GB2569352A

GB2569352A - Control system for a hybrid vehicle, vehicle sub-system and vehicle comprising the same, and method of controlling a climate of a cabin of a hybrid vehicle

Info

Publication number: GB2569352A
Application number: GB1720904.0A
Authority: GB
Inventors: Fracchia Riccardo; Kirkman Richard
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-12-14
Filing date: 2017-12-14
Publication date: 2019-06-19
Anticipated expiration: 2037-12-14
Also published as: GB201720904D0; GB2569352B

Abstract

A control system 100, for a hybrid vehicle, comprises a climate controller 101 for controlling climate of a cabin 105 using heat from combustion engine coolant fluid 110, and a powertrain controller 102 for controlling operation of a combustion engine 103 and of an electric motor 104. The climate controller 101 supplies to the powertrain controller 102 information on an ideal temperature 112 of the coolant, a minimum temperature 113 of the coolant and an actual temperature 114 of the coolant. The powertrain controller 102 is configured to control operation of the engine 103 in dependence on the information supplied to it by the climate controller 101. The control system allows the powertrain controller 102 to switch the combustion engine 103 on and off in line with driver-demanded acceleration and in accordance with how close the actual temperature 114 of the coolant is to the minimum temperature of the coolant 113. Reference is also made to a vehicle sub-system, a vehicle and to a method of controlling a climate of the cabin.

Description

CONTROL SYSTEM FOR A HYBRID VEHICLE, VEHICLE SUB-SYSTEM AND VEHICLE COMPRISING THE SAME, AND METHOD OF CONTROLLING A CLIMATE OF A CABIN OF A HYBRID VEHICLE

TECHNICAL FIELD

The present disclosure relates to a control system for a hybrid vehicle, a vehicle sub-system and a vehicle comprising the same, a method of controlling a climate of a cabin of a hybrid vehicle, and a non-transitory computer readable medium bearing a computer program product or program code for executing such a method. More specifically, it relates to such a control system, vehicle sub-system, vehicle, method and computer program product or program code, wherein the hybrid vehicle has a powertrain comprising a combustion engine and an electric traction motor, and wherein during operation, the combustion engine is circulated with coolant fluid.

BACKGROUND

A hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor generally has a cabin for the driver of the vehicle, as well as for any passengers. The combustion engine is circulated with coolant fluid during its operation, and it is common for heat from the coolant fluid to be used for controlling a climate of the cabin of the vehicle. The cabin can be heated using either heat recovered from the combustion engine or heat from an auxiliary electrical heater or heat pump, or a combination of both. With or without the auxiliary electrical heater or heat pump, heat may be recovered from the combustion engine even when the engine is switched off. The electrical heater or heat pump may have a peak power which is insufficient to reach and/or maintain a comfortable cabin temperature on its own under some combinations of environmental and driving conditions when it is possible to drive with the engine switched off. Such a combination of environmental and driving conditions may, for example, be at ambient temperatures below about 5 degrees Celsius in an urban driving cycle, or when the vehicle is travelling at high speeds on a motorway, when wind chill due to the high speed of the vehicle is significant, but the electric traction motor is sufficient to maintain vehicle momentum on its own. In such cases, the combustion engine will therefore be required to run at least intermittently to provide enough heat to reach and/or maintain a comfortable cabin temperature.

In general, the combustion engine may be switched off when the cabin is at a desired temperature, allowing for efficient hybrid operation of the vehicle at such times. However, if the combustion engine is then only switched on based on an estimation of when the actual cabin temperature is about to depart from the desired cabin temperature by too much, then the behaviour of the on-off duty cycle of the combustion engine may be perceived by the driver as unintuitive or disconcerting, who naturally expects the engine to be switched off when the vehicle is stationary and switched on when the vehicle is moving forward. It is also inefficient in its use of energy by running the engine when the vehicle is motionless, just to heat the cabin of the vehicle. For example, the vehicle may drive for a certain distance with the combustion engine switched off, and then if the driver has to stop the vehicle, for example because of a red traffic light or traffic congestion, when the cabin requires heating, the combustion engine may be switched on again, contrary to the driver’s expectations, and with no efficiency to be gained from recovering heat from the engine when the engine is meeting a driving load.

The present invention has been conceived against this background. It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control system for a hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor, wherein during operation, the combustion engine is circulated with coolant fluid, a vehicle sub-system and a vehicle comprising such a control system, a method of controlling a climate of a cabin of a hybrid vehicle, and a non-transitory computer readable medium bearing a computer program product or program code for executing such a method.

According to an aspect of the invention, there is provided a control system for a hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor, wherein during operation of the combustion engine, the combustion engine is circulated with coolant fluid. The control system comprises a climate controller and a powertrain controller. The climate controller is for controlling a climate of a cabin of the vehicle using heat from the coolant fluid. The powertrain controller is for controlling operation of the combustion engine and of the electric traction motor. The climate controller is configured to supply to the powertrain controller information on (a) an ideal temperature of the coolant fluid, (b) a minimum temperature of the coolant fluid, and (c) an actual temperature of the coolant fluid. The powertrain controller is configured to control operation of the combustion engine in dependence on the information supplied to it by the climate controller.

Supplying this information from the climate controller to the powertrain controller allows the powertrain controller to keep the combustion engine switched off for as long as possible when driver-demanded acceleration of the vehicle is low without affecting the thermal comfort of the cabin. On the other hand, the powertrain controller can also run the engine when it is most expected by the driver of the vehicle and also when it is most energy efficient to do so, in other words, when the combustion engine can fulfil a higher driver-demanded acceleration and the load on the combustion engine generates excess heat which can therefore be used to heat the cabin. It also allows fuel efficiency benefits to be gained from hybrid operation of the vehicle by keeping the engine switched off at low or nil driverdemanded acceleration.

Furthermore, if the vehicle also comprises an auxiliary electrical heater or heat pump, a high load on the auxiliary heater or heat pump can be avoided in driving conditions in which the thermal comfort of the cabin cannot be maintained without switching the engine on. Thus in such circumstances, the electrical power of the auxiliary heater or heat pump can be used more efficiently, and the amount of waste heat from the combustion engine lost to the vehicle’s environment can be reduced.

In some embodiments, the climate controller may be configured to determine the ideal temperature of the coolant fluid and the minimum temperature of the coolant fluid from a target temperature for an air vent for admitting to the cabin air which has been warmed using heat from the coolant fluid.

The powertrain controller may be configured to run the combustion engine in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature, when the actual temperature of the coolant fluid lies between a minimum temperature of the coolant fluid and an ideal temperature of the coolant fluid.

If so, the powertrain controller may be configured to run the combustion engine also in dependence on a speed of the vehicle.

The powertrain controller may be configured to determine the driver-demanded acceleration of the vehicle from torque demanded of the powertrain (that is to say, from the combustion engine and the electric traction motor working in any combination) by at least one of an accelerator pedal of the vehicle, a cruise control of the vehicle, and vehicle creep. By “vehicle creep” is meant the tendency of the vehicle to move forwards when the powertrain is idling, even when both the accelerator pedal of the vehicle and a cruise control of the vehicle have zero input.

The powertrain controller may be configured to assign an index to the actual temperature of the coolant fluid which is normalized to 0 when the actual coolant fluid temperature is less than or equal to the minimum coolant fluid temperature, 1 when the actual coolant fluid temperature is equal to or more than the ideal coolant fluid temperature, and to a value between 0 and 1 when the actual temperature of the coolant fluid lies between the minimum coolant fluid temperature and the ideal coolant fluid temperature. If so, the powertrain controller should also be configured to assign a relationship between the value of the index and a decision to start the combustion engine, wherein the relationship depends on the driver-demanded acceleration of the vehicle.

If so, the powertrain controller may be configured to run the combustion engine when the driver-demanded acceleration of the vehicle reaches a predetermined threshold value for a given value of the index.

The value of the threshold may be different when the driver-demanded acceleration is increasing compared to when the driver-demanded acceleration is decreasing. This has the advantage of allowing some hysteresis in the on-off duty cycle of the combustion engine, in order to avoid repeated switching on and off of the combustion engine when the value of the index is close to the predetermined threshold value.

In another aspect, the invention also provides a vehicle sub-system comprising a control system as described herein, a coolant fluid temperature sensor, a fluid pump, a coolant fluidto air-heat exchanger, an air vent temperature sensor, and a cabin air temperature sensor. The coolant fluid temperature sensor is for providing the actual temperature of the coolant fluid to the climate controller. The fluid pump, which is under control of the climate controller, is for circulating the combustion engine with coolant fluid during operation of the combustion engine. The air vent temperature sensor is for providing an actual air vent temperature to the climate controller. The cabin air temperature sensor is for providing an actual cabin air temperature to the climate controller.

The vehicle sub-system may also comprise an electric heater or heat pump, under control of the climate controller, for providing auxiliary heating to the cabin of the vehicle.

In a further aspect, the invention also provides a hybrid vehicle comprising a combustion engine, an electric traction motor, a cabin, and a control system as described herein or a vehicle sub-system as described herein.

According to yet another aspect of the invention, there is provided a method of controlling a climate of a cabin of a hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor. The method comprises circulating the combustion engine with coolant fluid, using heat from the coolant fluid to warm the cabin of the vehicle, and when an actual temperature of the coolant fluid lies between a minimum temperature of the coolant fluid and an ideal temperature of the coolant fluid, running the combustion engine in dependence on driver-demanded acceleration of the vehicle and proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature.

The method may comprise determining whether the actual coolant fluid temperature is less than the minimum coolant fluid temperature, and, if so, running the combustion engine continuously, whereas if not, determining whether the actual coolant fluid temperature is less than the ideal coolant fluid temperature. If so, the method may comprise running the combustion engine in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature, and determining whether the actual coolant fluid temperature is less than the minimum coolant fluid temperature again, whereas if not, switching the engine off.

The method may also comprise, when running the combustion engine continuously, determining whether the actual coolant fluid temperature is equal to or more than the ideal coolant fluid temperature, and if not, continuing to run the combustion engine continuously, whereas if so, switching the engine off. This has the advantage that once the actual coolant fluid temperature has reached the ideal coolant fluid temperature, heat can still be extracted from the warm combustion engine for a useful period of time, even after it has been switched off, in order to maintain the desired cabin temperature. Apart from improving fuel efficiency, this also reduces engine component wear and improves the driver’s perception of the engine’s behaviour by allowing the engine to remain switched off for extended periods, rather than switching rapidly between off and on.

The invention also provides a non-transitory computer readable medium bearing a computer program product or program code for executing a method as described herein.

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

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic perspective view of an embodiment of a hybrid vehicle;

Fig. 2 is a schematic block diagram of an embodiment of a vehicle sub-system;

Fig. 3 is a schematic flow diagram of an embodiment of a method of controlling a climate of a cabin of a hybrid vehicle;

Fig. 4 is a graph representing an example of operation of a known method of controlling a climate of a cabin of a hybrid vehicle; and

Fig. 5 is a graph representing an example of operation of the method of Fig. 3.

DETAILED DESCRIPTION

Fig. 1 shows an embodiment of a hybrid vehicle 1. The hybrid vehicle 1 has a powertrain comprising a combustion engine and an electric traction motor, and a cabin for the driver of the vehicle 1, as well as for any passengers. The combustion engine is circulated with coolant fluid during its operation, and heat from the coolant fluid is used for controlling a climate of the cabin of the vehicle 1.

Fig. 2 schematically shows an embodiment of a vehicle sub-system 10. The vehicle subsystem 10 comprises a control system 100 for a hybrid vehicle, such as that shown in Fig. 1.

Fig. 2 also schematically represents the powertrain of the vehicle, which comprises the combustion engine 103 and the electric traction motor 104, and the cabin 105 of the vehicle. The coolant fluid which is circulated through the combustion engine 103 is denoted in Fig. 2 by reference numeral 110.

The control system 100 comprises a climate controller 101 for controlling the climate of the cabin 105 using heat from the coolant fluid 110, and a powertrain controller 102 for controlling operation of the combustion engine 103 and of the electric traction motor 104. The climate controller 101 is configured to supply to the powertrain controller 102 information on (a) an ideal temperature 112 of the coolant fluid, (b) a minimum temperature 113 of the coolant fluid, and (c) an actual temperature 114 of the coolant fluid. The powertrain controller 102 is configured to control operation of the combustion engine 103 in dependence on the information supplied to it by the climate controller 101.

The vehicle sub-system 10 also comprises a coolant fluid temperature sensor 107, a fluid pump 111, a coolant fluid-to-air heat exchanger 108, an air vent temperature sensor 117, a cabin air temperature sensor 118, and an electric heater or heat pump 106. The coolant fluid temperature sensor 107 is for providing the actual temperature 114 of the coolant fluid 110 to the climate controller 101. The fluid pump 111, which is under control of the climate controller 101, is for circulating the combustion engine 103 with coolant fluid 110 during operation of the combustion engine 103. When the combustion engine 103 is switched on, the fluid pump 111 circulates the coolant fluid 110 round a circuit which includes, but is not necessarily limited to, the elements shown in Fig. 2. For example, the coolant fluid circuit may also include an engine bypass loop. However, when the combustion engine 103 is switched off, the climate controller 101 may still operate the fluid pump 111 to circulate the coolant fluid 110, according to thermal requirements.

An air vent 109 connects the coolant fluid-to-air heat exchanger 108 with the cabin 105. The air vent temperature sensor 117 is for providing an actual air vent temperature 115 to the climate controller 101. The cabin air temperature sensor 118 is for providing an actual cabin air temperature 116 to the climate controller 101. The electric heater or heat pump 106, which is also under control of the climate controller 101, is for providing auxiliary heating to the cabin 105. This auxiliary heating may be required if heat which can be extracted from the coolant fluid 110 by the heat exchanger 108 is not sufficient for the actual cabin air temperature to reach or maintain a target or desired cabin air temperature, for example in very cold environmental conditions and/or at high vehicle speeds.

The climate controller 101 is configured to determine the ideal temperature 112 of the coolant fluid 110 and the minimum temperature 113 of the coolant fluid 110 from a target temperature for the air vent 109 for admitting to the cabin 105 air which has been warmed by the heat exchanger 108 using heat from the coolant fluid 110. The air vent temperature sensor 117 and the cabin air temperature sensor 118 allow the climate controller 101 to determine what target temperature for the air vent 109 to set. The air vent temperature sensor 117 also allows the climate controller 101 to determine when the target temperature for the air vent 109 has been reached.

The powertrain controller 102 is configured to run the combustion engine 103 in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature 114 to the minimum coolant fluid temperature 112, as well as in dependence on the speed of the vehicle, when the actual temperature 114 of the coolant fluid 110 (as measured by the coolant fluid temperature sensor 107) lies between the minimum temperature 112 of the coolant fluid 110 and the ideal temperature 113 of the coolant fluid 110 (both of which are as determined by the climate controller 101). The powertrain controller 102 is also configured to determine the driver-demanded acceleration of the vehicle from torque demanded of the powertrain 103, 104 by one or more of an accelerator pedal of the vehicle, a cruise control of the vehicle, and vehicle creep.

The powertrain controller 102 is configured to assign an index to the actual temperature 114 of the coolant fluid 110. This index is normalized to 0 when the actual coolant fluid temperature 114 is less than or equal to the minimum coolant fluid temperature 112, 1 when the actual coolant fluid temperature 114 is equal to or more than the ideal coolant fluid temperature 113, and to a value between 0 and 1 when the actual temperature 114 of the coolant fluid 110 lies between the minimum coolant fluid temperature 112 and the ideal coolant fluid temperature 113. The powertrain controller 102 is also configured to assign a relationship between the value of the index and a decision to start the combustion engine 103. This relationship depends on the driver-demanded acceleration of the vehicle. The relationship may be determined, for example, by a predetermined look-up against the value of the index to give a threshold value for a given value of the index, above which the engine will be switched on or below which the engine will be switched off.

The powertrain controller 102 is therefore configured to run the combustion engine 103 when the driver-demanded acceleration of the vehicle reaches the predetermined threshold value for a given value of the index. The value of the threshold is different when the driverdemanded acceleration is increasing compared to when the driver-demanded acceleration is decreasing. This has the advantage of allowing some hysteresis to be included in the on-off duty cycle of the combustion engine 103 to avoid repeated switching on and off of the combustion engine 103 when the value of the index is close to the predetermined threshold value. The behaviour of the powertrain controller 102 during operation of the control system 110 as a result of these configurations of the powertrain controller 102 will become more apparent from the detailed description given below of an example of its operation.

Fig. 3 is a flow diagram which shows an embodiment of a method 200 of controlling a climate of a cabin of a hybrid vehicle, using a control system such as that shown in Fig. 2. The method 200 comprises circulating the combustion engine 103 with coolant fluid 110, using heat from the coolant fluid 110 to warm the cabin 105 of the vehicle, and, when an actual temperature, T, of the coolant fluid 110 lies between a minimum temperature, T_mn, of the coolant fluid 110 and an ideal temperature, T_ideai, of the coolant fluid 110, running the combustion engine 103 in dependence on driver-demanded acceleration of the vehicle and proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min. This conditional running of the engine is represented in Fig. 3 by box 205.

In more detail, the method 200 starts at box 201. No engine run request is issued to the engine 103 by the powertrain controller 102 in box 202. In box 203, the powertrain controller 102 determines whether the actual coolant fluid temperature, T, is less than the minimum coolant fluid temperature, T_min. If so, the powertrain controller 102 runs the combustion engine 103 continuously, as represented in Fig. 3 by box 206. If not, however, the powertrain controller 102 next determines in box 204 whether the actual coolant fluid temperature, T, is less than the ideal coolant fluid temperature, T_idea|. If so, in box 205, the powertrain controller 102 runs the combustion engine 103 in dependence on driver-demanded acceleration of the vehicle and proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min. When running the engine 103 in this conditional manner, the powertrain controller 102 also determines whether the actual coolant fluid temperature, T, is less than the minimum coolant fluid temperature, T_min, by returning to box 203 again. If, on the other hand, the powertrain controller 102 determines in box 204 that the actual coolant fluid temperature, T, is not less than the ideal coolant fluid temperature, T_ideai, the powertrain controller 102 instead switches the engine 103 off by returning to box 202.

When the engine 103 is run continuously by the powertrain controller 102 in box 206, the powertrain controller 102 also determines in box 207 whether the actual coolant fluid temperature, T, is equal to or more than the ideal coolant fluid temperature, T_idea|. If not, the powertrain controller 102 continues to run the combustion engine 103 continuously by returning to box 206. If so, however, the powertrain controller 102 instead switches the engine 103 off by returning to box 202.

An example of the method of Fig. 3 in operation will be described below in greater detail with reference to Fig. 5.

Figs. 4 and 5, which can be compared and contrasted with each other, respectively represent an example of a known method of controlling a climate of a cabin of a hybrid vehicle, when the method is in operation, and an example of the method of the invention when in operation. In both Figs. 4 and 5, time, t, is plotted on the x-axis or abscissa, and three different things are plotted on the y-axis or ordinate, as follows. A combustion engine duty cycle, switching between engine-off and engine-on, is plotted at the top of the ordinate in Figs. 4 and 5, vehicle speed is plotted in the middle of the ordinate in Figs. 4 and 5, and several different temperatures are plotted at the bottom of the ordinate in Figs. 4 and 5. These different temperatures are represented in Figs. 4 and 5 as follows. The dotted line represents a desired or target cabin temperature, the line of alternating short and long dashes represents the actual cabin temperature (for example, as measured by the cabin temperature sensor 118), the line of short dashes represents the ideal coolant fluid temperature, T_ideai, the line of two dots alternating with short dashes represents the minimum coolant fluid temperature, T_min, and the solid line represents the actual coolant fluid temperature, T (for example, as measured by the coolant fluid temperature sensor 107).

As may be seen by comparing the vehicle speeds in Figs. 4 and 5, the drive cycle of the vehicle is the same in both cases, therefore allowing the different behaviours of the combustion engine duty cycle and the various different temperatures in each case to be compared fairly with each other as well. By way of example, the drive cycle of the vehicle is a typical urban drive cycle.

Referring firstly to Fig. 4, it may be seen from the graph of vehicle speed that the vehicle starts from stationary at time t₀, increases its speed steadily to a first cruising speed, then increases its speed steadily again to a second cruising speed until time ti. During this time, the combustion engine remains on and both the actual cabin temperature and the coolant fluid temperature rise until the desired cabin temperature has been met. At this time t_1;therefore, the engine switches off because the desired cabin temperature has been met. Between this time L and time t₂, the combustion engine remains off and the variations in vehicle speed are instead provided by the electric traction motor of the hybrid vehicle. The actual coolant fluid temperature therefore drops steadily until time t₂, when the engine starts again because the actual cabin temperature has also dropped below its target temperature. The combustion engine therefore remains on again until time t₃, when the actual cabin temperature has increased back up to its target temperature once again. On the other hand, in the meantime, between time t₂ and time t₃, the vehicle speed has fallen to zero once again, and the vehicle is therefore standing motionless with the engine running. Thus it may be seen from Fig. 4 that the duty cycle of the engine, i.e. whether the engine is switched on or off, as represented by the topmost graph in Fig. 4, is uncorrelated with the drive cycle of the vehicle, as represented by the middle graph in Fig. 4. This is both disconcerting for the driver of the vehicle, who naturally expects the engine to be switched off when the vehicle is stationary and switched on when the vehicle is moving forward, and is also inefficient in its use of energy by running the engine when the vehicle is motionless, just to heat the cabin of the vehicle.

In contrast, as may be seen from Fig. 5, when the method of the invention is in operation, initially at time t₀, the actual temperature, T, of the coolant fluid is less than the minimum temperature, T_min, of the coolant fluid. Therefore, according to box 203 in Fig. 3, the combustion engine remains on (box 206 of Fig. 3), and both the actual coolant fluid temperature and the actual cabin temperature rise until at time t_1; the actual coolant fluid temperature, T, reaches the ideal coolant fluid temperature, T_idea, (box 207 of Fig. 3). At this time t_b therefore, the combustion engine is switched off (box 202 of Fig. 3). The actual cabin temperature has meanwhile also reached the desired cabin temperature. As may be seen from Fig. 5, both the ideal coolant fluid temperature, T_ideai, and the minimum coolant fluid temperature, T_min, are initially set to higher values by the climate controller 101 as a result of the low initial temperatures of the coolant fluid and of the cabin, and reduce somewhat as the actual coolant fluid and cabin temperatures rise. This helps to pull the actual cabin temperature up more quickly to its target temperature.

The combustion engine remains off until time t₂, when the powertrain controller 102 switches the engine back on again. At this time, the actual coolant fluid temperature, T, lies between the minimum temperature, T_min, of the coolant fluid and the ideal temperature, T_ideai, of the coolant fluid (boxes 203 and 204 of Fig. 3). Whenever this is the case, the powertrain controller 102 runs the combustion engine in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min (box 205 of Fig. 3). As may be seen in Fig. 5, this situation occurs both shortly before time ft and shortly before time t₂. Shortly before time t_1; the combustion engine is run continuously, as described above (box 206 of Fig. 3). However, shortly before time t₂, the combustion engine is instead run conditionally (box 205 of Fig. 3), and the powertrain controller 102 therefore assigns an index to the actual temperature, T, of the coolant fluid, which lies between 0 and 1. Shortly before time t₂, the powertrain controller 102 leaves the engine switched off, even though this index is less than 1, until the driverdemanded acceleration reaches an appropriate level at time t₂. Thus the combustion engine is run in dependence not only on the proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min, but also on the driver-demanded acceleration of the vehicle.

Thereafter, between times t₂ and t₃, the powertrain controller 102 continues to run the combustion engine in dependence on the driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min (box 205 of Fig. 3), switching the engine off (box 202 of Fig. 3) whenever the actual coolant fluid temperature, T, reaches the ideal temperature, T_ideai (box 204 of Fig. 3), until at time t₃, the powertrain controller 102 switches the engine back on again, even though the driver-demanded acceleration is relatively low, because the index of the actual coolant fluid temperature, T, has dropped almost to zero. Thus the on-off duty cycle of the engine, as represented by the topmost graph in Fig. 5, mirrors the drive cycle of the vehicle, as represented by the middle graph in Fig 5, quite closely. This is both reassuring for the driver of the vehicle, who generally experiences the engine to be switched off when the driver-demanded acceleration is low and switched on when the driver-demanded acceleration is high, and is also more efficient in its use of energy, by avoiding running the engine when the vehicle is motionless, merely to heat the cabin of the vehicle.

Whereas in the example of Fig. 5, the duty cycle of the combustion engine is dependent on just the proximity of the actual coolant fluid temperature, T, to the minimum coolant fluid temperature, T_min, and the driver-demanded acceleration of the vehicle, in a further embodiment, it may also be dependent on the speed at which the vehicle is travelling. When the vehicle is travelling at high speed, the cabin loses more heat than when the vehicle is travelling at low speed, increasing the demand for heating the cabin, in order to maintain a constant temperature. Thus the speed of the vehicle may also be taken into account by the powertrain controller 102 when determining when to switch the combustion engine on and off.

For the purposes of this disclosure, it is to be understood that the control systems described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controllers may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controllers or control units to implement the control techniques described herein, including the described methods. The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processors. For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. 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 computerreadable storage medium (e.g., a non-transitory 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 blocks illustrated in Fig. 4 may represent steps in a method and/or sections of code in a computer program. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features, whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

1. A control system for a hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor, wherein during operation, the combustion engine is circulated with coolant fluid, the control system comprising:

a climate controller for controlling a climate of a cabin of the vehicle using heat from the coolant fluid; and a powertrain controller for controlling operation of the combustion engine and of the electric traction motor;

wherein the climate controller is configured to supply to the powertrain controller information on:

an ideal temperature of the coolant fluid;

a minimum temperature of the coolant fluid; and an actual temperature of the coolant fluid;

and the powertrain controller is configured to control operation of the combustion engine in dependence on the information supplied to it by the climate controller.

2. A control system according to claim 1, wherein the climate controller is configured to determine the ideal temperature of the coolant fluid and the minimum temperature of the coolant fluid from a target temperature for an air vent for admitting to the cabin air warmed using heat from the coolant fluid.

3. A control system according to claim 1 or claim 2, wherein the powertrain controller is configured to run the combustion engine in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature, when the actual temperature of the coolant fluid lies between a minimum temperature of the coolant fluid and an ideal temperature of the coolant fluid.

4. A control system according to claim 3, wherein the powertrain controller is configured to run the combustion engine also in dependence on a speed of the vehicle.

5. A control system according to claim 3 or claim 4, wherein the powertrain controller is configured to determine the driver-demanded acceleration of the vehicle from torque demanded of the powertrain by at least one of an accelerator pedal of the vehicle, a cruise control of the vehicle, and vehicle creep.

6. A control system according to any one of claims 3 to 5, wherein the powertrain controller is configured to assign an index to the actual temperature of the coolant fluid which is normalized to:

0 when the actual coolant fluid temperature is less than or equal to the minimum coolant fluid temperature;

1 when the actual coolant fluid temperature is equal to or more than the ideal coolant fluid temperature; and a value between 0 and 1 when the actual temperature of the coolant fluid lies between the minimum coolant fluid temperature and the ideal coolant fluid temperature;

and to assign a relationship between the value of the index and a decision to start the combustion engine, wherein the relationship depends on the driver-demanded acceleration of the vehicle.

7. A control system according to claim 6, wherein the powertrain controller is configured to run the combustion engine when the driver-demanded acceleration of the vehicle reaches a predetermined threshold value for a given value of the index.

8. A control system according to claim 7, wherein the value of the threshold is different when the driver-demanded acceleration is increasing compared to when the driverdemanded acceleration is decreasing.

9. A vehicle sub-system comprising:

a control system according to any one of claims 1 to 8;

a coolant fluid temperature sensor for providing the actual temperature of the coolant fluid to the climate controller;

a fluid pump, under control of the climate controller, for circulating the combustion engine with coolant fluid during operation of the combustion engine;

a coolant fluid-to air-heat exchanger;

an air vent temperature sensor for providing an actual air vent temperature to the climate controller; and a cabin air temperature sensor for providing an actual cabin air temperature to the climate controller.

10. A vehicle sub-system according to claim 9, comprising:

an electric heater or heat pump, under control of the climate controller, for providing auxiliary heating to the cabin of the vehicle.

11. A hybrid vehicle comprising:

a combustion engine;

an electric traction motor;

a cabin; and a control system according to any one of claims 1 to 8 or a vehicle sub-system according to claim 9 or claim 10.

12. A method of controlling a climate of a cabin of a hybrid vehicle having a powertrain comprising a combustion engine and an electric traction motor, the method comprising:

circulating the combustion engine with coolant fluid;

using heat from the coolant fluid to warm the cabin of the vehicle; and when an actual temperature of the coolant fluid lies between a minimum temperature of the coolant fluid and an ideal temperature of the coolant fluid, running the combustion engine in dependence on driver-demanded acceleration of the vehicle and proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature.

13. A method according to claim 12, comprising:

determining whether the actual coolant fluid temperature is less than the minimum coolant fluid temperature;

if so, running the combustion engine continuously; whereas if not, determining whether the actual coolant fluid temperature is less than the ideal coolant fluid temperature;

if so, running the combustion engine in dependence on driver-demanded acceleration of the vehicle and the proximity of the actual coolant fluid temperature to the minimum coolant fluid temperature, and determining whether the actual coolant fluid temperature is less than the minimum coolant fluid temperature again; whereas if not, switching the engine off.

14. A method according to claim 13, comprising:

when running the combustion engine continuously, determining whether the actual coolant fluid temperature is equal to or more than the ideal coolant fluid temperature;

if not, continuing to run the combustion engine continuously; whereas if so, switching the engine off.

15. A non-transitory computer readable medium bearing a computer program product or program code for executing a method according to any one of claims 12 to 14.