole formed in the housing so as to be movable in the axial direction, and an internal pressure action chamber and a load formed between both ends of the differential pressure control valve and the housing. In a variable displacement pump in which an internal pressure, which is a pressure on the front side of the variable orifice of the discharge passage, and a load pressure, which is a pressure on the rear side thereof, are introduced into the pressure action chamber, the differential pressure control valve includes: When the differential pressure is small and the pressure is pressed toward the inner pressure working chamber side, a predetermined low pressure or a pressure obtained by reducing the inner pressure is introduced into the first working chamber and the load pressure is introduced into the second working chamber. If the differential pressure increases and moves to the load pressure action chamber side, the internal pressure is introduced into the first action chamber and the communication between the second action chamber and the portion where the load pressure is generated is closed. Variable displacement pump, characterized in that the so that configuration. 3. The variable displacement pump according to claim 1 or 2, wherein an elastic pressing force for urging the differential pressure control valve in a direction against the differential pressure responds to an increase in the load pressure. A variable displacement pump characterized in that it is configured to increase. 4. The variable displacement pump according to claim 2, wherein a valve pressing spring that biases the differential pressure control valve toward the internal pressure action chamber side and a slidably fitted support to the housing. A load pressure sensitive piston whose tip portion projecting into the internal pressure acting chamber can abut one end of the differential pressure control valve in the axial direction; and a piston for urging the load pressure sensitive piston toward the differential pressure control valve. An elastic pressing force for further urging the differential pressure control valve toward the internal pressure action chamber is provided with a pressing spring, and an elastic pressing force by the valve pressing spring and an elastic pressing force by the piston pressing spring are provided. Variable displacement pump.