GB2463650A

GB2463650A - Cast piston chamber housing

Info

Publication number: GB2463650A
Application number: GB0817068A
Authority: GB
Inventors: William Jonak; William Guichard
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2008-09-18
Filing date: 2008-09-18
Publication date: 2010-03-24
Also published as: GB0817068D0

Abstract

A cast piston chamber housing 1 comprising a piston chamber (2, Fig. 2) and a cavity (5, Fig. 1a) which has a fluid inlet (4, Fig 1a), the cavity (5, Fig. 1a) being closed by a plate 6 that has a first part 7 extending from one wall of the piston chamber (2, Fig. 2) to an opposite wall and a second part 9 located in the cavity (5, Fig. 1a), the plate 6 comprising a passageway 10 via which fluid can be applied against a piston 3. The first part of the plate 7 is located in the piston chamber (2, Fig. 2) by means of lip seals 8 and the second part of the plate 9 is provided with an O-ring 11 by which it is sealed against the cavity wall.

Description

DESCRIPTION

Casting piece The invention concerns a casting piece with a piston chamber in which a fluid is to be applied against a moveable piston, the piston chamber being provided with at least one cavity in which a fluid inlet is placed.

Casting pieces are widely used, especially in the field of automotive, because of their mechanical and thermical resistance. Piston chambers in engines and in transmissions are generally casting pieces. However, casting pieces also present one major inconvenient which is their important specific weight. With increasing fuel prices, mass reduction of vehicles becomes more and more important.

Mass reduction in casting pieces is generally performed by providing the casting piece with cavities. Due to the intelligent structure given to the casting pieces, the solidity of the casting piece suffers generally not or only slightly from the cavities, but the weight of the whole piece diminues considerably.

However, the hydraulic volume is often increased by the cavities in the casting piece. If there is a cavity in a casting piece with a piston chamber and the cavity is placed between the inlet and the piston for example, much more fluid has to be entered into the piston chamber until the piston is actioned. With other words, the dead volume increases due to the weight-saving cavity and the reactivity of the system diminues. An other inconvenient resides in the fact that for hydraulic systems a higher quantity of oil is needed which increases both the mass of the vehicle and the maintenance costs.

It is therefore an objective of the present invention to provide a casting piece with a piston chamber which has at least one cavity without the above-mentioned inconvenients of loss of reactivity and of increase of fluid quantity.

This objective is achieved according to the invention in that the cavity is closed with a plate, the plate having an upper part extending from one wall of the piston chamber to the opposite wall and a lower part filling out at least partially the cavity and being provided with a passageway for the fluid to be applied against the piston.

This allows the fluid to enter the piston chamber via the inlet, to pass through the passageway of the plate in order to be applied against the piston. By this way, the dead volume of the piston chamber which was due to the cavity therein can be significantly decreased so that reactivity of the system improves and the hydraulic volume is much smaller than before. In consequence, the needed fluid volume decreases.

This invention allows at the same time to save weight by providing a cavity in the casting piece and to keep the same reactivity as if there was no cavity.

According to an improvement of the invention, the upper part of the plate is maintained by lip seals on both sides thereof.

The lip seals are dimensioned in order to maintain the plate when being pushed into the piston chamber. At the same time, the lip seals assure lateral sealing of the plate.

In an other embodiment of the invention, the lower part of the plate is provided with an 0-ring assuring lateral sealing between the lower part and the walls of the cavity.

This 0-ring prevents fluid to pass from the fluid inlet along the side walls of the lower part of the plate and to disturb the central fluid flow directed vertically to the piston in order to action it.

The invention is explained in the following in detail with reference to the figures in which FIGURE 1 a shows a casting piece with a piston chamber with a cavity according to

the prior art,

FIGURE lb shows a casting piece with a piston chamber with a cavity according to the present invention, FIGURE 2 shows a detailed view of the piston chamber according to FIGURE ib, FIGURE 3a shows a view in perspective of the piston chamber according to the

prior art and

FIGURE 3b shows a view in perspective of the piston chamber according to the invention.

The FIGURE 1 a shows a casting piece 1 with a piston chamber 2. In this piston chamber 2, a piston 3 is moveably arranged. A fluid, for instance oil, enters the piston chamber 2 trough a fluid inlet 4 and applies pressure on the piston 3. In order to save weight, the area between the fluid inlet 4 and the piston 3 is designed as a cavity 5. However, this cavity 5 does not only allow to reduce the weight of the casting piece 1, but also forms a dead volume in front of the piston 3 thereby increasing the reaction time. A higher amount of fluid has to enter the piston chamber 2 in order to apply pressure onto the piston 3.

FIGURES lb and 2 show the same casting piece I after modification according to the present invention. A plate 6 has been placed in the piston chamber 2 right in front of the piston. Its upper part 7 is maintained by lip seals 8 on each side of the plate 6. The lip seals 8 are dimensioned in order to maintain the plate 6 when being pushed into the piston chamber 2. At the same time, the lip seals 8 assure lateral sealing of the plate 6.

Its lower part 9 extends into the cavity 5 and fills it out thereby reducing the dead volume. A passageway 10 extends through the lower part 9 of the plate 6 allowing the fluid to pass from the fluid inlet 4 to the piston 3. In the lower part 9 of the plate 6, an 0-ring 11 prevents fluid to pass from the fluid inlet 4 along the side walls of the lower part 9 of the plate 6 which would disturb the central fluid flow directed vertically to the piston 3 in order to action it. As a result, there is only a small hydraulic volume between the plate 6 and the piston 3 so that reaction time of the system is low.

FIGURE 3a shows a view in perspective of the system according to the prior art. It can be seen from this figure that there is dead volume due to cavities 5 in the casting piece 1.

As can be seen from FIGURE 3 b, the piston chamber 2 and its cavities 5 have been closed by a circumferential plate 6 so that the dead volume has decreased significantly. The fluid flow passes through a passageway 10 in the lower part 9 of the plate 6 so that the hydraulic volume between the plate 6 and the piston 3 is small and the reactivity of the system is high.

Claims

CLAIMS1. A casting piece (1) with a piston chamber (2) in which a fluid is to be applied against a moveable piston (3), the piston chamber (2) being provided with at least one cavity (5) in which a fluid inlet (4) is placed, characterized in that the cavity (5) is closed with a plate (6), the plate (6) having an upper part (7) extending from one wall of the piston chamber (2) to the opposite wall and a lower part (9) filling out at least partially the cavity (5) and being provided with a passageway (10) for the fluid to be applied against the piston (3).
2. The casting piece of claim 1, wherein the upper part (7) of the plate (6) is maintained by lip seals (8) on both sides thereof
3. The casting piece of claim 1, wherein the lower part (9) of the plate (7) is provided with an 0-ring (11) assuring lateral sealing between the lower part (9) and the walls of the cavity (5).