FR2920377A1 - Master brake cylinder for automobile, has lateral surfaces parallel to bore axis, central groove separating longitudinal ribs, and cavities respectively connecting ends of longitudinal holes of ribs to bore - Google Patents

Abstract

The cylinder has lateral surfaces parallel to axis (XX') of a bore of the cylinder, where the cylinder is made of plastic, aluminum or aluminum alloy. The surfaces do not include projections. A plane surface (p1) has transversal holes (tr1, tr2) placed with respect to the axis. A central groove (ra1) separates longitudinal ribs (n2, n3). The ribs are respectively pierced with longitudinal holes (tr3, tr4). Cavities respectively connect ends of the holes (tr3, tr4) to the bore. An independent claim is also included for a method for fabricating a master brake cylinder.

Description

The invention relates to a master brake cylinder and in particular a master cylinder whose outer shape is linear and elongated along the axis of the bore of the master cylinder. The invention also relates to a manufacturing method for producing such a master cylinder. Master brake cylinders known in the art are generally manufactured by molding and then machining (machining the inside of the bore, drilling access holes, etc.). The manufacture of the master cylinders is therefore relatively long and expensive because of the molding operations. In addition, the master cylinders obtained are relatively bulky. The invention proposes a faster and less expensive method of manufacture. This manufacturing mode uses extrusion manufacturing technique using a die. The master cylinders obtained are more compact and less bulky. In addition, being made of extruded material they can be made of a material (such as aluminum or plastic) that will not be the seat of anodization. In addition, the master cylinders can be stronger and harder than those made with a foundry alloy. 2

By extrusion, one will obtain bodies of master cylinders whose walls will not present porosities. We can therefore reduce the thickness of the walls and thus reduce the volume and weight of the master cylinders.

The invention thus relates to a brake master cylinder in which all the side surfaces parallel to the axis of the bore of the master cylinder do not have a protrusion. According to a preferred embodiment of the invention, the right-hand cross section of the master cylinder is generally circular in shape and the master cylinder comprises a flat surface which has at least two holes transverse to the axis of the bore and opening in the bore. Advantageously, the master cylinder comprises a first longitudinal rib and said flat surface is a longitudinal surface belonging to this first rib. It can also be provided that the master cylinder comprises at least one second longitudinal rib, this second rib having at least one longitudinal hole opening into a first cavity of the bore. According to this embodiment, the master cylinder may then comprise a third rib parallel to the second rib and separated from it by a groove, this third rib also having a longitudinal hole opening into a second cavity of the bore. 3

According to this embodiment, the cavity furthest from a first end opposite the inlet bore may comprise a circular groove inside the bore.

It can be provided that at least one of the second or third ribs has at least one hole perpendicular to the longitudinal direction of the ribs. In such a master cylinder, it will be advantageously provided that a first end opposite a second inlet end of the primary and secondary pistons is closed sealingly. For example, it will be provided that the first end opposite the second inlet end of the primary and secondary pistons comprises a cap crimped tightly on the edges of the first end. Said sealing cap will then be advantageously located along the axis of the bore and it may include a cylindrical boss intended to allow the centering of the secondary spring of the master cylinder. Advantageously, such a master cylinder is made of aluminum, aluminum alloy or plastic.

The invention also relates to a method of manufacturing the body of such a master brake cylinder. This method will in principle comprise the following steps: step 1: manufacture of a die having a shape substantially corresponding to the section of the master cylinder to be manufactured;

step 2: extrusion of a material through said die to obtain a profile having a uniform section corresponding to the section of the master cylinder to be manufactured; step 3: cutting in said profile of at least one master cylinder body; a specific length, - step 4: machining the feed holes to be connected to the outputs of a brake fluid supply tank and pressure communication holes to be connected to hydraulic braking circuits. According to one embodiment of this method, the die produced during step 1 makes it possible to produce an axial hole of diameter such that after the extrusion operation of step 2, the profile obtained has an axial hole. corresponding to the minimum diameter of the bore of the master cylinder to obtain or less than this diameter. If this is not the case, the method will provide that after step 2 or after step 3, an axial hole corresponding to the minimum diameter of the bore of the master cylinder body to obtain or less than this diameter is realized in said profile. The method of the invention further provides that after step 3 the finishing of the bore and the machining, within the bore, of the circular housings intended to receive seals are carried out. seals as usually required in master brake cylinders.

In the context of the machining of the master cylinder, it is also expected that, during step 4, at least two longitudinal holes, corresponding to two feed holes intended to be connected to the outputs of a feed tank of brake fluid or two pressure communication holes intended to be connected to at least one hydraulic braking circuit, are drilled in the wall of the master cylinder parallel to the axis of its bore. Also, after step 3, provision is made for at least two cavities to be milled inside the bore and for depths such that each of these cavities may be intersecting with one of said longitudinal holes. According to one embodiment of the method of the invention, it is provided that said axial hole made in the master cylinder, is a blind hole. According to another embodiment of this method, said axial hole is a hole which passes axially through the profile. In this case, said profile has a longitudinal rib 20 on its periphery. The two longitudinal holes are made in said rib. In addition, after step 3 or 4, the rib is machined at the first end of the master cylinder. Then, after step 3 or 4 said first end of the master cylinder is closed sealingly by folding the profile material towards the axis of the bore. According to an alternative embodiment, after step 3 or 4 a plug is sealingly attached to said first end of the master cylinder. 6

Advantageously, this plug is fixed along the axis of the bore. To fix this plug, it is possible to crimp the walls of the first end on the plug.

Or, according to an alternative embodiment, this cap is screwed onto the first end of the bore. Advantageously, it will be provided that said plug has a boss intended to allow the centering of the secondary spring of the master cylinder.

The invention also relates to such a master cylinder, characterized in that the longitudinal holes are drilled in the second and third ribs from the first end of the master cylinder and in that the first cavity or the second cavity furthest said first end is a circular groove inside the bore. The various objects and features of the invention will appear more clearly in the description and in the appended figures which represent: FIG. 1, a general perspective view of a master cylinder according to the invention, FIG. 2a, a view 1b, a longitudinal sectional view of the master cylinder of FIG. 2a, FIG. 3a, an end view of a master cylinder. according to the invention, - Figure 3b, a cross-sectional view of the master cylinder of Figure 3a, - Figure 3c, a cross-sectional view of an alternative embodiment of the master cylinder of Figure 3a, - Figure 4a, an end view of a master cylinder according to the invention, - Figures 4b and 4c, respectively, a first sectional view (section along bb) and a second sectional view (section along cc) of the master cylinder of FIG. 4a; FIGS. 5a to 5c, figures illustrating the procedure manufacturing method by extrusion of a master cylinder according to the invention, Figure 5a illustrating a die for producing master cylinder extrusion, Figure 5b showing a sectional view of a bar in which will be made master cylinders and Figure 5c showing an end view of a master cylinder obtained after extrusion, - Figures 6a to 6d, different manufacturing steps of a method of manufacturing a master cylinder according to the invention according to which Figures 6a and 6b show a master cylinder after extrusion respectively in longitudinal section (Figure 6a) and end view (Figure 6d), and Figures 6c and 3d show a master cylinder after machining in longitudinal section (Figure 6c) and end view (Figure 6d). - Figure 7, a longitudinal sectional view of a master cylinder obtained by the method of the invention, 8

FIGS. 8a to 8d, various steps of sealing the bottom of a master cylinder according to the invention in which FIGS. 8a, 8c, 8d are longitudinal sectional views and FIG. 8b is an end view; Figures 9a and 9b, longitudinal sectional views of a variant of the method of Figures 8a to 8d.

Referring to Figure 1, we will describe a general view of a master cylinder according to the invention. As can be seen in this figure the side walls (or longitudinal) parallel to the axis XX 'of the master cylinder are rectilinear and have no protuberance. The master cylinder has a general cylindrical shape. The inlet of the master cylinder through which are inserted the primary and secondary pistons is referenced MCe. The bottom of the master cylinder (secondary pressure chamber side) is referenced MCf.

The master cylinder has, on its periphery, a first longitudinal rib nl which has a flat surface pl. Two holes trl and tr2 are drilled in this surface p1. These holes pass through the rib ni and the wall of the master cylinder to open into the bore of the master cylinder. These holes will connect the hydraulic braking circuits to the primary and secondary pressure chambers. It is also provided a second and a third longitudinal rib n2 and n3 which are each pierced with a longitudinal hole tr3 and tr4 respectively. These holes are drilled from the MCf end of 9

master cylinder and end, as will be described later, to cavities that communicate with the bore of the master cylinder. These holes will connect a brake fluid reservoir and feed the primary and secondary pressure chambers. In this configuration, an ral groove is provided between the two ribs n2 and n3. This rib will mount a brake fluid reservoir by placing in the groove ral a fastening rib belonging to the tank. A transverse hole tr5 is provided in one of the ribs n2 or n3 and allows using a screw placed in this hole to lock the fixing rib of the brake fluid reservoir. It should be noted that the groove groove provided between the two ribs n2 and n3 is not mandatory and that these two ribs could form a single rib. The mounting of the brake fluid reservoir could then take another form. Figure 2a shows a side view of the master cylinder of Figure 1. As can be seen, the rib ni is off-axis with respect to the axis XX 'of the bore of the master cylinder. The holes tr1 and tr2 are therefore offset with respect to the axis XX '. Figure 2b shows a sectional view of the master cylinder by an axial plane passing between the two ribs n2 and n3. The inside of the bore has been machined so as to reveal the housings (lol to l04) of the various seals necessary for the operation of the master cylinder. In addition cavities fr3 and fr4 have been shown. They allow the 10

connecting the tr3 and tr4 holes to the primary and secondary pressure chamber. The rib n2 is visible in Figure 2b with the hole tr5 for fixing a brake fluid reservoir. Figure 3a shows the master cylinder seen end with the end face MCf visible. We thus see the holes tr3 and tr4 made in the ribs n2 and n3 and which will be used to connect a brake fluid reservoir. The cross-sectional view of FIG. 3b has been made in a plane passing through the axis of the tri-hole. This view shows that the hole trl passes through the rib nl as well as the wall of the master cylinder to end in the bore garlic. This hole has an enlarged inlet to allow the connection of a hydraulic pipe with a nut ensuring sealing in a manner known in the art. Figure 3c shows an alternative embodiment in which the groove ral has an enlargement in the bottom of the groove. This widening will make the master cylinder integral with a reservoir of brake fluid after having locked it with a screw screwed into the hole tr5 (see FIG. 25). The assembly of the tank will be done by sliding, in groove rai, a rib located under its bottom. Referring to Figures 4a to 4c, longitudinal sections of the master cylinder will now be described. FIG. 4b shows a section bb made along a plane passing through the axis XX 'of the bore and by FIG.

the axis of the hole tr3. The hole tr3 is drilled from the end face MCf of the master cylinder opposite the end MCe by which the primary and secondary pistons are inserted into the bore of the master cylinder. This hole tr3 has a depth such that it reaches an area at the beginning of the secondary pressure chamber cps. An internal cavity fr3 connects the end of the hole tr3 to the bore all between the recesses law and lo2 which are intended to receive two seals. This arrangement will feed the secondary pressure chamber through the secondary piston as is known in the art. FIG. 4c represents a section cc made in a plane passing through the axis XX 'of the bore and by the axis of the hole tr4. The hole tr4 is also pierced from the end face MCf. This hole tr4 has a depth such that it reaches an area at the beginning of the primary pressure chamber cpp. An internal recess fr4 connects the end of the hole tr4 to the bore garlic. This arrangement will thus feed the primary pressure chamber through the primary piston as is known in the art. We will now describe a manufacturing method according to the invention of such a master cylinder. Firstly, it is intended to manufacture a bushing FI1 having a cavity FI2 having a shape as shown in FIG. 5a and intended to obtain a profile whose section has the shape of a master cylinder.

We are therefore committed to producing a die whose shape

corresponds to the section of a master cylinder MC to be obtained. A material is then extruded through the FI2 cavity of the FIl die. The material may advantageously be aluminum or an aluminum alloy, or a plastic material intended to become a rigid hard plastic material while cooling. A profiled bar PR is thus obtained as shown in FIG. 5b. In this bar PR, cutting profile elements MC1, MC2, etc., of identical lengths L. All the elements obtained all have a cross section of the same shape as shown in FIG. 5c. These profile elements have, like the master cylinder of Figure 1, a longitudinal rib nl and two longitudinal ribs n2 and n3 separated by a rai groove. In this embodiment, a central hole has been made by extrusion into the profile. This central hole corresponds to the bore all of each master cylinder to obtain. Depending on the accuracy of the extrusion operation which is largely dependent on the nature of the extruded material, the diameter of the central hole may correspond to the diameter of the bore of the master cylinder MC. Section elements are thus obtained as shown in FIGS. 6a and 6b. Each profile element is then machined. If it does not have a central hole, drill this hole. According to the precision and the quality of surfaces obtained for this hole that it was obtained directly by extrusion or that it was obtained by drilling, it is possible to carry out a rectification of the surface 13

bore to achieve the best possible surface quality. Then, the circular housings lol to lo4 are machined to receive the seals (or cups) of the master cylinder. The cavities fr3 and fr4 are also machined to communicate the longitudinal holes tr3 and tr4 with the interior of the garlic bore. Moreover, the transverse holes tr1 and tr2 which open into the bore b1 are drilled as well as the longitudinal holes tr3 and tr4 which must open into the cavities fr3 and fr4. This produces a master cylinder of the type shown in Figures 6c and 6d.

In the case where the bore does not pass right through the body of the profile used to make the master cylinder, the end MCf is naturally closed. The master cylinder obtained corresponds to that shown in FIG.

In the case where the bore passes right through the body of the profile (the case of Figure 6c), to achieve a master cylinder as shown in Figure 1, it should close the MCf end. For this purpose, it is possible, as shown in FIG. 7, to fix a bolt cap sealingly on the end MCf of the master cylinder. This fixing can be done by any appropriate technique: either by screwing the plug at the end MCf, or by press fitting hot or cold, either by welding or by crimping, etc. 14

Figures 8a to 8d show another method of closing the end MCf of the master cylinder. In a zone MCfl of the end MCf, the ribs n1, n2 and n3 are removed and the wall of the master cylinder is thinned (see Figure 8a). Then the thinned wall MCfl is bent toward the axis of the bore as shown in Figure 8c. The MCfl wall by closing completely to the axis of the bore gives rise to a wall MCf2 which closes the end MCf of the master cylinder. The sealed closure of the wall MCf2 can be done by any means known in the art either by partial melting of the material of the wall, or by welding, etc. The process depends on the material used for the master cylinder. This process will find application particularly in the case of a plastic master cylinder. Figures 9a and 9b show an alternative embodiment of the method of Figures 8a to 8d. The thinned wall MCfl having been bent towards the axis of the bore as shown in FIG. 8c, the axial hole tr6 is machined to a determined diameter. A plug bo2 is placed in this hole and is crimped or welded tightly on the wall of the hole. The cap bo2 advantageously has a boss bo3 located along the axis XX 'of the bore. This boss can be used to allow centering of the secondary spring of the master cylinder. The body of a master cylinder thus obtained may be of a material such as aluminum or an aluminum alloy or even a plastic material. It does not present then risk of being the seat of anodization. In addition, in the case of aluminum or an aluminum alloy, a master cylinder body may be harder and stronger than a foundry alloy. The walls of the master cylinder will have almost porosities. They may be thinner. It will therefore be possible to have lighter master cylinder bodies whose dimensions obtained by extrusion will correspond directly to the desired dimensions of the master cylinder.

Extrusion manufacturing will make it possible to overcome the need for specific molds for different customers. Furthermore, the central groove (rai) provided between two longitudinal grooves allows to design an integrated fixing of a brake fluid reservoir on the master cylinder. Such an assembly, with the connection inputs of the brake fluid reservoir to the master cylinder placed at the end of the master cylinder, will provide a compact master cylinder / brake fluid reservoir.

Claims (26)

1. Master brake cylinder characterized in that all its side surfaces parallel to the axis (XX ') of the bore (all) of the cylinder do not have a protrusion. 2. Master cylinder according to claim 1, characterized in that its straight cross section is of generally circular shape (cl) and in that it comprises a flat surface (pl), said flat surface having at least two holes (sorting, tr2) transverse to the axis (XX ') of the bore and opening into the bore. 3 master cylinder according to claim 2, characterized in that it comprises a first longitudinal rib (nl) and in that said flat surface (pl) is a longitudinal surface of this first rib (nl). 4 master cylinder according to one of claims 1 to 3, characterized in that it comprises at least one second longitudinal rib (n2, n3), the second rib having at least one hole (tr3, tr4) longitudinal opening in a first cavity (fr3, fr4) of the bore (all). 5 master cylinder according to claim 4, characterized in that it comprises a third rib (n3) parallel to the second rib (n2) and separated therefrom by a groove (ral), this third rib also having a longitudinal hole (tr4) opening into a second cavity (fr4) of the bore. 17 6. Master cylinder according to claim 5, characterized in that at least one of the second or third ribs has at least one hole (tr5) perpendicular to the longitudinal direction of the ribs. 7. Master cylinder according to claim 5, characterized in that a first end (MCf) opposite a second inlet end (MCe) of the primary and secondary pistons is closed sealingly. 8. Master cylinder according to claim 5, characterized in that a first end (MCf) opposite a second inlet end (MCe) of the primary and secondary pistons comprises a cap (bo2) crimped tightly on the edges of the the first end. 9. Master cylinder according to claim 8, characterized in that the longitudinal holes (tri, tr4) are drilled in the second and third ribs from the first end (MCf) of the master cylinder and in that the first cavity or the second cavity (fr4) furthest from said first end (MCf) is a circular groove inside the bore (all). 10. Master cylinder according to claim 9, characterized in that said sealing plug is located along the axis of the bore and in that it comprises a cylindrical boss, this boss being intended to allow the centering of the secondary spring of the master cylinder. 10 15 18 11. Master cylinder according to any one of the preceding claims characterized that it is aluminum, aluminum alloy or plastic material. 12. A method of manufacturing a brake master cylinder according to any one of the preceding claims, characterized in that it comprises the following steps: - step 1: manufacture of a die (FIl) 10 of a corresponding form substantially at the section of a master cylinder to be manufactured; - step 2: extruding a material through said die to obtain a profile (PR) having a section adapted to the section of the master cylinder to be manufactured, - step 3 : cutting in said profile (PR) of at least one master cylinder of a length (L) determined, - step 4: machining of the feed holes 20 (tr3, tr4) intended to be connected to the outputs of a reservoir brake fluid supply and pressure communication holes (tri, tr2) for connection to hydraulic braking circuits. 25 13. The method of claim 12, characterized in that the die (IFl) made during step 1 allows for an axial hole diameter such that after the extrusion operation of step 2, the obtained profile has an axial hole corresponding to the minimum diameter of 19 the bore (all) of the master cylinder to obtain or less than this diameter. 14. The method of claim 12, characterized in that after step 2 or after step 3, an axial hole corresponding to the minimum diameter of the bore (all) of the master cylinder to obtain or less than this diameter is realized in said profile. 15. Method according to one of claims 13 or 14, characterized in that after step 3 are carried out finishing the bore (all) and machining, inside the bore (all) , circular housings for receiving seals. 16. The method of claim 15, characterized in that, in step 4, at least two longitudinal holes (tr3, tr4), corresponding to two feed holes to be connected to the outputs of a reservoir of brake fluid supply or two pressure communication holes intended to be connected to at least one hydraulic brake circuit, are drilled in the wall of the master cylinder parallel to the axis of its bore (all). 17. The method of claim 16, characterized in that after step 3 are made at least two cavities (fr3, fr4) milled inside the bore (all) and depths such that each is secant with one of said longitudinal holes. 18. Method according to one of claims 13 or 14 or 17, characterized in that said axial hole is a blind hole. 19. Method according to one of claims 13, 14 or 17, characterized in that said axial hole is a hole which passes axially through the profile. 20. A method according to claims 16 and 19, characterized in that said profile comprises a longitudinal rib on its periphery, in that the two longitudinal holes (tr3, tr4) are formed in said rib, and in that after step 3 or step 4 is provided for the machining of this rib at a first end (MCf) of the master cylinder, opposite a second end (MCe) intended to be the input end of the primary and secondary pistons 21. The method of claim 20, characterized in that after step 3 or 4 said first end (MCf) of the master cylinder is closed sealingly by folding the material of the profile towards the axis of the bore. 22. The method of claim 20, characterized in that after step 3 or 4 a plug (bo2) is sealingly attached to said first end (MCf) of the master cylinder. 23. The method of claim 22, characterized in that said plug (bo2) is fixed along the axis of the bore. 24. The method of claim 22, characterized in that the walls of the first end are crimped on said plug. 25. The method of claim 22, characterized in that said plug is screwed onto the first end of the bore. 26. Method according to one of claims 22 to 24, characterized in that said plug comprises a boss for allowing the centering of the secondary spring of the master cylinder.