Hybrid car in P0- or P1-configuration

Abstract

A method for controlling a car with a parallel hybrid system comprising at least a combustion engine and an electrical machine in P0- or P1-configuration, with a clutch for connecting the combustion engine's output shaft with at least one drive shaft. Steps include determining a power demand P.sub.d, and decoupling the combustion engine from the drive shaft if the power demand P.sub.d is below a first threshold P.sub.1. Coupling the combustion engine with the drive shaft when the power demand P.sub.d is above the first threshold P.sub.1 provides additional fuel savings when the method further comprises shutting off the combustion engine and providing power to the drive shaft by providing electrical power to the electrical machine to drive the car, when the power demand P.sub.d is between the first threshold P.sub.1 and a second threshold P.sub.2. The second threshold P.sub.2 is greater than the first threshold P.sub.1, i.e. if P.sub.1<P.sub.d<P.sub.2.

Claims

1. A method for controlling a vehicle with a parallel hybrid system that includes at least a combustion engine and an electrical machine in at least one of a P0- and P1 configuration with a clutch for connecting the combustion engine's output shaft with at least one drive shaft, wherein the method comprises: determining a power demand (P.sub.d), decoupling the combustion engine from the at least one drive shaft when the power demand (P.sub.d) is below a first threshold P.sub.1, coupling the combustion engine with the at least one drive shaft when the power demand (P.sub.d) is above the first threshold P.sub.1, shutting off the combustion engine and providing power to the at least one drive shaft by providing electrical power to the electrical machine to drive the vehicle, when the power demand (P.sub.d) is between said first threshold P.sub.1, and a second threshold P2, wherein said second threshold P.sub.2 is greater than the first threshold P.sub.1, i.e. P.sub.1<P.sub.d<P.sub.2.

2. The method of claim 1 wherein the combustion engine is restarted when the power demand (P.sub.d) is greater or equal than the second threshold P.sub.2, i.e. if P.sub.dP.sub.2.

3. The method of claim 1 wherein the second threshold P.sub.2 is a function of a state of charge (SOC) of the vehicle's battery.

4. The method of claim 1 wherein the combustion engine is shut-off when the power demand (P.sub.d) is below the first threshold P.sub.1 and if at the same time a state of charge (SOC) of the vehicle's battery system is above a first SOC threshold (SOC.sub.1).

5. The method of claim 1 wherein when the power demand (P.sub.d) is below the second threshold P.sub.2, the combustion engine is stopped only if at the same time a state of charge of the vehicle's battery is above a first SOC threshold.

6. The method of claim 1 wherein the method further comprises calculating a predictive energy demand value (E.sub.p) and in that the second threshold P.sub.2 is a function of the predictive energy demand value (E.sub.p).

7. The method of claim 6, wherein a predictive energy demand value (E.sub.p) is calculated based on geographical information about an intended or expected route.

8. The method of claim 1 wherein when the power demand (P.sub.d) is below the first threshold and below a negative power threshold (P.sub.ne), i.e. P.sub.d<P.sub.ne<P.sub.1 a clutch is closed to couple at least one wheel with the combustion engine's output shaft which drives the electrical machine to convert kinetic power provided by wheels to the electrical machine into electrical power.

9. A controller for controlling at least a combustion engine and an electrical machine of a vehicle's parallel hybrid system wherein said combustion engine and said electrical machine are in at least one of a P0- and P1-configuration, wherein the controller is configured to: determine a power demand (P.sub.d), provide a signal to a clutch to thereby decouple the combustion engine from at least one drive shaft if the power demand (P.sub.d) is below a first threshold P.sub.1, provide a signal to the clutch to thereby couple the combustion engine with the at least one drive shaft if the power demand is above the first threshold P.sub.1 wherein the controller shuts the combustion engine off and provides power to the at least one drive shaft by providing electrical power to the electrical machine to drive the vehicle when the power demand (P.sub.d) is between said first threshold P.sub.1 and a second threshold P.sub.2, wherein said second threshold P.sub.2 is greater than the first threshold P.sub.1, i.e. P.sub.1<P.sub.d<P.sub.2.

10. The controller of claim 9, wherein the controller is configured: to run the combustion engine when the power demand (P.sub.d) is greater or equal than the second threshold P.sub.2, i.e. if P.sub.dP.sub.2 and/or to close the clutch to thereby couple at least one wheel with the combustion engine's output shaft and to control the electrical machine to convert kinetic power provided by wheels to the electrical machine into electrical power when the power demand (P.sub.d) is below the first threshold and below a negative power threshold (P.sub.ne), i.e. P.sub.d<P.sub.ne<P.sub.1.

11. The controller of claim 9 wherein the controller determines the second threshold P.sub.2 as a function of at least one variable V.sub.j.

12. The controller of claim 9 wherein the controller is configured to shut-off the combustion engine when the power demand (P.sub.d) is below the first threshold P.sub.1 and if at the same time the state of charge (SOC) of the vehicle's battery system is above a first SOC threshold (SOC.sub.1).

13. The controller of claim 9 wherein the controller is configured for comparing the power demand (P.sub.d) with the second threshold P.sub.2 and a state of charge of the vehicle's battery with a first SOC threshold and to stop the engine in case the power demand (P.sub.d) is below the second threshold P.sub.2 and the state of charge is above the first SOC threshold and to run the combustion engine in case the state of charge is below or equal to the first SOC threshold.

14. The controller of claim 9 wherein the controller is further configured to determine a predictive energy demand value (E.sub.r) based on geographical and/or traffic information about an intended or expected route and in that the second threshold P.sub.2 is a function of the predictive energy demand value (E.sub.p).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Reference is now made more particularly to the drawings, which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views.

(2) FIG. 1 shows a mild hybrid system.

(3) FIG. 2 shows a method scheme.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a simplified mild parallel hybrid system in P0- and in P1-configuration: As usual, the vehicle has two front wheels 4 and two rear wheels 5, at least two of them are driven are by a mild parallel hybrid system, briefly hybrid system herein. The hybrid system comprises a combustion engine 10 with a crank shaft 11, which is the output shaft of the combustion engine 10. At least one electrical machine 20 is coupled to the output shaft 11. In the figure two electrical machines are indicated by dashed boxes in the P0 and in the P1 configuration, but only to indicate the P0 and the P1 position. In practice a single electrical machine is sufficient. The P0-position is at the side of the combustion engine 10 that faces away from the clutch 30. The P1-position is the position between the clutch 30 and the combustion engine 20. In the figure as well the P3, P4 and P5 positions are indicated, but only to clarify enumeration of the positions: In the P2-configuration the electrical machine would be coupled to the input shaft of the gear box 35. Integration of the electrical machine into the gear 35 or coupling it to the output shaft of the gear is referred to as P3-configuration. The P4-configuration is to couple the electrical machine to the drive shaft connecting the differential 41 and the wheels 4.

(5) As already apparent from the above, the crank shaft 11 is coupled with a clutch 30 in between to a transmission gear 35. The output shaft of the gear 35 is connected e.g. by a cardan shaft 42, 52 or some other means to at least one differential gear 41, 51, which are connected as usual via drive shafts 40, 50 to the wheels 4, 5. In the figure, the gear 35 is coupled to the front differential 51 and as well to a rear differential 41. But of course the vehicle can only be a two wheel drive car as well, i.e. one of the front and rear differentials 41, 51 and the corresponding drive shafts 40, 50 and connection means 42, 52 for connecting the gear 35 with the corresponding differential 41, 51 can be omitted. A rear wheel drive is obtained, by omitting the parts 50, 51, 52 indicated in dashed lines. Omitting the parts 40, 41, 42 in solid lines provides a front wheel drive.

(6) The car further comprises a controller 8. The controller 8 controls the electrical power being exchanged between the electrical machine 20 and a battery 2 e.g. by control lines 6. For example, the controller 8 can provide the electrical machine 20 with power from the battery to drive the crankshaft 11 via control lines 6 or at least a control signal. Alternatively, the controller 8 may charge the battery with power provided by the electrical machine 20, if the crank shaft 11 drives the electrical machine 20.

(7) The controller 8 further controls the combustion engine 10 as indicated by a further control line 6, i.e. the fuel flow and thus the output power of the combustion engine. The controller 8 is further connected with a clutch 30 by a further control line 6 to close or open it, to thereby connect or disconnect the crank shaft with the gear 35 and thus with the wheels 4, 5.

(8) The controller may have several inputs I.sub.i where i stands for an integer enumerating the input. The input ports may be connected to any kind of sensors, e.g. a battery temperature sensor, an acceleration pedal and/or hand throttle sensor, acceleration sensors. Beyond the input ports may enable the controller to communicate e.g. using a communication bus (e.g. a bidirectional communication bus like CAN, FLEXRAY, . . . ) with other components of the car, e.g. with a navigation system, an electronic stability control system or the like.

(9) The hybrid system is explained with respect to a vehicle having two axles. But of course the vehicle and the invention is not limited to such vehicle. The invention can of course as well be applied to vehicles having any number of axles, e.g. three or more axles. The invention can as well be used in trikes and motor cycles. In the case of a motor cycle the drive shafts, the differential and the cardan shaft are typically replaced by a belt drive, a chain drive or a cardan drive, but this does not affect controlling of the combustion engine and the electrical machine to enable passive and active coasting with hybrid systems in P0- or P1-configuration.

(10) In FIG. 2 a method for controlling a hybrid system in P0- and/or P1-configuration is depicted. In a first step 110 input parameters like a power demand P.sub.d and power thresholds P.sub.1 and P.sub.2 may be determined.

(11) Next the power demand P.sub.d is compared to some thresholds: The power demand P.sub.d is compared to a negative threshold as indicated in box 111, i.e. if P.sub.d<Abs(P.sub.ne). If the condition is met as indicated by 1 for true, the controller may activate the recuperation mode of the hybrid system, by closing the clutch indicated as box 123 and operating the electrical machine 20 in a generator mode indicated as box 146, where it provides electrical power to the battery 2 or some auxiliary systems like e.g. a servo steering, lights, radio, air conditioning, etc. The combustion engine 10 may be switched on (box 135) or off (box 130) depending on the electrical power being provided by the electrical machine if the combustion engine is off. This is indicated as I.sub.re>I.sub.min? (box 113), i.e. the current (or power) due to the recuperation of the kinetic energy is compared to some minimum I.sub.min. If the recuperated current I.sub.re (or power) is above the minimum, the combustion engine can be shut-off 130, if not it can be on 135 to drive the electrical machine as well. In practice this can be implemented e.g. by drawing the required electrical power from the electrical machine and controlling the speed of the vehicle by varying the fuel flow of the combustion engine or activation of the brakes as required.

(12) Continuing the false output of decision box 111, which is indicated by 0 it is tested if the power demand P.sub.d is below a first power threshold P.sub.1. This first threshold is chosen to enable passive coasting, i.e. the clutch is opened as indicated by box 120. The combustion engine may be stopped or run with low power, e.g. for charging the battery. The latter is indicated by box 115 symbolizing checking if the state of charge SOC is above a minimum value SOC.sub.min, which can be set in step 110 as a function of multiple variables, like e.g. the expected Energy requirement for the next n-seconds or even minutes, battery temperature, available capacity etc. If the condition is met (indicated by 1), the combustion engine can be shut-off. If not it should run and the electrical machine is in generator mode 146 until the condition is met. If the SOC does not require urgent recharging, the electrical machine may be switched off 140 instead (see dashed line). The corresponding decision box has been omitted to reduce the complexity of the scheme.

(13) If the power demand P.sub.d is in between of the first threshold P.sub.1 and a second threshold P.sub.2 being greater P.sub.1, i.e. if P.sub.1<P.sub.d<P.sub.2 is true (indicated as 1 in box 114), the vehicle is configured for active coasting: The clutch is closed as indicated by the connection with box 123 (in any case if P.sub.1<P.sub.d) and the combustion engine is shut-off 130, provided the SOC allows to (see box 117) and the vehicle is driven by the electrical machine only (electrical machine on 143). If the SOC is too low for active coasting, the combustion engine is started to provide the necessary power. The electrical engine may be used in generator mode 146 or switched off 140 (dashed line). The corresponding decision box was omitted to reduce the complexity of the figure.

(14) If the power demand P.sub.d exceeds the second threshold P.sub.2 box 114 provides 0 and the vehicle is to be driven at least by the combustion engine 135, accordingly 15 the clutch is closed 123 (this is the case as box 112 provides 0 and the corresponding output is connected with box 123). The combustion engine's power may be used to charge the battery 146 or to maintain its SOC. Alternatively the electrical machine may be switched off 140 or if the power demand P.sub.d requires and the SOC enables to, it may be switched on 143 as symbolized by box 116. Box 116 is in fact a very complex algorithm including load balancing between the combustion engine and the electrical machine. But this box 116 can be considered as the normal operation mode of prior art mild parallel hybrid systems that are already commercially available. Thus, there is no need explain its operation in detail again.

LIST OF REFERENCE NUMERALS

(15) 2 battery 4 wheels 5 wheels 6 control lines 8 controller 10 combustion engine 11 output shaft I crank shaft 20 electrical machine 30 clutch (at least one) 35 gear I gear/transmission 40 drive shaft 41 differential gear 42 transmission means e.g. cardan shaft 50 drive shaft 51 differential gear 52 transmission means e.g. cardan shaft 110 determining step 111 comparison P.sub.d<Abs(P.sub.ne)? 112 test P.sub.d<P.sub.1? 113 test I.sub.re<I.sub.min? 114 test P.sub.d<P.sub.2? 115 test SOC>SOC.sub.min? 116 standard load balancing routine 117 test SOC>SOC.sub.min? 120 clutch open 123 clutch closed 130 combustion engine off 135 combustion engine on 140 electrical machine off 143 electrical machine in motor mode 146 electrical machine in generator mode P0 position of electrical machine P1 position of electrical machine P2 position of electrical machine in another configuration P3 position of electrical machine in another configuration P4 position of electrical machine in another configuration I.sub.I, I.sub.i, I.sub.n input ports