Drive control device

Abstract

To suppress the deterioration of exhaust characteristics of an internal combustion engine when split injection is performed during engine startup. [Solution] The drive unit 20 to which the drive control device 70 is applied includes an internal combustion engine 30 having a direct injection injector 32 that injects fuel into a cylinder 31, and a first motor generator 41 connected to the crankshaft 33 of the internal combustion engine 30. When the internal combustion engine 30 is started, the drive control device 70 performs a divided injection process in which the fuel injection of the direct injection injector 32 is divided into multiple injections during one combustion cycle of the internal combustion engine 30. When the divided injection process is performed, a suppression process is performed in which the drive unit 20 is operated so that the engine speed does not exceed an upper limit of the engine speed corresponding to the number of divisions of the fuel injection of the direct injection injector 32.

Description

Technical Field

[0001] The present invention relates to a drive control device applied to a drive device including an internal combustion engine and a motor generator.

Background Art

[0002] Patent Document 1 discloses a control device that executes a split injection process for dividing fuel injection of a direct injection injector into a plurality of times during cold start of an internal combustion engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The direct injection injector operates by being supplied with power from a capacitor. Therefore, when operating the direct injection injector by the split injection process as described above, power supply from the capacitor to the direct injection injector is performed several times during one combustion cycle of the internal combustion engine. And every time the power supply from the capacitor to the direct injection injector ends, charging of the capacitor by power supply from the battery is performed. If the charging time of the capacitor at this time is short, at the time of the next operation of the direct injection injector, appropriate power supply from the capacitor to the direct injection injector may not be performed, and thus the controllability of fuel injection of the direct injection injector may deteriorate. Therefore, the upper limit value of the engine speed during execution of the split injection process is determined by the number of divisions of fuel injection of the direct injection injector and the charging ability of the capacitor.

[0005] When starting an internal combustion engine, the motor-generator drives the engine speed, and the fuel-air mixture, including fuel injected into the cylinder from the direct injection injector, is burned. This can cause the engine speed to increase. If the engine speed exceeds the upper limit due to this increase in engine speed, the time interval between consecutive fuel injections becomes shorter. As a result, the next fuel injection occurs before the condenser is sufficiently charged, reducing the controllability of the fuel injection amount by the direct injection injector. Consequently, the combustion state in the internal combustion engine changes, which can worsen the exhaust characteristics of the internal combustion engine. [Means for solving the problem]

[0006] The drive control device for solving the above problems is applied to a drive system comprising an internal combustion engine equipped with a direct injection injector for injecting fuel into a cylinder, and a motor generator connected to the crankshaft of the internal combustion engine. The drive control device includes a processing circuit that, when the internal combustion engine is started, performs a divided injection process that divides the fuel injection of the direct injection injector into multiple injections during one combustion cycle of the internal combustion engine, and a suppression process that, when the divided injection process is performed, operates the drive system so that the engine speed does not exceed an upper limit of engine speed corresponding to the number of divisions of fuel injection of the direct injection injector. [Effects of the Invention]

[0007] To suppress the deterioration of exhaust characteristics of an internal combustion engine when split injection is performed during engine startup. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a hybrid vehicle comprising a drive control device according to the first embodiment and a drive device controlled by the drive control device. [Figure 2] Figure 2 is a flowchart showing a series of processes performed by the first processing circuit of the drive control device shown in Figure 1. [Figure 3]Figure 3 is a flowchart showing a series of processes performed by the second processing circuit of the drive control device shown in Figure 1. [Figure 4] Figure 4 is a flowchart showing a portion of the series of processes performed by the first processing circuit in the drive control device of the second embodiment. [Modes for carrying out the invention]

[0009] (First Embodiment) A first embodiment of the drive control device will be described with reference to Figures 1 to 3. Figure 1 illustrates a hybrid vehicle 10 equipped with a drive control device 70. The hybrid vehicle 10 further comprises a drive unit 20 to which the drive control device 70 is applied, and a plurality of drive wheels 11 to which the output of the drive unit 20 is transmitted.

[0010] <Drive unit 20> The drive unit 20 includes an internal combustion engine 30, a power split mechanism 40, a first motor generator 41, a second motor generator 42, and a reduction mechanism 43.

[0011] The internal combustion engine 30 comprises a plurality of cylinders 31, a plurality of direct injection injectors 32 corresponding to each of the plurality of cylinders 31, and a crankshaft 33. The plurality of direct injection injectors 32 inject fuel into the corresponding cylinders 31. Inside the plurality of cylinders 31, a mixture containing the fuel injected from the corresponding direct injection injectors 32 and air is burned. The power generated by the combustion of the mixture causes the pistons inside the plurality of cylinders 31 to reciprocate, thereby rotating the crankshaft 33.

[0012] An example of the power split mechanism 40 is a planetary gear mechanism. The crankshaft 33 of the internal combustion engine 30 and the output shaft of the first motor generator 41 are connected to the power split mechanism 40. Therefore, the output from the power split mechanism 40 can be controlled by adjusting the output of the internal combustion engine 30 and the output of the first motor generator 41. In addition, the output shaft of the first motor generator 41 is connected to the crankshaft 33 via the power split mechanism 40. Therefore, the first motor generator 41 can adjust the rotational speed of the crankshaft 33.

[0013] The output of the power split mechanism 40 is transmitted to the multiple drive wheels 11 via the reduction mechanism 43. The output shaft of the second motor generator 42 is connected to the reduction mechanism 43. Therefore, the output of the second motor generator 42 is also transmitted to the multiple drive wheels 11 via the reduction mechanism 43.

[0014] The drive unit 20 further comprises a first power control unit 51 and a second power control unit 52. The first motor generator 41 is connected to the battery via the first power control unit 51. The second motor generator 42 is connected to the battery via the second power control unit 52. When the motor generators 41 and 42 are used as electric motors, the DC voltage of the battery is converted to AC voltage by the power control units 51 and 52 and supplied to the motor generators 41 and 42. On the other hand, when the motor generators 41 and 42 are used as generators, the AC voltage generated by the motor generators 41 and 42 is converted to DC voltage by the power control units 51 and 52 and supplied to the battery.

[0015] <Drive control device 70> The drive control device 70 includes processing circuits for controlling the internal combustion engine 30 and a plurality of motor generators 41, 42. These processing circuits include a first processing circuit 71 and a second processing circuit 75. The plurality of processing circuits 71, 75 are capable of sending and receiving various types of information and commands from each other.

[0016] An example of the processing circuits 71 and 75 is an electronic control unit. The first processing circuit 71 includes a CPU 72 and a memory 73 that stores a control program executed by the CPU 72. The second processing circuit 75 includes a CPU 76 and a memory 77 that stores a control program executed by the CPU 76. When the CPU 72 executes the control program in the memory 73, the first processing circuit 71 can control the operation of the internal combustion engine 30. When the CPU 76 executes the control program in the memory 77, the second processing circuit 75 can control the plurality of motor generators 41 and 42.

[0017] In the drive control device 70, when starting the internal combustion engine 30, the second processing circuit 75 drives the first motor generator 41 to rotate the crankshaft 33 of the internal combustion engine 30, and the first processing circuit 71 executes split injection processing. The split injection processing is a process of splitting the fuel injection of the direct injection injector 32 into N times during one combustion cycle of the internal combustion engine 30. "N" is an integer of 2 or more.

[0018] Here, the direct injection injector 32 operates by being supplied with power from a capacitor to its solenoid. The capacitor is a power supply source for the direct injection injector 32. When the power supply from the capacitor to the direct injection injector 32 ends, power is supplied from the in-vehicle battery to charge the capacitor. If power is supplied from the capacitor to the direct injection injector 32 when the charge amount of the capacitor is not sufficient, the direct injection injector 32 may not operate properly. That is, the controllability of the fuel injection amount of the direct injection injector 32 may decrease.

[0019] Therefore, when the split injection process is executed at the start of the internal combustion engine 30, an upper limit value NEL of the engine speed NE, which is the rotational speed of the crankshaft 33, is set. The upper limit value NEL is set to an engine speed corresponding to the number of splits N of fuel injection in the split injection process. Specifically, the upper limit value NEL is set such that the larger the number of splits N, the lower the upper limit value NEL. If the engine speed NE exceeds the upper limit value NEL during the execution of the split injection process, the temporal interval of consecutive fuel injections becomes shorter, and thus there is a risk that the next fuel injection may start before the capacitor is fully charged. In this case, since the fuel injection amount of the direct injection injector 32 cannot be appropriately controlled, the combustion state in the internal combustion engine 30 may change.

[0020] Therefore, when the split injection process is executed at the start of the internal combustion engine 30, the drive control device 70 executes a suppression process for operating the drive device 20 so that the engine speed NE does not exceed the upper limit value NEL.

[0021] Referring to FIG. 2, a series of processes executed by the first processing circuit 71 at the start of the internal combustion engine 30 are executed. The first processing circuit 71 executes a series of processes shown in FIG. 2 when the execution condition of the split injection process is satisfied at the start of the internal combustion engine 30.

[0022] In step S11, the first processing circuit 71 starts the split injection process. In the subsequent step S13, the first processing circuit 71 performs a prediction process to predict whether the engine speed NE will exceed the upper limit NEL when performing the split injection process, based on the engine speed NE and the rate at which the engine speed NE is increasing. For example, the first processing circuit 71 calculates a predicted engine speed NEa, which is the predicted value of the engine speed NE at a predetermined time after a predetermined time has elapsed from the present, based on the engine speed NE and the rate at which the engine speed NE is increasing. An example of a predetermined time is the cycle time, which is the time required for one combustion cycle of the internal combustion engine 30. If the predicted engine speed NEa is higher than the upper limit NEL, it is assumed that the engine speed NE will exceed the upper limit NEL during the execution of the split injection process. On the other hand, if the predicted engine speed NEa is less than or equal to the upper limit NEL, it is assumed that the engine speed NE will not exceed the upper limit NEL during the execution of the split injection process.

[0023] In the next step S15, if the first processing circuit 71 predicts that the engine speed NE will exceed the upper limit NEL in the prediction process (S15: YES), the first processing circuit 71 proceeds to step S17. On the other hand, if the first processing circuit 71 predicts that the engine speed NE will not exceed the upper limit NEL in the prediction process (S15: NO), the first processing circuit 71 proceeds to step S19.

[0024] In step S17, the first processing circuit 71 sends a generation request to the second processing circuit 75, which is a request to generate negative torque in the first motor generator 41. Then, the first processing circuit 71 proceeds to step S19.

[0025] In step S19, the first processing circuit 71 determines whether or not the internal combustion engine 30 has finished starting. For example, the first processing circuit 71 can determine that the internal combustion engine 30 has finished starting when the combustion of the internal combustion engine 30 has reached a stable, fully combusted state. If the first processing circuit 71 determines that the internal combustion engine 30 has finished starting (S19: YES), the first processing circuit 71 proceeds to step S21. On the other hand, if the first processing circuit 71 determines that the internal combustion engine 30 has not finished starting (S19: NO), the first processing circuit 71 proceeds to step S13.

[0026] In step S21, the first processing circuit 71 notifies the second processing circuit 75 that the starting of the internal combustion engine 30 is complete. In the following step S23, the first processing circuit 71 completes the split injection process. After that, the first processing circuit 71 completes the series of processes shown in Figure 2.

[0027] From this point onward, the first processing circuit 71 operates multiple direct injection injectors 32, for example, to satisfy the required injection amount with a single fuel injection. Referring to Figure 3, the second processing circuit 75 executes a series of processes when the internal combustion engine 30 is started. The second processing circuit 75 executes the series of processes shown in Figure 3 when starting the internal combustion engine 30.

[0028] In step S31, the second processing circuit 75 starts a cranking process in which the crankshaft 33 is rotated by the drive of the first motor generator 41. In the following step S33, the second processing circuit 75 determines whether or not it has received the generation request from the first processing circuit 71. If the second processing circuit 75 has received the generation request (S33: YES), the second processing circuit 75 proceeds to step S35. On the other hand, if the second processing circuit 75 has not received the generation request (S33: NO), the second processing circuit 75 performs the cranking process and proceeds to step S37.

[0029] In step S35, the second processing circuit 75 executes a negative torque generation process that generates a negative torque in the first motor generator 41. The negative torque generated by the first motor generator 41 is a torque that suppresses the rise of the crankshaft 33. In other words, the negative torque generation process is an example of a "suppression process" that operates the drive unit 20 so that the engine speed NE does not exceed the upper limit NEL. After that, the second processing circuit 75 moves on to step S37.

[0030] In step S37, the second processing circuit 75 determines whether or not it has received a message from the first processing circuit 71 indicating that the internal combustion engine 30 has started up. If the second processing circuit 75 has received a message indicating that the internal combustion engine 30 has started up (S37: YES), the second processing circuit 75 proceeds to step S39. On the other hand, if the second processing circuit 75 has not received a message indicating that the internal combustion engine 30 has started up (S37: NO), the second processing circuit 75 proceeds to step S33.

[0031] In step S39, the second processing circuit 75 terminates the process it was performing (cranking process or negative torque generation process). After that, the second processing circuit 75 terminates the series of processes shown in Figure 3.

[0032] <Operation and Effects of This Embodiment> (1-1) In the drive control device 70, when split injection processing is performed when the internal combustion engine 30 is started, a suppression process is performed to drive the drive device 20 so that the engine speed NE does not exceed the upper limit NEL. This suppresses the occurrence of engine speed surge, which is a phenomenon in which the engine speed NE rises to exceed the upper limit NEL when split injection processing is performed. As a result, even when split injection processing is being performed, the fuel injection amount of the direct injection injector 32 is appropriately controlled. Therefore, the drive control device 70 can suppress deterioration of the exhaust characteristics of the internal combustion engine 30 when split injection processing is performed when the internal combustion engine 30 is started.

[0033] (1-2) In the drive control device 70, when the split injection process is performed, a prediction process is performed to predict whether the engine speed NE will exceed the upper limit NEL, based on the engine speed NE and the rate at which the engine speed NE increases. If the prediction process predicts that the engine speed NE will exceed the upper limit NEL, a suppression process is performed. As a result, the drive control device 70 can perform the suppression process even before the engine speed NE exceeds the upper limit NEL.

[0034] (1-3) In the drive control device 70, a negative torque generation process is performed as a suppression process to generate negative torque in the first motor generator 41. As a result, the drive control device 70 can suppress the engine speed NE from exceeding the upper limit NEL without changing the fuel injection control mode (for example, the total injection amount or the number of divisions N) during the starting of the internal combustion engine 30.

[0035] (Second Embodiment) A second embodiment of the drive control device will be described with reference to Figure 4. The second embodiment differs from the first embodiment in a part of the processing content of the first processing circuit when the internal combustion engine is started. In the following description, the parts that differ from the first embodiment will be mainly described, and the same reference numerals will be used for components that are the same as or equivalent to those in the first embodiment, and redundant explanations will be omitted.

[0036] Referring to Figure 4, the following will explain the differences between the first embodiment and the first embodiment in the series of processes performed by the first processing circuit 71 when the internal combustion engine 30 is started. When the first processing circuit 71 starts the segmented injection process in step S11, it moves the process to step S13. In step S13, the first processing circuit 71 performs a prediction process. If the first processing circuit 71 predicts in the prediction process that the engine speed NE will exceed the upper limit NEL (S15: YES), the first processing circuit 71 moves the process to step S17. On the other hand, if the first processing circuit 71 predicts in the prediction process that the engine speed NE will not exceed the upper limit NEL (S15: NO), the first processing circuit 71 moves the process to step S19.

[0037] In step S17, the first processing circuit 71 transmits the above generation request to the second processing circuit 75. In the subsequent step S18, the first processing circuit 71 performs a process to reduce the total injection amount of the direct injection injector 32. In this reduction process, the first processing circuit 71 reduces the total amount of fuel injected by the direct injection injector 32 during one combustion cycle of the internal combustion engine 30 without changing the number of divisions N. By reducing the total amount in this way, the increase in the output torque of the internal combustion engine 30 is suppressed, and thus the increase in engine speed NE is suppressed. In other words, this reduction process is an example of a "suppression process" that operates the drive unit 20 so that the engine speed NE does not exceed the upper limit NEL. After that, the first processing circuit 71 moves the process to step S19.

[0038] Since the processing flow from step S19 onward is the same as in the first embodiment, a detailed explanation will be omitted. <Operation and Effects of This Embodiment> In this embodiment, in addition to the effects (1-1) to (1-3) of the first embodiment described above, the following effects can be further obtained.

[0039] (2-1) In the drive control device 70 of this embodiment, the reduction process is performed when the split injection process is performed when the internal combustion engine 30 is started. In this reduction process, the first processing circuit 71 of the drive control device 70 reduces the total amount of fuel injected by the direct injection injector 32 during one combustion cycle of the internal combustion engine 30 without changing the number of divisions N. This suppresses the output torque of the internal combustion engine 30 from becoming too large in an attempt to increase the engine speed NE. Therefore, the drive control device 70 can suppress the engine speed NE from exceeding the upper limit NEL.

[0040] (Example of change) The above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0041] In the second embodiment described above, if the first processing circuit 71 performs a reduction process, the second processing circuit 75 does not need to perform a negative torque generation process. Furthermore, if the reduction process can prevent the engine speed NE from exceeding the upper limit NEL during engine startup, the drive system to which the drive control device 70 is applied may be configured to include only the internal combustion engine among the internal combustion engine and motor generator.

[0042] In the above embodiments, the prediction of whether the engine speed NE exceeds the upper limit NEL was performed by the first processing circuit 71, but this is not limited to this. For example, the second processing circuit 75 may perform the above prediction. In this case, the first processing circuit 71 appropriately transmits information regarding the number of divisions N and the engine speed NE to the second processing circuit 75.

[0043] The drive system may have a different configuration from the drive system 20 shown in Figure 1, as long as it includes an internal combustion engine 30 and a motor generator connected to the crankshaft 33 of the internal combustion engine 30.

[0044] The drive control device 70 is not limited to one that includes a CPU and ROM and performs software processing. In other words, the drive control device 70 may have any of the following configurations: (a), (b), and (c).

[0045] (a) The drive control device 70 includes one or more processors that perform various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0046] (b) The drive control device 70 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit," and FPGA is an abbreviation for "Field Programmable Gate Array."

[0047] (c) The drive control device 70 comprises one or more processors that execute a portion of the various processes according to a computer program, and one or more dedicated hardware circuits that execute the remaining processes of the various processes. [Explanation of Symbols]

[0048] 20...Drive unit, 30...Internal combustion engine, 31...Cylinder, 32...Direct injection injector, 33...Crankshaft, 41...First motor generator, 42...Second motor generator, 70...Drive control device, 71,75...Processing circuit.

Claims

1. This is applied to a drive system comprising an internal combustion engine equipped with a direct injection injector that injects fuel into the cylinder, and a motor generator connected to the crankshaft of the internal combustion engine. During the startup of the internal combustion engine, a segmented injection process is performed in which the fuel injection of the direct injection injector is divided into multiple injections during one combustion cycle of the internal combustion engine. When performing the split injection process, the system includes a processing circuit that performs a suppression process to operate the drive unit so that the engine speed does not exceed an upper limit of the engine speed corresponding to the number of fuel injection divisions of the direct injection injector. Drive control device.

2. The aforementioned processing circuit is When performing the split injection process, a prediction process is performed to predict whether the engine speed will exceed the upper limit, based on the engine speed and the rate at which the engine speed increases. The suppression process is executed when it is predicted that the engine speed will exceed the upper limit. The drive control device according to claim 1.

3. The processing circuit generates a negative torque in the motor generator during the suppression process, which is a torque that suppresses the increase in engine speed. The drive control device according to claim 1 or claim 2.

4. The processing circuit reduces the total amount of fuel injected by the direct injection injector during one combustion cycle of the internal combustion engine without changing the number of divisions in the suppression process. The drive control device according to claim 1 or claim 2.

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