JPS6245980A - Hydraulic pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The invention relates to a hydraulic pump comprising a casing having a chamber, a shaft extending into the chamber and having at least one stroke curve, and a shaft directed toward the stroke curve. a pump piston assigned to the pump piston, a pump cylinder assigned to the pump piston, an outlet valve and an outlet valve each assigned to the pump piston, a return spring for pressing the pump piston against the stroke curve, and a pressure limiting device. and when a predetermined pressure limit is established behind the outlet valve, the pump piston is held away from the stroke curve by the pressure limiting device, so that the stroke curve moves away from the pump piston. After that, -1- is drive 1. It's about formal things that disappear.

BACKGROUND OF THE INVENTION In a hydraulic pump suitable for a vehicle brake system, known from DE 28 38 918 A1, the pump piston is pressed against a rotating eccentric by a return spring. The pump cylinder receiving the pump piston has an outlet valve to which a device is connected, in particular for limiting the delivery pressure of the hydraulic pump. This device consists of a complex control valve mechanism and a shut-off cylinder connected to the control valve mechanism and having a shut-off piston. The load of this shut-off piston acts via the piston rod and the end piece, so that the pump piston is moved against the force of the return spring so that it is no longer driven by the eccentric. become. This control valve mechanism and shutoff cylinder and piston are expensive and prone to failure.

Also known from U.S. Pat. No. 2,650,543 is a multistage cylinder-type combination structure consisting of at least two pre-feed pumps and two main feed pumps, which also has a control valve system. This valve mechanism is connected to the output valve of the main pump to control shutoff of the pre-feed pump. These pre-feed pumps each have a multi-stage cylinder and a multi-stage piston, which act on the one hand as a pre-feed piston and on the other hand as a shut-off piston. However, this multi-stage cylinder and multi-stage screws are extremely expensive.

OBJECT OF THE INVENTION The object of the invention is to overcome a series of disadvantages.

Means for Solving the Problems - 1 - According to the present invention, the chamber is formed airtight against I-L forces and is curved relative to the axis; A passage is open in the chamber, which is connected to the outlet valve on the outlet side, and when the pressure limit value is reached, the pressure from the chamber side on the pump piston is affected by the elastic tension of the return spring. The solution is that the corresponding return spring is designed in such a way that this is prevented.

Advantages of the Invention The hydraulic pump according to the present invention has a simple structure consisting of a small number of parts and can be manufactured at low cost.

According to the embodiment according to claim 2, the pump piston is lifted off the cam by a suitable selection of the cam shape, compared to hydraulic pumps with eccentrics of the known type. The impact speed of the cam on the piston in this state can be made as small as possible. This produces less noise and friction.

The exemplary hydraulic pump 2 is a component of a pressure supply device 3 suitable for example for use in a vehicle brake system 4 . This 1l11
The one-pressure pump 2 includes one casing 5 forming a cam chamber 6, two pump cylinders 7, two pump pistons 8, two return springs 9, two artificial valves 10, and two outputs 1.
] It has a valve 11, one camshaft 12, one cam 13, and a drive motor (not shown), which is connected to the camshaft 1.
Force J, + 3 is rotated through 2. Instead of a cam 13 forming a stroke curve, it is of course also possible to arrange an eccentric body and an eccentric rod on the hydraulic pump 2.

Both pump cylinders 7 are arranged coaxially and positioned towards the axis of the camshaft 12 . Each end of each pump cylinder 7 farther from the cam chamber 6 is closed with a cover 14 . Return spring 9 is connected to pump cylinder 7
and is supported by this cover 14. This return spring 9 loads the pump piston 8, which is pushed into the pump cylinder 7, in the direction towards the cam 13. One inlet valve 10 in each case is connected to each pump cylinder 7 and, on the other hand, to a pressure medium reservoir 15 . Similarly, one Yamaguchi valve 11 is connected to each pump cylinder 7, and this outlet valve 11 is connected to the casing 5.
It is connected to the force chamber 6 via respective passages 16 formed therein. Additionally, via a connection 17 formed in this housing 5, a connection line 18 supplies a pressure storage chamber 19 and a vehicle brake system 4 or another pressure medium receiver. A not-illustrated knob is arranged between the camshaft 12 and the casing 5 to prevent pressure medium from flowing out along the camshaft 12.

The camshaft 12 will now be described as to the mode of operation of the device according to the invention.
When is driven, the cup 213 is rotated. At this time, as shown in the second half of the drawing, the cam 13 slides one of the pump pistons 8 to the second dead center. cam 1
Further rotation of 3 causes the pump piston 8 to be moved in the direction of the axis 1 of the camshaft 12 by means of the return spring 9. The movement of the pump piston 8 draws pressure medium through the mouth valve 10 from the pressure medium reservoir 15 and pushes it deep into the cam chamber 6 . At this time, the outlet valve 11 is closed.

When the cam 13 rotates further, the pump piston 8 is lifted again, and the pressure medium sucked into the upper pump piston 7 is discharged through the valve 11 and the passage I6 into the cam chamber 6. discharged inside. During the next suction stroke, the return spring 9 forces the pump piston 8 into the cam chamber 6 again, which allows the pressure medium to pass through the outlet connection 17 and the connecting conduit 18 to the empty or partially into the pressure accumulator 19, which is filled only with water, or towards the vehicle brake system 4 or other pressure medium receiver.

A pump piston 8, which is shown on the underside of the camshaft 12, transfers pressure medium in a similar manner from a pressure medium storage vessel 15 to a pressure accumulator 19.
Transport inside. As a result, as long as the vehicle pressure cylinder 4 or other pressure medium receiver is not activated, the pressure accumulator 1
The pressure cuff in 9 increases by -1. As a result, the pressure within the cam chamber 6 also continues to rise by -1-. As the pressure in the cam chamber 6 increases, the depth of penetration of the pump piston 8 into the cam chamber gradually decreases. According to the invention, the spring force of the return spring 9 is designed in such a way that once a predetermined pressure limit value in the pressure accumulator 19 is reached, the pump piston 8 can no longer be displaced relative to the cam 13. has been done. The hydraulic pump 2 is therefore shut off by the pressure built up in the cam chamber 6 when a predetermined pressure limit value is reached, and no special auxiliary means are required for this purpose. There is no need to stop the drive motor. This makes it possible to connect the camshaft 12 in a fixed manner, for example to a drive motor of a motor vehicle or to its wheel drive shaft or cardan shaft.

For example, a one-way valve 20 is first connected to the outlet connection 17 and a connecting conduit 18 is connected to the valve 20;
It is possible to supply the pressure accumulator 19 and the vehicle pressure system 4 through the pressure accumulator 19 . The advantage of arranging this one-way valve 20 is that when the camshaft 12 is not driven, the pressure medium located in the pressure accumulator 19 cannot flow out through the hydraulic pump 2 into the pressure medium storage container 15. It is.

The shape of the cam 13 is selected in such a way that during automatic shutoff of the hydraulic pump 2, the speed at which the cam 13 hits the pump cylinder or cylinders 7'' is lower than when using eccentrics according to the prior art. ing. This lower impact speed also generates less noise and less wear.

[Brief explanation of the drawing]

The drawing is a partial cross-sectional view showing one embodiment of the present invention.

Claims (2)

[Claims] 1. Hydraulic pump, comprising a casing having a chamber, a shaft extending into the chamber and having at least one stroke curve, a pump piston oriented toward the stroke curve, and a pump cylinder assigned to the pump piston. each having an assigned inlet valve and an outlet valve, a return spring that presses the pump piston against the stroke curve, and a pressure limiting device, in which a predetermined pressure limit value is created behind the outlet valve. and in those of the type in which the pump piston is held away from the stroke curve by the pressure limiting device, so that the stroke curve no longer drives the pump piston, the chamber (6) is formed airtight against pressure. and sealed relative to the shaft (12), furthermore a passageway (16) opens into the chamber (6), which is connected on the outlet side to an outlet valve (11) and which is free from pressure. characterized in that the return spring (9) is configured in such a way that when the limit value is reached, the pressure from the chamber side on the pump piston (8) prevents the return spring (9) from being elastically stretched. A hydraulic pump. 2. 2. Hydraulic pump according to claim 1, wherein the stroke curve is formed as a cam (13).