GB2277784A

GB2277784A - A gear position detector

Info

Publication number: GB2277784A
Application number: GB9408711A
Authority: GB
Inventors: Lutz Leimbach; Ingo Franz; Thomas Strasser
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1993-05-06
Filing date: 1994-05-03
Publication date: 1994-11-09
Anticipated expiration: 2014-05-03
Also published as: GB2277784B; FR2704922A1; DE4314952A1; DE4314952C2; FR2704922B1; GB9408711D0

Description

2277784 1 MEANS FOR ASCERTAINING THE GEAR SELECTED IN A GEARBOX This

invention relates to means for ascertaining the gear selected in a gearbox of the kind in which the gearbox has a housing in which works a selector shaft rotatable about its axis and axially movable to select the gears, each gear position being defined by a plane and a direction in the plane, the means including digital switch elements.

Such means are known for example from German Gebrauchsmuster G91 09 855.6. The device described in this publication, which ascertains the gear position without contact, by making use of magnetic fields, has a finger which is connected to a selector shaft of the gearbox and on the end of which is mounted a permanent magnet acting on a sensor. The sensor, which extends into the gearbox from outside in the immediate neighbourhood of the permanent magnet, detects the position of a magnetic- fie ldsensitive reed switch associated with each selected position of the selector shaft. Because the reed switches do not respond consistently, the sensor must be adjusted by individual displacement of the individual magnetic screening plates associated with the individual reed switches, in a time-consuming setting process.

DE-A-38 36 145 shows a selected-position ascertaining means which continuously picks up the position of the central selector shaft by means of a linear potentiometer. Figure 3 shows a f inger which is connected to the selector shaft and projects radially from it and of which the tip forms the slider of a potentiometer track.

2 It is an aim of the present invention to provide means for ascertaining the gear selected in a gearbox in which the characteristics of the switch elements used correspond to the tolerances in the individual selected positions.

According to the present invention means for ascertaining the gear selected in a gearbox of the kind set forth includes at least one analogue switch element the arrangement of the digital and analogue switch elements being such that the digital switch elements are used to determine the plane and the analogue switch elements to determine the direction in the plane of the selector shaft, to ascertain the gear selected.

The arrangement of digital and analogue switching elements in this way means that digital elements can be used to recognise the plane, and will meet requirements even for coarsely set tolerances. It is advantageous to use analogue elements to determine the direction, as they are capable not only of recognising a gear position which has actually been -engaged but also one that has been selected or contemplated. They can also be easily and accurately adjusted, and so can be used in conjunction with means for evaluating gear changes having a learning capability. Such a combination of switch elements is of particular advantage with automatic clutchactuating arrangements. In that case, the recognition of the plane has no direct effect on the actuation of the clutch, but the recognition of a direction engaged is significant to the start of a clutch-engaging sequence, so that this must be determined much more accurately by the switch elements. In this connection the digital switch elements can comprise relatively low-cost components, and they can 3 be adjusted at a pre-assembly stage. More expensive analogue switch elements are then only employed for determining the direction and here - especially for automatic clutch actuation - a first adjustment and perhaps subsequent re-adjustments can be made in combination with evaluating circuits in a kind of learning operation.

Advantageously, the selector shaft has one end projecting through a wall of the gearbox housing into a sensor module, in which the analogue and digital switch elements are arranged. By the use of a sensor module mounted outside the gearbox housing the result is both simple assembly and improved accessibility for any possible servicing, as well as a more favourable environment for the switch elements.

Preferably, a single analogue switch element is provided. This reduces the primary production costs for the gear-recognition system.

Conveniently the actuating element of the analogue switch element is arranged substantially on the axis of the selector shaft and co-operates with the end of that shaf t. Accordingly, depending on the type of analogue element used, it is possible to detect either the axial movement or the angular movement of the selector shaft by use of the analogue switch element, and the other movement by the digital elements.

To detect angular movement of the selector shaft the analogue switch element preferably comprises -a rotary angle sensor and the digital switch elements are arranged serially along the axis of the selector shaft and at the same radial distance from it, and are actuated by a transmitter on the selector shaft. Such 4 an arrangement is of advantage for a gearbox in which the selection of the plane takes place by axial displacement of the selector shaft and the selection of the direction by rotation of the selector shaft. The rotary angle sensor is preferably actuated through a rotationally fixed but axially displaceable connection, such as for example a key-and-slot connection to the end of the selector shaft.

In another embodiment, the analogue switch element comprises a displacement sensor and the digital switch elements are arranged radially around the axis of the selector shaft in series, and are actuated by a transmitter arranged on the selector shaft. In this arrangement the selection of the plane takes place by rotation of the selector shaft and selection of the direction by axial displacement. The end of the selector shaft which is towards the sensor module acts directly on the actuating element of the displacement sensor, which is displaceable in the direction of the axis of the selector shaft.

Two embodiment of the invention are shown by way of example in the accompanying drawings, in which:- Figure 1 is a partial section through a gearbox housing with a sensor module built onto it and showing the end of the selector shaft; Figure 2 is a corresponding view showing a modified construction; and Figure is an illustration of the principle of an H gear-change layout.

Figure 1 shows means for ascertaining the gear selected in a gearbox. A selector shaft 1 is located in a gearbox housing 2. It projects through an aperture in the wall of the gearbox housing 2 and has its end 19 enclosed on the outside of the gearbox by a sensor module 4. During gear- changing movement, the selector shaf t 1 is rotated in the direction of the arrow A about its axis 3 and is displaced axially in accordance with the arrow B. The sensor module 4 has digital and analogue switch elements for determining the position of the selector shaft. Three digital switch elements 7, 8r 9 are axially spaced in the module 4, and the end 19 of the selector shaft 1 has an annular cam 6 which co-operates with the digital switch elements 7 to 9. The digital switch elements 7 to 9 can be formed as micro switches or as reed contacts or equally well as Hall- effect devices. A single analogue switch element 13 in the form of a rotary angle sensor is mounted on the sensor module 4, and the end 19 of the selector shaft 1 has a slotted shaft 15 which extends through the rotary angle sensor. The slotted shaft 15 is keyed for rotation with the rotary angle sensor, but is axially displaceable in relation to it. Signals from the digital and the analogue switch elements are brought together and appropriately processed in a microprocessor.

The digital switch elements 7, 8, 9 serve for ascertaining the individual planes of the gearbox in accordance with the axial position of the selector shaft 1. The analogue switch 13 in the form of a rotary angle sensor ascertains the angular position of the selector shaft 1 which results on engagement of the individual gears in accordance with the arrow A. At this point attention is drawn to Figure 3, which illustrates the principle of an H gear-change layout.

6 In an H layout in accordance with Figure 3 three forward ratios and a reverse ratio can be obtained, requiring two planes 17 and 18. These planes are detected by the digital switch elements 7 to 9, and where there are three planes (for example for five-speed gearboxes), three switch elements are provided as well. The determination of the individual planes 17 and 18 is relatively uncritical and accordingly it is sufficient to actuate the digital switching elements 7 to 9 by means of the annular cam 6 on the selector shaft 1. To ascertain the gear selected, that is. to recognise whether a ratio is engaged, and if so, which one, the rotary angle sensor 13 comes into action, delivering an appropriate signal through the action of a keyed shaft 15, on rotation of the selector shaft 1 in accordance with the arrow A.

As the sensor module is mounted on the gearbox housing 2 it is possible to pre-adjust the switch elements but it is very advantageous to build into the microprocessor a stored program device which, by means of a learning program, takes account of the actual construction of the module and gearbox and can adjust the switch elements accordingly.

Figure 2 shows a modification of the embodiment of Figure 1, and corresponding reference numerals have been applied to corresponding parts. In Figure 2, the selector shaft 1 is rotated about its axis 3 in accordance with the arrow C to select the plane, whilst the individual ratios are engaged by displacing the selector shaft 1 axially in accordance with the arrow D. The sensor module 4 arranged on the gearbox housing 2 has its digital elements 10 to 12 arranged circumferentially within the housing of the sensor module 4, at equal radial distances from the axis 3 of 7 the selector shaft. For actuating the digital switch elements 10 to 12 the selector shaft 1 has a cam 5 which actuates the individual elements 10 to 12 on rotation of the shaft 1 in accordance with the arrow C. By the angular movement and using these digital switch elements 10 to 12 the individual planes of a gearbox can be recognised. To recognise the individual ratios the end 19 of the selector shaft 1 co-operates with a sliding pin 16 of an analogue switch element 14 in the form of a displacement sensor. The displacement sensor 14 is mounted on the sensor module 4 in such a way that its sliding pin 16 is arranged in alignment with the axis 3 of the selector shaft so that the axial position of the selector shaft 1 is detected by the pin 16. The analogue displacement sensor 4, after appropriate adjustment by a learning process in the microprocessor, can determine whether a ratio is engaged or not.

8

Claims

1. Means for ascertaining the gear selected in a gearbox of the kind set forth, including at least one analogue switch element, the arrangement of the digital and analogue switch elements being such that the digital switch elements are used for determining the plane and the analogue switch elements to determine the direction in the plane of the selector shaft, to ascertain the gear selected. -

2. Means as claimed in claim 1, in which the selector shaft has one end projecting through a wall of the gearbox housing into a sensor module in which the analogue and digital switch elements are arranged.

3. Means as claimed in claim 1 or claim 2, in which a single analogue switch element is provided.

4. Means as claimed in claim 3, in which the actuating element of the analogue switch element is arranged substantially on the axis of the selector shaft and co-operates with the end of the selector shaf t.

5. Means as claimed in any preceding claim, in which the analogue switch element comprises a rotary angle sensor and the digital switch elements are arranged serially along the axis of the selector shaft and at the same radial distance from it and are actuated by a transmitter on the selector shaft.

6. Means as claimed in claim 5, in which the rotary angle sensor is actuated through a rotationally fixed but axially displaceable connection.

9

7. Means as claimed in claim 6, in which the connection is a key-and-slot connection to the end of the selector shaft.

8. Means as claimed in any of claims I to 4, in which the analogue switch element comprises a displacement sensor and the digital switch elements are arranged radially around the axis of the selector shaft in series and are actuated by a transmitter arranged on the selector shaft.

9. Means as claimed in claim 8 as dependent on claims 2 to 4, in which the end of the selector shaft which is towards the sensor module acts directly on the actuating element of the displacement sensor which is displaceable in the direction of the axis of the selector shaft.

10. Means for ascertaining the gear selected in a gearbox of the kind. set forth substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

11. Means for ascertaining the gear selected in a gearbox of the kind set forth substantially as described herein with reference to and as illustrated in Figure 2 of the accompanying drawings.