WO2011051054A1 - Shifting assembly for detecting a shifting travel in a motor vehicle transmission - Google Patents

Abstract

The invention relates to a shifting assembly (1) for detecting a shifting travel in a motor vehicle transmission comprising a shifting rail (5) extending in an axial direction (4) which can be axially slid or rotated, an eddy current sensor (9) for detecting the axial position of the shifting rail (5) and a measurement element (21) influencing the measurement values of the eddy current sensor (9) which is arranged on or to the shifting rail (5).

Description

 Name of the invention

Switching arrangement for detecting a switching path in a

 Motor vehicle transmission

description

FIELD OF THE INVENTION The invention relates to a shift arrangement for detecting a shift travel in a motor vehicle transmission. Such a switching arrangement is intended to enable the position determination of a switching element, whereby switching operations can be easily and accurately controlled and monitored. Background of the invention

Due to the advent of automated manual transmission and dual-clutch transmission, the detection of a shift sleeve position and thus the shift path has become necessary. In particular, in shift arrangements for shifting gear stages of an automated stepped transmission, it is important that the position of a switching element is accurately detected. In general, various ways can be taken for this purpose.

DE 10 2006 02 87 85 B3 discloses a non-contact method for detecting a switching path in the form of an arrangement with a sensor and a number of position sensors on a switching element designed as a switching rod. The position encoders are formed by two permanent magnets, which are arranged on a common plate and positively cooperate via a recess with a projection formed on the switching rod. Thus, the position sensors are precisely positioned to the shift rod. The arrangement of the position encoders is carried out overall so that the position encoders are the position sensors fixed to the housing in the gear compartment. genüberliegen. By means of the position sensors, the position of the shift rod can be determined.

In an arrangement according to DE 10 2006 02 87 85 B3, however, the use of magnets is essential, which serve with the position sensors for detecting the position of a switching element. However, the use of a magnet poses problems such as temperature-related measurement inaccuracies or metal abrasion in the transmission, which can hinder the bearing and the frictionless movement of a switching element. The magnets also require accurate positioning, so that usually a calibration of the arrangement is required.

DE 10 2007 044 425 A1 discloses a device for detecting the position of a shift fork, wherein the shift fork moves in a high-frequency field and this changes by means of a damping element. The change in the high-frequency field leads to detuning a resonant circuit whose frequency change is detectable. The device requires specially adapted shift forks and requires a separate resonant circuit detector for each shift fork.

Object of the invention

It is therefore an object of the invention to provide a switching arrangement for measuring a switching path, which allows the most accurate possible determination of the gear positions under the proviso of a simple feasibility.

The object of the invention is achieved according to the invention by an arrangement with the feature combination according to claim 1. Accordingly, the shift arrangement for detecting a shift travel in a motor vehicle transmission has an axially displaceable and axially displaceable shift rail, an eddy current sensor for detecting the axial position of the shift rail, and a measurement element influencing the measured values of the eddy current sensor, on or at the shift rail is arranged.

The invention is based on the consideration that in general through the use of non-contact sensors, the life and the reliability of the detection of a switching element can be increased. As a sensor for non-contact detection of the position of the shift rail, an eddy current sensor is used. The eddy current sensor is arranged with respect to the shift rail so that it detects their position in the axial direction. By integrating a measuring element influencing the measured values of the eddy current sensor, it is achieved that all positions of the switching rail can be reliably detected with an eddy current sensor and only one eddy current sensor is required for all switching positions if the measuring element is adequately selected and arranged. Eddy current sensors are characterized in particular by the fact that they do not require magnets for measurement and even under problematic environmental conditions, such as in the presence of strong magnetic fields, at high temperatures and at a relatively high degree of contamination still show an acceptable accuracy. Due to the non-contact detection no mechanical contact between individual transmission components is necessary, so that a wear-free operation can be ensured. The use of magnets on the shift rail can be completely dispensed with. As a result, a more flexible transmission design is possible because a separation of the metal particle-containing oil from the sensor is no longer required lent.

By using an eddy current sensor, a relatively high measurement accuracy can still be achieved even under difficult conditions. in this connection In particular, this accuracy can be exploited to safely and easily detect the switching position in a motor vehicle transmission. A switching arrangement with an eddy current sensor for detecting a switching path thus offers a wear-free and very accurate measuring method for determining the position of a switching element which meets the high requirements.

The principle of eddy current measurement is based on the detection of the retroactivity of eddy currents. In this case, eddy currents are induced by a changing magnetic field in an electrical conductor, which in turn cause the build-up of an opposing magnetic field. During a switching operation, for example, the switching element moves between two positions, each corresponding to a switching position. In order to be able to determine a switching position, the eddy-current sensor thus has to detect the two positions of the switching element. For this purpose, in the simplest case, the generation of a constant magnetic field, with respect to which the switching element changes its position, is sufficient. Usually, however, an alternating magnetic field is generated by the eddy current sensor, which is weakened when a conductive measuring element or target is in the vicinity. In the measuring element eddy currents are generated by the alternating field, which weaken the magnetic field. This attenuation is measurable and dependent on the distance between the eddy current sensor and the target. For example, the alternating magnetic field can be generated by means of an electromagnetic resonant circuit. This is measurably deprived of energy by the weakening of the magnetic field.

The term shift rail includes both rotatable shift shafts as additionally or exclusively axially movable shift rails. The shift rail is usually made of a metallic material. In this respect, it can be used directly and without further aids as a target for the eddy current sensor. To carry out switching operations, such a switching element is movably supported within a transmission and in particular in the switching unit. Usually, an axial end of the shift rail is mounted in a bearing unit. For storage, for example, a ne stored in a storage unit. For storage, for example, a rolling bearing or a plain bearing is provided. The bearing unit with the mounted switching element is inserted into a transmission housing. The cross-sectional contour of the shift rail can be round. Alternatively, it is designed as a shift rail in the narrower sense with a deviating from a circle, rather flat cross-section. Usually, a shift rail is made of a metal sheet. For manufacturing, known and easy-to-use manufacturing processes, such as a punching offer. Due to the design of the switching element as a shift rail, in particular a shape advantageous for the eddy current sensor for the position detection can be easily made.

For measuring the distance by means of an eddy current sensor, as stated, an electrically conductive target is required. Such a target or measuring element is manufactured separately in one embodiment and attached to the shift rail. The attachment can be done for example by gluing or screwing. By such a separate measuring element can be taken in particular on the requirements of the eddy current sensor consideration. The measuring element is specifically adaptable to the eddy current sensor used. A separate measuring element does not have to deal with the specific requirements that the switching rail has to fulfill as such. Advantageously, however, the shift rail is already made of an electrically conductive material, in particular of steel, and can therefore be used as a measuring element itself. The design of the shift rail as a measuring element simplifies the switching arrangement considerably. The assembly effort is not undesirable by attaching and positioning a separate measuring element difficult. Also, the space requirement can be kept low. In a further advantageous embodiment of the invention, the shift rail is formed with an inclined towards the eddy current sensor ramp contour. The ramp contour is formed in particular at the location of the switching element on which the eddy current sensor is in operative connection with the switching element. Due to the inclination of the ramp contour relative to the eddy current sensor, the distance between the shift rail and the eddy current sensor changes with an axial displacement. By this radial change in distance, the axial position of the switching element can be determined with high accuracy. About the defined ramp, a relationship between the measured via the eddy current sensor radial distance and the axial position of the shift rail can be determined. In particular, a ram with a constant pitch is provided for this purpose. Alternatively, existing installation geometries or switch positions are taken into account via a specific ramp contour with different inclinations. A shift rail with a rectangular cross-section can be made directly and with relatively little manufacturing effort with a correspondingly inclined ramp contour.

Alternatively, the measuring element is manufactured separately and at least rotatably connected to the shift rail. A distortion of the shift rail by attaching the measuring element does not occur due to the relatively large mass of the shift rail. In a further development, the measuring element is arranged on a separate component such as a switching sleeve, which in turn is pressed or welded on the shift rail. The switching sleeve advantageously takes several functions as a multi-functional sleeve. Thus, it can have switching fingers, switching guides and locking contours. Such a shift sleeve can be inexpensively made of sheet metal or plastic, and the shift rail remains free of reworking.

In principle, the eddy-current sensor can be arranged along the entire switching element. Preferably, however, the eddy current sensor is positioned on a switching dome formed by the shift rail and its mounting. By arranging the eddy current sensor in close proximity to the The measurement error in the detection of the axial position of the switching element is kept low or for lane guidance.

For the simplest possible positioning, the eddy-current sensor is advantageously fastened to the switching unit. Thus, the position between the eddy current sensor and the shift rail during assembly of both components is already clearly defined. In particular, the positioning of the two components relative to one another is already achieved before installation of the switching unit in a transmission. Ideally, in this case, the switching unit and the measuring sensors are integrated in a common housing, so that the module can be incorporated as a module in the transmission. The customer is thereby considerably easier to assemble.

In one embodiment of the invention, the measuring element is formed as a sheet metal part having a constant cross section. By forming a contour is introduced into the sheet, which has a defined distance to the eddy current sensor in different switching positions. The change of the resonant circuit is thus effected by the geometric proximity of the measuring element.

In a further embodiment, the measuring element has a locally different thickness. For example, material can be removed by machining so that, depending on the orientation relative to the sensor, the measuring element changes the high-frequency field during switching, in addition to or solely on the basis of its varying material thickness.

In a further embodiment, the measuring element is constructed of different materials. Thus, sections of plastic can alternate with those of aluminum or steel, for example, to detect relatively discrete changes. Also envisaged is the use of metal-particle-containing plastic. In a variant of the invention, the measuring element additionally serves as a latching element of a shift lock. By means of a biased against a locking element Schaltarretierung the individual grades are set, and prevents jumping out of the aisle. An integration through multiple use of the locking contour saves components and installation space.

It is also provided that the eddy current sensor is arranged on the shift dome or on the transmission housing so that it can detect all gear stages and in particular the neutral position. In the case of a central selector shaft, it interacts with a measuring element arranged on or on the selector shaft. If several switching rails are provided, each is equipped with its own measuring element, which can influence the recorded measured values. With such an arrangement, it is sufficient to use a relatively expensive eddy current sensor. In particular, when it comes only to the detection of the neutral position, it is possible to detect this in a simple manner in that the high-frequency field is detuned by any measuring element, so that such an arrangement is simple and inexpensive to implement.

Short description of the drawing

Embodiments of the invention are explained in more detail below with reference to drawings. Showing:

1 shows a cross section through a schematic circuit arrangement with a bearing unit, a shift rail and an eddy current sensor,

2 shows a perspective view of a switching arrangement according to the invention with a switching element having a measuring sleeve and an eddy current sensor,

3 shows a cross section of the arrangement according to FIG. 2, 4 shows a first measuring element with an eddy current sensor

5 shows a second measuring element FIG. 6 shows a third measuring element.

Detailed description of the drawings

1 shows a cross section of a switching arrangement 1 with a bearing unit 3. In the bearing unit 3, a shift rail 5 extending in an axial direction 4 is mounted. In the region of the bearing unit 3, the shift rail 5 is slidably held with its one axial end in the axial direction 4. As part of a switching operation, the shift rail 5 can be moved within the storage unit 3 over a distance of a few millimeters to centimeters in the axial direction 4 with respect to the neutral position. The switching arrangement 1 is designed to detect an axial switching path of this shift rail 5.

For detecting the axial position of the shift rail 5, an eddy current sensor 9 is attached to the bearing unit 3. The eddy current sensor 9 is arranged with respect to the shift rail 5 so that it can detect a positional offset of the shift rail 5 in the axial direction 4. By the connection of the eddy current sensor 9 to the bearing unit 3, the eddy current sensor 9 and the shift rail 5 are fixedly positioned relative to each other after insertion of the shift rail 5. A complex alignment for calibration of the sensor 9 is not necessary. Due to the axial bearing of the shift rail 5 in the bearing unit 3, there are no movements of the shift rail 5 in the radial direction at this point. The achievable measurement accuracy is insofar not affected by such, for example, in a switching operation occurring deflections.

The shift rail 5 is formed with a rectangular cross section and consists of a conductive steel. It is itself as a measuring element or Target for the eddy current sensor 9 is formed. For an accurate detection of the axial position of the shift rail 5 along the axial direction 4 is designed with a defined ramp contour 1 1 a constant pitch. For this purpose, the ramp is inclined in the axial direction 4 with respect to the eddy current sensor 9. In other words, the ramp contour 1 1 is detectable by the eddy current sensor 9. With an axial displacement of the shift rail 5 changes due to the inclination of the ramp contour 1 1 of the radial distance 13 between the two components. By this measurable change in distance, a high accuracy of the axial displacement of the shift rail 5 is achieved. About the inclination of the ramp contour 1 1 is a conversion of the measured by means of the eddy current sensor 1 1 radial distance 13 to the shift rail 5 in its axial position possible.

The roller bearing 15 serves for the axial mounting of the shift rail 5. The cage-guided balls run inside on a mounted on the shift rail 5 inner plate 18 and the outside in a circular cylinder sleeve 19, which in a Bore of the storage unit 3 is inserted. Such a roller bearing 15 allows good efficiency due to a low bearing friction and thus increases the shifting comfort, since it ensures a very smooth longitudinal guide of the shift rail 5. The rolling bearing 15 offers a low and virtually load-independent friction.

The eddy current sensor 9 is provided with a plug 20 for power supply and the Meßabgriff. In order to protect the plug 20 from contamination, for example by oil, it is pulled out of the storage unit 3 to the front. After installation of the entire module in a transmission housing 27, the plug 20 is arranged outside the storage. In this way, the eddy current sensor 9 can also be easily contacted from the outside.

In the present case, the eddy-current sensor 9 generates an alternating magnetic field via an electromagnetic resonant circuit. This field is determined by the Switched rail 5 weakened. In the shift rail 5 eddy currents are generated, which withdraw energy from the resonant circuit. This change in energy is measurable and dependent on the distance between the eddy current sensor 9 and the shift rail 5. In the present case, the radial distance 13 between the eddy current sensor 9 and the ramp contour 1 1 is detected and converted into an axial position of the shift rail 5.

Figures 2 and 3 show a switching sleeve 2, which is firmly or rotatably connected to a shift rail, not shown. For example, it can be blocked, pressed or welded. The shift sleeve 2 is designed as a multi-functional onshülse and carries next to the measuring element 21 further switching elements such as a shift finger 6, a gate guide 7, which is arranged in the vicinity of the measuring element 21 and a locking contour 8 for locking with a Schaltarretierung, not shown. Due to their larger lateral surface compared to the switching rail, the components 6, 7, 8, 21 can be arranged in a simple manner, without the shift rail being weakened.

Various measuring elements 21 are shown in FIGS. 4, 5 and 6. The measuring element 21 according to FIG. 4 is formed from sheet aluminum as a stamped stamped part with a ramp contour 11. Along the selection direction, the ramp contour 1 1 has a direction of rotation extending in the direction of selection and aligned with the eddy current sensor 9 elevation 10, which marks the neutral path. The elevation 10 merges relatively sharp-edged into radially lower regions 12, 14 in order to ensure reliable detection as soon as a switching operation takes place in the circumferential direction. In Figure 5, the elevation 10 is rounded, and the first region 12 and the second region 14 have a different radial height, so that the gear position is detectable. A measuring element 21 with such rounded contours is suitable, in particular if it is made of steel, at the same time as a latching contour for a shift lock. FIG. 6 shows a measuring element 21 made of metallized plastic with a central bead 16, which also identifies the neutral track. List of reference numbers Switching arrangement

switching sleeve

storage unit

axial direction

shift rail

shift finger

alleys lead

catch contour

Eddy current sensor

survey

ramp contour

first area

distance

second area

roller bearing

Central Beading

rolling elements

inner panel

cylinder sleeve

plug

measuring element

gearbox

Claims

claims 1 . Switching arrangement (1) for detecting a switching path in a motor vehicle transmission, comprising a shift rail (5), which is axially displaceable or rotatable in an axial direction (4), an eddy current sensor (9) for detecting the axial position of the shift rail (FIG. 5) and a measuring element (21) which influences the measured values of the eddy-current sensor (9) and which is arranged on or on the selector rail (5). Second switching arrangement (1) according to claim 1, wherein the measuring element (21) is a separate from the shift rail (5) formed component. 3. switching arrangement (1) according to claim 1, wherein the measuring element (21) is designed as a stamped embossed part. 4. Switching arrangement (1) according to claim 1, wherein the measuring element (21) has a ramp contour (1 1). 5. Switching arrangement (1) according to claim 4, wherein the measuring element (21) is designed as a deformed metal sheet of constant thickness. 6. switching arrangement (1) according to claim 4, wherein the ramp contour (1 1) is formed by different material thicknesses. 7. Switching arrangement (1) according to claim 1, wherein the measuring element (21) comprises different materials. 8. Switching arrangement (1) according to claim 1, wherein the measuring element (21) on a on the shift rail (5) rotatably mounted shift sleeve () is fixed. Switching arrangement (1) according to claim 1, wherein the eddy current sensor (9) is integrated in a locking element (12) which is biased against the measuring element (21). Switching arrangement (1) according to claim 1, wherein the eddy current sensor (9) and the measuring element (21) are arranged to each other so that the detection of all gears is possible.