GB2427656A

GB2427656A - Apparatus for controlling engine shutdown

Info

Publication number: GB2427656A
Application number: GB0513198A
Authority: GB
Inventors: Themi Petridis; Don Kees; Steve Mcgonigle
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-06-29
Filing date: 2005-06-29
Publication date: 2007-01-03
Anticipated expiration: 2025-06-29
Also published as: DE102006028334A1; GB2427656B; GB0513198D0; DE102006028334B4

Abstract

An apparatus for controlling the shutdown of an internal combustion engine 10. The apparatus comprises an electronic control unit and resistive load 20. The resistive load is switched to connect to an electrical generator 13 connected to the engine 10 when the engine is to be shutdown so as to apply a braking force to the engine and reduce the time taken to bring the engine to a stopped state. The apparatus may further disconnect the load when the engine is rotating below a predetermined speed. The electronic control unit may also control a fuel supply and spark supply to the engine. The resistive load may be a front or rear screen heating element, a seat warming element, a cylinder block heater, a cabin heater or a catalytic converter heater.

Description

AN APPARATUS AND METHOD FOR CONTROLLING ENGINE SHUTDOWN

This invention relates to internal combustion engines and in particular to an apparatus and method for controlling the shutdown of such an engine.

It is known that during shutdown of an internal combustion engine from an operating state the engine will pass through several resonant frequencies which will cause vibration of the engine which can be felt by a user of the motor vehicle through the seat upon which they are seated and induce noise audible to a user of a motor vehicle to which the engine is fitted.

Although engine shutdown is not a significant problem with a conventional motor vehicle because it does not occur very frequently it is a greater problem if the engine is used in a motor vehicle having a stop-start system. Stop- start systems automatically stop the engine whenever it is determined that there is an opportunity to do so in order to improve fuel consumption and reduce emissions from the engine or, in the case of a hybrid vehicle, when it is determined that it is preferential to switch from the internal combustion engine to an electric motor for motive power. Therefore in the case of a motor vehicle fitted with a stop-start system the internal combustion engine may be shutdown several times during even a relatively short journey and the vibrations produced during shutdown then become a more significant problem. This is particularly the case because the shutdowns are performed automatically and not in response to a direct action of the motor vehicle driver.

It is an object of this invention to provide an improved apparatus and method for controlling the shutdown of an internal combustion engine.

According to a first aspect of the invention there is provided an apparatus for controlling the shutdown of an internal combustion engine comprising an electrical generator driven by the engine, a resistive load connected to the electrical generator, an electronic control unit and an electronically controlled switch connected to and controlled by the electronic control unit to selectively connect and disconnect the resistive load to the electrical generator wherein the electronic control unit is operable to move the electronically controlled switch to an on position so as to connect the resistive load to the electrical generator during engine shutdown so as to increase the rate of deceleration of the engine.

The electronic control unit may be operable to move the electronically controlled switch to an off position when the engine is determined to be rotating below a predetermined rotational speed threshold.

The electrical control unit may be also operable to control one or more engine parameters used to cause shutdown of the engine.

The one or more engine parameters may include a fuel supply to the engine and a spark supply to the engine.

The electrical generator may be driven by a flexible drive from the engine and is one of a dynamo, an alternator and an integrated startergenerator.

The resistive load may be one or more resistive loads selected from a front screen heating element, a rear screen heating element, a seat warming element, a cylinder block heater, an electric cabin heater and a catalytic converter heater.

A manual switch may be provided to permit a user to independently switch on and off each respective resistive load independently of the position of the electronically controlled switch.

The electronically controlled switch may be arranged so as to be able to connect the respective resistive load to the electrical generator when it is required to slow the engine during shutdown irrespective of the position of the manual switch.

A respective electronically controlled switch may be connected in parallel to each manual switch.

The electrical generator may be a starter-generator driven by a flexible belt drive from a crankshaft of the engine and the starter generator is controlled by the electronic control unit to rotate the crankshaft of the engine when it is required to restart the engine from a stopped state.

According to a second aspect of the invention there is provided a motor vehicle having an apparatus in accordance with said first aspect of the invention.

According to a third aspect of the invention there is provided a method for controlling the shutdown of an internal combustion engine having an electrical generator driven by the engine and a resistive load selectively connectable to the generator wherein the method comprises determining whether the engine is to be shutdown and, when it is determined that the engine is to be shutdown, connecting the resistive load to the electrical generator so as to increase the rate of deceleration of the engine during shutdown.

The method may further comprise determining whether the rotational speed of the engine is below a predetermined rotational speed threshold and, if the rotational speed of the engine is below the predetermined threshold, disconnecting the resistive load from the electrical generator.

The method may further comprise disconnecting the resistive load from the electrical generator if, during an engine shutdown, an input is received from a user of the engine indicating that the engine is to be immediately restarted.

The electrical generator may be driveably connected by a flexible drive to the engine and may be one of a dynamo, an alternator and an integrated starter-generator.

The electrical generator may be a starter-generator driveably connected by a flexible belt drive to a crankshaft of the engine and the method further comprises energising the starter-generator to rotate the crankshaft of the engine when it is determined that the engine is not rotating and it is required to restart the engine.

The invention will now be described by way of example with reference to the accompanying drawing of which:- Fig.l is a schematic representation of a motor vehicle having an apparatus according to the invention; Fig.la is a modification to the apparatus shown in Fig.l; and Fig.2 is a chart showing the steps used in a method in accordance with the invention for controlling the shutdown of an internal combustion engine.

With reference to Fig.1 there is shown a motor vehicle having an engine 10 driving a multi-speed transmission 11.

An electrical generator in the form of an integrated starter-generator 13 which can drive or be driven by the engine 10 and in this case drives or is driven by a flexible drive in the form of a drive belt or chain drive 14 driveably connected to a crankshaft of the engine 10. The startergenerator 13 is connected to a source of electrical energy in the form of a battery 15 and to a resistive load 20. An electronic control unit 16 is connected to the starter-generator 13, to the engine 10 and to the transmission 11.

The electronic control unit 16 receives several signals from the engine 10 including a signal indicative of the rotational speed of the engine 10 and sends signals to the engine used to control shutdown and start-up of the engine 10. In this case the engine 10 is a spark ignited engine 10 and the signals sent from the electronic control unit are used to control a fuel supply system (not shown) for the engine 10 and an ignition system (not shown) for the engine 10. If the engine were to be a diesel engine then only the fuel supply to the engine would be controlled.

During normal engine running the electronic control unit 16 is operable to control the fuel supplied to the engine 10 and to adjust the ignition system so that sparks are supplied to the engine at the correct timing to produce the desired engine torque.

The electronic control unit 16 is also connected to an electronically controlled switch 21 which is used to connect and disconnect the resistive load 20 to the starter- generator 13. The electronically controlled switch 21 can be of any suitable type capable of switching the current that flows between the starter-generator 13 and the resistive load. The current will depend upon the resistance of the resistive load 20 and the voltage generated by the starter-generator 13 but typically will be in the range of to 50 amps for a 12 volt system. In this case the electronically controlled switch 21 is a relay type device.

During normal engine operation the electronically controlled switch 21 is set to an off position and the resistive load 20 is not connected to the starter-generator 13. When the electronic control unit 16 determines that the engine 10 is to be shut-down it sends a signal to the electronically controlled switch 21 to place it into an on state and thereby connect the resistive load 20 to the starter-generator 13 and also controls the fuel and spark to the engine 10 causing the engine 10 to stop. The determination that the engine 10 is to be stopped or shutdown can be based upon a key-off signal or be based upon a signal from a stop-start system.

Therefore during the shut-down of the engine 10 it is subjected to a braking load from the starter-generator 13 which causes the rotational speed of the engine 10 to decrease more rapidly than it would otherwise do. That is to say, during engine shutdown the rate of deceleration of the engine 10 is greater than it would be if the resistive load 20 is not connected. Although the engine 10 still has to traverse the same resonant frequencies, because of the rate of deceleration, the time spent at or near these resonant frequencies is less and so they are less noticeable to a user of the engine 10.

As the engine 10 decelerates the electronic control unit 16 tests the measured rotational speed against a predetermined rotational speed threshold such as 50 revolutions per minute (RPM) and, when it is determined that the rotational speed has fallen below this threshold, the electronic control unit 16 switches the electronically controlled switch 21 to an off position so that the resistive load 20 is no longer connected to the starter- generator 13. This is done to ensure that if the engine 10 is immediately restarted the resistive load 20 will not be connected to the starter- generator 13. The electronically controlled switch 21 will remain in this off position until the engine 10 is next stopped. It will be appreciated that the predetermined rotational speed threshold can be any convenient rotational speed close to zero RPM.

The engine 10 is restarted by supplying power from the battery 15 to the starter-generator 13 under Lhe control of the electronic control unit 16. This causes the starter- generator 13 to rotate the crankshaft of the engine 10 and at the same time fuel and spark are supplied to the engine 10 from the electronic control unit 16.

Although in the example described the electronic control unit 16 performs several functions including controlling the spark and fuel supply to the engine and energisation of the starter-generator 13 to start the engine it will be appreciated that the electronic control unit 16 could be used to control only the position of the electronically controlled switch 21 and one or more additional electronic control units could be used to control stopping and starting of the engine 10 Although it would be possible to use the battery 15 as the load for the starter- generator 13, this is not a preferred option. This is because, if the battery is already fully charged, it will not accept any more charge and so will not provide the resistive load required.

However, it will be appreciated that the battery 15 could be used on its own or in combination with one or more additional resistive loads provided that a battery state of charge control system is also used to ensure that there is always sufficient free capacity in the battery 15 for it to be used as a resistive load. However, this increases the complexity and cost of the system and requires the battery to be kept at all times in a less than fully charged state.

Although the invention has been described above with respect to an embodiment in which the resistive load is formed by an integrated startergenerator it will be appreciated that it could be equally applied to the use of any other form of electrical generator such as for example an alternator or a dynamo but in these cases a separate starter motor would need to be used to restart the engine.

In a preferred embodiment of the invention the resistive load is not an additional resistive device but is a resistive load device already present on the motor vehicle capable of providing a significant resistive load. Examples include a front screen heating element, a rear screen heating element, a seat warming element, a cylinder block heater, an electric cabin heater or a catalytic converter heater. The selection of resistive load device will naturally depend upon which of these resistive load devices is already fitted to a particular motor vehicle and the desired load required.

It will be appreciated that all of the resistive load devices are passive resistive loads, that is to say, they have no moving parts which could produce noise or vibration when connected to the electrical generator 13. This is important because it would be detrimental to the aim of the 3o invention to introduce further noise and vibration during engine shutdown.

For the purpose of example, if the resistive load 20 is a rear screen heater element then it will be appreciated that this heater element could be switched on with no obvious or detectable effect on the user of the engine 10.

Similarly, if the resistive load were to be the elements used to heat one or more seats of the vehicle then these could be switched on for the short time required to bring the engine to a halt with no discernable increase in seat temperature.

It will be appreciated that more than one of these resistive loads could be used so that, for example, front and rear screen heater elements could be simultaneously connected to the electrical generator to provide the resistive load.

If the resistive load is not a separate resistive load device provided solely for the purpose of braking the engine 10 but is a resistive load device already present on the motor vehicle, then it will be appreciated that a manual switch 25 will also need to be provided to allow the user to switch on and off that resistive load device when required.

In this case, and as shown in Fig.la, it is necessary to arrange the manual switch 25 and the electronically controlled switch 21 30 that they can both control the connection of the resistive load device to a source of electrical energy which in this case is derived directly from the electrical generator 13. As shown in Fig.la the manual switch 25 and the electronically controlled switch 21 are arranged in parallel thereby allowing that the switches 21, 25 to independently control the connection of the resistive load device to the electrical generator 13 and ensuring that the electronically controlled switch 21 can connect the resistive load device (resistive load 20) to the electrical generator 13 irrespective of the position of the manual switch 25.

It will be appreciated that each of the load resistive load devices could be provided with two separate power supplies, a first supply directly from the electrical - 10 - generator 13 controlled by the electronically controlled switch 21 (as shown on Fig.1) and a second supply from an alternate source of electrical power such as the battery 15 controlled by a manual switch. In this case the two switches would not be arranged as shown in Pig.la but would control the flow of power from the separate supplies. In this case, the electronically controlled switch 21 would be operable to switch off the second supply from the battery 15 and connect to the first supply when resistive load braking is required or there could be a separate electronically controlled switch arranged in series with the manual switch to switch off the second supply.

With particular reference to Fig.2 there is shown a method for controlling engine shutdown according to the invention.

The method starts at step 100 with the engine 10 running normally. At step 105 a stop request is generated by a key-off signal or by a signal from a stop-start system.

When the engine stop request is received the electronic control unit 16 is operable to shut-off the engine 10 at step 110 by cutting off the spark and fuel to the engine 10 and at the same time is operable at step 120 to engage the resistive load 20 by placing the electronically controlled switch 21 into an on position. The exact timing of these steps will depend upon the actual engine configuration but in practice there may be a small delay between step 110 and step 120.

The method then proceeds to step 125 where the electronic control unit 16 determines whether the rotational speed of the engine 10 is below a predetermined threshold.

This is achieved by comparing the rotational speed signal from the engine 10 with a predetermined value stored in a - 11 - memory of the electronic control unit 16 representing a speed below which the engine 10 is virtually stationary.

For example the electronic control unit 16 may perform the test "Is S< 50 RPM?" where S' is the measured engine speed in RPM. If the result of the test is yes' then go to step 130 of the method and move the electronically controlled switch 21 to off so as to disconnect resistive load 20 from the starter-generator 13. If the result of the test is no' then maintain the electronically controlled switch 21 in its current position and retest the engine speed by recycling through step 125.

It will be appreciated that S' could be an analogue or digital representation of engine speed and not an actual measurement.

Once the resistive load 20 has been disengaged or disconnected from the starter-generator 13 the method remains in this state until, at step 135, a restart request is generated. The restart request can be from a key-on signal or from a stop-start system.

The method then proceeds to step 140 where the engine is restarted and, in this case, the starter-generator 13 is energised to rotate the crankshaft of the engine 10.

The method then returns to step 100 and cycles back through steps 100 to 130. It will be appreciated that when the engine 10 is not running the method halts at the end of step 130.

Although the invention is particularly advantageous when used on a motor vehicle having a stop-start system it will be appreciated that it has benefit to all internal combustion powered motor vehicles.

- 12 - It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention.

For example, although the invention has been described above in relation to an embodiment in which the resistive load is only switched off when the speed of the engine reaches a predetermined speed, it will be appreciated that the resistive load could also be arranged to be instantly switched off if, during an engine shutdown, an input is received from a driver of the motor vehicle requiring the engine to be restarted. That is to say, if the engine has started to shutdown and the driver of the motor vehicle demonstrates an intent to pull away by means of one or more driver controlled input devices then the electronic control unit will instantly operate the electronically controlled switch so as to switch-off the resistive load.

Claims

- 13 - Claims 1. An apparatus for controlling the shutdown of an internal

combustion engine comprising an electrical generator driven by the engine, a resistive load connected to the electrical generator, an elecLronic control unit and an electronically controlled switch connected to and controlled by the electronic control unit to selectively connect and disconnect the resistive load to the electrical generator, wherein the electronic control unit is operable to move the electronically controlled switch to an on position so as to connect the resistive load to the electrical generator during engine shutdown so as to increase the rate of deceleration of the engine.
2. An apparatus as claimed in claim 1, wherein the electronic control unit is operable to move the electronically controlled switch to an off position when the engine is determined to be rotating below a predetermined rotational speed threshold.
3. An apparatus as claimed in claim 1 or 2, wherein the electrical control unit is also operable to control one or more engine parameters used to cause shutdown of the engine.
4. An apparatus as claimed in claim 3, wherein the one or more engine parameters include a fuel supply to the engine and a spark supply to the engine.
5. An apparatus as claimed in any of claims 1 to 4, wherein the electrical generator is driven by a flexible drive from the engine and is one of a dynamo, an alternator and an integrated starter-generator.
6. An apparatus as claimed in any of claims 1 to 5, wherein the resistive load is one or more resistive loads - 14 - selected from a front screen heating element, a rear screen heating element, a seat warming element, a cylinder block heater, an electric cabin heater and a catalytic converter heater.
7. An apparatus as claimed in claim 6, wherein a manual switch is provided to permit a user to independently switch on and off each respective resistive load independently of the position of the electronically controlled switch.
8. An apparatus as claimed in claim 7, wherein the electronically controlled switch is arranged so as to be able to connect the respective resistive load to the electrical generator when it is required to slow the engine during shutdown irrespective of the position of the manual switch.
9. An apparatus as claimed in claim 7 or 8, wherein a respective electronically controlled switch is connected in parallel to each manual switch.
10. An apparatus as claimed in any of claims 1 to 9, wherein the electrical generator is a starter-generator driven by a flexible belt drive from a crankshaft of the engine and the starter generator is controlled by the electronic control unit to rotate the crankshaft of the engine when it is required to restart the engine from a stopped state.
11. A motor vehicle having an apparatus as claimed in any of claims 1 to 10.
12. A method for controlling the shutdown of an internal combustion engine having an electrical generator driven by the engine and a resistive load selectively connectable to the generator, wherein the method comprises 15 - determining whether the engine is to be shutdown and, when it is determined that the engine is to be shutdown, connecting the resistive load to the electrical generator so as to increase the rate of deceleration of the engine during shutdown.
13. A method for controlling the shutdown of an internal combustion engine substantially as described herein with reference to the accompanying drawing.

13. A method as claimed in claim 12, wherein the method further comprises determining whether the rotational speed of the engine is below a predetermined rotational speed threshold and, if the rotational speed of the engine is below the predetermined threshold, disconnecting the resistive load from the electrical generator.

14. A method as claimed in claim 12 or 13, wherein the method further comprises disconnecting the resistive load from the electrical generator if, during an engine shutdown, an input is received from a user of the engine indicating that the engine is to be immediately restarted.

15. A method as claimed in any of claims 12 to 14, wherein the electrical generator is driveably connected by a flexible drive to the engine and is one of a dynamo, an alternator and an integrated starter-generator.

16. A method as claimed in claim 15, wherein the electrical generator is a starter-generator driveably connected by a flexible belt drive to a crankshaft of the engine and the method further comprises energising the starter-generator to rotate the crankshaft of the engine when it is determined that the engine is not rotating and it is required to restart the engine.

17. An apparatus for controlling the shutdown of an internal combustion engine substantially as described herein with reference to the accompanying drawings.

- 16 - 18. A motor vehicle substantially as described herein with reference to the accompanying drawings.

19. A method for controlling the shutdown of an internal combustion engine substantially as described herein with reference to the accompanying drawings. I-1

Amendments to the claims have been filed as follows 1. An apparatus for controlling the shutdown of an internal combustion engine comprising an electrical generator driven by the engine, a resistive load connected to the electrical generator, an electronic control unit and an electronically controlled switch connected to and controlled by the electronic control unit to selectively connect and disconnect the resistive load to the electrical generator wherein the electronic control unit is operable to move the electronically controlled switch to an on position so as to connect the resistive load to the electrical generator during engine shutdown so as to increase the rate of deceleration of the engine and is operable to move the electronically controlled switch to an off position when the engine is determined to be rotating below a predetermined rotational speed threshold.

2. An apparatus as claimed in claim 1 wherein the electrical generator is driven by a flexible drive from the engine and is one of a dynamo, an alternator and an integrated starter-generator.

3. An apparatus as claimed in claim 1 or in claim 2 wherein the resistive load is one or more resistive loads selected from a front screen heating element, a rear screen heating element, a seat warming element, a cylinder block heater, an electric cabin heater and a catalytic converter heater.

4. An apparatus as claimed in claim 3 wherein a manual switch is provided to permit a user to independently switch on and off each respective resistive load independently of the position of the electronically controlled switch.

205-0284GB Is, 5. An apparatus as claimed in claim 4 wherein the electronically controlled switch is arranged so as to be able to connect the respective resistive load to the electrical generator when it is required to slow the engine during shutdown irrespective of the position of the manual switch.

6. An apparatus as claimed in claim 4 or in claim 5 wherein a respective electronically controlled switch is connected in parallel to each manual switch.

7. An apparatus as claimed in any of claims 1 to 6 wherein the electronic control unit is operable to operate the or each electronically controlled switch to disconnect the resistive load from the electrical generator if, during an engine shutdown, an input is received from a user of the engine indicating that the engine is to be immediately restarted.

8. A motor vehicle having an apparatus as claimed in any of claims 1 to 7.

9. A method for controlling the shutdown of an internal combustion engine having an electrical generator driven by the engine and a resistive load selectively connectable to the generator wherein the method comprises determining whether the engine is to be shutdown and, when it is determined that the engine is to be shutdown, connecting the resistive load to the electrical generator so as to increase the rate of deceleration of the engine during shutdown and determining whether the rotational speed of the engine is below a predetermined rotational speed threshold and, if the rotational speed of the engine is below the predetermined threshold, disconnecting the resistive load from the electrical generator.

205-0284GB 10. A method as claimed in claim 9 wherein the method further comprises disconnecting the resistive load from the electrical generator if, during an engine shutdown, an input is received from a user of the engine indicating that the engine is to be immediately restarted.

11. An apparatus for controlling the shutdown of an internal combustion engine substantially as described herein with reference to the accompanying drawing.

12. A motor vehicle substantially as described herein with reference to the accompanying drawing.