JPH01294981A - Vane pump - Google Patents

Abstract

PURPOSE:To reduce the rotational load while increasing the rotational speed so as to reduce hydraulic pressure pulsation by forming a recess in a cam surface within an area which is coincident with the timing of lowering the pressure of hydraulic pulsation, and by eliminating a part of a vane pressing chamber facing the recess. CONSTITUTION:When a rotor 108 is rotated inside of a cam ring 102 in which a cam 104 is formed at the inner surface thereof, a plurality of vanes 114 are extended and retracted in radial slits 110 formed in a rotor 108 so as to slide on the cam 104. As a result, the volumes of pump chambers defined between the vanes 114 are increased and decreased, effecting pump action. In this arrangement, a recess 106 is formed in the cam 104 at a position which is coincident with the timing of lowering the pressure of hydraulic pulsation. Further, in a vane pressing chamber 116 which introduces discharged oil to the inner end of each slit 110 so as to press the associated vane 114 against the cam 104, only a part 118 located radially inward of the recess 106 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vane pump used in a power steering device of a vehicle and the like.

(Prior Art) Generally, as shown in Fig. 5, a vane type oil pump includes a cam ring (12) having a substantially elliptical cam surface (12a) on the inner periphery, and a cam ring (12) that rotates within the cam ring (12). a rotor (14) that slides within a radial slit (14a) formed in the rotor (14), and a plurality of vanes (1) whose tips slide in sliding contact with the cam surface (12a) of the cam ring (12). ) to (10), the cam ring (12), rotor (14), and vanes (1) to (10).
) is provided with plates (1B) etc. that sandwich the pump from both sides, and as the rotor (14) rotates, the pump chamber (20) is formed between two adjacent vanes (1) to (lO).
Oil is sucked in and discharged through a suction boat (22) and a discharge port (24) formed in the plate (18) by increasing or decreasing the volume of the plate (18).

In the vane pump as described above, pulsation of the discharge oil pressure, that is, a cyclic rise and fall of pressure in the discharge oil path occurs. This is a fluctuation in the instantaneous amount of oil discharged into the discharge oil path, and the causes are (-) the rate of change in volume of the pump chamber relative to the rotor rotating at a constant rotation, and (d) the rotational speed of the rotor. (3) When the pump chamber in the suction area moves to the discharge area, the amount of oil is replenished from the path side to compensate for the difference in oil density.

Regarding the first factor mentioned above, in order to eliminate the discontinuous points of the ideal cam made up of Archimedean lines and allow the vanes to slide smoothly on the inner surface of the cam, some kind of transition curve must be used. A cam form with a constant volume change rate cannot exist in reality. In addition, the second factor is unavoidably caused by shaft eccentricity caused by the machining accuracy and clearance of each part, and the third factor is:
A configuration has also been proposed in which the pump chamber is contracted in a closed state when entering the 8th line of the discharge area, and the pressure is increased to the discharge pressure before shifting, but in the case of an automobile power steering horn in which the discharge oil pressure itself changes, It is not possible to cover the entire area.

[Problem to be solved by the invention]

In any case, it is currently impossible to directly solve each of the above factors.

Therefore, when measuring the hydraulic pressure pulsations occurring in the discharge oil path due to the above factors, it is recognized that the pressure rises and falls as shown in FIG. This pressure rise and fall occurs at a number of cycles corresponding to the number of vanes during rotation of the rotor.

The present invention was made for the purpose of reducing the above-mentioned hydraulic pulsation, and in particular, in the area where the pulsating pressure decreases,
Reduce pump rotational load and increase instantaneous rotational speed,
This is an attempt to reduce the absolute imaging width of pulsation overall by preventing pressure drop.

[Means to solve the problem]

A vane pump according to the present invention includes: a cam ring having a cam formed on the inner surface; a rotor rotating within the cam ring;
a plurality of vanes that move forward and backward within a radial slit formed in the rotor, and whose tips slide into contact with the cam surface;
A vane pressing chamber is formed in which discharge oil is introduced into the inner end of the slit to press the vane against the cam surface. The pump action is performed by increasing or decreasing the volume of the pump chamber formed between two vanes, and a recess is formed on the cam surface in an area that coincides with the timing when the pressure of the discharge hydraulic pulsation caused by the pump action decreases. In addition, the vane pressing chamber located radially inward of this recess is removed.

(Function) In the vane pump according to the present invention, when the vane rotates and comes to the area where the recess is formed, the discharge oil is not introduced to the back side, so the vane tip moves away from the cam, so the frictional resistance decreases and instantaneous As a result, the rotational speed increases, pressure drop is prevented, and hydraulic pulsation is reduced.

〔Example〕

First, the process that led to the development of the device of this embodiment will be explained. In a vane pump, in order to press the vanes against the inner surface of the cam ring, a vane pressing chamber (reference numeral (28 in Fig. 5) The discharge oil pressure is guided through the In this case, the discharge oil pressure is P,
If the cross-sectional area of the vane is S, then the vane located at the boundary between the suction region and the discharge region is P-S/2, the vane located in the suction region is p-s, and the vane located in the discharge region is is under pressure. Although the pressing force in the discharge area may not be zero due to differences in mechanisms such as the vane pressing chamber being choked, it can be assumed that the pressing force is approximately the same as above.

The force that presses the vane acts as a friction load on the rotation of the pump.

Therefore, if the vane and cam ring can be separated instantaneously, the rotational load can be removed instantaneously, increasing the instantaneous rotational speed as described above, preventing pressure drop, and reducing hydraulic pulsation. becomes possible.

A conceivable means for separating the cam ring and the vane is to provide a concave shape in a desired area of the cam on the inner surface of the cam ring, that is, at a position that matches the timing at which the pulsating pressure decreases. With this configuration, when the vane enters the concave area formed on the cam, the amount of oil introduced to the back side of the vane is insufficient for the tip of the vane to follow the concave shape. In this case, the pressing force at the tip of the vane decreases, and the frictional load decreases.

As a result of actually measuring and comparing the amplitude of pulsation between the vane pump in which a recess is formed on the inner surface of the cam ring as described above and a conventional pump, differences as shown in FIG. 2 were observed. In addition, the solid line (a
) is a pump with a recess formed therein, and the broken line (b) is a conventional pump. In other words, a pump with a recess formed in the cam ring has a slightly larger pulsation at low rotation speeds than a conventional pump.
At high rotation speeds, a significant pulsation reduction effect is obtained.

Here, we will discuss the third reason for the high pulsation in the low rotation range.
This will be explained using figures. When the pump speed is high, the vane (
40) During the time when pressure oil is hardly replenished to the rear side, the vane (40) is inserted into the recess (44) of the cam ring (42).
) (see vane (40a)), and only an instantaneous reduction effect of the frictional load appears. However, when the pump rotation speed is low, the vane (4o) sufficiently follows the recess (44) and the vane (40b) (Reference) At the same time, the effect of reducing the frictional load does not appear, and at the same time, the vane (4o) enters the recess (44), so the amount of oil supplied to the back side of the vane (40) momentarily increases. As a result, the amount of oil in the discharge oil path further decreases, which has the opposite effect of increasing pulsation.

Therefore, in order to achieve the objective of reducing pulsation over the entire range from the low rotation range to the high rotation range of the pump, it is necessary to add the following mechanism. In other words, in order to allow the vane to be separated from the cam ring by the concave shape formed in the cam ring, and to prevent the vane from entering the concave portion at low rotation speeds, the area where the concave portion is formed is located on the back side of the vane. It is necessary to provide a mechanism that instantly cuts off the supply of discharged oil to.

Therefore, as in the embodiment shown in FIG.
02) A recess (108) is formed on the inner surface of the cam (1 (14)) at a position that matches the timing when the pulsating pressure decreases.
The inner end (112) of the radial slit (110) of
), the vane (114) is moved to the cam surface (10
4) The above object was attempted to be achieved by eliminating only the portion (11B) located radially inward of the recess (10B) of the vane pressing chamber (11B) that is configured to press the recess (10B).

The pulsation of the vane pump according to the above embodiment was measured and a graph comparing it with a conventional pump is shown in FIG. Note that the solid line (c) represents the pump according to this embodiment, and the broken line (d) represents the conventional pump. As is clear from this graph, the pump according to this example was able to reduce pulsation more than the conventional pump over the entire range from low rotation to high rotation. However, the position where the recess (106) is formed in the cam (104) is determined by the vane (1) that partitions the suction area and the discharge area.
14), the vane (114)
This is not preferable because a backflow of oil occurs through the gap between the cam surface (104) and the cam surface (104). 114) to the cam ring (10
2) It is most effective to provide it in the suction area where the pressing force is large.

〔Effect of the invention〕

As described above, according to the present invention, by reducing the pump rotational load and increasing the instantaneous rotational speed in a region where pulsating pressure decreases, pressure drop can be prevented and pulsation can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main parts of a vane pump according to an embodiment of the present invention, Fig. 2 is a graph comparing the pulsation amplitude of a conventional pump and a partially improved pump, and Fig. 3 is a graph comparing the pulsation amplitude of a conventional pump and a partially improved pump. A diagram explaining the operation of a partially improved pump, Figure 4 is a graph comparing the amplitude of pulsation between the conventional pump and the pump of this embodiment, Figure 5 is a cross-sectional view of the conventional pump, and Figure 6 is It is a graph showing the pulsation of the discharge oil pressure of a conventional valve. (102)...Cam ring, (104)...Cam, (106)...Cam recess, (108)...
・Rotor, (110)...Slit, (114
)... Vane, (118)... Vane pressing chamber, (118)... Portion located radially inward of the recess. Patent Applicant Jidosha Kiki Co., Ltd. Representative Patent Attorney Sou Yamazaki Kokuma Aikawa Eikichi Otsuka
Miyaji Atsushi 1...So 2nd cause Figure 3 F. 20

Claims (1)

[Claims] a cam ring having a cam formed on its inner surface; a rotor rotating within the cam ring; a plurality of vanes that move forward and backward within radial slits formed in the rotor and whose tips slide against the cam surface; A vane pressing chamber is formed in which discharged oil is introduced into the inner end of the slit to press the vane against the cam surface. In a vane pump that performs pumping action by increasing or decreasing the volume of a pump chamber formed between two vanes, a recess is formed on the cam surface in a region that matches the timing when the pressure of the discharge hydraulic pulsation caused by the pumping action decreases. Also, a vane pump characterized in that the vane pressing chamber located radially inward of the recess is removed.