JP2000265965A - Displacement pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise in cold starting at low cost without increasing a structure space of a displacement pump. SOLUTION: A discharge chamber 10A of a pump can be connected to an outlet passage 14 through a hole 13 in which an adjusting piston 17 can be slid against force of a spring 16. One flow rate control valve 11 is arranged in order to adjust the effective flow rate. The discharge chamber 10A is connected to a spring chamber 15 of the adjusting piston 17 through one bypass passage 18 in the range of the hole 13 housing the adjusting piston 17. The adjusting piston 17 controls the opening sectional surface of a throttle passage 12 for connecting the spring chamber 15 to the outlet passage 14 according to the outflow of this displacement pump. In such the pump, a second bypass passage is provided between the throttle passage 12 and the outlet passage 14. The outflow of the pump is guided to the outlet passage 14 through a throttle section 22 of the second bypass passage. Therefore, high viscosity correspondency can be provided, and the cold cooling state is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive displacement pump such as a vane pump or a roller pump having a discharge chamber, in which a control piston is slidable against the force of a spring. To a discharge passage connected to the outlet via a hole guided in the outlet.
The control piston controls the outlet cross section of the throttle passage in relation to the pump speed or the delivery flow. A flow control valve having a control piston loaded by a spring force is also provided in the casing hole.

[0002]

2. Description of the Prior Art A positive displacement pump of this kind is known from DE-A1-44333698.
With this positive displacement pump, a delivery flow characteristic curve exhibiting a discontinuous course is obtained. In this pump, a part of the delivery flow collected in the discharge chamber is guided to the outlet passage through the bypass passage and the throttle hole.

In the case of this known positive displacement pump, a so-called cold start noise may be generated when starting at a low temperature. The reason for this is that the aperture is relatively short and therefore has only a slight viscosity response. As a result, during a cold start, a delivery rate approximately equal to that in the "normal" operating state with the heated pressure medium is delivered to the actuator. A large negative pressure is created because the pump must re-inhale an amount equal to the amount to exhale. As a result, the suction chamber of the pump is only poorly filled. This produces significant pressure pulsations and consequently cold start noise.

[0004] European Patent Publication EP-B1-0220
In the case of another pump known from 187, a throttle insert with an orifice and a measuring throttle downstream of the orifice is arranged in order to avoid starting noise during cold start. The orifice and measurement restrictor are located in the main flow of the pump to the actuator, in the region of the flow regulating valve. The measuring throttle is formed as a single hole in the throttle insert, the flow cross section of which is approximately equal to the cross section of the orifice, the length of which is greater than the length of the orifice and the inner diameter of the hole.

In the case of pumps of the type mentioned at the outset, it is not possible to provide such an orifice and a downstream measuring throttle due to the lack of sufficient structural space. Also, the relatively large cost involved in forming the holes in the draw insert.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a positive displacement pump of the type mentioned at the outset in which start-up noise during cold start is largely avoided. This problem must be solved with as little construction and cost as possible. Also, the construction space of the pump must not be increased.

[0007]

SUMMARY OF THE INVENTION The object of the present invention has been attained by a positive displacement pump having the structure shown in claim 1 of the present invention. That is, a second bypass passage is disposed between the throttle passage and the outlet passage, and the second bypass passage first diverts the delivery flow of the pump from the outlet passage, and then to the outlet passage only after the throttle section. Lead them towards.

[0008] According to such a configuration, the above-mentioned European Patent Publication EP-B requiring a relatively large structural space.
The same operation and effect as those of the high-cost aperture insert disclosed in Japanese Patent No. 1-0220187 can be obtained in a simple manner.

[0009] Advantageous and advantageous embodiments of the invention are set out in the dependent claims. It is particularly advantageous if the second bypass channel has a substantially rectangular cross section.

If the ratio of the surface, which is determined by the length and the cross section of the second bypass passage and which is wetted by the oil flow to the actuator to the cross section of the throttle passage, is greater than about 13: 1. For example, it works advantageously in the cold start mode.

The pump can be made particularly cost-effective if the second bypass channel is cast into the pump housing part in which the regulating piston and the flow regulating valve are arranged. In this case, it is furthermore advantageous if the second bypass channel opens at least in the region of its throttle section towards the end face of the housing part.

[0012]

Next, the present invention will be described in detail with reference to the illustrated embodiment.

Hereinafter, the present invention will be described in accordance with an embodiment as a vane pump. However, the present invention can be applied to another positive displacement pump such as a roller pump with the same effect. The vane pump of the embodiment is used to pump pressure oil from a tank (not shown) to an actuator (not shown), for example, a power steering device.

A pump component 2 comprising a rotor 3, a cam ring 4 and a number of vanes 5 is inserted into the casing 1. The rotor 3 has a drive shaft 6 in a bearing casing 7.
Supported above.

A working chamber in the form of a volume chamber (not shown) is formed between the vane 5 and the cam ring 4 and these working chambers are closed at their axial ends by two control plates 8,9. ing. As is well known, one discharge port 10 and a suction port (not shown) are formed in the control plates 8 and 9. The discharge port 10 communicates with one discharge chamber 10A.

In the bearing casing 7, a bypass type flow regulating valve 11 having a piston 11A loaded by a spring is disposed for controlling the pressure oil flowing to the pressure connection portion. The configuration of the flow regulating valve 11 and the pressure limiting valve not visible from the drawing is described, for example, in U.S. Pat.
No. 9 and will not be described in detail. Further, a suction passage and a discharge passage connecting each working chamber to the suction connection portion, the flow regulating valve 11 and the pressure limiting valve are formed in the bearing casing 7. These passages are also generally known, and thus need not be described in detail. Bypass type flow control valve 11
Are provided in the bearing housing 7 in the form of one throttle passage 12.

The throttle passage 12 has a single hole 1 formed in the bearing casing 7 substantially parallel to the axis of the drive shaft 6.
3 to one exit passage 14. Restrictor passage 12
The connection between the and the outlet passage 14 will be described later. The opening of the throttle passage 12 communicates with one spring chamber 15 containing a spring 16. One end of the spring 16 has a bearing casing 7.
The inner end of the bore 13 is supported by the inner end, the other end of which is supported by a control piston 17 slidably guided in the bore 13. The discharge port 10 has one bypass passage 1
The spring chamber 15 and the opening of one throttle passage 12 are always connected by 8. The bypass passage 18 is substantially T-shaped as shown in the cross-sectional view of FIG. 2 and is preferably formed by casting in the bearing housing 7. The bypass passage 18 opens to the hole 13 side. The control piston 17 can slide against the force of the spring 16. Regardless of the position of the control piston 17, the connection from the discharge port 10 to the spring chamber 15 via the bypass passage 18 is maintained.

The control piston 17 has a control edge 19 at an end facing the spring chamber 15, and this control edge 19 is provided between the end face of the control piston 17 on the spring chamber 15 side and the cylindrical peripheral surface. Is formed by cutting. The control edge 19 cooperates with the opening of the throttle passage 12, and the open cross section of the throttle passage 12 decreases as the control piston 17 moves toward the spring chamber 15. This control edge 19 may be formed as a sharp edge, step or chamfer. By means of the control edge 19 having such a structure, the drawing process can be influenced.

The precise connection between the throttle passage 12 and the discharge passage 14 will be described below in detail. The throttle passage 12 has a hole 13
The opening on the opposite side is one second bypass passage 20.
Leading to The second bypass passage 20 is combined from many sections. First, one passage section 21 of the second bypass passage 20 that discharges the delivery flow of the pump and bypasses the passage 14 to the throttle passage 12 communicates therewith. Then 1
A passage section that forms two throttle sections 22 follows. Aperture section 22
Is open at one end face of the bearing casing 7. Second
The passage section 21 of the bypass passage 20 as well as a further passage section 24 are also open at the end face 23 of the bearing casing 7. The passage section 24 corresponds to the first passage section 21 in the flow direction.
Are arranged in the opposite direction. This passage section 24 communicates with the discharge passage 14 at the end opposite to the end surface 23 of the bearing casing 7.

The second bypass passage 20 has a substantially rectangular cross section. Since the bypass passage 20 is open on the end face 23 side of the bearing casing 7, it can be easily formed in the bearing casing 7 by casting.

In order to obtain a good effect taking into account the cold start of the pump, the surface and the throttling passage, which are determined by the length and the cross section of the second bypass passage 20 and are wetted by the hydraulic oil flow sent to the actuator. The ratio of 12 to the cross section is about 1
It is set larger than 3: 1.

The above arrangement and construction of the second bypass passage 20 according to the invention results in a very good viscosity response of the pump, which leads to a good cold start mode.

[0023]

According to the present invention, the cold start mode of the positive displacement pump can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a positive displacement pump.

FIG. 2 is a partial cross-sectional view taken along line II-II in FIG.

FIG. 3 is an enlarged partial sectional view taken along line III-III in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Pump component 3 Rotor 4 Cam ring 5 Vane 6 Drive shaft 7 Bearing casing 8 Control plate 9 Control plate 10 Discharge port 11 Discharge chamber 12 Restrictor passage 13 Hole 14 Outlet passage 15 Spring chamber 16 Spring 17 Adjustment piston 18 Bypass Passage 19 Control edge 20 Second bypass passage 21 Passage section 22 Restricted section 23 End face 24 Passage section

Claims (6)

[Claims] 1. A positive displacement pump, such as a vane pump or a roller pump, wherein a discharge chamber (10A) of the pump has an adjusting piston (17) slidable therein against the force of a spring (16). Via a hole (13) and a bypass passage (18) provided substantially in parallel with the hole within the range of the hole (13), the spring chamber (15) and the outlet passage (14) of the adjusting piston (17) are connected. A flow regulating valve (11), which is always connected and has a piston (11A) loaded with a spring force, is arranged to regulate the effective flow rate, and the regulating piston (17) is provided with a spring chamber (15). In which the open cross-section of the throttle passage (12) connecting the outlet passage (14) to the outlet passage (14) is controlled in relation to the delivery flow of the positive displacement pump, the throttle passage (12) and the outlet passage (14) Between the second bypass passage (20) The second bypass passage (20) is provided with an outlet passage (1).
A positive displacement pump characterized in that the pump is bypassed from 4) and is guided to an outlet passage (14) after passing through a throttle section (22). 2. The positive displacement pump according to claim 1, wherein the second bypass passage has a substantially rectangular cross section. 3. The second bypass passage (20) comprises a first passage section (21), a throttle section (22) and a second passage section (24), the first passage section (21). Branches off from the outlet passage (14), the second passage section (24) leads to the outlet passage (14) and the throttle section (22) connects these two passage sections (21, 24) to one another. The positive displacement pump according to claim 1, wherein: 4. The ratio of the cross-section of the throttle passage (12) to the surface, which is determined by the length and cross-section of the second bypass passage (20) and is wetted by the oil flow sent to the actuator, is approximately 13 The positive displacement pump according to any one of claims 1 to 3, wherein the ratio is larger than 1: 1. 5. The second bypass passage (20) is arranged in a pump casing part (bearing casing 7) in which an adjusting piston (17) and a flow regulating valve (11) are arranged. The positive displacement pump according to any one of claims 1 to 4. 6. The pump according to claim 5, wherein the second bypass passage (20) is open at least in the region of the throttle section (22) toward the end face (23) of the pump casing part. Displacement pump.