JPS646352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a vane pump that supplies pressure fluid to a power steering device or the like.

<Prior art> In a conventional pump for a power steering device, when the pump rotation speed exceeds a predetermined number, a flow rate control valve controls the discharge flow rate to be constant.

<Problems to be Solved by the Invention> The flow rate control valve used in the above-mentioned pump has a structure in which a portion of the discharged fluid is bypassed to the bypass passage by sliding the spool due to the differential pressure generated before and after the throttle. Therefore, when the pump rotates at high speeds, the bypass flow rate only increases, and the discharge flow rate from the pump itself cannot be reduced. Therefore, the load torque increases and energy loss increases. It was hot.

<Means for Solving the Problems> The present invention was made in order to eliminate such conventional drawbacks, and the present invention has been made in order to eliminate such drawbacks of the conventional art. Three sets of suction ports and three discharge ports are arranged corresponding to these three cam curves, and these three discharge ports and a flow control valve are connected through discharge passages. The configuration is characterized in that a switching valve is inserted in at least one of the three discharge passages to selectively connect the discharge port to the suction port side, and is switched in response to an external control signal. .

<Function> Since the present invention has the above configuration, when the pump rotates at low speed, the fluids discharged from the three discharge ports are merged to ensure the required flow rate. When the pump rotates at high speed, the switching valve is switched to communicate at least one of the three discharge ports with the suction port. As a result, a portion of the discharge fluid is introduced into the suction port, and the bypass flow rate from the flow control valve is reduced accordingly, and as a result, the load torque of the pump can be reduced.

<Examples> Examples of the present invention will be described below based on the drawings. In Figures 1, 2 and 3, 10
1 shows a pump housing, a hollow chamber 11 with a bottom is formed in this pump housing 10, and this hollow chamber 11 is open at one end of the pump housing 10. An end cover 12 that closes the opening of the pump housing 10 is fitted to one end of the pump housing 10, and is further secured with a circlip. Inside the hollow chamber 11 surrounded by the pump housing 10 and the end cover 12, there is a cam ring 14, a side plate 15 that is in contact with one side of the cam ring 14, and a side plate 15 that has one end that is in contact with the other end of the cam ring 14 and a back side that is in contact with the other end of the cam ring 14. A side plate 16 facing the end cover 12 is housed, and one side plate 1
5 is fitted into a bearing hole 10a of the pump housing 10. The cam ring 14 and the pair of side plates 15 and 16 are attached to the pump housing 1.
The phase is determined by a positioning pin 18 supported between 0 and the end cover 12.

The inner periphery of the cam ring 14 has three cam curves C1, C2, C3 having a phase difference of 120 degrees in the circumferential direction.
A rotor 22 is housed in the cam ring 14. Eleven vanes 21 are slidably fitted in the radial direction and are fitted in the cam ring 14. The axial widths of the rotor 22 and the vanes 21 are set to be somewhat smaller than the axial width of the cam ring 14, and when the pair of side plates 15 and 16 are in contact with both side surfaces of the cam ring 14, the rotor 22 Appropriate side clearance (axial gap) is maintained between the side plates 15 and 16.
The rotor 22 is located in the bearing hole 10 of the pump housing 10.
The spline is engaged with one end of a rotating shaft 24 which is rotatably supported by a bearing 23 that is fitted into the shaft 23a.

A plurality of pump chambers partitioned by vanes 21 are formed between the cam surface C of the cam ring 14 and the outer peripheral surface of the rotor 22, and each pump chamber is connected to the rotor 22.
The rotation of 2 causes a change in volume. On each side of the pair of side plates 15 and 16 that is in contact with the rotor 22, there are three holes corresponding to the pump chambers that perform the expansion process.
Three suction ports IP1, IP2, IP3, and three discharge ports corresponding to the pump chamber that performs the compression process.
OP1, OP2, and OP3 are formed respectively.

The fluid discharged from the discharge ports OP1, OP2, OP3 is controlled by a flow control valve 40 shown in FIG. This flow control valve 40 has a valve hole 4
1, the spool 42 is slidably fitted to the spool 42;
This spool 42 divides the inside of the valve hole 41 into two fluid chambers 41a and 41b. The fluid discharged from the discharge passage 50 is introduced into one of the fluid chambers 41a, and the fluid that has passed through the throttle 44 formed in the union 43 is introduced into the other fluid chamber 41b. Therefore, the spool 42 slides by compressing the spring 45 due to the differential pressure before and after the throttle 44 to control the opening degree of the bypass passage 46, and as a result, a portion of the fluid discharged from the discharge passage 50 is bypassed. The passage 46 is bypassed and the outlet 4
7, the discharge fluid is always delivered at a constant flow rate.

In the pump having such a configuration, the present invention provides a discharge path 50 from the discharge ports OP1, OP2, OP3.
It has the following circuit to control the fluid flowing out to the tank.

That is, the discharge ports OP1, OP2, OP
Discharge passages 51, 52, and 53 are connected to each of the discharge passages 3, and the discharge passages 51, 52, and 53 are merged into one discharge passage 50 in the middle, and then communicated with the flow rate control valve 40. These three discharge passages 5
1, 52, 53, electromagnetic switching valves V2, V3 are inserted in the middle of the discharge passages 52, 53. The electromagnetic switching valves V2 and V3 are sequentially switched as the pump rotation speed increases, and the discharge passages 52 and 53 are connected to the suction port IP2 and the suction port IP2 through the return passages 55 and 56, respectively.
It is now connected to IP3.

Note that the suction ports IP1, IP2, and IP3 are as follows:
It communicates with a suction passage 61 communicating with a reservoir (not shown) and a bypass passage 46 communicating with the flow control valve 40 via an annular groove 60 formed in the hollow chamber 11 . The discharge port OP1 also communicates with a pressure chamber 63 formed between the end plate 12 and the side plate 16.

Next, the operation of the vane pump having the above configuration will be explained. First, when the rotating shaft 24 is driven by the engine, the rotor 22 rotates, and as a result, the working fluid flows from the suction passage 61 to the three suction ports IP1, IP2, and IP3 into the pump chamber that performs the expansion process. There are three discharge ports OP1, OP2,
Pressure fluid is discharged via OP3.

When the engine is rotating at low speed, the electromagnetic switching valves V2 and V3 are in any position, and therefore the three discharge ports OP1 and OP are connected to each other as shown in Figure 2.
2. The pressure fluids discharged from OP3 are combined and discharged into the discharge passage 50. When the engine speed is low and the discharge flow from the three discharge ports OP1, OP2, OP3 is small, the flow control valve 40
is not operated, and the entire amount of the discharged fluid is sent to the outlet 47.
Sent from

After that, the engine speed gradually increases and the fourth
When the rotational speed increases to N1 shown in the figure, the discharge flow rate from the three discharge ports OP1, OP2, OP3 exceeds the required flow rate Q1 as shown in FIG. 4A. Therefore, from this point on, the flow rate control valve 40 operates to bypass the flow rate equal to or higher than the required flow rate Q1 to the bypass passage 46.

Also, when the engine speed increases to N2,
The electromagnetic switching valve V2 is switched to the position, and the discharge fluid from the discharge port OP2 is returned to the suction port IP2. Therefore, as shown in FIG. 4B, only the discharge fluid from the discharge ports OP1 and OP2 is discharged into the discharge passage 50, and the pump load is reduced accordingly.

After that, as the engine speed increases, the discharge port
The discharge flow rate from OP1 and OP2 gradually increases, but the fluid with the required flow rate Q1 or more is discharged from the flow rate control valve 40.
is bypassed to the bypass passage 46 by. At this time, the discharge port has already been switched between two states and is controlled so that the discharge flow rate from the discharge port itself is reduced, so the bypass flow rate accompanying the operation of the flow control valve 40 is also small, and the pump load is accordingly reduced. Become.

Further, when the engine speed reaches N3, both the electromagnetic switching valves V2 and V3 are switched to the position of , and the discharge fluid from the discharge ports OP2 and OP3 is returned to the suction ports IP2 and IP3. Therefore, as shown in FIG. 4C, the discharge passage 50 has a discharge port OP.
Only the fluid discharged from 1 is now discharged,
Pump loads can be further reduced.

Thereafter, as the engine speed increases, the discharge flow rate from the discharge port OP1 increases, but as described above, the flow rate control valve 40 bypasses fluid with a required flow rate Q1 or more. Also at this time, the discharge port
The discharge flow rates from OP2 and OP3 have already been stopped, so the amount of bypass is also small, and the pump load is further reduced.

Note that the degree of reduction in load torque due to the vane pump is calculated as follows.

First, consider the case where the electromagnetic switching valves V2 and V3 are not switched.

The theoretical discharge flow rate per revolution from one discharge port of an 11-vane pump is Vth, the rotation speed is N, and the pressure on the load side is P (however, the pump internal pressure P _IN has a differential pressure ΔP at the throttle 44. Therefore, P _IN =
(ΔP+P) Also, if torque loss due to friction inside the pump is ignored, the theoretical load torque Tth ₁ is given by the following formula.

Tth ₁ = N・Vth/2π (P1+P2+P3) Here, P1, P2, and P3 are each discharge port OP
1, pressure at OP2, OP3, P1=P2=P3
Since =P _IN =ΔP+P, ∴Tth ₂ =3・N・Vth(ΔP+P)/2π.

On the other hand, when calculating the theoretical load torque when switching the solenoid switching valve V2, Tth ₁ = N・Vth/2π (P1+P2+P3) Here, from P2≒0, P1=P3=ΔP+P, Tth ₂ = N・Vth/π (ΔP+P)=2/3Tth ₁ . This is 2/3 of the load torque compared to the case where the electromagnetic switching valve V2 is not switched.

Furthermore, when both solenoid switching valves V2 and V3 are switched, Tth ₃ = N・Vth/2π(P1+P2+P3) From P2=P3≒0, P1=ΔP+P, Tth ₃ =N・Vth(ΔP+P)/2π=1/3Tth ₁ , and by switching and controlling the electromagnetic switching valves V2 and V3 as described above, it is possible to reduce the load torque and create an energy-saving pump.

Incidentally, in the above embodiment, a case of constant flow rate control has been described, but the case of so-called drooping control, in which the flow rate is lowered when the engine reaches a predetermined rotation, can be similarly applied.

<Effects of the Invention> As detailed above, the vane pump of the present invention has the following advantages:
Three discharge ports and a flow control valve are connected through discharge passages, and at least one of the three discharge passages is switched in response to an external control signal to selectively direct the discharge port to the suction port side. Since the configuration includes a switching valve connected to the flow control valve, for example, by switching the switching valve according to a signal such as the engine speed, the flow rate passing through the throttle of the flow control valve can be reduced during high-speed rotation. As a result, the internal pressure of the pump is lowered and the pump load torque can be reduced, and the switching valve can be controlled independently of the control of the flow control valve.As a result, the switching timing of the switching valve can be easily and accurately controlled. Moreover, this switching valve can be switched by simply applying a control signal according to the engine speed, etc., so there is no need to generate special load pressure to switch the switching valve. , which has the advantage of reducing energy consumption accordingly.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a cross-sectional view of the vane pump of the present invention, FIG. 2 is a cross-sectional view taken along the - line arrow in FIG. 1, and FIG. The perspective view, FIG. 4, is a diagram showing the relationship between engine speed and pump discharge flow rate. 10...Pump housing, 14...Cam ring, 21, 22...Rotor, IP1, IP2, IP3
...Suction port, OP1, OP2, OP3...Discharge port, 51, 52, 53...Discharge passage, V2,
V3...Solenoid switching valve.

Claims (1)

[Claims] 1 pump housing and 3 which is fitted in this pump housing and has a phase difference of 120 degrees on its inner periphery.
A cam ring having a cam surface consisting of two cam curves, a rotor housed in the cam ring and connected to a rotating shaft, and the cam ring are arranged in a circle to form a pump chamber partitioned into a plurality of sections. Vanes housed at equal intervals on the circumference, three sets of suction ports and discharge ports corresponding to the three cam curves for sucking or discharging working fluid into the pump chamber, and discharge from the discharge ports. In a vane pump having a flow rate control valve that controls a constant flow rate of discharge fluid, the three discharge ports and the flow rate control valve are connected to each other via a discharge passage, and at least one of the three discharge passages is connected to the flow rate control valve. A vane pump characterized in that a switching valve is inserted that is switched in response to an external control signal and selectively connects the discharge port to the suction port side.