JP3721987B2 - Start control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine start control apparatus in a hybrid vehicle including an internal combustion engine, an electric motor for starting the internal combustion engine, and a generator.
[0002]
[Prior art]
In recent years, a hybrid vehicle has been proposed as a technique for improving the fuel efficiency of an internal combustion engine mounted on the vehicle, and a hybrid vehicle employing such a technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-147424. . In the hybrid vehicle described in this publication, the output shaft of the engine and the drive shaft of the motor generator are connected by a belt via an electromagnetic clutch. When the vehicle is temporarily stopped after the engine is warmed up, the electromagnetic clutch is released and the engine is automatically stopped. When the vehicle starts, it travels by connecting an electromagnetic clutch and driving the motor generator with the electric energy of the battery. At this time, after forcibly rotating the engine drive shaft and motoring, the firing is started and the engine is restarted. At the start of firing, an amount of fuel is supplied based on the intake pressure that is relative to the intake air amount. After firing, the motor generator is switched to a power generation function, and power is generated by the power of the engine to charge the battery.
[0003]
FIG. 3 is an explanatory diagram showing the relationship between the motoring rotation speed and the pressure generated in the intake passage when the engine is automatically started. The intake pressure increases as the motoring rotational speed decreases, and the intake pressure decreases as the motoring rotational speed increases.
[0004]
FIG. 4 is an explanatory view showing a change in engine rotation speed at the time of automatic engine start. Therefore, when shifting from motoring to firing, if the intake pressure is high, the amount of intake air also increases and the amount of fuel supply increases, the output torque increases, and the engine speed increases above the target speed. It will be. Further, when the intake pressure is low, the intake air amount is also reduced, the fuel supply amount is reduced, the output torque is reduced, and the engine rotational speed falls from the target rotational speed.
[0005]
[Problems to be solved by the invention]
However, in the above hybrid vehicle, when the rotational speed of the motor generator during motoring is low due to a decrease in the state of charge (SOC) of the battery, the negative pressure generation amount in the intake passage is reduced as shown in FIG. As indicated by the solid line, the pressure is larger than a target intake pressure (indicated by a broken line) for maintaining the motoring rotational speed. Accordingly, the intake air amount at the start of firing becomes larger than the target intake air amount (shown by a broken line), as shown by the solid line. Therefore, the fuel supply amount at the start of firing increases, and the engine rotation speed after firing rises as shown by the solid line, which may cause a running shock.
[0006]
Power generation by the motor generator after firing becomes a load on the engine. However, the required power generation amount for the motor generator after firing is set based on the SOC of the battery. Therefore, the increase in engine rotation speed cannot be suppressed depending on the intake pressure (or intake air amount) in the intake passage and the SOC state of the battery, and the occurrence of running shock may not be suppressed.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to start an internal combustion engine that can suitably suppress an increase or decrease in engine rotation speed after firing when the internal combustion engine is started. It is to provide a control device.
[0008]
[Means for Solving the Problems]
In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 includes an internal combustion engine, an electric motor connectable to the output shaft of the internal combustion engine, and a generator connectable to the output shaft of the internal combustion engine, and the electric motor is stopped when the internal combustion engine is stopped. The internal combustion engine is forcibly rotated by the driving force of the motor and motored, and then firing is started to start the internal combustion engine, and after the firing, power is generated by the generator by the power of the internal combustion engine. In the internal combustion engine start control device, the detecting means for detecting the intake air amount or the intake pressure at the time of transition from motoring to firing of the internal combustion engine, the intake air amount detected by the detecting means and the after firing phi based of the difference between the difference or the intake pressure detected by the detecting means and the fan target intake pressure after earrings and target intake air amount Characterized in that it comprises a power generation amount setting means for setting a required power generation amount with respect to the generator after the ring.
[0009]
When starting the internal combustion engine from the stopped state of the internal combustion engine, if the rotational speed at the time of motoring is different from the predetermined rotational speed from the state of the battery, the intake pressure in the intake passage becomes a value deviated from the target intake pressure. Along with this, the intake air amount at the start of firing also becomes a value that deviates from the target intake air amount, and the engine speed after firing increases or falls. At this time, the amount of power generated by the generator after firing becomes a load on the internal combustion engine. The magnitude of this load amount (required power generation amount) affects the stabilization of the engine speed. In this regard, according to the configuration of claim 1, the required power generation amount for the generator after firing is set based on the intake air amount or the intake pressure at the time of transition from motoring to firing of the internal combustion engine. Therefore, it is possible to suitably suppress the increase or decrease in the rotational speed of the internal combustion engine after firing.
[0011]
By the way , the intake air amount of the internal combustion engine has a relative relationship with the intake pressure of the intake passage, and the intake air amount can be obtained based on the intake pressure. Further, since the intake pressure of the internal combustion engine is detected downstream of the intake passage, the detection accuracy is high. Therefore, the required power generation amount for the generator after firing set based on the intake pressure becomes appropriate, and the increase or decrease in the rotational speed of the internal combustion engine after firing can be more suitably suppressed. .
[0013]
Furthermore, the required power generation amount for the generator after firing is set based on the difference between the intake air amount and the target intake air amount after firing or the difference between the intake pressure and the target intake pressure after firing. The required power generation amount becomes more appropriate, and it is possible to more suitably suppress the increase or decrease in the rotational speed of the internal combustion engine after firing.
[0014]
According to a second aspect of the present invention, in the start control device for an internal combustion engine according to the first aspect, the motor and the generator are a motor function that operates by electric energy of a battery, and a power generation that operates by the power of the internal combustion engine. It is a motor generator provided with a function.
[0015]
According to the configuration of the second aspect , it is sufficient to provide one motor generator having a motor function and a power generation function, and it is possible to reduce the number of parts and suppress an increase in cost and to reduce the installation space. can do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system configuration diagram of an internal combustion engine to which the above-described invention is applied and its control device. Here, a gasoline engine (hereinafter referred to as “engine”) 2 is used as the internal combustion engine. The engine 2 is mounted on a vehicle for driving an automobile.
[0017]
The power (mechanical energy) generated by the engine 2 is output from the crankshaft 2a of the engine 2 to the output shaft 6b side via the torque converter 4 and automatic transmission (hereinafter referred to as “A / T”) 6, and finally Is transmitted to the wheel. Further, the power generated by the engine 2 is transmitted to the belt 14 via the electromagnetic clutch 10 and the pulley 12 connected to the crankshaft 2a. The other pulleys 16, 18, and 20 are rotated by the power transmitted by the belt 14. The electromagnetic clutch 10 is connected / disconnected between the pulley 12 and the crankshaft 2a as necessary to enable switching between non-transmission and transmission of power.
[0018]
A power steering pump 22 is driven by the pulley 16 to generate power steering hydraulic pressure. The pulley 18 drives the air conditioner compressor 24.
[0019]
A motor generator (hereinafter referred to as “M / G”) 26 is driven by the pulley 20, and the M / G 26 functions as a generator. The M / G 26 is electrically connected to the inverter 28. The inverter 28 charges electric energy from the M / G 26 to the battery 30 as a power source based on a power generation command input from an electronic control device (hereinafter referred to as “M / GECU”) 32 for M / G control. Let it be done.
[0020]
Further, when the engine 2 is stopped, the M / G 26 functions as a motor based on a control signal from the inverter 28. At this time, the inverter 28 functions to adjust the supply of electrical energy from the battery 30 to the M / G 26 based on the current command input from the M / GECU 32 so that the rotational speed of the M / G 26 is variable.
[0021]
The M / GECU 32 communicates with an electronic control unit (hereinafter referred to as “ECU”) 38. Information on the amount of charge (SOC) of the battery 30 is input to the M / GECU 32. The M / GECU 32 is configured around a microcomputer. The M / GECU 32 executes necessary arithmetic processing according to the program written in the internal ROM, and drives and controls the electromagnetic clutch 10, the inverter 28, the M / G 26, and the like based on the arithmetic result.
[0022]
In a normal operation state of the engine 2, the M / GECU 32 connects the electromagnetic clutch 10 and rotates the M / G 26 with the power of the engine 2 to generate power. At this time, the M / GECU 32 calculates a required power generation amount according to the SOC of the battery 30 and outputs a power generation command according to the required power generation amount to the inverter 28. Based on this power generation command, the power generation amount of the M / G 26 is controlled by the inverter 28, and the battery 30 is charged by the generated power.
[0023]
In addition, when the engine 2 is automatically started, the M / G 26 is caused to generate power by the power of the engine 2 after the engine 2 is fired. In this case, the M / GECU 32 sets the required power generation amount for the M / G 26 by adding the power generation amount according to the intake pressure of the intake passage 2b to the power generation amount according to the SOC of the battery 30. And M / GECU32 outputs the electric power generation command according to this request | required electric power generation amount to the inverter 28, and controls the electric power generation amount of M / G26.
[0024]
In addition, when a drive request for auxiliary machines such as the power steering pump 22 and the air conditioner compressor 24 is generated in a stop state after the engine 2 is automatically stopped, the M / GECU 32 outputs a current command based on the drive request to the inverter 28. To do. Based on this current command, the inverter 28 operates the M / G 26 to drive the auxiliary machine.
[0025]
The ECU 38 includes an output shaft rotational speed sensor that detects the rotational speed of the output shaft 6b of the A / T 6, an idle switch that detects whether or not the accelerator pedal is depressed, and an accelerator opening that detects the amount of depression of the accelerator pedal (accelerator opening ACCP). A degree sensor, a throttle opening sensor provided in the intake passage 2b to the engine 2 for adjusting the amount of intake air, a throttle opening sensor for detecting an opening of the throttle valve 2c (throttle opening TA), and a shift position SHFT of A / T6. Detection values of a shift position sensor, an engine speed sensor that detects the engine speed NE, a brake switch that detects whether the brake pedal is depressed, a water temperature sensor that detects the engine cooling water temperature THW, or other sensors are input. Further, the ECU 38 receives a detection value of an intake pressure sensor 8 that is provided downstream of the throttle valve 2c in the intake passage 2b and detects the intake pressure. Further, the ECU 38 receives an operation signal for an eco-run switch for the driver to validate the operation of the eco-run system and an air-conditioner switch for validating the operation of the air-conditioner. The eco-run system is an operation control system that reduces fuel consumption and stops exhaust gas emission by stopping fuel supply and stopping the engine 2 when the vehicle is stopped at an intersection or the like.
[0026]
The ECU 38 is configured around a microcomputer and communicates with the M / GECU 32. The ECU 38 executes necessary arithmetic processing according to the program written in the internal ROM. Based on the calculation result, the ECU 38 adjusts the opening degree of the throttle valve 2c, a throttle valve motor 2d, a starter 44, a fuel injection valve 42 for supplying fuel into the intake port or combustion chamber of the engine 2, a igniter, and other actuators. By driving the engine, the engine 2 and the A / T 6 are suitably controlled.
[0027]
Further, when the eco-run switch is turned on by the driver, the ECU 38 performs an automatic stop process and an automatic start process of the engine 2 when the vehicle enters a predetermined driving state.
[0028]
During the automatic stop process of the engine 2, the ECU 38 determines the vehicle operating state, for example, the engine cooling water temperature THW detected by the water temperature sensor, the accelerator pedal depression / non-depression detected by the idle switch, the voltage of the battery 30, and the brake switch. It is determined whether or not the automatic stop condition is satisfied based on the detected depression of the brake pedal and the vehicle speed SPD obtained by conversion from the detected value of the output shaft rotational speed sensor. For example, (1) the engine 2 is warmed up and not overheated (the engine cooling water temperature THW is lower than the water temperature upper limit value THWmax and higher than the water temperature lower limit value THWmin), and (2) the accelerator pedal is depressed. State (idle switch on), (3) state of charge (SOC) of battery 30 being over a certain level (battery voltage is above reference voltage), (4) state of brake pedal being depressed (brake switch ON), and (5) When the conditions (1) to (5) that the vehicle is stopped (vehicle speed SPD is 0 km / h) are all satisfied, it is determined that the automatic stop condition is satisfied. To do. The SOC information of the battery 30 is acquired through communication with the M / GECU 32.
[0029]
On the other hand, if the driver stops the vehicle at an intersection or the like and the automatic stop condition is satisfied, the ECU 38 executes an engine stop process. For example, fuel injection from the fuel injection valve 42 is stopped, and ignition control for the air-fuel mixture in the combustion chamber of the engine 2 by the ignition plug is also stopped. As a result, fuel injection and ignition stop, and the operation of the engine 2 immediately stops.
[0030]
Next, the automatic start process of the engine 2 executed by the ECU 38 and the M / GECU 32 will be described in detail.
FIG. 2 is a flowchart showing an automatic start process executed by the ECU 38 and the M / GECU 32. This process is a process that is repeatedly executed periodically every preset short time. When this process is started, first, at step 100, the ECU 38 is in the driving state of the vehicle, here, for example, the same as the data read in the automatic stop process, the engine coolant temperature THW, the accelerator opening ACCP, and the battery 30. Reads voltage, brake switch status and vehicle speed SPD.
[0031]
In the next step 110, the ECU 38 determines whether or not the automatic start condition is satisfied based on the driving state of the vehicle. For example, under the condition that the engine is stopped by the automatic stop process, (1) the engine 2 is warmed up and not overheated (the engine cooling water temperature THW is lower than the water temperature upper limit value THWmax and the water temperature (2) state in which the accelerator pedal is not depressed (idle switch on), (3) state in which the amount of charge (SOC) of the battery 30 is above a certain level (battery voltage is above the reference voltage) (4) Conditions (1) to (5) where the brake pedal is depressed (brake switch on) and (5) the vehicle is stopped (vehicle speed SPD is 0 km / h) If one of the above is not satisfied, it is determined that the automatic start condition is satisfied. The automatic start conditions (1) to (5) described above are the same as the conditions used in the automatic stop condition. However, the conditions are not limited to these, and conditions other than the conditions (1) to (5) May be set, or may be limited to some of the conditions (1) to (5). If it is determined in step 110 that the automatic start condition is not satisfied, the ECU 38 once ends this process.
[0032]
If it is determined in step 110 that the automatic start condition is satisfied, the ECU 38 transfers an automatic start command to the M / GECU 32. In step 120, the M / GECU 32 connects the electromagnetic clutch 10 based on the automatic start command, and rotates the M / G 26 via the inverter 28 to forcibly rotate the crankshaft 2a of the engine 2 to perform motoring. .
[0033]
In the next step 130, the M / GECU 32 subtracts the target intake pressure pt for maintaining the same rotational speed as the motoring rotational speed during engine operation from the intake pressure pn detected by the intake pressure sensor 8 during motoring. To calculate the differential pressure Δp.
[0034]
In the following step 140, the M / GECU 32 calculates the required power generation amount mgtrq after firing based on the following equation.
mgtrq = Δp * k + mgtrq0
In the above equation, mgtrq0 is a power generation amount required according to the SOC state of the battery 30, and k is a coefficient for converting the differential pressure Δp into the power generation amount.
[0035]
When the motoring time reaches a predetermined time and the engine rotational speed reaches the predetermined rotational speed, in step 150, the ECU 38 performs fuel injection processing and ignition timing control processing to burn the engine 2 and perform firing. At this time, the ECU 38 sets the fuel injection amount based on the intake pressure pn and the engine speed so that the stoichiometric air-fuel ratio is obtained.
[0036]
In step 160, after firing, the M / GECU 32 outputs a power generation command corresponding to the required power generation amount calculated in step 140 to the inverter 28 to control the power generation amount of the M / G 26.
[0037]
FIG. 5 shows the operation at the start of the engine 2 of the embodiment. If the engine speed during motoring of the engine 2 is small due to a decrease in the SOC state of the battery 30 or the like, the amount of negative pressure generated in the intake passage is small, and the intake pressure is the motoring speed as indicated by the solid line. It becomes a value larger than the target intake pressure (indicated by a broken line) for maintaining. Accordingly, the intake air amount at the start of firing becomes larger than the target intake air amount (shown by a broken line), as shown by the solid line. Therefore, the fuel supply amount at the start of firing increases, and the engine rotation speed after firing tends to blow up as indicated by the chain line.
[0038]
However, the required power generation amount for the M / G 26 after firing is obtained by adding the power generation amount corresponding to the pressure difference Δp between the intake pressure pn and the target intake pressure pt to the power generation amount required according to the SOC state of the battery 30. Value is set. Accordingly, it is possible to suitably suppress the increase or decrease in the rotational speed of the engine 2 after firing.
[0039]
According to the embodiment described above, the following effects can be obtained.
In this embodiment, when the engine 2 is automatically started, power generation is performed by setting the required power generation amount for the M / G 26 after firing based on the intake pressure at the time of transition from motoring to firing. I did it. Therefore, it is possible to suitably suppress the increase or decrease in the rotational speed of the engine 2 after firing.
[0040]
In addition, the intake pressure in the intake passage 2b has a relative relationship with the intake air amount of the engine 2, and the intake pressure is detected downstream of the intake passage 2b, so the detection accuracy is high. Moreover, the required power generation amount for the M / G 26 after firing is set based on the difference between the intake pressure in the intake passage 2b and the target intake pressure after firing. Therefore, the required power generation amount of the M / G 26 set based on this intake pressure becomes more appropriate, and it is possible to more suitably suppress the increase or decrease in the rotational speed of the engine 2 after firing.
[0041]
-In this embodiment, since it was set as M / G26 provided with the motor function and the electric power generation function, if only one M / G26 is provided, the number of parts can be reduced and the cost increase can be suppressed. The installation space can also be reduced.
[0042]
The embodiment can be modified as follows.
In the above embodiment, the required power generation amount for the M / G 26 at the time of restarting the engine 2 is set based on the intake pressure, but this required power generation amount is based on the intake air amount when shifting from motoring to firing. May be set. That is, the charging efficiency of air into each cylinder of the engine 2 is obtained based on the intake pressure and the engine rotation speed, and the intake air amount into each cylinder can be obtained based on the charging efficiency. In this case, a target intake air amount capable of maintaining the rotational speed of the motoring of the engine 2 is set in advance. In step 130, the difference between the intake air amount and the target intake air amount is obtained, and in step 140, the required power generation amount is calculated based on the intake air amount difference. The value of the correction coefficient k is different from that of the differential pressure Δp. Also in this case, the same operations and effects as described above can be obtained.
[0043]
In the case where the air flow meter is provided downstream of the air cleaner in the intake passage 2b, the required power generation amount for the M / G 26 when the engine 2 is restarted based on the actual intake air amount detected by the air flow meter May be set. Also in this case, substantially the same operations and effects as described above can be obtained.
[0044]
Next, other technical ideas that can be grasped from the above embodiment will be described below.
2. The start control device for an internal combustion engine according to claim 1 , wherein the power generation amount setting means includes a power generation amount according to a state of a battery that supplies electric energy to the electric motor, and a required power generation amount for the generator. Is a start control device for an internal combustion engine.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an internal combustion engine and a control device thereof according to an embodiment.
FIG. 2 is a flowchart illustrating an automatic start process according to the embodiment.
FIG. 3 is an explanatory diagram showing the relationship between the motoring rotational speed of the internal combustion engine and the intake pressure.
FIG. 4 is an explanatory diagram showing changes in engine rotation speed in motoring and firing of an internal combustion engine.
FIG. 5 is an explanatory diagram showing an operation at the time of starting the engine according to the embodiment.
FIG. 6 is an explanatory diagram showing an operation at the time of starting a conventional engine.
[Explanation of symbols]
2 ... Engine, 2a ... Crankshaft, 2b ... Intake passage, 2c ... Throttle valve, 2d ... Throttle valve motor, 4 ... Torque converter, 6 ... A / T, 6b ... Output shaft, 8 ... Intake pressure sensor, 10 ... Electromagnetic Clutch, 12 ... pulley, 14 ... belt, 16, 18, 20 ... pulley, 22 ... power steering pump, 24 ... air conditioner compressor, 26 ... motor generator (M / G), 28 ... inverter, 30 ... battery, 32 ... M / GECU, 38 ... ECU, 42 ... fuel injection valve, 44 ... starter.

Claims (2)

An internal combustion engine, an electric motor connectable to the output shaft of the internal combustion engine, and a generator connectable to the output shaft of the internal combustion engine,
After the internal combustion engine is forcibly rotated by the driving force of the electric motor when the internal combustion engine is stopped and motored, the firing is started to start the internal combustion engine, and after the firing, the power of the internal combustion engine is used to In an internal combustion engine start control device configured to generate power by a generator,
Detecting means for detecting an intake air amount or an intake pressure at the time of transition from motoring to firing of the internal combustion engine;
Based on the difference between the intake air amount detected by the detection means and the target intake air amount after firing or the difference between the intake pressure detected by the detection means and the target intake pressure after firing. A start control device for an internal combustion engine, comprising: a power generation amount setting means for setting a required power generation amount for the generator. The start control device for an internal combustion engine according to claim 1,
The motor and generator are start control devices for an internal combustion engine, which is a motor generator having a motor function that operates by electric energy of a battery and a power generation function that operates by power of the internal combustion engine.

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