Parking brake actuator

Abstract

The invention relates to a parking brake actuator (P), comprising: a piston (1) having a piston rod (1a) and a piston head (1b), the piston (1) being arranged in a housing (3), a spring (2) being arranged between the piston head (1b) and one side of the housing (3); a housing having an opening (3a) into which the piston rod (1a) is movably inserted; a fluid chamber (3b) arranged between the piston head (1b) and the other side of the housing (3), a fluid being able to be introduced into the fluid chamber (3b), the piston (1) comprising at least one first guide element (5a) adapted to guide the piston rod (1a) in the opening (3a), at least one first sealing element (4a) is arranged between the piston rod (1a) and the opening (3a).

Description

Technical Field

[0001] Braking systems for commercial vehicles or utility vehicles typically comprise a parking brake and a service brake. Usually, the parking brake and the service brake are arranged in one brake caliper. Typically, disc brakes are used in commercial vehicles or utility vehicles and are actuated by a combined pneumatic cylinder for the service brake and the parking brake. Such a cylinder therefore has two components, comprising a so-called service brake part and a parking brake part, assembled in series and designed to work in tandem. The service brake part usually actuates the brake under normal driving conditions, while the parking brake part (e.g. comprising a compression spring in the released state) is used to actuate the brake when the power is removed and the vehicle remains stationary. Background Art

[0002] Typically, the parking brake portion actuates the service brake portion using spring force when the air pressure is released.

[0003] For example, the push rod of the parking brake part is connected to the diaphragm. The spring is designed to actuate the service brake part, which actuates the push rod, which in turn actuates the internal mechanism of the brake caliper. When air pressure is released from the system, the spring of the parking brake part pushes the push rod of the service brake part to actuate the brake. Therefore, actuation of the brake without the service brake part is impossible.

[0004] The parking brake portion of current combined cylinders is not directly connected to the internal mechanism of the brake, but rather the parking brake piston needs to be pushed onto the service brake piston in order to transfer the actuation force to the mechanism of the brake.

[0005] In the solution according to the prior art, it is necessary to stack the brake cylinders, and the combined cylinder comprising the parking brake part and the service brake part uses a lot of space.

[0006] However, it is also possible to design a separate parking brake cylinder, wherein the service brake cylinder is not included. For passenger cars, a separation of the brakes has already been implemented, wherein separate brake calipers are provided for the parking brake and for the service brake.

[0007] In the prior art, document DE2614321A1 is known. This document shows a disc brake with an actuation device, which comprises: a force transmission component, which is displaceably arranged in a brake caliper and movably contacts a brake body; a lever, which has two cam surfaces arranged at one of its ends; and at least one body, which is in rolling contact with the other cam surface and the opposite surface on the force transmission component, so that when a drive device acting on the other end of the lever is actuated, the force transmission component acts on the brake disc.

[0008] In the case of using only the parking brake, installation space in the axial direction can be saved and the parking brake can be integrated more easily in a confined space. However, due to the high radial forces introduced into the piston of the parking brake actuator, which is caused by the direct actuation of the push rod connected to the lever of the brake caliper, there is a risk that the seal may wear very quickly and will therefore no longer seal the cylinder.

[0009] If a parking brake cylinder with a diaphragm is used, the diaphragm always causes a deflection, also in cases where only linear movement is required. The diaphragm therefore has to cope with more than one direction of movement (linear movement and angular deflection), which will lead to fatigue at a certain point and will therefore reduce the life of the entire brake system, thus also increasing maintenance costs. Summary of the invention

[0010] The technical problem underlying the present application may therefore be to provide a separate parking brake actuator which is suitable for absorbing high radial forces on the piston in order to ensure a durable sealing capability of the seal of the cylinder.

[0011] The object of the invention is achieved by a parking brake actuator according to claim 1 .

[0012] Further advantageous embodiments of the invention are subject matter of the dependent claims.

[0013] A parking brake actuator according to a first embodiment comprises a piston having a piston rod and a piston head, which is arranged in a housing. A spring is arranged between the piston head and one side of the housing. The housing comprises an opening into which the piston rod is movably inserted. In addition, the housing comprises a fluid chamber, which is arranged between the piston head and the other side of the housing, wherein a fluid, such as a gas, in particular compressed air, can be inserted into the fluid space. The piston comprises at least one first guide element, which is suitable for guiding the piston rod in the opening, and comprises at least one first seal arranged between the piston rod and the opening.

[0014] In this case, the parking brake actuator can directly actuate the internal mechanism of the parking brake and therefore does not require a combined parking brake and service brake cylinder and therefore can save installation space on the axle. This also enables a more compact design. The guidance and sealing of the cylinder are separated in this embodiment and therefore, in addition to the seal, the piston rod is also guided by at least one guide element. This solution enables the piston to always move in a straight line (without angular or radial deflection) and the seal to remain intact throughout its life despite the increased radial forces compared to a conventional parking brake chamber in a combined cylinder.

[0015] Compared to the combined service and parking brake actuators of the prior art, this design of the parking brake cylinder also allows to cope with high deflection angles between the piston and the lever of the internal mechanism of the brake caliper. Furthermore, a new lever design of the internal mechanism of the brake caliper can be realized. The parking brake actuator can be directly connected to the brake caliper, which is used only as a parking brake caliper. The additional guide element can cope with the high radial forces generated by the connection of the piston to the internal mechanism of the brake caliper during actuation and release of the brake.

[0016] The at least one seal may be formed integrally with the respective guide element.

[0017] Preferably, the parking brake actuator additionally comprises a diaphragm, which is suitable for delimiting and sealing the fluid chamber with the spring seal. In this case, the spring can push onto the elastic diaphragm and, if the air pressure is released from the fluid chamber, the spring pushes the piston. The piston can then perform a linear movement and transmit the movement forward to a connecting mechanism, which is connected to the lever of the brake caliper. By separating the sealing and guiding of the piston rod, the guiding and sealing functions are provided by separate components and thus can cope with high guiding forces from potential connecting mechanisms.

[0018] Furthermore, this embodiment makes it possible to use a simplified design of the diaphragm cylinder and still achieve a compact design and have a small installation space.

[0019] If a diaphragm is not used, the parking brake actuator may include a second seal disposed between the piston head and the housing, and a second guide element disposed at the piston head, the second guide element being adapted to guide the movement of the piston head in the housing. Thus, it is ensured that the piston head and the piston rod perform only linear movements.

[0020] The second seal and the second guide element may optionally be formed in one piece.

[0021] Preferably, the first guide element and / or the second guide element is designed as a bushing, preferably a bushing comprising or consisting of polytetrafluoroethylene (PTFE) or a material having similar properties.

[0022] Such a component is very easy to manufacture and very easy to mount on the brake cylinder.

[0023] Preferably, no further actuator is connected to the piston. This means that the parking brake function is only performed by the parking brake actuator, without being connected to the service brake actuator.

[0024] Preferably, the parking brake actuator comprises at least one connecting element (eg arranged at the end of the piston, ie the end facing away from the piston head). The connecting element is suitable for connecting the piston rod with a lever of the parking brake caliper, and the lever is suitable for actuating the parking brake caliper.

[0025] Thus, the linear movement of the piston can be converted into a circular or pivoting movement of the lever.

[0026] Preferably, the conversion of the linear movement with deflection is performed by a lever in the brake caliper, for example in the clamping unit.In order to make the assembly of the connecting element easier, such a connecting element is either attached to the piston of the actuator or to the lever of the brake caliper.

[0027] It is important that the connecting element is designed in a way that allows free movement while keeping the connection in the correct position for assembly of the actuator with the brake caliper.

[0028] Preferably, the connecting element is a push rod, which is preferably arranged in a hole in the piston rod. Thus, a linear movement of the push rod is possible, as is a deflection when the piston is actuated or the brake is released. When the push rod is mounted in the piston, a constant connection is also achieved when not assembled to the brake caliper.

[0029] Preferably, the piston rod comprises a bore with at least one tapered portion, which is arranged on the side opposite to the piston head, and the push rod is arranged in the bore and is adapted to be connected to the lever of the brake caliper via a ball joint. The tapered bore portion of the piston rod allows a greater deflection angle of the push rod during the actuation stroke while increasing the stiffness and strength of the piston rod. Furthermore, self-alignment of the push rod is possible.

[0030] More preferably, the maximum displacement angle of the push rod in the portion of the bore is between 5° and 20°, even more preferably between 10° and 15°.The maximum displacement angle is the displacement of the push rod, which is guided by the ball joint and the bore.

[0031] Preferably, the push rod comprises a ball joint arranged in a hole of the piston rod and the push rod is slidably fixed in the hole by at least one alignment element. This solution allows a constant and stable connection of the push rod and the piston, while still allowing large deflection angles during actuation and release of the brake.

[0032] When the actuator is mounted to the brake caliper, the alignment element also helps to provide a direct connection of the push rod to the lever of the internal mechanism of the brake caliper. If such an alignment element is not provided, the push rod may swing around during assembly and may not contact the lever at the correct position.

[0033] Preferably, the alignment element is a rubber component or an alignment spring adapted for angular alignment of the push rod, thus allowing a flexible connection.

[0034] Alternatively or additionally, the push rod can also be connected directly to the lever instead of the piston, for example via vulcanized rubber, a pin connection or a magnetic connection.

[0035] This solution is suitable for aligning the push rod during assembly with the actuator, but still allowing deflection. These solutions can also be combined with a connection of a ball joint from the piston to the push rod, as this combination of two connection mechanisms allows easy assembly and maintenance.

[0036] Alternatively, the piston rod and the lever of the brake caliper can be directly connected via a bearing (without a push rod), preferably a roller bearing or a needle bearing. This solution allows free movement of the lever while still allowing only linear movement of the piston.

[0037] Alternatively, the piston rod is connected to the lever and the brake caliper by a rack arranged at the piston and a pinion arranged at the lever. In this embodiment, the piston has teeth that interact with the teeth of the lever, and the lever is also a simple connection mechanism.

[0038] The described solution for the parking brake can be combined with all existing emergency release mechanisms as well as incremental pressure compensation solutions (in the spring part). BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Advantageous embodiments of the application are provided below by means of the drawings.

[0040] Figure 1 Different possibilities for arranging a brake on an axle of a utility vehicle are shown.

[0041] Figure 2 The internal design of a parking brake actuator according to a first embodiment of the present invention is shown.

[0042] Figure 3 The arrangement structure of the diaphragm in the parking brake actuator according to the second embodiment of the present invention is shown.

[0043] Figure 4 a shows the arrangement of a push rod which connects the parking brake actuator according to the first embodiment of the invention to other elements of the brake caliper.

[0044] Figure 4 b shows the arrangement of the push rod in the connection between the parking brake actuator and the lever of the parking brake caliper.

[0045] Figure 5 Three possibilities are shown for fixing a push rod in a bore of a piston rod, which push rod connects a parking brake actuator according to a first embodiment of the invention to other elements of a brake caliper.

[0046] Figure 6Three possibilities of connecting the push rod to the lever of the brake caliper are shown.

[0047] Figure 7 A direct connection between the push rod and the lever via a bearing is shown.

[0048] Figure 8 A direct connection between the push rod and the lever via a rack and pinion is shown.

[0049] Fig. 9 The connection between a parking brake actuator and a lever of a brake caliper according to a first embodiment of the invention is shown, wherein a piston rod with a tapered bore is used. DETAILED DESCRIPTION

[0050] exist Figure 1 In a) the arrangement of a combined brake actuator PS at the wheel is shown, such a combined brake actuator PS being used for each wheel. Such a combined brake actuator PS is used in the prior art.

[0051] exist Figure 1 In b), the service brake actuator S and the parking brake actuator P are arranged radially apart and are therefore shorter in the axial direction and occupy less space. Figure 1 The structure of the brake in b) is according to the present application, in which a separate parking brake actuator (P) is used.

[0052] Figure 2A parking brake actuator P according to a first embodiment of the invention is shown. The piston 1 comprises a piston rod 1a and a piston head 1b. The spring 2 is arranged between the piston head 1b and the housing 3, in particular in the upper part of the housing 3. There is a fluid space 3b between the piston head 1b and the lower part of the housing 3, into which air, in particular compressed air, can be introduced and released. In addition, there is a hole 3a in the housing, into which the piston rod 1a is inserted. A first seal 4a and a first guide element 5a are arranged in the opening 3a. The first seal seals the fluid space 3b relative to the environment. The guide element 5a guides the piston rod 1a in the opening 3a. In addition, a second seal 4b is also arranged between the piston head 1b and the housing 3, and a second guide element 5b is also arranged between the piston head 1b and the housing 3. The guide elements 5a and 5b ensure the axial movement of the piston 1 in the housing 3. The spring 2 actuates, i.e. pushes the piston 1 to actuate the brake mechanism. The actuation is completed by releasing the air pressure from the fluid space 3b. The spring force then pushes the piston 1 and the piston 1 slides with the help of the guide elements 4b and 5b and the separate seals 4a and 4b in a purely linear motion. The parking brake actuator P can be mounted directly to a parking brake caliper, which is used only as a parking brake caliper. In this figure, the guide elements 4b and 5b are adapted to cope with high radial forces (e.g. deflections) generated by the connection element to the parking brake caliper C (not shown here).

[0053] Figure 3 A second embodiment of the invention is shown: this second embodiment is very similar to the first embodiment, however, a diaphragm 6 is provided in the lower part of the housing 3. There is also a piston rod 1a and a piston head 1b, wherein the diaphragm is provided below the piston head 1b and is connected to the housing 3. Therefore, a fluid space 3b is defined between the lower part of the housing and the diaphragm 6. In this case, only a first seal 4a and a first guide element 5a in the opening 3a of the housing 3 are required. Optionally, additional guide elements 4b and 5b can be used at the opening 3a of the housing 3 to avoid tilting of the piston 1. Moreover, in Figure 3 An air channel 11 is shown in FIG. 1 for introducing compressed air into the fluid space 3 b and releasing it.

[0054] Figure 4 a) shows a parking brake actuator P according to a first embodiment of the present invention, all components are similar to Figure 1 . However, a hole 1c is provided in the piston 1 (in particular in the piston rod 1a), pointing in a direction away from the piston head 1b (i.e. towards the outside of the housing 3). In the hole 1c a push rod 7a is inserted for connection to a lever L of a brake caliper C (not shown here). It can be seen that the push rod 7a can be deflected during the linear movement of the piston 1 and can also move in different directions to a certain extent.

[0055] Figure 4 b) shows the connection of the parking brake actuator P via the push rod 7 a to the lever L of the brake caliper C (not shown here).

[0056] Figure 5 Three different connections between the bore 1 c of the piston rod 1 a and the push rod 7 a are shown.

[0057] exist Figure 5 In a), on top of the push rod 7a there is a ball joint connection 7b, wherein two pairs of alignment elements 7c are arranged in the hole 1c. They limit the deflection of the push rod 7a.

[0058] exist Figure 5 b) has only one pair of alignment elements 7c, however (with Figure 5 a) has a tapered front section. These alignment elements 7c also allow a certain degree of deflection of the push rod 7a.

[0059] Figure 5 c) shows another possibility of an alignment element 7c, which however fixes the ball joint 7b more tightly and more rigidly in the hole 1c and thus Figure 5 a) allows a smaller deflection of the push rod 7a than 5b).

[0060] Figure 6 a) to 6c) show three possibilities for connecting the push rod 7a directly to the lever L of the parking brake caliper C (not shown here).

[0061] exist Figure 6 In a) there is a connection via vulcanized rubber 7d which connects the lever L and the push rod 7a.

[0062] exist Figure 6 In b) there is a pin connection 7e, where the pin engages the lever L and the push rod 7a.

[0063] exist Figure 6 In c), there is a magnetic connection 7f between the push rod 7a and the lever L, which also allows the movement of the push rod 7a and the lever L.

[0064] exist Figure 7 In the embodiment, the direct connection between the piston 1a and the lever L of the parking brake caliper C (not shown here) is provided by a bearing 8. The bearing 8 is preferably configured as a roller bearing or a needle bearing, both of which allow a rotational movement of the lever while still only allowing a mainly linear movement of the piston 1a.

[0065] Figure 8Another possibility of connecting the piston rod 1a of the parking brake actuator P to the parking brake caliper C (not shown here) is shown. In this case, the rack 9 is arranged on the piston 1a and the pinion 10 is arranged at the lever L (not shown in this figure). In this case as well, the linear movement of the piston 1 can be converted into an angular movement of the lever L.

[0066] exist Fig. 9 , a further connection between the piston rod 1a of the parking brake actuator and the lever L of the brake caliper C (not shown here) is shown. In this case, only the connection between the piston 1a and the lever L is shown, without the rest of the parking brake actuator. Here, the hole 1c of the piston rod 1a is a tapered hole. The tapered hole 1c of the piston rod 1a guides a push rod 7a, which is connected to the lever L via a ball joint 7b. During assembly, the push rod 7a is self-aligned by the angled side of the hole 1c. Here, the displacement angle β is the angle between the center line of the piston 1a and the push rod 7a.

[0067] The present invention is not limited to the above-described embodiments.

[0068] The push rod 7 a may have different shapes. Furthermore, the force transmission to the brake caliper C may be performed by different connection mechanisms 7 .

[0069] List of Figures

[0070] P parking brake actuator

[0071] S Service brake actuator

[0072] PS modular actuator

[0073] W wheel

[0074] C brake caliper

[0075] L Lever

[0076] 1 Piston

[0077] 1a Piston rod

[0078] 1b Piston head

[0079] 1c hole

[0080] 2 Spring

[0081] 3 Shell

[0082] 3a Shell opening

[0083] 3b Fluid Space

[0084] 4a First seal

[0085] 4b Second seal

[0086] 5a First guide element

[0087] 5b Second guide element

[0088] 6 Diaphragm

[0089] 7 Connecting elements

[0090] 7a Putter

[0091] 7b ball joint

[0092] 7c Alignment Components

[0093] 7d vulcanized rubber

[0094] 7e pin connector

[0095] 7f magnetic connector

[0096] 8 Bearings

[0097] 9 rack

[0098] 10 small gears

[0099] 11 Air channels

Claims

1. A parking brake actuator (P), the parking brake actuator comprising: A piston (1) having a piston rod (1a) and a piston head (1b), wherein the piston (1) is arranged in a housing (3), wherein a spring (2) is arranged between the piston head (1b) and one side of the housing (3), The housing has an opening (3a), into which the piston rod (1a) is movably inserted, a fluid chamber (3b) provided between the piston head (1b) and the other side of the housing (3), wherein a fluid can be introduced into the fluid space (3b), wherein the piston (1) comprises at least one first guiding element (5a) adapted to guide the piston rod (1a) in the opening (3a), Furthermore, at least one first sealing member (4a) is provided between the piston rod (1a) and the opening (3a).

2. The parking brake actuator (P) according to claim 1, wherein: The at least one first seal (4a) is formed integrally with the corresponding first guide element (5a).

3. The parking brake actuator (P) according to claim 1 or 2, wherein: The parking brake actuator additionally comprises a diaphragm (6) adapted to delimit the fluid chamber (3b) from the spring (2).

4. The parking brake actuator (P) according to claim 1 or 2, wherein: The parking brake actuator additionally comprises a second seal (4b) arranged between the piston head (1b) and the housing (3), and / or a second guide element (5b) arranged at the piston head (1b), the second guide element being suitable for guiding the movement of the piston head (1b) in the housing (3), wherein the second seal (4b) and the second guide element (5b) are optionally integrally formed.

5. Parking brake actuator (P) according to any one of the preceding claims, wherein: The first guide element (5a) and / or the second guide element (5b) is designed as a bushing, preferably a bushing containing or consisting of polytetrafluoroethylene (PTFE) or a material having similar properties.

6. Parking brake actuator (P) according to any one of the preceding claims, wherein: No further actuator is connected to the piston (1).

7. Parking brake actuator (P) according to any one of the preceding claims, wherein: The parking brake actuator further comprises at least one connecting element (7) suitable for connecting the piston rod (1a) to a lever (L), the lever (L) being suitable for actuating a brake caliper (C).

8. The parking brake actuator (P) according to claim 7, wherein: The connecting element (7) comprises a push rod (7a), which is preferably arranged in a hole (1c) of the piston rod (1a).

9. A parking brake actuator (P) according to any one of claims 7 or 8, wherein: The piston rod (1a) comprises a hole (1c) having at least one tapered portion at a side opposite to the piston head (1b), wherein a push rod (7a) is arranged in the hole (1c) and is adapted to be connected to a lever (L) of a brake caliper (C) via a ball joint (7b).

10. The parking brake actuator (P) according to claim 9, wherein: The maximum displacement angle (β) of the push rod (7a) in the portion of the hole (1c) is between 5° and 20°, preferably between 10° and 15°.

11. The parking brake actuator (P) according to claim 7 or 8, wherein: The push rod (7a) comprises a ball joint (7b) arranged in a hole (1c) of the piston rod (1a), wherein the push rod (7a) is preferably slidably fixed in the hole (1c) by at least one alignment element (7c).

12. The parking brake actuator (P) according to claim 11, wherein The alignment element (7c) is a rubber component or an alignment spring suitable for angular alignment of the push rod (7a).

13. Parking brake actuator (P) according to any one of the preceding claims 7 to 12, wherein: The parking brake actuator further comprises a vulcanized rubber (7d), a pin connection (7e) and / or a magnetic connection (7f), which is suitable for connecting the push rod (7a) to a lever (L) of a brake caliper (C).

14. The parking brake actuator (P) according to any one of claims 1 to 6, wherein: The parking brake actuator further comprises a bearing (8), preferably a roller bearing or a needle bearing, suitable for connecting the piston rod (1a) to a lever (L) of a brake caliper (C).

15. The parking brake actuator (P) according to any one of claims 1 to 6, wherein: The piston rod (1a) is adapted to be connected to the lever (L) via a rack (9) provided at the piston rod (1a) and a pinion (10) provided at the lever (L) of the brake caliper (C).

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