Control device for a hybrid vehicle

Abstract

A control device and a control method of a hybrid vehicle are provided. The control device of the hybrid vehicle executes engine start processing including a first start processing of driving a motor generator and a second start processing executed with a condition that a shift condition is satisfied in the first start processing. The second start processing includes driving the motor generator after supply of electric power to the motor generator is interrupted. The control device determines that the start of the engine is successful based on the engine rotation speed becoming above an engine rotation speed threshold within a second time threshold as an elapsed time in the execution of the second start processing. The second time threshold is larger than a first time threshold compared with the elapsed time in the execution of the first start processing.

Description

Technical Field

[0001] This disclosure relates to a control device and control method for hybrid vehicles. Background Technology

[0002] The control device described in Japanese Patent Application Publication No. 2015-009743 performs the starting process of starting the engine. If the engine speed is below a specified speed after a certain period has elapsed from the start time of the starting process, the control device determines that the engine has failed to start.

[0003] The control device described in Japanese Patent Application Publication No. 2013-082404 controls a vehicle equipped with an electric generator, a starter, and an engine. When the control device determines that starting the engine using the electric generator has failed, it starts the engine using the starter.

[0004] The starter starts the engine as follows: First, the starter's pinion engages with a drive plate mounted on the crankshaft. Then, the starter is driven by electricity from the battery. This causes the crankshaft to rotate, and the engine starts. A large force is applied to the drive plate during engine starting. Therefore, starting the engine with the starter is accompanied by considerable noise.

[0005] For example, a structure could be considered in which an electric generator is connected to the engine via a belt. In this configuration, starting the engine with the electric generator is much quieter than starting the engine with a starter. This is because driving the engine with a belt is much quieter than driving the engine with gears.

[0006] A structure could be considered for hybrid vehicles where the engine and generator are connected, allowing for a determination of generator starting failure based on a certain time interval. This time interval is set to prevent damage to the battery from prolonged high-voltage power supply due to generator start-up. Furthermore, a structure could be considered for the aforementioned hybrid vehicle to start the engine using a starter when the generator fails to start it. As mentioned above, from a quietness perspective, it is desirable to increase the chances of the generator starting the engine. Summary of the Invention

[0007] According to one aspect of this disclosure, a control device for a hybrid vehicle is provided. The hybrid vehicle includes an engine and an electric generator interconnected via a belt, a battery configured to supply power to the electric generator, and a starter configured to start the engine. The control device includes a processing circuit configured to perform engine starting processing when an execution condition for starting the engine is met. The engine starting processing includes: a first starting process for supplying power from the battery to the electric generator to drive the electric generator in order to start the engine; and a second starting process executed conditionally, wherein a logical OR condition, i.e., a transfer condition, is met in the first starting process, whereby the engine speed (i.e., the engine rotation speed) becomes less than 0 and the engine speed remains 0 for a predetermined period. The second starting process includes interrupting the power supply from the battery to the electric generator. After the electric generator receives power, it supplies power from the battery to drive the electric generator in order to start the engine. The processing circuit is configured such that: if, during the execution of the first starting process, the elapsed time from the start time of the first starting process exceeds a first time threshold and the engine speed is less than the engine speed threshold, it is determined that the electric generator has failed to start the engine. The processing circuit is configured such that: if, during the execution of the second starting process, the elapsed time exceeds a second time threshold and the engine speed is less than the engine speed threshold, it is determined that the electric generator has failed to start the engine. The second time threshold is greater than the first time threshold. The processing circuit is configured such that, in the case of the electric generator failing to start the engine, it uses the starter to start the engine.

[0008] According to one aspect of this disclosure, a control device for a hybrid vehicle is provided. The hybrid vehicle includes an engine and an electric generator interconnected via a belt, a battery configured to supply power to the electric generator, and a starter configured to start the engine. The control device includes a processing circuit configured to execute engine starting processing when an execution condition for starting the engine is met. The engine starting processing includes: a first starting process, which supplies power from the battery to the electric generator to drive the electric generator in order to start the engine; and a second starting process, executed on the condition that the engine speed, i.e., the engine rotation speed, becomes less than 0 during the first starting process. The second starting process includes, after interrupting the power supply from the battery to the electric generator, starting the engine... The engine starts and supplies power from the battery to the electric generator to drive the electric generator. The processing circuit is configured such that: if, during the execution of the first starting process, the elapsed time from the start time of the first starting process exceeds a first time threshold and the engine speed is less than an engine speed threshold, it is determined that the electric generator has failed to start the engine. The processing circuit is configured such that: if, during the execution of the second starting process, the elapsed time exceeds a second time threshold and the engine speed is less than the engine speed threshold, it is determined that the electric generator has failed to start the engine. The second time threshold is greater than the first time threshold. The processing circuit is configured such that, if the electric generator fails to start the engine, the engine is started using the starter.

[0009] According to one aspect of this disclosure, a control method for a hybrid vehicle is provided. The hybrid vehicle includes an engine and an electric generator interconnected via a belt, a battery configured to supply power to the electric generator, and a starter configured to start the engine. The control method includes performing an engine starting process when execution conditions for starting the engine are met. The engine starting process includes: a first starting process, in which power is supplied from the battery to the electric generator to drive the electric generator in order to start the engine; and a second starting process, performed when the engine speed (i.e., the engine rotation speed) becomes less than 0 during the first starting process or when the engine speed remains at 0 for a predetermined period. The second starting process includes supplying power from the battery to the electric generator to drive the electric generator in order to start the engine after the power supply from the battery to the electric generator is interrupted. The method includes: if, during the execution of the first start-up process, the elapsed time from the start time of the first start-up process exceeds a first time threshold and the engine speed is less than an engine speed threshold, determining that the electric generator has failed to start the engine; the control method includes: if, during the execution of the second start-up process, the elapsed time exceeds a second time threshold and the engine speed is less than the engine speed threshold, determining that the electric generator has failed to start the engine, the second time threshold being greater than the first time threshold; the control method includes: if the electric generator fails to start the engine, using the starter to start the engine. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating a control device according to one embodiment and a hybrid vehicle that is the object controlled by the control device.

[0011] Figure 2 This is a diagram illustrating the combustion cycle.

[0012] Figure 3 This is a schematic diagram showing the movement of multiple cylinders in the first and second starting processes.

[0013] Figure 4 This diagram illustrates the movement of the piston rings after the start of the second start-up process.

[0014] Figure 5 This is a timeline showing the successful starting of the engine by the electric generator through the first starting process.

[0015] Figure 6This is a timeline for situations where the generator fails to start the engine due to timeout during the first start-up process.

[0016] Figure 7 This is a timeline showing the successful starting of the engine by the electric generator via the second starting process.

[0017] Figure 8 This is a timeline for situations where the generator fails to start the engine due to timeout during the second start-up process.

[0018] Figure 9 yes Figure 1 The flowchart shows the process executed by the control device.

[0019] Figure 10 yes Figure 1 The flowchart shows the process executed by the control device. Detailed Implementation

[0020] Hereinafter, the control device 34 of the control device of the hybrid vehicle according to one embodiment will be described with reference to the accompanying drawings.

[0021] <Regarding the structure of hybrid vehicle 100>

[0022] Figure 1 A hybrid vehicle (hereinafter referred to as "vehicle") 100, which is controlled by a control device 34 according to one embodiment, is shown. The control device 34 is mounted on the vehicle 100. The vehicle 100 includes an internal combustion engine (hereinafter referred to as "engine") 10 and an electric generator 12. An air conditioning compressor (hereinafter referred to as "AC compressor") 14 is mounted on the vehicle 100. The engine 10 has a crankshaft pulley 10a. The electric generator 12 has an electric generator pulley 12a. The AC compressor 14 has an AC compressor pulley 14a. The crankshaft pulley 10a, the electric generator pulley 12a, and the AC compressor pulley 14a are interconnected via a belt 16.

[0023] Thus, in vehicle 100, engine 10 and electric generator 12 are interconnected via belt 16. Control device 34 controls such vehicle 100.

[0024] The vehicle 100 also includes a transmission 18, a starter 20, a DC-DC converter 22, an auxiliary machine 24, a high-voltage battery 26, and a low-voltage battery 28. The high-voltage battery 26 is, for example, a Li-ion battery. The low-voltage battery 28 is, for example, a lead-acid battery. The transmission 18 is connected to the engine 10. The starter 20 is connected to the transmission 18. The starter 20 can drive the transmission 18. By using the starter 20 to drive the transmission 18, the engine 10 can be started. The high-voltage battery 26 is connected to an electric generator 12 and the DC-DC converter 22. The electric generator 12, by receiving power from the high-voltage battery 26, can start the engine 10. The low-voltage battery 28 is connected to the starter 20, the DC-DC converter 22, and the auxiliary machine 24.

[0025] Engine 10 has four cylinders: #1, #2, #3, and #4. For each of cylinders #1 to #4, when the intake valve 40 is open, the intake air flows into the combustion chamber 38. Fuel is injected into the combustion chamber 38 by the fuel injection valve 44. In the combustion chamber 38, the air-fuel mixture is burned by a spark discharge from the ignition device 46. The energy generated by combustion is extracted as rotational energy of the crankshaft of engine 10. The crankshaft of engine 10 is connected to the transmission 18. The afterburning mixture is discharged from the combustion chamber 38 when the exhaust valve 42 is open.

[0026] The control device 34 includes a so-called microcomputer with a CPU, ROM, RAM, and input / output interfaces. The control device 34 performs signal processing according to a program pre-stored in the ROM while utilizing the temporary storage function of the RAM. The control device 34 is capable of controlling the engine 10 and the electric generator 12, etc.

[0027] An engine speed sensor 30 is provided in the engine 10. The control device 34 can obtain the engine speed of the engine 10, i.e., the engine speed, through the engine speed sensor 30. An electric generator speed sensor 32 is provided in the electric generator 12. The control device 34 can obtain the electric generator speed of the electric generator 12 through the electric generator speed sensor 32.

[0028] <Factors that contribute to the successful starting of the electric generator 12 and the engine 10>

[0029] Imagine the situation where the electric generator 12 starts the engine 10 from a state where the engine speed is 0.

[0030] like Figure 2As shown, cylinder #1 is in the expansion stroke when the crankshaft angle is 0–180 degrees. Cylinder #1 is in the exhaust stroke when the crankshaft angle is 180–360 degrees. Cylinder #1 is in the intake stroke when the crankshaft angle is 360–540 degrees. Cylinder #1 is in the compression stroke when the crankshaft angle is 540–720 degrees.

[0031] like Figure 2 As shown, cylinder #2 is in the exhaust stroke when the crankshaft angle is 0–180 degrees. Cylinder #2 is in the intake stroke when the crankshaft angle is 180–360 degrees. Cylinder #2 is in the compression stroke when the crankshaft angle is 360–540 degrees. Cylinder #2 is in the expansion stroke when the crankshaft angle is 540–720 degrees.

[0032] like Figure 2 As shown, cylinder #3 is in the compression stroke when the crankshaft angle is 0–180 degrees. Cylinder #3 is in the expansion stroke when the crankshaft angle is 180–360 degrees. Cylinder #3 is in the exhaust stroke when the crankshaft angle is 360–540 degrees. Cylinder #3 is in the intake stroke when the crankshaft angle is 540–720 degrees.

[0033] like Figure 2 As shown, cylinder #4 is in the intake stroke when the crankshaft angle is 0–180 degrees. Cylinder #4 is in the compression stroke when the crankshaft angle is 180–360 degrees. Cylinder #4 is in the expansion stroke when the crankshaft angle is 360–540 degrees. Cylinder #4 is in the exhaust stroke when the crankshaft angle is 540–720 degrees.

[0034] Thus, regardless of the crankshaft angle, one of the four cylinders #1 to #4 is in the compression stroke, and the other one of the four cylinders #1 to #4 is in the expansion stroke. In the cylinders in the compression or expansion stroke, the intake valve 40 and exhaust valve 42 are closed. Therefore, when the electric generator 12 starts the engine 10, the piston 50 in the cylinders in the compression or expansion stroke is not easily moved. That is, a load is applied to the electric generator 12. For example, if the electric generator 12 starts driving the engine 10 from a crankshaft angle of 0 degrees, a load is applied to the electric generator 12 due to cylinders #1 and #3. For example, if the electric generator 12 starts driving the engine 10 from a crankshaft angle of 180 degrees, a load is applied to the electric generator 12 due to cylinders #3 and #4 after passing through a crankshaft angle of 180 degrees.

[0035] If the electric generator 12 can overcome the load generated in the cylinder during the compression stroke and the cylinder during the expansion stroke, then the engine 10 will start successfully.

[0036] <Summary of the First and Second Startup Processes>

[0037] Figure 3 This illustrates a case where the electric generator 12 successfully starts the engine 10 through the first and second starting processes.

[0038] Figure 3 (a) shows the state at a crankshaft angle of 45 degrees. At a crankshaft angle of 45 degrees, cylinder #1 is in the expansion stroke and cylinder #3 is in the compression stroke. From the state at a crankshaft angle of 45 degrees, the electric generator 12 begins to drive the engine 10.

[0039] Figure 3 (b) shows the state at a crankshaft angle of 160 degrees. Assumption: Due to the compressed air in cylinder #3, the engine speed becomes less than 0 at a crankshaft angle of 160 degrees. Based on the engine speed becoming less than 0, control device 34 interrupts the power supply from high-voltage battery 26 to electric generator 12.

[0040] According to the control device 34, the power supply to the electric generator 12 was interrupted, and the crankshaft began to reverse. Shortly afterward, as... Figure 3 As shown in (c), the engine speed becomes 0. Figure 3 (c) shows the state with the crankshaft angle at 75 degrees.

[0041] Next, control device 34 begins to drive electric generator 12 by starting the supply of power to it. For example... Figure 3 As shown in (d), the crankshaft angle of 180 degrees is achieved. In this case, the electric generator 12 successfully starts the engine 10.

[0042] The process from the moment the electric generator 12 starts driving the engine 10 from a crankshaft angle of 45 degrees until the engine speed becomes less than 0 is equivalent to the first starting process. The process after the engine speed becomes less than 0 is equivalent to the second starting process.

[0043] Reference Figure 4 This explains why starting the engine 10 can sometimes be successful through the first and second starting processes.

[0044] Figure 4 The piston 50 in cylinder #3 during its compression stroke is shown. An annular groove 52 is formed on the outer circumferential surface of the piston 50. A piston ring 54 is fitted into the annular groove 52.

[0045] From the moment the electric generator 12 begins driving the engine 10 until the engine speed reaches zero, the lower part of the piston ring 54 is in close contact with the piston 50. At this time, the piston 50 is being driven by the electric generator 12 towards... Figure 4The piston is driven from above. Furthermore, the piston ring 54 is pressurized by the air pressure within cylinder #3. Therefore, the piston ring 54 is pressure-driven towards... Figure 4 The downward pressure from below causes the lower part of piston ring 54 to adhere tightly to piston 50. Specifically, as... Figure 4 As shown in (a), at the point when the engine speed is 0, the lower part of the piston ring 54 is in close contact with the piston 50.

[0046] If the engine speed becomes less than 0 due to the repulsive force of the compressed air in cylinder #3, the second starting process begins. As a result, the power supply to the electric generator 12 is temporarily interrupted. If the power supply to the electric generator 12 stops, the force acting on piston 50 that drives piston 50 upwards disappears. Furthermore, piston 50 is pressed down by the repulsive force of the compressed air.

[0047] like Figure 4 As shown in (b), after the crankshaft has just begun to reverse, if the force driving the piston 50 upward as described above disappears and the piston 50 is pressed down, the lower part of the piston ring 54 will separate from the piston 50. As the lower part of the piston ring 54 separates from the piston 50, compressed air flows out of the combustion chamber 38 through the gap between the inner circumferential surface of the piston ring 54 and the ring groove 52. Shortly afterward, as... Figure 4 As shown in (c), the lower part of the piston ring 54 presses against the piston 50 again, thereby stopping the outflow of compressed air from the combustion chamber 38.

[0048] In the second starting process, the amount of compressed air in cylinder #3 is less than in the first starting process. Therefore, the electric generator 12 can easily overcome the load generated in the cylinder during the compression stroke and the cylinder during the expansion stroke.

[0049] <Successful starting of the motor 10 via the first starting process>

[0050] Reference Figure 5 The following describes the successful starting of the engine 10 by the electric generator 12 through the first starting process. Figure 5 In the example shown, within the first time threshold described later, the engine speed becomes above the engine speed threshold described later, and thus the engine 10 is successfully started through the first start-up process.

[0051] At time T10, control device 34 determines that the starting conditions for engine 10 have been met. The starting conditions for engine 10 include, for example, the ignition switch of vehicle 100 being turned on. Control device 34 begins engine starting processing from time T10. Figure 5In the example shown, the engine starting process only includes a first starting process. The first starting process includes a first pre-torque process and a first MG high-voltage application process.

[0052] Control device 34 performs a first pre-torque process from time T10 to time T11. The first pre-torque process includes applying a tension (not shown) to belt 16. In the first pre-torque process, control device 34 uses a small MG required torque to control the electric generator 12. Through the first pre-torque process, belt 16 is brought to the desired tension. Thus, force can be transmitted from the electric generator pulley 12a to the crankshaft pulley 10a via belt 16.

[0053] Next, control device 34 begins the first MG high voltage application process from time T11. In the first MG high voltage application process, control device 34 uses the large MG required torque to control the electric generator 12. That is, control device 34 supplies power from high-voltage battery 26 to electric generator 12 to drive electric generator 12 in order to start engine 10.

[0054] At time T12, control device 34 determines that the engine speed is above the engine speed threshold. The engine speed threshold is set as a threshold for determining whether the starting of the engine 10 by the electric generator 12 has been successful. Control device 34 terminates the first MG high voltage application process based on the determination that the engine speed is above the engine speed threshold at time T12.

[0055] During the execution of the first start-up process, the control device 34 monitors whether the elapsed time from the start time T10 of the first start-up process is below a first time threshold. The first time threshold is the sum of the first pre-torque period A and the battery rated time BRT. The first pre-torque period A means the period from the start to the end of the first pre-torque process. The battery rated time BRT means the rated time of the high-voltage battery 26. The rated time of the high-voltage battery 26 is set as a limit to which the high-voltage battery 26 can be safely used at high voltage. Using the high-voltage battery 26 at high voltage means supplying power from the high-voltage battery 26 to the electric generator 12 in order to start the engine 10.

[0056] exist Figure 5 In the example shown, the sum of the first pre-torque period A and the first MG high-voltage application period B is less than the first time threshold. The first MG high-voltage application period B is the period from the start time to the end time of the first MG high-voltage application process. Because the sum of the first pre-torque period A and the first MG high-voltage application period B is less than the first time threshold, the high-voltage battery 26 is used safely.

[0057] <Cases where starting the motor 10 via the electric generator 12 fails due to timeout during the first starting process>

[0058] Reference Figure 6 The following explains the situation where the starting of the engine 10 by the electric generator 12 fails due to timeout during the first start-up process. During the execution of the first start-up process, the elapsed time from the start of the first start-up process exceeds a first time threshold, and the engine speed is less than an engine speed threshold. Therefore, the control device 34 determines that the starting of the engine 10 by the electric generator 12 has failed.

[0059] At time T20, control device 34 determines that the start-up conditions for engine 10 have been met. Control device 34 then begins engine start-up processing from time T20. Figure 6 In the example shown, the engine starting process only includes the first starting process.

[0060] Control device 34 performs the first pre-torque processing from time T20 to time T21. The first pre-torque processing is as described above.

[0061] Next, control device 34 begins the first MG high voltage application process from time T21. The first MG high voltage application process is as described above.

[0062] Next, at time T23, the control device 34 determines that the engine speed is less than the engine speed threshold and the elapsed time since the start of the first start-up process is greater than the first time threshold. Therefore, the control device 34 determines that the electric generator 12 has failed to start the engine 10. The control device 34 terminates the first MG high voltage application process. Furthermore, the control device 34 uses the starter 20 to start the engine 10.

[0063] <Successful starting of the motor 10 via the second starting process>

[0064] Reference Figure 7 The successful starting of the engine 10 by the electric generator 12 through the second starting process will be explained. Figure 7 In the example shown, during the execution of the second start-up process, the engine speed becomes above the engine speed threshold within the second time threshold, and thus the engine 10 is successfully started through the second start-up process.

[0065] At time T30, the control device 34 determines that the execution conditions for starting the engine 10 have been met. The control device 34 begins the engine starting process from time T30.

[0066] Control device 34 performs the first pre-torque processing from time T30 to time T31. The first pre-torque processing is as described above.

[0067] Next, control device 34 begins the first MG high-voltage application process from time T31. Regarding the first MG high-voltage application process, as described above. Control device 34 determines at time T32 that the engine speed has become less than 0. This means that the engine speed has become less than 0 due to the compressed air in the cylinder. Control device 34 terminates the first starting process and begins the second starting process based on the engine speed becoming less than 0. That is, the second starting process is executed on the condition that the engine speed became less than 0 during the first starting process. As described later, the second starting process includes torque removal processing, second pre-torque processing, and second MG high-voltage application processing.

[0068] Control device 34 performs torque removal processing from time T32 to time T33. Torque removal processing is the process of interrupting the power supply from high-voltage battery 26 to electric generator 12. The torque removal period C is set in such a way that the end time of torque removal period C coincides with the time when the engine speed switches from less than 0 to above 0. Torque removal period C means the period from the start to the end of torque removal processing. In other words, torque removal period C is the period during which the power supply from high-voltage battery 26 to electric generator 12 is interrupted during the second starting process, i.e., the interruption period.

[0069] The torque removal period C is variably set. The method for variably setting the torque removal period C will be explained. The electric generator 12 and the engine 10 are interconnected via belt 16. Immediately after time T32, the engine speed is negative. Therefore, immediately after time T32, the speed of the electric generator 12, i.e., the MG speed, is negative. The control device 34 predicts the end time of the torque removal period C based on the fact that the negative MG speed is greater than a negative threshold and that the MG speed is increasing. That is, the control device 34 predicts the end time of the torque removal period C based on the fact that the reverse rotation of the electric generator 12 gradually slows down and becomes slower than the threshold. Thus, the control device 34 sets the torque removal period C in a manner that makes the end time of the torque removal period C coincide with the time when the engine speed switches from less than 0 to above 0.

[0070] Control device 34 performs a second pre-torque process from time T33 to time T34. The second pre-torque process is the same as the first pre-torque process.

[0071] Control device 34 begins the second MG high voltage application process from time T34. The second MG high voltage application process is the same as the first MG high voltage application process. That is, the second MG high voltage application process is the process of supplying power from the high-voltage battery 26 to the electric generator 12 to drive the electric generator 12 in order to start the engine 10.

[0072] Control device 34 determines at time T35 that the engine speed is above the engine speed threshold. Control device 34 terminates the second MG high voltage application process based on the determination that the engine speed is above the engine speed threshold at time T35.

[0073] During the execution of the second start-up process, control device 34 monitors whether the elapsed time from the start time T30 of the first start-up process is below a second time threshold. The second time threshold is the sum of the first pre-torque period A, the torque removal period C, the second pre-torque period D, and the battery rated time BRT. The second pre-torque period D represents the period from the start to the end of the second pre-torque process. The second time threshold is greater than the first time threshold by the torque removal period C and the second pre-torque period D.

[0074] exist Figure 7 In the example shown, the sum of the first pre-torque period A, the first MG high-voltage application period B, the torque removal period C, the second pre-torque period D, and the second MG high-voltage application period E is less than the second time threshold. Therefore, the high-voltage battery 26 is used safely. Here, the second MG high-voltage application period E is the period from the start time of the second MG high-voltage application process to the end time.

[0075] <Cases where starting the motor 10 via the electric generator 12 fails due to timeout during the second starting process>

[0076] Reference Figure 8 This section explains the situation where the starting of the engine 10 by the electric generator 12 fails due to timeout during the second starting process. Figure 8 In the example shown, during the execution of the second start-up process, the elapsed time from the start of the first start-up process exceeds the second time threshold and the engine speed is less than the engine speed threshold. Therefore, the control device 34 determines that the electric generator 12 has failed to start the engine 10.

[0077] At time T40, control device 34 determines that the execution conditions for starting engine 10 have been met. Control device 34 begins engine starting processing from time T40.

[0078] Control device 34 performs the first pre-torque process from time T40 to time T41.

[0079] Next, control device 34 begins the first MG high voltage application process from time T41. At time T42, control device 34 determines that the engine speed has become less than 0. Based on the engine speed becoming less than 0, control device 34 ends the first start-up process and begins the second start-up process.

[0080] Control device 34 performs torque removal processing from time T42 to time T43. Control device 34 performs second pre-torque processing from time T43 to time T44.

[0081] Control device 34 begins the second MG high voltage application process at time T44. Then, at time T45, control device 34 determines that the engine speed is less than the engine speed threshold and the elapsed time since the start of the first start-up process is greater than the second time threshold. Therefore, control device 34 determines that the electric generator 12 has failed to start the engine 10. Control device 34 terminates the second MG high voltage application process. Furthermore, control device 34 uses starter 20 to start the engine 10.

[0082] <Flowchart of the process executed by control device 34>

[0083] Reference Figure 9 and Figure 10 To explain the processing performed by the control device 34. Figure 5 and Figure 6 The action shown corresponds to Figure 9 . Figure 7 and Figure 8 The action shown corresponds to Figure 9 and Figure 10 . Figure 9 The process shown begins when the start-up conditions of engine 10 are met. The engine start-up process includes a first start-up process. The first start-up process includes... Figure 9 The start of the first pre-torque treatment Figure 9 The first MG high voltage application process is a series of processes up to the end of the first starting process. Additionally, the engine starting process includes a second starting process executed if a transfer condition is met in the first starting process (step S906: Yes). The transfer condition is a logical OR condition where the engine speed becomes less than 0 and the engine speed remains at 0 for a specified period. The second starting process includes... Figure 10 The start of torque removal processing Figure 10 The series of processes up to the end of the second MG high voltage application process.

[0084] like Figure 9 As shown, in step S900, the control device 34 performs the first pre-torque processing. Next, in step S902, the control device 34 begins the first MG high-voltage application processing.

[0085] Next, in step S904, the control device 34 determines whether the elapsed time since the start of the first start-up process is below a first time threshold. If the control device 34 affirms the determination in step S904 (step S904: Yes), it proceeds to step S906. In step S906, the control device 34 determines whether the transfer condition is met. If the control device 34 negates the determination in step S906 (step S906: No), it proceeds to step S908. In step S908, the control device 34 determines whether the engine speed is above the engine speed threshold. If the control device 34 negates the determination in step S908 (step S908: No), it proceeds to step S904. During the period when the determination in step S904 is affirmative, the determination in step S906 is negative, and the determination in step S908 is negative, steps S904, S906, and S908 are repeated.

[0086] If the control device 34 determines "yes" in step S908 (step S908: Yes), it proceeds to step S910. In step S910, the control device 34 terminates the first MG high voltage application process. Then, the control device 34 terminates the current process. The case where the current process terminates by proceeding to step S910 corresponds to... Figure 5 The example shown.

[0087] If the control device 34 makes a negative determination in step S904 (step S904: No), it proceeds to step S912. In step S912, the control device 34 ends the first MG high voltage application process and starts the engine 10 using the starter 20. Then, the control device 34 ends the process. The case of entering step S912 and ending the process corresponds to... Figure 6 The example shown.

[0088] If the control device 34 confirms the condition in step S906 (step S906: Yes), it proceeds to step S914. In step S914, the control device 34 terminates the first MG high voltage application process. That is, the control device 34 terminates the first start-up process. Then, the control device 34 begins... Figure 10 The second startup process is shown.

[0089] like Figure 10 As shown, in step S916, control device 34 performs the torque removal process described above. Next, in step S918, control device 34 performs the second pre-torque process described above. Next, in step S920, control device 34 sets a second time threshold. As described above, the second time threshold is the sum of the first pre-torque period A, the torque removal period C, the second pre-torque period D, and the battery rated time BRT. As described above, the torque removal period C can be set variably.

[0090] Next, in step S922, control device 34 begins the second MG high voltage application process. Then, control device 34 proceeds to step S924.

[0091] In step S924, control device 34 determines whether the elapsed time since the start of the first start-up process is below a second time threshold. If control device 34 affirms the determination in step S924 (step S924: Yes), it proceeds to step S926. In step S926, control device 34 determines whether the engine speed is above the engine speed threshold. If control device 34 negates the determination in step S926 (step S926: No), it proceeds to step S924. During the period when the determination in step S924 is affirmative and the determination in step S926 is negative, steps S924 and S926 are repeated.

[0092] If the control device 34 determines "yes" in step S926 (step S926: Yes), it proceeds to step S928. In step S928, the control device 34 terminates the second MG high voltage application process. Then, the control device 34 terminates the current process. The case where the current process terminates by proceeding to step S928 corresponds to... Figure 7 The example shown.

[0093] If the control device 34 makes a negative determination in step S924 (step S924: No), it proceeds to step S930. In step S930, the control device 34 terminates the second MG high voltage application process and starts the engine 10 using the starter 20. Then, the control device 34 terminates the process. The case where the process terminates by proceeding to step S930 corresponds to... Figure 8 The example shown.

[0094] <Function and Effects of This Implementation Method>

[0095] (1) Sometimes, the control device 34 performs the first starting process, and the engine 10 starts successfully without performing the second starting process. In contrast, sometimes the engine 10 starts successfully by performing both the first and second starting processes by the control device 34. In the above structure, the control device 34 ends the first starting process and begins the second starting process when the logic OR condition that the engine speed becomes less than 0 and the engine speed remains at 0 for a specified period is met. This is because if the engine speed becomes less than 0 or the engine speed remains at 0 for a specified period during the execution of the first starting process, it can be considered that the engine 10 cannot be started even if the first starting process continues. In the above structure, compared with the structure that does not perform the second starting process, the chance of starting the engine 10 using the electric generator 12 can be increased.

[0096] Here, the reason why starting may sometimes be successful if the first starting process is ended and the second starting process is executed is explained. The engine 10 has a cylindrical piston 50 and piston rings 54 fitted into annular grooves 52 on the outer circumference of the piston 50. A large load is applied to the electric generator 12 because one cylinder is in the compression stroke and other cylinders are in the expansion stroke. During the execution of the first starting process, in the cylinder in the compression stroke, the piston rings 54 are pressed against the lower end of the annular grooves 52. If the first starting process is ended and the second starting process is executed, the power supply to the electric generator 12 is interrupted first. As a result, the piston 50 descends in the cylinder in the compression stroke. When the piston 50 descends, the piston rings 54 momentarily leave the lower end of the annular grooves 52, thus creating an air passage in the annular grooves 52. Through this air passage, compressed air escapes from the cylinder. Therefore, in the second starting process, compared to the first starting process, the repulsive force of the air in the cylinder in the compression stroke is smaller. Therefore, if the first startup process ends and the second startup process is executed, the startup may succeed.

[0097] like Figure 7 As shown, the time threshold for comparing the elapsed time from the start of the first start-up process differs between the execution of the first and second start-up processes. That is, a second time threshold larger than the first time threshold is set. The reason for setting a second time threshold larger than the first time threshold is explained. If, assuming a prolonged period of high-voltage power supply using the start-up of the electric generator 12, the high-voltage battery 26 may be damaged. The first and second time thresholds are set in a manner that can prevent damage to the high-voltage battery 26. In the second start-up process, there is a period during which the power supply from the high-voltage battery 26 to the electric generator 12 is interrupted. Therefore, a second time threshold larger than the first time threshold is set.

[0098] Consider the following comparative example: The failure to start the engine 10 by the electric generator 12 is determined based on the same elapsed period, without considering the period during which the power supply from the high-voltage battery 26 to the electric generator 12 is interrupted. In this comparative example, even though damage to the high-voltage battery 26 is avoided and the engine 10 is successfully started by performing a second starting procedure, it is possible to determine that the starting has failed.

[0099] In the above structure, a second time threshold is set that is larger than the first time threshold. Therefore, compared with the comparative example, the chance of starting the engine 10 using the electric generator 12 can be increased.

[0100] (2) At the start time of the second starting process, one cylinder is in the compression stroke, while the other cylinders are in the expansion stroke. The second starting process is executed conditionally, provided that the engine speed becomes less than 0 during the first starting process and the engine speed remains at 0 for a specified period. If the second starting process is executed when the engine speed becomes less than 0 during the first starting process, the engine speed is negative at the start time of the torque removal period C. If the second starting process is executed when the engine speed remains at 0 for a specified period during the first starting process, the engine speed becomes negative immediately after the start of the torque removal period C due to the air repulsion force. Therefore, during the torque removal period C, air expands in the cylinders in the compression stroke and is compressed in the cylinders in the expansion stroke. Shortly afterward, the engine speed becomes 0 due to the force of the compressed air in the cylinders in the expansion stroke pressing down on the piston 50.

[0101] In the above structure, the end time of the torque removal period C is set to coincide with the time when the engine speed switches from less than 0 to above 0. After the torque removal period C ends, the control device 34 supplies power from the high-voltage battery 26 to the electric generator 12 to drive the electric generator 12 in order to start the engine 10. Immediately after the engine speed switches from less than 0 to above 0, the piston 50 in the cylinder, which is in the expansion stroke, is pushed down by compressed air. That is, the compressed air helps the engine 10 rotate in the forward direction. Therefore, compared with the structure that starts the engine 10 from the time when the engine speed is negative, the engine 10 can be started more effectively.

[0102] (3) Consider a structure where the control device 34 determines the end time of the torque removal period C based on the rotational speed of the electric generator 12 being 0, which differs from the structure described above. In this structure, it is difficult to make the end time of the torque removal period C coincide with the time when the engine speed switches from less than 0 to above 0. In contrast, in the structure described above, the control device 34 predicts the end time of the torque removal period C based on the fact that the rotational speed of the negative electric generator 12 is greater than a negative threshold before becoming 0. Therefore, it is easier to make the end time of the torque removal period C coincide with the time when the engine speed switches from less than 0 to above 0.

[0103] <Example of Change>

[0104] This embodiment can be modified as follows. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0105] The structure of vehicle 100 can be modified appropriately. In the above embodiment, the number of cylinders is four. However, this is merely an example. The number of cylinders can be modified appropriately, for example, it could be six.

[0106] In the above embodiment, no clutch is provided that can connect or disconnect the engine 10 and the crankshaft pulley 10a. However, a clutch may be provided between the engine 10 and the crankshaft pulley 10a.

[0107] In the above embodiment, the high-voltage battery 26 and the low-voltage battery 28 are mounted on the vehicle 100. However, this is merely an example. Any battery capable of supplying power to the electric generator 12 can be mounted on the vehicle 100.

[0108] • The combustion cycle can be modified appropriately. In the above embodiment, the air-fuel mixture is ignited in the order of cylinder #1, cylinder #3, cylinder #4, and cylinder #2. The air-fuel mixture can also be ignited in the order of cylinder #1, cylinder #2, cylinder #4, and cylinder #3.

[0109] In the above embodiment, the transition condition is a logical OR condition where the engine speed becomes less than 0 and the engine speed remains at 0 for a specified period. Alternatively, the transition condition can also be a condition that means the engine speed becomes less than 0. That is, the determination of whether the engine speed remains at 0 for a specified period can be omitted.

[0110] In the above embodiment, the first time threshold is the sum of the first pre-torque period A and the battery rated time BRT. The second time threshold is the sum of the first pre-torque period A, the torque removal period C, the second pre-torque period D, and the battery rated time BRT. However, this is merely an example. The first and second time thresholds only need to satisfy the requirement that damage to the battery capable of supplying power to the electric generator 12 can be avoided, and that the second time threshold is greater than the first time threshold.

[0111] • In the above embodiment, the torque removal period C can be set variably. The torque removal period C can also be a fixed value.

[0112] In the above embodiment, the control device 34 predicts the end time of the torque removal period C based on the fact that the negative MG speed is greater than a negative threshold and the MG speed is increasing. However, this is merely an example. For instance, the control device 34 could also determine the end time of the torque removal period C based on the fact that the crankshaft reversal angle exceeds a threshold. The control device 34 could also determine the end time of the torque removal period C based on the fact that the elapsed time from the time the crankshaft begins to reverse exceeds a threshold.

[0113] In the above embodiments, the control device 34 includes a CPU, ROM, and RAM, and performs software processing. However, this is merely an example. For instance, the control device 34 may also include dedicated hardware circuitry (e.g., an ASIC) for processing at least a portion of the software processing performed in the above embodiments. That is, the control device 34 can be any of the following structures (a) to (c): (a) The control device 34 includes a processing device for executing all processing according to a program and a program storage device such as a ROM for storing the program. That is, the control device 34 includes a software execution device. (b) The control device 34 includes a processing device for executing a portion of the processing according to a program and a program storage device. Furthermore, the control device 34 includes dedicated hardware circuitry for executing the remaining processing. (c) The control device 34 includes dedicated hardware circuitry for executing all processing. Here, there may be multiple software execution devices and / or dedicated hardware circuitry. That is, the above processing can be executed by a processing circuitry that includes at least one of the software execution device and dedicated hardware circuitry. There may also be multiple software execution devices and dedicated hardware circuitry included in the processing circuitry. Program storage devices, or computer-readable media, include all media that can be accessed using a general-purpose or special-purpose computer.

Claims

1. A control device for a hybrid vehicle, the hybrid vehicle comprising an engine and an electric generator interconnected via a belt, a battery configured to supply power to the electric generator, and a starter configured to start the engine, wherein, The control device includes a processing circuit. The processing circuit is configured to perform engine starting processing when the engine starting conditions are met. The engine starting process includes: The first start-up process involves supplying power from the battery to the electric generator to drive the electric generator in order to start the engine; and The second start-up process is executed on the condition that the engine speed (i.e., the engine rotation speed) becomes less than 0 in the first start-up process and the engine speed remains at 0 for a specified period, i.e., the transfer condition, is met. The second starting process includes supplying power from the battery to the electric generator to drive the electric generator in order to start the engine after the power supply from the battery to the electric generator is interrupted. The processing circuit is configured such that, during the execution of the first start-up process, if the elapsed time from the start of the first start-up process exceeds a first time threshold and the engine speed is less than an engine speed threshold, it is determined that the electric generator has failed to start the engine. The processing circuit is configured such that, during the execution of the second start-up process, if the elapsed time exceeds a second time threshold and the engine speed is less than the engine speed threshold, it is determined that the electric generator has failed to start the engine. The second time threshold is greater than the first time threshold. The processing circuit is configured to start the engine using the starter if the electric generator fails to start the engine. In the second start-up process, the period during which the power supply from the battery to the electric generator is interrupted, i.e., the interruption period, is set in such a way that the end time of the interruption period coincides with the time when the engine speed switches from less than 0 to more than 0.

2. The control device for a hybrid vehicle according to claim 1, The processing circuit is configured to predict the end time point of the interruption period based on the fact that the negative rotational speed of the electric generator is greater than a negative threshold and the rotational speed of the electric generator is increasing.

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