TECHNICAL FIELD

The present invention relates to a method for improving the drivability of a motor vehicle with a transmission. The invention relates also to a computer programme product comprising programme code for a computer for implementing a method according to the invention. The invention relates also to a device and a motor vehicle equipped with the device.

BACKGROUND

Today there are vehicles in which a conventional mechanical gear lever has been replaced by a so-called electronic gear lever. An electronic gear lever is particularly advantageous in vehicles in which a gearbox of the vehicle is situated in a rear portion of the vehicle. The electronic gear lever is a gear lever adapted to communication with a control unit of the vehicle. The control unit is adapted to using control signals to control gear change processes of a transmission of the vehicle via various operating means, e.g. solenoid valves. Such a system is referred to, for example, as an electro-pneumatic system. The vehicle manufacturer Scania uses in certain vehicles a system called "shift by wire".

A disadvantage of such an electro-pneumatic system is the need to feed information back to the driver so that he/she may be aware that a new gear has been engaged, to which end the driver may receive an indication or acknowledgement that the new gear has been engaged and that a clutch pedal may be released to achieve a closed driveline of the vehicle. A gear lever suitable for such an electro-pneumatic system is therefore relatively expensive, since such systems may have a feedback system built into them.

A gear lever suitable for such an electro-pneumatic system is therefore also relatively complicated. In contrast, in a conventional system in which there is an entirely mechanical gear lever the driver can perceive via the gear lever when a new gear has been engaged, whereupon he/she may release the clutch pedal. As indicated above, however, these conventional systems are not suitable for all types of vehicles. Such conventional systems are also not as user-friendly as an electro-pneumatic system.

Another currently known practice is to have an electronic control system of the vehicle take over control of an engine of the vehicle when a gear of the vehicle's transmission is engaged in a neutral step during a gear change process, in order thereafter to coordinate a gear manoeuvre with the engine of the vehicle. This makes it possible for the driver to be permitted to release the clutch pedal during the gear change, resulting in no need to provide him/her with acknowledgement that he/she has permission to release the clutch pedal. A disadvantage of this method is that the driver may feel that he/she does not have full control of the process and cannot him/herself balance clutch and power demand after the gear change has been effected.

WO 2008/026993 describes a method for changing gear in a "gear by wire" system in a vehicle which comprises a clutch, gearbox and means for controlling the clutch, for manual control of the latter's engagement and disengagement, and gear selector means which allow manual indication of a desired gear.

However, there is a need to provide a method and device for improving the drivability of existing motor vehicles so that the disadvantages mentioned above can be overcome. SUMMARY OF THE INVENTION

An object of the present invention is to propose a novel and advantageous method for improving the drivability of a motor vehicle.

Another object of the invention is to propose a method, a device and a computer programme for improving the drivability of a motor vehicle.

A further object of the invention is to propose a method and computer programme for effecting a user-friendly method for improving the drivability of a motor vehicle.

These objects are achieved with a method for improving the drivability of a motor vehicle, which method comprises the steps according to claim 1.

It is with advantage made possible to avoid incorrect handling of gear changing. With the innovative method, the driver is prevented from sliding the vehicle's clutch together before a new gear step of the gearbox has been engaged.

A first state of the clutch may involve the clutch of a transmission of the vehicle being fully open, resulting in an interruption of power in the vehicle's transmission.

A second state of the clutch may involve the clutch being not fully open.

Any desired gear step may be a preselected gear step.

The method may further comprise the step of indicating for a driver that a gear step other than the neutral gear step of the gearbox is engaged, making it possible for control of the vehicle's engine and gearbox to be returned to a driver of the vehicle. Using presentation means to provide the driver with acknowledgement that a gear step other than the neutral gear step of the gearbox is engaged makes it possible to avoid using an expensive gear lever with an acknowledgement function. The method according to an aspect of the invention may thus represent a cost-effective solution to the problem of improving the drivability of a motor vehicle.

The method is easy to implement in existing motor vehicles. Software for automatic deactivation and activation of operating means during a gear change procedure, e.g. accelerator pedal and clutch pedal, on the basis of action taken by the driver may, according to the invention, be installed in a control unit of the vehicle during the manufacture of the vehicle. A purchaser of the vehicle may thus have the possibility of selecting the function of the method as an option. Alternatively, software which comprises programme code for effecting the innovative method for improving the drivability of a motor vehicle may be installed in a control unit of the vehicle on the occasion of upgrading at a service station, in which case the software may be loaded into a memory of the control unit. Implementing the innovative method is therefore cost-effective in various aspects, particularly as no further knobs, buttons or electronic components need be installed in the vehicle. Presentation means which currently already exist may be used to perform an acknowledgement function according to an aspect of the invention. Necessary hardware, e.g. a control unit of the vehicle, is currently already provided in the vehicle. The invention therefore represents a cost-effective solution to the problem of improving the drivability of a motor vehicle.

Software which comprises programme code for improving the drivability of a motor vehicle is easy to update or replace. Various portions of the software which comprise programme code for improving the drivability of the motor vehicle may also be replaced independently of one another. This modular configuration is advantageous from a maintenance perspective. The objects indicated above are also achieved with a device for improving the drivability of a motor vehicle, which device comprises the features according to claim 6. Advantageous embodiments are indicated in the dependent claims 7-9.

The innovative device may allow a driver to have full control of the vehicle's engine and gearbox, provided that he/she releases the clutch pedal after a new gear step has been initiated. When the driver begins to release the clutch pedal, a change from a first state (a fully open position) to a second state (a not fully open position) of the clutch is detectable. Acknowledgement that a new gear step has been initiated may be provided via presentation means.

If during a gear change procedure the vehicle's driver releases the clutch too early, i.e. before a new gear step has been initiated, a control unit of the vehicle is adapted to taking over control of the gear change procedure and ensuring that the gear change is effected without damage to a gearbox of the vehicle. The control unit is also adapted to handing over control of the engine and gearbox to the driver in a predetermined way after correctly effected engagement of a preselected gear step. The transfer of control to the driver takes place preferably in a controlled way with ramping of a prevailing engine torque to an engine torque requested by the driver.

These objects are also achieved with a motor vehicle which comprises the features according to claim 10. The motor vehicle may be a truck, bus or passenger car.

These objects are also achieved with a computer programme for improving the drivability of a motor vehicle, which computer programme comprises programme code stored on a computer-readable medium for causing an electronic control unit or another computer connected to the electronic control unit to perform the steps indicated in claims 1-5. These objects are also achieved with a computer programme product comprising a programme code stored on a computer-readable medium for performing the method steps according to claims 1-5.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas the invention is described below, it should be noted that it is not limited to the specific details described. Specialists having access to the teachings herein will recognise further applications, modifications and incorporations within other fields, which are within the scope of the invention.

CONCISE DESCRIPTION OF THE DRAWINGS

For fuller understanding of the present invention and further objects and advantages thereof, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which:

Figure 1 illustrates schematically a vehicle according to an embodiment of the invention;

Figure 2 illustrates schematically a subsystem for the vehicle depicted in

Figure 1 , according to an embodiment of the invention; Figure 3 is a schematic diagram showing how various parameters of the motor vehicle depend on time, according to an embodiment of the invention;

Figure 4a is a schematic flowchart of a method for improving the drivability of a motor vehicle, according to an embodiment of the invention;

Figure 4b is a schematic flowchart in more detail of a method for improving the drivability of a motor vehicle, according to an embodiment of the invention; and Figure 5 illustrates schematically a computer according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a side view of a vehicle 100. The exemplified vehicle 100 comprises a tractor unit 110 and a trailer 112. The vehicle may be a heavy vehicle, e.g. a truck or a bus. The vehicle may alternatively be a passenger car. The vehicle 100 is a motor vehicle with automated transmission.

The term "link" refers herein to a communication link which may be a physical connection such as an opto-electronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link.

Figure 2 depicts a subsystem 299 of the vehicle 100. The subsystem 299 is situated in the tractor unit 110. The subsystem 299 has an engine 230. The engine 230 may be a combustion engine. The combustion engine may be an engine with six cylinders. The combustion engine may alternatively have four, five or eight cylinders. The combustion engine may be a diesel engine. The combustion engine may alternatively be a petrol, gas or ethanol engine.

The engine 230 has an output shaft 231 connected to a clutch 235. The clutch may for example be of a conventional disc type, such as a two-disc clutch. The clutch 235 is also connected to a shaft 236. The shaft 236 is an input shaft to a gearbox 240. The gearbox 240 has an output shaft 243 adapted to transmitting power from the engine to a number of vehicle wheels 245 in a conventional manner. The clutch 235 is adapted to being able to interrupt the power transmission in the driveline of the motor vehicle 100, which driveline comprises the shaft 231 , the clutch 235, the shaft 236, the gearbox 240 and the shaft 243. According to a version, a control unit 200 is adapted to controlling both the clutch 235 and the gearbox 240. The control unit 200 is adapted to communication with the clutch 235 via a link 237. The control unit 200 is adapted to communication with the gearbox 240 via a link 239.

A second control unit 210 is adapted to communication with the control unit 200 via a link 215. The second control unit 210 may be detachably connected to the control unit 200. The second control unit 210 may be a control unit external to the vehicle 100. The second control unit 210 may be adapted to performing the innovative method steps according to the invention. The second control unit 210 may be used to cross-load software to the control unit 200, particularly software for effecting the innovative method. The second control unit 210 may alternatively be adapted to communication with the control unit 200 via an internal network in the vehicle. The second control unit 210 may be adapted to performing substantially similar functions to the first control unit, e.g. controlling the engine 230, the clutch 235 and the gearbox 240 on the basis of information received from a control 280.

According to this version, the control unit 200 is also adapted to controlling the engine 230 via a link 233.

The control unit 200 is signal-connected via a link 251, or is connected in some other way, to first operating means 250. The operating means 250 may be an acceleration control, e.g. an accelerator pedal for manual action by a driver of the motor vehicle 100. The control unit 200 is adapted to controlling inter alia the engine 230 in response to manual action upon the operating means 250.

The control unit 200 is signal-connected via a link 261, or is connected in some other way, to second operating means 260. The operating means 260 comprise a clutch control, e.g. a clutch pedal for manual action by a driver of the motor vehicle 100. The control unit 200 is adapted to controlling the clutch 235 in response to manual action upon the operating means 260. Separate control units may of course be provided for the engine and the gearbox respectively, in which case they need to be connected together to enable them to communicate relevant information between them.

According to a version, the control unit 200 is adapted to controlling the gearbox 240 via a link 239. To this end, the control unit 200 is signal- connected to operating means (not depicted) for gear step change in the gearbox.

The control unit 200 is signal-connected via a link 271, or is connected in some other way, to presentation means 270. The presentation means 270 may be any type of visual presentation means, e.g. a viewing screen. The presentation means 270 may according to a version be a light-emitting diode (LED). The presentation means 270 may be any type of light-generating presentation means which comprises a loudspeaker to generate acoustic signals, e.g. "beep" signals.

The presentation means 270 are adapted to presenting, during a gear change procedure, an acknowledgement that a new gear step has been engaged. The acknowledgement is an indication that the driver may release the clutch pedal 260 in order to slide together the clutch 235. The acknowledgement may be provided in any desired way. According to a version, the acknowledgement takes the form of information comprising one or more alphanumeric characters displayed on the viewing screen.

According to a version, the acknowledgement takes the form of information comprising one or more symbols displayed on the viewing screen. According to a version, the acknowledgement takes the form of a beam of light of any desired colour emitted from the LED. For example, a "green" colour may indicate that a new gear step has been engaged and that the driver may therefore release the clutch pedal without risk. According to an example, the acknowledgement takes the form of any desired acoustic signal generated and delivered via the loudspeaker.

The presentation means 270 may also take the form of an audiovisual unit adapted to providing in any desired way, e.g. by combined light and acoustic signals, an acknowledgement that a new gear step has been engaged in the vehicle's transmission, so that a driver becomes aware that the clutch pedal may be released without risk.

The presentation means 270 may be set manually by a driver of the vehicle. This means that a certain type of desired feedback may be set by the vehicle's driver. A "tailor-made" acknowledgement that a new gear step has been engaged in the vehicle's transmission may thus be provided.

The control unit 200 is signal-connected via a link 281 , or is connected in some other way, to a control 280 for gear step selection in the gearbox 240. The control 280 may be a gear lever.

Figure 3 is a schematic diagram showing how various parameters of the motor vehicle depend on time, according to an embodiment of the invention.

In the diagram, a continuous graph f represents a speed of the vehicle's engine. There is also a continuous graph e representing a position of the vehicle's clutch 235. A position of the clutch is associated with a position of the vehicle's clutch pedal.

Before a time T31 , a certain speed of the engine prevails. Before time T31, the clutch is closed and the vehicle's driveline transmits torque generated by the engine.

Two different cases are described below. In the first case, the clutch is fully open in the driveline at time T31. Thereafter, a selected gear step is engaged at a time T42. After the new gear step has been engaged, the driver may so act upon the clutch pedal and the accelerator pedal that the clutch begins to slide together at a time T43. At a time T34 the clutch is fully closed. During a time period T31-T43 the driver will have the clutch pedal fully depressed, keeping the vehicle's clutch fully open. This first case is represented by the two continuous lines e and f.

In the second case, the clutch is fully open in the driveline at time T31. Thereafter, the driver releases the clutch pedal at a time T41 , i.e. before a new gear step has been engaged, and the gearbox will have a neutral gear step engaged. According to the invention, this is detected and a control unit of the vehicle takes over control of the gear change procedure at this stage. According to an example, if it is detected that the driver releases the clutch pedal too early, the control unit will take over control of the gear change procedure before the clutch has closed. The control unit preferably takes over control of the gear change procedure when the driver has released the clutch pedal to a predetermined position relative to its fully depressed position. The predetermined position of the clutch pedal and its fully depressed position are preferably close to one another. According to this first case, the driver retains control of the clutch pedal and the accelerator pedal.

According to the second case, the control unit is adapted to taking over control of the gear change procedure as above and engaging the new gear step. When the new gear step at a time T44 is engaged, control of the accelerator pedal is handed back to the driver. The vehicle parameters of engine speed and clutch position are represented in the second case by the discontinuous graphs f* and e* respectively. According to this second case, the driver does not retain control of the engine and gearbox when it is detected that he/she intends to release the clutch pedal during a gear change procedure, when a neutral step of the gearbox is engaged, before a selected gear step has been engaged in the gearbox. Control of the accelerator pedal may be handed over to the driver after the new gear step has been automatically engaged. The transfer is effected in a controlled way.

Figure 4a is a schematic flowchart of a method for improving the drivability of a motor vehicle during a gear change procedure whereby there is a neutral gear step of a gearbox of a transmission of the vehicle, comprising the step of detecting when a first state of a clutch of the vehicle changes to a second state. The method step s401 comprises also the steps of taking control of an engine and gearbox of the vehicle from a driver of the vehicle, where appropriate, on the basis of said detection, in order to automatically control the gear change procedure in such a way that any desired gear step of the gearbox is engaged, and of thereafter returning control of the vehicle's engine and gearbox to a driver. After step s401 the method ends.

Figure 4b is a schematic flowchart in more detail of a method for improving the drivability of a motor vehicle during a gear change procedure whereby there is a neutral gear step of a gearbox of a transmission of the vehicle, according to an embodiment of the invention. The method comprises a first step s410. Step s410 incorporates the step of detecting whether a new gear step of the vehicle's gearbox has been selected. Step s410 incorporates the step of detecting whether a neutral gear step of the gearbox has been engaged. Step s410 incorporates the step of detecting whether a clutch pedal of the vehicle is fully depressed. If a new gear step of the vehicle's gearbox has been selected and a neutral gear step of the gearbox has been engaged and a clutch pedal of the vehicle is fully depressed, a subsequent step s420 is performed.

Method step s420 determines whether a driver is acting upon the clutch pedal in such a way that the clutch may be assumed to be about to be closed and thereby provide power transmission in the vehicle's driveline. If the driver acts upon the vehicle's clutch pedal in such a way, a subsequent step s430 is performed. If the driver does not act upon the vehicle's clutch pedal in such a way, the new gear step is expected to be engaged and the method ends. According to a version, a signal containing information that a new gear step has been engaged is sent. This signal may be used to indicate for the driver that a new gear step has been engaged.

Method step s430 effects automatic transfer of control of the engine and gearbox from the driver to the control unit 200. The vehicle's driver will thus no longer be able to influence the gear change procedure by using, for example, the clutch pedal and the accelerator pedal, but will still be able to use the gear lever to select new target gears. Step s430 is followed by a step s440.

Method step s440 effects an adjustment of the speed of the engine to reach a certain engagement speed for the clutch. When the engine's clutch engagement speed has been reached, the new gear step is engaged. Step s440 is followed by a step s450.

Method step s450 effects automatic transfer of control of the engine and gearbox from the control unit 200 to the driver. The vehicle's driver may thus resume control of the engine and gearbox in order to drive the vehicle as desired. Step s450 is followed by a step s460.

Method step s460 sends a signal containing information that a new gear step has been engaged. This signal may be used to indicate for the driver that a new gear step has been engaged. Step s460 is discretionary. According to an example, no acknowledgement is therefore sent to the driver, but it is tacitly understood that the driver has to wait a long enough period of time before he/she may, for example, again try to select a new gear step of the gearbox. Thereafter the method ends. Figure 5 is a diagram of a version of a device 500. The control units 200 and 210 described with reference to Figure 2 may in a version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer programme, e.g. an operating system, is stored for controlling the function of the device 200. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

According to an aspect of the invention, a computer programme P is provided which comprises routines for improving the drivability of a motor vehicle during a gear change procedure whereby there is a neutral gear step of a gearbox of a transmission of the vehicle. The programme P comprises routines for, where appropriate, taking control of the operating means 250 and 260 from a driver during a gear change procedure and automatically controlling the gear change procedure in such a way that any desired gear step of the gearbox is engaged, and thereafter returning control of the operating means 250 and 260 to a driver, in accordance with the innovative method. The programme P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550.

Where it is stated that the data processing unit 510 performs a certain function, it means that the data processing unit 510 effects a certain part of the programme which is stored in the memory 560 or a certain part of the programme which is stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory

560 is intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 is intended to communicate with the data processing unit 510 via a data bus 514. The links 233, 237, 239, 251, 261 , 271 and 215, for example, may be connected to the data port 599 (see Figure 2).

When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 will be ready to effect code execution in a manner described above.

Parts of the methods herein described may be effected by the device 500 by means of the data processing unit 510 which runs the programme stored in the memory 560 or the read/write memory 550. When the device 500 runs the programme, methods herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to limit the invention to the variants described. Many modifications and variants will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order best to make clear the principles of the invention and its practical applications and hence to make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.