Start-Stop Device for Bringing About an Automatic Switch-Off And/Or Switch-On Operation of an Internal Combustion Engine of a Motor Vehicle

Abstract

A start-stop device and a corresponding method brings about an automatic switch-off and/or switch-on operation of an automatically switched-off drive machine of a motor vehicle, in particular of a motor vehicle having an automatic transmission. The start-stop device has a switch-off logic, by way of which an automatic switch-off of the drive machine can be brought about in the case of a moving vehicle in accordance with a predefined switch-off operating strategy, and a switch-on logic, by way of which an automatic switch-on of the automatically switched-off drive machine can be brought about in accordance with a predefined switch-on operating strategy. The switch-off operating strategy and/or the switch-on operating strategy are/is configured in a manner which is based on wheel torque.

Claims

1. A start-stop device for bringing about an automatic switch-off and/or switch-on operation of an automatically switched-off drive machine of a motor vehicle, comprising: switch-off logic, by way of which an automatic switch-off of the drive machine is carried out in a case of a moving vehicle in accordance with a predefined switch-off operating strategy; and switch-on logic, by way of which an automatic switch-on of the automatically switched-off drive machine is carried out in accordance with a predefined switch-on operating strategy, wherein at least one of the switch-off operating strategy and the switch-on operating strategy is configured in a manner which is based on wheel torque.

2. The start-stop device according to claim 1, wherein the switch-off operating strategy takes into account present or determinable information relating to: a current or predicted vehicle tractive torque, a current or predicted crawl torque, a current and/or predicted downhill torque, a predicted wheel torque when the drive machine is switched off, and/or a current and/or predicted braking torque, when the decision is made to bring about an automatic switch-off process.

3. The start-stop device according to claim 2, wherein the switch-on operating strategy takes into account present or determinable information relating to: a predicted vehicle tractive torque, a predicted crawl torque when the drive machine is switched on, a current and/or predicted downhill torque, and/or a current and/or predicted braking torque, when the decision is made to bring about an automatic switch-on process.

4. The start-stop device according to claim 3, wherein the switch-on operating strategy is configured to bring about an automatic start of the drive machine when it is established that the current braking torque of the motor vehicle is at least no smaller than a value of a predicted vehicle tractive torque when the drive machine is switched on.

5. The start-stop device according to claim 4, wherein the predicted vehicle tractive torque is determinable based on a predicted crawl torque, wherein the predicted crawl torque is determinable based on a determinable output speed of the transmission, a planned gear to be engaged and/or a planned idling speed of the drive machine.

6. The start-stop device according to claim 4, wherein the predicted vehicle tractive torque is determinable taking into account information relating to a current or predicted slope of the vehicle.

7. The start-stop device according to claim 6, wherein the predicted vehicle tractive torque is determinable taking into account a determinable current and/or predicted downhill torque.

8. The start-stop device according to claim 4, wherein the predicted vehicle tractive torque is determined as follows: determining a current speed of the vehicle or an output speed of the vehicle transmission; determining a virtual turbine speed of a converter arranged between drive and transmission based on the speed of the vehicle or the output speed of the transmission and a planned gear to be engaged; determining a predicted turbine speed, wherein the predicted turbine speed is determined from the virtual turbine speed and taking into account a delay time, which is required for starting the drive machine and for building up traction; determining a predicted crawl torque based on the determined predicted turbine speed and a planned idling speed of the drive machine and optionally taking into account a downhill torque acting on at least one wheel; determining the predicted vehicle tractive torque taking into account the determined predicted crawl torque, the current or predicted downhill torque and a braking torque currently set by the driver.

9. The start-stop device according to claim 1, wherein the motor vehicle has an automatic transmission.

10. A method for bringing about an automatic switch-off and/or switch-on operation of an automatically switched-off drive machine of a motor vehicle having an automatic transmission, the method comprising: bringing about the automatic switch-off of the drive machine when the vehicle is moving according to a predefined switch-off operating strategy; and bringing about an automatic switch-on of the automatically switched-off drive machine according to a predefined switch-on operating strategy, wherein the switch-off operating strategy and/or the switch-on operating strategy is configured in a manner which is based on wheel torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a structure of a start-stop device according to an embodiment of the invention for bringing about an automatic switch-off and/or switch-on process of a drive machine.

[0028] FIG. 2 shows an exemplary structure of a wheel-torque-based switch-on operating strategy according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows in detail a start-stop device SSE, which is adapted, by emitting a signal msa_stopp, to bring about an automatic switch-off process of an internal combustion engine BKM of a motor vehicle with automatic transmission, not shown in detail here, when the motor vehicle is moving. The start-stop device SSE is also adapted, by emitting a signal msa_start, to bring about a switch-on process of the internal combustion engine BKM of the motor vehicle, which has been automatically switched off when the motor vehicle is moving. The internal combustion engine BKM of the motor vehicle not shown in detail here can either be the single drive machine of the motor vehicle or one of at least two drive machines, such as is the case, for example, with hybrid vehicles.

[0030] The start-stop device SSE receives, inter alia, the following signals in order to be able to decide on the time of bringing about an automatic switch-off and/or switch-on of the previously automatically switched off drive machine:

[0031] a speed signal v from the vehicle,

[0032] a brake torque signal MBr,

[0033] a current or predicted downhill torque signal Mhg,

[0034] a signal g, which provides information relating to the gear currently engaged, and

[0035] a transmission signal I of the transmission, and

[0036] a signal dzll relating to the predicted idling speed.

[0037] The start-stop device SSE can be adapted to calculate, taking into account the incoming signals when the drive machine is switched off, based on the wheel torque, a predicted vehicle tractive torque MVor, which would be established when the drive machine BKM was switched off.

[0038] The start-stop device SSE further comprises switch-off logic ABL, by which an automatic switch-off of the drive machine BKM when the vehicle is moving can be brought about in accordance with a predefined switch-off operating strategy and switch-on logic ANL, by which an automatic switch-on of the internal combustion engine BKM, which has been automatically switched off with the vehicle moving, can be brought about in accordance with a predefined, wheel-torque-based switch-on operating strategy.

[0039] The switch-on logic ANL can be configured in such a manner that this determines, taking into account the predicted vehicle tractive torque MVor, whether and when an automatic switch-on of the drive machine should be brought about.

[0040] FIG. 2 shows a possible configuration of the switch-on operating strategy including a wheel-torque-based determination of the predicted crawl torque MKriech, by way of which an automatic starting of the internal combustion engine and a gentle transition into an automatic crawl can be brought about.

[0041] In this case, the output speed DZAbtrieb of the transmission is determined from the speed signal v from the vehicle. Firstly, in a first determination unit E1, a virtual predicted crawl torque (on the level) MKriech is determined from the determined output speed DZAbtrieb, the planned gear g to be engaged, the planned idling speed dzll, and the transmission signal 1 of the transmission. Taking into account the virtual predicted crawl torque MKriech, a determined current or predicted downhill torque Mhg and a determined braking torque MBr actuated by the driver, the actually predicted vehicle tractive torque MVor, which would occur if the drive machine were switched on (and there was no gas pedal actuation) is then determined in a second determination unit E2.

[0042] This predicted vehicle tractive torque MVor is supplied as an input signal to the switch-on logic ANL. The switch-on logic ANL decides on the basis of the vehicle tractive torque MVor or on the basis of the previously determined predicted crawl torque MKriech, the current braking torque MBr, and the downhill torque Mhg, whether to bring about an automatic switch-on process of the drive machine. Thus, an automatic switch-on of the drive machine is brought about by emitting a signal msa_start when the current braking torque MBr is greater than the value of the predicted vehicle tractive torque MVor when the drive machine is switched on.

[0043] By means of the start-stop device proposed here, configured according to the invention, a comfortable, intuitive, and driving-physically appropriate transition from the motor stop state into crawl can be brought about in a simple and cost-effective manner. This also has a positive effect on the CO.sub.2 balance.

[0044] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.