Vehicle and method for controlling an engine in a vehicle

A vehicle is provided that includes an engine and an electric machine operable to provide torque to drive the vehicle. A control system, including at least one controller, is configured to selectively and automatically start and stop the engine when the vehicle is in a first operating mode. The control system further includes control logic executable to place the vehicle in a second operating mode wherein the engine can be cranked but not started. The execution of the control logic to place the vehicle in the second operating mode is effected by operation of at least one vehicle system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle and a method for controlling an engine in a vehicle, and more particularly, to a vehicle having an engine and an electric machine operable to provide torque to drive the vehicle.

2. Background Art

In an effort to increase fuel economy, decrease fuel consumption, and decrease exhaust emissions from vehicles, a number of alternative vehicle types are becoming increasingly popular. For example, a hybrid electric vehicle (HEV) that utilizes an internal combustion engine and one or more electric motors to provide torque to power the vehicle, provides an alternative to conventional vehicle types which rely exclusively on an engine to drive the vehicle. In some HEV's, the engine may be automatically stopped whenever it is not needed for such tasks as powering the vehicle, charging a battery, or providing power to operate one or more vehicle systems. Control of the engine in such a vehicle, including the selective starting and stopping of the engine, may be automatically handled by a control system. Therefore, anytime the vehicle is being operated, the engine may or may not be running, depending on the particular requirements of the vehicle.

The selective and automatic starting and stopping of an engine in an HEV, although useful to reduce fuel consumption and exhaust emissions, may present particular challenges to a service technician who needs the engine to run continuously for some period of time while a diagnostic or repair procedure is taking place. One attempt to deal with this situation is discussed in U.S. Pat. No. 6,131,538 issued to Kanai on Oct. 17, 2000. Kanai discusses an apparatus for controlling the engine in an HEV, including operation of the engine in an inspection mode. In order to facilitate the inspection mode, a check wire is applied to a diagnosis connector to connect a pair of predetermined electric terminals to each other. The connection of these terminals provides an output signal that facilitates putting the engine in an inspection mode—a mode which may be characterized by continuous operation of the engine.

One limitation of the apparatus described in Kanai, is the need to use an external device, such as the check wire, to facilitate placing the engine in the inspection mode. It would be more convenient, and therefore desirable, if an HEV were equipped to operate an engine in an inspection mode by using only existing vehicle systems, thereby eliminating the need for any external devices. In addition, it may desirable to provide other inspection modes, wherein the engine is operated under some other predetermined set of conditions that were different from the normal operating conditions. For example, in order to check the compression of the cylinders in the engine, it is necessary to crank the engine—i.e., move the pistons up and down within their respective cylinders—while prohibiting starting of the engine.

Such an inspection mode is described for a hybrid electric vehicle in Toyota Prius Repair Manual, Vol. 2, Pub. No. RM778U2, Copyright 2000 Toyota Motor Corporation. The compression inspection routine provides a cranking mode during which cylinder compression can be measured. To facilitate the compression inspection, a hand-held tester is connected to an input port and a cranking mode is chosen on the hand-held tester. This method also requires the use of a device external to the vehicle to facilitate the testing. It would be desirable to facilitate this type of inspection mode in an HEV without the need to use external devices which may add cost and complexity to the procedure.

SUMMARY OF THE INVENTION

Accordingly, one advantage of the present invention is that it provides a hybrid electric vehicle that can be placed in a diagnostic mode wherein the engine can be cranked, but not started, and this diagnostic mode can be entered without the use of any devices external to the vehicle.

Another advantage of the invention is that it provides a vehicle that can be placed in an inspection mode wherein the engine may be operated continuously.

Another advantage of the invention is that it provides a timed sequence of operations of vehicle systems to place the vehicle in an inspection mode, the timed sequence helping to ensure that the vehicle is not unintentionally placed in the inspection mode.

The invention also provides a vehicle including an engine and an electric machine operable to provide torque to drive the vehicle. A control system includes at least one controller, and is configured to selectively and automatically start and stop the engine when the vehicle in a first operating mode. The control system further includes control logic that is executable to place the vehicle in a second operating mode wherein the engine can be cranked but not started. The execution of the control logic to place the vehicle in the second operating mode is effected by operation of at least one vehicle system.

The invention further provides a vehicle including an engine and an electric machine operable to provide torque to drive the vehicle. A control system, including at least one controller, is configured to effect at least two vehicle operating modes. The vehicle operating modes include a normal operating mode and a first diagnostic operating mode. The normal operating mode includes selective and automatic starting and stopping of the engine based at least in part on vehicle power requirements. The first diagnostic operating mode is effective to facilitate cranking of the engine and prohibit starting of the engine. At least one vehicle system is operable in a predetermined manner to change the vehicle operating mode from the normal operating mode to the first diagnostic operating mode.

The invention also provides a method for controlling an engine in a vehicle having an electric machine operable to provide torque to drive the vehicle. The vehicle includes a first operating mode wherein the engine is selectively and automatically started and stopped based at least in part on vehicle power requirements. The method includes operating at least one vehicle system in a first predetermined manner to change the vehicle operating mode from the first operating mode to a second operating mode. The change in the vehicle operating mode thus occurs without employing the use of a device external to the vehicle. The second operating mode facilitates cranking of the engine and prohibiting starting of the engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1shows a schematic representation of a vehicle10in accordance with the present invention. The vehicle10includes an engine12and an electric machine, or generator14. The engine12and the generator14are connected through a power transfer unit, which in this embodiment is a planetary gear set16. Of course, other types of power transfer units, including other gear sets and transmissions may be used to connect the engine12to the generator14. The planetary gear set includes a ring gear18, a carrier20, planet gears22, and a sun gear24.

The generator14can also be used as a motor, outputting torque to a shaft26connected to the sun gear24. Similarly, the engine12outputs torque to a shaft28connected to the carrier20. A brake30is provided for stopping rotation of the shaft26, thereby locking the sun gear24in place. Because this configuration allows torque to be transferred from the generator14to the engine12, a one-way clutch32is provided so that the shaft28rotates in only one direction. Having the generator14operatively connected to the engine12, as shown inFIG. 1, allows the speed of the engine12to be controlled by the generator14.

The ring gear18is connected to a shaft34, which is connected to vehicle drive wheels36through a second gear set38. The vehicle10includes a second electric machine, or motor40, which can be used to output torque to a shaft42. Other vehicles within the scope of the present invention may have different electric machine arrangements, such as more or less than two electric machines. In the embodiment shown inFIG. 1, the motor40and the generator14can both be used as motors to output torque. Alternatively, each can also be used as a generator, outputting electrical power to a high voltage bus44and to an energy storage device, or battery46.

The battery46is a high voltage battery that is capable of outputting electrical power to operate the motor40and the generator14. Other types of energy storage devices and/or output devices can be used with a vehicle, such as the vehicle10. For example, a device such as a capacitor can be used, which, like a high voltage battery, is capable of both storing and outputting electrical energy. Alternatively, a device such as a fuel cell may be used in conjunction with a battery and/or capacitor to provide electrical power for the vehicle10.

As shown inFIG. 1, the motor40, the generator14, the planetary gear set16, and a portion of the second gear set38may generally be referred to as a transaxle48. To control the engine12and the components of the transaxle48—i.e., the generator14and motor40—a control system, including a controller50, is provided. As shown inFIG. 1, the controller50is a vehicle system controller (VSC), and although it is shown as a single controller, it may include multiple controllers. For example, the VSC50may include a separate powertrain control module (PCM), which could be software embedded within the VSC50, or it could be a separate hardware device.

A controller area network (CAN)52allows the VSC50to communicate with the transaxle48and a battery control mode (BCM)54. Just as the battery46has the BCM54, other devices controlled by the VSC50may have their own controllers. For example, an engine control unit (ECU) may communicate with the VSC50and may perform control functions on the engine12. In addition, the transaxle48may include one or more controllers, such as a transaxle control module (TCM), configured to control specific components within the transaxle48, such as the generator14and/or the motor40. Some or all of these controllers may be a part of a control system for the present invention.

In addition to inputs from the transaxle48, the VSC50also includes inputs from other vehicle systems. For example, an accelerator pedal56communicates an accelerator pedal position to the VSC50. In addition, an ignition switch58communicates to the VSC50whether it is in a stop, run, or start position. Also shown inFIG. 1is a transmission gear selector60which communicates to the VSC50which gear the driver has selected—e.g., park, neutral, forward or reverse.

The VSC50is programmed with control logic that is effective to place the vehicle10in one or more operating modes. For example, the vehicle10includes a first, or normal operating mode, during which the VSC50will selectively and automatically start and stop the engine12based at least in part on power requirements of the vehicle10. In the normal operating mode, the VSC50evaluates inputs from a number of the vehicle systems to determine the vehicle power requirements—e.g., the amount of torque required to propel the vehicle10and the amount of electrical energy required from the battery46to power various vehicle systems. When the VSC50determines that the engine12is not required, the engine12will be shut off until vehicle operating conditions change. If the vehicle10were always operated in the normal operating mode, it could be difficult for a technician to service the vehicle10, and particularly difficult to service the engine12. Thus, the present invention contemplates at least one diagnostic mode, wherein operation of the engine is independent of the vehicle power requirements.

In one diagnostic mode, for example, it may be desirable to operate the engine such that it is allowed to crank, but not to start. In such a situation, the engine crankshaft would spin, and the pistons move up and down, but no combustion would occur. To facilitate operation in a cranking mode such as this, the present invention provides a second operating mode, or first diagnostic operating mode, during which cranking of the engine12is facilitated, but starting of the engine12is prohibited.

To facilitate changing the vehicle operating mode from the normal operating mode to the first diagnostic operating mode, it is desirable to rely on existing vehicle systems. That is, it may be inconvenient and costly to require the use of computers, scanning devices, and/or other diagnostic devices external to the vehicle10merely to change the operating mode. Therefore, the present invention provides a method for changing the vehicle operating mode without employing the use of a device external to the vehicle. In order to facilitate changing of the operating mode of the vehicle10, any of a number of vehicle systems can be used. For example, the VSC50can be configured such that the accelerator pedal56, the ignition switch58, and the transmission gear selector60may be used individually, or together, in some predetermined sequence of steps, in order to change the vehicle operating mode.

FIG. 2illustrates one example of control logic that can be programmed into a controller, such as the VSC50, in order to facilitate a change in vehicle operating modes from a normal operating mode to an engine cranking diagnostic mode. As shown in block62, the Mode Process evaluates a number of inputs. For example, a state of charge (SOC) of the battery46is input, as is an accelerator pedal position (APP), a transmission gear selector position (PRNDL), and a key position for the ignition switch58. As noted above, and explained more fully below, the accelerator pedal56, the ignition switch58, and the transmission gear selector60can be operated in a predetermined sequence of steps to place the vehicle operating mode in the engine cranking diagnostic mode.

As shown in the Mode Process block62, the sequence of vehicle system operations is recognized, and the diagnostic state is set. Under certain conditions, the Mode Process62will cancel the diagnostic mode, even when the appropriate sequence of steps is recognized. For example, if the battery SOC is below some predetermined value—e.g., 45%—the mode process logic will not allow the vehicle to be changed to the engine cranking diagnostic mode. This is because engine cranking will draw energy from the battery46, and prohibiting entry into the engine cranking diagnostic mode helps to ensure that the battery SOC will not go too low.

The Mode Process62also commands the position of a throttle (not shown) based on the accelerator pedal position. If the accelerator pedal is fully depressed, the Mode Process62will command the throttle to be wide open. Conversely, if the accelerator pedal is completely released, the Mode Process62will command the throttle to be completely closed (this is sometimes called “closed in the bore”). If the accelerator pedal position is in any other position except fully open or fully closed, the Mode Process62will command the throttle to remain in its previous state—i.e., fully open or fully closed.

The throttle command is received by the Controlled Start/Stop Process, shown in block64. The Controlled Start/Stop Process64commands the throttle position to the electronic throttle control (ETC) based on the throttle command received from the Mode Process62. In addition, the Controlled Start/Stop Process64enables ignition, but disables fuel injectors. This is because it is desirable to allow the engine12to crank, by placing the ignition switch58in the start position, but at the same time, ensure that no combustion occurs. Thus, the fuel injectors are disabled in this mode. As shown inFIG. 2, the ETC66receives information regarding the throttle status from the Controlled Start/Stop Process64.

In addition to communicating with the ETC66, the Controlled Start/Stop Process64communicates with a Mode Select Process, shown in block68. The Mode Select Process68is effective to crank the engine12when the ignition switch58is in the start position. Here, a start flag is set to “TRUE”. In addition, the Mode Select Process68inhibits engine pull-up—i.e., the engine12is not allowed to start. Here, an engine request flag is set to zero, and this is communicated back to the Controlled Start/Stop Process64. The Mode Select Process68also sends an engine target speed to a transaxle control module (TCM)70. The TCM70can keep the engine12operating at some predetermined speed when the ignition switch58is in the start position. Thus, the engine cranking diagnostic mode may be useful for such things as checking the compression in the cylinders of the engine12, as well as checking the engine speed.

As shown inFIG. 2, the Mode Select Process68receives a start flag from the Mode Process62. The Mode Process62also puts out a signal indicating the engine diagnostic state to the Controlled Start/Stop Process64, the Mode Select Process68, as well as a Battery Control Process72and a Driver Information Process74. In the Battery Control Process72, reconditioning modes (R-modes) for the battery46are inhibited. This helps to ensure that the battery46will have enough charge to complete the engine cranking diagnostic testing. In addition, the Mode Process62can be configured to cancel the engine cranking diagnostic mode at any time when the SOC of the battery46falls below a second predetermined battery charge level. The second predetermined battery charge level, for example, 35%, will typically be below the charge level used to inhibit placing the vehicle10in the engine cranking diagnostic mode from the normal mode.

The Driver Information Process74can provide some indication—e.g., either audible, visual, or some combination thereof—that the vehicle is in the engine cranking diagnostic mode. As shown in block74, a flashing red light may be conveniently used as such an indicator. This information is then sent to an instrument cluster (IC)76.

In addition to the engine cranking diagnostic mode, the present invention can also provide a third vehicle operating mode, or second diagnostic operating mode. The control logic for such a mode, in particular an engine running diagnostic mode, is shown inFIG. 3. As with the engine cranking diagnostic mode logic shown inFIG. 2, the engine running diagnostic mode logic can be programmed into the VSC50. Alternatively, some or all of this logic could be programmed into other vehicle controllers. In the engine running diagnostic mode, operation of the engine12is independent of the vehicle power requirements. In particular, the engine12is allowed to run continuously, and is not subject to the selective and automatic starting and stopping that is indicative of the normal operating mode.

In the engine running diagnostic mode, a Mode Process78receives a number of inputs, including accelerator pedal position, the position of the ignition switch58, and the position of the transmission gear selector60. The Mode Process78recognizes the sequence of operation and position of the accelerator pedal56, the ignition switch58, and the transmission gear selector60; when the proper sequence is recognized, engine pull-down is inhibited. This means that the engine12will not be shut off according to the logic used in the normal operating mode. When the engine12stops, the engine running diagnostic mode is automatically canceled.

The Mode Process78sends a throttle command to the Controlled Start/Stop Process—see block80. In turn, the Controlled Start/Stop Process80sends an engine running status indicator back to the Mode Process78. As shown inFIG. 3, the Controlled Start/Stop Process80controls the engine12exactly the same as if the vehicle10were in the normal operating mode and the engine12was requested to run based on vehicle power requirements or other considerations. As in the engine cranking diagnostic mode, the Controlled Start/Stop Process80communicates with the ETC66.

As shown inFIG. 3, the Mode Process78also communicates with the Mode Select Process—see block82. In particular, the Mode Process78sends an engine pull-up/pull-down request to the Mode Select Process82. The Mode Select Process82behaves the same as it would if the vehicle10were in the normal operating mode. That is, if the Mode Process78commands the engine12to start (pull-up), the Mode Select Process82will facilitate engine start. Conversely, if the Mode Process78requests an engine pull-down, the Mode Select Process82will stop the engine12. As with the engine cranking diagnostic mode, shown inFIG. 2, the Mode Select Process82also communicates with the TCM70.

In addition to communicating with the Controlled Start/Stop Process80and the Mode Select Process82, the Mode Process78also communicates with a Battery Control Process84and a Driver Information Process86. The Battery Control Process84receives the engine diagnostic state from the Mode Process78. When the engine running diagnostic mode has been initiated, the Battery Control Process84inhibits R-modes for the battery46. In order to identify the engine running diagnostic mode separately from the engine cranking diagnostic mode, the Driver Information Process86uses a different audible and/or visual indicator to show that the vehicle10is in the engine running diagnostic mode. For example, an iconic indicator, such as a wrench or other representation, may be used in conjunction with a light that has a color different from the color used to indicate the engine cranking diagnostic mode. When a visual indicator is used, this information is then displayed on the IC76.

As noted above, the present invention contemplates the use of vehicle systems, rather than external devices, to change the vehicle operating mode from the normal operating mode to the engine cranking diagnostic mode. A predetermined sequence of operations can be required to effect such a change. This can help to ensure that the vehicle10is not inadvertently placed in the engine cranking diagnostic mode. In addition, it may be beneficial to require that at least some of the steps in the predetermined sequence of steps be performed within a predetermined time period, to further ensure that the vehicle10is not inadvertently placed in the engine cranking diagnostic mode.

FIG. 4shows a flow chart88illustrating a method of changing a vehicle10from the normal operating mode to the engine cranking diagnostic mode. It is worth noting that althoughFIG. 4, andFIG. 5discussed below, illustrate a particular sequence of operations for changing the vehicle operating mode, the present invention contemplates the use of other methods for changing the vehicle operating mode. InFIG. 4, the first step in changing the vehicle operating mode is shown in block90, where the ignition switch58is moved from the “off” position to the “run” position.

The next step, shown in block92, must be performed within some predetermined time after the ignition switch58is moved to the “run” position. This time is shown inFIG. 4as “tstep”. The time, tstep, can be any convenient time period, for example, 0<tstep<5 sec. The operation shown in block92—fully depressing the accelerator pedal56—must not only be performed within five seconds of step90, but the accelerator pedal56must be held for a period of “Time1”. The time, Time1, can be set to any convenient time period, such as 5 sec.<Time1<15 sec.

After the accelerator pedal56is held fully open for some time within the time period Time1, the accelerator pedal56is then fully released at step94. Step96must again be performed within five seconds of the previous step. Step98involves changing the transmission gear selector60from park to neutral. Then, the accelerator pedal56is again fully depressed for some time within the time period Time1. At step98, the accelerator pedal56is released, and within five seconds, the transmission gear selector60is changed from neutral to park—see step100. The vehicle10is now in the engine cranking diagnostic mode. As noted above, the vehicle10will be placed back in the normal operating mode if the SOC of the battery46falls below some predetermined battery charge level. Moreover, the vehicle10will return to the normal operating mode if the ignition switch58is turned to the “off” position.

FIG. 5shows a flow chart102illustrating a method for changing the vehicle operating mode from the normal operating mode to the engine running diagnostic mode. As will be readily seen, many of the steps are the same as the steps used to change the vehicle operating mode from the normal operating mode to the engine cranking diagnostic mode. In fact, it is the same vehicle systems which are used to effect the change into each of the respective diagnostic modes. As shown in the flow chart102, however, there is a different predetermined sequence of steps from that which is used in the flow chart88, shown inFIG. 4.

At step104, the ignition switch58is moved from the “off” position to the “run” position. Within a time period that is less than tstep, the accelerator pedal56is held fully depressed for some time within the time period, Time1—see step106. It is worth noting that the time period tstepand time1are the same for both the engine cranking diagnostic mode and the engine running diagnostic mode. Although these time periods need not be the same for each of the two diagnostic modes, it may be convenient to set them the same, so as to provide consistency between the two diagnostic modes.

At step108, the accelerator pedal56is fully released, and within a time period less than tstep, the transmission gear selector60is changed from park to drive. The accelerator pedal56is again held fully depressed for some time within the time period Time1; this is illustrated at step110. At step112, the accelerator pedal56is fully released, and within the time period tstep, the transmission gear selector60is changed from drive to park—see step114. The vehicle10is now in the engine running diagnostic mode. When the ignition switch58is turned to the “start” position, the engine12will be started, and will be operated as if the vehicle10were in the normal mode and the engine12was requested to run based on vehicle power requirements or other considerations.

Just as with the engine cranking diagnostic mode, should any of the steps required to place the vehicle10in the engine running diagnostic mode fail, the vehicle10will remain in the normal operating mode. This again helps to ensure that the vehicle10will not be inadvertently placed into one of the diagnostic modes. As noted above in a description of the engine running diagnostic mode logic shown inFIG. 3, there is no set throttle command for this operating mode. Thus, the engine can be revved or otherwise operated at different speeds to facilitate the diagnostic testing. While the engine12is running, it may continue to charge the battery46, even if it charges at a low rate. If the battery SOC gets too high while the vehicle10is in the engine running diagnostic mode, the engine12will be automatically shut off. If the engine12stops for any reason when the vehicle10is in the engine running diagnostic mode, the vehicle10will automatically be placed back into the normal operating mode.