GB2370324A

GB2370324A - A method of determining a gear ratio of a transmission

Info

Publication number: GB2370324A
Application number: GB0030914A
Authority: GB
Inventors: Andrew David Milsom
Original assignee: LuK Lamellen und Kupplungsbau GmbH
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 2000-12-19
Filing date: 2000-12-19
Publication date: 2002-06-26
Also published as: GB2370327A; GB0129932D0; GB0030914D0; JP2002188712A; ITMI20012700A1; DE10149526A1

Abstract

A transmission comprises a multi-ratio gearbox 12 having an input shaft 15 and an output shaft 44. The input shaft 15 and output shaft 44 have sensors 42, 43 which produce pulsed output signals, the number of pulses of the output signals being proportional to the number of rotations of the shafts 15, 44. A gear ratio is determined by counting the number of pulses produced by sensor 43 over a period taken for the sensor 42 to produce a predetermined number of pulses (for example 100), that is the gear ration will be a predetermined number of pulses produced by sensor 42 to the number of pulses produce by sensor 43 over the same period. Sensors 42, 43 may comprise an inductive pickup mounted in proximity to a circumference of a toothed wheel fixed to shafts 15, 44. Wheel sensors 62 may also be provided so that an overall ratio of the transmission and differential may be determined.

Description

TRANSMISSION SYSTEMS

The present invention relates to a method of determining the transmission ratio of a transmission system incorporating a multi-ratio gearbox, particularly an automated transmission system.

In automated transmission systems, for example automated manual transmission systems, or automatic or semi-automatic transmission systems including a multi-ratio gearbox of, for example, the type disclosed in W097/05410 or W097/40300 whose content is expressly incorporated in the disclosure content of the present application, a gear engagement mechanism comprises a plurality of shift rails, each shift rail being associated with two gear ratios of the gearbox, via a selector fork and synchromesh unit, so that axial movement of each shift rail in either direction will engage one of the associated gear ratios.

The selector member is moved in a select direction transverse to the shift rails, to be indexed with and engage a selected one of the shift rails and in a shift direction, axially of the shift rails, to move the selected shift rail axially in one direction or the other to engage the selected gear ratio.

In accordance with W097/05410 and W097/40300, the selector member is moved in the first and second directions by means of hydraulic actuators. DE 19734023 whose content is expressly incorporated in the disclosure content of the present application, discloses the use of electric motors to move the selector member in the first and second directions respectively.

In such systems, the means for controlling the actuators must be calibrated, so that the selector member may be moved to positions corresponding to engagement of the gear ratios in the gearbox. This will depend upon the design of the gearbox. As the systems may be used

with difference designs of gearbox, there is a requirement that the type of gearbox may be determined.

According to one aspect of the present invention, a method of determining a transmission ratio of a transmission system incorporating a multi-ratio gearbox comprises: producing a pulsed input signal, the number of pulses of the signal being proportional to the number of rotations of an input shaft to the transmission system; producing a pulsed output signal, the number of pulses of the output signal being proportional to the number of rotations of an output shaft of the transmission system; and counting the number of pulses of one of the input or output signals which occur during the same period as a predetermined number of pulses of the other of the input or output signals.

An accurate transmission ratio determination will then be the ratio of the predetermined number of pulses of the input signal to the number of pulses of the output signal over the same period.

According to a preferred embodiment of the invention, the input signal is derived from rotation of an input shaft of the gearbox, said input shaft being located between the gearbox and a friction clutch, by which the gearbox is connected to an engine. Alternatively, however, the input signal may be derived from rotation of a shaft located on the engine side of the clutch or a component of the engine, the clutch remaining fully engaged during the transmission ratio determination.

The output signal may be derived from a direct output shaft of the gearbox, in which case the transmission ratio determined will be the gear ratio. Alternatively, the output signal may be derived from one or more of

the driven wheels of the vehicle, in which case the transmission ratio determination will be a combination of the gear ratio and differential ratio.

By determining the transmission ratio based on the number of revolutions of the input shaft and output shaft over a given period, in the manner disclosed above, the determination is not affected by changes in speed and may consequently be carried out over a significant period, without requiring steady state conditions, thereby improving the accuracy of the determination.

The present method may be used to detect the type of gearbox fitted to the vehicle, or to check the actual gear selected against other means of indication of the gear selected, for example the position of the gear select and gear shift actuators.

An embodiment of the invention is now described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a semi-automated transmission system; and Figure 2 shows a gear selector mechanism and associated selector gate for the transmission system illustrated in Fig. 1.

Figure 1 of the accompanying drawings shows an engine 10 with a starter and associated starter circuit 1 osa which is coupled through the main drive friction clutch 14 to a multi-speed synchromeshed lay shaft-type gearbox 12, via a gearbox input shaft 15. Fuel is supplied to the engine by a throttle 16 which includes a throttle valve 18, operated by accelerator pedal 19. The invention is equally applicable to electronic or mechanical fuel injection petrol or diesel engine.

The clutch 14 is actuated by a release fork 20 which is operated by a hydraulic slave cylinder 22, under the control of a clutch actuator control means 38.

A gear selector lever 24 operates in a gate 50 having two limbs 51 and 52 joined by a cross track 53 extending between the end of limb 52 and intermediate of the ends of limb 51. The gate 50 defines five positions; "R"at the end of limb 52 ;"N"intermediate of the ends of the cross track 53;"S"at the junction of limb 51 with the cross track 53; and"+"and "-"at the extremities of limb 51. In limb 51 the lever 24 is biased to the central"S"position. The"N"position of the selector lever 24 corresponds to neutral ; "R"corresponds to selection of reverse gear;"S" corresponds to selection of a forward drive mode; momentary movement of the lever to the ~ +"position provides a command to cause the gearbox to shift up one gear ratio; and momentary movement of the gear lever 24 to the"-"position provides a command to cause the gearbox to shift down one gear ratio.

The positions of the lever 24 are sensed by a series of sensors, for example micro switches or optical sensors, positioned around the gate 50.

Signals from the sensors are fed to an electronic control unit 36. An output from the control unit 36 controls a gear engaging mechanism 25, which engages the gear ratios of the gearbox 12, in accordance with movement of the selector lever 24 by the vehicle operator.

In addition to signals from the gear selector lever 24, the control unit 36 receives signals from: sensor 1 9a indicative of the degree of depression of the accelerator pedal 19;

sensor 30 indicative of the degree of opening of the throttle control valve 18 ; sensor 26 indicative of the engine speed ;

sensor 42 indicative of the speed of the clutch driven plate ; sensor 34 indicative of the clutch slave cylinder position ; and sensor 43 indicative of the gearbox output shaft speed.

The control unit 36 utilises the signals from these sensors to control actuation of the clutch 14 during take-up from rest and gear changes, for example as described in patent specifications EP0038113, EP0043660, EP0059035, EP0101220 and W092/13208 whose content is expressly incorporated in the disclosure content of the present application.

In addition to the above mentioned sensors, control unit 36 also receives signals from a vehicle speed sensor 52, ignition switch 54, brake switch 56 associated with the main braking system, for example the footbrake 58 of the vehicle and from ABS wheel sensors 62.

A buzzer 50 is connected to the control unit 36 to warn/indicate to the vehicle operator as certain operating conditions occur. In addition or in place of the buzzer 50 a flashing warning light or other indicating means may be used. A gear indicator 60 is also provided to indicate the gear ratio selected.

As illustrated in Figure 2, the gear engagement mechanism 25 comprises three shift rails 111,112, 113 mounted parallel to one another for movement in an axial direction. Each shift rail 111,112, 113 is associated with two of the gear ratios of the gearbox 12, via a selector fork and synchromesh unit in conventional manner, so that movement of the shift rails 111, 112, 113 in one axial direction will cause engagement of one of the associated gear ratios and axial movement of the shift rail 111, 112, 113 in the opposite axial direction will cause engagement of the other associated gear ratio.

Typically ; first and second gear ratios are associated with shift rail 111, so that axial movement of the shift rail 111 in a first direction will engage first gear or axial movement of shift rail 111 in a second direction will engage second gear; third and fourth gear ratios are associated with shift rail 112, so that axial movement of shift rail 112 in the first direction will engage third gear or axial movement of shift 112 in a second direction will engage fourth gear; and fifth and reverse gear ratios are associated with shift rail 113, so that axial movement of shift rail 113 in the first direction will engage fifth gear while axial movement of shift rail 113 in the second direction will engage reverse gear.

A selector member 110 is mounted for movement in a select direction X transverse to the axes of the shift rails 111, 112, 113 and in a shift direction Y, for movement axially of the shift rails 111, 112 and 113. The selector member 110 may thus be moved in direction X along a neutral plane A-B, so that it may be indexed with and engaged a selected one of the shift rails 111, 112 and 113. The selector member 110 may then be moved in direction Y to move the engaged shift rail 111, 112, 113 axiaiiy in either direction to engage one of the gear ratios associated therewith.

The selector member 110 will typically be controlled by a pair of pneumatic, hydraulic or electrical actuators, for example as disclosed in W097/05410 ; W097/40300 ; or DE 19734023, one to move the selector member 110 in direction X and one to move selector member 110 in direction Y. Sensor means 32 is associated with the selector member 110 or the actuators to provide the position of the selector member 110 with respect to the X and Y directions, which may be used to provide an indication of the gear ratio engaged, which is displayed on indicator 60.

Vehicles may be supplied with a variety of different gearbox types and different differential units. Automated transmission systems of the type described above must be calibrated depending upon the characteristics of

the gearbox/differential unit with which they are used. This may of course be achieved by visually identifying the gearbox type used and looking up the characteristics thereof. The present invention however provides means by which the gearbox type may be identified and distinguished from other gearbox types by measurement of the gear ratios. As the gear ratios of different gearbox types may differ by only a small amount, the method of determination of the gear ratio must be accurate. Furthermore, the present method may be used to check that the gear engaged is that identified by sensor means 32 and if necessary, recalibrate the sensor means 32 to correct the detected position of the selector member 110.

In accordance with the present invention, sensors 42 and 43 comprise an inductive pickup mounted in proximity to the circumference of a toothed wheel, which is mounted for rotation with the gearbox input shaft 25 and gearbox output shaft 44, respectively. Sensors 42 and 43 thereby produce pulsed signals, the number of pulses being proportional to the number of rotations of the shafts 15 and 44 respectively. Other sensor means which will produce pulse signals indicative of the number of revolutions of the shafts may alternatively be used.

The number of pulses of the signals produced by sensors 42 and 43 are counted and the number of pulses of the signal produced by sensor 43 over the period taken for the sensor 42 to produce a predetermined number of pulses (for example 100) is determined, from which the transmission ratio of the currently engaged gear may be calculated. That is the gear ratio will be the predetermined number of pulses produced by sensor 42 to the number of pulses produced by sensor 43 over the same period.

According to an alternative embodiment of the invention, the number of pulses produced by sensor 43 may be compared against the number of

pulses produced in similar manner by sensor 26, the clutch 14 remaining fully engaged during the gear ratio determination.

Furthermore, the pulses produced by sensors 42 or 24 may be compared against pulses produced by wheel sensors 62 which correspond to the number of revolutions of the wheels. The resulting transmission ratio determined in this manner will be the overall ratio of the gear selected and the differential unit. Preferably, when using the wheel sensors 62, both driven wheels should be monitored, so that the counts may be averaged to correct for differences that may occur in the number of rotations of each of the wheels, over the determination period.

Various modifications may be made without departing from the invention.

For example, while as described above the number of pulses of an output signal are counted during the time taken for a predetermined number of pulses of an input signal, alternatively the number of pulses of an input signal may be counted during the time taken for a predetermined number of pulses of an output signal.

The patent claims submitted with the application are proposed formulations without prejudice to the achievement of further patent protection. The applicant reserves the right to submit claims for further combinations of characteristics, previously only disclosed in the description and/or drawings.

References back used in sub-claims refer to the further development of the subject of the main claim by the characteristics of the respective subclaim ; they are not to be understood as a waiver with regard to achieving independent item protection for the combination of characteristics in the related sub-claims.

Since the subject of the sub-claims can form separate and independent inventions with reference to the prior art on the priority date, the applicant reserves the right to make them the subject of independent claims or of division declarations. Furthermore, they may also contain independent inventions which demonstrate a design which is independent of one of the objects of the preceding sub-claims.

The embodiments are not to be considered a restriction of the invention.

Rather, a wide range of amendments and modifications is possible within the scope of the current disclosure, especially those variations, elements and combinations and/or materials which, for example, the expert can learn by combining individual ones together with those in the general description and embodiments in addition to characteristics and/or elements or process stages described in the claims and contained in the drawings with the aim of solving a task thus leading to a new object or new process stages or sequences of process stages via combinable characteristics, even where they concern manufacturing, testing and work processes.

Claims

1. A method of determining the transmission ratio of a transmission system incorporating a multi-ratio gearbox comprising; producing a pulsed input signal, the number of pulses of the input signal being proportional to the number of rotations of an input shaft to the transmission system; producing a pulsed output signal, the number of pulses of the output signal being proportional to the number of rotations of an output shaft of a transmission system; and counting the number of pulses of one of the input or output signals which occur during the same period as a predetermined number of pulses of the other of the input and output signals.

2. A method according to claim 1 in which the input shaft is an input shaft of the gearbox.

3. A method according to claim 1 in which the input shaft is a component of an engine or input shaft of a frictional clutch located between an engine and the gearbox, the clutch remaining engaged during the determination of the transmission ratio.

4. A method according to any one of claims 1 to 3 in which the output shaft is an output shaft of the gearbox.

5. A method according to any one of claims 1 to 3 in which the output shaft is an output shaft from the differential unit.

6. A method according to claim 5 in which the transmission ratio determined is the combined transmission ratio of the gear engaged and the differential unit.

7. A method according to any one of the preceding claims in which the sensors comprise an inductive pickup mounted in proximity to the periphery of a toothed wheel, the tooth wheel being mounted for rotation with the associated shaft.

8. A method substantially as described herein with reference to the accompanying drawings.