GB2353835A

GB2353835A - Two mode automatic transmission allowing racing start

Info

Publication number: GB2353835A
Application number: GB0019188A
Authority: GB
Inventors: Robin John Warren
Original assignee: LuK Lamellen und Kupplungsbau GmbH
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 1999-09-04
Filing date: 2000-08-07
Publication date: 2001-03-07
Anticipated expiration: 2020-08-07
Also published as: DE10040167A1; FR2798173B1; GB2353835B; GB0019188D0; FR2798173A1

Abstract

An automated transmission disengages clutch 14 for gear engagement upon movement of lever 24 from neutral N to drive S and in a first, standard start mode, controls clutch re-engagement according to engine speed. The system also includes a vehicle brake 58 actuation sensor 56 and a switch for initiating a second, racing start, mode following actuation of the brake 58 and the switch, to permit increased engine speed without clutch re-engagement, which is only effected upon release of the switch. The arrangement shown is an indexing semi-automatic transmission with lever 24 acting as the switch. The second mode is engaged by applying the brake and holding the lever in the gear down position (-) for five seconds after which a warning buzzer 50 sounds and the brake may be released; release of the lever initiates the start.

Description

2353835 AUTOMATED TRANSMISSION SYSTEMS The present invention relates to

automated transmission systems, said transmission systems having a coupling as a main drive clutch, clutch actuation means of controlling of state of engagement of the clutch, a multi-ratio gearbox, a gear-engaging mechanism for engaging an operative ratio of the gearbox and a driver operable drive mode selector allowing the driver to select neutral or a drive mode.

In German Patent Application DE1 9911332 an automated transmission system is proposed in which take-up from rest may be initiated at increased engine speed, by increasing the engine speed while the drive mode selector is in neutral. Movement of the drive mode selector to drive mode will then cause the transmission system to engage a take-up gear and engage the clutch in controlled manner. While this system may provide a quicker get-away than initiating take-up at idle speed and then opening the throttle, there is still a delay after initiation of take-up, in order to engage the take-up gear.

The purpose of the present invention is to provide a transmission system as described above, which reduces or eliminates the aforesaid disadvantages.

The present invention provides an automated transmission system with the facility for making sporty or racing starts.

According to one aspect of the present invention an automated transmission system comprises a main drive clutch, clutch actuation means for controlling the state of engagement of the clutch, a multi- ratio gearbox, a gear-engaging mechanism for engaging an operative ratio of the gearbox, a driver operable drive mode selector such as a gear-change or selector lever allowing the driver to select neutral or a drive mode, switch means for initiating take-up at elevated speed and an electronic control means to control the clutch actuation means, the control means being adapted to disengage the clutch for engagement of a take-up gear upon movement of the drive mode selector from neutral to a drive mode, and in a first mode controlling re-engagement of the clutch in accordance with engine speed; the control means also including means for sensing actuation of a brake of the vehicle; and the control means in a second mode being adapted, upon actuation of the brake and the switch means, to permit elevation of the engine speed without re-engagement of the clutch, the control means in the second mode being adapted to cause the clutch actuation means to re-engage the clutch, upon release of the switch means.

In accordance with the present invention, take-up at elevated speed may be initiated by actuation of the vehicle brake and switch means, after movement of the drive mode selector from neutral to a drive mode to engage a take-up gear. In this second mode, the engine speed may be increased with the take-up gear engaged, without re-engagement of the clutch in accordance with'the normal take-up procedure. The engagement of the clutch may then be initiated by release of the switch means.

Preferably with semi or fully automated transmission systems the take-up gear will be selected automatically upon movement of the drive mode selector. With fully automatic transmissions the gear can be selected automatically by a control unit, so that the driver need not be involved in the gear selection at least in one operating mode of the transmission.

However with manual transmission systems with automated clutch, the take-up gear is selected manually by movement of the drive mode selector.

In accordance with an alternative embodiment of the invention, for turbocharged engines, when the brake and switch means are actuated, the control means may permit partial pre-engagement of the clutch, to load the engine and increase turbo pressure.

In accordance with a preferred embodiment of the invention, the brake and switch means must be actuated for a predetermined period, typically 5 seconds, before take-up at elevated speed is initiated. An audible and/or visual warning may be given at the end of that period, to indicate to the driver that the take-up at elevated speed mode is initiated. After 10 initiation, the brake may be released but the switch means is not released until re-engagement of the clutch is required. Preferably for semi-automated transmission systems the switch means used to initiate take-up at elevated speed and control clutch reengagement in that mode, is the gear selection switch. Other switch 15 means, for example a brake locking switch of the type found in rally cross cars or a dedicated switch means, may be used. Upon release of the switch means, re- engagement of the clutch is controlled in order to provide maximum acceleration, preferably with a smooth take-up of drive, avoiding excess wear and overheating of the 20 clutch, and avoiding stalling of the engine. The clutch may furthermore be controlled to give positive torque traction control in order to avoid wheel slip. The invention is now described, by way of example only, with reference to the accompanying drawings, in which:25 Figure 1 shows a schematic view of a semi-automated transmission system in accordance with the present invention; Figure 2 shows a flow diagram illustrating the steps involved in controlling transmission in accordance with the present invention; and Figure 3 is a typical plot of engine speed and clutch plate driven speed against time, for a take-up at elevated engine speed with the transmission system illustrated in Figure 1.

Figure 1 of the accompanying drawings shows an engine 10 with a starter and associated starter circuit 1 Oa which is coupled through the main drive friction clutch 14 and a gearbox input shaft 15 to a multi-speed transmission 12, for example a triple-shaft transmission with several synchromeshed transmission gears. 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, such as a slide way, 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 5 1. 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. The gear engaging mechanism 25 may, for example, comprise hydraulic rams and solenoid control valves to move selector members to engage and disengage the various gear ratios, for example as disclosed in patent specification W097/0541 0 by the present Applicant, whose content is expressly incorporated in the disclosure content of the present application.

In addition to signals from the gear selector lever 24, the control unit 36 receives signals from:

sensor 19a 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 32 indicative of the gear ratio selected.

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, EP01 01220 and W092/13208, whose contents are expressly incorporated on the disclosure contents of the present -6 application.

In addition to the above mentioned sensors, control unit 36 also receives signals from an anti-lock braking sensor system 52, ignition switch 54 and brake switch 56 associated with the main braking system, for example the footbrake 58 of the vehicle.

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.

With the system described above, when the vehicle is at rest, starting of the engine 10 by actuation of the ignition switch 54, will key-on the transmission system and the control unit 36 will cause the clutch actuator means 38,22,20 to disengage the clutch 14. Movement of the gear lever 24 from the neutral "N" position to the drive position "S" or reverse position "R" will then cause the control unit 36 to actuate the gear engaging mechanism 25 to engage, respectively, the lowest forward gear ratio (first gear) or reverse gear. Upon depression of the accelerator pedal 19 to drive the vehicle away, the control unit 36 will then cause the clutch actuator means 38,22,20 to re-engage the clutch 14, to take-up the drive. Re-engagement of the clutch 14 in this manner will be controlled by control unit 36, in the manner disclosed, for example, in EP00381113; EP0043660; EP0696341 or EP0735957 whose content is expressly incorporated in the disclosure content of the present application, in order to ensure a smooth take-up of drive.

Take-up at elevated engine speed may also achieved, by depressing the accelerator prior to movement of the gear lever 24 from the neutral "N" position to drive position "S" or reverse position '-'R". Re-engagement of the clutch 14 may then be controlled by control unit 36, in the manner disclosed in EP0043660; EP0696341 or DE 19911332.7 whose content is expressly incorporated in the disclosure content of the present application.

Take-up at elevated engine speed in this manner is primarily used where the transmission is under load, for example when the vehicle is starting on a hill or is towing, but it will also provide a quick get-away, if required.

Nevertheless, normal take-up procedures of the type described above, cannot be compared with sporty or racing starts achievable with a manual transmission system.

With the transmission system of the present invention, a sporty or racing start may be initiated by applying the footbrake 58 and holding the gear lever 24 in the shift-down position "-" for a predetermined period, typically 5 seconds, after moving the gear lever 24 from the neutral "N" position to the drive mode "S"' position.

After the pre-determined period has expired, the control unit 36 energises the buzzer 50, to pro'vide an audible warning, confirming that the sporty or racing start mode has been initiated. Typically the audible warning will have a duration of one second. After initiation of the sporty or racing start mode, the vehicle accelerator may be depressed in order to increase engine speed, without re-engaging the clutch 14. The vehicle may then be started at elevated engine speed, by releasing the gear lever 24. The brake 58 may be released at any time after the sporty or racing start mode has been initiated.

In accordance with the present invention, the clutch 14 will be disengaged and first gear engaged, when the gear lever 24 is moved from the neutral W' position to the drive mode "S" position. The clutch 14 will however remain disengaged, until the gear lever 24 is released from the shift-down "-" position. A sporty or racing start similar to that achievable with a manual transmission, may consequently be achieved.

Upon release of the gear lever 24 from the shift-down "-" position, control means 36 will control the clutch actuator means 38,22,20 to reengage the clutch in a predefined profile, in order to provide optimum acceleration of the vehicle smoothly from rest, while avoiding excess wear and overheating of the clutch 14 and stalling of the vehicle. In order to 10 achieve this, the clutch 14 may initially be re-engaged fairly rapidly, in order to pull down the engine speed to a predetermined value, thereby reducing the speed differential between the driving and driven plates of the clutch 14 and reducing wear and heating thereof. This will also prevent the engine from racing away and will also make more torque 15 available for accelerating the vehicle. Re-engagement of the clutch 14 may subsequently be controlled in order to maintain optimum acceleration, while maintaining the engine speed above a predetermined minimum value in order to avoid stalling of the engine. Furthermore, the clutch re-engagement may be controlled by control 20 means 36, to provide positive torque traction control, to avoid wheel slip. For this purpose wheel slip may be detected by the anti-lock braking sensor system 52, when for example, the speed of a driven wheel exceeds that of a non- driven wheel by more than a predetermined value, typically 50 rpm. Positive torque traction control in this manner may 25 however necessitate higher speed differentials between the plates of the clutch 14, resulting in increased wear and heating. Figure 3 shows a typical plot of engine speed Ve and clutch driven plate speed Vdp, against time, demonstrating the initial drop in engine speed Ve following take-off request by release of gear lever 24 at time to and the engine speed Ve and driven plate speed Vdp then coming together.

As illustrated in Figure 2, the control unit 36 will monitor the position of the brake 58 and the gear lever 24, to determine whether a sporty or racing start has been initiated or not. Upon application of the accelerator 19, the control unit 36 will then instigate a normal take-up procedure if the sporty or racing start has not been initiated; or will initiate a sporty or racing start mode procedure if said mode has been initiated.

In accordance with an alternative embodiment of the invention, where the engine 10 is turbo-charged, upon actuation of the brake 58 and movement of the gear lever 24 to the shift-down position "-", to initiate sporty or racing start mode, the control unit 36 will cause the clutch actuator means 38,22,20 to partially pre-engage the clutch 14 to load the engine 10, so that increase in engine speed will increase the turbo pressure. With this mode of operation, the brake 58 must be kept on until it is wished to move away.

Partial re-engagement of the clutch 14 in this manner, may be controlled by control unit 36, to provide a predetermined torque level. Alternatively, pre-engagement of the clutch 14 may be controlled by the control unit 36, to provide a predetermined turbo pressure, using a pressure sensor and closed-loop control circuit.

Various modifications may be made without departing from the invention, for example while in the above embodiment hydraulic means are used for actuation of the clutch actuator means and gear engaging mechanism; hydraulic, pneumatic or electrical actuators, for example electric motors or solenoids, may be used, for example as disclosed in DE1 9504847; W097/10456 or DE1 9734023 whose content is expressly incorporated in the disclosure content of the present application.

The claims submitted with the application are formulation proposals without prejudice to the attainment of more complete patent protection.

The Applicant reserves the right to claim additional combinations of features only disclosed so far in the description and/or the drawings.

Back-references in the subordinate claims relate to further developments of the object of the principal claim by virtue of the features specified in the subordinate claim in each case; they are not to be understood as waivers of the right to self-sufficient, objective protection for the feature combinations of the subordinate claims to which they refer. Since, compared with the state of the art on the priority date, the subordinate claims can constitute individual and independent inventions, the Applicant reserves the right to make use of them as the object of independent claims or distinguishing clarifications. They may also constitute self sufficient inventions having a design independent of the objects of the preceding subordinate claims.

The example embodiments are not to be understood as limitations of the invention. Rather, within the scope of the present disclosure numerous variants and modifications are possible, in particular such variants, elements and combinations and/or materials which, for example by combination or variation of features, elements or processes described individually in combination with the general description, example embodiments and drawings and the claims, would be accepted by those familiar with the field as a solution of the objectives set and, by combination of such characteristics, would lead to a new object or to new process steps or process step sequences, even so far as they relate to manufacturing, testing and operating processes.

Claims

1. An automated transmission system comprising a coupling as a main drive clutch, clutch actuation means for controlling the state of engagement of the clutch, a multi-ratio gearbox, a gear-engaging mechanism for engaging an operative ratio of the gearbox, a driver operable drive mode selector allowing the driver to select neutral or a drive mode, switch means for initiating take-up at elevated speed and an electronic control means to control the clutch actuation means, the control means being adapted to disengage the clutch for engagement of a take-up gear upon movement of the drive mode selector from neutral to a drive mode, and in a first mode controlling re-engagement of the clutch in accordance with engine speed; the control means also including means for sensing actuation of a brake of the vehicle; and the control means in a second mode being adapted, upon actuation of the brake and the switch means, to permit elevation of the engine speed without re-engagement of the clutch, the control means in the second mode being adapted to cause the clutch actuation means to re-engage the clutch, upon release of the switch means.

2. An automated transmission system according to claim 1 in which the brake and switch means must be applied for a predetermined period, before the second mode is initiated.

3. An automated transmission system according to claim 2 in which an audible and/or visual warning is given at the end of the predetermined period.

4. An automated transmission system according to any one of claims 1 to 3 in which the switch means comprises a gear selector of a semi automated transmission system, a brake-locking switch or a dedicated - 12switch.

5. An automated transmission system according to any one of the preceding claims in which upon release of the switch means, the clutch is reengaged following a predetermined profile.

6. An automated transmission system according to claim 5 in which upon release of the switch means, the clutch is initially re-engaged rapidly in order to pull down the engine speed to a predetermined value.

7. An automated transmission system according to claim 5 or 6 in which, upon release of the switch means, the clutch is re-engaged to 10 maintain the engine speed above a predetermined minimum value.

8. An automated transmission system according to any one of claims 5 to 7 in which upon release of the switch means, the clutch is reengaged to avoid wheel slip.

9. An automated transmission system according to any one of the 15 preceding claims in which, upon actuation of the brake and switch means, the clutch is partially pre-engaged to load the engine.

10. An automated transmission system substantially as described herein with reference to, and as shown in Figures 1 to 3 of the accompanying drawings.