DE102013205901B4 - Switching device of a vehicle gear change transmission - Google Patents

Abstract

Switching device (1) with a switching element (3) of a vehicle gear change transmission, which is movable to a gear housing fixed housing (2) and a signal transmitter (4, 5) for determining the position of the switching element (3), wherein the housing (2) has a bearing receptacle for the Switching element (3) and a sensor (6) for the signal transmitter (4, 5), wherein the signal generator by two axially spaced, on the switching element (3) fixedly arranged magnets (4, 5) is formed and wherein between the Magnets (4, 5) a ferromagnetic element (13) is arranged, whose radial extent is at least as large as that of the magnets (4, 5), characterized in that the switching element (3) by means of metallic balls as rolling elements (16) in Housing (2) is roller-mounted and that the housing (2) has a sleeve in the region which is axially between the magnets (4, 5), which formed of a ferromagnetic material or with a ferro magnetic material is coated.

Description

Field of the invention

The invention relates to a switching device with a movable switching element of a Fahrzeuggangräderwechselgetriebes, which is movable to a gear housing fixed housing and having a signal transmitter for determining the position of the switching element, wherein the housing forms a bearing receptacle for the switching element and having a sensor for at least one of the signal generator, the signal generator two axially spaced, fixedly arranged on the switching element magnets is formed and wherein between the magnets, a ferromagnetic element is arranged, whose radial extent is at least as large as that of the magnets.

Background of the invention

A switching device of the generic type is used in particular in manual transmissions but also in automated manual transmissions and in automatic transmissions of motor vehicles. Increasingly, it is necessary in modern gearbox construction to be able to determine the exact position of shifting elements, in particular of shifting shafts.

According to a prior art, the position detection of a switching element based on the principle of detecting a locally changed magnetic field by utilizing the Hall effect. So revealed the EP 1 350 991 B1 a sensor arrangement for determining a shift drum position, wherein a probe scans a contoured peripheral surface of a sensor disk firmly connected to a shift shaft. By non-contact measurement of the position of the probe, the switching position is then determined by means of a Hall element.

With the previously known solutions, only one essentially switching Hall sensor is used, which is designed to detect discrete switching positions. In the case of the use of Hall switches, one obtains only binary state information, no exact position of a switching element; Intermediate items can not be recorded.

To solve this problem, there exist approaches for continuous displacement measurements that are based on measuring the flux density of magnets or the angular course of the magnetic field. Generic switching devices go out DE 10 2006 011 207 A1 and US 2009/0 001 971 A1 out. Other switching devices are off, DE 10 2008 052 416 A1 . DE 10 2008 063 598 A1 and DE 197 48 115 A1 known.

However, the signals from magnets used for the continuous path measurement disadvantageously have high temperature dependencies in the case of the flux density measurement or are characterized by a high nonlinearity in the case of the angle measurement. Therefore, a great deal of effort in terms of compensation, linearization or learning each switching device is required. Furthermore, high demands are placed on the components, whose series production may only be very small.

A further disadvantage is that, especially in the application as integrated sensors in a rolling bearing, said sensor systems based on measurements of magnetic fields are not well suited, since the ferromagnetic properties of the rolling elements cause a too large and unexchangeable disturbance of the signal curve.

Object of the invention

The present invention has for its object to provide a switching device with a switching element with a magnetic system for the axial position detection of the switching element available whose position can be detected continuously safe under the conditions prevailing in the transmission conditions. This is to ensure that the exact axial position detection is possible without offset correction or only with little corrective measures. Furthermore, a switching device is to be provided with such a switching element and a rolling bearing having ferromagnetic rolling elements, which enables reliable detection of the mounted switching element.

Summary of the invention

The object is achieved by a switching device with the features of claim 1. On the switching element, two magnets are arranged, which are axially spaced from each other. According to the invention, a ferromagnetic material is arranged on the imaginary connecting line through both magnets. The ferromagnetic material arranged at this point causes the magnetic field lines, which without the material would be more angled to the surface of the switching element, to be "pulled" into the vertical. As a result of this parallelization of the field lines in the pole field, magnetic field changes can be detected more easily at a predetermined, radial distance from the switching element. Furthermore, the effect that the magnetic field direction is dependent on the absolute strength of the magnets axially next to the poles is alleviated. The series scattering of the magnets therefore influences the measured magnetic field angle significantly less, so that the angle errors of the poles are reduced. This has several advantages: On the one hand, cheaper magnets can be installed, since they may have a larger series spread; on the other hand, an individual sensor calibration can be omitted, which significantly reduces installation costs. Finally, if one sensor fails, only the sensor itself needs to be replaced without requiring a new calibration procedure.

The two magnets are preferably designed as permanent magnets. They may be formed, for example, as a rectangular or cylindrically shaped bar magnet.

The two magnets are preferably arranged in opposite directions with respect to the magnetic field generated by them.

The two magnetic elements are arranged so that the magnetic field lines emerging from the center of the magnetic elements are perpendicular to the axial direction of movement of the switching element. They are preferably arranged at the same distance away from the switching axis of the switching element.

Preferably, the magnets are held solely on the switching element due to their magnetism and not additionally, for example, material or form-fitting secured. The switching element consists for example of a steel alloy.

In a development of the invention, the magnets are arranged in recesses of the switching element. The recesses are formed as through holes or blind holes in the lateral surface of the switching element and preferably have contours that are complementary to those of the magnets. Falling out or unintentional stripping of the magnets during assembly can be prevented, so that can be dispensed with additional, costly security measures. Nevertheless, the magnets can still be additionally secured in the recess, for example glued or sprayed with plastic.

A switching element with recesses which correspond at least to the radial height of the magnets has the advantage that the ferromagnetic element can be formed by the switching element itself. The production cost is thus reduced. The switching element is formed, for example, as a switching shaft with a cylindrical outer surface having two spaced holes as blind holes for the magnets. The magnets are circular cylindrical with flat, radially directed end faces and magnetically arranged in the holes so that the polar axis is also directed radially. The outer contour of the switching arrangement thus formed by the switching shaft and the magnets is therefore flattened in the region of the blind hole, resulting in both sides of the magnets in the axial direction walls that border the magnets. When viewed in longitudinal section, the outer contour is thus formed by the enveloping circle of the lateral surface of the switching arrangement extending parallel to the axis of rotation, which is offset radially inward only in the area of the blind holes.

In a next embodiment of the invention, the switching element has a recess in the form of a slot. The magnets are spaced from each other in the same slot, and between the magnets, the ferromagnetic element is disposed between the magnets at least in a partial region on an imaginary connecting straight line passing through the magnets. Such a solution is also suitable for switching elements that are not magnetizable, such as switching rods made of carbon or plastic. The ferromagnetic element is preferably made separately from the switching element in this case.

The switching element is formed in particular by an axially displaceable and rotatable switching shaft for selecting and switching gear positions. The switching device may be part of a manual transmission, an automated transmission or an automatic transmission of a motor vehicle. The magnetic field of the signal generator is detected by a preferably gearbox fixed sensor. The sensor and the magnets are preferably moved relative to each other at a constant distance to form an air gap. The sensor is preferably connected to an evaluation device, which is designed for further processing of the measured signal, for example the magnetic field direction, in an axial position. The sensor may generally operate in the manner of a compass needle indicating the direction of the magnetic field.

By the proposed concept, a continuous measurement of the magnetic field is made possible with sufficient accuracy for a continuous position determination of the switching element. The measured signal is already linear or a good linearisierbares signal that allows accurate axial position determination of the switching element relative to the housing. For this purpose, the magnetic field generated by the two magnets is detected with respect to the direction and / or strength of the sensor and from this determines the axial position. The two magnets are arranged one behind the other in the measuring direction, whereby the magnetic field direction is substantially proportional to the axial position and insensitive to disturbances.

This is made possible by the use of two magnets which are magnetized opposite to each other and arranged side by side in the measuring direction and preferably have the same thickness. With a suitable distance between the magnets, a minimum linearity error of the measured variable advantageously results for a specific air gap over the measuring path. Furthermore, the ideal air gap in this configuration is smaller than the typical air gaps with simple magnets, which additionally has a positive effect on the integrability of the solution.

A further advantage is that by pushing out of the magnetic field lines in the vertical adjacent interference, z. B. by relative movements of ferromagnetic rolling elements, significantly lower affect the sensor-directed magnetic field and thus the signal quality.

For an optimal characteristic curve can be expertly adjusted the distances of the magnets from each other and the size of the air gap.

The proposed solution is particularly suitable for the continuous position determination of a switching element in a linear bearing of a transmission because of the only small necessary air gap and robustness against interference. Furthermore, only a small space is needed, which is equally advantageous.

It is also advantageous that an integration of the proposed solution in existing transmission systems is possible without changing their environment construction; the outer dimensions of the switching device and thus the mechanical interfaces remain unchanged.

An inventive switching element can be stored directly in a transmission housing. Preferably, it is mounted in a housing, in which the sensor for detecting the field lines of the magnets is integrated. The housing and the switching element with the magnets form a switching device. The switching device may, in particular, have a plurality of rows of metallic rolling elements arranged one behind the other, which roll on the switching element immediately adjacent to the magnets, without the measuring accuracy being significantly impaired.

Preferably, the housing is a metal or plastic housing, which is provided with a recess for one or more sensors. In a variant, the housing has a bearing shell, in which the sensor is embedded. The bearing shell can be designed as an MID component, that is to say as an injection-molded component with a printed circuit board, which allows easy adaptation to different environmental constructions. The bearing shell or the housing can simultaneously fulfill an adapter function and have an outer contour, which is dissimilar to the outer contour of the, for example, rectangular switching element, which allows an arrangement in an external bore or a differently designed blind hole.

If the housing is not itself metallic, it may have a metallic sleeve, which forms the outer raceway for the rolling elements. In the region of the sensor, a window can be provided in the sleeve. A ferromagnetic outer raceway can also have a favorable influence on the magnetic field lines and further improve the measuring accuracy.

Brief description of the figures

In the figures, an embodiment of the invention is shown. Show it:

1 a schematic representation of a switching device of a motor vehicle gearbox with a switching shaft which can move in an axial direction and the axial position to be detected,

2 schematically the sensor system for determining the axial position of the switching shaft,

3 the function of the measured magnetic field direction (α) over the axial position (x) and

4 a switching device with a switching element in a perspective view.

Detailed description of the figures

In 1 is a part of a switching device 1 of the gear change transmission of a motor vehicle outlines whose basic structure is known. By means not shown actuators, a switching element 3 in the form of a switching shaft in a housing 2 be moved axially in the direction of an axis. With the switching shaft 3 can a shift fork 9 moves and hereby a switching operation can be performed.

The determination of the axial position x of the switching shaft 3 is done with a sensor made of magnets 4 . 5 as a signal generator pair and a sensor 6 is formed.

The functioning of the sensor is in 2 shown in more detail. It includes a first magnet 4 and a second magnet 5 , which are stationary at respective axial positions x ₁ and x ₂ on the switching element 3 are arranged and thus have a defined distance from each other. As can be seen, the magnets formed as permanent magnets are 4 . 5 arranged in opposite directions, ie the north and south poles N, S are oriented in opposite directions. As a result of the two magnetic elements 4 . 5 generates a magnetic field, as determined by the in 2 sketched magnetic flux lines is indicated. This results in the manner outlined, because the orientation of the magnetic elements 4 . 5 such that the magnetic axis from the north to the south pole is perpendicular to the axial direction of movement x.

The sensor also includes a sensor 6 , which is at a radial distance s from the switching element, not shown here 3 and through an air gap 7 is spaced. The sensor 6 is on the case 2 fixedly arranged.

Because of the two magnets 4 . 5 generated magnetic field results over the axial displacement direction x at each location a local direction T of the magnetic field from the sensor 6 can be detected; accordingly, the sensor 6 detect an angle α at which the magnetic field is at a position x. This applies in any case over a measuring range M, over which a high degree of linearity between the angle α and the axial position x of the switching element 3 consists.

This is in 3 to see, in the present and the gauge 6 measured angle α is plotted against the axial position x. For the in 2 present position x _{0 of} the sensor 6 Here is an angle of α ₀ given. Each axial position x in the range of the maximum permissible displacement of a few cm is uniquely associated with a certain angle α, so that the detection of an absolute value is sufficient without having to refer to a reference position.

The determination of the axial position x from the measured angle α takes place in an evaluation device 8th , in the 2 outlined. The measured angle α is in the evaluation 8th transmitted, in which the axial position x determined and output, for example, to the vehicle electronics.

4 shows a switching device 1 with a housing 2 as MID component and a switching element 3 in the form of a shift rod. The shift rod has a circular lateral surface 15 on, the end through the housing 2 is stored with a blind hole recording. To secure switching positions, the switching element 3 locking recesses 12 on, in the thighs one in the housing 2 axially secured form spring 14 can lock. The lateral surface 15 forms the inner raceway for the rolling elements 16 of which each form a plurality of rolling element rows arranged axially one behind the other. On the outer circumference of the switching element 3 a plurality of such rows of rolling elements are arranged.

Between two rows of rolling elements are two magnets 4 . 5 axially fixed in succession, whose polarity is directed radially and oppositely. The flat and round magnets 4 . 5 are so in the holes designed as holes 11 . 10 of the switching element 3 arranged the secant of the holes with the surface of the magnets 4 . 5 matches, causing the switching element 3 centered on the magnet 3 . 4 survives. The supernatant forms the ferromagnetic element 13 that the magnetic field lines in the vertical to the switching element 3 draws. The magnets 4 . 5 are thereby in the switching element 3 sunk and are not on the outer circle of the circular surface 15 radially in front.

LIST OF REFERENCE NUMBERS

1

switching device

2

casing

3

switching element

4

first magnet

5

second magnet

6

sensor

7

air gap

8th

evaluation

9

shift fork

10

recess

11

recess

12

latching depression

13

ferromagnetic element

14

shaped spring

15

lateral surface

16

rolling elements

x

axial position

x ₁

first axial position

x ₂

second axial position

s

distance

A

Axis of the switching element

T

local direction of the magnetic field local angle of the magnetic field

S

South Pole

N

North Pole

M

measuring range

Claims (8)

Switching device ( 1 ) with a switching element ( 3 ) of a vehicle gear change transmission, which to a gearbox fixed housing ( 2 ) is movable and a signal generator ( 4 . 5 ) for determining the position of the switching element ( 3 ), wherein the housing ( 2 ) a bearing receptacle for the switching element ( 3 ) and a sensor ( 6 ) for the signal transmitter ( 4 . 5 ), wherein the signal transmitter by two axially spaced, on the switching element ( 3 ) fixed magnets ( 4 . 5 ) is formed and whereby between the magnets ( 4 . 5 ) a ferromagnetic element ( 13 ) is arranged, whose radial extent is at least as large as that of the magnets ( 4 . 5 ), characterized in that the switching element ( 3 ) by means of metallic balls as rolling elements ( 16 ) in the housing ( 2 ) is roller-mounted and that the housing ( 2 ) a sleeve in the region which is axially between the magnets ( 4 . 5 ), which is formed of a ferromagnetic material or coated with a ferromagnetic material. Switching device according to Claim 1, characterized in that the ferromagnetic element ( 13 ) as one of the switching element ( 3 ) is formed separately manufactured component. Switching device according to Claim 1, characterized in that the ferromagnetic element ( 13 ) in one piece with the switching element ( 3 ) is trained. Switching device according to one of the preceding claims, characterized in that the magnets ( 4 . 5 ) in one or more recesses ( 11 . 10 ) of the switching element ( 3 ) are arranged. Switching device according to claim 3, characterized in that the magnets ( 4 . 5 ) as a circular cylinder and the recesses ( 11 . 10 ) are formed as blind hole bores. Switching device according to one of the preceding claims, characterized in that the magnets ( 4 . 5 ) solely due to its magnetism on the switching element ( 3 ) are held. Switching device according to one of the preceding claims, characterized in that the switching element ( 3 ) is formed as a shift rod, as a shift shaft or as a shift rail. Switching device according to claim 1, characterized in that the housing ( 2 ) has a radial recess in which the sensor ( 6 ) is arranged accessible radially from the outside.

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