JPH081174Y2 - Liquid pump - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid pump used as a power source for a power steering device of an automobile.

2. Description of the Related Art As a conventional liquid pump of this type, for example, the actual exploitation 59
-21173 is known.

The outline will be described with reference to FIG. 3. In FIG. 1, reference numeral 1 denotes a pump body in which a working chamber 2 is formed. In the working chamber 2, a rotor having vanes (not shown) and a rotor are provided. A rotating shaft for rotation is housed, and the working fluid introduced into the working chamber 2 from the suction port on the pump suction side is sent out from the discharge port 4 on the pump discharge side B to the outside with the rotation of the rotary shaft. .

Reference numeral 5 in the drawing denotes a flow rate control valve arranged on the pump discharge side B. The flow control valve 5 includes a spool 7, a spring 8 that presses the spool 7 toward the orifice 6, and
It is provided with a relief valve 9 provided inside the spool 7.

Then, the spool 7 is slidably fitted in the spool chamber 10 while the spool chamber 10 is fitted to the front end side (orifice 6).
Side pressure chamber 10a and a rear end side back pressure chamber 10b.
The pressure chamber 10a is open to the working chamber 2 on the pump discharge side B and communicates with the discharge port 4 via an orifice 6. Further, the back pressure chamber 10b communicates with the passage 11 outside the orifice 6 via the pressure communication passages 12a, 12b and the surge orifice 12c.

Therefore, the pump discharge pressure upstream of the orifice 6, that is, the pressure of the pressure chamber 10a is applied to the front surface of the spool 7, and the pressure downstream of the orifice 6, that is, the pressure of the back pressure chamber 10b is applied to the rear surface of the spool 7, The amount of opening of the drain passage 13 is controlled by sliding the spool 7 in the axial direction according to the pressure difference between the two chambers 10a and 10b.

Therefore, as the engine speed increases, the pump speed also increases, and when the amount of hydraulic fluid flowing into the pressure chamber 10a increases, the pressure difference before and after the orifice 6 increases, and the spool 7 becomes more back pressure chamber 10b. Sliding to the side, the opening amount of the drain passage 13 also increases and the discharge amount from the pressure chamber 10a also increases. As a result, the flow rate supplied from the orifice 6 to the power cylinder (not shown) through the discharge port 4 is suppressed to a predetermined amount or less even if the engine speed increases, so that a preferable steering assisting force can be obtained. There is.

The relief valve 9 has a cylindrical hole 14 formed in the rear end portion of the spool 7 and a relief having a small passage cross-sectional area which is fixedly inserted at the rear end side of the cylindrical hole 14 and penetrates in the inner axial direction. A plug (15) having a passage (16), a retainer (17) slidably provided inside the cylindrical hole (14) facing the plug (15), and one end of the relief passage (16) supported at the center of a side end surface of the retainer (17). And a check ball 18 for opening and closing the large-diameter opening 16a included in the.

The relief passage 16 communicates the back pressure chamber 10b with the inside of the cylindrical hole 14, and also via a through hole 19 formed in the circumferential wall of the spool 7 along the radial direction and an annular groove 20 on the outer peripheral surface. The inside of the cylindrical hole 14 communicates with the drain oil passage 13. further,
The check ball 18 closes the relief passage 16 by the spring force of the relief spring 21 having one end elastically held by the retainer 17, and when the inside of the back pressure chamber 10b exceeds the spring force (relief pressure) of the relief spring 21. The hydraulic oil in the back pressure chamber 10b is opened to release the relief passage 16, the cylindrical hole 14, the through hole 19, and the annular groove 20.
The surge pressure is prevented by escaping from the drain oil passage 13 to the pump suction side via the.

Problems to be Solved by the Invention In such a conventional example, as described above, the orifice 6 is used.
The check ball 18 of the relief valve 9 opens and closes according to the pressure after passing, that is, the pressure in the back pressure chamber 10b. However, if the flow rate of the hydraulic oil to be relieved becomes larger than necessary, pump loss will occur. Easier to do. Therefore, the passage sectional area of the relief passage 16 is made sufficiently small to suppress the flow rate, and the spring force of the relief spring 21 is set to be relatively large to increase the valve closing pressure by the check ball 18 to increase the large diameter. The opening amount of the opening 16a is controlled to be small.

Therefore, particularly when the engine is cold-started, the viscosity of the hydraulic oil in the pump is high, so the flow resistance due to the viscous resistance of the hydraulic oil flowing from the back pressure chamber 10b to the relief passage 16 becomes large, and the back pressure increases. A normal relief action depending on the internal pressure of the chamber 10b becomes difficult. Therefore, the back pressure chamber 10
b That is, the pump discharge pressure may rise excessively.
As a result, in order to secure the strength of the liquid pump, not only the liquid pump must be upsized, but also the pump discharge side B
Special consideration is required to secure the strength of the pipes.

Means for Solving the Problems The present invention has been devised to solve the above-mentioned problems of the prior art, and forms a bypass passage that bypasses the relief valve and connects the pump discharge side and the pump suction side. The bypass passage is opened only for a fixed time after the pump is started.

Effects According to the present invention, when the pump is started in a cold region where the liquid viscosity is high, the bypass passage that connects the pump discharge side and the pump suction side is opened for a certain period of time at the same time as the pump is started. The abnormal pressure rise of is prevented.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
It should be noted that the same components as those of the above-described conventional device will be described with the same reference numerals.

1 and 2, reference numeral 1 denotes a pump body, and a working chamber 2 is formed in the pump body 1. In the working chamber 2, a rotor having vanes (not shown) and a rotating shaft for rotating the vane are provided. Is accommodated, and the working fluid introduced into the working chamber 2 from the suction port 3 on the pump suction side A is operated from the discharge port 4 on the pump discharge side B with the rotation of the rotating shaft connected to the engine (not shown). It is designed to be sent out of the chamber 2.

Reference numeral 5 is a flow control valve disposed in the pump body 1 on the pump discharge side B. The flow control valve 5 includes a spool 7 slidably provided in a spool chamber 10, and a spool 7
Spring 8 for pressing the drain passage 13 in the closing direction of the drain passage 13.
And a relief valve 9 attached inside the spool 7. A pressure chamber 10a, which is provided on the front end side of the spool 7 and communicates with the orifice 6, communicates with the working chamber 2, and a back pressure chamber 10b on the rear end side has a passage 11 outside the orifice 6. Through the pressure communication passages 12a and 12b and the surge orifice 12c. Therefore, when the pump rotates, the flow rate control valve 5 moves to the left in FIG. 1 while the spool 7 receives the pressure of the hydraulic oil introduced from the working chamber 2 into the pressure chamber 10a and compresses the spring 8. To do. As a result, the spool 7 opens the drain passage 13 to discharge a part of the hydraulic oil in the pressure chamber 10a from the drain passage 13, and supplies the other hydraulic oil to the power steering device through the orifice 6. On the other hand, this flow control valve 5
When the pump is rotating at high speed (when the engine is operating at high speed), the pump discharge amount increases and the differential pressure across the orifice 6 increases, so the spool 7 moves to the left side in the figure against the spring force of the spring 8. The drain oil passage 13 is opened to release a part of the excessive discharge amount to the pump suction side A to supply a desired amount of hydraulic fluid to an external device.

Further, the relief valve 9 provided inside the spool 7 is constructed in the same manner as the conventional one, and when the pump discharge pressure (the hydraulic pressure in the back pressure chamber 10b on the rear end side of the spool 7) rises above a predetermined pressure. In addition, the check ball 18 is relieved by the hydraulic pressure in the relief passage 16 via the retainer 17 and the relief spring.
21 is compressed and moved to the right in FIG. 1, thereby opening the relief passage 16, and a part of the hydraulic fluid passing through the orifice 6 is passed through the back pressure chamber 10b, the relief passage 16, the cylindrical hole 14, It operates so as to return from the drain passage 13 to the pump suction side A through the hole 19 and the annular groove 20.

Reference numeral 22 denotes a bypass passage, which connects the back pressure chamber 10b on the rear end side of the spool 7 with the suction port 3. A check valve 23 for blocking the flow from the back pressure chamber 10b to the intake port 3 is provided in the middle of the bypass passage 22.
And a solenoid valve 24 for opening the check valve 23 based on a control signal from a controller (not shown).

That is, the check valve 23 appropriately blocks the hydraulic oil in the back pressure chamber 10b from flowing through the bypass passage 22 into the suction port 3, and the solenoid valve 24 for opening the check valve 23 is opened. As shown in FIG. 2, the drive rod is advanced to the right in the figure by the excitation signal (current) from the controller to move the check valve 23 to the right in the figure against the spring force of the check spring. It is designed to open.

The controller (not shown) is connected to a liquid temperature sensor (not shown) that senses the liquid temperature of the hydraulic fluid and an engine start key switch (not shown) so that the liquid temperature is below a predetermined temperature. , When the engine start key switch is turned on, an excitation signal is output to the solenoid valve 24 for a predetermined time,
The check valve 23 is opened via the solenoid valve 24 to open the bypass passage 22.

According to the above-described structure of the embodiment, when the working fluid has a low temperature in a cold region and the viscosity of the fluid is high, the hydraulic pressure of the working chamber 2 at the time of starting the engine becomes high. In this case, since the bypass passage 22 that bypasses the relief valve 9 and connects the pump discharge side B to the pump suction side A is opened by the solenoid valve 24 that operates simultaneously with the engine start, the hydraulic pressure in the working chamber 2 is increased. Is prevented from abnormally high temperature.

Since the solenoid valve 24 stops operating after a certain period of time and closes the bypass passage 22, the flow rate of the hydraulic fluid is adjusted only by the flow rate control valve 5 thereafter. Further, the solenoid valve 24 does not operate when the liquid temperature is equal to or higher than the predetermined temperature.

Effect of the Invention As described above, the present invention forms a bypass passage that bypasses the relief valve attached to the flow control valve and connects the pump discharge side and the pump suction side. Since it is opened only for the time, it is possible to suppress an abnormal increase in pump discharge pressure that occurs when the engine is started in a state where the liquid temperature is low and the liquid viscosity is high. As a result, there is a practically great effect that the pump body can be made smaller and lighter.

[Brief description of drawings]

1 is a sectional view of a liquid pump showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view showing a conventional liquid pump. 5 ... Flow control valve, 9 ... Relief valve, 22 ... Bypass passage, A ... Pump suction side, B ... Pump discharge side.

Claims (1)

[Scope of utility model registration request] 1. A flow rate control valve for adjusting a discharge flow rate is disposed on a pump discharge side, and the flow rate control valve is opened when a discharge pressure exceeds a predetermined pressure so that a part of the discharge amount is pumped. In a liquid pump provided with a relief valve for escaping to the suction side, a bypass passage that bypasses the relief valve and communicates with the pump suction side is formed on the pump discharge side, and the bypass passage is opened only for a certain time from the pump start. A liquid pump characterized by the above.