Engine control device

Abstract

To suppress deterioration in startability of an engine.SOLUTION: An engine control device controls an engine such that after starting the engine during cold, the equivalence ratio becomes a target equivalence ratio based on a cooling water temperature at the time of engine startup and an integrated air amount, which is the integrated value of intake air amounts since startup of the engine. After starting the engine during cold, when the integrated air amount is small, the engine control device sets the target equivalence ratio to be larger as compared with that when the integrated air amount is large, and when the engine stalls after starting the engine during cold, resets the integrated air amount to a value 0.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an engine control device.

Background Art

[0002] Conventionally, as an engine control device of this type, there has been proposed one that calculates a basic fuel injection amount at startup based on the temperature of the engine at startup and corrects the basic fuel injection amount at startup by an increase or decrease amount according to the time from engine stop to startup (see, for example, Patent Document 1). In this device, it is assumed that when the engine is repeatedly started at low temperatures, the inside of the cylinder can be set to an appropriate equivalence ratio (air-fuel ratio).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described engine control device, immediately after starting the engine in the cold state, the engine warm-up is insufficient and the engine may stall. As a method for suppressing such engine stalls, after starting the engine, an integrated air intake amount is calculated as an integrated value of the intake air amount since the engine was started, as a parameter reflecting the warm-up state of the engine combustion chamber, and the equivalence ratio is made smaller as the integrated air intake amount increases. However, when an engine stall occurs immediately after starting the engine and then the engine is restarted, since the integrated air intake amount has increased at the first engine start, the equivalence ratio becomes excessively smaller than the equivalence ratio at which the engine can be started well, and engine stall during restart cannot be suppressed, and the startability may deteriorate.

[0005] The engine control device of the present invention aims to suppress a decrease in the starting performance of the engine.

Means for Solving the Problems

[0006] The engine control device of the present invention is an engine control device that controls the engine such that, after starting the engine during cold conditions, the equivalence ratio becomes a target equivalence ratio based on the integrated air amount, which is the product of the coolant temperature at the start of the engine and the integrated value of the intake air amount since starting the engine. After starting the engine during cold conditions, the target equivalence ratio is set to be larger when the integrated air amount is small than when it is large. When the engine stalls after starting the engine during cold conditions, the integrated air amount is reset to the value 0. This is the gist.

[0007] In this engine control device of the present invention, after starting the engine during cold conditions, the target equivalence ratio is set to be smaller when the integrated air amount is large than when it is small. The integrated air amount is a parameter that reflects the warm-up state of the combustion chamber of the engine. When the integrated air amount is small, it is considered that the warm-up of the combustion chamber has not progressed as much as when it is large. Therefore, by setting the target equivalence ratio to be smaller when the integrated air amount is large than when it is small after starting the engine during cold conditions, the target equivalence ratio is increased when the integrated air amount is small and the warm-up of the combustion chamber of the engine has not progressed, so engine stall can be suppressed and a decrease in the starting performance of the engine can be suppressed. And when engine stall occurs after starting the engine during cold conditions, the integrated air amount is reset to the value 0. As a result, after restarting the engine after engine stall, the integrated air amount becomes the value 0, and the target equivalence ratio is set larger than when the integrated air amount is not the value 0. As a result, engine stall is suppressed and a decrease in the starting performance of the engine can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0009] Next, the mode for carrying out the present invention will be described using examples.

Example

[0010] FIG. 1 is a configuration diagram showing an outline of the configuration of an automobile 20 equipped with an engine control device as an embodiment of the present invention. As shown in the figure, the automobile 20 of the embodiment includes an engine 22, a starter motor 24, a transmission 26, and an electronic control unit (hereinafter referred to as "ECU") 30. As the engine control device of the embodiment, mainly the ECU 30 corresponds.

[0011] The engine 22 is configured as an internal combustion engine that outputs power using, for example, gasoline or light oil as fuel. The starter motor 24 is connected to the 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 connected to 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 transmits the power from the engine 22 after shifting it to the drive shaft 28. The engine 22, the starter motor 24, and the transmission 26 are controlled by the ECU 30.

[0012] Although not shown in the figures, 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 the signals input to the ECU 30 include the coolant temperature Tw from a water temperature sensor 22a that detects the temperature of the coolant of the engine 22, and the intake air amount Qa from an air flow meter 22b attached upstream of the throttle valve in the intake pipe. Further, examples also include the accelerator opening Acc from an accelerator pedal position sensor 42 that detects the depression amount of the accelerator pedal 40, and the vehicle speed V from a vehicle speed sensor 44. Various control signals are output from the ECU 30 via the output ports. Examples of the 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 a load factor KL (the ratio of the volume of air actually inhaled in one cycle to the stroke volume per cycle of the engine 22) of the engine 22 based on the intake air amount Qa from the air flow meter 22b and the engine speed Ne of the engine 22.

[0013] In the automobile 20 of the embodiment configured as described above, the ECU 30 sets a target gear stage 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 stage Gs of the transmission 26 becomes the target gear stage Gs*. Further, based on the accelerator opening Acc, the vehicle speed V, and the gear stage Gs of the transmission 26, a target torque Te* of the engine 22 is set, and intake air amount control, fuel injection control, ignition control, etc. of the engine 22 are performed so that the engine 22 is operated based on the target torque Te*.

[0014] In fuel injection control, the ECU 30 sets the target fuel injection amount Qfd* of the fuel injection valve based on the load factor KL of the engine 22 so that the equivalence ratio φ obtained by subtracting the stoichiometric air-fuel ratio from the air-fuel ratio AF from the air-fuel ratio sensor, which is attached upstream of the purification device in the exhaust pipe, becomes the target equivalence ratio φ*, and controls the fuel injection valve so that fuel of the target fuel injection amount Qfd* is injected from the fuel injection valve. Regarding intake air amount control and ignition control, since they do not form the core of the present invention, detailed descriptions thereof are omitted.

[0015] Next, the operation of the automobile 20 of the embodiment configured in this way, particularly, the setting of the target equivalence ratio φ* after the engine 22 is cold-started will be described. FIG. 2 is a flowchart showing an example of post cold-start processing executed by the ECU 30. This routine is repeatedly executed at predetermined intervals (for example, every few msec) after the engine 22 is started by cranking the engine 22 using the starter motor 24 in a state where the coolant temperature Tw is equal to or lower than a predetermined temperature Tref after the ignition switch is turned on (after the first explosion of the engine 22).

[0016] When this routine is executed, the CPU of the ECU 30 inputs the starting water temperature Tws and the intake air amount Qa (step S100). The starting water temperature Tws inputs the value detected by the water temperature sensor 22a immediately after the engine 22 is started. The intake air amount Qa inputs the value detected by the air flow meter 22b.

[0017] Subsequently, it is determined whether or not an engine stall has occurred after the engine 22 is started (step S110). When no engine stall has occurred, the integrated air amount Iqa is calculated (step S130). The calculation of the integrated air amount Iqa is a value obtained by adding the intake air amount Qa input in step S100 to the integrated air amount Iqa (previous Iqa, initial value is 0) calculated when the previous routine was executed. The integrated air amount Iqa is the integrated value of the intake air amount Qa since the engine 22 was started.

[0018] Subsequently, the target equivalence ratio φ* is set using the integrated air quantity Iqa and the starting water temperature Tws (step S150), and this routine ends. In step S150, the target equivalence ratio φ* is set to be smaller when the starting water temperature Tws is high than when it is low, and is set to be smaller when the integrated air quantity Iqa is large than when it is small, starting from a value greater than 1. The integrated air quantity Iqa is a parameter that reflects the warm-up state of the combustion chamber of the engine 22. When the integrated air quantity Iqa is small, it is considered that the warm-up of the combustion chamber has not progressed as much as when it is large. Therefore, after starting the engine 22 during cold conditions, by setting the target equivalence ratio φ* to be smaller when the integrated air quantity Iqa is large than when it is small, starting from a value greater than 1, it is possible to suppress engine stall when the integrated air quantity Iqa is small and the warm-up of the combustion chamber of the engine 22 has not progressed.

[0019] When an engine stall occurs after starting the engine 22 in step S110, it is determined whether the integrated air quantity Iqa has been reset to the value 0 due to the current engine stall (step S120). When the integrated air quantity Iqa has not been reset to the value 0 due to the current engine stall, the integrated air quantity Iqa is reset to the value 0 (step S140), the target equivalence ratio φ* is set using the integrated air quantity Iqa and the starting water temperature Tws (step S150), and this routine ends. When the integrated air quantity Iqa has not been reset to the value 0 due to the current engine stall, the integrated air quantity Iqa is reset to the value 0 (step S140), the target equivalence ratio φ* is set using the integrated air quantity Iqa and the starting water temperature Tws (step S150), and this routine ends. When the integrated air quantity Iqa has been reset to the value 0 due to the current engine stall, the target equivalence ratio φ* is set using the integrated air quantity Iqa and the starting water temperature Tws (step S150), and this routine ends.

[0020] FIG. 3 is an explanatory diagram showing an example of the time changes in the rotational speed Ne of the engine 22, the target equivalence ratio φ*, and the integrated air quantity Iqa. In the figure, the solid line indicates an example, and the dashed line indicates a comparative example. In the comparative example, when the engine 22 is started (time t0) and then stalls (time t1), the integrated air quantity Iqa is not reset to the value 0. Therefore, when the engine 22 is restarted (time t2), the integrated air quantity Iqa is integrated from a value greater than 0, the target equivalence ratio φ* becomes smaller, falls below the value 1, and becomes 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 example, when the engine stalls (time t1), the integrated air quantity Iqa is reset to the value 0. Therefore, when the engine 22 is restarted (time t2), the integrated air quantity Iqa is integrated from 0, the target equivalence ratio φ* becomes greater than the value 1, that is, rich, and engine stalling is suppressed. Thereby, a decrease in the starting performance of the engine 22 can be suppressed.

[0021] According to the automobile 20 equipped with the engine control device of the example described above, after starting the engine 22 during cold time, the target equivalence ratio φ* is set so as to be larger when the integrated air quantity Iqa is small than when it is large, and when the engine 22 stalls after starting the engine 22 during cold time, by resetting the integrated air quantity Iqa to the value 0, a decrease in the starting performance of the engine 22 can be suppressed.

[0022] The correspondence between the main elements of the example and the main elements of the invention described in the column of means for solving the problems will be described. In the example, the ECU 30 corresponds to the "engine control device".

[0023] As described above, the embodiments for carrying out the present invention have been described using examples. However, the present invention is not limited to such examples, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Description of Reference Numerals

[0024] 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 wheel.

Claims

【Claim 1】 An engine control device that controls the engine such that, after starting the engine in cold conditions, the equivalence ratio becomes a target equivalence ratio based on the integrated air intake amount, which is the product of the coolant water temperature at the start of the engine and the integrated value of the intake air amount after starting the engine. After starting the engine in cold conditions, the target equivalence ratio is set to be larger when the integrated air intake amount is small than when it is large. When the engine stalls after starting the engine in cold conditions, the integrated air intake amount is reset to the value 0. An engine control device.

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