Pneumatic piston and method for producing same

Abstract

A pneumatic piston (100) for an electropneumatic modulator is disclosed. The modulator comprises a piston housing (20) with a chamber (25) for receiving the pneumatic piston (100). The pneumatic piston (100) comprises a sealing element (110), for sealing an intermediate space between the pneumatic piston (100) and the piston housing (20); a piston body (120) with a recess (125) for receiving the sealing element (110); and a securing element (130) which is designed to fix the sealing element (110) in the recess (125) in a form-fitting manner.

Description

[0001] DESCRIPTION

[0002] Pneumatic piston and a method for its production

[0003] The present invention relates to pneumatic pistons, an electropneumatic modulator and a method for manufacturing a pneumatic piston for the electropneumatic modulator.

[0004] Electro-pneumatic modulators are used, for example, in pneumatic braking systems for commercial vehicles to adjust air pressure via targeted electrical control of valves in order to provide a desired braking pressure for a pneumatic brake.

[0005] A conventional electropneumatic modulator and a pneumatic piston are disclosed, for example, in DE 10 2018 121 716 A1. The piston has a hollow cylindrical shape and is axially movable within a chamber of a piston housing. The pressure in the chamber is gradually increased or decreased, for example, via solenoid valves, resulting in axial movement of the piston. A seal between the piston and the housing is provided by a gasket held beneath a cover plate. The cover plate is welded to the piston body or held in place by hot-staking.

[0006] However, this fastening is disadvantageous because large acceleration forces act particularly at a stop of the piston, which can lead to the welded connection breaking and thus the sealing of the piston within the piston housing is no longer reliably guaranteed.

[0007] Therefore, there is a need for alternative pneumatic pistons that ensure a more reliable seal between the piston and the piston housing and can withstand higher loads over time.

[0008] At least some of the above-mentioned problems are solved by a pneumatic piston according to claim 1, an electropneumatic modulator according to claim 7, and a manufacturing method according to claim 8. The dependent claims define further advantageous embodiments of the subject matter of the independent claims.

[0009] The present invention relates to a pneumatic piston for an electropneumatic modulator. The modulator comprises a piston housing with a chamber for receiving the pneumatic piston. The pneumatic piston comprises a sealing element for sealing a gap between the pneumatic piston and the piston housing, a piston body with a recess for receiving the sealing element, and a securing element designed to positively fix the sealing element in the recess. It is understood that the sealing element is designed to seal the gap between the piston body and the housing only after the pneumatic piston has been inserted into the piston housing.

[0010] Optionally, the pneumatic piston includes a locking element designed to lock the securing element to the piston body. The locking element is not mandatory, as the securing element can also be self-locking. The locking mechanism particularly includes an axial direction (linear movement direction of the piston), whereby displacement or bending in the radial direction may be possible or is only prevented after insertion into the housing.

[0011] Optionally, the locking element comprises at least one of the following: a groove, at least one undercut, and at least one hook-shaped projection. The locking element can be an inherent component of the piston body and need not be an independent element. For example, the groove can have a geometry such that the locking element can be inserted into the groove and holds the locking element in the axial direction.

[0012] Optionally, the securing element comprises one of the following:

[0013] - a retaining ring, in particular a snap ring, which can be snapped into the groove, - two half rings which can be locked by the groove and / or by the at least one undercut and / or by the at least one hook-shaped projection,

[0014] - a toothed or untoothed wave washer with a diameter selected such that the wave washer engages in the piston body when inserted,

[0015] - at least one projection which can be inserted into the at least one undercut and / or into the at least one hook-shaped projection (in order to be held there),

[0016] - at least one notch into which a projection on the piston body can radially engage in order to prevent relative rotation between the securing element and the piston body.

[0017] The locking element only needs to be held by the positive connection. According to exemplary embodiments, it is not held by hot-staking or a welded connection. The connection is therefore detachable. However, the locking element can also be held by a click-lock or frog-effect (thicker). In this case, the locking element is self-locking, as it snaps directly into the piston body by bending (e.g., in an annular recess).

[0018] Optionally, the following materials can be used: the sealing element comprises rubber or a plastic, the piston body comprises a plastic or a metal, the securing element comprises a plastic or a metal.

[0019] Optionally, the piston body has the shape of a hollow cylinder or a cylinder. The sealing element and the securing element can be formed on a radially inner surface and / or on a radially outer surface.

[0020] Embodiments also relate to an electropneumatic modulator for a (pneumatic) braking system of a commercial vehicle. The modulator comprises: a previously described pneumatic piston and a piston housing with a chamber for accommodating the pneumatic piston. Embodiments also relate to a method for manufacturing a pneumatic piston, the method comprising:

[0021] - forming a piston body with a recess for receiving the sealing element;

[0022] - Inserting a sealing element into the recess of the piston body to seal a gap between the pneumatic piston and the piston housing; and

[0023] - Locking the sealing element in the recess with a locking element.

[0024] It is understood that the recess and the sealing element can be formed in a ring shape.

[0025] Optionally, the step of forming the piston body is carried out by means of a folding core.

[0026] Embodiments overcome the disadvantages of conventional pneumatic pistons by eliminating the need for welded joints and hot-staking between the piston body and a retaining element. Instead, a positive connection is provided that meets even higher long-term requirements. A large seal can be supported directly in the piston on a flange. This provides a stronger material without the need for a weld. Since no welding process is required,

[0027] Examples have the advantage that it can be manufactured more cost-effectively and quickly while also offering greater reliability.

[0028] The embodiments of the present invention will be better understood from the following detailed description and the accompanying drawings of the various embodiments, which, however, should not be construed to limit the disclosure to the specific embodiments, but are for explanation and understanding only.

[0029] Fig. 1 shows a pneumatic piston according to one embodiment of the present invention. Fig. 2 shows another embodiment of the pneumatic piston.

[0030] Fig. 3 shows a possible design of the securing element as

[0031] Disc in Fig. 2 can be used.

[0032] Fig. 4A, 4B show in a plan view and a cross-sectional view the securing element, as it can be designed as a toothed corrugated washer according to further embodiments.

[0033] Fig. 5 shows a schematic flow diagram for a method for manufacturing the pneumatic piston.

[0034] Fig. 6 illustrates the use of a folding core during the manufacture of the pneumatic piston.

[0035] Fig. 1 shows an embodiment of a pneumatic piston 100 inserted into a chamber 25 of a piston housing 20. The pneumatic piston 100 is formed, for example, as a hollow cylinder, so that an inner through-opening of the pneumatic piston 100 encloses a pin 22 of the piston housing 20 and adjoins an outer (cylindrical) wall 21. A seal between the piston body 120 and the pin 22 is provided by an annular sealing element 110, which is held on the piston body 120 by means of a securing element 130.

[0036] According to exemplary embodiments, the securing element 130 is designed to axially hold the sealing element 110 in a form-fitting manner in a recess 125 (e.g., an annular depression) of the piston body 120. Radial displacement is no longer possible, at least after the pneumatic piston 100 has been inserted into the chamber 25, since the pin 22 or the piston body 120 prevent movement.

[0037] The securing element 130 can be fixed to the piston body 120 by means of a locking element 140, although there are various possibilities for this. In Fig. 1, the locking element 140 is designed, for example, as a groove 142 in the piston body 120, into which the securing element 130 can be inserted. The fixing can take place before the pneumatic piston 100 is inserted into the chamber 25, since releasing the securing element 130 is generally no longer possible thereafter (or only if the pneumatic piston 100 would be at least partially destroyed). This would require radial compression of the securing element 130, which is prevented by the centrally arranged housing pin 22.

[0038] The sealing element 110 can be designed as an O-ring (e.g., made of a rubber material) to seal the connection point between the piston body 120 and the housing 20, wherein the recess 125 for the O-ring 110 can be designed as a chamber. The securing element 130 holds the O-ring 110 in the chamber 125, for example, by means of a so-called Cir Clip (retaining ring or snap ring), which engages in the groove 142 of the piston body 120 and is thus firmly fixed to the piston body 120. The sealing element 110 can therefore also not move in the axial direction (stroke direction of the piston).

[0039] In the assembled state, as can be seen in Fig. 1, the locking element 130 cannot be lost, since compression of the locking ring 130 is prevented by the inner pin 22 of the housing.

[0040] According to further embodiments, it is also possible to fix an additional sealing element 127 between the outer wall 22 and the piston body 120. This optional additional sealing element 127 is accommodated in a further recess in Fig. 1. Here, too, the axial fixation of the additional sealing element 127 can be achieved via an additional securing element (not shown), which in turn establishes a positive connection to the piston body 120. Release would then only be possible through disassembly, for the same reasons as described for the inner retaining ring 130.

[0041] However, the pneumatic piston 100 does not have to be a hollow cylinder, but can also be formed as a conventional cylinder. The housing pin 22 would then be omitted. In this case, a sealing element 127 and securing element would only be present on one outer cylinder wall, but could be formed there in the same way as in the described inner cylinder wall of the hollow cylinder shown. The securing ring 130 can, for example, comprise a plastic material or metal. The piston body 120 can also comprise a plastic material, and the sealing element 110 can comprise a rubber material.

[0042] Fig. 2 shows a further embodiment of the pneumatic piston 100, in which the securing element 130 is a disk that rests on a shoulder portion of the piston body 120 perpendicular to the axial direction. The disk 130 is radially or laterally displaceable and is secured by locking elements 140. The locking elements 140 are designed as undercuts 144, behind which the disk 130 (securing element) engages and is thus held in its axial position perpendicular to the plane of the drawing.

[0043] After inserting the pneumatic piston 100 into the piston housing 20, the disc 130 cannot be pushed out because the inner housing pin 22 (see Fig. 1) prevents radial displacement of the locking element 130. The disc 130 is thus again reliably held in the undercuts 144. The disc 130 cannot rotate (around the axial axis) either, because a projection 145 of the piston body 120 engages a notch in the disc 130 and holds the disc 130 in a rotationally fixed manner.

[0044] Fig. 3 shows a possible embodiment of the securing element 130, as shown as a disk in Fig. 2. The disk 130 is annular and has radially outward-pointing projections 133 and a radial notch 135 into which the locking elements 140 from Fig. 2 can engage. The securing element 130 is thereby held in all spatial directions. The engagement of the locking elements 140 in the notch 135 prevents twisting, and the engagement of the projections 133 (by the undercuts 144) prevents axial displacement. Radial displacement is again prevented by the central pin 22 (see Fig. 1), which engages in the central opening of the disk 130 with only a slight amount of play.

[0045] According to further embodiments, the securing element 130 is formed by two

[0046] Half rings are formed (not shown in the figures), which can engage, for example, in the groove 142 shown in Fig. 1 of the piston body 120. The two half rings are in turn designed so thick in the radial direction that the housing pin 22 can be fitted centrally with only a slight play, and after that the half rings can no longer be removed from the groove 142 (or only after the piston 100 has been removed from the housing).

[0047] Fig. 4A shows a plan view of another embodiment in which the securing element 130 is designed as a toothed corrugated washer that can be inserted into an annular recess 123 of the piston body 120. An outer diameter of the corrugated washer 130 is selected to be slightly larger than an inner diameter of the annular recess 123. This makes it possible for the corrugated washer 130 to be pressed into the annular recess 123 by means of the so-called frog effect or as a click-frog (English: thicker). The outer teeth of the corrugated washer 130 engage in the piston body 120 and, in this metastable state, provide a stable hold for the underlying sealing element 110 through the deflection.

[0048] Fig. 4B shows the embodiment of Fig. 4A in a cross-sectional view along the axial direction through the sealing ring 110 and the corrugated washer 130 located above it. The corrugated washer 130 is secured by pressing downwards along the arrow F. Due to the larger diameter of the corrugated washer 130 compared to the annular recess 123, this bends the corrugated washer 130 and thus causes it to be pressed into the piston body 120. Due to the bending stress, the corrugated washer 130 can no longer detach itself, and the sealing ring 110 is reliably locked. In this case, no separate locking means 140 are provided. Instead, the locking is achieved by the special geometry or dimensions of the securing element 130 and the piston body 120.

[0049] All previous connections between the securing element 130 and the piston body 120 were detachable. However, according to further embodiments, optional permanent connections (e.g., by welding, hot-staking, laser, ultrasound, etc.) can be formed between the securing element 130 and the piston body 120. The securing element 130 can then also be designed as a simple disc.

[0050] Fig. 5 shows a schematic flow diagram for a method for manufacturing the pneumatic piston 100. The method comprises the steps:

[0051] - Forming S110 a piston body 120 with a recess 125 for receiving the sealing element 110;

[0052] - Inserting S120 a sealing element 110 into the recess 125 of the piston body 120 to seal a gap between the pneumatic piston 100 and the piston housing 20; and

[0053] - Locking S130 of the sealing element 110 in the recess 125 with a locking element 130.

[0054] Fig. 6 shows a possible use of a collapsible core 150 (or collapsible core) for producing the piston body 120 with the recess 125. This is particularly possible when the piston body 120 is injection-molded from a plastic material. For this purpose, the collapsible core 150 is unfolded in the mold (only an inner mold 160 is shown in Fig. 6), as indicated by the arrows in Fig. 6. After the exemplary injection molding, the collapsible core 150 can be retracted so that the piston body 120 can be removed together with the recess 125.

[0055] According to another embodiment, it is also possible to use a collapsible core for an O-ring groove. In this case, a retaining ring is no longer required, but there is a risk that the seal could be compromised due to multiple mold separations on the collapsible core.

[0056] It is understood that all of the previously described features of the pneumatic piston 100 can also be implemented through further optional method steps. Furthermore, it is understood that the order in which they are listed does not necessarily represent the order in which the method steps are executed. The steps can also be performed in a different order, or only some of the method steps are performed. Examples of embodiments offer, among other things, the following advantages:

[0057] - The retaining ring or retaining element 130 can provide additional guidance for the piston, which has the advantage of extending the guide length of the inner piston guide. This results in better guidance.

[0058] - The groove 142 in the piston can be manufactured cost-effectively—for example, using a collapsible core. The features of the invention disclosed in the description, claims, and figures may be essential for the implementation of the invention, both individually and in any combination.

[0059] LIST OF REFERENCE SYMBOLS

[0060] 20 piston housings

[0061] 25 chamber in the piston housing 100 pneumatic pistons

[0062] 110, 127 Sealing element

[0063] 120 piston bodies

[0064] 123 annular depression

[0065] 125 Recess(es) 130 Securing element

[0066] 133 radial projection

[0067] 135 incision

[0068] 140 locking element

[0069] 142 Groove 144 Undercut(s)

[0070] 145,146 (hook-shaped) projection

[0071] 150 folding core

[0072] 160 inner form

Claims

PATENT CLAIMS 1. Pneumatic piston (100) for an electropneumatic modulator, wherein the modulator has a piston housing (20; 21, 22) with a chamber (25) for receiving the pneumatic piston (100), the pneumatic piston (100) is characterized by - a sealing element (110) for sealing a gap between the pneumatic piston (100) and the piston housing (20; 21 , 22); - a piston body (120) with a recess (125) for receiving the sealing element (110); and - a locking element (130) designed to positively lock the sealing element (110) in the recess (125).

2. Pneumatic piston according to claim 1, characterized by a locking element (140) which is designed to lock the locking element (130) to the piston body (120).

3. Pneumatic piston according to claim 2, characterized in that the locking element (140) comprises at least one of the following: - a groove (142), - at least one undercut (144), - at least a hook-shaped protrusion.

4. Pneumatic piston according to one of the preceding claims, characterized in that the locking element (130) comprises one of the following: - a retaining ring, in particular a snap ring, which can be snapped into the groove (142) according to claim 3, - two half-rings which can be locked in the groove and / or in the at least one undercut (144) and / or in the at least one hook-shaped projection according to claim 3, - a toothed or untoothed wave washer with a diameter selected such that the wave washer snaps into the piston body (120) when inserted, - at least one projection (133) that can be inserted into the at least one undercut (144) and / or into the at least one hook-shaped projection, - at least a notch (135) into which a projection (145) on the piston body (120) can engage radially in order to prevent a relative rotation between the locking element (130) and the piston body (120).

5. Pneumatic piston (100) according to one of the preceding claims, characterized in that at least one of the following materials is used: - the sealing element (110) comprises rubber or a plastic, - the piston body (120) comprises a plastic or a metal, - the locking element (130) comprises a plastic or a metal.

6. Pneumatic piston (100) according to one of the preceding claims, characterized in that the piston body (120) has the form of a hollow cylinder or a cylinder, and the sealing element (110) and the locking element (130) are located on a radially inner surface.

7. Electropneumatic modulator for a braking system of a commercial vehicle, the modulator comprising the following: - a pneumatic piston (100) according to one of the preceding claims; and - a piston housing (20) with a chamber (25) for receiving the pneumatic piston (100).

8. Method for manufacturing a pneumatic piston (100), characterized by - Forming (S110) a piston body (120) with a recess (125) for receiving the sealing element (110); - Inserting (S120) a sealing element (110) into the recess (125) of the piston body (120) to seal a gap between the pneumatic piston (100) and the piston housing (20); and - Locking (S130) the sealing element (110) in the recess (125) with a locking element (130).

9. Method according to claim 8, characterized in that the step of forming (S110) the piston body (120) is carried out using a folding core.

Images