GB2347764A

GB2347764A - Limiting motor speed when gearbox is in neutral

Info

Publication number: GB2347764A
Application number: GB0015256A
Authority: GB
Inventors: Jochen Stinus
Original assignee: LuK Getriebe Systeme GmbH
Current assignee: LuK Getriebe Systeme GmbH
Priority date: 1996-06-15
Filing date: 1997-06-10
Publication date: 2000-09-13
Anticipated expiration: 2017-06-10
Also published as: GB2347764B; GB0015256D0

Abstract

In a motor vehicle with a drive motor 2, a gearbox 4, and an automatically operable torque transfer system (clutch) 3, a gear position sensor 14 detects the gear ratio engaged in the gearbox, and a motor control unit 30 controls the torque of the drive motor so that, when neutral is detected as the gearbox state, the maximum allowed speed of the engine is reduced. The reduction may follow disengagement or engagement of the torque transfer system.

Description

MOTOR VEHICLE The invention relates to a motor vehicle with a drive motor, a gearbox and a manual or automatic torque transfer system, with an operating unit which can be controlled by a control unit to operate the torque transfer system. An engine control unit controls the engine torque of the drive motor. A transmitter operable on the driver side, such as an accelerator pedal, supplies power on the driver side and provides a transmitter value.

Motor vehicles of this kind can be equipped with an automatic or manually operable gearbox. With such gearboxes the gear position can be selected by means of a gear selector element or the gear setting can be carried out automatically.

If for example a non-driving state is selected in the gearbox then with the torque transfer system opened in this state and with an operation by the driver of the accelerator pedal the increase in the engine speed or engine revs is too strong, and uncomfortable engine noises occur. Furthermore such roaring of the engine leads to undesired noise strain. Also damage to the engine may occur.

If with an automated transmission a gear change is carried out with a break in the traction force it is disadvantageous if during the gear change the engine runs too fast because the driver then may operate the accelerator pedal. This can lead to a loss of comfort and to damage to the motor and/or gearbox.

Furthermore when starting off when a non-starting-off gear is engaged in the gearbox the torque transfer system can undergo an at least temporary excessive strain which is as a rule not desired on the part of the driver.

The object of the invention is to provide a motor vehicle of the kind described above which can be operated comfortably and safely. Furthermore it is an object of the invention to provide a motor vehicle with a gearbox and with an automated torque transfer system which at least substantially reduces or overcomes the disadvantages of the prior art and which can be manufactured costeffectively.

The object is further to carry out a shift process with an automated transmission where the accelerator pedal is operated on the driver's side and nevertheless the engine speed does not run unintentionally high.

According to the invention there is provided a motor vehicle with a drive motor, a gearbox, a manually or automatically operable torque transfer system, a gear recognition sensor for detecting the gear ratio engaged in the gearbox, and a motor control unit for controlling the torque of the drive motor, characterised in that on detection of neutral as the engaged gearbox state, the maximum controllable value of the engine speed is reduced.

The speed reduction can follow either disengagement or engagement of the torque transfer system.

If the torque transfer system is automatically operable, a control unit can be provided for controlling a controllable actuation unit for actuation of the torque transfer system.

The invention will now be explained with reference to the accompanying drawings in which: Figure 1 is a diagrammatic illustration of a vehicle; Figure 2 is a block circuit diagram; and Figure 3 is a block circuit diagram.

Figure 1 shows a vehicle 1 in a diagrammatic illustration with a drive motor 2, a torque transfer system 3 and a gearbox 4. On the output side of the gearbox 4 is a drive shaft 5 and differential 6 as well as the driven axles 7a and 7b wherein the wheels 8a and 8b are driven by means of the driven axles 7a and 7b. The vehicle can also be provided with a four wheel drive. This is however not shown in Figure 1.

The torque transfer system 3, such as for example friction clutch, such as dry friction clutch or wet-running friction clutch, magnetic powder clutch or torque converter with converter bridging clutch is shown in Figure 1 as a torque transfer system 4 mounted in the drive train between the drive motor 2 and the gearbox 4 wherein the torque transfer system 3 can also be mounted on the output side after the gearbox 4, such as can be expedient for example in a continuously variable transmission.

The torque transfer system 3 consists in the illustration of Figure 1 of a clutch disc with friction linings 3b, pressure plate 3c as well as a clutch cover 3d and a plate spring 3e. These parts of the torque transfer system can be mounted on a flywheel 3a wherein these can also be assembled with the flywheel 3a as a premountable unit. The flywheel can also be a so-called twin-mass flywheel which provides at least a torsion damper between the primary and secondary mass. The plate spring 3e is biased by means of the disengagement bearing 3f for engaging or disengaging the clutch whereby through the biasing of the plate spring tongues by the disengagement bearing 3f the clutch can be set or adjusted in to a state which is for example the fully engaged or fully disengaged state or a state between these boundary states. The torque transferrable by the torque transfer system 3 can be set and fixed anywhere in the range between zero and the maximum value.

The disengagement bearing is operated in the embodiment of Figure 1 by a disengagement lever 9 wherein the disengagement lever is operated through a hydraulic path with slave cylinder 10, hydraulic line 11 and actor 12.

The actor 12 contains a setting device 12a which can contain in the event of using a hydraulic path a master cylinder and drive unit for operating the master cylinder.

Furthermore the actor 12 contains an electronic unit 12b such as control unit which processes signals from for example sensor devices, sensors or other electronics units and which produces control signals to control the drive unit of the actor for engaging or disengaging the torque transfer system.

The gearbox 4 is a gearbox where it is possible to differentiate between different gear translations such as gears, by means of an operating element 13. In order to select one gear translation from a number thereof the operating element 13 is brought into the position provided for same or is operated in a manner provided for same.

This operation can be carried out manually in this case.

Furthermore an operation of a gearbox can also take place automatically wherein at least one actor carries out the operation of the transmission automatically. The actor can carry out the shifting and/or selecting of the gears in a controlled manner. An actor of this kind can carry out a transmission operation or a shift process electromechanically or by means of pressurised medium.

The device for disengaging the torque transfer system can as shown above be carried out by means of a pressurised medium system wherein the pressurised medium system can be a hydraulic system, a pneumatic system or an other fluid-operated system. The disengagement member can in these cases also be a central disengagement member operated by pressurised medium. Furthermore the operation can also be carried out through mechanical means, such as for example through a linkage.

A sensor device 14 can be attached or mounted on the operating element 13 whereby an operation of the operating element is detected by this sensor unit 14. The detection of an operation can take place by measuring an acting force or by measuring a change in position or change in speed or acceleration. Furthermore when exceeding a boundary or threshold value in the event of a movement or operation of the operating element a detection of an operation can be carried out. The sensor 14 acts as a gear position sensor which detects the translation engaged in the gearbox or a position engaged in the gearbox.

The sensor or sensor device 14 can be a path or speed or acceleration or force dependent sensor which detects or can detect a movement of the operating element or of an element connected therewith or a force on the operating element or on an element connected therewith.

Furthermore a sensor 15 can be mounted on the gearbox 4 to detect the position of the engaged gear for example by sensing the position of shift elements inside the gearbox.

A sensor of this kind is a gear recognition sensor.

The sensors, such as throttle valve sensor 16, such as wheel speed or speed sensor 17 (vehicle speed sensor), engine speed sensor 18 and further sensors can be provided in or on the vehicle and can be connected to the control unit through signal lines. A door sensor which detects whether a door is opened can likewise be mounted on the vehicle. A sensor can also be provided for detecting the throttle valve angle. The control unit can also calculate from the data of the sensors gradients which are used to evaluate the shift intent. These gradients can be calculated for example by numerical processes. The control unit 12 detects the driving state from these sensor data and other data as well as from system input values and generates a control signal for operating the torque transfer system 3 if a shift intent is evaluated as present.

The vehicle 1 further has an accelerator pedal 20, such as load lever, as well as an operating element of a brake 21, such as operating brake, as well as an operating element 22 for a brake, such as parking brake. At least one sensor 23 is mounted on the load lever 20 and determines both the deflection a and also an operation which is present or not present. An idling switch for example can be considered as a sensor for determining whether the pedal or load lever is operated or not wherein the idling switch is switched on for example when the pedal is not operated and is switched off when the pedal is operated. A reverse switching, such as coding of the idling switch is also possible. The sensor 23 is provided as a transmitter sensor for the accelerator pedal, such as transmitter of the operation on the driver side. The engine control 102 of Figure 2 controls the engine speed and/or engine torque from these accelerator pedal operating values. The control unit of the clutch control and/or transmission control calculates or determines an engine speed and/or engine torque which is to be controlled from the accelerator pedal operation and from the vehicle and transmission and/or clutch data, such as revs, speeds, gear stages etc.

A brake switch 24 can be mounted on the operating element of the operating brake 21, such as brake pedal, to detect whether the brake is operated. A brake switch of this kind can likewise be mounted on the operating element 22 for the parking brake wherein the sensor 25 detects whether the parking brake is operated.

The sensor device 23 of the load lever 20 can furthermore be in signal connection with the engine electronics 30 so that through operation of the accelerator pedal the engine speed and the engine torque is controlled accordingly by the engine electronics 30.

From the signals, such as measuring data or system input values entering the control unit 12 it is possible to determine the engine torque applied. The applied engine torque is the actual engine torque minus/plus the torques which are taken up or discharged by secondary assemblies.

As secondary assembly can be for example the climate control or centrifugal energy accumulator. Furthermore drag torques can be taken into account. The engine torque can however also be determined by the engine control unit 30 and transferred to the control unit through a signal lead.

Furthermore it can be determined whether an operation of the control element 13 exists and whether a brake 21,22 is operated and whether the accelerator pedal, such as load lever, is operated. The control unit 12 detects a shift intent through an operation of the control element 13 from the incoming signals of the sensors 14 and/or 15.

Whether the shift intent is evaluated or accepted as a wish to shift, and a control signal is produced to open the clutch, depends on the system parameters.

The motor vehicle can be fitted with a manually operated gearbox and/or with an automatic shift transmission.

An automatic shift transmission can have a separate control device which controls the shift processes of the gears. This control device can be in signal connection with the control unit wherein sensors can likewise be in signal connection with this control device.

As an advantageous development an integrated control device or an integrated control unit can contain both the engine control, gearbox control and/or control unit for controlling the torque transfer system. An integrated control unit of this kind is in signal connection with sensors and further electronics units and controls and/or regulates the operation of the gearbox, clutch and control of the engine.

Through an integration of this kind of the electronic controls of for example the engine, gearbox and clutch it is possible to provide an advantageous functional and cost-effective unit. For example all parameters of the systems engine, gearbox and clutch can be matched with each other in the sense of a for example consumptionfavourable and/or sporty and/or emissions-favourable operating state.

Apart from the clutch torque as a parameter to be considered it is also possible to correct the engine torque of the engine control, for example by the torques of secondary assemblies, such as for example climate control. In this case, when the secondary assembly is switched on or off it is possible to achieve an increase or reduction in the engine torque.

The gearbox has a gear selector switch or lever by means of which it is possible to set the transmission engaged in the gearbox or a neutral gear or a parking position.

Furthermore it is possible to select a driving program by means of a further element. An element of this kind is marked by 40 in Figure 1. By means of the drive program selector element or device it is possible to differentiate for example between a sporty (s), economy (o), comfort (k) drive program or a winter program (w).

Figure 2 shows a block diagram 100 which represents a function sequence. In block 101 the driver of the vehicle operates a load lever such as accelerator pedal. This pedal is allocated at least one sensor so that it detects a signal representing at least a pedal value. A signal of this kind can be for example the pedal value itself or a throttle valve angle or a corresponding signal.

In block 102 the pedal value is detected and conveyed to the engine control such as engine control electronics.

Similarly this value is conveyed to the clutch control and/or transmission control 104,105. The clutch control is in at least signal connection with the transmission control wherein these two control units can also be formed as integrated control unit. It can likewise be advantageous if the engine electronics are likewise provided with one and/or other control unit as an integrated unit. This is shown by the broken frame 110.

The clutch and/or transmission control 103,104 detects an engine torque and/or engine speed in dependence on the gear selector switch or signal of the gear selector switch sensor respectively. Furthermore the engine control determines a value for an engine torque and/or for an engine speed. These values are processed in block 106 to determine the engine torque.

If for example a non-driving gear is present, such as for example a neutral position N or a neutral gear or a parking position P, then the engine torque can be controlled with a load lever operation so that the engine speed nKtis for example restricted or not restricted. A restriction of this kind can be for example at maximum value nmt X. A maximum speed as boundary value can be provided for example so that the engine is protected from over-revving. Furthermore a restriction can be provided so that the engine is restricted or fixed to a point of maximum engine torque in which a quick start can take place when a driving or starting gear is engaged.

The restriction of the engine speed through a control or regulation of the engine speed or engine torque can be produced in a non-driving gear P, N since the control unit of the torque transfer system is preferably kept open at least temporarily at such an operating point of the torque transfer system. A restriction of the engine speed can be used for improved comfort and for engine protection.

Such a restriction can be provided by nmot # nmot-max As boundary value nmOt-x a speed can be used in the range from 1000 rpm to 6000 rpm, preferably from 2000 rpm to 4000 rpm. Furthermore it is possible to restrict the engine speed to the idling speed with nmOt = nierlauf.

Restricting the engine speed to the idling speed in the gear stages P or N leads for example to a reduction in the fuel consumption of the vehicle.

The engine is controlled in block 107 by means of the engine torque detected in block 106. Through the reaction of the engine 107 to the control, the engine reaction or vehicle reaction 108 is notified back to the driver 101 who can then adapt or change his operation of for example the accelerator pedal.

The control unit of the torque transfer system such as clutch or the engine electronics or a further control unit such as for example a gear control electronics compares the values for the engine torque Mmot determined by the engine electronics with the values Mmoup of the engine torque determined by for example the control unit of the torque transfer system, and forms for example a minimum value as ideal value which is controlled. This can take place for example by means of the function Mmot-soll = MIN(Mmot-kup, Mmot) wherein MIN (x, y) forms the minimum of the values x, y. A vehicle reaction is produced through the engine ideal torque which is being or can be set, and the driver of the vehicle then adjusts the pedal value as he may wish.

The control unit of the torque transfer system can make an allowance regarding the boundary value of the engine speed and/or engine torque and this engine electronics uses this value as an upper boundary value and the engine speed and/or engine torque cannot rise above this boundary value. The selection of the boundary values can depend on the selected drive program.

A control of the engine torque and/or engine speed through the control unit of the torque transfer system can preferably be implemented in a vehicle with E-gas system.

Figure 3 is a block diagram. The signal 201 of the accelerator pedal transmitter is sent to the inputs 202 and 203 of the engine control unit 204 and the control unit 205 of the automated clutch. These calculate from the characteristic lines 204a, 205a, the ideal values 204b, 205b of the engine torque and/or engine speed. These are sent to the input of a comparator 206 and compared with each other. The lower signal or lower value is controlled so that the engine 207 adopts same. In another embodiment also the larger signal of the two values can be controlled. Also the comparator can contain a function generator connected in on the output side to modify the output value once more.

This device for controlling an engine speed and/or an engine torque uses as an engine control device with a control unit. The control unit has a gear recognition sensor which detects, amongst the gears engaged in the gearbox, at least a neutral area engaged in the gearbox.

With a disengaged clutch and/or with an engaged clutch the engine control lowers the controllable maximum value of the engine speed when a non-driving gear such as neutral is engaged in the gearbox. The control unit can be connected to a clutch engagement state detector, such as clutch path sensor, and can reduce the maximum value of the engine speed for example only when the clutch is disengaged. The clutch can thereby be automated or operable by activating a pedal. With the above described for example when neutral is engaged in the gearbox the engine speed is regulated down with a speed which is reduced compared with operation (revs) with a gear engaged wherein the reduction can lie in the area of some hundreds rpm. Thus for example with an engaged gear the down regulating speed at which the engine speed is not raised further by the control unit can be at 6000 rpm and with an engaged neutral area at 5800 rpm. This has the advantage that the centrifugal forces which act on the plate spring tongues of the disengaged clutch are reduced.

It is thereby possible to reduce a negative effect through a clutch which is kept disengaged or stuck as a result of the centrifugal force and the clutch engages again as a result of spring bias of the plate spring when the disengagement bearing releases the clutch for engagement. The above device thus avoids the clutch sticking at least in the disengaged state when neutral area is engaged. The lowering of the maximum engine speed in the neutral area can be carried out so far until the clutch no longer remains stuck. This can happen up to a reduction of the engine speed substantially to the idling speed. Both the new state and the wear state of the clutch can thereby be taken into account since with a wear state of the clutch the plate spring tongues as generally known can have a steeper or more inclined installation position. The reduction of the maximum engine speed can likewise take place during a shift process and/or at least temporarily after a shift process. The reduction of the maximum engine speed in neutral area furthermore still has the advantage of saving fuel.

The signals of the gear recognition sensor and where applicable the engaged state of the clutch can be transferred by the sensors directly to the engine control or through the control unit of the automated clutch to the engine control. The gear recognition sensor can be a switch which detects the engaged neutral area. In another embodiment this sensor can detect at least some or all of the gears engaged in the gearbox.

The invention is not restricted to the embodiment of the description. Numerous modifications and alterations are possible within the scope of the claims, more particularly those variations, elements and combinations and/or materials which are combinations or modifications of individual features or elements or method steps contained in the drawings and described in connection with those in the general description and embodiments and claims.

Claims

CLAIMS 1. Motor vehicle with a drive motor, a gearbox, a manually or automatically operable torque transfer system, a gear recognition sensor for detecting the gear ratio engaged in the gearbox, and a motor control unit for controlling the torque of the drive motor, characterised in that on detection of neutral as the engaged gearbox state, the maximum controllable value of the engine speed is reduced.
2. Motor vehicle as claimed in Claim 1, wherein the reduction follows disengagement of the torque transfer system.
3. Motor vehicles as claimed in Claim 1, wherein the reduction follows engagement of the torque transfer system.
4. Motor vehicle as claimed in any preceding claim, wherein the torque transfer system is automatically operable and a control unit is provided for controlling a controllable actuation unit for actuation of the torque transfer system.
5. Motor vehicle substantially as herein described with reference to Figure 3 of the accompanying drawings.