JPH0243037B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a casing, a cam ring supported within the casing, a radially slotted rotor driven by a drive shaft, and a rotor slidably fitted within the radial slit of the rotor. The present invention relates to a high-pressure pump, in particular for a power steering device, which has an actuating vane in air-tight contact with the cam ring, and at least one control plate, the pump part being made by pressure casting.

A well-known high-pressure pump of this kind (West German patent no.
Specification No. 2020675 and Specification No. 2047040)
has an integral casing for the pump and oil tank. In this case, the shape of the casing is determined in such a way that rework can be avoided by allowing the casing to be produced by pressure casting. The pump parts housed in the casing pump chamber then consist of a drive-side control plate, a cam ring, actuating vanes which are guided in radial slots in the rotor and can be moved radially outwards and abut against said cam ring, and on the discharge side of the pump. It consists of a separate control board provided. Since the control plate on the discharge side is subjected to conveying pressure during operation of the pump, all pump parts are tightly pressed together and supported in the casing via the control plate of the drive shaft. In order to obtain good wear resistance due to the relatively high pressing forces and the resulting sliding friction, the control plate is made of a sintered alloy. Although this sintered alloy control plate has the advantage of satisfying high requirements for shape accuracy and dimensional accuracy, it has the disadvantage of high manufacturing cost.

An object of the present invention is to reduce the manufacturing cost and weight of this type of high-pressure pump while sufficiently maintaining conventionally applied standards regarding wear resistance, shape and dimensional accuracy, and liquid tightness. .

This object, according to the invention, is to provide a high-pressure pump of the type mentioned at the outset, in which at least one control plate is made of a high-silicon-containing alloy made by vacuum casting, the flatness of which does not require reworking. in
This is achieved by being 0.1 mm or less.

Advantageous embodiments of the high-pressure pump according to the invention are described in the claims 2 to 4.

According to the above-mentioned West German Patent No. 2047040,
Although it is known that high-pressure pump casings can be made by pressure casting, the use of control plates made by pressure casting has traditionally been opposed with great prejudice.
In other words, pressure cast products have less stress than sintered alloys, and cavitation that acts on the control plate.
Pressure castings have heretofore been considered unsuitable materials for this pump component because of the considerable frictional and bending loads. Rather, premature wear of the control plate in the area of the contact surface between rotor and working blades or damage conditioned by small elongation rates were taken into account. This idea is due to the large porosity and void formation in the structure of pressure castings.

Furthermore, if the elastic modulus of the pressure cast product is small, excessive deformation of the control plate will occur during operation, which has been thought to have a detrimental effect on the operation of the pump. However, these expected disadvantages do not actually occur; on the contrary, life tests have shown that the pump according to the invention reaches the values of known pumps in terms of operating performance and wear characteristics. A homogeneous structure with minimal voids and a wear-resistant surface area was obtained by using a control plate constructed of a high-silicon-containing aluminum alloy, which was initially made by vacuum casting. A control board made in this way is considerably less expensive to manufacture, and at the same time the weight is saved.

In order to limit the pressure, the area on which the pressure acts on the discharge side of the control plate is advantageously reduced by the axial packing. This results in a hydraulic end clearance adjustment and prevents overloading of this control plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments of a vane chamber pump shown in the drawings.

The pump casing 1 equipped with reinforcing ribs 1A is
It is constructed of a high silicon-containing alloy made by vacuum casting, in which case the oil passages 2, 3 or 2 are
The drive-side control plate 4 provided with A and 3A is formed integrally with the casing. A drive shaft 5 extends inside the casing 1, and is connected to a rotor 6 via a key. Although not shown in the drawings, the rotor 6 has a number of radial slits into which actuating blades 8, which are movable in the radial direction and are in contact with the cam ring 7, are slidably fitted. There is. A movable control plate 10 is supported on the cam ring 7, and the control plate 10 is provided with discharge ports 11, 11A and arcuate oil passages 13, 13A to the lower side of the actuating blade 8, which act in a well-known manner. ing. The transfer chamber between the working blades 8, that is, the rotor 6 and the cam ring 7
The transfer chamber between the two is connected to an oil tank (not shown) via the suction chambers 15, 15A and the suction port 17. The pressure oil conveyed by the actuating blades 8 is sent through the discharge ports 11 to 11A to a discharge chamber 20 connected to the discharge port 18. The control plate 10 is provided with a groove for the packing ring 21. This sealing ring 21 delimits a predetermined pressure area of the control plate 10 on which the delivery pressure acts, so that the control plate 10 does not sag excessively even at high pump pressures. The discharge pressure acting on the control plate 10 is used to balance the axial play and to balance the internal pressure acting on the control plate 10 from the rotor side.

In a high-pressure pump such as the one according to the present invention, a combination of different materials is used, so the wear load on the control plates 4 and 10 is extremely large. That is, the rotor 6 and operating vanes 8 of the high-pressure pump of the present invention are usually made of steel, while the casing 1 and control plates 4, 10 are made of an aluminum-silicon alloy as in the present invention. During operation of the high pressure pump, the control board 10
is slightly curved in the direction of the drive shaft 5 under the operating pressure acting on the discharge chamber 20, so the end surfaces of the rotor 6 and the operating blades 8 slide on both control plates 4, 10 and come into contact. . As a result, a line contact condition occurs between the actuating vane 8 and the control plates 4, 10, which exposes the control plates 4, 10 to extreme wear loads.

Furthermore, in the case of a high-pressure pump such as the present invention, in addition to such extreme wear loads, cavitation loads also occur. In other words, cavitation caused by pressure oil is
It occurs rapidly in a narrow area between the pressurization area and the suction area of a high-pressure pump, and erodes materials such as control plates.

However, when the control plates 4 and 10 are manufactured from a high-silicon-containing alloy using a vacuum casting method such as die casting as in the present invention, silicon crystals precipitate very finely on the surface of the cast product during rapid cooling, forming a thin boundary layer. In contrast, coarse crystals precipitate in deeper layers in the casting. It has been found that the fine silicon deposits on the surface of the casting form a surface layer that is sufficiently resistant to wear and cavitation. In particular, it exhibits exceptional wear resistance compared to control plates made of sintered alloys. Therefore, in the present invention, this surface layer is used in the vacuum-cast state without being machined.

Despite the high precision required for pump structural parts of this type, control mirrors integrally formed with the control plate or casing made by vacuum casting can be used without expensive rework. Since the flatness of the control plate is less than 0.1mm without reprocessing,
There are extremely few processing requirements for the control mirror surface. Therefore, the fine structure on the surface is maintained and the wear resistance is not impaired.

[Brief explanation of the drawing]

The drawing is a sectional view of a high-pressure pump according to the invention. 1...Casing, 4...Control board, 5...Drive shaft, 6
...Rotor, 7...Cam ring, 8...Working blade, 10...
Control board, 20...discharge chamber, 21...packing ring.

Claims (1)

[Scope of Claims] 1. A casing, a cam ring supported within the casing, a rotor with a radial slit driven by a drive shaft, the cam ring slidably fitted within the radial slit of the rotor; In a high-pressure pump for a power steering device in which the pump body is made by pressurized casting, the pump body has an operating vane in airtight contact with the blade and at least one control plate, and the at least one control plate 10 is A high-pressure pump comprising a high-silicon-containing alloy cast by a vacuum casting method, and characterized in that the flatness of the control plate is 0.1 mm or less in the as-vacuum-cast state. 2 Control board 10 located on the discharge side of the pump
2. The high-pressure pump according to claim 1, wherein the pump is made of a high-silicon-containing alloy cast by a vacuum casting method. 3 The discharge chamber 20 side of the control board 10 is the packing 2
The high-pressure pump according to claim 1 or 2, characterized in that the high-pressure pump has a pressure area partitioned by 1. 4. Any one of claims 1 to 3, characterized in that a control plate 4 integrally formed with a casing 1 is provided on the drive side of the pump, and the casing is cast by a vacuum casting method. The high-pressure pump according to item 1.