WO2006098672A1

WO2006098672A1 - A system and a method for controlling the operation of a vehicle engine

Info

Publication number: WO2006098672A1
Application number: PCT/SE2006/000047
Authority: WO
Inventors: Jon Andersson
Original assignee: Scania Cv Ab (Publ)
Priority date: 2005-03-17
Filing date: 2006-01-12
Publication date: 2006-09-21
Also published as: SE0500607L; SE529055C2; DE112006000353T5

Abstract

A system and method for controlling the operation of a vehicle engine (2), the output shaft (5) of which being connected to driving wheels of the vehicle via a clutch (3) and a gearbox (4). A first control mode, in which the engine is controlled to keep the actual vehicle speed equal to the set vehicle speed, is suspended when a movement of the clutch lever (7) in the clutch disengaging direction is sensed. When a movement is sensed and on condition that it has been established that the first control mode is to be resumed on clutch reengagement, the engine is controlled according to a second control mode, in which the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft (6a) is reduced before the reengagement of the clutch takes place.

Description

A system and a method for controlling the operation of a vehicle engine Technical field

[0001] The present invention relates to a system for controlling the operation of a vehicle engine according to the preamble of claim 1 and 34, respectively. The invention also relates to a method for controlling the operation of a vehicle engine, a computer program comprising computer program code for implementing said method, a computer program product comprising a data storage medium readable by an electronic control unit and having a computer program adapted to make an electronic control unit implement said method stored thereon, and an electronic control unit.

Background art

[0002] Motor vehicles, such as cars, lorries, towing vehicles and buses, are often provided with a so-called speed control system, also denominated cruise control system, for automatically maintaining a desired vehicle speed. Such a control system comprises means, such as a vehicle speed sensor, for monitoring the actual vehicle speed. The speed control system compares the actual vehicle speed to a set vehicle speed, which is the speed at which automatic control is desired. The set vehicle speed is usually entered into the speed control system as the prevailing actual vehicle speed when a set switch is actuated by the driver. The speed control system generates an error signal by comparing the actual vehicle speed to the set vehicle speed. The error signal is then used to control an actuator coupled to the fuel pump or to the vehicle throttle in order to change the engine speed until the error signal is substantially zero, i.e. until the actual vehicle speed is equal to the set vehicle speed.

[0003] When the speed control system is used on a vehicle having a manual transmission, it may occasionally be necessary for the vehicle driver to manually shift the transmission to another gear while the speed control system is operational. This may for instance be necessary when the vehicle encounters an uphill slope. In such a situation, it is necessary to suspend operation of the speed control system during the gear shift; otherwise the speed control system will operate to dramatically increase the engine speed when the clutch is disengaged. Several methods have been developed in the prior art to suspend operation of the speed control system when the clutch is disengaged. Some prior art systems use a switch that senses depression of the vehicle clutch pedal, the output of the switch being used to trigger suspension of the speed control system. Once the driver has completed shifting the transmission to another gear, it is desirable to resume operation of the speed control system. The speed control system cannot be simply resumed when the clutch pedal sensor indicates that the clutch has been engaged. The driver may for instance have shifted the transmission into neutral position, in which case resumption of speed control would result in a dramatic increase in engine speed. Therefore, many prior art systems are provided with a resume switch, which must be actuated by the driver in order to resume the speed control. However, many drivers find it annoying to have to actuate the resume switch after every gear change. In order to avoid this problem, prior art systems have been proposed which incorporate a sensor switch on the gear shift lever. Once a shift into a new gearing has been performed by the driver, as indicated by the gear shift lever sensor, and the clutch has been engaged, as indicated by the clutch pedal sensor, the speed control system is automatically resumed, without the need for the driver to actuate a resume switch.

[0004] Another type of method for automatic suspension and resumption of speed control after gear change is previously known from US-A-5 680 309. The method according to US-A-5 680 309 comprises the steps of:

• sensing a start of the gear change;

• suspending operation of the speed control system;

• beginning measurement of an elapsed time;

• sensing a completion of the gear change; and

• resuming operation of the speed control system if the elapsed time is less than a predetermined limit.

Disclosure of the invention [0005] The object of the present invention is to achieve a further development of a speed control system of the above-mentioned type so as to provide a function thereof that is improved in at least some aspect.

[0006] According to a first aspect of the invention, said object is achieved by means of a system having the features defined in claim 1 and a method having the features defined in claim 18.

[0007] The solution according to the first aspect of the invention implies that the resumption of the speed control, here denominated first control mode, after gear shift is preceded by an engine control mode, here denominated second control mode, in which the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft is reduced before the reengagement of the clutch takes place. Said second control mode is initiated when a movement of the clutch lever in the clutch reengaging direction is sensed and on condition that it has been established that the first control mode is to be resumed on clutch reengagement. Hereby, the rotational speed difference prevailing between the engine output shaft and the gearbox input shaft at the moment of clutch reengagement is reduced, which in its turn results in a smoother running of the vehicle in connection with the resumption of the speed control as compared to the corresponding prior art systems.

[0008] In this description and the subsequent claims, the moment when "the reengagement of the clutch takes place" refers to the moment when the clutch has been brought into such a state that it is capable of transferring such a high torque from the engine output shaft to the gearbox input shaft that a prevailing essential difference in rotational speed between the engine output shaft and the engine input shaft will make the vehicle driver experience a jerk in the vehicle.

[0009] According to an embodiment of the invention, the rotational speed of the engine output shaft is in the second control mode made to assume a desired value before the reengagement of the clutch takes place, said desired value representing either the prevailing rotational speed of the gearbox input shaft or an assumed value of the prevailing rotational speed of the gearbox input shaft. [0010] According to another embodiment of the invention, the desired value is a calculated or measured value of the prevailing rotational speed of the gearbox input shaft. Hereby, a very smooth running of the vehicle in connection with the resumption of the speed control is secured. According to a more simplified embodiment, the desired value essentially corresponds to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is sensed. The latter solution is based on the realisation that the rotational speed of the gearbox input shaft is only changed to a smaller extent in connection with a normal gear shift when the vehicle is running with the speed control in operation. Thus, the latter solution will normally give a satisfactory approximation of the rotational speed of the gearbox input shaft prevailing at the moment of clutch reengagement after a performed gear shift.

[0011] According to another embodiment of the invention, it is calculated, based on information as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the reengagement of the clutch will take place, the information as to said moment being taken into account during the second control mode. Hereby, it can be secured that the rotational speed of the engine output shaft is changed at a suitable pace during the second control mode so that the desired value is reached with certainty before the reengagement of the clutch takes place.

[0012] According to another embodiment of the invention, the first control mode, i.e. the speed control, is interrupted if the rotational speed of the engine exceeds a predetermined limit value after the reengagement of the clutch. Hereby, a dramatic increase in engine speed after the resumption of the speed control may be avoided.

[0013] According a second aspect of the invention, said object is achieved by means of a system having the features defined in claim 34 and a method having the features defined in claim 37.

[0014] The solution according to the second aspect of the invention implies that the suspension of the first control mode, i.e. the suspension of the speed control, in connection with a detected movement of the clutch lever in the clutch disengaging direction is followed by a control mode in which the torque exerted by the engine is reduced in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place. This results in a smoother running of the vehicle in connection with the suspension of the speed control and the disengagement of the clutch as compared to the corresponding prior art systems.

[0015] According to an embodiment of the invention, it is calculated, based on information as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the complete disengagement of the clutch will take place, the information as to said moment being taken into account during the control mode initiated after the suspension of the speed control. Hereby, it can be secured that the torque of the engine is reduced at a suitable pace during the torque reducing control mode so that the torque is essentially down to zero with certainty before the complete disengagement of the clutch takes place. [0016] Further advantages as well as advantageous features of the system and the method according to the present invention will appear from the subsequent description and the dependent claims. [0017] The invention also relates to a computer program according to claim 33 and claim 38, respectively, a computer program product according to claim 39 and an electronic control unit according to claim 40. Brief description of the drawings

[0018] The invention will in the following be more closely described by means of embodiment examples, with reference to the appended drawings, where: Fig 1 is a schematical outline diagram illustrating a system according to the present invention, Fig 2 is a schematical perspective view of a conventional gear shift lever for a heavy motor vehicle,

Fig 3 is an outline diagram of an electronic control unit for implementing a method according to the invention, Fig 4 is a flow diagram detailing a method according to a first embodiment of the invention, and

Fig 5 is a flow diagram detailing a method according to a second embodiment of the invention.

Mode(s) for carrying out the invention

[0019] A part of a driving link 1 of a motor vehicle is schematically illustrated in

Fig 1. The driving link 1 comprises a vehicle engine 2, e.g. in the form of a conventional combustion engine, which is connected to driving wheels (not shown) of the vehicle via a clutch 3 and a gearbox 4. The output shaft 5 of the engine 1 is connected to the input shaft 6a of the gearbox via said clutch 3, which is arranged to transfer the torque exerted by the engine to the input shaft 6a of the gearbox. The clutch 3 is controlled by the driver of the vehicle via a clutch lever 7, normally in the form of a clutch pedal. The clutch 3 is disengaged by depression of the clutch lever 7 and reengaged by allowing the clutch lever to return to its initial position. When the clutch 3 is completely disengaged, the engine output shaft 5 is disconnected from the gearbox input shaft 6a and the gearing may be changed without any torque being transferred from the engine to the gearbox.

[0020] In this description and the subsequent claims the "output shaft" of the engine refers to the shaft that is arranged to connect the engine to the clutch. This shaft 5 may constitute or be directly connected to the main shaft of the engine, in which case it is rotating with the rotational speed of the engine. This is the case when the main shaft of the engine is directly connected to the clutch 3. However, the main shaft of the engine may also be indirectly connected to the clutch 3. In the latter case, the main shaft of the engine is connected to said output shaft 5 via a gearing, which makes the output shaft 5 rotate with a rotational speed differing from the rotational speed of the engine.

[0021] In the illustrated example, the gearbox 4 is of a type comprising a so- called split gear 4a, a conventional gear 4b and a so-called range gear 4c connected in series between the input shaft 6a and the output shaft 6b of the gearbox. These gears 4a-4c are controlled by the driver via a gear shift lever 8. An example of a gear shift lever 8 for controlling a gearbox 4 of the type here in question is illustrated in Fig 2. This gear shift lever 8 has three different members for selecting the desired gearing in the gearbox 4. One of these members is the lever 8 itself, which is movable in the directions indicated with the arrow A between different given positions representing different gearings in the conventional gear 4b. The lever 8 may be directly connected to the gear 4b, as illustrated in Fig 1 , so as to mechanically control the gearing in this gear 4b. As an alternative, the lever 8 may be indirectly connected to the gear 4b. In the latter case, switches are provided to sense the position of the lever 8 and the gear 4b is controlled by a control unit based on signals from these switches. A second of said members is provided on the lever 8 in the form of a switch 8a, by means of which two different gearings of the split gear 4a may be selected. The split gear 4a is consequently controlled based on signals from said switch 8a. A third of said members is provided on the lever 8 in the form of a displaceable sleeve 8c, which is displaceable in the directions indicated with the arrow B between two given positions representing two different gearings of the range gear 4c. Switches are provided to sense the position of the sleeve 8c and the range gear 4c is controlled based on signals from these switches. The illustrated gearbox 4 and gear shift lever 8 are of conventional type for use in heavy motor vehicles such as lorries and towing vehicles.

[0022] The inventive system 10 comprises speed setting means 11 for setting a desired vehicle speed. The speed setting means 11 may for instance comprise a set member, such as a depressible switch, to be actuated by the driver when the vehicle is running at a speed which the driver wants to maintain. By actuation of the set member, the prevailing vehicle speed is entered as the value of the desired vehicle speed.

[0023] The system 10 further comprises engine control means 12, e.g. in the form of an electronic control unit, which is adapted to control the engine 2, e.g. by controlling the amount of fuel injected into the engine. The engine control means 12 is arranged to receive information as to the set vehicle speed, i.e. the set value of the desired vehicle speed, from the speed setting means 11 and is, in a first control mode, adapted to control the engine in dependence on the information as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed. Consequently, the engine control means 12 performs a conventional speed control function in this first control mode. The first control mode is triggered by the actuation of the speed setting means 11.

[0024] The actual vehicle speed, i.e. the prevailing speed at which the vehicle is running, may be measured or estimated in any suitable manner. The speed of a vehicle may for instance be estimated based on measuring values of the rotational speed of some part of the vehicle's drive shaft, such as the output shaft 6b of the gearbox 4. In the example illustrated in Fig 1 , the actual vehicle speed is determined by speed determining means comprising a member 13 arranged to generate a value representing the rotational speed of the gearbox output shaft 6b. The engine control means 12 is arranged to receive information as to the actual vehicle speed from said speed determining means.

[0025] The system 10 further comprises sensing means 14 for sensing manoeuvring movements of the vehicle clutch lever 7. This sensing means is preferably adapted to sense the prevailing manoeuvring position of the clutch lever 7 as well as the velocity at which the clutch lever is moved. The engine control means 12 is arranged to receive information as to movements of the clutch lever 7 from the sensing means 14.

[0026] The engine control means 12 is adapted to suspend the first control mode when a movement of the clutch lever 7 in the clutch disengaging direction is sensed by the sensing means 14, i.e. when it is established by means of the sensing means 14 that the driver depresses the clutch lever 7. After having suspended the first control mode, the engine control means 12 is adapted to determine, based on different parameters, whether or not to resume the first control mode on a subsequent clutch reengagement. One parameter may be the time elapsed between the suspension of the first control mode and the subsequent reengagement of the clutch. If the elapsed time exceeds a predetermined limit, e.g. in the order of 2-4 seconds, at the moment when a movement of the clutch lever 7 in the clutch reengaging direction is sensed by the sensing means 14, the engine control means 12 is adapted not to resume the first control mode on clutch reengagement. In this case, the system comprises time measuring means 15, for measuring the time elapsed since the last suspension of the first control mode. The time measuring means 15 may be integrated in one and the same unit as the engine control means 12, but may of course also be arranged as a separate unit which is connected to the engine control means so as to send time information thereto.

[0027] Another parameter, may be the activation of a brake function, i.e. the use of a brake of the vehicle, after the suspension of the first control mode and before the subsequent reengagement of the clutch. In this case, the engine control means 12 is adapted not to resume the first control mode if it has been established that a brake function has been activated after the last suspension of the first control mode. In this case, the system comprises brake detecting means (not shown) for detecting the activation of a brake function of the vehicle. The engine control means 12 is arranged to receive information as to the activation of a brake function from the brake detecting means.

[0028] Another parameter may be the change of the vehicle speed during the time period between the suspension of the first control mode and the subsequent reengagement of the clutch. In this case, the engine control means 12 is adapted not to resume the first control mode if it has been established that the vehicle speed has changed, by being increased or decreased, more than a predetermined limit value, e.g. in the order of +/- 10 km/h, after the last suspension of the first control mode. In this case, the system comprises speed change determining means (not shown) for determining the change of the vehicle speed after a suspension of the first control mode. The engine control means 12 is arranged to receive information as to said speed change from the speed change determining means. This parameter is based on the realisation that the vehicle speed is only changed to a smaller extent in connection with a normal gear shift when the vehicle is running with the speed control in operation and the driver intends to keep running with the speed control in operation after the gear shift.

[0029] Another parameter may be that the gearbox has been placed in gear, i.e. that the gearbox is not in the neutral state, when the clutch is reengaged. This may be established in any suitable manner, e.g. by means of switches sensing the position of the gear shift lever 8 or by evaluation of the gear ratio values. The gear ratio values may for instance be established by forming the ratio between measuring values representing the rotational speed of the gearbox input shaft and measuring values representing the rotational speed of the gearbox output shaft. In this case, the engine control means 12 is adapted to resume the first control mode only if it has been established that the gearbox has been placed in gear when a movement of the clutch lever 7 in the clutch reengaging direction is sensed by the sensing means 14. In this case, the system comprises detecting means (not shown) for detecting whether or not the gearbox is placed in gear. The engine control means 12 is arranged to receive information as to whether or not the gearbox is placed in gear from said detecting means. As an alternative, according to which the system may lack detecting means for detecting whether or not the gearbox is placed in gear, the engine control means 12 may be adapted to resume the first control mode on the reengagement of the clutch 3 irrespective of whether or not the gearbox 4 has been placed in gear, but of course on condition that any other requirement for such a resumption has been fulfilled. In the latter case, the engine control means 12 is adapted to rapidly interrupt the first control mode if the rotational speed of the engine exceeds a predetermined limit value after the reengagement of the clutch.

[0030] According to the invention, the engine control means 12 is adapted to start operating according to a second control mode when a movement of the clutch lever 7 in the clutch reengaging direction is sensed by the sensing means 14 and on condition that it has established that the first control mode is to be resumed on clutch reengagement, the engine control means 12 being adapted in said second control mode to control the engine 2 so as to reduce the difference between the rotational speed of the engine output shaft 5 and the rotational speed of the gearbox input shaft 6a before the reengagement of the clutch takes place. The engine control means 12 is suitably adapted in the second control mode to control the engine 2 so as to make the rotational speed of the engine output shaft 5 assume a desired value before the reengagement of the clutch takes place, said desired value representing either the prevailing rotational speed of the gearbox input shaft 6a or an assumed value of the prevailing rotational speed of the gearbox input shaft 6a.

[0031] According to a simplified solution, said desired value is set to correspond to the rotational speed of the gearbox input shaft 6a prevailing at the moment when the movement of the clutch lever 7 in the clutch disengaging direction is sensed by the sensing means 14. Consequently, the rotational speed of the gearbox input shaft 6a prevailing shortly before the disengagement of the clutch 3 is in this case used as a roughly assumed value of the prevailing rotational speed of the gearbox input shaft 6a at the moment of clutch reengagement.

[0032] According to a another solution, said desired value is set depending on the position of the split gear switch 8a of the gear shift lever 8 at the moment when the movement of the clutch lever 7 in the clutch disengaging direction is sensed and the position of the split gear switch 8a at the moment when the movement of the clutch lever 7 in the clutch reengaging direction is sensed. If it is established that the position of the split gear switch 8a has been changed after the last suspension of the first control mode, said desired value is set to a value corresponding to the rotational speed of the gearbox input shaft 6a prevailing at the moment when the movement of the clutch lever 7 in the clutch disengaging direction is sensed by the sensing means 14 minus a predetermined value, e.g. in the order of 100-400 rpm, if the new position of the split gear switch 8a represents a gear change up, and plus a predetermined value, e.g. in the order of 100-400 rpm, if the new position of the split gear switch 8a represents a gear change down. If it is established that the split gear switch 8a has not been actuated during the time period between the suspension of the first control mode and the subsequent movement of the clutch lever 7 in the clutch reengaging direction, the desired value may be set to correspond to the rotational speed of the gearbox input shaft 6a prevailing at the moment when the movement of the clutch lever 7 in the clutch disengaging direction was sensed by the sensing means 14.

[0033] According to a more sophisticated solution, said desired value is a calculated or measured value of the prevailing rotational speed of the gearbox input shaft 6a. In this case, the system may for instance comprise sensing means (not shown) for sensing the rotation of the gearbox input shaft 6a so as to generate a value representing the rotational speed of the gearbox input shaft 6a. The engine control means 12 is then arranged to receive information as to the rotational speed of the gearbox input shaft 6a from said sensing means. As an alternative, the prevailing rotational speed of the gearbox input shaft 6a may be calculated based on information as to the rotational speed of the gearbox output shaft 6b and the gearing of the gearbox 4. The gearing of the gearbox 4 may for instance be determined by means of switches sensing the position of the gear shift lever 8.

[0034] The system suitably comprises calculating means 16 for calculating, based on information from the sensing means 14 as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the reengagement of the clutch will take place, the engine control means 12 being adapted to take information from the calculating means 16 as to said moment into account during the second control mode. In this case, the engine control means 12 could be adapted, in the second control mode, to control the engine 2 in such a manner that the rotational speed of the engine output shaft 5 essentially corresponds to the rotational speed of the gearbox input shaft 6a at the moment when the reengagement of the clutch takes place. The calculating means 16 may be integrated in one and the same unit as the engine control means 12, but may of course also be arranged as a separate unit which is connected to the engine control means so as to send information thereto as to said calculated moment.

[0035] The engine control means 12 is suitably adapted to start operating according to a third control mode after having suspended the first control mode on the detection by the sensing means 14 of a movement of the clutch lever 7 in the clutch disengaging direction, the engine control means 12 being adapted in said third control mode to control the engine 2 to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch 3 takes place. The system suitably comprises calculating means 16 for calculating, based on information from the sensing means 14 as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the complete disengagement of the clutch will take place, the engine control means 12 being adapted to take information from the calculating means 16 as to said moment into account during the third control mode.

[0036] In the example illustrated in Fig 1 , the rotational speed of the engine output shaft 5 is determined by rotational speed determining means comprising a member 18 arranged to generate a value representing the rotational speed of the engine output shaft 5. The engine control means 12 is arranged to receive information as to the rotational speed of the engine output shaft 5 from said rotational speed determining means.

[0037] The system preferably comprises enabling means 17 allowing the second control mode and/or the third control mode to be enabled and disabled at the choice of the vehicle driver. Said enabling means 17 could for instance comprise a press button or any other suitable switch. As an alternative, the enabling means 17 could be manoeuvred via a display and an associated actuator.

[0038] A flow diagram detailing a method according to first embodiment of the invention is shown in Fig 4. In a first step S1, a set value representing the desired vehicle speed is determined or received. The engine 2 is then (step S2) controlled according to a first control mode, in which the actual vehicle speed is kept essentially equal to the set vehicle speed. When a movement of the clutch lever 7 in the clutch disengaging direction is established, the first control mode is suspended (step S3), whereupon the engine 2 is controlled according to a third control mode (step S4), in which the torque exerted by the engine 2 is reduced in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place. Thereupon, it is determined whether or not the first control mode is to be resumed on clutch reengagement (step S5). If it is established that the first control mode is not to be resumed on clutch reengagement, the control sequence is ended. If it is established that the first control mode is to be resumed on clutch reengagement and when a movement of the clutch lever 7 in the clutch reengaging direction is established, the engine 2 is controlled according to a second control mode (step S6), in which the difference between the rotational speed of the engine output shaft 5 and the rotational speed of the gearbox input shaft 6a is reduced before the reengagement of the clutch takes place. The first control mode is then resumed on the reengagement of the clutch (step S7). The first control mode will be suspended again (step S3) when a new movement of the clutch lever 7 in the clutch disengaging direction is established, whereupon the procedure indicated by steps S4-S7 is repeated.

[0039] A flow diagram detailing a method according to second embodiment of the invention is shown in Fig 5. This embodiment comprises, in addition to the above-indicated steps S1-S7, a further step S8, in which it is controlled, after the resumption of the first control mode in step S7, whether or not the rotational speed of the engine 2 exceeds a predetermined limit value after the reengagement of the clutch. If it is established that the rotational speed of the engine 2 exceeds the limit value, the first control mode is interrupted (step S9) and the control sequence is ended. If it is established that the rotational speed of the engine 2 does not exceed the limit value, the control sequence will proceed and the first control mode will be suspended again (step S3) when a new movement of the clutch lever 7 in the clutch disengaging direction is established, whereupon the procedure indicated by steps S4-S9) is repeated.

[0040] Computer program code for implementing a method according to the invention is suitably included in a computer program, which is loadable directly into the internal memory of a computer, such as the internal memory of the main electronic control unit of the vehicle. Such a computer program is suitably provided via a computer program product comprising a data storage medium readable by an electronic control unit, which data storage medium has the computer program stored thereon. Said data storage medium is for instance an optical data storage medium in the form of a CD-ROM disc, a DVD disc etc, or a magnetic data storage medium in the form of a hard disc, a diskette, a cassette tape etc. The computer program according to an embodiment of the invention comprises computer program code for causing a computer, e.g. in the form of or an electronic control unit, to: determine or receive a set value representing a desired vehicle speed of a vehicle comprising a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox;

• determine or receive a value representing the actual vehicle speed; determine or receive values representing manoeuvring movements of the vehicle clutch lever; control the engine, in a first control mode, in dependence on the values as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed;

• suspend the first control mode when a movement of the clutch lever in the clutch disengaging direction is established and then control the engine so as to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place;

• determine whether or not to resume the first control mode on clutch reengagement; and

• when a movement of the clutch lever in the clutch reengaging direction is established and on condition that it has been established that the first control mode is to be resumed on clutch reengagement, control the engine so as to reduce the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft before the reengagement of the clutch takes place. [0042] Fig 3 very schematically illustrates an electronic control unit 40 comprising an execution means 41, such as a central processing unit (CPU), for executing computer software. The execution means 41 communicates with a memory 43, for instance of the type RAM, via a data bus 42. The control unit 40 also comprises data storage medium 44, for instance in the form of a memory of the type ROM, PROM, EPROM or EEPROM or a Flash memory. The execution means 41 communicates with the data storage medium 44 via the data bus 42. A computer program comprising computer program code for implementing a method according to the invention is stored on the data storage medium 44.

[0043] The inventive system is intended to be used in a motor vehicle, such as for instance a car, a lorry, a towing vehicle or a bus.

[0044] The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to modifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention as defined in the appended claims.

Claims

1. A system for controlling the operation of a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox, the system comprising:

- speed setting means (11) for setting a desired vehicle speed;

- engine control means (12) adapted, in a first control mode, to control the engine in dependence on information as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed; and

- sensing means (14) for sensing manoeuvring movements of the vehicle clutch lever; wherein the engine control means (12) is adapted to suspend the first control mode when a movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14), and wherein the engine control means (12), after having suspended the first control mode, is adapted to determine, based on different parameters, whether or not to resume the first control mode on clutch reengagement, characterized in that the engine control means (12) is adapted to start operating according to a second control mode when a movement of the clutch lever in the clutch reengaging direction is sensed by the sensing means (14) and on condition that it has established that the first control mode is to be resumed on clutch reengagement, the engine control means (12) being adapted in said second control mode to control the engine so as to reduce the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft before the reengagement of the clutch takes place.

2. A system according to claim 1 , characterized in that the engine control means (12) is adapted in the second control mode to control the engine so as to make the rotational speed of the engine output shaft assume a desired value before the reengagement of the clutch takes place, said desired value representing either the prevailing rotational speed of the gearbox input shaft or an assumed value of the prevailing rotational speed of the gearbox input shaft.

3. A system according to claim 2, characterized in that the desired value is a calculated or measured value of the prevailing rotational speed of the gearbox input shaft.

4. A system according to any of claims 1-3, characterized in that the engine control means (12) is adapted, in the second control mode, to control the engine in such a manner that the rotational speed of the engine output shaft essentially corresponds to the rotational speed of the gearbox input shaft at the moment when the reengagement of the clutch takes place.

5. A system according to claim 2, characterized in that the desired value essentially corresponds to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14).

6. A system according to claim 2, characterized in that the desired value is set depending on the position of a split gear switch of the vehicle gear shift lever at the moment when the movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14) and the position of the split gear switch at the moment when the movement of the clutch lever in the clutch reengaging direction is sensed by the sensing means (14).

7. A system according to claim 6, characterized in that the desired value, if it is established that the position of the split gear switch has been changed after the last suspension of the first control mode, is set to a value corresponding to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14) minus a predetermined value, preferably in the order of 100-400 rpm, if the new position of the split gear switch represents a gear change up, and plus a predetermined value, preferably in the order of 100-400 rpm, if the new position of the split gear switch represents a gear change down.

8. A system according to claim 7, characterized in that the desired value, if it is established that the position of the split gear switch has not been changed after the last suspension of the first control mode, is set to essentially correspond to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14).

9. A system according to any of claims 1-8, characterized in that the sensing means (14) is adapted to sense the prevailing manoeuvring position of the clutch lever as well as the velocity at which the clutch lever is moved.

10. A system according to claim 9, characterized in that the system comprises calculating means (16) for calculating, based on information from the sensing means (14) as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the reengagement of the clutch will take place, the engine control means (12) being adapted to take information from the calculating means (16) as to said moment into account during the second control mode.

11. A system according to any of claims 1-10, characterized in that the engine control means (12) is adapted to resume the first control mode on the reengagement of the clutch when having operated according to the second control mode.

12. A system according to claim 11 , characterized in that the engine control means (12) is adapted to interrupt the first control mode if the rotational speed of the engine exceeds a predetermined limit value after the reengagement of the clutch.

13. A system according to any of claims 1-12, characterized in that the engine control means (12) is adapted not to resume the first control mode if it has been established that a brake function has been activated after the last suspension of the first control mode.

14. A system according to any of claims 1-13, characterized in that the system comprises time measuring means (15) for measuring the time elapsed since the last suspension of the first control mode, and that the engine control means (12) is adapted not to resume the first control mode if the elapsed time exceeds a predetermined limit at the moment when the movement of the clutch lever in the clutch reengaging direction is sensed by the sensing means (14).

15. A system according to any of claims 1-14, characterized in that the system comprises enabling means (17) for enabling and disabling the second control mode at the choice of the vehicle driver.

16. A system according to any of claims 1-15, characterized in that the engine control means (12), after having suspended the first control mode on the detection by the sensing means (14) of a movement of the clutch lever in the clutch disengaging direction, is adapted to start operating according to a third control mode, the engine control means (12) being adapted in said third control mode to control the engine so as to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place.

17. A system according to claim 16 in combination with claim 9, characterized in that the system comprises calculating means (16) for calculating, based on information from the sensing means (14) as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the complete disengagement of the clutch will take place, the engine control means (12) being adapted to take information from the calculating means (16) as to said moment into account during the third control mode.

18. A method for controlling the operation of a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox, the method comprising the steps of:

- determining or receiving a set value representing a desired vehicle speed;

- determining or receiving a value representing the actual vehicle speed;

- determining or receiving values representing manoeuvring movements of the vehicle clutch lever;

- controlling the engine, in a first control mode, in dependence on the values as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed;

- suspending the first control mode when a movement of the clutch lever in the clutch disengaging direction is established;

- determining whether or not to resume the first control mode on clutch reengagement; and

- when a movement of the clutch lever in the clutch reengaging direction is established and on condition that it has been established that the first control mode is to be resumed on clutch reengagement, controlling the engine according to a second control mode, in which the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft is reduced before the reengagement of the clutch takes place.

19. A method according to claim 18, characterized in that the rotational speed of the engine output shaft in the second control mode is made to assume a desired value before the reengagement of the clutch takes place, said desired value representing either the prevailing rotational speed of the gearbox input shaft or an assumed value of the prevailing rotational speed of the gearbox input shaft.

20. A method according to claim 19, characterized in that the desired value is a calculated or measured value of the prevailing rotational speed of the gearbox input shaft.

21. A method according to any of claims 18-20, characterized in that the engine in the second control mode is controlled in such a manner that the rotational speed of the engine output shaft essentially corresponds to the rotational speed of the gearbox input shaft at the moment when the reengagement of the clutch takes place.

22. A method according to claim 19, characterized in that the desired value essentially corresponds to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is established.

23. A method according to claim 19, characterized in that the desired value is set depending on the position of a split gear switch of the vehicle gear shift lever at the moment when the movement of the clutch lever in the clutch disengaging direction is established and the position of the split gear switch at the moment when the movement of the clutch lever in the clutch reengaging direction is established.

24. A method according to claim 23, characterized in that the desired value, if it is established that the position of the split gear switch has been changed after the last suspension of the first control mode, is set to a value corresponding to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is established minus a predetermined value, preferably in the order of 100-400 rpm, if the new position of the split gear switch represents a gear change up, and plus a predetermined value, preferably in the order of 100-400 rpm, if the new position of the split gear switch represents a gear change down.

25. A method according to claim 24, characterized in that the desired value, if it is established that the position of the split gear switch has not been changed after the last suspension of the first control mode, is set to essentially correspond to the rotational speed of the gearbox input shaft prevailing at the moment when the movement of the clutch lever in the clutch disengaging direction is established.

26. A method according to any of claims 18-25, characterized in that values representing the prevailing manoeuvring position of the clutch lever as well as the velocity at which the clutch lever is moved are determined or received.

27. A method according to claim 26, characterized in that it is calculated, based on information as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the reengagement of the clutch will take place, and that the information as to said moment is taken into account during the second control mode.

28. A method according to any of claims 18-27, characterized in that the first control mode is resumed on the reengagement of the clutch when the engine has been controlled according to the second control mode.

29. A method according to claim 28, characterized in that the first control mode is interrupted if the rotational speed of the engine exceeds a predetermined limit value after the reengagement of the clutch.

30. A method according to any of claims 18-29, characterized in that the first control mode is not resumed if it has been established that a brake function has been activated after the last suspension of the first control mode.

31. A method according to any of claims 18-30, characterized in that the time elapsed since the last suspension of the first control mode is measured, and that the first control mode is not resumed if the elapsed time exceeds a predetermined limit at the moment when the movement of the clutch lever in the clutch reengaging direction is sensed.

32. A method according to any of claims 18-31 , characterized in that the engine, after suspension of the first control mode on the detection of a movement of the clutch lever in the clutch disengaging direction, is controlled according to a third control mode, in which the torque exerted by the engine is reduced in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place.

33. A computer program loadable directly into the internal memory of a computer, which computer program comprises computer program code for causing the computer to;

- determine or receive a set value representing a desired vehicle speed of a vehicle comprising a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox;

- determine or receive a value representing the actual vehicle speed;

- determine or receive values representing manoeuvring movements of the vehicle clutch lever;

- control the engine, in a first control mode, in dependence on the values as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed;

- suspend the first control mode when a movement of the clutch lever in the clutch disengaging direction is established;

- determine whether or not to resume the first control mode on clutch reengagement; and

- when a movement of the clutch lever in the clutch reengaging direction is established and on condition that it has been established that the first control mode is to be resumed on clutch reengagement, control the engine according to a second control mode, in which the difference between the rotational speed of the engine output shaft and the rotational speed of the gearbox input shaft is reduced before the reengagement of the clutch takes place.

34. A system for controlling the operation of a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox, the system comprising:

- speed setting means (11) for setting a desired vehicle speed;

- sensing means (14) for sensing manoeuvring movements of the vehicle clutch lever, characterized in that the engine control means (12) is adapted to suspend the first control mode when a movement of the clutch lever in the clutch disengaging direction is sensed by the sensing means (14) and start operating according to another control mode, here denominated third control mode, the engine control means (12) being adapted in said third control mode to control the engine to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place.

35. A system according to claim 34, characterized in that the sensing means (14) is adapted to sense the prevailing manoeuvring position of the clutch lever as well as the velocity at which the clutch lever is moved.

36. A system according to claim 35, characterized in that the system comprises calculating means (16) for calculating, based on information from the sensing means (14) as to the prevailing manoeuvring position of the clutch lever and the velocity at which the clutch lever is moved, at what moment the complete disengagement of the clutch will take place, the engine control means (12) being adapted to take information from the calculating means (16) as to said moment into account during the third control mode.

37. A method for controlling the operation of a vehicle engine, the output shaft of which being connected to driving wheels of the vehicle via a clutch and a gearbox, the method comprising the steps of:

- determining or receiving a set value representing a desired vehicle speed;

- determining or receiving a value representing the actual vehicle speed;

- controlling the engine, in a first control mode, in dependence on the values as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed; and - suspending the first control mode when a movement of the clutch lever in the clutch disengaging direction is established and then controlling the engine so as to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place.

38. A computer program loadable directly into the internal memory of a computer, which computer program comprises computer program code for causing the computer to:

- determine or receive a value representing the actual vehicle speed;

- control the engine, in a first control mode, in dependence on the values as to the set vehicle speed and the actual vehicle speed so as to keep the actual vehicle speed essentially equal to the set vehicle speed; and

- suspend the first control mode when a movement of the clutch lever in the clutch disengaging direction is established and then control the engine so as to reduce the torque exerted by the engine in such a manner that said torque is essentially down to zero at the moment when the complete disengagement of the clutch takes place.

39. A computer program product comprising a data storage medium readable by an electronic control unit (12; 40), a computer program according to claim 33 or 38 being stored on said data storage medium.

40. An electronic control unit (40) comprising an execution means (41), a memory (43) connected to the execution means and a data storage medium (44) connected to the execution means, a computer program according to claim 33 or 38 being stored on said data storage medium (44).