Clutch with position detection means, method for manufacturing the same, device equipped with a clutch with position detection means, and switching method using a clutch with position detection means

Abstract

To provide a technology that enables proper and smooth switching of teeth in a high-speed / low-speed switching clutch by allowing teeth to be aligned in the appropriate position, thereby avoiding switching delays or failures, tooth wear, and other issues. [Solution] The clutch 10 with position detection means is configured to include a first switching target 1, a second switching target 2, and an armature 3 provided between them and used for switching, wherein the armature 3 is formed to have a first switching structure 4 and a second switching structure 5 that are compatible with the corresponding first switching target 1 and second switching target 2, respectively, and a position detection means 6 for detecting the position of the switching target is provided on at least one of the first switching target 1 or the second switching target 2.

Description

Technical Field

[0001] The present invention relates to a clutch with a position detection means, a manufacturing method thereof, a clutch-equipped device with a position detection means, and a switching method using the clutch with a position detection means. In particular, it relates to a technique for improving the gear meshing accuracy when switching gears of a clutch having a low-speed gear and a high-speed gear.

Background Art

[0002] FIG. 8 is a side view explanatory diagram showing the basic configuration of a conventional high-speed / low-speed switching clutch in a speed reduction mechanism using a planetary gear or the like. As shown in the figure, in order to exhibit different characteristics of low speed / high torque and high speed / low torque using a single motor, a conventional high-speed / low-speed switching clutch 810 is provided with a high-speed side fixed tooth 82 and a low-speed side fixed tooth 81 that rotate in conjunction with the motor shaft 88. The two fixed teeth 81 and 82 are arranged opposite to each other with the armature 83 sandwiched therebetween, and have different specifications such as the number of teeth. As shown in the figure, the armature 83 is formed with a first switching structure 84 and a second switching structure 85 corresponding to each of the fixed teeth 81 and 82 so as to mesh with each fixed tooth.

[0003] The switching of the reduction ratio, that is, the movement of the armature between the fixed teeth, is performed by meshing and fixing one of the fixed teeth, and the high-speed / low-torque rotation and the low-speed / high-torque rotation are switched. Specifically, based on the detection result by a rotation sensor attached to the motor, the position of the fixed tooth is estimated, the fixed tooth is moved to a position where the teeth of the armature and the fixed tooth do not interfere, the appropriate timing of the armature switching is measured, the teeth of both are meshed, and the switching is executed.

[0004] Many patent applications have been filed regarding clutches in reduction mechanisms using planetary gears. For example, Patent Document 1, listed below, discloses a configuration in a vehicle having two electric motors connected via a planetary gear mechanism, in which the first electric motor is connected to the first sun gear, and the second electric motor is connected to the second sun gear or ring gear via a connection switching mechanism, as a drive system that can obtain greater driving force at low speeds. As a result, when the vehicle is driven by the first and second electric motors, when the second electric motor is connected to the second sun gear, the rotational speed of the carrier is equal to or between the rotational speeds of the first and second sun gears. On the other hand, when the second electric motor is connected to the ring gear, the second sun gear is fixed by a one-way clutch, and the rotational speed of the carrier becomes slower than the rotational speed of the first sun gear and ring gear. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-133876, "Drive System for Electric Vehicles" [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As mentioned above, in conventional high-speed / low-speed clutches, the switching (movement) of the armature between each fixed tooth is performed by determining the appropriate timing based on the position of the fixed tooth estimated from the detection results of a motor-equipped rotation sensor, and then engaging the teeth of both. However, this estimation method is not sufficient, and the switching does not always occur at the appropriate timing.

[0007] In other words, in the conventional method of estimating the position of the fixed teeth using a motor-mounted rotation sensor, the gear meshing may not align, resulting in a positional relationship where the convex teeth of the armature and the convex teeth of the fixed teeth interfere with each other. This can lead to problems such as inability to switch gears, delays in switching, or tooth wear. Technology is needed to eliminate these problems.

[0008] Therefore, the problem that this invention aims to solve is to eliminate the problems of the conventional technology and provide a technology that improves the reliability of gear alignment in a high-speed / low-speed switching clutch, which allows gear alignment to be performed at the appropriate position, thereby avoiding malfunctions such as delays or failures in switching and gear wear, and enabling appropriate and smooth switching. [Means for solving the problem]

[0009] As a result of considering the above problems, the inventors of this invention have come up with a method in which, instead of using a rotation sensor (angle sensor) attached to the motor as a position detection means to estimate the position, angle sensors are attached to the fixed teeth (gears) that are to be switched by the clutch, and the clutch is switched based on the data obtained, at the timing when the gear to be switched and the armature are aligned. Furthermore, the inventors have come up with the idea that by aligning the 0 position of the rotation sensor with the position of the fixed teeth before attaching the rotation sensor, the position of the teeth can be detected accurately, and that by using parameters such as the width and period of the teeth to determine whether the alignment is correct, the values ​​required as the resolution of the rotation sensor can be easily calculated.

[0010] In other words, in order to improve the accuracy and reliability of the alignment, a position detection means for tooth position estimation is used as in the conventional method, but as a result of diligent consideration of its mounting position, mounting method and required performance, satisfactory results were obtained, and based on this, the present invention was completed. That is to say, the invention claimed in this application, or at least disclosed invention, as a means of solving the above problems is as follows.

[0011] [1] A clutch comprising a first switching target, a second switching target, and an armature provided between the two and used for switching, The armature is shaped to fit each corresponding switching target, At least one of the items subject to the first replacement or the item subject to the second replacement, A position detection means is provided for detecting the position of the object to be switched. A clutch with position detection means, characterized by the above. [2] The clutch with position detection means according to [1], characterized in that the first replacement target and the second switching target are gears that mesh with the armature. [3] The clutch with position detection means according to [2], characterized in that the first gear to be switched is a low-speed gear and the second gear to be switched is a high-speed gear. [4] A clutch with a position detection means according to any one of [1], [2], or [3], characterized in that the position detection means is a rotation sensor. [5] A clutch with a position detection means according to any one of [1], [2], or [3], characterized in that the position detection means is a hollow shaft resolver. [6] The clutch with position detection means according to any one of [1], [2], or [3], characterized in that the position detection means is a magnetic encoder.

[0012] [7] The position detection means is a rotation sensor, The aforementioned all-changeable object and the second-changeable object are gears that mesh with the armature, The rotation sensor in question is, It has an angular resolution that satisfies the criteria for determining whether or not the armature and gear mesh, which are calculated based on the dimensions of the armature and the gear. A clutch with position detection means according to any one of [1], [2], or [3], characterized in that [8] The clutch with position detection means according to [7], characterized in that the meshing determination criterion is a meshing determination range calculated from the gear period width gc, which is the period width of the gear, the gear width gw, which is the width of the armature gear aw. [9] The clutch with position detection means according to claim 7, characterized in that it is equipped with a switching determination execution means that determines the timing of the meshing between the gear and the armature, which are the target of switching, based on the position detection result of the rotation sensor, according to the meshing presence or absence determination criterion, and performs switching by the armature.

[10] A clutch device equipped with a position detection means, characterized by comprising a clutch with a position detection means as described in any of [1], [2], [3], [8], or [9].

[11] A method for determining and executing the switching of the object to be switched using a clutch with position detection means as described in [9], Based on the position detection result of the switching target by the rotation sensor, A switching determination process that determines the timing of the meshing between the gear and the armature, which are the targets of the switching, based on the meshing presence or absence determination criteria, Based on the judgment made through the switching decision process, The system is characterized by comprising a switching execution process that performs the switching by the armature, A switching method using a clutch with a position detection mechanism.

[12] A method for manufacturing a clutch with position detection means as described in any of [1], [2], [3], [8], or [9], An installation process in which the position detection means is attached to the switching target by aligning the specific position of the position detection means with the specific position of the switching target, The system includes an initial setup process that sets the position detection means to an operational state after the installation process. A method for manufacturing a clutch with a position detection means, characterized in that the initial setup process enables the acquisition of the relative position of the switching target with respect to the armature. The method for manufacturing a clutch with a position detection means according to

[12] , wherein the position detection means is a hollow shaft resolver. The method for manufacturing a clutch with a position detection means according to

[12] , wherein the position detection means is a magnetic encoder.

Advantages of the Invention

[0013] Since the clutch with a position detection means, the manufacturing method thereof, the clutch-equipped device with a position detection means, and the switching method using the clutch with a position detection means according to the present invention are configured as described above, according to these, in a high-speed / low-speed switching clutch, the clutch can be switched at the timing when the gear to be switched and the armature are aligned, that is, the tooth engagement can be performed at an appropriate position. Thereby, it is possible to avoid problems such as switching delay, inability to switch, and tooth wear, and to achieve appropriate and smooth switching. Therefore, the reliability of the engagement can be enhanced.

[0014] Further, according to the clutch with a position detection means and the like of the present invention, since the rotation sensor can be attached after aligning the 0 position of the rotation sensor and the position of the fixed teeth, it is possible to detect the accurate tooth position, which is a prerequisite for accurate switching. Also, by using a specific parameter for determining the suitability of the engagement, it is possible to easily calculate the value required as the resolution of the rotation sensor, which is a prerequisite for accurate switching.

Brief Description of the Drawings

[0015] [Figure 1] It is an explanatory view conceptually showing the basic configuration of the clutch with a position detection means of the present invention. [Figure 2] It is a cross-sectional view explanatory drawing showing the main part configuration of the clutch with a position detection means of the present invention, where the first switching target and the second switching target are gears. [Figure 3] It is an explanatory view of an end face view from the input shaft side showing the main part configuration of the clutch with a position detection means of the present invention, where the position detection means is a hollow shaft resolver. [Figure 4] Figure 2 is an explanatory diagram showing an example of parameters used to calculate the engagement determination range in the clutch with position detection means of the present invention. [Figure 5] This is an explanatory diagram showing an example of the matching judgment range calculated using the parameters shown in Figure 4. [Figure 6] This flowchart shows the basic configuration of the switching method using a clutch with a position detection means according to the present invention. [Figure 7] This flowchart shows the basic configuration of the clutch manufacturing method with position detection means according to the present invention. [Figure 8] This is a side view diagram illustrating the basic configuration of a conventional high-speed / low-speed switching clutch in a reduction mechanism using planetary gears, etc. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below with reference to the drawings. Figure 1 is a conceptual diagram illustrating the basic configuration of the clutch with position detection means of the present invention. As shown in the figure, the clutch with position detection means 10 comprises a first switching target 1, a second switching target 2, and an armature 3 provided between them and used for switching. The armature 3 is formed to fit the corresponding first switching target 1 and second switching target 2, respectively, and is formed to include a first switching structure 5 and a second switching structure 6. A characteristic feature of the configuration is that at least one of the first switching target 1 or the second switching target 2 is provided with a position detection means 6 for detecting the position of the switching target. Note that in this figure, the configuration in which the position detection means 6 is provided on the second switching target 2 is shown.

[0017] The operation of the clutch 10 with position detection means of the present invention, configured as described above, will now be explained. The first switching target 1 and the second switching target 2 are switched by an armature 3 provided between them. When the switching target is the first switching target 1, the switching by the armature 3 is performed by connecting and temporarily fixing the first switching structure 5, which is compatible with the first switching target 1, to the first switching target 1. On the other hand, when the switching target is the second switching target 2, the switching by the armature 3 is performed by connecting and temporarily fixing the second switching structure 6, which is compatible with the second switching target 2, to the second switching target 2.

[0018] In the clutch 10 with position detection means of the present invention, the position detection means 6 is provided on at least one of the first switching target 1 or the second switching target 2 (on the second switching target 2 in the figure). Therefore, the position of the switching target on which the position detection means 6 is provided is not indirectly estimated, but directly detected. Based on this, the clutch can be switched at an appropriate timing for connecting the switching target 1 or 2 with the armature 3, thereby avoiding problems such as delays or failures in switching and tooth wear, and achieving smooth switching.

[0019] Figure 2 is a cross-sectional view illustrating the main components of the clutch with position detection means of the present invention, in which the first and second switching targets are gears. As shown in the figure, the clutch with position detection means 210 comprises a first switching target 21, a second switching target 22, and an armature 23 provided between them and used for switching. The armature 23 is formed to fit the corresponding switching targets, the first switching target 21 and the second switching target 22, respectively, that is, it is formed to include a first switching structure 25 and a second switching structure 26, and at least one of the first switching target 21 or the second switching target 22 is provided with a position detection means 26 for detecting the position of the switching target.

[0020] As shown in the figure, the first changeable object 21 and the second changeable object 22 can be gears that mesh with the armature 23. Therefore, the first changeable structure 24 and the second changeable structure 25 of the armature 23 are also corresponding gears.

[0021] The configuration shown in Figure 2 is considerably similar to the configuration shown in Figure 7 of the prior art, but the distinguishing feature of the present invention shown in Figure 2 is the inclusion of a position detection means 26. The figure shows a configuration in which the position detection means 26 is provided on the second switching target 22. In Figure 2, the first switching target 21 is a low-speed gear, and the second switching target 22 is a high-speed gear. That is, high-speed rotation and low-speed rotation can be switched by switching the armature 23 and fixing one of them.

[0022] In this structure, if gear switching is performed at the timing when the teeth of the armature 23 and each switching target 21 or 22 are aligned, gear wear can be suppressed and speed switching can be performed reliably. This can be achieved by providing position detection means 26 on both or at least one of the first switching target 21 and the second switching target 22 (in the figure, it is installed on the second switching target 22). A rotation sensor can be used as the position detection means 26, but a magnetic encoder can be preferably used, for example.

[0023] Figure 3 is an explanatory diagram showing the main components of the clutch with position detection means of the present invention, in which the position detection means is a hollow shaft resolver, viewed from the input shaft (motor shaft) side. As shown in the figure, a hollow shaft resolver can also be suitably used as the position detection means 36 of this clutch with position detection means 310. As the position detection means, a rotation sensor such as a hollow shaft resolver (36) or a magnetic encoder (26 in Figure 2) can be used to acquire the position of the teeth of gears 21, 22, etc., as angular data.

[0024] In order to determine whether the gears are meshed correctly from the angle data, the rotation sensor must have a certain level of angular resolution. In other words, it must have an angular resolution that satisfies the criteria for determining whether the armature and gears are meshed (mesh detection criteria). Hereafter, the minimum resolution required to determine whether the gears are meshed correctly will be referred to as the "required resolution."

[0025] Figure 4 is an explanatory diagram showing an example of parameters used to calculate the meshing determination range in the clutch with position detection means of the present invention shown in Figure 2. The configuration shown in Figure 4 is basically the same as the configuration shown in Figure 2, but the reference numerals for the components are changed for explanation. As shown in the figure, the meshing determination criterion for the clutch with position detection means 410 can be the meshing determination range calculated from the gear period width gc, the gear width gw, and the armature gear width aw. In other words, the required resolution depends on the gear period width gc, the gear width gw, and the armature gear width aw, so by explaining this relationship, it is possible to select a rotation sensor with appropriate specifications.

[0026] As a prerequisite, the gear period width GC and the armature gear period width AC, which is the period width of the armature gear, are equal. This is because it is a condition under which both gears mesh. In other words; gc=ac In addition, the sum of the gear width GW and the armature gear width AW is smaller than the gear period width GC. In other words; gc>gw+aw

[0027] "Gear meshing" refers to a state where the entire gear width gw of the teeth fits within the recess of the armature gear. Therefore, in Figure 4, if the leftmost point of the gear width gw is the judgment reference point P, then if it falls within the range L to R shown below, the gears are "meshing". This is the "meshing judgment range". L: Leftmost position of the armature gear period width ac R: Position located at a distance of gear width gw and armature gear width aw from the right end of the armature gear period width ac. In other words, if the leftmost position of the armature gear period width ac is set to 0, the size of the "meshing detection range" is: ac-(gw+aw) or gc-(gw+aw) That is the case.

[0028] Furthermore, gear meshing can be determined from the angle data obtained by the rotation sensor attached to the clutch with position detection means of the present invention, which has been selected. Note that the pitch and width of the armature are not necessary for calculating the criteria for determining whether or not the gears are meshing.

[0029] Figure 5 is an explanatory diagram showing an example of the meshing determination range calculated using the parameters shown in Figure 4, and is an example of the range in which the gears are meshed. In the clutch 410 with position detection means shown in Figure 5, the second switching target 42 is a high-speed gear, and is shown as "high-speed side tooth" in the figure. The required resolution, which is necessary to determine whether the current angle of the switching target detected by the rotation sensor falls within the meshing determination range, is at least less than the meshing determination range. In other words, if the required resolution is Rr, Rr <ac-(gw+aw) または、Rr<gc-(gw+aw) That is the case.

[0030] However, it is more desirable that the required resolution be such that it can measure less than half of the meshing determination range. Therefore, the required resolution Rr is, Rr≦{gc-(gw+aw)} / 2 [deg] Rr≦360[deg]×2 / {gc-(gw+aw)} [step] or Rr≦{ac-(gw+aw)} / 2 [deg] Rr≦360[deg]×2 / {ac-(gw+aw)} [step] This is the result. Using the above formula, you can select the angle sensor that should be attached to the gear (the object to be switched).

[0031] The clutch with position detection means of the present invention can be configured to include a switching decision execution means that determines the timing of meshing between the gear to be switched and the armature, which is the gear to be switched, based on the position detection result of the gear to be switched by the rotation sensor, according to the meshing presence or absence determination criteria, and performs switching by the armature. In other words, the switching decision execution means determines the timing of meshing between the gear and the armature based on the position detection result of the gear to be switched by the rotation sensor, according to the meshing presence or absence determination criteria, and performs switching by the armature.

[0032] A clutch device equipped with a position detection means, which includes a clutch having any of the configurations described above, is also within the scope of the present invention.

[0033] Figure 6 is a flowchart showing the basic configuration of the switching method using a clutch with position detection means of the present invention. As shown in the figure, the switching method using a clutch with position detection means is a method of determining and executing the switching of a target to be switched using a specific clutch with position detection means equipped with the above-described switching determination execution means, and mainly consists of a switching determination process P10 in which the timing of meshing between the gear and the armature that are to be switched is determined by a meshing presence or absence determination criterion based on the position detection result of the target to be switched by a rotation sensor, and a switching execution process P20 in which the switching by the armature is executed based on the determination made in the switching determination process P10.

[0034] In this switching method using a clutch with a position detection means, using the specific clutch with a position detection means described above, first in the switching decision process P10, the timing of the meshing between the gear to be switched and the armature is determined by the meshing presence / absence determination criteria based on the position detection result of the gear to be switched by the rotation sensor, and then in the switching execution process P20, the switching EX of the gear to be switched by the armature is executed based on the determination made in the switching decision process P10.

[0035] The present invention also includes a method for manufacturing a clutch with position detection means. Figure 7 is a flowchart showing the basic configuration of the switching method using a clutch with a position detection means according to the present invention. This is a method for manufacturing a clutch with a position detection means having any of the above-described configurations, and comprises an installation process Q30 in which the position detection means is attached to the switching target by aligning the specific position of the position detection means with the specific position of the switching target, and an initial setting process Q40 after the installation process Q30 in which the position detection means is set to an operational state, and is characterized by a configuration in which the initial setting process Q40 enables the acquisition of the relative position of the switching target with respect to the armature.

[0036] In this clutch manufacturing method with a position detection means, during the mounting process Q30, the specific position of the position detection means and the specific position of the switching target are aligned, and the position detection means is attached to the switching target. Subsequently, during the initial setup process Q40, the position detection means is set to an operational state, and the relative position of the switching target with respect to the armature is acquired. Furthermore, other processes necessary for clutch manufacturing are carried out before, during, or after these processes, and the clutch CL with a position detection means is manufactured.

[0037] This section specifically describes the case where a hollow shaft resolver is used as a position detection means in this manufacturing method. When attaching the hollow shaft resolver to the switching target (fixed tooth), the 0 position of the hollow shaft resolver and the position of the tooth protrusions on the fixed tooth are aligned in advance before attachment (attachment process Q30). Then, the hollow shaft resolver is energized and its angle signal is read (initial setting process Q40). This makes it possible to determine the position of the tooth without having to confirm or estimate the position of the tooth on the fixed tooth.

[0038] In other words, when the clutch armature is engaged with one fixed tooth, and the rotation sensor to be attached to the other fixed tooth side to be engaged is to align its zero position with the tooth position of the other fixed tooth before attaching the angle sensor, the convex teeth of the armature and the convex teeth of the other fixed tooth can be engaged without interference between them.

[0039] This manufacturing method is particularly suitable for clutches that use a hollow shaft resolver as a position detection means, but a magnetic encoder or the like may also be used. [Industrial applicability]

[0040] According to the clutch with position detection means, its manufacturing method, the clutch equipped with the position detection means, and the switching method using the clutch with the position detection means of the present invention, in a high-speed / low-speed switching clutch, the clutch can be switched at the timing when the gear to be switched and the armature are matched, thereby avoiding malfunctions during switching and improving reliability. Therefore, this invention has high industrial applicability in all related fields, including factory automation, the manufacturing and use fields of clutches and products using them. [Explanation of symbols]

[0041] 1, 21, 41... All items subject to replacement. 2, 22, 32, 42... Second target for switching 3, 23, 43... Armature 4, 24, 44... Complete replacement structure 5, 25, 45... Second switching structure 6, 26, 36, 46... Position detection means 8, 28, 38, 48... Input axes 9, 29, 49... Output shafts 10, 210, 310, 410… Clutch with position detection means CL...Clutch with position detection means EX... Switching of the target of the switch P10... Switching decision process P20... Switching process Q30...Installation process Q40…Initial setting process 81... Low-speed side fixed teeth 82... High-speed side fixed teeth 83... Armature 84...Completely replaceable structure 85...Second switching structure 88...motor shaft 89... Output shaft 810...Conventional high / low speed switching clutch

Claims

1. A clutch comprising a first switching target, a second switching target, and an armature located between the two and used for switching, The armature is shaped to fit each corresponding switching target, At least one of the items subject to the first replacement or the item subject to the second replacement, A position detection means is provided for detecting the position of the object to be switched. A clutch with position detection means, characterized by the above.

2. The clutch with position detection means according to claim 1, characterized in that the first replacement target and the second switching target are gears that mesh with the armature.

3. The clutch with position detection means according to claim 2, characterized in that the first gear to be switched is a low-speed gear and the second gear to be switched is a high-speed gear.

4. The clutch with position detection means according to any one of claims 1, 2, or 3, characterized in that the position detection means is a rotation sensor.

5. The clutch with position detection means according to any one of claims 1, 2, or 3, characterized in that the position detection means is a hollow shaft resolver.

6. The clutch with position detection means according to any one of claims 1, 2, or 3, characterized in that the position detection means is a magnetic encoder.

7. The position detection means is a rotation sensor, The aforementioned all-changeable object and the second-changeable object are gears that mesh with the armature, The rotation sensor in question is, It has an angular resolution that satisfies the criteria for determining whether or not the armature and gear mesh, which are calculated based on the dimensions of the armature and the gear. A clutch with position detection means according to any one of claims 1, 2, or 3, characterized in that

8. The clutch with position detection means according to claim 7, characterized in that the meshing determination criterion is a meshing determination range calculated from the gear period width GC, which is the period width of the gear, the gear width GW, which is the width of the armature gear AW.

9. A clutch with a position detection means according to claim 7, characterized in that it includes a switching determination execution means that determines the timing of the meshing between the gear and the armature, which are the target of switching, based on the position detection result of the rotation sensor, and performs switching by the armature, according to the meshing presence or absence determination criterion.

10. A clutch device equipped with a position detection means, characterized by comprising a clutch with a position detection means as described in any one of claims 1, 2, 3, 8, or 9.

11. A method for determining and executing the switching of the object to be switched using a clutch with position detection means as described in claim 9, Based on the position detection result of the switching target by the rotation sensor, A switching determination process that determines the timing of the meshing between the gear and the armature, which are the targets of the switching, based on the meshing presence or absence determination criteria, Based on the judgment made through the switching decision process, The system is characterized by comprising a switching execution process that performs the switching by the armature, A switching method using a clutch with a position detection mechanism.

12. A method for manufacturing a clutch with position detection means according to any one of claims 1, 2, 3, 8, or 9, An installation process in which the position detection means is attached to the switching target by aligning the specific position of the position detection means with the specific position of the switching target, The system includes an initial setup process that sets the position detection means to an operational state after the installation process. This initial setup process makes it possible to obtain the relative position of the switching target with respect to the armature. A method for manufacturing a clutch with a position detection means, characterized by the above.

13. The method for manufacturing a clutch with a position detection means according to claim 12, characterized in that the position detection means is a hollow shaft resolver.

14. The method for manufacturing a clutch with a position detection means according to claim 12, characterized in that the position detection means is a magnetic encoder.

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