Vehicle control device

Abstract

To provide a control unit of a vehicle which can perform a split injection of fuel.SOLUTION: A control unit of a vehicle having a fuel injection valve driven with a voltage charged in a capacitor, includes an acquisition part which acquires the voltage of the capacitor, and an injection control part which controls the number of times of injections of fuel from the fuel injection valve into an internal combustion engine on the basis of the voltage of the capacitor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] A fuel injector supplies fuel to an internal combustion engine. A technique for driving the fuel injector by energy stored in a capacitor is known (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-013430 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, the ignition timing may be retarded to warm up the catalyst. Retarding the ignition timing can reduce torque. Increasing the amount of air introduced into the internal combustion engine and increasing the engine speed increases torque during warm-up control. Split fuel injection is performed to reduce emissions and improve fuel economy. Split injection involves multiple fuel injections from the fuel injection valve.

[0005] A fuel injection valve is driven by energy stored in a capacitor. Driving the fuel injection valve reduces the voltage of the capacitor. The voltage is increased by charging the capacitor after each fuel injection. However, increasing the engine speed and the number of injections shortens the time it takes to charge the capacitor. This reduces the voltage, making split injection difficult. Therefore, the objective of this invention is to provide a vehicle control device that can perform split fuel injection. [Means for solving the problem]

[0006] The object is to provide a control device for a vehicle having a fuel injection valve that is driven by a voltage charged in a capacitor, the control device including: an acquisition unit that acquires the voltage of the capacitor; and an injection control unit that controls the number of injections of fuel from the fuel injection valve to an internal combustion engine based on the voltage of the capacitor. and a setting unit that sets a target value of the number of injections of fuel from the fuel injection valve to the internal combustion engine, wherein when the voltage of the capacitor is equal to or higher than a first threshold, the injection control unit sets the number of injections to the target value, when the voltage of the capacitor is lower than a second threshold, the injection control unit sets the number of injections to be less than the number of previous injections, when the voltage of the capacitor is equal to or higher than the second threshold and lower than a third threshold, the injection control unit sets the number of injections to be equal to the number of previous injections, and when the voltage of the capacitor is equal to or higher than the third threshold and lower than the first threshold, the injection control unit sets the number of injections to be greater than the number of previous injections. This can be achieved by the vehicle's control device.

[0007] The acquisition unit may acquire the voltage of the capacitor after one of the fuel injection valves injects fuel and before the other of the fuel injection valves injects fuel.

[0009] The vehicle may be provided with a rotation speed control unit that controls the rotation speed of the internal combustion engine, and the vehicle is provided with a catalyst that purifies exhaust gas from the internal combustion engine, and the rotation speed control unit increases the rotation speed when warming up the catalyst compared to when warming up is not performed, and the injection control unit controls the number of injections of fuel from the fuel injection valve to the internal combustion engine based on the voltage of the capacitor when warming up the catalyst.

[0010] The injection control unit may control the number of injections of fuel from the fuel injection valve to the internal combustion engine based on the rotation speed of the internal combustion engine and the voltage of the capacitor. [Effects of the Invention]

[0011] A vehicle control device capable of performing split fuel injection can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a vehicle according to the first embodiment. [Figure 2] FIG. 2 is a flowchart illustrating the processing in the first embodiment. [Figure 3] 3(a) and 3(b) are diagrams illustrating time charts. [Figure 4]Fig. 4(a) is a diagram illustrating a flowchart in the second embodiment, and Fig. 4(b) is a diagram illustrating the number of injections. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment 1 is a schematic diagram of a vehicle 1 according to a first embodiment. The vehicle 1 is, for example, a plug-in hybrid vehicle. The vehicle 1 has an internal combustion engine (engine) 10, batteries 20 and 24, a DC (Direct Current) converter 22, a drive circuit 25, an engine ECU (Electronic Control Unit) 30 (ENG-ECU), and a hybrid ECU (HEV-ECU) 40.

[0014] The engine 10 burns fuel such as gasoline to output torque. The vehicle 1 runs on the torque output by the engine 10 and the torque output by an electric motor (motor generator, MG) (not shown).

[0015] The engine 10 is, for example, a four-cylinder engine. An intake passage 12 and an exhaust passage 14 are connected to the four cylinders of the engine 10. Air flows through the intake passage 12 and is supplied to the cylinders of the engine 10. A throttle valve 13 is provided in the intake passage 12. The larger the opening of the throttle valve 13, the greater the amount of air supplied to the engine 10. The smaller the opening, the less air is supplied.

[0016] Each of the four cylinders of the engine 10 is provided with a spark plug 16 and a fuel injection valve 18. The fuel injection valve 18 injects fuel directly into the cylinder. In the cylinder, the fuel and air form a mixture. The spark plug 16 ignites the mixture, causing it to burn. The exhaust gas after combustion passes through the exhaust passage 14 and is discharged to the outside of the vehicle 1.

[0017] A catalyst 15 is provided in the exhaust passage 14. The catalyst 15 is, for example, a three-way catalyst, and purifies nitrogen oxides (NOx), carbon monoxide (CO), and the like in the exhaust gas.

[0018] The vehicle 1 is provided with two batteries 20 and 24. The batteries 20 and 24 are secondary batteries such as nickel-metal hydride batteries or lithium-ion batteries. The battery 20 is the main battery. An MG (not shown) is driven by the power of the battery 20. The battery 20 is charged by the power generated by the MG. The battery 24 supplies power to, for example, auxiliary equipment and a drive circuit 25. The auxiliary equipment includes lights, an air conditioner, etc.

[0019] The batteries 20 and 24 are electrically connected to a DC-DC converter 22. The DC-DC converter 22 increases or decreases the output voltage of the battery 20 and supplies it to the battery 24.

[0020] The drive circuit 25 is electrically connected to the plurality of fuel injection valves 18 and drives the fuel injection valves 18. The drive circuit 25 has a capacitor 26. The capacitor 26 is charged by the voltage output by the battery 24. The fuel injection valves 18 are driven by the voltage stored in the capacitor 26. The capacitor 26 discharges, and electricity is passed through, for example, a coil (not shown). When electricity is passed through the coil, the valve body of the fuel injection valve 18 moves, the fuel injection valve 18 opens, and fuel is injected.

[0021] The temperature sensor 32 detects, for example, the temperature of the cooling water of the engine 10. The rotation speed sensor 34 detects the rotation speed of the engine 10.

[0022] The ENG-ECU 30 and the HEV-ECU 40 are control devices for the vehicle 1. Each of the ENG-ECU 30 and the HEV-ECU 40 includes an arithmetic unit such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ENG-ECU 30 and the HEV-ECU 40 perform various controls by executing programs stored in the ROM and the storage device.

[0023] The ENG-ECU 30 controls the engine 10. The ENG-ECU 30 controls the opening of the throttle valve 13. The ENG-ECU 30 controls the ignition timing of the spark plug 16. The ENG-ECU 30 functions as a rotation speed control unit that controls the rotation speed of the engine 10.

[0024] The HEV-ECU 40 controls the batteries 20 and 24 and the DCDC converter 22. The HEV-ECU 40 controls the output voltage of the battery 20. The HEV-ECU 40 controls the voltage supplied from the DCDC converter 22 to the battery 24. The HEV-ECU 40 controls the voltage supplied from the battery 24 to the capacitor 26. The ENG-ECU 30 stores thresholds for the voltage of the capacitor 26. There are three thresholds, for example, Va (first threshold), Vb (third threshold), and Vc (second threshold). Of the three thresholds, Va is the largest. Vb is smaller than Va and larger than Vc. Of the three thresholds, Vc is the smallest.

[0025] The ENG-ECU 30 functions as an acquisition unit that acquires the voltage of the capacitor 26. The ENG-ECU 30 functions as a setting unit that sets a target value for the number of fuel injections. The ENG-ECU 30 functions as an injection control unit that controls the timing and number of discharges of the capacitor 26 and the timing and number of injections of the fuel injection valve 18.

[0026] The exhaust purification performance of the catalyst 15 depends on temperature. When the temperature is low, for example, around 0°C, purification performance decreases. To improve purification performance, warm-up control of the catalyst 15 is performed. The ENG-ECU 30 raises the temperature of the catalyst 15 by retarding the ignition timing. Retarding the ignition timing may reduce torque. The ENG-ECU 30 increases the amount of air introduced into the engine 10 and increases the engine 10 rotation speed, thereby increasing torque. During warm-up control, split fuel injection is performed to reduce exhaust emissions and improve fuel efficiency. The ENG-ECU 30 sets the target value of fuel injection for each cylinder to, for example, four times.

[0027] 2 is a flowchart illustrating the processing in the first embodiment. The ENG-ECU 30 determines whether or not warm-up control of the catalyst 15 is being performed (step S10). If the determination is negative (No), the processing ends. For example, if the temperature of the cooling water is equal to or lower than a predetermined temperature, warm-up control is performed. If the determination is positive (Yes) in step S10, the ENG-ECU 30 obtains the voltage V of the capacitor 26 and determines whether or not the voltage V is less than a threshold value Va (step S12). If the determination is negative (No) in step S12, that is, if the voltage V is equal to or higher than the threshold value Va, the ENG-ECU 30 sets the number of injections to a target value (step S14).

[0028] If the determination in step S12 is affirmative (Yes), i.e., if the voltage V is less than the threshold value Va, the ENG-ECU 30 determines whether the voltage V is less than the threshold value Vc (step S16). If the determination is affirmative, i.e., if the voltage V is less than the threshold value Vc, the ENG-ECU 30 reduces the number of injections by one (step S18). The lower limit of the number of injections is one.

[0029] If the determination in step S16 is negative, i.e., if the voltage V is equal to or greater than the threshold value Vc, the ENG-ECU 30 determines whether the voltage V is equal to or greater than the threshold value Vb (step S20). If the determination is negative, i.e., if the voltage V is equal to or greater than Vc but less than Vb, the ENG-ECU 30 maintains the number of injections at the previous number (step S22). If the determination in step S20 is positive, i.e., if the voltage V is equal to or greater than Vb but less than Va, the ENG-ECU 30 increases the number of injections by one (step S24). The upper limit of the number of injections is the target value. After step S14, S18, S22, or S24, the processing ends.

[0030] 3(a) and 3(b) are diagrams illustrating time charts. The horizontal axis represents time. The vertical axis represents the voltage of the capacitor 26. In both FIG. 3(a) and FIG. 3(b), warm-up control of the catalyst 15 and split fuel injection are performed. Fuel injection is performed in the order of cylinders #1, #3, #4, and #2. The target number of injections is four. FIG. 3(a) is an example where the engine 10 rotation speed is R1. FIG. 3(b) is an example where the engine rotation speed is R2. R2 is greater than R1, for example, twice R1.

[0031] In the example of Figure 3(a), for example, fuel is injected into one cylinder #1 at times t1, t2, t3, and t4. Fuel is injected into another cylinder #3 at times t5 and t6. Capacitor 26 is charged during the time between injections. The voltage of capacitor 26 changes over time. As voltage is supplied from battery 24, capacitor 26 is charged and the voltage increases. As capacitor 26 discharges, fuel injector 18 injects fuel. After fuel injection, the voltage of capacitor 26 decreases. Capacitor 26 is charged again. For example, capacitor 26 is charged between times t1 and t2 (P1). The rotation speed R1 is lower than R2. As a result, the charging time P1 is longer. The voltage of capacitor 26 increases during time P1. The voltage is less likely to decrease.

[0032] In the example of FIG. 3(b), injections occur at times t7, t8, t18, etc. Capacitor 26 is charged during the time between injections. For example, capacitor 26 is charged during time P2, from time t7 to t8. The engine 10 rotation speed R2 is higher than the rotation speed R1 in FIG. 3(a). Therefore, the charging time P2 is shorter than P1.

[0033] In the example (comparison example) shown by the dashed line in FIG. 3(b), the number of fuel injections for each cylinder is four. Because the charging time is short, the voltage drops. This drop in voltage makes it difficult to drive the fuel injection valve 18, which may result in a decrease in the number of injections. This may result in a deterioration in exhaust emissions and fuel economy.

[0034] The example of the solid line in Figure 3(b) is the first embodiment, in which the number of injections is controlled. Four fuel injections are performed on cylinder #1 (at times t7, t8, t9, and t10). After time t10 (after injection from one fuel injector 18) and before time t11 (before injection from the other fuel injector 18), voltage V1 is lower than threshold Vc. ENG-ECU 30 reduces the number of injections for cylinder #3 by one to three (step S18 in Figure 2).

[0035] Three fuel injections are performed on cylinder #3 (times t11, t12, and t13). After time t13 and before time t14, voltage V2 is lower than threshold Vc. ENG-ECU 30 reduces the number of injections for cylinder #4 by one to two (step S18).

[0036] Two fuel injections are performed on cylinder #4 (times t14 and t15). After time t15 and before time t16, voltage V3 is equal to or greater than threshold value Vc and less than threshold value Vb. ENG-ECU 30 maintains the number of injections for cylinder #2 at two, the same as the previous number (injection to cylinder #4) (step S22).

[0037] Two fuel injections are performed into cylinder #2 (times t16 and t17). After time t17 and before time t18, voltage V4 is equal to or greater than threshold value Va. ENG-ECU 30 sets the number of injections into cylinder #1 to the target value of four (step S14).

[0038] According to the first embodiment, the ENG-ECU 30 acquires the voltage of the capacitor 26 and controls the number of fuel injections from the fuel injection valve 18 based on the voltage. By controlling the number of injections, split injection can be performed to the extent possible. Split injection can reduce exhaust emissions and improve fuel economy.

[0039] The ENG-ECU 30 acquires the voltage of the capacitor 26 after injection from one fuel injector 18 and before injection from the other fuel injector 18. For example, as shown in FIG. 3(b), the ENG-ECU 30 acquires a voltage V1 after injection into cylinder #1 and before injection into cylinder #3, a voltage V2 after injection into cylinder #3 and before injection into cylinder #4, a voltage V3 after injection into cylinder #4 and before injection into cylinder #2, and a voltage V4 after injection into cylinder #2 and before injection into cylinder #1. The ENG-ECU 30 controls the number of injections based on these voltages.

[0040] The ENG-ECU 30 sets the target number of injections to, for example, four. When the voltage V of the capacitor 26 is equal to or greater than the threshold value Va, the ENG-ECU 30 sets the number of injections to the target value. When the voltage V is less than the threshold value Vc, the ENG-ECU 30 reduces the number of injections by, for example, one injection compared to the previous split injection. When the voltage V is equal to or greater than the threshold value Vb and less than Va, the ENG-ECU 30 increases the number of injections by, for example, one injection. When the voltage V is equal to or greater than the threshold value Vc and less than Vb, the ENG-ECU 30 maintains the number of injections at the same number as the previous split injection. The number of injections changes depending on the voltage V. By changing the number of injections, split injections are performed to the extent possible. Split injections can reduce exhaust emissions and improve fuel efficiency. Changing the number of injections suppresses a decrease in the voltage V. As the voltage V increases, the number of injections increases, and it is possible to achieve the target number of injections, as in the example of Figure 3(b).

[0041] The catalyst 15 purifies the exhaust gas from the engine 10. To improve purification performance, the ignition timing is retarded to warm up the catalyst 15. To compensate for the torque reduction caused by the ignition retard, the ENG-ECU 30 increases the engine 10 rotation speed. To reduce exhaust emissions and improve fuel economy, the fuel injection valve 18 performs split injection. The time required to charge the capacitor 26 is shortened. During warm-up control, the ENG-ECU 30 controls the number of injections. Even during warm-up control, voltage drop is suppressed and split injection is possible.

[0042] The ENG-ECU 30 may increase or decrease the number of injections by one, or may increase or decrease the number of injections by, for example, two or more. The target value of the number of injections may be four or less, or may be four or more.

[0043] The number of cylinders in the engine 10 may be four or less, or may be four or more. For example, one fuel injector 18 is provided for each cylinder. A capacitor 26 in a drive circuit 25 supplies voltage to the multiple fuel injectors 18 to drive them. The capacitor 26 is charged between the injection from one fuel injector 18 and the injection from another fuel injector 18. By controlling the number of injections, voltage drops are suppressed and split injections are performed to the extent possible. The processing may be performed by either the ENG-ECU 30 or the HEV-ECU 40.

[0044] Second Embodiment Description of the same configuration as in the first embodiment will be omitted. FIG. 4(a) is a diagram illustrating an example of a flowchart in the second embodiment. The ENG-ECU 30 determines whether or not warm-up control of the catalyst 15 is being performed (step S10). If the determination is negative, the processing ends. If the determination is positive, the ENG-ECU 30 acquires the rotation speed of the engine 10 and the voltage of the capacitor 26 before the start of injection, and controls the number of injections based on the rotation speed and voltage (step S26). The ENG-ECU 30 controls the number of injections for each cylinder based on the rotation speed and voltage. This completes the processing in FIG. 4(a).

[0045] FIG. 4(b) is a diagram illustrating the number of injections. The horizontal axis represents the engine speed of the engine 10. The vertical axis represents the voltage of the capacitor 26. The number of injections is determined according to the engine speed and voltage. The ENG-ECU 30 stores a map such as that shown in FIG. 4(b).

[0046] In the portion below line L1 in Figure 4(b), the number of injections is two. In the portion above line L1 and below line L2, the number of injections is three. In the portion above line L2, the number of injections is four. The point corresponding to the rotation speed R4 and voltage V4 is located below line L1. ENG-ECU 30 sets the number of injections to two (step S26 in Figure 4(a)). The point corresponding to the rotation speed R5 and voltage V5 is located above line L1 and below line L2. ENG-ECU 30 sets the number of injections to three (step S26). The point corresponding to the rotation speed R6 and voltage V6 is above line L2. ENG-ECU 30 sets the number of injections to four (step S26).

[0047] The ENG-ECU 30 controls the number of fuel injections based on the engine 10 rotation speed and the voltage of the capacitor 26. Split injection can be performed. As shown in FIG. 4(b), the higher the voltage, the more injections there are, and the lower the voltage, the fewer injections there are. By reducing the number of injections when the voltage is low, voltage drop is suppressed. The lower the rotation speed, the more injections there are, and the higher the rotation speed, the fewer injections there are. When the rotation speed is low, the time required to charge the capacitor 26 is longer, and voltage drop is suppressed. This allows the number of injections to be increased. When the rotation speed is high, the charging time is shorter. Reducing the number of injections suppresses voltage drop. Split injection can be performed as much as possible by changing the number of injections. The number of injections may be two, three, four, or may include five or more.

[0048] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0049] 1 vehicle 10 Engine 12 Intake passage 13 Throttle valve 14 Exhaust passage 15 Catalyst 16 Spark plug 18 Fuel injection valve 20, 24 battery 22 DC-DC converter 25 Drive circuit 26 Capacitor 30 ENG-ECU 32 Temperature Sensor 34 RPM sensor 40 HEV-ECU

Claims

1. A control device for a vehicle having a fuel injection valve that is driven by a voltage charged in a capacitor, an acquisition unit that acquires a voltage of the capacitor; an injection control unit that controls the number of injections of fuel from the fuel injection valve to the internal combustion engine based on the voltage of the capacitor; a setting unit that sets a target value of the number of injections of fuel from the fuel injection valve to the internal combustion engine, When the voltage of the capacitor is equal to or greater than a first threshold value, the injection control unit sets the number of injections to the target value, When the voltage of the capacitor is less than a second threshold value, the injection control unit reduces the number of injections to be less than the number of previous injections, When the voltage of the capacitor is equal to or greater than the second threshold value and less than a third threshold value, the injection control unit sets the number of injections to be equal to the number of previous injections; A control device for a vehicle, wherein the injection control unit increases the number of injections to be greater than the previous number of injections when the voltage of the capacitor is equal to or greater than the third threshold value and less than the first threshold value.

2. The vehicle control device according to claim 1 , wherein the acquisition unit acquires the voltage of the capacitor after one of the fuel injection valves injects fuel and before the other of the fuel injection valves injects fuel.

3. a rotation speed control unit that controls the rotation speed of the internal combustion engine, the vehicle is provided with a catalyst that purifies exhaust gas from the internal combustion engine; the rotation speed control unit increases the rotation speed when warming up the catalyst compared to when the warming up is not performed, 3. The vehicle control device according to claim 1, wherein the injection control unit controls the number of injections of fuel from the fuel injection valve to the internal combustion engine based on the voltage of the capacitor when warming up the catalyst.

4. 3. The vehicle control device according to claim 1, wherein the injection control unit controls the number of injections of fuel from the fuel injection valve to the internal combustion engine based on the rotation speed of the internal combustion engine and the voltage of the capacitor.

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