JP2016065467A - Engine start control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine start control device which can improve the startability of an engine.SOLUTION: An engine start control device comprises: a fuel injection valve 21 which injects fuel to each cylinder of an engine 2; a crank angle sensor 24 which outputs a crank angle signal for generating a pulse every time a crankshaft 2a of the engine 2 rotates at a prescribed angle; an angular speed detection part 31 which detects an angular speed of the crankshaft 2a of the engine 2; and a control part 32 which decreases a fuel injection amount of the engines 2 when it is determined that a rise amount of the angular speed of the crankshaft 2a which is detected by the angular speed detection part 31 at a prescribed time interval is larger than an angular speed rise amount threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine start control device, and more particularly to an engine start control device that starts by fuel injection.

  In an internal combustion engine type engine, the fuel injection amount is increased at the start-up compared to the normal operation after the complete explosion of the engine. On the other hand, in the normal operation after the engine is completely exhausted, the air-fuel ratio becomes rich with the fuel injection amount at the time of starting, so it is necessary to reduce the fuel injection amount.

  In Patent Document 1, when starting the engine, the fuel injection amount is gradually increased from the start of cranking of the engine by the starter motor until reaching the upper limit fuel injection amount, and after the cranking by the starter motor is completed, the fuel injection amount is set. It is described that the normal fuel injection amount is set when the engine reaches the complete explosion speed by gradually reducing the engine speed. As a result, it is possible to prevent the air-fuel ratio from becoming over-rich when the engine is started, and it is possible to increase the engine speed smoothly and to quickly start up the engine.

JP 2001-173490 A

However, in such an engine start control device, since the reduction of the fuel injection amount of the engine is started when the cranking is completed, the engine speed increases depending on the engine state such as the engine temperature. Otherwise, the engine may fail to start.
SUMMARY OF THE INVENTION An object of the present invention is to provide an engine start control device that can improve engine startability.

  One aspect of the invention of an engine start control device that solves the above-described problems is an engine start control device that starts by fuel injection, and includes an angular speed detection unit that detects the angular speed of the crankshaft of the engine, and during engine startup. A control unit that reduces the fuel injection amount to the engine when it is determined that the increase amount of the angular velocity of the crankshaft detected by the angular velocity detection unit is equal to or greater than the angular velocity increase amount threshold value.

  Thus, according to one aspect of the present invention, the startability of the engine can be improved.

FIG. 1 is a conceptual block diagram showing an engine start control device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an engine start control device according to an embodiment of the present invention, and is a flowchart for explaining a start-up fuel injection amount control processing procedure. FIG. 3 is a diagram showing an engine start control device according to an embodiment of the present invention, and is a time chart in the start time fuel injection amount control process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, a vehicle 1 equipped with an engine start control device according to an embodiment of the present invention includes an engine 2 and an ECU (Engine Control Unit) 3.

The engine 2 is composed of an in-line four-cylinder diesel engine having at least one, for example, four cylinders # 1 to # 4, and includes a fuel supply device (not shown). The fuel supply device has a fuel injection valve 21 corresponding to each cylinder. The engine 2 is not limited to the in-line four cylinders, and may be, for example, a V-type engine, and the number of cylinders is not particularly limited to four.
The fuel injection valve 21 is connected to the ECU 3, and under the control of the ECU 3, the amount of fuel injected into each cylinder and the injection timing are individually adjusted.

  The engine 2 includes a piston, a cylinder, a connecting rod, and the like (not shown), and performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston reciprocates the cylinder twice. It is composed of a four-cycle diesel engine that directly injects fuel into compressed air and burns it.

  The piston housed in the cylinder is connected to the crankshaft 2a via a connecting rod. The connecting rod converts the reciprocating motion of the piston into the rotational motion of the crankshaft 2a.

  A starter motor 22 is connected to the crankshaft 2a via a reduction gear (not shown). The starter motor 22 cranks the engine 2 by rotating the crankshaft 2a via a reduction gear.

  The engine 2 includes a cam angle sensor 23 that outputs a cam angle signal that generates a pulse every time a cam shaft (not shown) rotates by a predetermined angle, for example, 90 degrees, and a crankshaft 2a, for example, 10 degrees. There is provided a crank angle sensor 24 for outputting a crank angle signal for generating a pulse every rotation. The cam angle sensor 23 and the crank angle sensor 24 are connected to the ECU 3 and transmit a cam angle signal and a crank angle signal to the ECU 3. Here, the engine speed is calculated by the ECU 3 based on the crank angle signal.

  Further, the ECU 3 detects the rotation angle of the crankshaft 2a based on the crank angle signal. Further, the ECU 3 can detect the timing of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke for each cylinder based on the cam angle signal and the crank angle signal.

  In the present embodiment, the operating state of the engine 2 configured as described above is controlled by the ECU 3. The ECU 3 includes a microcomputer including, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an input / output interface, and the like. The CPU has a temporary storage function of the RAM. The signal processing is performed according to a program that is used and stored in advance in the ROM. Various control constants and various maps are stored in advance in the ROM.

In addition to the cam angle sensor 23 and the crank angle sensor 24 described above, various sensors such as an ignition switch (hereinafter referred to as an IG switch) 41 are connected to the input side of the ECU 3. The IG switch 41 can be switched on and off in conjunction with an operation of an ignition key (not shown).
On the other hand, various devices such as the fuel injection valve 21 described above are connected to the output side of the ECU 3.

  When the IG switch 41 is turned on, the ECU 3 operates the starter motor 22 by supplying power to the starter motor 22 to perform cranking. Simultaneously with the start of cranking, the ECU 3 starts the engine 2 by controlling the fuel injection valve 21 to perform fuel injection of a preset basic start injection amount. Here, the basic starting injection amount is experimentally obtained in advance and stored in the ROM of the ECU 3.

  Furthermore, the ECU 3 includes an angular velocity detection unit 31 and a control unit 32. The angular velocity detection unit 31 continuously refers to the rotation angle of the crankshaft 2a detected from the crank angle signal output from the crank angle sensor 24 every unit time, and performs cranking based on the rotational displacement of the crankshaft 2a per unit time. The angular velocity of the shaft 2a is detected.

  The control unit 32 controls the fuel injection amount when the engine 2 is started. Specifically, when the IG switch 41 is turned on, the control unit 32 determines that the amount of increase in the angular speed of the crankshaft 2a at a predetermined time interval is greater than or equal to the angular speed increase threshold value while the engine speed is equal to or lower than the predetermined speed. If it is determined that there is, the fuel injection amount is decreased by a predetermined decrease amount.

  Here, the predetermined rotation speed is experimentally obtained in advance and stored in the ROM of the ECU 3. For example, the predetermined engine speed is set to an engine speed indicating that the engine 2 has completely exploded. Further, the predetermined time interval is experimentally obtained in advance and stored in the ROM of the ECU 3. The angular velocity increase threshold value is obtained experimentally in advance and stored in the ROM of the ECU 3. The angular velocity increase amount threshold is set to an increase amount of angular velocity indicating that combustion has occurred in the engine 2. Further, the predetermined amount of decrease is experimentally obtained in advance and stored in the ROM of the ECU 3.

  Further, when the fuel injection amount is decreased, the control unit 32 returns the fuel injection amount to the basic start injection amount when the angular velocity of the crankshaft 2a is decreasing at a predetermined time interval, and again for a predetermined time. It waits for the increase amount of the angular velocity of the crankshaft 2a at the interval to be equal to or greater than the angular velocity increase amount threshold value. Here, for example, the control unit 32 determines whether or not the angular velocity of the crankshaft 2a is decreasing based on whether or not the increase amount of the angular velocity of the crankshaft 2a is smaller than “0”.

  With this configuration, it is possible to prevent the engine 2 from being stopped due to a decrease in the fuel injection amount until the engine speed becomes larger than the predetermined speed.

  Instead of returning the fuel injection amount to the basic start-time injection amount, the fuel injection amount may be returned to the fuel injection amount immediately before the fuel injection amount at which the angular velocity of the crankshaft 2a is lowered.

  With this configuration, the engine 2 is stopped by increasing the minimum fuel injection amount while taking advantage of the decrease in the fuel injection amount until it is determined that the angular velocity of the crankshaft 2a has decreased. Can be prevented.

  Further, the control unit 32 decreases the fuel injection amount, and the fuel injection amount is increased when the angular speed of the crankshaft 2a does not decrease at a predetermined time interval and the engine rotational speed becomes higher than the predetermined rotational speed. Is an idle fuel injection amount that is a fuel injection amount when the engine 2 is idling. Here, the idle fuel injection amount is experimentally obtained in advance and stored in the ROM of the ECU 3.

  As the amount of increase in the angular velocity of the crankshaft 2a, the amount of increase in the angular velocity of the crankshaft 2a in the expansion stroke of each cylinder may be used. That is, the amount of increase in time series regardless of the cylinder of the angular velocity of the crankshaft 2a when the expansion stroke is reached regardless of the cylinder.

  The start time fuel injection amount control process by the engine start control device according to the present embodiment configured as described above will be described with reference to FIG. The start time fuel injection amount control process described below is started at the same time as the IG switch 41 is turned on.

  First, the control unit 32 determines whether or not the engine speed is equal to or less than the above-described predetermined speed (step S11). If it is determined that the engine speed is not less than the predetermined speed, the control unit 32 ends the process.

  On the other hand, when it is determined that the engine speed is equal to or lower than the predetermined speed, the control unit 32 calculates the amount of increase in the angular speed of the crankshaft 2a in the expansion stroke of each cylinder (step S12), and the angular speed of the crankshaft 2a. It is determined whether or not the amount of increase is equal to or greater than the angular velocity increase threshold described above (step S13). When determining that the amount of increase in the angular velocity of the crankshaft 2a is not equal to or greater than the threshold value for increasing the angular velocity, the control unit 32 returns to step S12 and waits for the amount of increase in the angular velocity of the crankshaft 2a to be equal to or greater than the threshold value for increasing angular velocity. .

  On the other hand, when it is determined that the increase amount of the angular velocity of the crankshaft 2a is equal to or greater than the angular velocity increase amount threshold value, the control unit 32 decreases the fuel injection amount by a predetermined decrease amount (step S14), The amount of increase in the angular velocity of the crankshaft 2a is calculated (step S15), and it is determined whether or not the amount of increase in the angular velocity of the crankshaft 2a is smaller than “0” (step S16). When it is determined that the amount of increase in the angular velocity of the crankshaft 2a is smaller than “0”, the control unit 32 returns the fuel injection amount to the basic start injection amount (step S17), and returns to step S12 to return to the crankshaft 2a. It waits for the amount of increase in the angular velocity to be equal to or greater than the threshold value for increasing the angular velocity.

  On the other hand, when it is determined that the amount of increase in the angular velocity of the crankshaft 2a is not smaller than “0”, the control unit 32 determines whether or not the engine speed is equal to or less than the predetermined speed described above (step S18). If it is determined that the engine speed is equal to or lower than the predetermined speed, the control unit 32 returns to step S14 and repeats the process. On the other hand, if it is determined that the engine speed is not less than the predetermined speed, the control unit 32 ends the process.

  The operation of the engine start control device of the present embodiment described above will be described with reference to FIG. In FIG. 3, the “cylinder discrimination result” indicates the cylinder number that reaches the expansion stroke.

  As shown in FIG. 3, when the IG switch 41 is turned on at t1, the starter motor 22 starts cranking as shown by “Starter Motor”, and the engine speed rises as shown by “Engine Speed”.

  If cranking continues, the engine speed will increase, and if combustion occurs, the cylinder pressure will increase like the “cylinder pressure” # 1 cylinder, and the amount of increase in the angular speed of the crankshaft 2a of “expansion stroke angular speed fluctuation” Is determined to start combustion at t2 that exceeds the angular velocity increase threshold, and the fuel injection amount shown in “fuel injection amount” is gradually reduced.

Thus, in the above-described embodiment, when it is determined that the amount of increase in the angular velocity of the crankshaft 2a detected by the angular velocity detector 31 at a predetermined time interval is greater than or equal to the angular velocity increase amount threshold value, the fuel injection amount of the engine 2 The control part 32 which decreases is provided.
As a result, the start of combustion of the engine 2 is reliably determined, and the engine start failure is prevented, and the air-fuel ratio is prevented from becoming overrich, and the engine speed is smoothly increased to start the engine 2. Can be done quickly. That is, the startability of the engine 2 can be improved.

Further, when it is determined that the amount of increase in the angular velocity of the crankshaft is equal to or greater than the angular velocity increase amount threshold value, it is preferable to decrease the fuel injection amount of the engine 2 by a preset decrease amount at preset time intervals. .
As a result, engine start failure due to a sudden decrease in fuel injection amount is prevented, and the air-fuel ratio is prevented from becoming overrich, and the engine speed is smoothly increased to start the engine 2 quickly. be able to. That is, the startability of the engine 2 can be improved.

Further, when the fuel injection amount of the engine 2 is decreased, the control unit 32 increases the fuel injection amount when the increase amount of the angular velocity of the crankshaft becomes smaller than “0”.
As a result, when the fuel injection amount of the engine 2 is reduced, the fuel injection amount is increased when the angular speed of the crankshaft becomes small and the engine 2 may stop. Thus, the startability of the engine 2 can be improved.

Further, the control unit 32 obtains the amount of increase in the angular speed of the crankshaft from the angular speed during the expansion stroke of the engine 2.
As a result, the start of combustion of the engine 2 is determined based on the fluctuation amount of the angular velocity during the expansion stroke, the start of combustion of the engine 2 can be more accurately determined, and the engine start failure can be prevented. Can be improved.

  While embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 2a Crankshaft 3 ECU (Angular velocity detection part, control part)
21 Fuel Injection Valve 22 Starter Motor 23 Cam Angle Sensor 24 Crank Angle Sensor (Angular Speed Detection Unit)
31 Angular velocity detection unit 32 Control unit 41 IG switch

Claims (4)

An engine start control device that starts by fuel injection,
An angular velocity detector for detecting the angular velocity of the crankshaft of the engine;
A control unit that decreases the fuel injection amount to the engine when it is determined that the increase amount of the angular velocity of the crankshaft detected by the angular velocity detection unit is equal to or greater than an angular velocity increase amount threshold during startup of the engine. Engine start control device.   2. The engine start control device according to claim 1, wherein when the fuel injection amount to the engine is decreased, the control unit decreases the amount of decrease set in advance at a predetermined time interval.   3. The engine according to claim 1, wherein when the fuel injection amount to the engine is decreased, the control unit increases the fuel injection amount to the engine when it is determined that the angular velocity is decreasing. Start control device. The engine start control device according to any one of claims 1 to 3, wherein the increase amount of the angular velocity is obtained based on an angular velocity during an expansion stroke of the engine.