JP7694472B2 - Engine Control Unit - Google Patents

Description

The present invention relates to an engine control device.

Conventionally, a control device for this type of engine has been proposed that calculates a basic fuel injection amount at startup based on the temperature at engine startup, and corrects the basic fuel injection amount by increasing or decreasing it depending on the time from engine shutdown to startup (see, for example, Patent Document 1). This device is said to be able to maintain an appropriate equivalence ratio (air-fuel ratio) in the cylinder when the engine is repeatedly started at low temperatures.

JP 2010-138919 A

However, with the above-mentioned engine control device, the engine may not warm up sufficiently immediately after starting the engine when it is cold, resulting in engine stall. One method for suppressing such engine stalls is to calculate the cumulative air volume as the cumulative value of the intake air volume since starting the engine as a parameter reflecting the warm-up state of the engine's combustion chamber, and to reduce the equivalence ratio as the cumulative air volume increases. However, if an engine stall occurs immediately after starting the engine, and the engine is then restarted, the cumulative air volume is large at the initial engine start, so the equivalence ratio becomes excessively small compared to the equivalence ratio that allows the engine to start well, and engine stall at the time of restart cannot be suppressed, resulting in reduced startability.

The engine control device of the present invention aims to suppress a decrease in engine startability.

The engine control device of the present invention comprises:
A control device for an engine that controls an engine so that, after starting the engine in a cold state, an equivalence ratio becomes a target equivalence ratio based on a cooling water temperature at the start of the engine and an integrated air amount that is an integrated value of an intake air amount since the start of the engine,
After the engine is started in a cold state, the target equivalence ratio is set to be larger when the integrated air amount is small than when the integrated air amount is large;
When the engine stalls after being started in the cold state, the integrated air amount is reset to a value of zero.

In the engine control device of the present invention, after starting the engine in a cold state, the target equivalence ratio is set to be smaller when the cumulative air amount is large compared to when it is small. The cumulative air amount is a parameter that reflects the warm-up state of the combustion chamber of the engine, and it is considered that when the cumulative air amount is small, the warm-up of the combustion chamber is not progressing as much as when it is large. Therefore, by setting the target equivalence ratio to be smaller when the cumulative air amount is large compared to when it is small after starting the engine in a cold state, the target equivalence ratio is increased when the cumulative air amount is small and the warm-up of the combustion chamber of the engine is not progressing, thereby suppressing engine stall and suppressing deterioration of engine startability. Then, when an engine stall occurs after starting the engine in a cold state, the cumulative air amount is reset to a value of 0. As a result, after restarting the engine after the engine stall, the cumulative air amount becomes a value of 0, and the target equivalence ratio is set to be larger than when the cumulative air amount is not a value of 0. As a result, engine stall is suppressed and deterioration of engine startability can be suppressed.

1 is a diagram showing an outline of the configuration of an automobile 20 equipped with an engine control device according to an embodiment of the present invention; 4 is a flowchart showing an example of a cold start post-processing executed by an ECU 30. 1 is an explanatory diagram showing an example of time variations in the rotation speed Ne of the engine 22, the target equivalence ratio φ*, and the integrated air amount Iqa. FIG.

Next, we will explain how to implement the present invention using examples.

Figure 1 is a schematic diagram showing the configuration of an automobile 20 equipped with an engine control device as one embodiment of the present invention. As shown in the figure, the automobile 20 of the embodiment is equipped with an engine 22, a starter motor 24, a transmission 26, and an electronic control unit (hereinafter referred to as "ECU") 30. The engine control device of the embodiment mainly corresponds to the ECU 30.

The engine 22 is configured as an internal combustion engine that outputs power using, for example, gasoline or diesel as fuel. The starter motor 24 is connected to a crankshaft 23 as the output shaft of the engine 22, and cranks the engine 22. The transmission 26 includes an automatic transmission (not shown) whose output shaft is connected to a drive shaft 28 that is connected to the drive wheels DW via a differential gear DF, and a torque converter (not shown) connected between the crankshaft 23 and the input shaft of the transmission, and outputs the power from the engine 22 to the drive shaft 28 after changing the speed. The engine 22, the starter motor 24, and the transmission 26 are controlled by an ECU 30.

Although not shown, the ECU 30 is configured as a microcomputer having a CPU, ROM, RAM, flash memory, and input/output ports. Signals from various sensors are input to the ECU 30 via the input ports. Examples of signals input to the ECU 30 include the coolant temperature Tw from the water temperature sensor 22a that detects the temperature of the coolant of the engine 22 and the intake air volume Qa from the air flow meter 22b installed upstream of the throttle valve of the intake pipe. In addition, the accelerator opening Acc from the accelerator pedal position sensor 42 that detects the amount of depression of the accelerator pedal 40 and the vehicle speed V from the vehicle speed sensor 44 can also be mentioned. Various control signals are output from the ECU 30 via the output ports. Examples of signals output from the ECU 30 include control signals to the throttle valve of the engine 22, control signals to the starter motor 24, and control signals to the transmission 26. The ECU 30 calculates the load factor KL of the engine 22 (the ratio of the volume of air actually taken in during one cycle to the stroke volume per cycle of the engine 22) based on the intake air volume Qa from the air flow meter 22b and the engine 22 rotation speed Ne.

In the automobile 20 of the embodiment thus configured, the ECU 30 sets the target gear Gs* of the transmission 26 based on the accelerator opening Acc and the vehicle speed V, and controls the transmission 26 so that the gear Gs of the transmission 26 becomes the target gear Gs*. The ECU 30 also sets the target torque Te* of the engine 22 based on the accelerator opening Acc, the vehicle speed V, and the gear Gs of the transmission 26, and performs intake air volume control, fuel injection control, ignition control, and the like for the engine 22 so that the engine 22 is operated based on the target torque Te*.

In fuel injection control, the ECU 30 sets the target fuel injection amount Qfd* of the fuel injection valve based on the load rate KL of the engine 22 so that the equivalence ratio φ obtained by dividing the theoretical air-fuel ratio by the air-fuel ratio AF from the air-fuel ratio sensor attached upstream of the exhaust pipe purification device becomes the target equivalence ratio φ*, and controls the fuel injection valve so that the target fuel injection amount Qfd* of fuel is injected from the fuel injection valve. Since intake air amount control and ignition control are not central to the present invention, detailed explanations are omitted.

Next, the operation of the automobile 20 of the embodiment thus configured, in particular the setting of the target equivalence ratio φ* after the engine 22 is cold started, will be described. FIG. 2 is a flow chart showing an example of post-cold start processing executed by the ECU 30. This routine is repeatedly executed at predetermined time intervals (e.g., every few msec) after the ignition switch is turned on and the engine 22 is started by cranking the engine 22 using the starter motor 24 with the cooling water temperature Tw at or below a predetermined temperature Tref (after the initial explosion of the engine 22).

When this routine is executed, the CPU of the ECU 30 inputs the start-up water temperature Tws and the intake air volume Qa (step S100). The start-up water temperature Tws is input with the value detected by the water temperature sensor 22a immediately after the engine 22 starts. The intake air volume Qa is input with the value detected by the air flow meter 22b.

Next, it is determined whether or not an engine stall has occurred after starting the engine 22 (step S110). If an engine stall has not occurred, the accumulated air volume Iqa is calculated (step S130). The accumulated air volume Iqa is calculated by adding the intake air volume Qa input in step S100 to the accumulated air volume Iqa calculated the previous time this routine was executed (previous Iqa, initial value is 0). The accumulated air volume Iqa is the accumulated value of the intake air volume Qa since the engine 22 was started.

Next, the target equivalence ratio φ* is set using the accumulated air amount Iqa and the start-up water temperature Tws (step S150), and this routine is terminated. In step S150, the target equivalence ratio φ* is set to be smaller when the start-up water temperature Tws is high compared to when it is low, and is set from a value greater than 1 to be smaller when the accumulated air amount Iqa is large compared to when it is small. The accumulated air amount Iqa is a parameter that reflects the warm-up state of the combustion chamber of the engine 22, and it is considered that when the accumulated air amount Iqa is small, the warm-up of the combustion chamber is not progressing as much as when it is large. Therefore, after starting the engine 22 in a cold state, by setting the target equivalence ratio φ* from a value greater than 1 to be smaller when the accumulated air amount Iqa is large compared to when it is small, engine stall when the accumulated air amount Iqa is small and the warm-up of the combustion chamber of the engine 22 is not progressing can be suppressed.

When an engine stall occurs after starting the engine 22 in step S110, it is determined whether the cumulative air amount Iqa has been reset to a value of 0 at the current engine stall (step S120). If the cumulative air amount Iqa has not been reset to a value of 0 at the current engine stall, the cumulative air amount Iqa is reset to a value of 0 (step S140), the target equivalence ratio φ* is set using the cumulative air amount Iqa and the start-up water temperature Tws (step S150), and this routine is terminated. If the cumulative air amount Iqa has not been reset to a value of 0 at the current engine stall, the cumulative air amount Iqa is reset to a value of 0 (step S140), the target equivalence ratio φ* is set using the cumulative air amount Iqa and the start-up water temperature Tws (step S150), and this routine is terminated. If the cumulative air volume Iqa has already been reset to 0 due to the current engine stall, the target equivalence ratio φ* is set using the cumulative air volume Iqa and the start-up water temperature Tws (step S150), and this routine ends.

3 is an explanatory diagram showing an example of the time change of the rotation speed Ne, the target equivalence ratio φ*, and the cumulative air amount Iqa of the engine 22. In the figure, the solid line shows an embodiment, and the dashed line shows a comparative example. In the comparative example, the engine 22 is started (time t0), and then when the engine stalls (time t1), the cumulative air amount Iqa is not reset to a value of 0. Therefore, from when the engine 22 is restarted (time t2), the cumulative air amount Iqa is accumulated from a value greater than the value 0, and the target equivalence ratio φ* becomes smaller and falls below the value 1, becoming so-called lean. At this time, the warm-up of the combustion chamber of the engine 22 has not progressed, and the engine may stall again. In the embodiment, when the engine stalls (time t1), the cumulative air amount Iqa is reset to a value of 0. Therefore, from when the engine 22 is restarted (time t2), the cumulative air amount Iqa is accumulated from a value of 0, and the target equivalence ratio φ* becomes greater than the value 1, that is, becomes rich, so that engine stall is suppressed. This helps prevent a decrease in the startability of the engine 22.

According to the automobile 20 equipped with the engine control device of the embodiment described above, after the engine 22 is started in a cold state, the target equivalence ratio φ* is set to be larger when the cumulative air volume Iqa is small compared to when it is large, and when the engine 22 stalls after being started in a cold state, the cumulative air volume Iqa is reset to a value of 0, thereby suppressing a decrease in the startability of the engine 22.

The following explains the relationship between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem. In the embodiment, the ECU 30 corresponds to the "engine control device."

The above describes the form for carrying out the present invention using examples, but the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the scope of the invention.

20 automobile, 22 engine, 22a water temperature sensor, 22b air flow meter, 23 crankshaft, 24 starter motor, 26 transmission, 28 drive shaft, 30 electronic control unit (ECU), 40 accelerator pedal, 42 accelerator pedal position sensor, 44 vehicle speed sensor, DF differential gear, DW drive wheels.

Claims (1)

A control device for an engine that controls an engine so that, after starting the engine in a cold state, an equivalence ratio becomes a target equivalence ratio based on a cooling water temperature at the start of the engine and an integrated air amount that is an integrated value of an intake air amount since the start of the engine,
After the engine is started in a cold state, the target equivalence ratio is set to be larger when the integrated air amount is small than when the integrated air amount is large;
When the engine stalls after the engine is started in the cold state, the integrated air amount is reset to a value of 0.

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