JP4661747B2 - Engine stop control device - Google Patents

Description

  The present invention relates to an engine stop control device, and when an engine automatic stop condition set in advance in an engine idling state or the like is satisfied, an engine that has been automatically stopped is restarted when an engine restart condition is satisfied. It belongs to the control field of the engine that automatically stops the engine while taking the above into consideration.

  In recent years, when a restart condition is established such that the engine is automatically stopped temporarily during idling to reduce fuel consumption or carbon dioxide emissions, and then the driver starts the vehicle. Thus, an automatic engine stop control, that is, a so-called idle stop control technique that automatically restarts the engine has been developed.

  For example, there exists a thing of patent document 1 regarding an idle stop control. This is because the engine can be restarted in a short time after the engine has been automatically stopped. Specifically, after the automatic stop, fuel is injected into the cylinder that is in the stopped state in the expansion stroke, and ignition and combustion are performed. By doing so, the engine is restarted. At this time, the alternator that is driven by the engine and generates power controls the rotational load acting on the engine from the alternator by controlling the power generation amount of the alternator, thereby reducing the rotational speed of the engine during the automatic stop operation. As a result, each time an automatic stop is performed, the piston is stopped at a predetermined position (for example, ATDC 100-120 deg) suitable for restarting the engine.

JP 2005-282434 A

  However, in the case of the control described in Patent Document 1, the stop position of the piston may not necessarily be a predetermined position suitable for restarting the engine for a short time. This is because the relationship between the field coil energization current value, which is the control parameter of the alternator, and the generated current value of the alternator differs depending on the temperature of the alternator. That is, even if the field coil energization current value, which is the control parameter of the alternator, is the same, the amount of power generated by the alternator may differ depending on the temperature of the alternator. As a result, the rotational load acting on the engine varies depending on the amount of power generated by the alternator, and the stop position of the piston may differ from the predetermined position.

  Therefore, the present invention provides an engine stop control device capable of accurately stopping a piston at a predetermined position suitable for restarting the engine each time an automatic stop is performed using an alternator. This is the issue.

In order to solve the above-mentioned problem, the invention according to claim 1 of the present application automatically stops the engine when a predetermined engine stop condition is satisfied, and when the predetermined engine start condition is satisfied during the stop, An engine stop control device having an automatic stop control means for automatically starting an engine, wherein the alternator is driven by the engine to generate electric power, the alternator temperature detection means for detecting the temperature of the alternator, and the alternator temperature detection means. An alternator control means for correcting the rotational load from the alternator acting on the engine during the automatic stop so that the piston stops at a predetermined position by controlling the energization current to the field coil of the alternator based on the generated alternator temperature possess the door, the alternator temperature detecting means, said alternator Characterized in that it is configured to estimate the temperature of the alternator based on a temperature-correlation characteristics with energizing current value to the generated current value and the alternator field coil motor.

The invention according to claim 2, in the stop control system for an engine according to claim 1, the automatic stop control of the engine is started by the predetermined engine stop condition is satisfied the automatic stop control means Before, the engine has a stop preparation control means for controlling the engine speed to a predetermined number, and the alternator temperature detecting means is configured so that the alternator temperature detecting means controls the alternator while the stop preparation control means is controlling the engine speed to a predetermined number. The temperature of the alternator is estimated based on a temperature correlation characteristic between a generated current value and a value of a current flowing through a field coil of the alternator .

Further, the invention according to claim 3 is the engine stop control device according to claim 1 or 2 , wherein the automatic stop control means stops at least in an expansion stroke when the predetermined engine start condition is satisfied. The engine is configured to be automatically started by injecting fuel into the cylinder in such a state to cause ignition and combustion.

  According to the engine stop control device of the first aspect of the present invention, the rotational load acting on the engine from the alternator, which varies depending on the temperature of the alternator, is corrected to a rotational load at which the piston stops at a predetermined position. The alternator is controlled based on the temperature of the alternator. As a result, the piston can be stopped at a predetermined position suitable for restart every time the engine is automatically stopped stably regardless of the temperature change of the alternator.

In this case, according to the engine stop control device, the temperature of the alternator is estimated based on the temperature correlation characteristic between the generated current value of the alternator and the current value supplied to the field coil, so that the temperature is directly detected. There is no need.

According to the engine stop control device of the second aspect , since the temperature of the alternator is always estimated under the same conditions in which the engine is rotating at a predetermined rotational speed, the temperature estimation accuracy is high. It will be a thing. The reason for doing this is that the estimation accuracy of the alternator temperature is easily affected by changes in the engine speed, and the alternator temperature estimated by changing the revolution speed is not accurate.

Further, according to the engine stop control device of the third aspect , the fuel is injected into the cylinder in a state where the piston is stopped at a predetermined position suitable for restart and stopped in the expansion stroke, and ignition and combustion are performed. By performing the above, the restartability of the engine is enhanced.

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine having an engine stop control device according to an embodiment of the present invention. The engine indicated by reference numeral 10 in the figure has a main body 16 having a cylinder head 12 and a cylinder block 14, and an ECU 18 for engine control.

  The engine body 16 is provided with four cylinders 20A to 20D, and a combustion chamber 26 is formed by inserting a piston 24 connected to the crankshaft 22 into each cylinder.

  A spark plug 28 is installed at the top of the combustion chamber 26 of each cylinder 20A to 20D so that the tip is in the combustion chamber. A fuel injection valve 30 that directly injects fuel into the combustion chamber is provided on the side of the combustion chamber 26. The fuel injection valve 30 incorporates a needle valve and a solenoid (not shown), and is driven to open for a time corresponding to the pulse width of the pulse signal input from the ECU 18 and ignites an amount of fuel corresponding to the valve opening time. It is configured to inject toward the plug 28.

  An intake port 32 and an exhaust port 34 that open toward the combustion chamber are provided in the upper part of the combustion chamber 26 of each cylinder 20A to 20D, and these ports are equipped with an intake valve 36 and an exhaust valve 38. The intake valve 36 and the exhaust valve 38 of each cylinder 20A to 20D are driven by a valve mechanism having a camshaft (not shown) so that each cylinder performs a combustion cycle at a timing having a predetermined phase difference. It is configured to open and close.

  An intake passage 40 and an exhaust passage 42 are connected to the intake port 32 and the exhaust port 34. As shown in FIG. 2, the downstream side of the intake passage 40 close to the intake port 32 is an independent branch intake passage 40a corresponding to each cylinder 20A to 20D, and the upstream end of each branch intake passage is connected to the surge tank 40b. Communicate. A common intake passage 40c is provided upstream of the surge tank 40b, and a throttle valve 46 driven by an actuator 44 is provided in the common intake passage. An air flow sensor 48 that detects the intake air flow rate is disposed upstream of the throttle valve 46, and an intake pressure sensor 50 that detects the intake pressure (negative pressure) is disposed downstream of the throttle valve 46.

  Further, the engine body 16 is provided with an alternator (generator) 52 connected to the crankshaft 22 by a timing belt or the like. The alternator 52 adjusts the amount of power generated by adjusting the output voltage using a current supplied to a field coil (not shown) (hereinafter referred to as “fduty”, the magnitude of which is expressed as a percentage of the maximum value) as a control parameter of the alternator. The regulator circuit 52a is built in, and based on a control signal from the ECU 18 input to the regulator circuit 52a, the amount of power generation corresponding to the electric load of the vehicle, the voltage of the battery, and the like is executed.

  Further, the engine 10 is provided with two crank angle sensors 54 and 56 for detecting the rotation angle of the crankshaft 22, and the rotation speed of the engine is detected based on the detection signal output from one crank angle sensor 54. At the same time, the rotation direction and rotation angle of the crankshaft 22 are detected based on detection signals out of phase output from both sensors.

  The ECU 18 includes a cam angle sensor 58 for detecting a specific rotational position for cylinder identification provided on the camshaft, a water temperature sensor 60 for detecting the coolant temperature of the engine, and an accelerator opening corresponding to the accelerator operation amount of the driver. Each detection signal output from each accelerator sensor 62 that detects the degree is input.

  The ECU 18 receives detection signals from the sensors 48, 50, 54 to 62, outputs a control signal for controlling the fuel injection amount and injection timing to the fuel injection valve 30, and supplies the ignition plug 28 with a control signal. A control signal for controlling the ignition timing is output to the attached ignition device 64.

As will be described later, the ECU 18 automatically stops fuel injection into each cylinder 20A to 20D at a predetermined timing (fuel cut F / C) when a preset automatic engine stop condition is satisfied. The engine is stopped at the same time, and a control for automatically restarting the engine is executed when a restart condition is satisfied, for example, when an accelerator operation is performed by the driver.

  The engine is restarted by injecting fuel into at least one cylinder that has been stopped in the expansion stroke after the automatic stop of the engine to cause ignition and combustion. Therefore, in order to properly restart the engine simply by igniting the fuel injected into the cylinder stopped in the expansion stroke, the engine is automatically stopped so that a sufficient amount of air can be secured in the cylinder. In other words, it is necessary to stop the piston at a predetermined position at a corresponding position with good reproducibility.

  From now on, the contents of the automatic stop control of the engine which automatically stops the engine so that a sufficient amount of air can be secured in the cylinder performed by the ECU 18, that is, stops the piston at a predetermined position at a corresponding position with high reproducibility will be described. To do.

  The description will be made with reference to the engine automatic stop control flow shown in FIG. 3 and the engine automatic stop timing chart shown in FIG.

  As shown in FIG. 3, it is determined in step 100 whether or not the vehicle speed is 0 km / h. When the vehicle speed is 0 km / h, the routine proceeds to step 110. If not, return to START.

  In step 110, it is determined whether an idle stop condition is satisfied. For example, after confirming that the vehicle speed of 0 km / h has continued for a predetermined time, an engine automatic stop flag is set as shown in FIG. 4 and the idle stop condition is satisfied. If it is determined that the idle stop condition is satisfied, the process proceeds to step 120. If not, go back to the start.

  In step 120, after the idle stop condition is established, the ECU 18 increases the engine speed, which was 500 rpm at the time of idling, to about 900 rpm, sets the boost pressure to −320 mmHg, and sets the throttle opening to 0.1 as shown in FIG. Take control. This is for scavenging the combustion gas in the cylinder and for estimating the temperature of an alternator described later. Hereinafter, the control performed during the period from the establishment of the idle stop condition to the fuel cut (F / C) described later is referred to as stop preparation control (that is, the ECU 18 functions as stop preparation control means).

  Next, in step 130, the alternator's fduty (current applied to the field coil) is controlled to a predetermined value. For example, it is controlled to a certain value in the range of 30 to 50% (in the figure, 50%).

  In the following step 140, it is determined whether or not the engine speed is within a predetermined range, that is, whether or not it is about 900 rpm controlled in step 120. When the engine speed is about 900 rpm, the routine proceeds to step 150. Otherwise, step 140 is repeated until the engine speed reaches about 900 rpm.

  In step 150, the temperature state of the alternator is estimated. The temperature state of the alternator is estimated based on the temperature correlation characteristic between the generated current value of the alternator and the current value (fduty) applied to the field coil, which is experimentally obtained in advance, as shown in FIG. Therefore, it is not necessary to directly detect the temperature of the alternator with a temperature sensor or the like.

  FIG. 5A shows the temperature correlation characteristics of an alternator with an engine speed of 900 rpm. The power generation current of the alternator can be obtained from the power generation amount and the battery voltage. The energization current (fduty) to the field coil is the value set in step 130.

  For example, when the generated current of the alternator is 60 A and the fduty is 50%, it can be seen from the temperature correlation characteristics of FIG. 5A that the alternator is in a relatively low temperature state.

  Thus, the temperature state of the alternator is estimated after the engine is brought into a specific state through steps 120-140. This is because the temperature state of the alternator is always estimated under the same conditions. As a result, the temperature estimation accuracy is high. The reason why the alternator temperature state is always estimated under the same conditions (especially with respect to the engine speed) is that the estimation accuracy of the alternator temperature is easily affected by changes in the engine speed, and the speed is estimated to change. This is because the generated alternator temperature is not accurate.

  The relationship between the current (fduty) applied to the field coil of the alternator and the generated current varies depending on the temperature of the alternator. This is considered to be due to Joule heat generated when the current flows.

  When the temperature state of the alternator is known, in step 160, the ECU 18 performs fuel cut (F / C). As shown in FIG. 4, the F / C start flag is set. Hereinafter, the control from when the F / C is started until the engine stops is referred to as stop control (that is, the ECU 18 functions as an automatic stop control means).

  In step 170, the throttle opening is increased to 0.3.

  In the following step 180, the alternator fduty is controlled to 100%, that is, the alternator is caused to generate maximum power.

  In step 190, it is determined whether the engine speed is equal to or less than a predetermined value. In step 170, the throttle opening is increased to 0.3, and the power generation amount of the alternator is maximized in step 180, so that the engine sucks and the rotational speed decreases due to the rotational load applied from the alternator. . When the number of rotations has decreased to a predetermined value or less, for example, 600 rpm or less, which is smaller than the previous 900 rpm, the process proceeds to step 200. Otherwise, step 190 is repeated until the engine speed falls below a predetermined value.

  In step 200, the throttle opening is controlled to zero.

  In step 210, whether the engine speed is within a predetermined range, that is, within a range that is equal to or less than the speed determined in step 190 due to intake resistance acting on the piston when the throttle opening becomes zero. Determined. For example, it is determined whether or not the range is around 550 rpm. When the engine speed is within the predetermined range, the routine proceeds to step 220. Otherwise, step 210 is repeated until the engine speed is within a predetermined range.

  In step 220, a current value (fduty) applied to the field coil is set. More specifically, the fduty value is set so that a predetermined rotational load from the alternator, that is, a predetermined rotational load that stops the piston at a predetermined position, acts on the engine during the automatic stop.

  To explain, a predetermined rotational load acting on the engine from the alternator corresponds to a predetermined power generation amount of the alternator. Since the predetermined power generation amount is obtained from the power generation current of the alternator and the battery voltage, the fduty may be set so that the alternator generates power using the predetermined power generation current corresponding to the predetermined rotational load as the target power generation current.

  Specifically, the fduty is obtained from the temperature correlation characteristics between the fduty at the engine speed in step 210 and the generated current and the temperature state of the alternator estimated in step 150.

  For example, when the alternator is in a low temperature state as described above, the engine speed in step 210 is 550 rpm, and the above-described target generated current is 60 A, based on the temperature correlation characteristics shown in FIG. It can be seen that the fduty to be set is about 65%.

  In summary, under the control in step 220, the fduty is appropriately set based on the temperature of the alternator, and the rotational load acting on the engine is corrected to a predetermined rotational load.

  The engine stop control is continued in step 230 with the fduty set appropriately, that is, with a predetermined rotational load applied to the engine.

  In step 240, the engine is completely stopped, and the automatic engine stop control is terminated.

  According to the present embodiment, the rotary load acting on the engine from the alternator is a predetermined load in the automatic engine stop operation regardless of the temperature state of the alternator. It is possible to stop at a predetermined position suitable for starting with high reproducibility. In addition, the engine can be provided with high restartability by injecting fuel into the cylinder stopped in the expansion stroke to cause ignition and combustion.

  The present invention has been described above by taking one embodiment as an example, but the present invention is not limited to this.

  For example, in the case of the above-described embodiment, the temperature of the alternator is estimated from the characteristics, but it may be measured directly by a temperature sensor or the like.

  The timing for estimating the temperature of the alternator may be any time as long as the engine speed is stable. However, the timing immediately before the automatic engine stop control is preferable because of less temperature fluctuation.

  Further, the fduty setting may be updated a plurality of times until the engine is completely stopped.

1 is a schematic configuration diagram of an engine including an engine automatic stop device according to an embodiment of the present invention. It is a schematic block diagram of another engine including the engine automatic stop apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the flow of an engine automatic stop. It is a timing chart until the engine corresponding to FIG. 3 stops automatically. In an alternator, it is a figure which shows the temperature correlation characteristic of the electric current which flows into the field coil which changes with engine rotation speeds, and a generated electric current.

Claims (3)

An engine stop control device having automatic stop control means for automatically stopping the engine when a predetermined engine stop condition is satisfied and automatically starting the engine when the predetermined engine start condition is satisfied during the stop. And
An alternator driven by an engine to generate electricity,
Alternator temperature detecting means for detecting the temperature of the alternator;
By controlling the current supplied to the field coil of the alternator based on the alternator temperature detected by the alternator temperature detecting means, the piston stops the rotational load from the alternator acting on the engine during the automatic stop at a predetermined position. It possesses a alternator control means for correcting as,
The alternator temperature detecting means is configured to estimate the temperature of the alternator based on a temperature correlation characteristic between a generated current value of the alternator and a current value supplied to a field coil of the alternator. Engine stop control device. In the engine stop control device according to claim 1,
Before the predetermined engine stop condition is established, and before the automatic stop control of the engine by the automatic stop control means is started, has stop preparation control means for controlling the engine speed to a predetermined number,
The alternator temperature detection means has a temperature correlation characteristic between the generated current value of the alternator and the current value supplied to the field coil of the alternator while the stop preparation control means controls the engine speed to a predetermined number. An engine stop control device configured to estimate a temperature of the alternator on the basis thereof. In the engine stop control device according to claim 1 or 2 ,
The automatic stop control means automatically starts the engine by injecting fuel to cause ignition and combustion at least in a cylinder stopped in the expansion stroke when the predetermined engine start condition is satisfied. An engine stop control device characterized by being configured.

Images