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 or switch-on operation of a drive machine of a motor vehicle, comprising: switch-off logic, by way of which the automatic switch-off operation of the drive machine is carried out in accordance with a predefined switch-off operating strategy when the motor vehicle is moving; and switch-on logic, by way of which the automatic switch-on operation of the 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 based on a wheel torque determined from one or more signals of the motor vehicle and/or a transmission of the motor vehicle; 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 or predicted downhill torque, a predicted wheel torque, and/or a current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-off operation; the switch-on operating strategy takes into account present or determinable information relating to: the predicted vehicle tractive torque, the predicted crawl torque, the current or predicted downhill torque, and/or the current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-on operation; and 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 no smaller than a value of the predicted vehicle tractive torque.

2. The start-stop device according to claim 1, wherein the predicted vehicle tractive torque is determinable based on the predicted crawl torque, and wherein the predicted crawl torque is determinable based on an output speed of the transmission, a planned gear of the transmission to be engaged, or a planned idling speed of the drive machine.

3. The start-stop device according to claim 1, wherein the predicted vehicle tractive torque is determinable based on information relating to a current or predicted slope of the vehicle.

4. The start-stop device according to claim 3, wherein the predicted vehicle tractive torque is determinable based on the current or predicted downhill torque.

5. The start-stop device according to claim 1, wherein the predicted vehicle tractive torque is determined as follows: determining a current speed of the vehicle or an output speed of the transmission; determining a virtual turbine speed of a converter arranged between the drive machine and the transmission based on the current speed of the vehicle or the output speed of the transmission and a planned gear of the transmission to be engaged; determining a predicted turbine speed, wherein the predicted turbine speed is determined from the virtual turbine speed and based on a delay time which is required for starting the drive machine and building up traction; determining the predicted crawl torque based on the predicted turbine speed and a planned idling speed of the drive machine and optionally based on the current or predicted downhill torque acting on at least one wheel of the motor vehicle; and determining the predicted vehicle tractive torque based on the predicted crawl torque, the current or predicted downhill torque, and the current or predicted braking torque of the motor vehicle.

6. The start-stop device according to claim 1, wherein the transmission of the motor vehicle is an automatic transmission.

7. A method for bringing about an automatic switch-off or switch-on operation of a drive machine of a motor vehicle having an automatic transmission, the method comprising: bringing about the automatic switch-off operation of the drive machine according to a predefined switch-off operating strategy when the motor vehicle is moving; and bringing about the automatic switch-on operation of the drive machine according to a predefined switch-on operating strategy, wherein the switch-off operating strategy and/or the switch-on operating strategy is based on a wheel torque determined from one or more signals of the motor vehicle and/or the automatic transmission of the motor vehicle; 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 or predicted downhill torque, a predicted wheel torque, and/or a current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-off operation; the switch-on operating strategy takes into account present or determinable information relating to: the predicted vehicle tractive torque, the predicted crawl torque, the current or predicted downhill torque, and/or the current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-on operation; and 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 no smaller than a value of the predicted vehicle tractive torque.

8. A start-stop device for bringing about an automatic switch-off or switch-on operation of a drive machine of a motor vehicle, comprising: switch-off logic, by way of which the automatic switch-off operation of the drive machine is carried out in accordance with a predefined switch-off operating strategy when the motor vehicle is moving; and switch-on logic, by way of which the automatic switch-on operation of the drive machine is carried out in accordance with a predefined switch-on operating strategy, wherein each of the switch-off operating strategy and the switch-on operating strategy are based on a wheel torque determined from one or more signals of the motor vehicle and/or a transmission of the motor vehicle; 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 or predicted downhill torque, a predicted wheel torque, and/or a current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-off operation; the switch-on operating strategy takes into account present or determinable information relating to: the predicted vehicle tractive torque, the predicted crawl torque, the current or predicted downhill torque, and/or the current or predicted braking torque of the motor vehicle, when a decision is made to bring about the automatic switch-on operation; and 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 no smaller than a value of the predicted vehicle tractive torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

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

(3) FIG. 3 shows a flowchart of a method according to an embodiment of the invention for bringing about an automatic switch-off and/or switch-on process of a drive machine.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows in detail a start-stop device 100, which is adapted, by emitting a stop signal 120, to bring about an automatic switch-off process of an internal combustion engine 105 of a motor vehicle with automatic transmission 135, not shown in detail here, when the motor vehicle is moving. The start-stop device 100 is also adapted, by emitting a start signal 125, to bring about a switch-on process of the internal combustion engine 105 of the motor vehicle, which has been automatically switched off when the motor vehicle is moving. The internal combustion engine 105 of the motor vehicle not shown in detail here can either be the single drive machine 105 of the motor vehicle or one of at least two drive machines 105, such as is the case, for example, with hybrid vehicles.

(5) The start-stop device 100 receives, inter aha, 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 105: a speed signal 140 from the vehicle, a brake torque signal 145, a current or predicted downhill torque signal 150, a gear signal 155, which provides information relating to the gear currently engaged, and a transmission signal 160 of the transmission 135, and an idle speed signal 165 relating to the predicted idling speed.

(6) The start-stop device 100 can be adapted to calculate, taking into account the incoming signals when the drive machine 105 is switched off, based on the wheel torque, a predicted vehicle tractive torque 175, which would be established when the internal combustion engine 105 was switched off.

(7) The start-stop device 100 further comprises switch-off logic 110, by which an automatic switch-off of the internal combustion engine 105 when the vehicle is moving can be brought about in accordance with a predefined switch-off operating strategy and switch-on logic 115, by which an automatic switch-on of the internal combustion engine 105, 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.

(8) The switch-on logic 115 can be configured in such a nrr determines, taking into account the predicted vehicle tractive torque 175, whether and when an automatic switch-on of the drive machine 105 should be brought about.

(9) FIG. 2 shows a possible configuration of the switch-on operating strategy including a wheel-torque-based determination of the predicted crawl torque 170, by way of which an automatic starting of the internal combustion engine 105 and a gentle transition into an automatic crawl can be brought about.

(10) In this case, the output speed 180 of the transmission 135 is determined from the speed signal 140 from the vehicle. Firstly, in a first determination unit 200, a virtual predicted crawl torque (on the level) 170 is determined from the determined output speed 180, the planned gear 155 to be engaged, the planned idling speed 165, and the transmission signal 160 of the transmission 135. Taking into account the virtual predicted crawl torque 170, a determined current or predicted downhill torque 150 and a determined braking torque 145 actuated by the driver, the actually predicted vehicle tractive torque 175, which would occur if the drive machine 105 were switched on (and there was no gas pedal actuation) is then determined in a second determination unit 205.

(11) This predicted vehicle tractive torque 175 is supplied as an input signal to the switch-on logic 115. The switch-on logic 115 decides on the basis of the vehicle tractive torque 175 or on the basis of the previously determined predicted crawl torque 170, the current braking torque 145, and the downhill torque 150, whether to bring about an automatic switch-on process of the drive machine 105. Thus, an automatic switch-on of the drive machine 105 is brought about by emitting a start signal 125 when the current braking torque 145 is greater than the value of the predicted vehicle tractive torque 175 when the drive machine 105 is switched on.

(12) FIG. 3 is a flowchart illustrating a method 300 for determining the predicted crawl torque 170. In 5301, a current speed 140 of the vehicle or an output speed 180 of the vehicle transmission 135 is determined. In 5302, a virtual turbine speed of a converter 130 arranged between drive machine 105 and transmission 135 is determined based on the speed 140 of the vehicle or the output speed 180 of the transmission 135. In 5303, a 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 105 and for building up traction. In 5304, a predicted crawl torque 170 based on the determined predicted virtual turbine speed and the predicted idling speed of the drive machine 105 (after starting) is determined with the aid of the known hydrodynamic converter identification. In 5305, the predicted vehicle tractive torque 175 is determined based on the determined (virtual predicted) predicted crawl torque 170, the determined or known downhill torque 150 and the braking torque 145 predefined or brought about by the driver.

(13) 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.

(14) 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.