Control system for hybrid vehicles

Abstract

To suppress impact on an exhaust gas at engine starting and generation of rattling noise.SOLUTION: A control device used for a hybrid vehicle includes a calculation part for calculating a fuel injection quantity at engine starting. When there is a motoring history, the calculation part adds a correction term for correcting a reference fuel injection quantity to the reference fuel injection quantity being a reference to calculate the fuel injection quantity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background Art]

[0002] For example, a series hybrid system includes an engine, a generator motor that generates electric power using the power of the engine, a drive motor that generates driving force for traveling, and a battery that stores electric power supplied to the drive motor. An engine output gear is provided on a crankshaft of the engine, a generator motor gear is provided on a rotating shaft of the generator motor, and power is transmitted between the engine and the generator motor when the engine output gear and the generator motor gear mesh with each other.

[0003] In a vehicle equipped with such a hybrid system, a technology has been proposed that calculates a fuel injection amount at the time of engine starting based on the coolant temperature of the engine and the engine rotation speed. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2012-112256 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Here, when starting the engine during motoring, the required fuel injection amount may change. For example, when starting the engine immediately after motoring, the required fuel injection amount may be larger than that in a case where there is no motoring history. Further, for example, when there is a motoring history, the required fuel injection amount may decrease as the engine stop time elapses.

[0006] Thus, if the required fuel injection amount at engine startup differs, the air-fuel ratio changes, which can affect exhaust emissions. Furthermore, if too little fuel is injected when a large amount is required, combustion in the engine will be insufficient. For example, the teeth of the engine output gear and the teeth of the generator motor gear may collide forcefully, resulting in a so-called "clacking" noise.

[0007] The objective of the present invention is to provide a control device for a hybrid vehicle that can suppress the impact on exhaust gas and the generation of gear noise during engine startup. [Means for solving the problem]

[0008] To achieve the above objective, the control device for a hybrid vehicle according to the present invention is a control device for use in a hybrid vehicle that includes a calculation unit for calculating the fuel injection amount when the engine is started, wherein, if there is a motoring history, the calculation unit calculates the fuel injection amount by adding a correction term to a reference fuel injection amount that corrects the reference fuel injection amount.

[0009] In this configuration, the control unit of a hybrid vehicle calculates the fuel injection amount by adding a correction term to the standard fuel injection amount when there is a motoring history. Therefore, it is possible to calculate the required fuel injection amount at engine startup depending on whether or not there is a motoring history. As a result, the control unit of the hybrid vehicle can suppress the impact on exhaust gases at engine startup without changing the air-fuel ratio.

[0010] Furthermore, by injecting a corrected amount of fuel into the engine depending on whether or not there is a motoring history, combustion within the engine becomes sufficient, the engine speed increases, and thus gear noise can be suppressed. As a result, the control system of a hybrid vehicle can suppress the generation of gear noise caused by gear noise.

[0011] Furthermore, for example, the correction term may be calculated based on a correction reference value calculated from the intake air temperature and the cumulative intake air volume during motoring, and a correction coefficient calculated from the water temperature and the engine stop time after motoring. Moreover, for example, the correction coefficient may decrease as the engine stop time elapses.

[0012] This allows, for example, the correction term to calculate the required fuel injection amount according to the motoring state. As a result, the control system of a hybrid vehicle can suppress the impact on exhaust emissions and the generation of gear noise during engine startup. [Effects of the Invention]

[0013] According to the present invention, it is possible to suppress the impact on exhaust gases and the generation of gear noise during engine startup. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a block diagram showing an example of the configuration of a hybrid vehicle to which a control device according to one embodiment of the present invention is applied. [Figure 2] Figure 2 is a table for calculating a correction reference value for the fuel injection amount at engine startup based on the engine intake air temperature and the cumulative intake air volume of the engine, according to one embodiment of the present invention. [Figure 3] Figure 3 is a table for calculating a correction coefficient for the fuel injection amount at engine startup based on the engine water temperature and the engine stop time after motoring, according to one embodiment of the present invention. [Figure 4] Figure 4 is a system diagram showing an example of a system for determining the amount of fuel injected at engine startup, according to one embodiment of the present invention. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] <Hybrid vehicle> FIG. 1 is a block diagram showing the configuration of a hybrid vehicle 1.

[0017] The hybrid vehicle 1 is equipped with a series-type hybrid system 2. The hybrid system 2 includes an engine 11, a generator motor (MG1) 12, a drive motor (MG2) 13, a battery 14, and a PCU (Power Control Unit) 15.

[0018] The engine 11 is, for example, a gasoline engine. The engine 11 includes a throttle body, a fuel injector that injects fuel into intake air, and the like. The throttle body is a component that takes in fuel and air and sends them to the fuel chamber of the engine 11, and is equipped with an electronic throttle valve (hereinafter also simply referred to as a throttle valve) for adjusting the amount of intake air into the combustion chamber of the engine 11, a throttle position sensor that detects the opening degree of the electronic throttle valve, a control valve for adjusting the intake air amount during idling such as when the vehicle is stopped, and the like. The engine 11 is also provided with an associated starter for starting the engine.

[0019] The generator motor 12 is formed of, for example, a permanent magnet synchronous motor. The rotating shaft of the generator motor 12 is mechanically connected to the crankshaft of the engine 11 via a gear (not shown). For example, an engine output gear is non-rotatably supported on the crankshaft of the engine 11, a motor gear is non-rotatably supported on the rotating shaft of the generator motor 12, and the engine output gear and the motor gear are meshed with each other. The output of the engine 11 is transmitted to the generator motor 12.

[0020] The drive motor 13 is, for example, a permanent magnet synchronous motor larger than the generator motor 12. The rotating shaft of the drive motor 13 is connected to the drive system 16 of the hybrid vehicle 1. The drive system 16 includes a differential gear, and the power of the drive motor 13 is transmitted to the differential gear, then distributed and transmitted from the differential gear to drive wheels 17 consisting of left and right front wheels or rear wheels. Accordingly, the left and right drive wheels 17 rotate, causing the hybrid vehicle 1 to move forward or backward.

[0021] The battery 14 is an assembled battery formed by combining a plurality of secondary batteries. The secondary battery is, for example, a lithium-ion battery. The battery 14 outputs DC power of approximately 200 to 350 V (volts), for example.

[0022] The PCU 15 is a unit for controlling driving of the generator motor 12 and the drive motor 13, and includes a first inverter 21, a second inverter 22, and a converter 23.

[0023] When starting the engine 11, DC power output from the battery 14 is boosted by the converter 23, the boosted DC power is converted into AC power by the first inverter 21, and the AC power is supplied to the generator motor 12. Accordingly, the generator motor 12 performs power running operation, and the engine 11 is motored (cranked) by the generator motor 12 (motoring operation). When the rotation speed of the crankshaft of the engine 11 increases to the rotation speed required for starting due to motoring, and the spark plug of the engine 11 ignites, the engine 11 starts.

[0024] When the hybrid vehicle 1 is traveling, the drive motor 13 performs power running operation, and the drive motor 13 generates power.

[0025] When the output required of the drive motor 13 is smaller than the output of the battery 14, the hybrid vehicle 1 performs EV travel. That is, the engine 11 is stopped, power generation by the generator motor 12 is not performed, power is supplied from the battery 14 to the drive motor 13, and the drive motor 13 is driven by the power.

[0026] On the other hand, when the output required for the drive motor 13 exceeds the output of the battery 14, the hybrid vehicle 1 operates as an HEV. That is, the engine 11 is put into operation and the generator motor 12 is put into regenerative operation, so that the power of the engine 11 is converted into AC power by the generator motor 12. Then, the AC power from the generator motor 12 is converted into DC power by the first inverter 21, and the DC power output from the first inverter 21 is converted into AC power by the second inverter 22, and this AC power is supplied to the drive motor 13, thereby driving the drive motor 13.

[0027] Furthermore, when the remaining capacity of the battery 14 falls below a predetermined level, fuel is injected into the engine 11 regardless of whether the drive motor 13 is running or stopped, and the generator motor 12 is operated to generate electricity while the engine 11 is running (firing operation). At this time, the AC power from the generator motor 12 is converted to DC power by the first inverter 21, the DC power output from the first inverter 21 is stepped down by the converter 23, and the stepped-down DC power is supplied to the battery 14, thereby charging the battery 14.

[0028] When the hybrid vehicle 1 decelerates, the drive motor 13 is regenerated, and the power transmitted from the drive wheels 17 to the drive motor 13 is converted into alternating current (AC) power. At this time, the drive motor 13 becomes a resistance in the drive system, and this resistance acts as a braking force (regenerative braking force) that brakes the hybrid vehicle 1. At this time, in the PCU 15, the AC power supplied from the drive motor 13 to the second inverter 22 is converted into DC power in the second inverter 22, and the DC power output from the second inverter 22 is stepped down by the converter 23. Then, the stepped-down DC power is supplied to the battery 14, thereby charging the battery 14.

[0029] Hybrid vehicle 1 is equipped with multiple ECUs (Electronic Control Units). Each ECU has a microcontroller unit, which contains, for example, a CPU, non-volatile memory such as flash memory, and volatile memory such as DRAM (Dynamic Random Access Memory).

[0030] Multiple ECUs are connected via the CAN (Controller Area Network) communication protocol, enabling bidirectional communication. Each ECU is connected to various sensors necessary for control, and receives detection signals from these sensors. In addition to detection signals from the sensors, each ECU also receives control-related information from other ECUs.

[0031] Figure 1 shows ECU311 and ECU312, which control the hybrid system 2, among several ECUs. ECU31, which includes ECU311 and ECU312, is an example of a control device for the hybrid vehicle 1.

[0032] The ECU311 is connected to an accelerator sensor 32 and a vehicle speed sensor 33. The accelerator sensor 32 outputs a detection signal corresponding to the amount of pressure applied to the accelerator pedal by the driver. The vehicle speed sensor 33 outputs a pulse signal as a detection signal that is synchronized with the rotation of a rotating body that rotates as the hybrid vehicle 1 moves.

[0033] Furthermore, the ECU312 is connected to an intake air temperature sensor 34, an intake air volume sensor 35, and a water temperature sensor 36. The intake air temperature sensor 34 detects the intake air temperature of the engine 11 and outputs a detection signal corresponding to the detected intake air temperature. The intake air volume sensor 35 detects the intake air volume of the engine 11 and outputs a detection signal corresponding to the detected intake air volume. The water temperature sensor 36 detects the coolant temperature of the engine 11 and outputs a detection signal corresponding to the detected coolant temperature (hereinafter also referred to as water temperature).

[0034] In the ECU311, the accelerator opening, which is the ratio of the current accelerator pedal operation to the maximum operation amount, is determined from the detection signal of the accelerator sensor 32. In addition, the ECU311 determines the frequency of the detection signal (pulse signal) from the detection signal of the vehicle speed sensor 33, and this frequency is converted into vehicle speed.

[0035] Furthermore, the method by which the ECU31 recognizes vehicle speed is not limited to using a detection signal obtained from the vehicle speed sensor 33. Other methods may also be used, for example, by using vehicle speed-related information obtained via CAN from the PCU15 or VSC (Vehicle Stability Control).

[0036] The ECU312 comprises an acquisition unit, a determination unit, a timing unit, a calculation unit, and a control unit. The acquisition unit acquires the intake air temperature of the engine 11 from the intake air temperature sensor 34. The acquisition unit also acquires the cumulative intake air volume (hereinafter also referred to as intake air volume) of the engine 11 from the intake air volume sensor 35. Furthermore, the acquisition unit acquires the water temperature of the engine 11 from the water temperature sensor 36. The determination unit determines whether there is a motoring history. The timing unit measures the time since the end of motoring. The control unit controls the fuel injector (engine) to inject fuel corresponding to the fuel injection amount calculated by the calculation unit (injection correction).

[0037] The calculation unit calculates the fuel injection amount when the engine starts. Furthermore, if the determination unit determines that there is a motoring history, the calculation unit adds a correction term to the standard fuel injection amount to calculate the fuel injection amount.

[0038] Here, we will explain how to determine the fuel injection amount at engine startup using Figures 2, 3, and 4. Figure 2 is a table for calculating a correction reference value for the fuel injection amount at engine startup from the intake air temperature and the cumulative intake air volume of the engine 11, according to one embodiment of the present invention. Figure 3 is a table for calculating a correction coefficient for the fuel injection amount at engine startup from the engine water temperature and the engine stop time after motoring, according to one embodiment of the present invention. Figure 4 is a system diagram showing an example of a system for determining the fuel injection amount at engine startup, according to one embodiment of the present invention.

[0039] Here, the values ​​of intake air temperature (a), intake air volume (b), and correction reference value (c) shown in Table 41 of Figure 2 are assumed to be positive numbers. Also, the values ​​of water temperature (d), correction coefficients (e, f, g, h, i), and the time from the end of motoring to restart (engine stop time) (t1, t2, t3, t4, and t5) shown in Table 42 of Figure 3 are assumed to be positive numbers. Furthermore, the values ​​of the correction coefficients (e, f, g, h, and i) are less than 1. In addition, the relationship between the values ​​of the correction coefficients (e, f, g, h, and i) is 1>e>f>g>h>i. In other words, the correction coefficient decreases as the engine stop time elapses.

[0040] The calculation unit of the ECU312 calculates a correction term based on a correction reference value calculated from the intake air temperature and the cumulative intake air volume during motoring, and a correction coefficient calculated from the water temperature and the engine stop time after motoring. Specifically, first, if the determination unit of the ECU312 determines that there is a motoring history, the calculation unit of the ECU312 refers to the table 41 shown in Figure 2, based on the intake air temperature of the engine 11 and the cumulative intake air volume of the engine 11 acquired by the acquisition unit of the ECU312, and identifies the correction reference value (see Figure 4).

[0041] Furthermore, the calculation unit of the ECU312 determines a correction coefficient by referring to the table 42 shown in Figure 3, based on the engine water temperature 11 acquired by the acquisition unit of the ECU312 and the time since the end of motoring measured by the timing unit. The calculation unit of the ECU312 then calculates a correction term by multiplying the determined correction reference value by the correction coefficient (see Figure 4).

[0042] For example, if the determination unit of the ECU312 determines that there is a motoring history, then the acquisition unit of the ECU312 acquires the intake air temperature of the engine 11 as a [°C], the cumulative intake air volume of the engine 11 as b [g], and the water temperature of the engine 11 as d [°C]. Also, let t2 [s] be the time since the end of motoring, as measured by the timing unit of the ECU312.

[0043] In this case, the calculation unit of the ECU312 refers to Table 41 shown in Figure 2 and identifies the correction reference value as c. The calculation unit of the ECU312 also refers to Table 42 shown in Figure 3 and identifies the correction coefficient as e. Then, based on the identified correction reference value c and the correction coefficient e, the calculation unit of the ECU312 calculates the correction term (= c × e) by multiplying the identified correction reference value c by the correction coefficient e (see Figure 4). The control unit of the ECU312 then performs injection correction, which controls the injection of a fuel injection amount that is the standard fuel injection amount calculated by the calculation unit plus the correction term, from engine start-up until the end of injection.

[0044] As a result, the control device of the hybrid vehicle 1 can calculate the required fuel injection amount according to the state of the engine 11 (intake air temperature, cumulative intake air volume, water temperature, and engine stop time) if there is a motoring history. However, the functions of the ECU 312 are not limited to this.

[0045] <Effects of this embodiment> As described above, in the case of the hybrid vehicle 1 according to this embodiment, if there is a motoring history, the control device calculates the fuel injection amount by adding a correction term that corrects the standard fuel injection amount to the standard fuel injection amount.

[0046] Therefore, according to the present invention, the control device of the hybrid vehicle 1 can calculate the required fuel injection amount at engine startup depending on whether or not there is a motoring history. As a result, the control device of the hybrid vehicle 1 can suppress the impact on exhaust gas at engine startup without changing the air-fuel ratio.

[0047] Furthermore, by injecting a corrected amount of fuel into the engine depending on whether or not there is a motoring history, combustion in the engine becomes sufficient, the engine speed increases, and thus gear noise can be suppressed. As a result, the control device of the hybrid vehicle 1 can suppress the generation of gear noise caused by gear noise.

[0048] Furthermore, for example, the correction term may be calculated based on a correction reference value calculated from the intake air temperature and the cumulative intake air volume during motoring, and a correction coefficient calculated from the water temperature and the engine stop time after motoring. Moreover, for example, the correction coefficient may decrease as the engine stop time elapses.

[0049] As a result, for example, the correction term calculates the required fuel injection amount according to the motoring state. This allows the control device of the hybrid vehicle 1 to suppress the impact on exhaust gases and the generation of gear noise during engine startup.

[0050] Although this embodiment describes a control device applied to a series hybrid system 2, it is not limited to this. For example, it can be applied to a series-parallel hybrid system in which a power split mechanism is provided in the vehicle and both the engine and motor are used as power sources, as well as mild hybrid systems and parallel hybrid systems that utilize the motor as an auxiliary motor for the engine (e.g., ISG (Integrated Starter Generator)).

[0051] Although embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Moreover, this embodiment is included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0052] 1: Hybrid vehicles 11: Engine 12: Generator motor 13: Drive motor 14: Battery 15: PCU 312: ECU (Control Unit, Acquisition Unit, Judgment Unit, Timing Unit, Calculation Unit, Control Unit)

Claims

[Claim 1] A control device used in a hybrid vehicle, which includes a calculation unit that calculates the amount of fuel injected when the engine is started, The calculation unit, when there is a motoring history, calculates the fuel injection amount by adding a correction term calculated based on a correction reference value calculated from the intake air temperature and the cumulative intake air volume during motoring, and a correction coefficient calculated from the water temperature and the engine stop time after motoring, which decreases as the engine stop time elapses. Control system for hybrid vehicles.

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