FR2953568A1 - Piston pump for brake installation of vehicle, has inlet valve placed on piston and provided with blocking body that is held by spring element, where spring element forms unit with sealing element - Google Patents

Abstract

The pump (10) has a sealing element (48) ensuring radial sealing of a piston (16) with respect to a cylinder (14). An inlet valve (18) is placed on the piston, and is provided with a blocking body (51) that is held by a spring element (50), where the spring element forms a unit with the sealing element. The spring element is realized in a form of a spring blade in a spring (46) having a segment that is directed axially from the sealing element. The sealing element, the spring element and the blocking body are made of a single piece in plastic material.

Description

FIELD OF THE INVENTION The present invention relates to a piston pump comprising a piston, a sealing element ensuring the radial sealing of the piston with respect to the cylinder and an inlet valve on the piston, and which comprises a shutter member. State of the art The known vehicle brake installations comprise a unit or a hydraulic module for dosing the brake pressure. This module comprises a pump, generally in the form of a piston pump whose piston slides in a cylinder. The piston slides in a two-stroke mode. In the first stage the liquid to be transferred for example the brake fluid is sucked through the inlet valve. In the second stage, the liquid is discharged through an outlet valve. The piston is sealed from the inner casing surface of the cylinder by a sealing member and this sealing member describes the cylinder during its translational movement. For example, such a piston pump is known from DE 10 2005 017 131 A1. FIGS. 1 and 2 show a piston pump 10 according to the state of the art including, among other things, a piston device 12 formed of a cylinder. 14 which receives a sliding piston 16. The piston device or assembly 12 further comprises an inlet valve 18 and an outlet valve 20. The valves 18, 20 allow the piston 16 during its translational movement in the cylinder 14, withdrawing liquid through the inlet 22 to the high pressure chamber or the high pressure zone 24 inside the cylinder 14 and then discharging this liquid through an outlet 26, under pressure, out of the high pressure zone 24. The fluid is mainly brake fluid. The piston 16 is prestressed by spring in the axial direction by means of a return spring 28 installed in the high pressure zone 24. The return spring 28 is supported by its left side according to Figure 1 against the front surface of the cylinder 14 and pushes by its right end against a spring support 30. The spring support 30 is fixedly coupled to the piston 16 so that the

2 return spring 28 pushes against the piston 16 via the spring support 30. A sealing member 32 provided between the piston 16 and the cylinder 14 seals the high pressure zone 24 in the cylinder 14. The sealing member 32 has an annular shape and joins the outer casing surface of the piston 16. By this envelope surface, the sealing member 32 is fixedly held by a valve cage or valve housing 34 fitted on the piston 16 and receiving the inlet valve 18. The spring support 30 in the form of a shoulder is formed on the valve housing 34. The sealing member 32 thus held is radially biased towards the interior against the inner surface of the cylinder 14 to slide and seal. The valve housing 34 has a cup shape constituting a cage receiving inside a return spring 36 of helical shape which bears against the closure member 38 in the form of a ball. The closure member 38 thus applies (in the operating state shown in FIGS. 1 and 2) against a valve seat 40 made on the end face of the piston 16. The closure member 38 is raised from the valve seat 40 against the force developed by the return spring 36 when the piston 16 is pulled to the right out of the cylinder 14 according to Figure 1. During this movement, the inlet valve 18 opens and liquid is sucked into the high pressure zone 24.

The sealing element 32 according to FIGS. 1 and 2 has a base body 42 of essentially rectangular cross section, on which a sealing lip 44 is turned towards the high pressure zone 24. Aim of the invention The present invention is intended to develop a vehicle brake system comprising a piston pump whose behavior of the opening and closing of the inlet valve is improved while being more economically feasible. DESCRIPTION AND ADVANTAGES OF THE INVENTION For this purpose the present invention relates to a piston pump of the type defined above characterized in that the organ

3 shutter is held by a spring element integral with the sealing member. The piston pump according to the invention is made more economically thanks to this one-piece component, formed by the spring element and the sealing element, compared to two separate components. The pump according to the invention also has other advantages. Thus, it considerably simplifies, in particular, the mounting of the closure member because it can be stabilized in position, in a very simple way even during assembly thanks to the elastic spring element. In addition, the spring element can serve the sealing element to detect the position in an automatic mounting installation. The one-piece embodiment comprising the spring element and the sealing element is also advantageous for the characteristics of the elastic material used for this purpose. Thus, the piston pump according to the invention has made it possible to select an elastic material which, on the one hand, provides a particularly advantageous seal and, on the other hand, allows excellent compression behavior of the closure member. According to an advantageous development of the piston pump according to the invention, the spring element is a leaf spring having in particular a first segment directed axially from the sealing element and a second adjacent segment, directed essentially in the direction radial. Such leaf spring results in an opening and closing behavior defined in a particularly precise manner because the closure element provided on the leaf spring is precisely guided as a hinge. According to another advantageous development of the piston pump according to the invention the closure member has a substantially hemispherical shape and in particular the convex side of the hemispherical shape is turned towards the valve seat forming part of the piston. The hemispherical shape makes it possible to have a closure member of relatively low mass. This low mass and the resulting low inertia have an advantageous effect on the

4 opening and closing acceleration behavior. The closure member is sealingly applied against its valve seat even in the case of small positional deviation. In addition, this shutter member is advantageously pushed by the pressure applied on its substantially plane side, which makes it possible to close the valve seat with a very fast reaction. According to another development of the piston pump according to the invention, the substantially flat side of the hemispherical shape comprises a central cavity.

The cavity further reduces the mass of the closure member and furthermore constitutes a surface of very advantageous shape for the pressure exerted by the liquid during the closing phase of the inlet valve. According to another advantageous development of the piston pump of the invention, the sealing element and the spring element and the closure member are made in one piece of plastic material. The targeted choice of a plastics material that is sufficiently strong in its shape and sufficiently elastic enables the three parts constituted by the sealing element, the spring element and the shut-off member to be produced in one piece. during a single manufacturing operation. Such an embodiment is based in particular on the discovery that the requirements relating to the material to ensure elastic sealing between the piston and the cylinder, to ensure elastic sealing with the inlet valve and finally to ensure the elastic guidance of the shutter member are close conditions. According to the invention these conditions are achieved by a single type of material. According to another advantageous development of the piston pump of the invention, the sealing element comprises a spring support for the return spring which supports the piston relative to the cylinder. Such a spring support allows a particularly compact installation of the return spring which can be both long enough and a sufficiently large diameter. This spring makes it possible to develop important restoring forces for a small space requirement. According to another advantageous development of the piston pump according to the invention, the sealing element has an axial groove open towards the high pressure zone of the piston / cylinder assembly. When the piston pump is operating, the pressure in the high pressure zone can reach the open axial groove towards the high pressure zone in the piston / cylinder assembly, and this groove can thus widen. At the same time, the outer radial portion of the sealing element, that is to say the portion located radially next to the axial groove can be forced towards the inner wall adjacent to the cylinder. Thus, as the pressure increases in the high pressure zone, the expansion of the sealing element against the cylinder is amplified and the seal is improved. At the same time the behavior of the piston with respect to the leaks and furthermore the guidance of the piston in the cylinder is improved. According to another advantageous development of the piston pump according to the invention, the side of the sealing element facing the piston is stepped.

The stepped shape of the sealing member results in a relatively large contact area between the piston and the sealing member. This important contact surface improves the conditions for fixing the sealing element. This sealing element can be fixed in particular by its application under pressure against the axially directed flanks of the shoulders or stepped parts. At the same time at the flanks there will be a centering of the sealing element relative to the piston. The flanks of the stepped portions, radially directed serve to support the sealing member against the piston which is particularly advantageous when returning the piston by the return spring described above. According to another advantageous development of the piston pump according to the invention, the sealing element envelops the piston. This enveloping structure of the sealing element around a portion of the piston, particularly at a step, a groove or a fillet of the piston, is such that the sealing element

6 clings to the piston in the axial direction by a peripheral segment or peripheral attachment means. A shape connection is thus made between the piston and the sealing element and this connection allows a good realization and a good pre-assembly thanks to the easily elastic characteristics mentioned above of the material of the sealing element. for automatic manufacture. In addition the piston is advantageously in two parts having a first portion facing the drive means and a second portion facing the sealing member. Each of the parts of the piston thus made in two parts will have particular functions. Thus the first part transmits the drive thrust to the second part which ensures the entry of the liquid including brake fluid into the inlet valve. The high pressure zone inside the cylinder is then delimited by the sealing element and separated in a sealed manner with respect to the low pressure zone. The second part of the sealing element thus slides in the cylinder and is itself pushed by the first part. The return is ensured by the return spring by transmitting the restoring forces via the sealing element and the second part on the first part. The different parts can be optimized in a simpler way for the choice of the material than the possible manufacturing processes, compared to what would be possible for a piston in one piece. It is furthermore advantageous if the first part is a solid cylinder and the second part is a hollow cylinder. The first part in the form of a solid cylinder is made in a very economical manner and makes it possible to transmit the particularly large thrust forces. It is advantageous to make it plastic material preferably reinforced with fibers. The second portion in the form of hollow cylinder may advantageously be made as such as blank with a cylindrical cavity. The second part is preferably made of metal and especially as sintered part or as part manufactured by deep drawing. It suffices to provide at least one radial opening in such a part through which, when the piston pump is operating, the liquid to be sucked can arrive radially from the outside inwards toward the inlet valve. The object set by the invention is also provided by a vehicle brake installation equipped with such a piston pump 5 thus offering the advantages already stated above. Drawings The present invention will be described hereinafter in detail with the aid of an exemplary embodiment shown in the accompanying drawings in which: FIG. 1 is a longitudinal section of a piston pump according to the state of FIG. 2 is an enlarged view of detail II of FIG. 1; FIG. 3 is a longitudinal section of a first exemplary embodiment of a piston pump according to the invention; FIG. 4 shows the enlarged scale detail IV of FIG. 3, and FIG. 5 is a perspective view of a mounting consisting of a closure member, a spring element and a corresponding sealing element. FIGS. 3 and 4 show a piston pump 10 according to the invention. The piston pump comprises a piston assembly 12 with a cylinder 14 receiving a sliding piston 16. The pump has an inlet valve 18 and an outlet valve 20. The piston 16 is resiliently biased by a return spring 28 in the high pressure zone 24; the return spring 28 pushes a spring support 46 fixedly coupled to the piston 16 according to the invention. A sealing member 48 is provided between the piston 16 and the cylinder 14; this sealing element is fixedly held on the piston 16 and slides along the inner casing surface of the cylinder 14. The sealing element 48 is formed in one piece with a spring element 50 according to the invention. invention that holds the closure member 51. The one-piece embodiment of the spring element 50 with the sealing element 48 allows an axially very short construction, more compact than in the state of the art and with durations

8 particularly short reaction to the opening and closing of the closure member 51 relative to the corresponding valve seat 40. A return spring 28 applied against the spring support 46 provides the additional prestressing of the sealing element 48. The return spring 28 has a radial bearing surface, very wide as a spring support 46. According to 4, the sealing element 48 is provided with an axial groove 52 open towards the high pressure zone 24. The axial groove 52 has a corresponding length in the high pressure zone 24 while being subjected to the liquid under pressure . The axial groove 52 is pushed radially outwardly by the liquid at its two inner side surfaces or flanks 54, 56 which face each other. In particular, the lip-shaped portion or segment 58 of the sealing element 48 which is radially outwardly for the axial groove 52, and which may also be called the sealing lip, is supported radially towards the outside. against the inner casing surface of the cylinder 14. Thus, as the pressure increases in the high pressure zone 24, this segment 58 of the sealing element 48 bears more strongly against the cylinder 14 and ensures better sealing. Furthermore, this improves the guiding of the piston 16 in the cylinder 14. In the embodiment of FIG. 3, the piston 16 is in two parts, namely a first part 60 and a second part 62. The first part 60 is a rod-like structure, cylindrical solid, injected plastic and specially adapted to transmit the axial thrust of an eccentric drive (not shown) on the second portion 62 and thus on the sealing member 48. The second portion 62 is a sintered hollow cylinder, both ends of which have a shoulder or step 64, 66. The step 64 includes the first portion 60 having an outer radial end region; the first part 60 is fixed by a force connection by the fitting pressed inside the shoulder 64. The shoulder 66 adjacent to the sealing element 48 is surrounded by it, radially by the outside in the axial direction. A segment

9 68 of the sealing member 48 which constitutes the core, is applied radially outwardly against the shoulder 66 and forms with it a pressed fit. Another segment 70 of the sealing element 48 which is located radially quite outside, surrounds a kind of arm or sleeve of the shoulder 66 of the second part 62. This segment 70 comprises several periphery hooks 72 which hook behind the outer radial zone of the shoulder 66 and in this way form a connection by the shape in the axial direction with the second portion 62.

Figures 4 and 5 further show the unit made in one piece comprising the sealing member 48, the spring member 50 and the closure member 51. The spring element 50 of the element substantially annular seal 48 is located firstly as a leaf spring with the first segment 74 in the axial direction of the piston 16. This first segment 74 is continued by a second segment 76 which extends substantially radially; this latter segment has a radial shape slightly inclined in the case of the embodiment shown.

The second segment 76 carries a closing spring 51 which has a substantially hemispherical shape and thus has a curved upper surface 78 facing the valve seat 40. In contrast, the closure member 51 has a limiting surface 80 substantially flat, with central cavity 82.25 NOMENCLATURE OF MAIN ELEMENTS 10 piston pump 12 piston assembly 14 cylinder 16 piston 18 inlet valve 20 outlet valve 22 inlet 24 high pressure zone 26 outlet 28 return spring 30 spring support 32 sealing element 34 valve housing 36 return spring 38 closure member 40 valve seat 46 spring support 48 sealing element 50 spring element 51 closure member 52 axial groove 54 sidewall flank 56 flank the axial groove 58 lip-shaped segment of the sealing element 60 first portion of the piston 62 second portion of the piston 64 shoulder 66 shoulder 70 segment of the element sealing member 72 fastening member 74 first segment of the closure member 76 second segment of the closure member 78 convex upper surface

Claims (1)

CLAIMS1 °) Piston pump (10) comprising a piston (16), a sealing element (32, 48) providing radial sealing of the piston (16) with respect to the cylinder (14) and a valve inlet (18) on the piston (16), and which comprises a closure member (38, 51), pump characterized in that the closure member (51) is held by a spring element (50) making body with the sealing member (48). 2) piston pump according to claim 1, characterized in that the spring element (50) is in the form of a leaf spring in particular in the spring having a first segment (74), axially directed from the sealing element (48) and a second segment (76), adjacent to the first, and which is directed substantially radially. 3) piston pump according to claim 1, characterized in that the closure member (51) has a substantially half-sphere shape, and in particular the curved side (78) of the half-sphere shape is rotated to a valve seat (40) forming part of the piston (16). 4) piston pump according to claim 3, characterized in that the substantially planar side (80) of the hemispherical shape comprises a central cavity (82). Piston pump according to Claim 1, characterized in that the sealing element (48) and the spring element (50) as well as the closure element (51) are made in one piece. made of plastic 6. Piston pump according to claim 1, characterized in that the sealing element (48) has a spring support (46) for the return spring (28) of the piston (16) supporting on the cylinder (14). 7 °) piston pump according to claim 1, characterized in that the sealing element (48) has an axial groove (52) open towards the high pressure zone (24) of the piston / cylinder assembly (16, 14) . 8 °) piston pump according to claim 1, characterized in that the sealing member (48) is stepped (66) at its side facing the piston (16). Piston pump according to Claim 1, characterized in that the sealing element (48) has a shape (70, 72) surrounding the piston (16). 10 °) Vehicle brake installation comprising a piston pump (10) according to one of claims 1 to 9, characterized in that the pump (10) comprises a piston (16), a sealing element (32) , 48) radially sealing the piston (16) relative to the cylinder (14) and an inlet valve (18) fitted to the piston (16) and having a closure member (38, 51), The closure member (51) being held by a spring member (50) integral with the sealing member (48). 30