Pneumatic actuator with magnetic position sensor

Abstract

A pneumatic actuator with a magnetic position sensor is provided. The invention relates to a pneumatic actuator (1) for actuating a functional element (2), comprising: a pneumatic cylinder (4), which comprises a cylinder body (7), the cylinder body (7) defining a pneumatic chamber (8) having a central axis (A); and a pneumatic piston (6), which is used to actuate the functional element (2), and comprises a piston head (12) and a piston rod (14). The piston head (12) is accommodated in the pneumatic chamber (18) in a manner that it can slide along the central axis (A). The pneumatic actuator (1) also includes a magnetic position sensor (64) and a magnet (66), the magnetic position sensor is used to detect the relative position of the pneumatic piston (6), and the magnet (66) is attached to the pneumatic piston (6) so as to cooperate with the position sensor (6). The pneumatic actuator (1) is characterized in that the magnet (66) is point-symmetrical with respect to the central axis (A). The invention also relates to a gearbox (100) and a commercial vehicle (200).

Description

Technical Field

[0001] The present invention relates to a pneumatic actuator for actuating a functional element, in particular a functional element of a commercial vehicle gearbox, the pneumatic actuator comprising: a pneumatic cylinder, which comprises a cylinder body and a cylinder head, the cylinder body defining a pneumatic chamber with a central axis, the cylinder head closing the pneumatic chamber; a pneumatic piston, which is used to actuate the functional element, the pneumatic piston comprising a piston head and a piston rod, the piston rod being used to connect the piston head to the functional element, wherein the piston head is accommodated in the pneumatic chamber in a manner that can slide along the central axis; a magnetic position sensor, which is used to detect the relative position of the pneumatic piston with respect to the pneumatic cylinder; and a magnet, which is attached to the pneumatic piston so as to cooperate with the position sensor. Background Art

[0002] There are various ways of implementing an automatic transmission in vehicles, in particular in commercial vehicles. In addition to automatic gearboxes, automated manual transmission systems are often used. An AMT system comprises a conventional manual gearbox that is automatically driven by one or more pneumatic actuators. The pneumatic actuators are connected to functional elements, for example to a gearshift fork. When the pneumatic actuators are actuated, gear changes can be made without the vehicle driver having to manually actuate the gearshift lever.

[0003] Typically, a pneumatic actuator comprises a pneumatic cylinder and a pneumatic piston. The pneumatic piston is movable relative to the pneumatic cylinder. While moving, the piston actuates a functional element connected to the piston. In order to initiate such movement of the piston, the piston head is accommodated in a pneumatic chamber defined by the cylinder body of the pneumatic cylinder. The pneumatic piston is slidably arranged in the pneumatic chamber and can move back and forth along the central axis of the pneumatic chamber. When the pressure in the pneumatic chamber increases, the pneumatic piston is pushed in the positive stroke direction, and the volume surrounded by the pneumatic piston and the pneumatic chamber increases. The piston rod connected to the piston head extends from the pneumatic chamber and actuates the functional element. When the pressure in the pneumatic piston drops below the ambient pressure level, the piston moves into the pneumatic chamber, performing a negative stroke in the negative stroke direction.

[0004] In order to reduce the wear of the gearbox components, the drive of the functional elements connected to the pneumatic actuator needs to be precise. In order to automatically control the actuator, accurate information about the relative position of the piston relative to the pneumatic cylinder is required. Therefore, the pneumatic actuator includes a position sensor for detecting the relative position of the pneumatic piston to the pneumatic cylinder. The magnetic position sensor is usually of the Hall sensor type. The magnetic position sensor is suitable for detecting a magnet that cooperates with the sensor. If the distance of the magnet relative to the magnetic sensor changes, the magnetic sensor provides a corresponding signal. By attaching a magnet to the pneumatic piston, the relative position of the piston to the pneumatic cylinder can be derived from the sensor signal. The signal can be used to distinguish between multiple piston positions and / or the signal can correspond to the exact distance between the magnet and the magnet position sensor.

[0005] Components of the actuator arranged between the magnet and the sensor, in particular ferromagnetic components and a large distance between the magnet and the sensor can affect the signal strength and / or accuracy of the signal provided by the magnetic position sensor. By arranging the magnet on the outer circumferential surface of the piston head and arranging the magnetic position sensor on a corresponding part of the outer wall of the cylinder body, the distance between the magnet and the magnetic position sensor is kept small for conventional sensors. In order to receive the magnet, the piston head includes a cavity on the circumferential surface. The magnet is accommodated in this cavity and is protected therein. However, the manufacture of the cavity leads to increased manufacturing costs. In addition, the magnet needs to be accurately positioned and assembled to prevent frictional contact between the magnet and the pneumatic cylinder. This leads to increased assembly costs and an increased possibility of functional errors and / or assembly errors. In general, cost and reliability are the most important for components in the automotive and commercial vehicle industries. Summary of the invention

[0006] It is therefore an object of the present invention to provide a cost-effective and reliable pneumatic actuator that is easy to assemble.

[0007] In order to solve this purpose, the present invention proposes in a first aspect that the magnet is point-symmetrical about the central axis. The magnet that is point-symmetrical about the central axis is preferably symmetrical in two dimensions. For multi-angle orientations of the pneumatic piston, the distance of the point-symmetrical magnet relative to the magnetic position sensor is preferably constant. Therefore, when assembling the pneumatic actuator, multiple angular orientations of the pneumatic piston relative to the pneumatic chamber are possible. The risk of incorrect assembly is reduced because more than one orientation of the pneumatic piston relative to the main axis is correct. In addition, traditional and commercially available magnetic position sensors can still be used in the present invention. The point symmetry of the magnet with the central axis depends on the shape of the magnet itself and the relative installation position of the magnet with respect to the central axis. The magnet itself can be point-symmetrical, such as a cube, but it is still not arranged point-symmetrically with respect to the central axis. The axis of symmetry of the point-symmetrical magnet is coaxial with the central axis.

[0008] Preferably, the magnet is attached to the piston head of the pneumatic piston. The magnet attached to the piston head directly provides information about the position of the piston head relative to the pneumatic cylinder. This facilitates the control of the pneumatic actuator. However, it is also possible to attach the magnet to the piston rod. For example, both the magnet and the magnetic position sensor can be arranged outside the pneumatic chamber.

[0009] The cylinder cover is preferably removable from the cylinder body. A removable cylinder cover facilitates assembly of the piston in the pneumatic chamber and sealing of the pneumatic chamber. However, the cylinder cover may also be permanently fixed or integrally formed with the cylinder body. Thus, the pneumatic cylinder may include an access opening which is sealed by the piston head after the piston is received in the pneumatic chamber.

[0010] Preferably, the cylinder head and / or cylinder body are made of aluminum. Aluminum also includes aluminum alloys. Compared with other traditional materials, in particular compared with steel, aluminum is not ferromagnetic and has little effect on the magnetic field provided by the magnet attached to the piston. Therefore, a cylinder head and / or cylinder body made of aluminum allows accurate detection of the relative position of the pneumatic piston.

[0011] Preferably, the magnet is a permanent magnet, particularly preferably a magnet based on neodymium, bismuth manganese and / or aluminum nickel cobalt. For example, the magnetic flux density of the magnet is 1000mT to 2000mT, preferably 1200mT to 1500mT, and further preferably 1300mT to 1400mT. The technical effect of this embodiment is that the material selected for the magnet can achieve the magnetic flux density as described above, thereby accurately determining the position of the piston to which the magnet is attached. According to one embodiment, the magnetic flux density of the magnet is determined using, for example, a gaussmeter relative to the distance to be affected by the magnetic flux density. In another embodiment, the magnetic flux density of the magnet is determined using one of a total flux test (fluxmeter) and a hysteresis test (permeameter). In addition, based on the readings from a test such as a gaussmeter, the material selection, magnet shape and other parameters are calibrated, selected and / or adjusted.

[0012] According to a preferred embodiment, the magnet used in the present invention has a "residual" magnetic flux density in the range of 1300mT and 1400mT, more preferably in the range of 1310mT and 1350mT at room temperature of about 20 degrees Celsius. For example, the term "residual magnetic flux density" is generally defined as the value of the magnetic flux density remaining in a magnetized body (in this case, a "magnet") in the absence of a self-demagnetizing field such that the applied magnetic field strength is zero. The technical effect of this feature is that it allows one of the best possible properties associated with, for example, a pneumatic actuator used in association with the gearbox of the present invention.

[0013] In a first preferred embodiment, the magnet is rotationally symmetric. The angular orientation of the piston has no influence on the orientation of the rotationally symmetric magnet relative to the sensor. Thus, by applying a magnet that is rotationally symmetric relative to the central axis, the possibility of a wrong angle assembly of the pneumatic piston is eliminated. Furthermore, during operation of the pneumatic actuator, the angular orientation of the pneumatic piston relative to the pneumatic cylinder can be changed without affecting the detection of the position sensor. The need to provide dedicated alignment elements on the pneumatic piston is eliminated. The rotationally symmetric magnet can be, for example, cylindrical or disc-shaped.

[0014] Preferably, the piston head comprises a first front face and a second front face, and the magnet is preferably attached to the first front face of the piston head. The front face is preferably substantially perpendicular to the main axis. By attaching the magnet to the front face, the need for machining a receiving portion on the peripheral surface of the pneumatic piston head is eliminated. Machining the peripheral surface is usually cost-intensive and therefore undesirable. Since the recess in the peripheral surface of the piston is not required when the magnet is attached to the front face of the piston head, it is beneficial to the sealing of the pneumatic piston to the pneumatic chamber. In addition, when the piston moves, the magnet is protected from rubbing against the inner surface of the pneumatic cylinder. Therefore, arranging the magnet in the front face increases the reliability and efficiency of the pneumatic actuator. Preferably, the first front face is oriented toward the cylinder head. In cooperation with the pneumatic chamber and the cylinder head, the first front face oriented toward the cylinder head defines the first air volume between the pneumatic piston and the pneumatic cylinder.

[0015] In a preferred embodiment, the piston head includes a mounting recess in the first front face, and the magnet is at least partially accommodated in the mounting recess. The magnet can still protrude beyond the front face, preferably toward the cylinder head. Particularly preferably, the magnet is completely accommodated in the mounting recess. A magnet completely accommodated in the mounting recess can effectively prevent damage. The mounting recess facilitates the attachment of the magnet to the front face. The possibility of incorrect assembly is reduced. In addition, the side walls of the mounting recess can prevent the magnet from moving laterally. The reliability of the pneumatic actuator is thereby increased, and the magnet is prevented from loosening during operation of the pneumatic actuator. Preferably, the internal geometry of the mounting recess corresponds to the external geometry of the magnet. For example, the recess can have a rectangular cross-section perpendicular to the central axis, and the magnet also has a substantially corresponding cross-section. Preferably, the outer side surface of the magnet parallel to the central axis contacts the inner wall of the recess. It is understood that even if the outer side of the magnet contacts the inner wall of the recess, a small gap can be provided to facilitate assembly.

[0016] In another preferred embodiment, the magnet is a ring magnet with a central aperture. Ring magnets are commercially available and can be purchased at a lower cost. In addition, the total weight of the ring magnet is smaller and therefore lighter than a disc magnet. The central magnet axis is defined by the central aperture and is coaxial with the central axis of the pneumatic chamber.

[0017] Preferably, the connecting member connecting the piston head to the piston rod extends through the central aperture of the annular magnet. Therefore, the annular shape of the magnet allows easy assembly of the pneumatic piston. In addition, the connecting member can be approached even after the magnet is attached. In the event of damage to the pneumatic piston and / or the magnet, it is convenient to repair and / or replace parts and improve the overall reliability of the pneumatic actuator. The pneumatic piston is preferably a two-piece construction. The piston rod and the piston head can be manufactured independently, which reduces material consumption and reduces manufacturing costs. Preferably, the piston head is screwed to the piston rod. The connecting member then includes one or more screws. Particularly preferably, the piston head is screwed to the piston rod from the first front. The screw head of the screw is preferably adjacent to the piston head. The connecting member can also be a rivet or include a rivet. The piston rod can also be glued to the piston head. The piston rod can also include a threaded portion. In this case, the connecting member can then be a nut, a locking ring and / or a locking pin. Preferably, the connecting piece is formed integrally with the piston rod or the piston head.

[0018] In a preferred embodiment, the annular magnet is attached to the piston head by means of a connecting member. The connecting member is a multifunctional connecting member that attaches the piston head to the piston rod and attaches the magnet to the piston head. It is convenient to align the annular magnet, the piston head and the piston rod. It is also preferred that the annular magnet is attached to the piston head by a separate element. The connecting member can also include multiple elements, such as screws, rivets and washers.

[0019] According to another preferred embodiment, the magnet is glued to the piston head. By gluing the magnet to the piston head, a durable and easy fixation of the magnet can be achieved. In general, gluing is a fast and cost-effective assembly method. The glue can compensate for deformations of the piston head and is reliable in the long term. Gluing is particularly preferred when the magnet is attached to the front face of the piston head. Since the risk of friction between the magnet and the inner surface of the pneumatic body is eliminated by attaching the magnet to the front face, the amount of glue for attaching the magnet to the piston head can be provided with lower precision, which further facilitates assembly. Differences in the distance along the center axis between the magnet and the magnetic position sensor due to inaccurate dispensing of the glue can be easily compensated and therefore have no influence on the overall function of the sensor.

[0020] Preferably, the main sensor axis of the position sensor is parallel to, particularly preferably coaxial with, the center axis of the pneumatic chamber. The main sensor axis is defined by the measuring direction of the magnetic position sensor. The parallel and / or coaxial arrangement of the main sensor axis and the center axis facilitates processing of the signal provided by the magnetic position sensor corresponding to the position of the magnetic sensor. Preferably, the center axis extends through the sensor. Thereby the possibility of misalignment is further reduced.

[0021] In a preferred embodiment, the position sensor is arranged on the outside of the cylinder head opposite the pneumatic chamber. By arranging the magnetic position sensor on the outside of the cylinder head, the risk of damage to the magnetic position sensor is reduced. In addition, the position sensor arranged on the outside is easily accessible. Assembly is facilitated because the wires or cables connecting the position sensor to the control unit do not need to enter the pneumatic chamber. The pneumatic cylinder head is preferably removable from the pneumatic chamber. The magnetic position sensor can then be attached to the piston head before the piston head is installed in the pneumatic chamber, which further facilitates correct alignment and assembly.

[0022] Preferably, the exterior of the cylinder head comprises a sensor recess, and the position sensor is at least partially accommodated in the sensor recess. The sensor recess thereby facilitates the correct positioning of the magnetic position sensor. When the position sensor is accommodated in the recess, it can be protected from damage by the surrounding cylinder head. Preferably, the recess is a rotationally symmetrical recess. Thus, the cylinder head can be manufactured by turning, which is a cost-effective and precise production method for rotationally symmetrical components. Preferably, the internal geometry of the sensor recess corresponds to the external geometry of the position sensor. The cylinder head may further comprise a sensor cover for covering the position sensor received in the sensor recess. The sensor cover further protects the position sensor from damage, in particular from moving elements, corrosive media and / or heat.

[0023] According to a preferred embodiment, the peripheral surface of the piston head is continuous. The continuous peripheral surface does not include a cavity. However, it should be understood that the continuous peripheral surface can still include a variable radius perpendicular to the central axis and / or a step. For example, the first peripheral surface for attaching the first sealing element can have a smaller or larger radius than the second peripheral surface for receiving the second sealing element. The continuous peripheral surface can be manufactured at low cost and with high precision.

[0024] In another preferred embodiment, the piston rod is rotationally symmetrical along at least a portion thereof. Preferably, the first end of the piston rod opposite the piston head is symmetrical. A symmetrical piston rod eliminates the risk of misalignment during assembly. Since the magnet is symmetrical, no alignment elements, such as hooks or noses, are required on the piston rod of the piston head to ensure correct alignment of the magnet relative to the magnetic position sensor. Since such alignment elements require additional manufacturing steps, point-symmetrical magnets allow for a cost-effective piston rod design. In particular, the piston assembly comprising the pneumatic piston and the magnet is rotationally symmetrical.

[0025] According to a second aspect of the invention, the above-mentioned problem is solved by a gearbox, in particular a gearbox for commercial vehicles, comprising a pneumatic actuator according to any embodiment described in the first aspect of the invention. Preferably, the cylinder body is formed integrally with the housing of the gearbox. However, a pneumatic actuator attached to the housing of the gearbox by connecting elements such as screws or rivets is also preferred. In addition, the pneumatic cylinder can also be partially or completely welded to the housing of the gearbox. Particularly preferably, the pneumatic actuator is received in the housing of the gearbox. The pneumatic piston, other elements of the actuator or functional elements arranged inside the gearbox do not pass through the gearbox housing. Thereby, the sealing of the gearbox housing is promoted and the reliability is improved.

[0026] In a third aspect of the invention, the above problem is solved by a commercial vehicle comprising a gearbox according to the second aspect of the invention. It should be understood that the pneumatic actuator according to the first aspect of the invention, the gearbox according to the second aspect of the invention and the vehicle according to the third aspect of the invention preferably have similar or identical aspects, in particular as they are described in the dependent claims. Therefore, reference is made to the above description of the pneumatic actuator according to the first aspect of the invention.

[0027] In order to more completely understand the present invention, the present invention will now be described in detail with reference to the accompanying drawings. The detailed description will illustrate and describe the contents of the preferred embodiments of the present invention. It should be understood that various modifications and changes can be easily made in form or detail without departing from the spirit of the present invention. Therefore, the present invention is not limited to the exact form and details shown and described herein, nor is it limited to the entirety of the present invention disclosed herein and claimed below. In addition, the features described in the specification, drawings and claims of the present invention may be indispensable for the present invention considered alone or in combination. In particular, any figure mark in the claims should not be interpreted as limiting the scope of the present invention. The wording "comprising" does not exclude other elements or steps. The words "one" or "an" do not exclude plural numbers. The wording "multiple" items also include the number 1, i.e., a single item, and other numbers, such as 2, 3, 4, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the attached picture:

[0029] Figure 1 shows a cross-sectional view of a first embodiment of a pneumatic actuator;

[0030] Figure 2 A cross-sectional view showing a pneumatic actuator according to a second embodiment; and

[0031] Figure 3 A commercial vehicle is shown having a gearbox including a pneumatic actuator. DETAILED DESCRIPTION

[0032] A pneumatic actuator 1, in particular a pneumatic actuator 1 for actuating a functional element 2 of a gearbox 100, comprises a pneumatic cylinder 4 and a pneumatic piston 6. The piston body 7 of the pneumatic cylinder 4 defines a pneumatic chamber 8, which has a central axis A. On a first side 9, the pneumatic chamber 8 is closed by a cylinder cover 10 of the pneumatic cylinder 4. The pneumatic cylinder 4 is formed integrally with a housing 102 of the gearbox 100. The pneumatic actuator 1 is received in an interior 104 in the gearbox 100 (see also Figure 3 ).

[0033] The piston head 12 of the pneumatic piston 6 is accommodated in the pneumatic chamber 8 of the pneumatic cylinder 4. The piston head 12 is connected to a piston rod 14 of the pneumatic piston 6, which extends through a cylinder bore 15 of the pneumatic cylinder 4 on a second side 16 opposite to the first side 9. The cylinder bore 15 is formed in a bottom 18 of the cylinder body 7. The maximum outer diameter D1 of the piston head 12 is greater than the corresponding inner diameter D2 of the piston orifice 15. During assembly of the pneumatic actuator 1, the pneumatic piston 6 is inserted from the first side 9 through the head opening 20. After the pneumatic piston 6 has been inserted, the cylinder cover 10 closes the cover opening 20 of the pneumatic chamber 8. However, the inner diameter D2 can also correspond to the maximum outer diameter D1, so that the pneumatic piston 6 can be inserted into the pneumatic chamber 8 from the second side 16 through the piston orifice 15.

[0034] The piston head 12, the cylinder head 10 and the inner wall 22 of the cylinder 7 enclose a first volume V1. In order to move the pneumatic piston 6, a first pressure p1 is applied to the first volume V1. Opposite to the first volume V1, a second volume V2 is defined in the pneumatic chamber 8. The second volume V2 is fluidically connected to the interior 104 of the gearbox 100 via the channel 17. If the first pressure p1 exceeds the ambient pressure p1 of the interior 104, the second volume V2 is fluidly connected to the interior 104 of the gearbox 100. a , the ambient pressure p a Also applied to the second volume V2, the first volume V1 increases and the pneumatic piston 6 performs a positive stroke in the positive stroke direction R1. The bearing 62 guides the pneumatic piston 6 so that the positive stroke direction R1 is parallel to the center axis A. In order to perform a negative stroke of the pneumatic piston 6 in the negative stroke direction R2 opposite to the positive stroke direction R1, a pressure below the ambient pressure p a The second pressure p2 is applied to the first volume V1. However, the movement of the pneumatic piston 6 in the positive stroke direction R1 and / or the negative stroke direction R2 may also be achieved and / or assisted by a biasing member, such as a spring.

[0035] By applying the varying pressures p1, p2 to the first volume V1, the pneumatic piston 6 can be moved back and forth relative to the pneumatic cylinder 4. At the first end 24 opposite to the piston head 12, the piston rod 14 engages the functional element 2. The piston rod 14 transmits the movement of the piston head 12 to the functional element 2. When the pneumatic piston 6 performs a positive stroke in the positive stroke direction R1, the functional element 2 engaging the piston rod 14 is actuated and also moves in the positive stroke direction R1. During the negative stroke of the piston 6 in the negative stroke direction R2, the functional element 2 also moves in the negative stroke direction R2.

[0036] In order to engage the functional element 2, the piston rod 14 comprises a recess 26. In this embodiment and preferably the recess 26 is a substantially U-shaped recess 26. Additionally or alternatively, the piston rod 14 may also comprise a radial protrusion (not shown) for engaging the functional element 2. The recess 26 extends along the entire circumference of the piston rod 14. However, the recess 26 may also extend only partially around the circumference of the piston rod 14.

[0037] The pneumatic piston 6 is a two-piece structure. The piston head 12 and the piston rod 14 are manufactured independently and attached to each other when the pneumatic piston 6 is assembled. A connecting member 27 attaches the piston head 12 to the piston rod 14. Here, the connecting member 27 is a screw 28 having a shaft 30 and a screw head 32. The shaft 30 includes an external thread 34, which is received in a corresponding internal thread 36 of a hole 38 in the piston rod 14. The shaft 30 extends through the piston head 12, and the screw head 32 is adjacent to the first front face 40 of the piston head 12. In this embodiment, the first front face 40 points to the cylinder head 10. Opposite to the first front face 40, the piston head 12 includes a second front face 42. Both the first front face 40 and the second front face 42 are perpendicular to the central axis A.

[0038] The piston rod 14 is directly adjacent to the second front face 42 of the piston head 12. However, the piston head 12 may also preferably include a rod recess (not shown) for partially receiving the piston rod 14. The piston head 12 can be attached to the piston rod 14, and then the assembled pneumatic piston 6 can be inserted into the pneumatic cylinder 4 from the first side 9. Since the piston rod 14 is connected to the piston head 12 in a detachable manner, it is also possible to first insert the piston rod 14 from the second side 16 and then attach the piston rod 14 to the piston head 12. Depending on the layout of the gearbox 100, this can facilitate assembly. Therefore, the two-part structure of the pneumatic piston 6 allows a variety of arrangements. The same design of the pneumatic actuator 1 can be used for different gearbox designs.

[0039] After the pneumatic piston 6 has been inserted, the cylinder head 10 closes the pneumatic chamber 8. The cylinder head 10 comprises a second outer thread 44 corresponding to the second inner thread 46 of the cylinder block 7. In order to seal the first volume V1, a first sealing element 48 is arranged in a sealing groove 50 of the cylinder head 10. Figure 1 and Figure 2In the exemplary embodiment of FIG. 4 , the cylinder head 10 is rotationally symmetrical and the sealing element 48 is formed as an O-ring.

[0040] In order to seal the volume V1, the piston head 12 includes two lip seals 52, 54. The lip seals 52, 54 are oriented in opposite directions. The leg 52.1 of the first lip seal 52 extends in the positive stroke direction R1, while the leg 54.1 of the second lip seal 54 extends in the negative stroke direction R2. The legs 52.1, 54.1 abut the inner wall 22 of the cylinder 7 and ensure the sealing of the first volume V1. In order to receive the first lip seal 52 and the second lip seal 54, the cylinder head 14 has a T-shaped cross section. The peripheral surface 57 of the piston head 12 is continuous and does not include a cavity. The radial protrusion 56 that defines the maximum outer diameter D1 of the piston head 12 protrudes beyond the sealing surfaces 58, 60 of the piston head 12. The lip seal abuts the sealing surfaces 58, 60 and the radial protrusion 56. The sealing surfaces 58 , 60 prevent the lip seals 52 , 54 from deforming in the radial direction R3 perpendicular to the central axis A, while the radial protrusion 56 prevents relative movement of the lip seals 52 , 54 in the positive stroke direction R1 and / or the negative stroke direction R2 and / or facilitates installation of the lip seals 52 , 54 .

[0041] A small gap (not shown) is formed between the piston head 12 and the inner face 22. In order to guide the pneumatic piston 6, the piston rod 14 extends through a guide bearing 62 arranged at the bottom 18 of the cylinder 7. The bearing 62 is a sliding bearing, but can also be formed as a rolling bearing. Alternatively or additionally, the piston head 12 can also contact the inner face 22 to guide the pneumatic piston 6.

[0042] In order to detect the relative position of the pneumatic piston 6 and the pneumatic cylinder 4, in particular the position of the pneumatic piston 6 along the central axis A, the pneumatic actuator 1 comprises a magnetic position sensor 64 and a magnet 66 cooperating with the magnetic position sensor 64. The position sensor 64 is adapted to detect the magnet 66. The position sensor is arranged on the outer portion 65 of the cylinder head 10. Preferably, the position sensor 64 provides a sensor signal corresponding to the distance L between the position sensor 64 and the magnet 66. The sensor axis AS is parallel to the central axis A of the pneumatic chamber 8, along which the sensor can detect the distance L. Therefore, the signal is proportional to the distance L and can be used to determine the position of the pneumatic piston 6 relative to the pneumatic cylinder 4 without complex calculations.

[0043] The magnet 66 is attached to the first front face 40 of the piston head 12 and is rotationally symmetrical with respect to the central axis A. By attaching the magnet 66 to the first front face 40 facing the cylinder head 10, the distance L between the sensor 64 and the magnet 66 is minimized. The magnet 66 is an annular magnet 68 having a central orifice 70. The central orifice 70 defines a central magnet axis AM coaxial with the central axis A. The annular magnet 68 is rotationally symmetrical about the central axis A. Therefore, the relative position of the annular magnet 68 relative to the position sensor 64 arranged on the cylinder head 10 is the same for each angular orientation of the pneumatic piston 6. For example, the pneumatic piston 6 can be rotated 90° around the central axis A without changing the relative position of the annular magnet 66 and the position sensor 64. Therefore, when the pneumatic piston 6 rotates around the central axis A, the signal representing the distance L does not change. Therefore, during assembly, the angular orientation of the pneumatic piston 6 relative to the pneumatic cylinder has no effect on the function of the position sensor 64. Furthermore, during operation of the pneumatic actuator 1, the piston rod 14 can be rotationally symmetrical and no alignment elements are required to prevent rotation of the piston rod 14. The connecting member 27 extends through the central aperture 70 of the annular magnet 68. Thus, the annular magnet 68 can be fixed to the piston head 12 before attaching the piston head 12 to the piston rod 14. Point symmetry of the magnet 66 about the central axis can be easily achieved and facilitates correct alignment.

[0044] exist Figure 1 In the embodiment of the present invention, the annular magnet 68 is bonded to the first front face 40. In particular, the annular magnet 68 is received in a mounting recess 72 of the piston head 12. The mounting recess 72 protects the magnet 66 from damage. In this embodiment, the mounting recess diameter D3 defined by the radial inner recess surface 74 is larger than the outer ring diameter D4 of the annular magnet 68. Therefore, sufficient space is provided for receiving the magnet 66 in the mounting recess 72. However, the internal geometry of the mounting recess 72, in this embodiment, the mounting recess diameter D3 can substantially correspond to the external geometry of the magnet 66, in this embodiment, corresponding to the outer ring diameter D4. This can further facilitate the correct alignment of the magnet 66 relative to the piston head 12. The outer ring diameter D4 can be exactly the same as the mounting recess diameter D3.

[0045] The cylinder head 10 includes a sensor recess 76, and the position sensor 64 is received in the sensor recess 76. By arranging the sensor 64 in the sensor recess 76, the distance L between the magnet 66 and the magnetic position sensor 64 is minimized. In addition, the position sensor 64 is completely accommodated in the sensor recess 76, which is a stepped recess in this embodiment. In order to further protect the sensor 64, the sensor recess 76 can be closed from the first side 9 by a cover, a cap or a cover (not shown). The sensor axis AS is spaced apart from the center axis A. However, the center axis A and the sensor axis AS can also be congruent, and / or the sensor 64 can be arranged rotationally symmetrically about the center axis A. In this embodiment and preferably, the cylinder head 10 is substantially wedge-shaped. The wedge points to the positive stroke direction R1. Thereby reducing the distance between the magnet 66 and the magnetic position sensor 64. For a wedge-shaped cylinder head 10 at a constant distance L, the first volume V1 defined between the piston head 12, the inner wall 22 and the cylinder head 10 is larger than in the case of a generally cylindrical cylinder head 10. The larger first volume V1 allows for more precise actuation of the pneumatic piston 6 and the functional element 2, respectively. In addition, the wedge shape is structurally stable and prevents deformation of the cylinder head 10 when a pressure p1 is applied to the first volume V1. Therefore, the material thickness T1 of the sensor recess grinding portion 78 of the sensor recess 76 can be reduced without sacrificing the stability of the cylinder head 10. The influence of the cylinder head 10 on the position detection of the pneumatic piston 6 is reduced, and the position sensor 64 can provide a stronger and / or more accurate signal.

[0046] Figure 2 A second embodiment of the pneumatic actuator 1 is shown. The same reference numerals are applied to corresponding components and reference is made to the description of the first embodiment of the pneumatic actuator 1 .

[0047] In the second embodiment, the magnet 66 is attached to the piston head 12 of the pneumatic piston 6 by means of a connection 27. For the first embodiment, the connection 27 includes a screw 28. In addition, the connection 27 includes a washer 80 arranged between the screw head 32 and the annular magnet 68. However, the screw head 32 can also directly abut the annular magnet 68. The washer 80 is cup-shaped and has an inclined surface 82 adjacent to the annular magnet 68. By providing the inclined surface 82, the point-symmetrical arrangement of the magnet 68 about the central axis A is facilitated. When the ring connection member 27 is tightened, a fixing force F1 is provided along the central axis A in the positive stroke direction R1. Since the inclined surface 82 of the adjacent magnet 64 is inclined relative to the central axis A, the second force F2 transmitted to the annular magnet 68 via the washer 80 is also inclined. The second force F2 has an axial component along the positive stroke direction R1 and a radial component along the radial direction R3. If the radial magnet 68 is misaligned relative to the central axis A, the radial component of the second force F2 moves the annular magnet 68 until the central aperture 70 is centered about the central axis A and the magnet axis AM is coaxial with the central axis A. A preferred washer 80 having an inclined surface 82 is provided to allow the magnet 66 to automatically align relative to the central axis A when the connecting member 27 is tightened.

[0048] Figure 3 A commercial vehicle 200 is shown, which has a motor 202, a gearbox 100, a clutch 204 and a drive shaft 206, which connects the motor 202 to the clutch 204 and the gearbox 100. The pneumatic actuator 1 is arranged in the interior 104 of the gearbox 100. The piston shaft 14 extends from the pneumatic cylinder 4 and is connected to the functional element 2. In the present embodiment, the functional element 2 is a shift fork 106 of the gearbox 100. Using the shift fork 106, the first gear 108 of the gearbox 100 can be actuated and moved in the positive stroke direction R1 or the negative stroke direction R2. Figure 3 In the embodiment, the pneumatic piston 6 is in the outermost position and the larger first gear 108.1 engages the smaller second gear 110.1 of the driven shaft 112. By applying a second pressure p2 to the first volume V1, the second pressure p2 is less than the ambient pressure p of the interior 104 of the gearbox 100. a , the pneumatic piston 6 can move in the negative stroke direction R2. The shift fork 106 also moves in the negative stroke direction R2. The shift fork 106 slides the first gear 108 along the shaft 112, so that the larger first gear 108.1 is disengaged from the smaller second gear 110.1, and the smaller first gear 108.2 is in contact with the larger second gear 110.2. Therefore, the gear of the gearbox 100 is changed when the pneumatic actuator 1 is actuated.

[0049] The magnetic position sensor 64 detects the position of the magnet 66 and provides a corresponding position signal S to a controller 116 of the vehicle 100 via a cable 114 . Since the position of the pneumatic piston 6 relative to the pneumatic cylinder 4 corresponds to the position of the functional element 2 , the position signal S can be used to automatically control the gearbox 100 .

[0050] The pneumatic actuator 1 is arranged in the interior 104 of the gearbox 100, and neither the piston shaft 14 nor the fork 106 passes through the housing 102 of the gearbox 100. The sealing of the gearbox 100 is thereby promoted, and leakage of the oil 118 contained in the gearbox 100 is effectively prevented. The cylinder block 7 is formed integrally with the housing 102 of the gearbox 100. For example, the entire gearbox housing 102 including the cylinder block 7 may be integrally cast.

[0051] Reference Symbols List:

[0052] 1Pneumatic Actuator

[0053] 2 Functional elements

[0054] 4 Pneumatic Cylinders

[0055] 6 Pneumatic piston

[0056] 7 Piston body

[0057] 8 Pneumatic chamber

[0058] 9 First side

[0059] 10 Cylinder head

[0060] 12 piston head

[0061] 14 Piston rod

[0062] 15 cylinder port

[0063] 16 Second side

[0064] 17 channels

[0065] 18 Bottom

[0066] 20 openings

[0067] 22 Inner wall

[0068] 24 First end of piston rod

[0069] 26 grooves

[0070] 27 Connectors

[0071] 28 screws

[0072] 30 screw shaft

[0073] 32 screw head

[0074] 34 external thread

[0075] 36 internal thread

[0076] 38 holes

[0077] 40 First Front

[0078] 42 Second Front

[0079] 44 second external thread

[0080] 46 second internal thread

[0081] 48 first sealing element

[0082] 50 Sealing groove

[0083] 52 first lip seal

[0084] 52.1 Leg first lip seal

[0085] 54 Second lip seal

[0086] 54.1 Leg second lip seal

[0087] 56 Radial protrusion

[0088] 57 Outer circumferential surface of piston head

[0089] 58 Sealing surface

[0090] 60 Sealing surface

[0091] 62 guide bearing

[0092] 64 Magnetic Position Sensor

[0093] 65 cylinder head exterior

[0094] 66 Magnets

[0095] 68 Ring Magnet

[0096] 70 center hole

[0097] 72 installation recess

[0098] 74 inner concave surface

[0099] 76 sensor recess

[0100] 78 Sensor concave grounding

[0101] 80 washers

[0102] 82 bevel

[0103] 100 Gear Box

[0104] 102 Shell

[0105] 104 The interior of the gearbox

[0106] 106 shift fork

[0107] 108 first gear

[0108] 108.1 Larger first gear

[0109] 108.2 Smaller first gear

[0110] 110 second gear

[0111] 110.1 Smaller second gear

[0112] 110.2 Larger Second Gear

[0113] 112 driven shaft

[0114] 114 Cable

[0115] 116 Controller

[0116] 118 oil

[0117] 200 vehicles

[0118] 202 Motor

[0119] 204 Clutch

[0120] 206 drive shaft

[0121] ACentral axis

[0122] AM center magnet axis

[0123] AS main sensor axis

[0124] D1 Maximum outer diameter of piston head

[0125] D2 Piston hole inner diameter

[0126] D3 recess diameter

[0127] D4 outer ring diameter

[0128] F1 first force

[0129] F2 Second Force

[0130] L distance

[0131] p1 first pressure

[0132] p2 second pressure

[0133] p a Environmental pressure

[0134] R1 positive travel direction

[0135] R2 negative travel direction

[0136] R3 radial direction

[0137] S signal

[0138] T1 Cylinder head material thickness

[0139] V1 first volume

[0140] V2 Second volume

Claims

1. A pneumatic actuator (1) for actuating a functional element (2), the pneumatic actuator (1) comprising: A pneumatic cylinder (4), wherein the pneumatic cylinder (4) comprises: a cylinder (7) defining a pneumatic chamber (8) having a central axis (A), and a cylinder head (10), the cylinder head (10) enclosing the pneumatic chamber (8); A pneumatic piston (6), the pneumatic piston (6) is used to actuate the functional element (2), and the pneumatic piston (6) comprises: a piston head (12), and a piston rod (14) for connecting the piston head (12) to the functional element (2), wherein the piston head (12) is accommodated in the pneumatic chamber (8) in a manner capable of sliding along the central axis (A); a magnetic position sensor (64), the magnetic position sensor (64) being used to detect the relative position of the pneumatic piston (6) and the pneumatic cylinder (4); and a magnet (66) attached to the pneumatic piston (6) so as to cooperate with the magnetic position sensor (64), The invention is characterized in that the magnet (66) is point-symmetrical with respect to the central axis (A). wherein the cylinder cover is wedge-shaped, and the wedge points toward the pneumatic chamber (8), wherein the position sensor (64) is arranged on the outer portion (65) of the cylinder head (10) opposite to the pneumatic chamber (8), The outer portion (65) of the cylinder head (10) comprises a sensor recess (76), and the position sensor (64) is at least partially received in the sensor recess (76).

2. The pneumatic actuator (1) according to claim 1, wherein: The magnet (66) is rotationally symmetric.

3. The pneumatic actuator (1) according to claim 1 or 2, wherein: The piston head (12) includes a first front face (40) and a second front face (42), and wherein the magnet (66) is attached to the first front face (40) of the piston head (12).

4. The pneumatic actuator (1) according to claim 3, wherein: The piston head (12) includes a mounting recess (72) in the first front face (40), and wherein the magnet (66) is at least partially received in the mounting recess (72).

5. The pneumatic actuator (1) according to claim 1 or 2, wherein: The magnet (66) is an annular magnet (68) having a central aperture (70), wherein a central magnet axis (AM) defined by the central aperture (70) is coaxial with a central axis (A) of the pneumatic chamber (8).

6. The pneumatic actuator (1) according to claim 5, wherein: A connecting member (27) connecting the piston head (12) to the piston rod (14) extends through a central aperture (70) of the annular magnet (68), wherein the annular magnet (68) is attached to the piston head (12) by means of the connecting member (27).

7. The pneumatic actuator (1) according to claim 1 or 2, wherein: The magnet (66) is glued to the piston head (12).

8. The pneumatic actuator (1) according to claim 1 or 2, wherein: The main sensor axis (AS) of the position sensor (64) is parallel to the center axis (A) of the pneumatic chamber (8).

9. The pneumatic actuator (1) according to claim 1, wherein: The functional element (2) is a functional element (2) of a gearbox (100) of a commercial vehicle (200).

10. The pneumatic actuator (1) according to claim 1 or 2, wherein: At room temperature of about 20°C, the magnets have a "residual" flux density in the range of 1300 mT and 1400 mT.

11. The pneumatic actuator (1) according to claim 10, wherein: At room temperature of about 20°C, the magnets have a "residual" flux density in the range of 1310 mT and 1350 mT.

12. The pneumatic actuator (1) according to claim 1 or 2, wherein: The outer peripheral surface (57) of the piston head (12) is continuous.

13. The pneumatic actuator (1) according to claim 1 or 2, wherein: The piston rod (14) is rotationally symmetrical.

14. The pneumatic actuator (1) according to claim 1 or 2, wherein: The magnet is made of neodymium magnet, bismuth manganese magnet and / or alnico magnet.

15. The pneumatic actuator (1) according to claim 14, wherein: The magnet has a magnetic flux density in the range of 1000 mT to 2000 mT.

16. The pneumatic actuator (1) according to claim 14, wherein: The magnet has a magnetic flux density in the range of 1200 mT to 1500 mT.

17. The pneumatic actuator (1) according to claim 14, wherein: The magnet has a magnetic flux density in the range of 1300 mT to 1400 mT.

18. A gearbox (100) comprising a pneumatic actuator (1) according to any one of the preceding claims.

19. The gearbox (100) according to claim 18, wherein the gearbox (100) is a gearbox (100) for a commercial vehicle (200).

20. A commercial vehicle (200) comprising a gearbox (100) according to claim 18 or 19.

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