JPH0754779A - Radial piston pump - Google Patents

Abstract

PURPOSE:To realize stable delivery by determining a suction port position of a radial piston in accordance with a position relation to a pump suction chamber center in a mounting condition, and eliminating a difference between delivery flow amounts of upper/lower radial piston pumps. CONSTITUTION:A valve means 13, responding to a pump delivery pressure by receiving a capacity control pressure and delivery pressure control force in a reverse direction to this capacity control pressure and determining an opening, is provided between a reservoir 12 and a suction passage 11, to control opening the suction passage 11. A distance from a piston internal periphery direction end part of a suction port, provided in a radial piston 7 positioned in an upper side from a pump suction chamber center in a mounting condition, is increased larger than a distance from a piston internal periphery direction end part of a suction port provided in a radial piston 7 positioned in a lower side from the pump suction chamber center, and a delivery flow amount of the radial piston 7 in the upper side in the mounting condition is set larger than that in the lower side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial piston pump which controls a discharge flow rate according to a pump discharge pressure input as a displacement control pressure.

[0002]

2. Description of the Related Art A radial piston pump, which is one of variable displacement pumps, saves pump drive energy by controlling to discharge a required minimum amount required by a device operated by a discharge pressure. Fuel efficiency can be improved. As a conventional example of such a radial piston pump, there is one described in Japanese Patent Laid-Open No. 213683/1993.

In this conventional example, valve means is provided on the suction passage side of the radial piston pump, and the spool of the valve means receives the pump discharge pressure as capacity control pressure and responds, and discharges from the direction opposite to this. The opening of the suction passage of the pump is controlled by receiving a pressure control force and responding to this, and by making a stroke to a position where forces in both directions are balanced. By this opening degree control, the pump capacity can be controlled according to the pump discharge pressure.

[0004]

In the radial piston pump of the above-mentioned conventional example, when the suction passage is throttled to a low flow rate, the flow rate of the working fluid flowing into the pump suction chamber is restricted so that the pump suction chamber is Since liquid and gas are mixed, the working fluid is more likely to flow into the lower part of the pump suction chamber in the mounted state.Therefore, the liquid existing in the upper and lower parts of the pump suction chamber is As a result of unevenness and a difference between the discharge flow rate of the radial piston located above the pump suction chamber and the discharge flow rate of the radial piston located below the pump suction chamber, the discharge flow rate fluctuation as shown in FIG. 5 occurs. become. Such fluctuations in the discharge flow rate cause large fluctuations in the discharge pulse pressure and large fluctuations in the driving torque, and deteriorate the characteristics relating to vibration and noise.

The present invention has been made in view of such a problem, and the position of the suction port formed in the radial piston or the position of the center of the pump cam shaft is related to the positional relationship with the center of the pump suction chamber in the mounted state. Therefore, it is an object of the present invention to solve the above-mentioned problem by making a determination according to the above-mentioned determination so that the difference between the discharge flow rates of the upper and lower radial piston pumps is eliminated.

[0006]

To this end, the structure according to claim 1 of the present invention receives the pump discharge pressure as a displacement control pressure, responds to the displacement control pressure, and opposes the displacement control pressure. Responding to this by receiving the discharge pressure control force of
A radial piston pump having valve means for determining the opening, the opening of the suction passage being controlled by the valve means to control the discharge flow rate, the radial piston pump being located above the center of the pump suction chamber in the mounted state. The distance from the piston inner circumferential end of the suction port provided on the radial piston is
It is characterized in that it is larger than the distance from the piston inner circumferential direction end of the suction port provided in the radial piston located below the center of the pump suction chamber.

According to a second aspect of the present invention, the pump discharge pressure is received as a displacement control pressure and responds to the displacement control pressure, and a discharge pressure control force in a direction opposite to the displacement control pressure is received. In the radial piston pump having valve means for controlling the opening degree of the suction passage, the opening degree of the suction passage is controlled by the valve means to control the discharge flow rate. It is characterized in that it is located above the center of the pump suction chamber.

[0008]

According to the first aspect of the present invention, the radial passage is controlled by controlling the opening degree of the suction passage by the valve means whose opening degree is determined by receiving the capacity control pressure and the discharge pressure control force in the opposite directions. When controlling the discharge flow rate of the pump, the distance from the piston inner circumferential end of the suction port provided in the radial piston located above the pump suction chamber center in the mounted state should be below the pump center. Since the suction port provided in the radial piston located is larger than the distance from the end in the inner circumferential direction of the piston, even if the working fluid in the pump suction chamber is uneven due to suction limitation, the upper and lower radial pistons Since the difference in the discharge amount between them becomes small, there is no fluctuation in the discharge flow rate as shown in FIG. 5, and stable discharge with a small amplitude can be realized.

According to the second aspect of the present invention,
When controlling the discharge flow rate of the radial piston pump by controlling the opening degree of the suction passage by the valve means whose opening degree is determined by receiving the capacity control pressure and the discharge pressure control force in the directions opposite to each other, the pump in the mounted state is used. Since the center of the camshaft is located above the center of the pump suction chamber, the same effect as that of the first aspect can be obtained.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view showing the structure of a radial piston of a first embodiment of the present invention. The radial piston pump of the first embodiment is basically the same as the radial piston pump of Japanese Patent Application No. 4-348909 filed previously by the applicant of the present application, with the modification of FIG. 2 described later. It is a thing.

In FIG. 1, 1 is a pump housing, and 2
Denote cam drive shafts (hereinafter, shafts), respectively. The shaft 2 has an inner end rotatably supported by a bearing 3, an outer end rotatably supported by a bearing 4, and an outer end further having a seal 5 for sealing with the pump housing 1. To provide. A belt drive pulley 6 is wedged on the tip of the shaft 2 protruding from the pump housing 1.

A rotary eccentric cam (hereinafter referred to as an eccentric cam) 2a is integrally formed on the shaft 2 between the bearings 3 and 4, and the eccentric cam is circumferentially arranged at equal intervals and extends in a plurality of radial directions. The existing radial piston 7 is provided. These radial pistons 7 are slidably fitted in the pump housing 1 and pressed against the outer circumference of the eccentric cam 2a by springs.
Further, the radial piston 7 has a hollow end surface that is in contact with the eccentric cam 2a, and a suction port 7a is formed on its peripheral wall as described later.

A partition plate 8 is fixed to one end of the eccentric cam 2a, whereby the pump chamber is divided into a main pump chamber 9 facing the radial piston 7 and an auxiliary pump chamber 10 isolated from the main pump chamber. As shown in FIG. 1, a reservoir 12 is connected to the auxiliary pump chamber 10 via an intake passage 11, and a valve means 13 is inserted into the intake passage 11. The valve means 13 receives the pump discharge pressure output through the delivery valve 14 as a displacement control pressure at the left end in the figure, and the spring force of the spring 15 is input in the opposite direction as a discharge pressure control force.
By displacing these to a balanced position, the opening degree of the pump suction passage 11 is determined, and the pump capacity is a well-known one that is controlled according to the pump discharge pressure.

In the present embodiment, in the mounted state shown in FIG. 2, the position forming the suction port 7a is changed according to the relative positional relationship between the radial piston and the center of the pump suction chamber. That is, in the mounted state, the radial piston 7 located below the center of the pump suction chamber (the lower side in the drawing) is provided with the suction port 7a at a distance h from the end in the inner circumferential direction. The radial piston 7 located above the center (upper side in the drawing) has a suction port 7a at a position at a distance H from the end in the inner circumferential direction.
Furthermore, in the radial piston 7 positioned at the same level as the center of the pump suction chamber in the mounted state, a suction port 7a is formed at a position (H + h) / 2 from the end in the inner circumferential direction. It is assumed that H> h.

Next, the operation of the above embodiment will be described. When the eccentric cam 2a is rotationally driven by the belt driving pulley 6 via the shaft 2, the eccentric cam causes the radial piston 7 to make a stroke, and the suction port 7a of each radial piston 7 begins to open with respect to the main pump chamber 9. During the suction stroke until reaching the maximum opening, the working fluid is sucked from the reservoir 12 and guided to the main pump chamber 9 through the valve means 13 and the pump suction passage 11. The working fluid flowing into the main pump chamber 9 discharges the suctioned liquid through the delivery valve 14 during the stroke of the reverse direction and during the discharge stroke of the piston 7 in which the port 7a is closed and still strokes in the same direction.

During the suction stroke, the valve means 13 is acted on by the pump discharge pressure as a displacement control pressure and a discharge pressure control force (spring force of the spring 15) in a direction opposite to the pump control pressure so that the two are in a balanced position. Stroke to and suction passage 1
The opening degree of 1 is controlled, thereby limiting the flow rate of the working fluid. The working fluid flowing into the main pump chamber 9 is the eccentric cam 2a.
With the negative pressure generated when the radial piston 7 is returned by the spring force of the spring 15 after the working fluid existing in the radial piston 7 is discharged by the rotation of the suction piston 7a, the suction port 7a opens to the main pump chamber 9. At the same time, it is sucked into the radial piston 7. At this time, as shown in FIG. 2, the degree of the negative pressure is higher when the suction port 7a of the radial piston 7 is high (that is, when the distance from the inner circumferential end of the suction port 7a is larger) than when it is low. Increases, and the suction force when the suction port 7a opens is increased.

Therefore, when controlling the pump flow rate by such suction restriction, the suction port 7a of the radial piston located above the center of the pump suction chamber in the mounted state is the suction port of the radial piston pump located below. 7a (H> h) to make the suction force stronger, in other words, by making the specific discharge amount of the upper radial piston larger than the specific discharge amount of the lower radial piston, The discharge rate increases. Therefore, as is clear from a comparison between the pump drive torque waveform of the present embodiment shown in FIG. 3 and the pump drive torque waveform of the conventional example shown in FIG. 5, the problem that the working fluid discharge amount greatly differs between the upper and lower radial pistons is solved. Is
It is possible to prevent large fluctuations in pump drive torque,
Problems such as large fluctuations in the discharge pulse pressure, large vibrations, and large noise do not occur.

FIG. 4 is a sectional view showing the construction of the essential parts of the radial piston of the second embodiment of the present invention. In the second embodiment, as shown in FIG. 4, the suction port 7a in each radial piston 7 is obtained in order to obtain the effect of eliminating the difference in pump discharge amount realized by the configuration shown in FIG. 2 in the first embodiment.
And the center of the camshaft 16 is the center of the pump suction chamber (the center of the pump arrangement) in the mounted state.
It is arranged so as to be located above.

When the center of the camshaft is eccentric to the center of the pump suction chamber in this way, the specific discharge amount of the upper radial piston becomes larger than the specific discharge amount of the lower radial piston. The same effect as the example can be obtained.

In the second embodiment, the shape of the inner surface of the housing of the pump suction chamber may be changed instead of the eccentricity of the center of the camshaft upward with respect to the center of the pump suction chamber. The same effect as that of the first embodiment can be obtained.

[0021]

As described above, according to the radial piston pump of the present invention, the difference between the discharge flow rates of the upper and lower radial piston pumps depends on the positional relationship between the position of the suction port formed in the radial piston and the center of the pump suction chamber in the mounted state. Is determined to be eliminated, or the center of the pump camshaft is located above the center of the pump suction chamber in the mounted state, so the working fluid in the pump suction chamber is uneven due to suction limitation. Even in this case, since the difference in the discharge amount between the upper and lower radial pistons is small, there is no change in the discharge flow rate as shown in FIG.
It is possible to realize stable ejection with a small amplitude.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a radial piston of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a suction port provided in the radial piston of the same example in relation to an attached state.

FIG. 3 is a diagram illustrating a discharge flow rate characteristic and a pump drive torque characteristic of the same example.

FIG. 4 is a cross-sectional view showing the structure of a main part of a radial piston according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a discharge flow rate characteristic and a pump drive torque characteristic of a conventional example.

[Explanation of symbols]

 1 Pump Housing 2 Cam Drive Shaft 2a Rotation Eccentric Cam 6 Belt Drive Pulley 7 Radial Piston 7a Suction Port 9 Main Pump Chamber 10 Sub Pump Chamber 11 Suction Passage 13 Valve Means 15 Spring 16 Cam Shaft

Claims (2)

[Claims] 1. An opening is determined by receiving a pump discharge pressure as a displacement control pressure and responding to the displacement control pressure and also receiving a discharge pressure control force in a direction opposite to the displacement control pressure. A radial piston pump having a valve means for controlling the opening of the suction passage to control the discharge flow rate, the suction being provided in the radial piston located above the center of the pump suction chamber in the mounted state. The distance from the piston inner circumferential direction end portion of the port is made larger than the distance from the piston inner circumferential direction end portion of the suction port provided in the radial piston located below the pump suction chamber center, Radial piston pump. 2. The opening is determined by receiving the pump discharge pressure as a displacement control pressure and responding to the displacement control pressure and also receiving a discharge pressure control force in a direction opposite to the displacement control pressure. In a radial piston pump having valve means for controlling the opening of the suction passage to control the discharge flow rate, the center of the pump camshaft is located above the center of the pump suction chamber in the mounted state. Radial piston pump characterized by doing so.