GB2491627A

GB2491627A - An apparatus and method for restarting an engine

Info

Publication number: GB2491627A
Application number: GB1109669.0A
Authority: GB
Inventors: Themi Philemon Petridis
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2011-06-09
Filing date: 2011-06-09
Publication date: 2012-12-12
Anticipated expiration: 2031-06-09
Also published as: CN102817758A; GB201109669D0; CN102817758B; GB2491627B

Abstract

An apparatus and method for restarting an internal combustion engine 2 in which, if a driver change of mind event occurs during an engine shut-down period, a compressed air motor 5 is activated to restart the engine 2 with minimal delay. An electronic control unit (ECU) 9 is used to control the operation of the air motor and to electronically control a valve to control the flow of air to the air motor 5 from an air reservoir 6. The ECU 9 may also control the operation of an electronically controlled clutch 4 driveably positioned between the air motor 5 and the engine 2. The air motor 5 may also be used as a pump to recharge the air reservoir, preferably when the vehicle is braking or when the engine is operating in an overrun condition.

Description

AN APPARATUS AND METHOD FOR RESTARTING AN ENGINE

This invention relates to the starting of an internal combustion engine and, in particular, to the restarting of an engine during an engine shut-down if a driver change of mind event occurs.

For a manual transmission motor vehicle using a Stop-in-Neutral (SIN) stop-start strategy and a conventional starter motor which is not permanently engaged, there are potential problems in the event of a driver change of mind (CoN) . A CoN occurs during the period when the engine is shutting down if the driver triggers a reguest to restart the engine.

With a conventional starter motor a delay will occur between the time the CoN event occurs and the time when the starter motor can be used to restart the engine because a starter pinion of the starter motor cannot be engaged until the engine has come to rest. This delay can result in a kangaroo or jerky start because the engine has not reached sufficient speed before the driver has had time to engage the clutch and reguest torgue or, if the driver is very fast when pressing the clutch pedal, selecting a gear and releasing the clutch pedal, cranking of the engine using the starter motor will be prohibited because the driveline is engaged, thereby stranding the driver.

For a motor vehicle using a Stop-in Gear (SIC) stop-start strategy, exposure to a CoN is even greater due to a reduced time from the initiation of the driver induced start trigger (brake pedal release) to the driver reguesting torque with a closed drive-line. Stop-in-Drive (SID) automatic transmission stop-start applications suffer similar issues, but the result is simply a delay in starting the engine and providing torque for the driver and there is no risk of stall.

According to a first aspect of the invention there is provided an apparatus for restarting an internal combustion engine of a motor vehicle during an engine shut-down due to a driver change of mind wherein the apparatus comprises an air motor driveably connected to the engine and a source of compressed air to selectively drive the air motor when it is reguired to restart the engine.

The apparatus may further comprise an electronic control unit to control the operation of the air motor.

The apparatus may further comprise an electronically controlled valve to control the flow of air to the air motor from the source of compressed air and the electronic control unit is operable to open the electronically controlled valve in order to energise the air motor.

The source of compressed air may be an air reservoir and the air motor may be used as a pump to recharge the air reservoir with compressed air.

The air motor may be operated as a pump when the motor vehicle is determined to be braking.

The air motor may be operated as a pump when the engine is operating in an overrun condition.

The air motor may be driveably connected to the engine via an electronically controlled clutch.

The operation of the electronically controlled clutch is controlled by the electronic control unit.

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

According to a third aspect of the invention there is provided a method for restarting an engine during an engine shut-down due to a driver change of mind wherein the method comprises determining that a driver change of mind has occurred and energising an air motor from a source of compressed air to restart the engine.

The air motor may be driveably connected to the engine via a clutch and the method may further comprise engaging the clutch when the air motor is energised to restart the engine.

The method may further comprise disengaging the clutch when the air motor is not energised.

The source of compressed air may be an air reservoir, the air motor may be selectively operable as a pump and the method may further comprise engaging the clutch when the air motor is operated as a pump in order to recharge the air reservoir.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1 is a block diagram of a motor vehicle and starting apparatus according to a first embodiment of a first aspect of the invention; Fig.2 is a block diagram of a motor vehicle and starting apparatus according to a second embodiment of the first aspect of the invention; and Fig.3 is a high level flow chart showing the basic steps of a method for starting an engine according to a second aspect of the invention.

Referring to Fig.l there is shown a motor vehicle 1 having an internal combustion engine 2 driving a flywheel with starter ring 3 as is well known in the art. The motor vehicle 1 is of a micro hybrid type, that is to say, the engine 2 is controlled by an electronic controller so as to be automatically stopped and restarted when certain predetermined conditions exist in order to improve fuel economy and reduce emissions.

The motor vehicle 1 includes an apparatus to restart the engine 2 while it is still rotating if a driver change of mind event occurs during an engine shut-down. The apparatus comprises an air motor 5 driveably connected to the engine 2 by an electronically controlled clutch 4, a source of compressed air for the air motor 5 in the form of an air reservoir 6, an electronically controlled valve 7 and an electronic control unit 9.

It will be appreciated that the electronic control unit 9 could act as the stop-start controller for the engine 2 or this could be a separate electronic control unit operationally connected to the electronic control unit 9.

Similarly, although the electronic control unit 9 in the example being described controls the operation of the electronically controlled clutch 4 and the electronically controlled valve 7 this need not be the case and separate electronic control units operationally connected together could be provide for these functions.

The air motor 4 is driven by the engine 2 by a direct drive from the flywheel ring gear 3 which drives a shaft connected to an input side of the clutch 4 and an output side of the clutch is connected to a drive shaft of the air motor 5.

The air motor 5 has a first oombined inlet/exhaust 8 which, depending upon whether the air motor 5 is being used as a motor or a pump, allows air to flow respectively out of or into the air motor 5.

The air motor 5 has a second combined inlet/exhaust which, depending upon whether the air motor 5 is being used as a motor or a pump, allows air to flow respectively into or out of the air motor 5 via a passage that is connected to the air reservoir 6 via the electronically controlled valve 7.

The air motor 5 has in this example a turbine (not shown) which is rotated when compressed air flows through the air motor 5 to start the engine 2 or is operable to pump air to the air reservoir 6 in order to recharge it as described in more detail hereinafter. It will be appreciated that the invention is not limited to the use of an air motor having a turbine and that other types of air motor could be used.

An air pressure sensor 10 provides an output to the electronic control unit 9 indicative of the air pressure in the air reservoir 6.

The motor vehicle 1 is further provided with numerous other sensors 11 that are used to sense the operating state of the motor vehicle 1 such as whether it is braking and providing feedback of one or more driver operations such as clutch, brake or accelerator pedal operation.

The electronic control unit 9 is also connected to one or more engine sensors 12 that provide feedback on the operating state of the engine 2 such as engine speed.

Operation of the apparatus is as follows, when it is determined from one of the sensors 11 that a change of mind event (CoN) has occurred during an engine shut-down seguence, the electronic control unit 9 is operable to use the air motor 5 to speed up the engine 2 to a speed at which combustion can take over. This is achieved by opening the electronically controlled valve 7 so as to allow air to flow from the air reservoir 6 into the air motor 5 via the secondary inlet/exhaust through the turbine of the air motor and out via the first inlet/exhaust 8 at the same time or slightly before the electronically controlled valve 7 is opened, the electronic control unit 9 engages the electronically controlled clutch 4 SO as to permit drive to be transmitted from the air motor 5 to the engine 2 in order to speed it up. When the engine 2 starts-up or reaches a speed where effective starting is possible, such as say 500- 700RPM, the electronic control unit 9 disengages the electronically controlled clutch 4 SO as to reduce drag on the engine 2 and closes the electronically controlled valve 7 so as to preserve as much air in the air reservoir as possible.

The electronic control unit 9 is also operable to control the air motor 5 as a pump in order to recharge the air reservoir 6. The electronic control unit 9 engages the electronically controlled clutch 4 SO as to permit drive to be transmitted from the engine 2 to the air motor 5 and opens the electronically controlled valve 7 so as to allow air to flow from the air motor 5 to the air reservoir 6. In this case the first inlet/exhaust allows air to be drawn into the air motor 5 where it is compressed by the rotating turbine of the air motor 5 and flows to the air reservoir 6 via the secondary inlet /exhaust. When the air pressure in the air reservoir 6 reaches a certain pressure as indicated by the air pressure sensor 10 the electronic control unit 9 closes the electronically controlled valve 7 and disengages the electronically controlled clutch 4 so as to reduce drag on the engine 2.

In order to reduce or eliminate any adverse effect on fuel consumption, the electronic control unit 9 is preferably operable to only operate the air motor 5 as a pump when the motor vehicle 1 is braking or when the engine 2 is in an overrun mode in which fuelling of the engine 2 is cut-off.

However, if the air pressure in the air reservoir falls below a level at which the air motor 5 could not be effectively used, the electronic control unit 9 may also be further operable to recharge the air reservoir by using the air motor 5 as a pump when the engine 2 is running at a substantially constant speed such as cruising on a motorway.

Referring now to Fig.2 there is shown a second embodiment of an apparatus for restarting the engine 2 which is in most respects is identical to that previously described and will not therefore be described again in detail.

The only significant difference between this second embodiment and that described previously is the mode in which the air motor 5 is driven or drives the engine 2.

Whereas, in the previously described embodiment this was by means of a direct drive from the flywheel ring gear 3, in this case it is via a gearbox and clutch assembly 14 driven by a crankshaft of the engine 2 or more accurately from an accessory drive pulley 13 connected to one end of the crankshaft.

The gearbox and clutch assembly 14 includes an electronically controlled clutch that is controlled by the electronic control unit 9. The advantage of this arrangement is that the speed ratio between the engine crankshaft and the turbine of the air pump 5 can be designed to optimise the operation of the air pump 5. In addition, it would be possible to have a different ratio for the use of the air motor 5 when it is being used as a pump and a motor or vary the speed ratio by using a CVT gearbox during the time the air motor 5 is oonneoted to the engine 2.

Operation of the apparatus aooording to this embodiment is as follows, when it is determined from one of the sensors 11 that a ohange of mind event (CoW) has occurred during an engine shut-down seguence, the electronic control unit 9 is operable to use the air motor 5 to speed up the engine 2 to a speed at which combustion can take over. This is achieved as before by opening the electronically controlled valve 7 so as to allow air to flow from the air reservoir 6 into the air motor 5 via the secondary inlet/exhaust through the turbine of the air motor and out via the first inlet/exhaust 8 at the same time or slightly before the electronically controlled valve 7 is opened, the electronic control unit 9 engages the electronically controlled clutch 4 so as to permit drive to be transmitted from the air motor 5 to the engine 2 in order to speed it up. When the engine 2 starts up or reaches a speed where effective starting is possible the electronic control unit 9 disengages the electronically controlled clutch 4 so as to reduce drag on the engine 2 and closes the electronically controlled valve 7 SO as to preserve as much air in the air reservoir as possible.

The electronic control unit 9 is also operable to control the air motor 5 as a pump in order to recharge the air reservoir 6. As before, the electronic control unit 9 engages the electronically controlled clutch 4 so as to permit drive to be transmitted from the engine 2 to the air motor 5 and opens the electronically controlled valve 7 50 as to allow air to flow from the air motor 5 to the air reservoir 6. As before, the first inlet/exhaust allows air to be drawn into the air motor 5 where it is compressed by the rotating turbine and flows to the air reservoir 6 via the secondary inlet /exhaust. When the air pressure in the air reservoir 6 reaches a certain pressure as indicated by the air pressure sensor 10 the electronic control unit 9 closes the electronically controlled valve 7 and disengages the electronically controlled clutch 4 so as to reduce drag on the engine 2.

In order to reduce or eliminate any adverse effect on fuel consumption the electronic control unit 9 is, as before, preferably operable to only operate the air motor 5 as a pump when the motor vehicle 1 is braking or when the engine 2 is in an overrun mode in which fuelling of the engine 2 is cut-off but could be used at other times if required.

Although the air motor 5 is driven via a gearbox in the second embodiment, it will be appreciated that the air motor could alternatively be directly driven from the accessory drive pulley 13 by a belt or chain to produce a desired speed ratio.

Although in the first and second embodiments described above the flow through the air motor 5 is controlled by a single electronically controlled valve it will be appreciated that the invention is not limited to such an arrangement and that other flow control arrangements could be used. For example, the flow to the air reservoir 6 could be via a first passage having a non-return valve so that air can flow only to the air reservoir 6 and the flow to the air motor 5 from the air reservoir 6 to the air motor 5 could be through a second passage controlled by an electronically controlled valve. With such an arrangement the electronically controlled valve is only opened when it is required to restart the engine 2 and there is no need to open it to recharge the air reservoir 6.

It will also be appreciated that the use of an air pressure sensor is not essential to the invention, a pressure relief valve could be fitted to prevent over -10 -pressurising of the air reservoir 6 or the design of the air motor 5 could be such that when the back pressure reaches a certain level stall of the air in the turbine occurs so that over pressurisation of the air reservoir 6 cannot occur.

Although it would be possible to permanently connect the air motor to the engine 2, this is not desirable because when the engine 2 is running the air motor 5 would then always be operating as a pump and this would have a negative effect on fuel economy.

It would also be possible to replace the electronically controlled clutch with a one way clutch such that drive can only be transmitted to the engine 2 from the air motor 5 but this has the disadvantage that a separate means for recharging the air reservoir 6 would be reguired.

It will also be appreciated that the air reservoir could be replenished by means other than the air motor such as for example by a supercharger or turbocharger and that, in such a case, the air motor does not need to be of a reversible type in which it can operate as a pump and a motor but would only need to operate as a motor thereby increasing the types of air motor that could be used.

It will also be appreciated that the air reservoir could be shared with another system and be replenished by a device used to replenish the air reservoir for the other system such as for example a pump for an air braking system.

Referring now to Fig.3 there is shown in a simplified form a method for restarting the engine 2 during a shut-down seguence according to this invention.

The method starts at step 110 where the engine 2 is running. Then in step 120 it is determined whether a shut-down request has been received or to be more precise whether -11 -the stop-start controller has determined that the engine 2 should be shut-down to save fuel and reduce emissions. This shut-down request can be activated by any combination of driver actions known in the art and is not limited to any specific combination of driver actions.

If a shut-down has not be requested the method loops back to step 110 and the engine 2 remains running but if a shut-down has been requested the method advances to step 130 and the stop-start controller or an engine controller will take the necessary actions to begin to shut the engine 2 down. The invention is not limited to any particular shut- down strategy and any known strategy could be used to shut-down the engine 2.

At step 130 it is determined whether a change of mind event has occurred and, if it has, the method advances to step 140 but, if it has not, the method advances to step 135. In practice the test at step 130 is repetitively conducted until the engine speed is substantially zero.

If from step 130 the method has advanced to step 135, no C0M has occurred and the engine 2 will be stopped and the method ends thereafter at step 200.

Conversely, if from step 130 the method has advanced to step 140, the engine 2 will be restarted using the compressed air motor (CAM) 5 and the method ends thereafter at step 200.

Although the invention has been described with respect to the use of the air motor 5 to restart the engine 2 during an engine shut-down by increasing the speed of the engine to a speed where effective combustion can take place, it will be appreciated that the air motor 5 could also be used for restarting the engine 2 from stationary. This will depend upon the size and type of engine and size of air motor.

-12 -Therefore in summary, the invention provides a solution to the problems referred to above by the provision of an engine starting device that can be activated even when the engine is still rotating thereby allowing the engine 2 to be restarted with minimal delay after a CoM event has occurred.

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 alternative embodiments could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

-13 -Claims 1. An apparatus for restarting an internal oombustion engine of a motor vehiole during an engine shut-down due to a driver ohange of mind wherein the apparatus oomprises an air motor driveably oonneoted to the engine and a souroe of oompressed air to selectively drive the air motor when it is reguired to restart the engine.
2. An apparatus as olaimed in olaim 1 wherein the apparatus further oomprises an electronio oontrol unit to oontrol the operation of the air motor.
3. An apparatus as claimed in olaim 2 wherein the apparatus further oomprises an electronioally oontrolled valve to control the flow of air to the air motor from the souroe of oompressed air and the electronio control unit is operable to open the eleotronioally controlled valve in order to energise the air motor.
4. An apparatus as oiaimed in any of olaims 1 to 3 wherein the souroe of oompressed air is an air reservoir and the air motor is used as a pump to recharge the air reservoir with compressed air.
5. An apparatus as ciaimed in claim 5 wherein the air motor is operated as a pump when the motor vehicle is determined to be braking.
6. An apparatus as ciaimed in claim 5 wherein the air motor is operated as a pump when the engine is operating in an overrun condition.
7. An apparatus as claimed in any of claims 1 to 6 wherein the air motor is driveably connected to the engine via an electronically controlled clutch.

-14 -
8. An apparatus as claimed in claim 7 when claim 7 is dependent upcn claim 2 wherein the operation of the electronically controlled clutch is controlled by the electronic control unit.
9. A motor vehicle having an apparatus as claimed in any of claims 1 to 8.
10. A method for restarting an engine during an engine shut-down due to a driver change of mind wherein the method comprises determining that a driver change of mind has occurred and energising an air motor from a source of compressed air to restart the engine.
11. A method as claimed in claim 10 in which the air motor is driveably connected to the engine via a clutch and the method further comprises engaging the clutch when the air motor is energised to restart the engine.
12. A method as claimed in claim 11 wherein the method further comprises disengaging the clutch when the air motor is not energised.
13. A method as claimed in claim 11 wherein the source of compressed air is an air reservoir, the air motor is selectively operable as a pump and the method further comprises engaging the clutch when the air motor is operated as a pump in order to recharge the air reservoir.
14. An apparatus for restarting an internal combustion engine of a motor vehicle substantially as described herein with reference to the accompanying drawing.
15. A motor vehicle substantially as described herein with reference to the accompanying drawing.-15 -
16. A method for restarting an engine substantially as described herein with reference to the accompanying drawing.