Power plants – Pressure fluid source and motor – Pulsator
Patent
1997-10-21
1999-03-09
Nguyen, Hoang
Power plants
Pressure fluid source and motor
Pulsator
60588, 60589, B60T 1120
Patent
active
058785752
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a master cylinder, in particular for hydraulic automotive vehicle brake systems.
In U.S. Pat. No. 5,187,934, for example, a master cylinder is disclosed which includes a piston movable therein, which is sealed relative to a pressure chamber by way of a sealing element fixed on the housing, the pressure chamber being connectable to an unpressurized supply chamber by multiple transverse bores provided in the piston. It is a disadvantage in the prior art master cylinder that transverse bores in the piston must be deburred in order to avoid damage to the sealing element when overriding the transverse bores. Also, many small-diameter bores are required to permit a high amount of fluid flow without causing damage to the sealing element. A large-diameter bore would permit a high amount of fluid flow, however, would increase the risk of destroying the sealing element and cause a large lost travel.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a generic tandem master cylinder which permits a high amount of fluid flow through the transverse bores without increasing the risk of destroying the sealing element.
According to the present invention, this object is achieved by a master cylinder having transverse bores that open into at least one groove provided on the outer surface of the piston. The groove is used to increase the flow cross-section. The groove, or a plurality of grooves, can extend either in an axial direction, or over part of the periphery of the outer piston surface. The formation of burrs at the port of the transverse bore is of little interest because the port is placed in the groove. Possible burrs do not get into contact with the sealing element, thus, wear or damage to the sealing element is effectively prevented.
Because of its symmetric shape, a circumferential groove is particularly easy to manufacture. A groove of this type also permits a maximum expansion of the flow cross-section and, thus, a slow velocity of flow of the hydraulic medium along with a high amount of fluid flow.
A slight inclination of the lateral surfaces of the groove with respect to the outer surface of the piston causes little impairment of the sealing element when it is overridden by the groove. An inclination of approximately 30.degree. has proved especially suitable because the lateral surfaces are sufficiently flat in this case, i.e., the transition is sufficiently smooth, and an appropriately large fluid flow cross-section is achieved in addition. However, equally good properties are achieved with a discrepancy from this value of about .+-.15.degree.. It is particularly favorable to configure the cross-section of the groove as a V, with the legs of the V being at an obtuse angle relative to each other. This achieves good properties and a simple manufacture.
The expanded cross-section achieved by the groove of the present invention necessitates only a small number of transverse bores with a correspondingly large cross-section. The cross-section of the transverse bore may be large because, at its port on the outer surface of the piston, the sealing element is not impaired due to the groove of the present invention. Two transverse bores, which lie preferably on one axis, can be manufactured particularly easily, for example, by drilling in one operation. Four bores also bear this advantage. It is even simpler to manufacture one single transverse bore.
A particularly large cross-section and a small axial extension of the transverse bore with respect to the piston axis is achieved when the transverse bore has a slotted shape. A transverse bore of this type is easy to manufacture in punching or injection-molding operations. Transverse bores with an oval cross-section, for example, are also possible.
When the supply chamber is provided in a guide element which guides the piston, the guide element has radial recesses on the side facing the piston according to the present invention.
The recesses are separated from each other i
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patent: 5046315 (1991-09-01), Nakamura
patent: 5063743 (1991-11-01), Mori et al.
patent: 5187934 (1993-02-01), Mori
patent: 5251446 (1993-10-01), Mori
Konig Harald
Kreh Heinrich
ITT Manufacturing Enterprises Inc.
Nguyen Hoang
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