GB2570888A

GB2570888A - Control of a vehicle

Info

Publication number: GB2570888A
Application number: GB1801969.5A
Authority: GB
Inventors: James Mcgeoch David; Jerger Rob; Marsden Paul
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-02-07
Filing date: 2018-02-07
Publication date: 2019-08-14
Anticipated expiration: 2038-02-07
Also published as: GB201801969D0; GB2570888B

Abstract

A control system for a vehicle (100, Fig. 4) having an engine 12, a transmission 14, and an electric motor 26, the control system being configured to: receive one or more electrical signals indicative of a vehicle parameter (602, Fig. 6); determine, based on said one or more electrical signals, a requirement to perform an operation of the transmission (14) while the vehicle (100) is in motion and the engine (12) is shut off (604, Fig. 6); and in dependence on determining said requirement: activate the electric motor (26) to increase the rotational speed of the engine (606, Fig. 6); recouple the engine (12) and the transmission (608, Fig. 6); and perform the operation of the transmission (610, Fig. 6); By utilising an electric motor to rotate the engine, then the engine is not required to be restarted in order to enable a gear shift to be achieved; The engine thus does not require the input of fuel and therefore the fuel efficiency of the engine may be increased. A method of controlling a vehicle is also disclosed.

Description

CONTROL OF A VEHICLE

TECHNICAL FIELD

The present disclosure relates to the control of a vehicle. In particular, but not exclusively, the disclosure relates to achieving transmission torque interventions on a vehicle and more specifically a hybrid vehicle. More particularly, the present invention relates to a method of performing a gearshift operation or preventing the disengagement of a clutch in the transmission system of a vehicle while the vehicle is in motion and the engine is shut off. Aspects of the invention relate to a control system, a vehicle and a method.

BACKGROUND

For the purpose of improving fuel economy, it is known to provide an internal combustion engine which may be turned off whilst the vehicle is in motion and the propulsion system is not required to provide propulsive effort (i.e. the driver is not pressing the accelerator pedal). When the engine is stopped, it no longer provides oil pressure to an automatic transmission of the vehicle. In this event it will be understood that the transmission of the vehicle is essentially in 'neutral', so that the road wheels can still rotate, but the engine is stationary. The input shaft to the transmission is also stationary, however some internal gears within the transmission may still be rotating, due to their mechanical connection to the transmission output shaft (which is directly connected to the wheels).

It is desirable to maintain the correct gear for the road speed of the vehicle so as to minimise internal losses and minimise re-engagement time due to not needing to select the correct gear after the engine is re-started and the driver is demanding propulsive effort. It will be appreciated that such a delay would degrade driver perception of the vehicle.

Normal gear selection within an automatic transmission is achieved via an arrangement of friction clutch devices. However, for automatic transmission arrangements containing nonfriction clutches, typically referred to as dog clutches and having interengageable teeth, there are two potential issues:

1. It may not be possible to re-engage a dog clutch if there is tooth-to-tooth contact. If the dog clutch is not rotating, then it will be appreciated that there is nothing to adjust the relative position of the clutch teeth.

2. During the time that the engine of the vehicle is turned off a dog clutch may naturally disengage due to loss of hydraulic pressure within the transmission.

Without other mitigation and to allow either a successful gear shift which involves a dog clutch, or to prevent disengagement of a dog clutch within the transmission, the engine would need to be re-started. This would result in rotation of the input shaft of the transmission and hence cause movement of the dog clutch so that the teeth thereof can move into a fully engaged position. The engine can thereafter be stopped once this action is complete. It will be appreciated however that re-starting the engine for this purpose is fuel inefficient and potentially degrades overall refinement and driver perception of the behaviour of the vehicle.

It is an aim of the invention to overcome the above mentioned issues.

SUMMARY OF THE INVENTION

Aspects of the invention provide a control system, a vehicle and a method as claimed in the appended claims.

According to an aspect of the invention there is provided a control system for a vehicle having an engine, a transmission and an electric motor, the control system being configured to: receive one or more electrical signals indicative of a vehicle parameter; determine, based on said one or more electrical signals, a requirement to perform an operation of the transmission while the vehicle is in motion, the supply of fuel to the engine is ceased, and the engine and the transmission are decoupled; and in dependence on determining said requirement: activate the electric motor to increase the rotational speed of the engine; recouple the engine and the transmission without providing fuel to the engine; and perform the operation of the transmission.

The invention described above provides a control system for performing an operation of the transmission when the engine of the vehicle is shut off. The electric motor is used as an alternative torque source to rotate the engine and transmission and thereby enable an operation of the transmission to be achieved. Rotation of the engine by the electric motor may be achieved either before or after the engine has been coupled to the transmission. By utilising an electric motor to rotate the engine, then the engine is not required to be restarted in order to enable a gear shift to be achieved. The engine thus does not require the input of fuel and therefore the fuel efficiency of the engine may be increased compared to the prior art in which the engine is required to be restarted in order to enable a gear shift to be achieved.

The engine can be said to be shut off if the supply of fuel to the engine is ceased such that the engine is no longer providing positive torque at an output shaft of the engine. It will be appreciated that the engine is still free to rotate when it is shut off.

The control system may comprise one or more controller individually or collectively comprising: means for receiving said one or more electrical signals indicative of a vehicle parameter; means to determine said requirement to perform an operation of the transmission while the vehicle is in motion and the engine is shut off; and means to, in dependence on determining said requirement: activate the electric motor to increase the rotational speed of the engine; recouple the engine and the transmission; and perform the operation of the transmission. In this way the control may be carried out on a single individual electronic controller or the various functions may be carried out on different controllers on the vehicle.

The means for receiving one or more signals indicative of a vehicle parameter may comprise an electronic processor having an electrical input for receiving said one or more signals. The control system may comprise an electronic memory device may be electrically coupled to the electronic processor and have instructions stored therein. The means to determine a requirement to perform an operation of the transmission, and the means to activate the electric motor to increase the rotational speed of the engine, recouple the engine and the transmission, and perform the operation of the transmission may comprise the processor being configured to access the memory device and execute the instructions stored therein such that it is operable to: determine said requirement to perform an operation of the transmission; command said activation of the electric motor to increase the rotational speed of the engine; command said recoupling of the engine and the transmission; and command said performing of the operation of the transmission.

The one or more electrical signals indicative of a vehicle parameter may comprise a signal indicative of vehicle speed and, in dependence on said signal indicative of vehicle speed indicating that the vehicle speed has changed, the controller may output a signal indicative of a requirement to perform a gear shift operation.

In an arrangement, the signal indicative of vehicle speed may indicate that the vehicle speed has decreased. In such an arrangement, the controller may output a signal indicative of a requirement to perform a down shift of the transmission in dependence on the signal indicative of vehicle speed indicating that the vehicle speed has decreased. In the same arrangement, or in an alternative arrangement, the signal indicative of vehicle speed may indicate that the vehicle speed has increased. In such an arrangement, the controller may output a signal indicative of a requirement to perform an up shift of the transmission in dependence on the signal indicative of vehicle speed indicating that the vehicle speed has increased.

The transmission of the vehicle is thus enabled to shift into a higher or lower gear in the event that the speed of the vehicle either increases or decreases while the engine is shut off. The transmission is thus kept in a gear which is appropriate to the speed of the vehicle without requiring the engine of the vehicle to be fuelled and restarted. It will be appreciated that the transmission will therefore be in an appropriate gear to propel the vehicle before the engine is restarted and propulsive effort is demanded from the engine. This has the advantage that the time delay between propulsive effort being demanded from the engine, for example as a result of the driver of the vehicle depressing the accelerator pedal, and the engine delivering propulsive effort is minimised. A downshift may be required when the engine is shut off and the vehicle is decelerating, for example decelerating to a stop. An upshift may be required when the engine is shut off and the vehicle is accelerating, for example coasting downhill.

The one or more electrical signals indicative of a vehicle parameter may alternatively or additionally comprise a signal indicative of engagement of a clutch in the transmission and, in dependence on said signal indicative of engagement of a clutch indicating that the clutch is disengaging due to loss of hydraulic pressure within the transmission, the controller may 4 output a signal indicative of a requirement to perform a gear shift operation. In this case, the controller may output a signal to perform an increase in hydraulic pressure within the transmission for the purpose of re-establishing complete engagement of a clutch of the transmission.

The control system of the present invention may thus be utilised to prevent both partial and complete disengagement of a clutch in the transmission of a vehicle when the engine of the vehicle is shut off. The invention utilises an electric motor to rotate the engine and transmission to increase hydraulic pressure within the system. This in turn urges the clutch into engagement. Rotation of the engine by the electric motor may be achieved either before or after the engine has been coupled to the transmission. By utilising an electric motor to rotate the engine, the engine is not required to be restarted. The engine thus does not require the input of fuel and therefore the fuel efficiency of the engine may increase.

The control system of the present invention may further be configured to determine the completion of said requirement to perform an operation of the transmission and, in dependence on determining the completion of said requirement, deactivate the electric motor; and decouple the engine from the transmission after performing the operation of the transmission.

The control system may further be configured to, in dependence on determining said requirement to perform an operation of the transmission, increase the rotational speed of the engine to between 200 rpm and 1000 rpm. In one embodiment of the invention the control system may be configured to increase the engine speed to 300rpm. In another embodiment of the invention the control system may be configured to increase the engine speed to 400rpm. The control system may be configured to increase the rotational speed of the engine either while the engine is rotating or from rest. The control system may be configured to, in dependence on determining said requirement to perform an operation of the transmission, maintain the increased rotational speed of the engine for between 0.1 seconds and 5 seconds. More specifically, the control system may be configured to maintain the increased rotational speed of the engine for between 0.5 seconds and 1.5 seconds.

It will be appreciated that the rotational speed which the control system is configured to increase the engine to, and the time period for which the control system is configured to maintain said speed, is dependent upon, amongst other factors, the configuration of the transmission.

The control system may comprise an engine and an electric motor.

The electric motor may directly drive a shaft of the engine. In such an embodiment the electric motor may be incorporated into the configuration of the engine. It will be appreciated that internal incorporation of the electric motor may assist in packaging of the engine as a whole.

In an alternative embodiment, the electric motor may indirectly drive a shaft of the engine, for example through a pulley and belt arrangement. The electric motor may thus be provided externally to the engine and may thus be considered an ancillary component of the engine.

The electric motor may comprise part of a belt driven starter generator (BISG) arrangement of the vehicle.

According to another aspect of the invention there is provided a vehicle having a control system as described above.

According to another aspect of the invention there is provided a method of controlling a vehicle having an engine, a transmission and an electric motor, the method comprising: determining, in dependence on one or more electrical signals indicative of a vehicle parameter, a requirement to perform an operation of the transmission while the vehicle is in motion and the engine is shut off; activating the electric motor to increase the rotational speed of the engine; recoupling the engine and the transmission; and performing the operation of the transmission.

The method may further comprise recoupling the engine and the transmission before activating the electric motor. Alternatively, the method may further comprise recoupling the engine and the transmission after activating the electric motor.

The method may further comprise deactivating the electric motor and decoupling the engine from the transmission after performing the operation of the transmission.

According to further aspects of the invention there is provided a computer program that, when run on at least one electronic processor, causes the method as described above to be performed, and a non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of the method described above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic layout of an embodiment of a vehicle engine and transmission system according to the present invention;

Figure 2 shows a schematic layout of an embodiment of a vehicle engine and transmission system according to the present invention;

Figure 3 shows a plot of vehicle speed against time;

Figure 4 shows a side view of a vehicle;

Figure 5 shows a control system according to the present invention; and

Figure 6 shows a flow chart of a method according to the present invention.

DETAILED DESCRIPTION

Referring to Figure 1 there is shown a schematic view of a vehicle engine and transmission system generally designated 10 suitable for a vehicle generally designated 100 as shown in Figure 4. It will be understood that the vehicle 100 is illustrative of a type of vehicle which may incorporate the engine and transmission system 10 of Figure 1. The vehicle 100 includes a combustion engine 12 and a transmission 14. The transmission 14 is connected to the engine 12 through a clutch arrangement 16. The clutch arrangement 16 is connected to the engine 12 and transmission 14 by respective shafts 18,20, where shaft 18 is an output shaft of the engine 12 and shaft 20 is an input shaft of the transmission 14. It will be understood that the clutch arrangement 16 can be manipulated to connect and disconnect the transmission 14 from the engine 12.

The vehicle 100 is further provided with two sets of road wheels 22, 24 comprising a pair of front road wheels 22a, 22b and a pair of rear road wheels 24a, 24b.

In the embodiment shown, the system 10 depicts an all-wheel drive arrangement for a vehicle 100. The system 10 further depicts a front engine layout for a vehicle 100 where the engine 12 and transmission 14 are aligned longitudinally with respect to the front to rear centreline axis D-D of the vehicle 100 in what is known as a north-south configuration. The drive arrangement and engine layout depicted for the vehicle 100 are provided for the purpose of describing an embodiment of the present invention and are not intended to be limiting. It will be appreciated that other drive arrangements may be provided. For example, the vehicle 100 may have solely front or rear wheel drive, or a selective two wheel/all-wheel drive arrangement.

Similarly, it will be understood that position and alignment of the engine 12 and transmission 14 may be different. For example, the engine 12 and transmission may aligned transversely with respect to the front to rear centreline axis D-D of the vehicle 100 in what is known as an east-west configuration. The position of the engine 12 may differ without departing from the scope of the present invention. For example, the vehicle 100 may alternatively have a frontmid, mid or rear engine layout.

The system 10 further includes an alternative torque source operable to rotate the crankshaft of the engine 12. In the embodiment shown, the alternative torque source comprises an electric motor 26 which is associated with the engine 12 and is operable to rotate the engine 12. In one embodiment of the present invention the electric motor 26 may be a belt driven integrated starter generator, hereinafter referred to as a BISG. As will be understood by the skilled addressee, a BISG comprises an electric starter/generator device having an output shaft. The output shaft of the BISG is provided with a pulley which is aligned with a pulley of the engine 12. The BISG pulley and engine pulley are coupled for rotation with one another by a belt. The belt is tensioned such that torque is transmissible between the BISG and the engine 12. In use, the BISG may be operated to rotate the engine 12, for example for the purpose of starting the engine 12. Alternatively, the BISG may be rotated by the engine 12 to generate electrical power. The BISG is typically an external ancillary device to the engine 12 and is located within the engine bay of the vehicle 100.

In an alternative embodiment of the present invention the electric motor 26 may form part of a hybrid drive system of the vehicle 100. The electric motor 26 may, for example be external or internal to the engine 12. The electric motor 26 may be operable to drive the vehicle 100 in either addition to the engine or alternate to the engine 12. The electric motor 26 may, for example, be annular and be positioned so as to, in use, rotate the output shaft 18 of the engine 12.

In an alternative embodiment of the present invention the electric motor 26 may be provided specifically for the purpose of rotating the engine 12 to enable the present invention.

Referring to Figure 5, the engine and transmission system 10 of Figure 1 has one or more controller or control mean generally designated 30 associated therewith. For purposes of this disclosure, it is to be understood that the controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors 304. A vehicle 100 and/or a system thereof may comprise a single control unit or electronic controller 30 or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions 308 are provided which, when executed, cause said controller(s) 30 or control unit(s) to implement the control techniques described herein (including the described method). The set of instructions 308 may be embedded in the controller(s) 30 or in the one or more electronic processors, for example the controller 30 may have an associated or embedded electronic memory device 306, 9 coupled to the one or more electronic processors 304, on which the instructions 308 are stored. In such an arrangement the processor 304 is configured to access the memory 306 and to execute the instructions 308 stored therein so that it is operable to function as herein described.

Alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s) 304. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computerreadable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

The controller 30 has a connection 32 to the alternative torque source which, in the embodiment shown, is an electric motor 26. The connection 32 enables the controller 30 to activate and deactivate the electric motor 26 and thereby increase and decrease the rotational speed of the engine 12 when the engine 12 is shut off and not receiving fuel.

The controller 30 is also provided with a connection 34 to the transmission 14. The connection 34 enables the controller 30 to determine the current gear of the transmission 14 and execute a gear shift within the transmission 14. The gear shift may be an upshift or a downshift.

The controller 30 is also provided with connections 36,38 to the clutch arrangement 16 provided between the engine 12 and the transmission 14. The connections 36,38 enable the controller 30 to both determine the rotational speeds of the shafts 18,20 and operate the clutch arrangement 16 to couple and decouple the engine 12 and transmission 14. The connections 36,38 also enable the controller 30 to determine whether or not the engine 12 is connected or coupled to the transmission 14.

The controller 30 is also provided with means which may comprise one or more electrical input 302 to the processor, for receiving via wired or wireless connections 40 one or more signals indicative of a vehicle parameter. The processor may process the received signals and make the determination on the basis of the received signals of a requirement to perform an operation of the transmission. The signals may originate from one or more vehicle sensors or systems 42 which may, for example, include or comprise a speed sensor. The speed sensor 42 acts as a means for the controller 30 to determine whether the speed of the vehicle 100 is increasing or decreasing.

The controller 30 having the inputs and outputs described above may thus be considered a means for sensing, via the speed sensor 42, a change in the velocity of the vehicle 100, and further a means for determining the need to perform a gear shift operation and a means to perform a gear shift operation.

Figure 2 shows a schematic view of another vehicle engine and transmission system generally designated 50. Features common to the system 10 described with reference to Figure 1 are identified with like reference numerals. As before, the vehicle 100 of Figure 4 is illustrative of a type of vehicle which may incorporate the engine and transmission system 50 of Figure 2.

The system 50 of Figure 2 differs from that of Figure 1 in that the controller or control means 52 does not include a connection to a speed sensor. The system 50 of Figure 2 is further provided with a different connection 54 between the controller 52 and the transmission 14. The connection 54 is provided to enable the controller 52 to sense hydraulic pressure within the transmission 14.

The controller 52 having the inputs and outputs described above may thus be considered means for sensing, via the connection 54 to the transmission 14, a reduction in hydraulic pressure within the transmission 14, and further a means for activating the alternative torque source and clutch arrangement 16 for the purpose of increasing the hydraulic pressure within the transmission 14.

The system 10 of Figure 1, as will be described in greater detail below, enables gear shift operations to be achieved when the engine 12 is shut off. The system 50 of Figure 2, as will be described in greater detail below, prevents the disengagement of a clutch within the 11 transmission 14 due to hydraulic pressure loss when the engine 12 is shut off. More specifically, the system 50 establishes full or complete re-engagement of a clutch within the transmission 14. Complete re-engagement of the clutch may be achieved in instances where the clutch has become either fully or partially disengaged due to hydraulic pressure loss. It will be understood by the skilled addressee that partial disengagement of a clutch occurs where teeth of the clutch are still in contact but there is axial separation between the two sides of the clutch. For full or complete disengagement of the clutch it will be understood that the teeth of the clutch are no longer in contact.

For the purpose of clearly describing the functionality of the systems 10, 50, the systems 10, 50 have been illustrated separately. It will be appreciated however that both systems 10, 50 may be incorporated into a single vehicle 100.

Referring now to Figure 3 there is shown a plot, generally designated 56, of vehicle speed against time for a vehicle 100. Arrow 58 indicates the point at which the engine 12 of the vehicle 100 is shut off while the vehicle 100 is in motion. More specifically, fuelling to the engine 12 is stopped and the transmission 14 and engine 12 are disconnected by the clutch arrangement 16. This may typically be termed an engine stop on the move (SOTM) event.

The plot 56 after the SOTM event 58 illustrates the decrease in the speed of the vehicle 100 to rest 60. Decrease in the speed of the vehicle 100 may, for example, be achieved by one or more of the application of the vehicle brakes, the topography of the surface over which the vehicle 100 is travelling, aerodynamic resistance, kinetic energy recovery arrangements of the vehicle 100 and the inherent rolling resistance within the drive train of the vehicle 100.

At a point between SOTM entry 58 and point A on the plot 56 it is determined that that a downshift is required. Such determination may be made by the controller 30 based upon a decrease in the speed of the vehicle 100 sensed by the speed sensor 42. The controller 30 thereafter activates the alterative torque source to increase the speed of the engine 12. The controller 30 monitors the rotational speed of the engine output shaft 18 and the clutch input shaft 20. When both shafts 18,20 are at suitable speeds the controller 30 operates the clutch arrangement 16 to connect the engine 12 to the transmission 14. Connection of the engine 12 to the transmission 14 increases the hydraulic pressure within the transmission 14 to a point where the controller 30 can perform a downshift. The downshift of the transmission 14 occurs between points A and B on the plot 56. Once the down shift has been completed the 12 controller 30 deactivates the alternative torque source and operates the clutch arrangement 16 to disconnect the engine 12 from the transmission 14.

In one embodiment the alternative torque source may be utilised to rotate the engine 12 at 300 rpm. In another embodiment of the invention the alternative torque source may be utilised to rotate the engine 12 at 400 rpm. It will be understood that other engine speeds are possible, and the engine may be rotated at a speed within the range of 200rpm to lOOOrpm. The engine 12 may be rotated at this speed for approximately one second during which time operation of the clutch arrangement 16 and the downshift of the transmission 14 are achieved. It will be understood that other durations for the rotation of the engine 12 by the alternative torque source may be utilised. In one embodiment the engine 12 may be rotated by the alternative torque source for between 0.1 seconds and 5 seconds. In an alternative embodiment the engine 12 may be rotated by the alternative torque source for between 0.5 seconds and 1.5 seconds.

In an alternative embodiment, rotation of the engine 12 may occur after connection of the engine 12 to the transmission 14 by the clutch arrangement 16.

The operation described above concerns a downshift of the transmission 14 due to the speed of the vehicle 100 decreasing. It will be appreciated that the same method may be employed to accomplish an upshift of the transmission 14 due to an increase in the speed of the vehicle 100.

Point C on the plot 56 illustrates a point where partial disengagement of a clutch within the transmission 14 occurs due to loss of hydraulic pressure within the transmission 14. Such a loss of hydraulic pressure may occur due to the engine 12 being stopped for an extended period while the vehicle 100 is still on the move. In such an instance the partial clutch disengagement may be determined by the controller 52 due to a sensed reduction of pressure within the transmission 14. It will be appreciated that other methods may be used to determine partial disengagement of a clutch, for example a clutch position sensor.

Once the partial disengagement of a clutch within the transmission 14 has been sensed or determined, the controller 52 activates the alterative torque source to increase the speed of the engine 12. The controller 52 monitors the rotational speed of the engine output shaft 18 and the clutch input shaft 20. When both shafts 18,20 are at suitable speeds the controller 13 operates the clutch arrangement 16 to connect the engine 12 to the transmission 14. Connection of the engine 12 to the transmission 14 increases the hydraulic pressure within the transmission 14 which results in re-engagement of the clutch within the transmission 14.

Once re-engagement of the clutch has been completed the controller 30 deactivates the alternative torque source and operates the clutch arrangement 16 to disconnect the engine 12 from the transmission 14. In one embodiment the alternative torque source may be utilised to rotate the engine 12 at 300 rpm. The engine 12 may be rotated at this speed for approximately one second during which time operation of the clutch arrangement 16 and reengagement of the clutch are achieved. Alternative engine speeds and rotation durations, as described above in connection with shifting of the transmission, may be utilised in connection with re-establishing complete re-engagement of a clutch within the transmission.

The present invention allows the engine 12 of a vehicle 100 to remain off and unfuelled whilst performing gear changes to track the best gear for any given speed. This improves refinement and speed of torque response in the engine 12 is restarted and the transmission 14 re-engaged due to a driver request as the transmission 14 is already in the correct gear.

The use of an alternative torque source to provide torque to rotate the engine 12 allows the engine 12 to be kept off for longer and thereby reducing fuel use.

Referring now to Figure 6 a flow chart of the method 600 of the invention is shown. It will be appreciated that the method may be performed by one or more controller as described hereinabove. At 602, one or more signal indicative of vehicle parameters, as described above, are received. At 604, in dependence on one or more electrical signals indicative of a vehicle parameter, a requirement to perform an operation of the transmission 14 while the vehicle is in motion and the engine is shut off is determined. At 606 the electric motor 26 is activated to increase the rotational speed of the engine 12 and at 608 the engine 12 and the transmission 14 are recoupled. It will be appreciated that the engine 12 and the transmission 14 may be recoupled before or after the electric motor 26 is activated. At 610, the operation of the transmission 14 is performed.

The method may additionally include, at 612, deactivating the electric motor 26; and at 614, decoupling the engine 12 and the transmission 14.

Claims

1. A control system for a vehicle having an engine, a transmission and an electric motor, the control system being configured to:

receive one or more electrical signals indicative of a vehicle parameter;

determine, based on said one or more electrical signals, a requirement to perform an operation of the transmission while: the vehicle is in motion, the supply of fuel to the engine is ceased, and the engine and the transmission are decoupled; and in dependence on determining said requirement: activate the electric motor to increase the rotational speed of the engine; recouple the engine and the transmission without providing fuel to the engine; and perform the operation of the transmission.

2. A control system according to claim 1 comprising one or more controller individually or collectively comprising:

means for receiving said one or more electrical signals indicative of a vehicle parameter;

means to determine said requirement to perform an operation of the transmission while the vehicle is in motion and the engine is shut off; and means to, in dependence on determining said requirement: activate the electric motor to increase the rotational speed of the engine; recouple the engine and the transmission; and perform the operation of the transmission.

3. A control system according to claim 2 wherein:

said means for receiving one or more signals indicative of a vehicle parameter comprises an electronic processor having an electrical input for receiving said one or more signals; the system comprising an electronic memory device electrically coupled to the electronic processor and having instructions stored therein; and wherein said means to determine a requirement to perform an operation of the transmission and said means to activate the electric motor to increase the rotational speed of the engine, recouple the engine and the transmission, and perform the operation of the transmission comprise the processor being configured to access the memory device and execute the instructions stored therein such that it is operable to: determine said requirement to perform an operation of the transmission; command said activation of the electric motor to increase the rotational speed of the engine; command said recoupling of the engine and the transmission; and command said performing of the operation of the transmission.

4. A control system according to any preceding claim, wherein said one or more electrical signals indicative of a vehicle parameter comprise a signal indicative of vehicle speed and wherein, in dependence on said signal indicative of vehicle speed indicating that the vehicle speed has changed, the controller outputs a signal indicative of a requirement to perform a gear shift operation.

5. A control system according to claim 4, wherein in dependence on said signal indicative of vehicle speed indicating that the vehicle speed has decreased, the controller outputs a signal indicative of a requirement to perform a gear shift operation.

6. A control system according to claim 5, wherein the operation of the transmission is a down shift of the transmission.

7. A control system according to any of claims 4 to 6, wherein in dependence on said signal indicative of vehicle speed indicating that the vehicle speed has increased, the controller outputs a signal indicative of a requirement to perform a gear shift operation.

8. A control system according to claim 7, wherein the operation of the transmission is an up shift of the transmission.

9. A control system according to any preceding claim, wherein said one or more electrical signals indicative of a vehicle parameter comprise a signal indicative of engagement of a clutch in the transmission and wherein, in dependence on said signal indicative of engagement of a clutch indicating that the clutch is disengaging due to loss of hydraulic pressure within the transmission, the controller outputs a signal indicative of a requirement to perform an operation of the transmission.

10. A control system according to claim 9, wherein the operation of the transmission is an increase in hydraulic pressure within the transmission for the purpose of re-establishing complete engagement of a clutch of the transmission.

11. A control system according to any preceding claim configured to, determine the completion of said requirement to perform an operation of the transmission, and in dependence thereon:

deactivate the electric motor; and decouple the engine from the transmission.

12. A control system according to any preceding claim and further being configured to, in dependence on determining said requirement to perform an operation of the transmission: increase the rotational speed of the engine to between 200 rpm and 1000 rpm.

13. A control system according to any preceding claim and further being configured to, in dependence on determining said requirement to perform an operation of the transmission: increase the rotational speed of the engine from rest to between 200 rpm and 1000 rpm.

14. A control system according to any preceding claim and further being configured to, in dependence on determining said requirement to perform an operation of the transmission: maintain the increased rotational speed of the engine for between 0.5 seconds and 1.5 seconds.

15. A control system according to any preceding claim comprising:

an engine; and an electric motor.

16. A control system according to claim 15, wherein said electric motor directly drives a shaft of the engine.

17. A control system according to claim 15, wherein said electric motor indirectly drives a shaft of the engine.

18. A control system according to claim 17, wherein the electric motor indirectly drives a shaft of the engine through a pulley and belt arrangement.

19. A control system according to claim 18, wherein the electric motor comprises part of a belt driven starter generator arrangement of the vehicle.

20. A vehicle having the control system as claimed in any one of the preceding claims.

21. A method of controlling a vehicle having an engine, a transmission and an electric motor, the method comprising:

determining, in dependence on one or more electrical signals indicative of a vehicle parameter, a requirement to perform an operation of the transmission while the vehicle is in motion and the engine is shut off;

activating the electric motor to increase the rotational speed of the engine;

recoupling the engine and the transmission; and performing the operation of the transmission.

22. A method according to claim 21 comprising recoupling transmission before activating the electric motor. the engine and the

23. A method according to claim 21 comprising recoupling the engine and the

transmission after activating the electric motor.

24. A method according to any of claims 21 to 23 and further comprising:

deactivating the electric motor; and decoupling the engine from the transmission after performing the operation of the transmission.

25. A computer program that, when run on at least one electronic processor, causes the method according to any of claims 21 to 24 to be performed.

26. A non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of the method according to any of claims 21 to 24.