Bleed valve

This application claims priority from German Application Serial No. 10 2004 007 750.9 filed Feb. 18, 2004.

The present invention relates to a bleed valve.

In infinitely variable change-speed gears, according to the state of the art, the selector valve is generally arranged separately from the hydraulic control unit, which is arranged in the oil pan in a separate selector valve housing in the upper region of the transmission. The connection between the hydraulic control unit and the selector valve housing, as well as between the selector valve housing and the forward clutch and the backward brake, is established by pipes. When the transmission is shut off, oil can disadvantageously leak from the connecting pipe between the selector valve and the forward clutch, because in the parking position P, the upper end of the line is open via a bleed valve and on the lower end, oil can escape into the primary shaft via a rectangular ring and a bleed bore arranged behind it. The amount of air, which reaches the line due to this process and is pushed into the clutch when engaging a gear for the first time after starting, fluctuates drastically and, therefore, has a negative effect on the shifting comfort and the shift adaptation.

It is the object of the present invention to create a device, which prevents oil from escaping from an end comprising a bleed valve of a connecting pipe containing fluid, especially hydraulic fluid, particularly of the connecting pipe between the selector valve and the clutch to the front in an infinitely variable change-speed gear.

Integrate of a non-return function into the bleed valuve is suggested; the bleed valve, proviced at the end of the connecting pipe, is generally designed to be a thermal valve. In doing so, the end of the line is closed with a non-return valve in order to prevent oil or hydraulic fluid from escaping wherein, for space reasons, the non-return valve has very small dimensions and opens already at low pressure levels (<0.5 bar ) in the case of a connecting pipe vetween the selector valve and a clutch, so that the residual pressure remaining in the clutch does not lead to engagement of the clutch. With the bleed valves arranged at the end of the connecting pipe, it preferably concerns a thermal valve, which adjusts the bleed cross-section dependent on the temperature.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a preferred embodiment of the present invention;

FIG. 2 is a top view onto the embodiment pursuant to FIG. 1 , in which the valve openings are shown; and

FIG. 3 is a top view onto the embodiment pursuant to FIG. 1 in the assembled state.

In the embodiment illustrated in the Figures, the bleed valve, designed as a thermal valve 1 , comprising at least two valve openings 2 , 2 ′, as well as a thin spring metal sheet 3 , which serves as a non-return plate and is arranged on a surface in a cover 4 of the thermal valve 1 above and around the valve openings 2 , 2 ′. Within the framework of the illustrated exemplary embodiment, one valve opening 2 is designed as a variable valve and one valve opening 2 ′ is designed as a fixed valve; it is also possible to provide several valve openings. Alternatively, only one variable valve opening can be provided.

Furthermore the spring metal sheet 3 is fixed on the cover 4 of the thermal valve with another component 5 , which is referred to in the following as a stop. According to the invention, the stop 5 prevents the plastic deformation of the spring metal sheet 3 during the bleeding process. The cover 4 and the stop 5 are preferably made of plastic. According to FIGS. 1 and 3 , the stop has a cross-shaped design, however, other designs are feasible as well.

1 thermal valve

2 valve opening

2 ′ valve opening

3 spring metal sheet

4 plastic cover of the thermal valve

5 stop