DE20116818U1 - hydraulic cylinders - Google Patents

Description

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Hydraulic cylinder

Description

The invention relates to a hydraulic cylinder according to the preamble of claim 1. In particular, the invention relates to a master or slave cylinder for a hydraulic clutch actuation for motor vehicles, as are used en masse in the automotive industry.

A conventional hydraulic clutch actuator for motor vehicles has a master cylinder connected to a compensating tank filled with hydraulic fluid, which can be actuated, for example, via a clutch pedal or an electric motor drive. The master cylinder is hydraulically connected to a slave cylinder via a pressure line, so that the pressure generated by depressing the clutch pedal or electromotive displacement of the master cylinder piston in the master cylinder can be transferred to the slave cylinder via the fluid column in the pressure line. As a result, the clutch release bearing is subjected to an actuating force via the slave cylinder piston in order to separate the clutch pressure plate from the clutch drive plate and thus the engine from the transmission of the motor vehicle via a release mechanism. Hydraulic clutch actuators are also known in which the clutch release mechanism can be actuated by an operatively connected actuating or slave cylinder, which in turn is controlled via a hydraulic servo circuit.

In such hydraulic clutch actuations for motor vehicles, it has already been proposed in the prior art to sense the position of the piston of the master or slave cylinder by means of suitable mechanical, electrical or magnetic devices (e.g. US 4,705,151, DE 41 20 643 Al, DE

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199 15 832 Al) in order to indirectly determine the position of the clutch pressure plate. Such a sensing system enables a statement to be made about the state of wear of the clutch. On the other hand, the engagement or disengagement state of the clutch can be determined so that, for example, in the case of automated friction clutches, the clutch actuation can be controlled automatically to the desired extent. The results of the sensing system can also be used for safety precautions in the operation of the motor vehicle.

In this context, the generic document DE 199 832 A1 discloses a master cylinder which has a piston arranged in a housing so that it can be moved longitudinally. An annular groove is formed on the piston, which serves to accommodate a ring magnet.

A receiving part is located on the housing of the master cylinder, in which two Hall switches, associated evaluation electronics and a connecting contact part are arranged. The position of the ring magnet and thus the position of the piston is detected through the wall of the cylinder housing by means of the Hall switches, whereupon the corresponding switching signal is processed by the evaluation electronics and then sent out via the connecting contact part for further processing. Finally, DE 199 15 832 A1 generally mentions that the receiving part can be subsequently placed on the housing of the master cylinder and locked into place. However, a specific design of such a connection cannot be derived from this state of the art.

Based on the prior art according to DE 199 15 832 A1, the invention is based on the object of creating a hydraulic cylinder with a device for detecting the piston position, in which a position sensor of the detection device, which cooperates with a signal element on the piston, can be fixed to the cylinder housing in a simple and defined manner.

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This object is achieved by the features specified in claim 1. Advantageous or expedient developments of the invention are the subject of claims 2 to 14.

According to the invention, in a hydraulic cylinder, in particular a master or slave cylinder for a hydraulic clutch actuation for motor vehicles, which has a piston which has a signaling element and is accommodated in a cylinder housing so as to be longitudinally displaceable, on the outer circumference of which a position sensor is fastened, by means of which an axial position of the signaling element and thus of the piston in the cylinder housing can be detected, a base is provided on the outer circumference of the cylinder housing, which forms a support surface against which the position sensor rests flat and which is adjoined by webs which hold the position sensor in a form-fitting manner on the cylinder housing.

Because the position sensor on the cylinder housing rests flat against the support surface of a base of a defined thickness, the radial distance between the position sensor on the cylinder housing and the signal element on the piston is set in a defined manner and kept constant. At the same time, the webs adjacent to the support surface of the base ensure a defined, positive-locking fixation of the position sensor both in the circumferential direction and in the axial direction of the cylinder housing. As a result, the position sensor is easily held in a clearly defined spatial positional relationship to the cylinder housing, even when subjected to vibrations, for example when a motor vehicle is in operation, so that the position sensor can always be used to correctly sense the signal element provided on the piston and thus the axial piston position.

According to the teaching of claim 2, it is expedient to provide in the longitudinal and/or transverse direction of the cylinder housing to both

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On each side of the support surface there is a web protruding above the support surface.

According to claim 3, the position sensor is preferably detachably locked to the cylinder housing. By providing a locking or snap connection, the position sensor can be advantageously easily mounted on the cylinder housing, whereby the position sensor can be pre-wired and pre-mounted, hanging on a motor vehicle's wiring harness, for example, independently of the hydraulic cylinder, so that after joining a pedal module to a clutch master cylinder, for example, the position sensor can be mounted to the cylinder housing by simply pressing it on. By detachably locking the position sensor to the cylinder housing, it is advantageously possible to separate the position sensor from the hydraulic cylinder if the position sensor and/or the hydraulic cylinder needs to be removed for repair purposes or for replacement.

According to the teaching of claim 4, at least two webs arranged opposite one another with respect to the support surface are expediently designed as resilient retaining webs, which are each provided with a locking profile on their mutually facing sides, which engages behind the position sensor or a section thereof when the position sensor is mounted. This design is preferred here, although the resilient retaining webs could also each be provided with a locking recess on their mutually facing sides, which serves to accommodate an associated locking profile on the position sensor that is complementary in cross section.

The locking profile can, for example, have a substantially semicircular cross-section. Both in terms of manufacturing technology and to achieve assembly and disassembly forces that are largely independent of manufacturing tolerances.

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for example, are independent in the length of the position sensor, it is preferred if the locking profile, as specified in claim 5, has a substantially triangular cross-section, with an inclined surface section facing the support surface and an inclined surface section facing away from the support surface. The inclined surface sections facing the support surface serve to positively fix the position sensor against the support surface on the cylinder housing, while the inclined surface sections facing away from the support surface ensure that the position sensor can be easily positioned and centered with respect to the resilient retaining webs and, as a result, the resilient retaining webs can be pushed over. Both the force with which the position sensor is held on the cylinder housing and the force required to mount the position sensor on the cylinder housing can be easily preset to suit the respective requirements by changing the locking profile geometry with respect to the angle of inclination of one or both surface sections and/or the height of the locking profile.

According to claim 6, further webs, i.e. webs not designed as holding webs, are designed as guide webs, on whose smooth inner surfaces the position sensor rests flatly when mounted. This means that the snap-in or release force can be kept within predetermined limits when mounting or dismounting the position sensor. On the other hand, the flat contact of the position sensor on the smooth inner surfaces of the guide webs serves to hold the position sensor between the guide webs in a defined and play-free manner. Finally, when mounting the position sensor on the cylinder housing, the position sensor can advantageously be inserted between the guide webs with essentially no force and can be moved along the guide webs with only a small axial pushing force until one end of the position sensor is at the associated

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The retaining web comes into contact below the corresponding locking profile, so that only the retaining web arranged opposite this retaining web needs to be overpressed with a small amount of force in order to fix the position sensor to the cylinder housing as defined above.

The protection claim 7 provides that the guide webs run in the longitudinal direction of the cylinder housing, while the holding webs run in the transverse direction of the cylinder housing, which advantageously leads to lower joining forces compared to the reverse arrangement.

In an alternative embodiment of the hydraulic cylinder according to claim 8, in the assembled state of the position sensor, at least one of the retaining webs is accommodated in an associated recess in the position sensor, the retaining web having a stop surface at each of its longitudinal ends, against which a respective associated guide surface of the recess in the position sensor rests. Thus, the same retaining web or the same retaining webs serve in an advantageously simple manner not only for the positive fixing of the position sensor, which comes to rest flat on the support surface of the base, in a direction perpendicular to the longitudinal extension direction of the retaining webs, but at the same time for the positive fixing of the position sensor in the longitudinal extension direction of the retaining webs.

According to claim 9, the webs are preferably formed in one piece with the base, in a particularly simple manufacturing technique. The base is also preferably formed in one piece with the cylinder housing, in a particularly simple manufacturing technique, as stated in claim 10. However, it would also be conceivable to have a base manufactured separately from the cylinder housing, which could then be attached to the cylinder housing, for example by gluing or welding.

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It would also be possible to retrofit existing cylinder housings to form a hydraulic cylinder with a device for detecting the piston position.

According to the teaching of claim II, the support surface for the position sensor is preferably flat, so that the support surface can be easily formed and a flat contact of the position sensor with the support surface can be ensured in a simple manner.

Claim 12 provides that the base is provided with at least one recess, starting from the support surface for the position sensor, in particular for receiving a functional section of the position sensor. Such a functional section of the position sensor can advantageously be a sensor or switch, possibly accommodated in a housing of the position sensor, which, due to its accommodation in the recess in the base support surface, can be positioned on the cylinder housing with the smallest possible radial distance to the signal element on the piston, so that the best possible signal level, e.g. magnetic, is always provided. Furthermore, in particular in the case of a cylinder housing injection-molded from plastic according to claim 14, on which the base is formed in one piece according to claim 10, a functional design of the cylinder housing can be achieved by means of a suitable choice of the position and number of recesses in the base support surface in such a way that, on the one hand, the housing wall thickness is sufficient to meet the mechanical strength requirements, but on the other hand, no excessive wall thickness fluctuations occur on the cylinder housing, which could lead to undesirable local position and shape tolerance problems. Furthermore, by means of a suitable choice of the position of the recess(es) in the base support surface, an assembly aid can also be created in such a way that the position sensor can only be attached to the cylinder housing in a predetermined alignment or position orientation.

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can be mounted. Finally, the provision of recesses in the base support surface also promotes a compact design.

According to the teaching of claim 13, the position sensor is essentially rectangular when viewed from above, so that the base and its support surface on the cylinder housing can also have an advantageously simple and easy-to-form geometry.

If the cylinder housing of the hydraulic cylinder is finally injection-molded from plastic in accordance with protection claim 14, this has the advantage, among other things, that the wall of the cylinder housing does not have a shielding effect that could be detrimental to the correct detection of the axial position of the magnetic signal element, for example, by the position sensor, which operates inductively or is equipped with a Hall sensor. In addition, the cylinder housing can thus be manufactured cost-effectively without the need for tooling, i.e. without the need for complex post-processing steps.

Last but not least, the use of plastic as a housing material also brings weight advantages.

The invention is explained in more detail below using preferred embodiments with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a cylinder housing of a hydraulic cylinder according to the invention according to a first embodiment, on which a position

sensor of a device for detecting the axial piston position,

Fig. 2 is a plan view of the cylinder housing shown in Fig. 1 with mounted position sensor,

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Fig. 3 is a perspective view of the cylinder housing according to Fig. 1, enlarged in scale and with a different viewing angle compared to the view in Fig. 1, from which the position sensor has been removed,

Fig. 4 is an enlarged partial sectional view of the cylinder housing according to Fig. 1 along the section line IV-IV in Fig. 3,

Fig. 5 is an enlarged and interrupted partial sectional view of the cylinder housing according to Fig. 1 along the section line V-V in Fig. 3 and

Fig. 6 is a perspective view of a cylinder housing of a hydraulic cylinder according to the invention according to a second embodiment, on which a position sensor of a device for detecting the axial piston position is mounted.

In the figures, only the cylinder housing 10, 10' of a hydraulic cylinder, in the embodiment shown a master cylinder of a hydraulic clutch actuation, is shown. The piston assembly arranged in or on the cylinder housing 10, 10' in the fully assembled state of the master cylinder, which can be designed in a conventional manner, is not shown to simplify the illustration. At this point, it should only be noted that the piston assembly has, among other things, a piston accommodated in the cylinder housing 10, 10' so that it can be moved longitudinally, for example by means of a clutch pedal via a piston rod in the cylinder housing 10, 10', in order to generate a hydraulic pressure in a pressure chamber of the cylinder housing 10, 10' in a manner known per se, which can be applied to a slave cylinder via a pressure connection 12, 12' of the hydraulic cylinder, which

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which in turn is operatively connected to a release mechanism of a dry friction clutch. The piston is also provided with a signal element, for example in the form of a magnetic ring attached to the piston, the axial position of which in the cylinder housing 10, 10' can be detected through the wall of the cylinder housing 10, 10' by means of a position sensor 16, 16' attached to the outer circumference 14, 14' of the cylinder housing 10, 10' in a manner to be described below in order to determine the axial position of the piston. As will be explained in more detail below, a base 18, 18' is provided for this purpose on the outer circumference 14, 14' of the cylinder housing 10, 10', which forms a support surface 20, 20', against which the position sensor 16, 16' rests flat and which is bordered by webs 22, 24, 26, 28 or 22', 24', which hold the position sensor 16, 16' in a form-fitting manner on the cylinder housing 10, 10'.

As shown in Fig. 1 to 3, the cylinder housing 10, which is injection-molded from plastic and has a longitudinally stepped diameter, has an assembly opening 30 for the piston assembly (not shown) at its end facing away from the pressure connection 12, which is surrounded by a plurality of locking openings 32 for fastening the piston assembly in the cylinder housing 10. When the piston assembly is assembled, the piston rod, which is operatively connected to the piston, protrudes from the assembly opening. The cylinder housing 10 is also provided with two bearing points 34, which serve to fasten the master cylinder to a pedal bracket in the motor vehicle, for example. Finally, the cylinder housing 10 also has a follow-up or pressure compensation connection 36, which is hydraulically connected to a follow-up container in a manner known per se when the master cylinder is connected.

According to Figs. 1 to 5, the base 18 is formed integrally with the cylinder housing 10 and extends in the longitudinal direction of the cylinder housing 10 over a central section

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the same, the inner circumference of which forms a running surface 38 for the piston. In the illustrated embodiment, the base 18 forms a flat support surface 20 for the position sensor 16, which is parallel to the longitudinal axis of the cylinder housing 10 (Fig.

5) and, viewed in cross section (Fig. 4), is aligned perpendicular to the radial direction or essentially tangential to the outer circumference 14. The webs 22, 24, 26, 28, which border on or frame the support surface 20, are formed integrally with the base 18.

As shown in particular in Fig. 3, in the illustrated embodiment, a web 22, 24, 26, 28 is provided in the longitudinal and transverse direction of the cylinder housing 10 on both sides of the support surface 20 for the position sensor 16, protruding outwards beyond the support surface 20. The position sensor 16 can be releasably locked to the cylinder housing 10, for which purpose the two webs 22, 24 arranged opposite one another with respect to the support surface 20 in the longitudinal direction of the cylinder housing 10 and running in the transverse direction of the cylinder housing 10 are designed as resilient holding webs, which are each provided on their sides facing one another with a locking profile 40 extending over the entire holding web 22 or 24, which engages behind the position sensor 16 when the position sensor 16 is mounted. The locking profile 40 of the holding webs 22, 24 extending essentially over the entire width of the support surface 20 has, according to Figs. 4 and 5, a substantially triangular cross-section, with an inclined surface section 42 facing the support surface 20 and an inclined surface section 44 facing away from the support surface 20.

The clear distance between the locking profiles 40 on the opposite holding webs 22, 24 is slightly smaller than the length of the position sensor 16, which is essentially rectangular when viewed from above (Fig. 2), while the distance between the locking profiles 40 and the support surface 20 essentially corresponds to the thickness of the position sensor 16 on these

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It is clear that the retaining webs 22, 24 with their smooth inner surfaces 46 hold the position sensor 16 locked to the cylinder housing 10 in the longitudinal direction of the cylinder housing 10 without play or with little play, while the locking profiles 40 on the retaining webs 22, 24, more precisely the inclined surface sections 42 of the locking profiles 40 facing the support surface 20, hold the position sensor 16 in flat contact with the support surface 20. The inclined surface sections 44 of the locking profiles 40 facing away from the support surface 20 can serve to center the position sensor 16 when the position sensor 16 is locked to the cylinder housing 10. On the other hand, when the position sensor 16 is mounted on the cylinder housing 10, by applying a compressive force to the position sensor 16 in the direction of the cylinder housing 10 on the respective retaining web 22, 24, they cause a force component directed outwards, i.e. in Fig. 5 on the retaining web 22 to the left or on the retaining web 24 to the right, which leads to an elastic springing up or away of the respective retaining web 22, 24 before the respective locking profile 40 locks behind the position sensor 16 with the respective retaining web 22, 24 springing back when the position sensor 16 comes to rest flat on the support surface 20. On their sides facing away from each other, the retaining webs 22, 24 are bevelled towards their free ends, as shown in Fig. 5, so that the retaining webs 22, 24 taper towards their free ends, which promotes the elastic springing up or away of one or both retaining webs 22, 24 when the position sensor 16 is locked to the cylinder housing 10 or is released from its locking connection to the cylinder housing 10.

The other two webs 26, 28, which are arranged opposite one another in the transverse direction of the cylinder housing 10 with respect to the support surface 20 and extend in the longitudinal direction of the cylinder housing 10, are designed as guide webs, on whose smooth inner surfaces 48 the position sensor 16 in the assembled state

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lies flat. Accordingly, the clear distance between the guide webs 26, 28 corresponds to the width of the position sensor 16. The guide webs 26, 28, which protrude less beyond the support surface 20 than the holding webs 22, 24 according to Fig. 4 and 5, each have a centering bevel 50 on their free ends on their sides facing each other, which simplifies the assembly of the position sensor 16 on the cylinder housing 10. The length of the guide webs 26, 28 can be selected according to the respective requirements so that the guide webs 26, 28 on the one hand allow easy assembly or disassembly of the position sensor 16 on the cylinder housing 10 and on the other hand ensure a secure and play-free or low-play positive fixing of the position sensor 16 on the cylinder housing 10 in the transverse or circumferential direction of the cylinder housing 10. In the illustrated embodiment, one guide web 26 is shorter than the other guide web 28, which enables better handling of the position sensor 16 when it is to be released from the locking connection to the cylinder housing 10.

As shown in Fig. 3 to 5, the base 18 is provided with two recesses 52, 54 starting from the support surface 20 for the position sensor 16, which serve to accommodate functional sections of the position sensor 16, not shown in detail here.

From Fig. 5 it can be seen that the recesses 52, 54 allow a positioning of the functional sections of the position sensor 16 in the immediate vicinity of the running surface 38 of the cylinder housing 10.

In this context, it should be noted that the position sensor 16 can have a Hall sensor in a manner known per se, by means of which the position of the magnetic ring attached to the piston can be detected. Furthermore, the position sensor 16 can have an evaluation electronics connected to the Hall sensor, which, when the magnetic ring is sensed by means of the Hall sensor,

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Sensor emits an electrical signal which can be picked up by the position transmitter 16 via a connection contact part 56 of the position transmitter 16.

Fig. 6 shows a cylinder housing 10' of a master cylinder according to a second embodiment, with which a position sensor 16' is locked. The second embodiment will be described below only insofar as it differs from the first embodiment and appears necessary for understanding the present invention, wherein identical or corresponding parts compared to the first embodiment are provided with reference numerals which are supplemented by a prime (').

The cylinder housing 10', which can be mounted on a pedal bracket of a motor vehicle, for example, by means of locking lugs 58' and a fastening flange 60', also has a base 18', which is injection-molded in one piece with the cylinder housing 10' from plastic in the area of the running surface for the piston on the outer circumference 14' and which forms the support surface 20' for the position sensor 16'. In contrast to the first embodiment, the second embodiment provides two holding webs 22', 24' which, viewed in the transverse direction of the cylinder housing 10', are arranged opposite one another with respect to the support surface 20' and run in the longitudinal direction of the cylinder housing 10', of which only one holding web 22' can be seen in Fig. 6.

Just like the holding webs 22, 24 of the first embodiment, the holding webs 22', 24' of the second embodiment have on their mutually facing sides a locking profile (not visible here) for releasably securing the position sensor 16' to the cylinder housing 10', wherein the locking profile engages in a recess (not shown) of the position sensor 16' in order to engage behind a section of the position sensor 16'.

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However, guide webs corresponding to the first embodiment are missing in the second embodiment. Instead, in the assembled state of the position sensor 16', the holding webs 22', 24' are accommodated in associated recesses 62* in the position sensor 16', with each holding web 22', 24' having a stop surface 64' at its longitudinal ends, against which a respective associated guide surface 66' of the recess 62' in the position sensor 16' rests.

It can be seen that the locking profiles on the holding webs 22', 24' hold the position sensor 16' in flat contact with the support surface 20' of the base 18', while the holding webs 22', 24' with their inner surfaces facing each other and the end stop surfaces 64' ensure a positive fixing of the position sensor 16' on the cylinder housing 10' both transversely and longitudinally of the cylinder housing 10'.

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List of reference symbols

10, 10 ¹ Cylinder housing 12, 12' Pressure connection 14, 14" Outer circumference 16, 16' Position sensor 18, 18' base 20, 20' Support surface 22, 22' Holding bridge 24, 24' Holding bridge 26 Guide bridge 28 Guide bridge 30, 30' Mounting opening 32, 32' Latching opening 34 Storage location 36, 36' Pressure equalization connection 38 Tread 40 Locking profile 42 Area section 44 Area section 46 Inner surface 48 Inner surface 50 Centering bevel 52 Recess 54 Recess 56, 56' Connection contact part 58' locking lug 60' Mounting flange 62' Recess 64' Stop surface 66' Guide surface

Claims (14)

1. Hydraulic cylinder, in particular a master or slave cylinder for a hydraulic clutch actuation for motor vehicles, with a piston which has a signal element and is accommodated in a cylinder housing ( 10 , 10 ') in a longitudinally displaceable manner, on the outer circumference ( 14 , 14 ') of which a position sensor ( 16 , 16 ') is fastened, by means of which an axial position of the signal element and thus of the piston in the cylinder housing ( 10 , 10 ') can be detected, characterized in that a base ( 18 , 18 ') is provided on the outer circumference ( 14 , 14 ') of the cylinder housing ( 10 , 10 '), which forms a support surface ( 20 , 20 ') against which the position sensor ( 16 , 16 ') rests flat and has webs ( 22 , 24 , 26 , 28 ; 22 ', 24 ') which hold the position sensor ( 16 , 16 ') in a form-fitting manner on the cylinder housing ( 10 , 10 '). 2. Hydraulic cylinder according to claim 1, characterized in that in the longitudinal and/or transverse direction of the cylinder housing ( 10 , 10 ') on both sides of the support surface ( 20 , 20 ') a web ( 22 , 24 , 26 , 28 ; 22 ', 24 ') projecting over the support surface ( 20 , 20 ') is provided. 3. Hydraulic cylinder according to claim 1 or 2, characterized in that the position sensor ( 16 , 16 ') is preferably releasably locked to the cylinder housing ( 10 , 10 '). 4. Hydraulic cylinder according to one of the preceding claims, characterized in that at least two webs ( 22 , 24 ; 22 ', 24 ') arranged opposite one another with respect to the support surface ( 20 , 20 ') are designed as resilient holding webs which are each provided on their mutually facing sides with a locking profile ( 40 ) which, in the mounted state of the position sensor ( 16 , 16 '), engages behind the position sensor ( 16 , 16 ') or a section thereof. 5. Hydraulic cylinder according to claim 4, characterized in that the locking profile ( 40 ) has a substantially triangular cross-section, with an inclined surface section ( 42 ) facing the support surface ( 20 ) and an inclined surface section ( 44 ) facing away from the support surface ( 20 ). 6. Hydraulic cylinder according to claim 4 or 5, characterized in that further webs ( 26 , 28 ) are designed as guide webs, on whose smooth inner surfaces ( 48 ) the position sensor ( 16 ) rests flat in the assembled state. 7. Hydraulic cylinder according to claim 6, characterized in that the guide webs ( 26 , 28 ) run in the longitudinal direction of the cylinder housing ( 10 ), while the holding webs ( 22 , 24 ) run in the transverse direction of the cylinder housing ( 10 ). 8. Hydraulic cylinder according to claim 4 or 5, characterized in that in the assembled state of the position sensor ( 16 ') at least one of the holding webs ( 22 ', 24 ') is received in an associated recess ( 62 ') in the position sensor ( 16 '), the holding web ( 22 ', 24 ') having at each of its longitudinal ends a stop surface ( 64 ') against which a respective associated guide surface ( 66 ') of the recess ( 62 ') in the position sensor ( 16 ') rests. 9. Hydraulic cylinder according to one of the preceding claims, characterized in that the webs ( 22 , 24 , 26 , 28 ; 22 ', 24 ') are formed integrally with the base ( 18 , 18 '). 10. Hydraulic cylinder according to one of the preceding claims, characterized in that the base ( 18 , 18 ') is formed integrally with the cylinder housing ( 10 , 10 '). 11. Hydraulic cylinder according to one of the preceding claims, characterized in that the support surface ( 20 ) for the position sensor ( 16 ) is flat. 12. Hydraulic cylinder according to one of the preceding claims, characterized in that the base ( 18 ), starting from the support surface ( 20 ) for the position sensor ( 16 ), is provided with at least one recess ( 52 , 54 ), in particular for receiving a functional section of the position sensor ( 16 ). 13. Hydraulic cylinder according to one of the preceding claims, characterized in that the position sensor ( 16 ) is substantially rectangular when viewed in plan view ( Fig. 2). 14. Hydraulic cylinder according to one of the preceding claims, characterized in that the cylinder housing ( 10 , 10 ') is injection-molded from plastic.