Method to reduce fuel consumption when driving a vehicle and switching to higher gear, a computer program for the method, a system enabling the method and a vehicle for it

Patent metadata

Field	Value
Publication number	US-9481353-B2
Application number	US-201314410145-A
Country	US
Kind code	B2
Filing date	Jul 4, 2013
Priority date	Jul 5, 2012
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

A method to reduce fuel consumption when driving a vehicle, wherein the vehicle comprises an internal combustion engine, and a gearbox that is settable to a plurality of transmission ratios, and the vehicle is configured to be driven in at least a first mode (M 1 ) and a second mode (M 2 ), wherein, when the vehicle is driven according to the second mode (M 2 ), a reduced fuel consumption is prioritized to a larger extent at the cost of performance compared with when the vehicle is driven according to the first mode (M 1 ). When setting the gearbox from a first transmission ratio to a second transmission ratio lower than the first transmission ratio that is one of the three lowest settable transmission ratios for the gearbox, the method includes comparing a torque (T req ) requested from the internal combustion engine after setting the gearbox to the second transmission ratio with a first torque (T lim1 ), and driving the vehicle according to the second mode (M 2 ) if the request for torque (T req ) from the internal combustion engine is below the first torque (T lim1 ).

First claim

The invention claimed is:

1. A method to reduce fuel consumption of a vehicle, wherein the vehicle comprises an internal combustion engine, and a gearbox that is settable to a plurality of transmission ratios, and the vehicle is configured for being driven in at least a first mode (M 1 ) and a second mode (M 2 ), wherein, in the second mode (M 2 ), a reduced fuel consumption is prioritized to a larger extent at the cost of performance compared with the first mode (M 1 ), the method comprising:
setting the gearbox from a first transmission ratio to a second transmission ratio that is lower than a first transmission ratio and is one of three lowest settable transmission ratios for the gearbox,
comparing a torque (T req ) requested from the internal combustion engine after setting the gearbox to the second transmission ratio with a first torque (T lim1 ), and
driving the vehicle according to the second mode (M 2 ) if the request for torque (T req ) from the internal combustion engine is below the first torque (T lim1 ).

2. The method according to claim 1 , wherein the vehicle is configured to be selectively driven according to the first mode (M 1 ) and the second mode (M 2 ) at the requested torque (T req ).

3. The method according to claim 1 , wherein
driving according to the second mode (M 2 ) constitutes driving with a lower combustion air pressure compared to the combustion air pressure in the first mode (M 1 ).

4. The method according to claim 1 , further comprising predicting the torque (T req ) requested from the internal combustion engine after setting the gearbox to the second transmission ratio, wherein the predicting is before the gearbox has been set to the second transmission ratio.

5. The method according to claim 4 , further comprising estimating the torque (T req ) requested after setting the gearbox to the second transmission ratio by using one or more from a group consisting of:
a cruise control function;
a look ahead cruise control function;
a determination of a request for torque before the setting of the gearbox to the second transmission ratio;
a change over time of a request for torque before the setting of said gearbox to the second transmission ratio.

6. The method according to claim 1 , wherein the first torque (T lim1 ) is a torque in a range of 0-50% of the maximum transmissible torque from the internal combustion engine, seen over a speed range of the engine.

7. The method according to claim 1 , wherein the size of the first torque (T lim1 ) depends on a current train weight of the vehicle.

8. The method according to claim 1 , wherein the size of the first torque (T lim1 ) depends on a ratio between a maximum train weight of the vehicle and a maximum torque transmissible by the internal combustion engine seen over the speed range of the engine, or a maximum transmissible power at a speed, seen over the speed range of the engine, at which maximum power is transmitted.

9. The method according to claim 1 , wherein the lower transmission ratio is the lowest settable transmission ratio for the gearbox.

10. The method according to claim 1 , further including determining whether a speed (v f ) for the vehicle exceeds a first speed (v 0 ), and
driving the vehicle according to the second mode (M 2 ) if the speed (v f ) for the vehicle exceeds the first speed (v 0 ).

11. The method according to claim 10 , wherein the first speed is a speed exceeding a suitable speed (v 0 ) in the range of 70-90 km/h.

12. The method according to claim 1 , wherein the transmission ratio to which the gearbox is set is a low transmission ratio at which the combustion engine speed is below the engine speed at which a torque plateau for the low transmission ratio is reached.

13. The method according to claim 1 , further comprising determining whether a speed (n eng ) of the internal combustion engine after setting to the second transmission ratio is below a first speed (n 0 ), and
driving the vehicle according to the second mode (M 2 ) if the speed (n eng ) of the internal combustion engine is below the first speed (n 0 ).

14. The method according to claim 13 , wherein the first speed (n 0 ) of the internal combustion engine is in the range of 600-1300 rpm.

15. The method according to claim 1 , wherein, in the first mode (M 1 ), an air/fuel ratio for combustion in the internal combustion engine is controlled such that the air/fuel ratio does not fall below a first limit value, and wherein the combustion is also controlled such that a first margin with respect to the first limit value is maintained, and wherein, in the second mode (M 2 ), the first margin with respect to the first limit value is reduced to a second margin being smaller than the first margin.

16. The method according to claim 15 , wherein the first limit value is essentially a minimum air/fuel ratio that is needed from the point of view of combustion.

17. The method according to claim 1 , wherein, at least in the first mode (M 1 ), the combustion air pressure is maintained at a pressure that is higher than what is necessary from the point of view of combustion.

18. The method according to claim 1 , wherein, in the first mode (M 1 ), maintaining a combustion air pressure at a higher value during a first period (t H ) after a reduction of the requested torque from the internal combustion engine compared with maintained combustion air pressure after a reduction of the requested torque from the internal combustion engine in the second mode (M 2 ).

19. The method according to claim 1 , further comprising determining whether conditions for driving the vehicle according to the second mode (M 2 ) are no longer satisfied, and changing the mode for driving the vehicle to the first mode (M 1 ) in response to conditions that do not satisfy conditions for driving the vehicle according to the second mode (M 2 ).

20. A computer program product comprising a program code stored in a non-transitory computer readable medium which causes a computer to perform the method according to claim 1 .

21. A system configured to reduce fuel consumption of a vehicle, wherein the vehicle comprises an internal combustion engine, and a gear box that is settable to a plurality of transmission ratios, and the vehicle is configured for being driven in at least a first mode (M 1 ) and a second mode (M 2 ), wherein, in the second mode (M 2 ), a reduced fuel consumption is prioritized to a larger extent at the cost of performance compared with the first mode (M 1 ), the system comprising:
a control unit that:
a) sets the gearbox from a first
transmission ratio to a second transmission ratio that is lower than the first transmission ratio, and is one of the three lowest settable transmission ratios for the gearbox,
b) compares a torque (T req ) requested from the internal combustion engine after setting the gearbox to the second transmission ratio with a first torque (T lim1 ), and
c) drives the vehicle according to the second mode (M 2 ) if the request for torque (T req ) from the internal combustion engine is below the first torque (T lim1 ).

22. The system according to claim 21 , wherein the internal combustion engine is a diesel engine.

23. A vehicle, characterized in that it comprises a system according to claim 21 .

Assignees

• Scania Cv Ab

Inventors

• Telborn Klas

Classifications

• F16H61/00

  Control functions within {control units of} change-speed- or reversing-gearings for conveying rotary motion {; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing} · CPC title

• B60W10/11

  Stepped gearings · CPC title

• F02D11/105

  characterised by the function converting demand to actuation, e.g. a map indicating relations between an accelerator pedal position and throttle valve opening or target engine torque · CPC title

• F02D23/02 Primary

  the engines being of fuel-injection type · CPC title

• F16H61/0213

  characterised by the method for generating shift signals · CPC title