JPH0914155A - Variable capacity oil pump - Google Patents

Abstract

(57) [Summary] [Purpose] To eliminate the fluctuation of hydraulic pressure of hydraulic oil in the working space,
(EN) Provided is a variable displacement oil pump capable of preventing a driver from feeling uncomfortable due to pulsation caused by fluctuations in hydraulic pressure. In a variable displacement oil pump capable of variably controlling the discharge amount of hydraulic oil to be discharged, a working space 19 for the hydraulic oil is provided.
The suction portion 1 through which the hydraulic oil is sucked from the suction port 24.
91, the cutoff portion 19 which is a section for transporting the hydraulic oil sucked from the suction portion 191 to the discharge port 25 and pre-compressing it.
2. Discharge portion 19 from which hydraulic oil is discharged from the discharge port 25
3, a closing portion 19 that connects the discharge portion 193 and the suction portion 191
The variable displacement oil pump is characterized in that the space of the shutoff portion 192 and the closing portion 194 is a space surrounded by concentric circles with the rotation center of the rotor 17 as the center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle hydraulic drive system pump for pumping hydraulic fluid to hydraulic equipment (power steering, hydraulic motor, etc.) provided in a vehicle, and particularly to the amount of hydraulic fluid to be pumped. The present invention relates to a variable capacity oil pump capable of variably controlling the oil.

[0002]

2. Description of the Related Art A vehicle is equipped with a large number of devices (power steering, hydraulic motor, etc.) which are normally operated by hydraulic pressure. Naturally, an oil pump for sending hydraulic oil to these hydraulically operated devices is also required. In addition, the hydraulic motor that drives the fan that cools the radiator must control the number of revolutions according to the temperature of the cooling water that flows in the radiator, so the amount of hydraulic oil supplied to this hydraulic motor must also be variably controllable. I won't. FIG. 5 shows a conventional variable displacement oil pump that satisfies these requirements.

The variable capacity oil pump 50 includes a body 5
1 and a rotor 52 arranged in the body 51 and transmitted by a belt (not shown) to rotate the crankshaft (not shown), and an operating space 53 is formed between the rotor 52 and the rotor 52. Installed and body 51
A cam ring 55 which is swingable around a pin 54 fixed to the fulcrum and is eccentric with respect to the rotor 52, a suction port 56 for sucking the working oil into the working space, and a discharge port for discharging the working oil to the outside. A discharge port 57 and a cam ring swinging device 58 that swings the cam ring 55 are provided.

The cam ring swinging device 58 includes a body 51.
And a cylinder 581 integrally formed with the cylinder 58.
Of the cam ring 55 and the control piston 582 which is slidably disposed in the first ring 1 and biases the protrusion 551 serving as the point of action formed on the cam ring 55 in the direction (the right direction in the drawing) that reduces the eccentric amount of the cam ring 55. The protrusion 551 of the cam ring 55 extends in the direction of increasing the eccentricity (leftward in the drawing).
And a return spring 583 that biases the.

The left end of the control piston 582 is a pressure receiving surface 582a for receiving hydraulic pressure. When the biasing force of the control piston 582 due to the hydraulic pressure becomes larger than the biasing force of the return spring 583, the cam ring 55 moves to the right in the figure. The cam ring 55 is swung to the eccentric amount and the eccentric amount of the cam ring 55 is reduced.

The working space 53 includes a suction portion 531 for sucking the working oil, a shut-off portion 532 for carrying the sucked working oil and performing precompression for increasing the pressure, and a discharge portion 533 for discharging the carried working oil. , Discharge part 533 and suction part 531
It is composed of four parts of a confinement part 534 for connecting and.

A plurality of vanes 59 are connected to the rotor 52 in the circumferential direction. The vane 59 is expandable and contractable in the radial direction of the rotor 52, and the vane 59 and the rotor 5 are
Since the operating hydraulic pressure (discharge pressure) in the discharge unit 533 is added to the connecting portion with 2, the rotor 52 is urged by the discharge pressure and the centrifugal force due to the rotation in the direction outward from the center of the rotor 52 when the rotor 52 rotates. Has been done. Therefore, vane 59
The tip end of the cam ring 55 is always in contact with the inner circumference of the cam ring 55, and when the cam ring 55 is eccentric with respect to the rotor 52 as shown in FIG.
The vane on the side of the closing portion 534 becomes shorter.

In the oil pump having such a structure,
When the rotor 52 rotates and oil is sucked from the suction port 57, the space between the adjacent vanes on the suction portion 531 side is filled with hydraulic oil. The hydraulic oil in this space is pre-compressed by the rotation of the rotor 52 through the cutoff portion 532,
It is conveyed to the discharge portion 533 side and pressure-fed from the discharge port 56. In this way, the job of transporting oil is done.

When the control piston 582 moves to the right in the figure, the amount of eccentricity of the cam ring 55 decreases. Then, the opening area of the discharge port 57 facing the rotor 52 decreases. Therefore, the discharge amount of oil is reduced and the transport amount of oil is also reduced. In this way, it becomes possible to make the amount of oil transported variable.

[0010]

It has been observed that the conventional variable displacement oil pump described above has a larger discharge pulsation than pumps of other types. It is considered that this is due to the difference in shape profile of the working space surrounded by the inner circumference of the cam ring and the outer circumference of the rotor. As shown in FIG. 3, when the cam ring is eccentric to the rotor in order to control the discharge amount of hydraulic oil, the center of the rotor is A, the center of the cam ring is B, the radius of the rotor is r, and the cam ring The radius is R, the distance between the center B of the cam ring indicating the eccentricity of the cam ring and the center A of the rotor is e, and the angle between the straight line connecting the center of the adjacent vanes and the center A of the rotor and the horizontal line is shown. When θ is set, the distance x between the rotor and the cam ring at the position where the vane of interest is present is expressed by x = (ecos θ−r) + (e ² cos ² θ + R ² −e ² ) ^1/2 . This indicates that the distance x between the rotor and the cam ring is a function of θ shown in the drawing, which means that it changes at that position. This change increases in the region where θ is π to 3π / 2 to 0 in FIG. 3, and θ is 0.
It decreases in the region of π / 2 to π. Therefore, considering the pressure of the hydraulic oil filled between the adjacent vanes, as shown in FIG. 4, it is the moment when a part of the space filled with the hydraulic oil is separated from the suction port (FIG. 4A). When the rotor is rotated from the position of (1) to the position of the discharge port shown in FIG. 4B (the position of θ = 0 in FIG. 3), the volume of the filling space increases. Since the distance between the cam ring and the rotor is the longest at this position,
The volume of the filling space is also maximum. Considering the case where the rotor further rotates and reaches the position shown in FIG. 4C,
The filled space is a closed space and its volume decreases. Therefore, the pressure change due to the volume change tends to increase. Therefore, the hydraulic fluid immediately before the discharge port has a considerably high pressure. On the other hand, the discharge of the hydraulic oil to the discharge port is completed, and the hydraulic oil that has not been discharged is returned to the suction port (FIG. 4D).
When the position is reached, the pressure increases because the volume of the filling space decreases. Therefore, the pressure of the hydraulic oil is high immediately before the space filled with the hydraulic oil and the suction port communicate with each other.

In order for the pump to exhibit its function as a pump, it is necessary to cause a local pressure gradient in the pump and maintain the pressure gradient. In this pressure gradient, the fluid is sucked in on the low pressure side and discharged on the high pressure side. Therefore, the pressure on the suction port side is low,
The pressure on the discharge port side is high. The net pressure of the working fluid is obtained by adding the pressure fluctuation due to the volume change of the working space to the normal pressure gradient in the pump. This net pressure becomes extremely high in the portion immediately before the discharge port (FIG. 4C) and the portion immediately before the suction port.

In the conventional oil pump, groove-shaped notches are provided at the edges of the suction and discharge ports as shown in FIG. 4 in order to mitigate the pressure fluctuation, but the pressure fluctuation is accompanied by the volume change. In this case, the pressure change cannot be alleviated even by this notch. This state is generally called overcompression. When overcompression occurs, the vane urging force is lost to the high pressure, and the tip of the vane separates from the cam ring. Then, the hydraulic oil flows into the discharge port and the suction port all at once, causing a pulsation phenomenon. These pulsations cause an abnormal noise (goo noise) that makes the driver uncomfortable, especially when the steering wheel is turned (steady) during idling.

Therefore, the present invention prevents the pulsation of hydraulic oil,
In particular, it is a technical problem to provide a variable displacement oil pump that does not cause a driver to feel uncomfortable when the steering wheel is turned during idling of a passenger car.

[0014]

In order to solve the above-mentioned technical problems, the technical means taken in claim 1 of the present invention comprises a body and a rotatably supported rotatably mounted body. A circular rotor, a cam ring disposed around the rotor and eccentric to the rotor, and a suction port formed in the body for sucking working oil into a working space surrounded by the cam ring and the rotor. And a discharge port formed in the body for discharging the working oil in the working space to the outside, one end connected to the rotor arranged in the radial direction of the rotor and the other end constantly contacting the inner circumference of the cam ring. A plurality of vanes, which are sucked from the suction port and filled in the space between the adjacent vanes, are transported by the rotation of the rotor to the discharge port. In the variable displacement oil pump, which discharges the working oil, increases the discharge amount of the working oil as the eccentric amount of the cam ring with respect to the rotor increases, the working space is a suction portion in which the working oil is sucked from the suction port, From a shutoff portion that is a section that conveys the hydraulic oil sucked from the suction portion to the discharge port, a discharge portion that discharges the hydraulic oil from the discharge port, and a closing portion that connects the discharge portion and the suction portion. In other words, the variable capacity oil pump is characterized in that the space of the shutoff portion and the closing portion is a space surrounded by concentric circles centering on the rotation center of the rotor.

[0015]

The operation of the above technical means is as follows. That is, the shape profile of the cam ring was determined so that, in the maximum eccentricity of the cam ring, the shut-off portion and the closing portion were surrounded by concentric circles centering on the rotation center of the rotor in the working space surrounded by the rotor and the cam ring. With such a configuration, the distance (x in FIG. 3) between the rotor and the cam ring at the shutoff portion and the closing portion is always constant. Therefore, while the hydraulic oil filled from the suction port is conveyed to the discharge port, pressure fluctuation due to the volume change of the hydraulic oil filled space does not occur. Further, in the process of transporting the undischarged hydraulic oil from the discharge port to the supply port, the pressure change due to the volume change of the space filled with the hydraulic oil does not occur in the closing part.

[0016]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a vehicle hydraulic drive system using an oil pump according to an embodiment of the present invention.

In the vehicle hydraulic drive system 10 shown in FIG. 1, the variable displacement oil pump 11 sucks the working oil from the reservoir tank 12 through the suction passage 13, compresses the working oil, and discharges it to the discharge passage 14. It is a thing.
In the body 15 of the variable displacement oil pump 11,
A rotor 17 to which rotational drive of a crankshaft (not shown) is transmitted by a belt (not shown) is arranged, and the rotor 17 can rotate in the body 15 by the transmitted rotational drive force. A cam ring 18 is arranged around the rotor 17 and forms an operating space 19 with the rotor 17. The cam ring 18 is swingable around a pin 20 fixed to the pump body 15 as a fulcrum, and is eccentric to the rotor 17.
That is, the eccentric amount of the cam ring 18 with respect to the rotor 17 changes as the cam ring 18 swings about the pin 20 as a fulcrum.

The working space 19 is a portion for sucking hydraulic oil, a suction portion 191, a shutoff portion 192 for transporting and pre-compressing the sucked hydraulic oil, a discharge portion 193 for discharging the transported hydraulic oil, and a discharge portion 193. And a suction part 191 are connected to each other.

A projection 18a serving as a point of action is formed on the lower portion of the cam ring 18 in the figure, and the projection 18a is biased by a return spring 21 in a direction to increase the eccentricity of the cam ring 18. That is, the eccentric amount of the cam ring 18 is maintained at a predetermined value by the return spring 21. On the other hand, the projection 18a of the cam ring 18 is biased in the direction opposite to the biasing direction of the return spring 21 (rightward in the figure) by the control piston 22 arranged so as to face the return spring 21. Therefore, when the biasing force of the control piston 22 becomes larger than the biasing force of the return spring 21, the cam ring 1
8 swings to the right in the drawing, and the eccentric amount of the cam ring 18 decreases. The urging force of the control piston 22 is
It changes according to the control oil pressure from the discharge amount control means 23 described later.

A suction port 24 and a discharge port 25 are formed in the body 15 so as to extend along the circumferential direction of the rotor 17, the suction port 24 communicates with the suction passage 13, and the discharge port 25 has a discharge passage. It communicates with 14.

The above-mentioned discharge amount control means 23 controls the hydraulic pressure supplied to the control piston 22 to change the eccentric amount of the cam ring 18 to thereby change the variable displacement oil pump 1.
The discharge amount of 1 is controlled. The discharge amount control means 23 includes a sub oil pump 26, a proportional control valve 27, and an electronic control unit (ECU) 28.

The sub oil pump 26 is arranged coaxially with the variable capacity oil pump 11, and for example, a constant capacity oil pump such as a trochoid pump is used. The sub oil pump 26 sucks the working oil from the reservoir tank 12 through the sub oil pump suction passage 29, and discharges the working oil of a constant capacity to the control piston 22 of the variable capacity oil pump 11 for the sub oil pump. It discharges toward the passage 30. Proportional control valve 27
Is disposed in the middle of the bypass passage 31 connected to the middle of the sub oil pump discharge passage 30 and the middle of the sub oil pump suction passage 29.
It controls the hydraulic pressure supplied to. That is, the proportional control valve 27
The hydraulic pressure supplied to the control piston 22 becomes smaller as the opening degree of becomes larger. ECU2
Sensor signals such as the temperature of the engine cooling water and the engine speed are input to 8, and the ECU 28 controls the opening degree of the proportional control valve 27 according to these sensor signals.

Discharge passage 14 of variable displacement oil pump 11
A shunt valve (valve means) 32 is disposed in the middle of.
The shunt valve 32 branches the discharge passage 14 into a first passage 33 and a second passage 34, and a certain amount of hydraulic oil is supplied to the first passage 33 (a necessary amount of operation oil for steering at a stop or steering). oil)
Of the hydraulic oil discharged from the variable capacity oil pump 11 and the fixed amount of hydraulic oil supplied to the first passage 33, and the excess hydraulic oil corresponding to the difference in flow rate between the hydraulic oil supplied to the first passage 33 and the second passage 34. is there. A power steering (steering mechanism) 36 interlocking with the steering wheel 35 is connected to the first passage 33, and the downstream side of the power steering 36 is connected to the reserve tank 12 via a passage 37. A relief passage 42 is connected in the middle of the first passage 33. A relief valve 41 is disposed in the middle of the relief passage 42, and joins the passage 37 on the downstream side thereof. A hydraulic motor 38 is connected to the second passage 34, and a downstream side of the hydraulic motor 38 is connected to the reservoir tank 12 via a passage 40. A cooling fan 39 for cooling cooling water in a radiator (not shown) of the engine is rotatably connected to the hydraulic motor 38.

The operation of the vehicle hydraulic drive system 10 configured as described above will be described.

After the engine is started, the hydraulic oil discharged from the variable displacement oil pump 11 is diverted by the shunt valve 32, and a constant amount of hydraulic oil is supplied to the power steering 36 via the first passage 33.

When the temperature of the engine cooling water is low, the sensor detects it, and based on the signal, the ECU 28 makes the opening degree of the proportional control valve 27 small or closed, and supplies a large hydraulic pressure to the control piston 22. The amount of eccentricity of the cam ring 18 with respect to the rotor 17 is reduced, and as a result, the discharge amount of the variable displacement oil pump 11 is reduced. Therefore, a small amount of hydraulic oil is supplied to the flow dividing valve 32 via the discharge passage 14 and is an excess amount corresponding to the flow rate difference between the discharge amount of the variable displacement oil pump 11 and the hydraulic oil amount constantly supplied to the first passage 33. The amount of hydraulic oil decreases, and the excess hydraulic oil is supplied to the hydraulic motor 3 by the flow dividing valve 32 via the second passage 34.
8 and the hydraulic motor 38 rotates at a low speed. As a result, the cooling fan 39 rotates at a low speed.

When the temperature of the engine cooling water is high, the sensor detects it, and the ECU 28 increases the opening degree of the proportional control valve 27 based on the signal, so that the control piston 22 receives almost no hydraulic pressure. As a result, the return spring 21 swings the cam ring 18 to the left in the drawing to increase the eccentric amount of the cam ring 18 and increase the discharge amount of the variable displacement oil pump 11. Therefore,
A large amount of hydraulic oil is supplied to the flow dividing valve 32 via the discharge passage 14, and the discharge amount of the variable displacement oil pump 11 and the first passage 3
The amount of surplus hydraulic oil corresponding to the flow rate difference from the amount of hydraulic oil constantly supplied to 3 increases, and the surplus hydraulic oil is supplied to the hydraulic motor 38 through the second passage 34 by the diversion valve 32, and the hydraulic motor 38 Rotates at high speed. As a result, the cooling fan 3
9 rotates at high speed.

While the vehicle is stopped (during idling), the radiator cannot be cooled by ventilation from the outside air, so the cooling fan 39 must be rotated at a high speed. Therefore, the hydraulic motor 38 for driving the cooling fan operates a large amount. I need to send oil. Therefore, the eccentric amount of the cam ring 18 of the variable displacement oil pump 11 is maximized during idling of the vehicle. In this state, the shutoff portion 19 in the working space 19
As shown in FIG. 2, the shapes of 2 and the closing portion 194 are space shapes surrounded by concentric circles centering on the rotation center A of the rotor 17. (In the drawing, in the closed part and the closed part, the part indicated by the dotted line is a perfect circle centered on the point B, and the part indicated by the solid line is a concentric circle with the outer periphery of the rotor 17 centered on the point A. The portion indicated by the dotted line is the inner peripheral shape of the conventional cam ring, and the portion indicated by the solid line is the inner peripheral shape of the cam ring in the present invention.)
With such a shape, the space filled with the hydraulic oil surrounded by the vanes does not change in volume at the shutoff portion and the closing portion. Therefore, when pumping the hydraulic oil to the discharge port 25 or when returning the hydraulic oil to the supply port 24, the pulsation phenomenon due to the pressure change does not occur, and the driver does not feel any discomfort.

[0030]

The invention of claim 1 has the following effects.

In the working space surrounded by the rotor and the cam ring, the shape of the shut-off portion and the closing portion is a space shape surrounded by concentric circles centering on the rotation center of the rotor at the maximum eccentricity of the cam ring. It is possible to prevent the pulsation phenomenon of the hydraulic oil based on the volume change of the working space when the vehicle is idling, and to prevent the driver from feeling uncomfortable due to the pulsation.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of a vehicle hydraulic drive system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the shape of the working space of the working oil of the variable displacement oil pump in the embodiment of the present invention.

FIG. 3 is a schematic view showing a shape of a working space of working oil of a variable displacement oil pump in a conventional example.

FIG. 4 is a diagram showing a problem of a conventional variable displacement oil pump.

FIG. 5 is a schematic partial cross-sectional view of a variable displacement oil pump in a conventional example.

[Explanation of symbols]

10 Vehicle Hydraulic Drive System 11 Variable Capacity Oil Pump 12 Reservoir Tank 13 Suction Passage 14 Discharge Passage 15 Body 17 Rotor 18 Cam Ring 18a Projection 19 Working Space 191 Suction 192 Closure 193 Discharge 194 Closure 20 Pin 21 Return Spring 22 Control piston 23 Discharge amount control means 24 Suction port 25 Discharge port 26 Sub oil pump 27 Proportional control valve 28 Electronic control unit (EC
U) 29 Suction passage for sub oil pump 30 Discharge passage for sub oil pump 31 Bypass passage 32 Dividing valve 33 First passage 34 Second passage 35 Handle 36 Power steering 37 Passage 38 Hydraulic motor 39 Cooling fan 40 Passage 41 Relief valve 42 Relief aisle

Claims (1)

[Claims] 1. A body, a perfectly circular rotor disposed in the body and rotatably supported, a cam ring disposed around the rotor and eccentric to the rotor, and the body. A suction port for sucking the formed working oil into the working space surrounded by the cam ring and the rotor, a discharge port formed in the body for discharging the working oil in the working space to the outside, and a radial direction of the rotor And a plurality of vanes whose one end is connected to the rotor and the other end is always in contact with the inner circumference of the cam ring, and the working oil is sucked from the suction port and filled in the space between the adjacent vanes. Is conveyed by the rotation of the rotor and sent to the discharge port to discharge the hydraulic oil, and the hydraulic oil is discharged as the eccentric amount of the cam ring with respect to the rotor increases. In a variable displacement oil pump whose output increases, the working space includes a suction part that sucks hydraulic oil from the suction port, a cutoff part that is a section that conveys the hydraulic oil sucked from the suction part to a discharge port, and A discharge part for discharging hydraulic oil from a discharge port, and a closing part that communicates the discharge part with the suction part. The space between the shutoff part and the closing part is centered on the rotation center of the rotor. Variable capacity oil pump characterized by being a space surrounded by concentric circles.