JP4291762B2 - Engine stop control device and vehicle equipped with the same - Google Patents

Description

  The present invention relates to an engine stop control device and a vehicle equipped with the same.

Conventionally, an engine stop control device has been proposed that increases the amount of air supplied to each cylinder of an engine after the engine stop condition is satisfied (see, for example, Patent Document 1). The device described in Patent Document 1 increases the resistance due to the compression pressure generated when the piston compresses air after the engine stop condition is satisfied, and suppresses variations in the stop position of the piston. According to this engine stop control device, since the piston can be stopped at a position where the engine can be easily restarted, restartability can be improved. Further, there has been proposed one that decreases the intake pressure of air supplied to each cylinder of the engine after the engine stop condition is satisfied and increases the intake pressure after the engine stops (for example, see Patent Document 2). ). The apparatus described in Patent Document 2 reduces the resistance caused by the compression pressure of the engine after the engine stop condition is satisfied, thereby reducing vibration when the engine is stopped. Relieve pressure and optimize air-fuel ratio at restart.
JP 2001-173473 A JP 2000-257458 A

  However, in the engine stop control device described in Patent Document 1, when stopping the engine, variation in the stop position of the piston can be suppressed, but the engine vibration is large. Further, in the engine stop control device described in Patent Document 2, when stopping the engine, the vibration of the engine can be suppressed, but the stop position of the piston varies. That is, until now, there has been no known engine stop control device that achieves both the reduction of vibration when the engine is stopped and the suppression of variations in the stop position of the piston.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an engine stop control device that can reduce vibrations of the engine when the engine is stopped and suppress variations in piston stop positions. I will. Another object is to provide a vehicle equipped with such an engine stop control device.

  The present invention employs the following means in order to achieve at least a part of the above-described object.

The engine stop control device of the present invention includes:
An air amount adjusting means for adjusting the amount of air supplied to each cylinder of the engine;
Fuel injection means for injecting fuel to each cylinder;
Fuel injection control means for controlling the fuel injection amount of the fuel injection means so as to be a predetermined air-fuel ratio, and for stopping the fuel injection of the fuel injection means to the engine when an engine stop request is made;
After the engine stop request, the air amount adjusting means is controlled so that the air amount becomes small, and after controlling the air amount so as to become small, the pressure from the air amount adjusting means to the engine and information relating to the pressure An air amount adjustment control means for controlling the air amount adjustment means so that the air amount is increased based on at least one of the following:
It is equipped with.

  In this engine stop control device, after the engine stop request, the amount of air supplied to each cylinder of the engine is reduced, and after the amount of air is reduced, the air amount is adjusted based on the pressure from the air amount adjusting means to the engine or information on the pressure. Enlarge. Thus, the engine vibration can be reduced because the air amount is reduced after the engine stop request. In addition, since the air amount is increased based on the pressure from the air amount adjusting means to the engine or the information related to the pressure after reducing the air amount, it is possible to suppress variations in the piston stop position. Here, the “information about pressure” refers to information having a correlation with the pressure from the air amount adjusting means to the engine. For example, the time and the air amount after controlling to reduce the air amount are reduced. For example, the amount of change in the crank angle after control.

  Here, “injecting fuel into the cylinder” includes a case where fuel is directly injected into the cylinder of the engine and a case where fuel is injected into the intake port of the cylinder of the engine.

  In the engine stop control device of the present invention, the air amount adjusting means may control the air amount adjusting means so that the air amount becomes large when the pressure falls below a predetermined lower limit value. In this way, the air amount is increased after the negative pressure is once reached, so that the flow rate of the intake air is increased and it is easy to inhale into the cylinder. Here, the “predetermined lower limit value” may be determined, for example, as a pressure at which a sufficient air flow rate is obtained when the amount of air is increased.

  In the engine stop control device of the present invention, when the air amount adjustment control unit controls the air amount adjustment unit so that the air amount becomes large, a predetermined cylinder is moved in a predetermined stroke when the engine is stopped. The air amount adjusting means may be controlled based on the engine speed and the amount of change in the engine speed so as to stop. In this way, the air amount is controlled based on the engine speed and the amount of change in the engine speed to adjust the compression pressure of the engine, so that the piston can be easily stopped at a predetermined stop position.

  In the engine stop control device of the present invention, the air amount adjustment control means adjusts the air amount so that the air amount becomes small after the fuel injection control means stops the fuel injection of the fuel injection means by idle stop control. And controlling the air amount so that the air amount becomes large based on at least one of the pressure from the air amount adjusting means to the engine and the information related to the pressure. The means may be controlled. When the idle stop control is performed, the engine stop and restart are repeated many times during traveling, so that it is significant to apply the present invention.

  In the engine stop control device of the present invention, the fuel injection control means may cause the fuel injection means to inject fuel before the engine stops for a cylinder that stops in a compression stroke when the engine stops. Good. If it carries out like this, since it can ignite immediately after restart of an engine and the combustion energy can be obtained in the cylinder which injected and compressed fuel, it will be easy to restart. In the present invention, even if the piston immediately before the engine stops is slow, the flow rate of the intake air is increased by increasing the air amount after the pressure from the air amount adjusting means to the engine is once made negative. The air-fuel mixture in which the air and the fuel are sufficiently mixed can be put in the cylinder stopped in the compression stroke as compared with the case where the intake air flow rate is low without using negative pressure. At this time, when the engine is stopped, stop prediction means for predicting which cylinder stops in the compression stroke before the engine stops may be provided. In this way, it is possible to predict the cylinder that stops in the compression stroke and to put the fuel.

  In the engine stop control device of the present invention, when the air amount adjustment control unit controls the air amount adjustment unit so that the air amount decreases after the engine stop request, the engine speed is a predetermined low value. The air amount adjusting means may be controlled so that the air amount is minimized when the rotational speed is lower. By doing so, the compression pressure of the engine is minimized, and it is easy to reduce engine vibration. Further, since the amount of air supplied downstream of the air amount adjusting means is minimized, it is easy to make the pressure from the air amount adjusting means to the engine negative. Here, the “predetermined low rotational speed” may be determined as a rotational speed sufficiently smaller than the idling rotational speed, for example.

  In the engine stop control device of the present invention, the air amount adjusting means may be a throttle valve. In this way, it is not necessary to provide an air amount adjusting means separately from the throttle valve.

  The vehicle of the present invention is equipped with the engine stop control device according to any of the various aspects described above. Since the engine stop control device of the present invention can reduce the vibration of the engine when the engine is stopped and suppress variations in the stop positions of the pistons, a vehicle equipped with the same has the same effect.

  Next, the best mode for carrying out the present invention will be described using examples.

  FIG. 1 is a configuration diagram showing an outline of a configuration of a gasoline vehicle 10 that performs idle stop control according to an embodiment of the present invention. As shown in FIG. 1, the gasoline automobile 10 includes an engine 20 driven by gasoline and an engine electronic control unit (hereinafter referred to as an engine ECU) 50 that controls the engine 20. The engine ECU 50 corresponds to the fuel injection control means and the air amount adjustment control means of the present invention.

  The engine 20 is a four-cylinder engine in this embodiment, and each cylinder 20a has an injector 23 (corresponding to fuel injection means of the present invention) in an intake port 23a provided upstream of the intake valve 24 in the intake passage 31. Is configured as a port type that injects gasoline. Each cylinder of the engine 20 repeats this cycle by taking an intake stroke, a compression stroke, an expansion stroke (also referred to as a combustion stroke), and an exhaust stroke as one cycle, and each time the crankshaft 37 is rotated half a turn, that is, 180 °. Each time the stroke is switched, the cycle advances one cycle each time the crankshaft 37 rotates twice, that is, 720 °. In this embodiment, the ignition timings of the four cylinders are in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. Therefore, for example, when the first cylinder is in the expansion stroke, the second cylinder is exhausted. The stroke, the third cylinder is the compression stroke, and the fourth cylinder is the intake stroke. FIG. 2 shows the correspondence between the crank angle CA and the stroke of each cylinder. In FIG. 2, TDC represents top dead center and BDC represents bottom dead center. FIG. 2 also shows a stop period when each cylinder stops in the compression stroke.

  In the intake passage 31 of the engine 20, an air cleaner 21, a throttle valve 22 (corresponding to the air amount adjusting means of the present invention), a pressure sensor 28, and an injector 23 are arranged from upstream. The air sucked into the intake passage 31 through the air cleaner 21 and the throttle valve 22 is mixed with gasoline injected from the injector 23 through the suction port 23a to become an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 32 by opening the intake valve 24, ignited by the spark of the spark plug 25, and explosively burned. The piston 33 reciprocates by the combustion energy, and the crankshaft 37 rotates. Let The exhaust gas after combustion is discharged from the combustion chamber 32 when the exhaust valve 26 is opened. The throttle valve 22 is connected to a throttle motor 22a for adjusting the opening (position) of the throttle valve 22 and a throttle valve position sensor 22b for detecting the opening of the throttle valve 22. The degree S is adjusted.

  The pressure sensor 28 is a sensor that outputs a pressure converted into a voltage by a silicon diaphragm type pressure conversion element, and is disposed in the intake passage 31 between the throttle valve 22 and the intake valve 24 (near the intake port 23a). The pressure Pe in the vicinity of the port 23a is detected. Since the pressure sensor 28 shows a substantially linear relationship between the pressure and the voltage, the pressure can be directly obtained from the output voltage value. The pressure Pe is obtained by using the output value of the pressure sensor 28, and this pressure Pe is used for automatic stop control described later, or the intake air amount used for air-fuel ratio control is grasped from the pressure Pe and the engine speed Ne. To do.

  The crankshaft 37 of the engine 20 is connected to the automatic transmission 17 via the drive shaft 16. The automatic transmission 17 shifts the power output from the engine 20 to the crankshaft 37 and transmits it to the drive wheels 19 and 19 via the differential gear 18. A crank angle sensor 27 is attached to the crankshaft 37, and a cam angle sensor 36 is attached to the camshafts 34a and 35a on which cams 34 and 35 for opening and closing the intake valve 24 and the exhaust valve 26 are arranged. Among these, the crank angle sensor 27 is an MRE rotation sensor in which a magnetoresistive element is arranged at a position facing a magnet rotor (not shown) attached to the crankshaft 37, and is pulsed every predetermined angle (for example, crank angle 10 ° CA). Is output. A crank angle CA is specified or an engine speed Ne is obtained by using a pulse generated by the crank angle sensor 27. The cam angle sensor 36 is an electromagnetic induction pickup type sensor that outputs a pulse each time the gear teeth rotating integrally with the camshafts 34a and 35a approach the coil core, and the camshaft rotates once ( Each time the crankshaft 37 is rotated twice), one pulse is generated.

  The engine ECU 50 controls the operation of the engine 20, and is configured as a microprocessor centered on the CPU 52. The ROM 54 stores a processing program, a RAM 56 temporarily stores data, an input / output port ( (Not shown). The engine ECU 50 includes various sensors that indicate the operating state of the engine 20, for example, the throttle valve position sensor 22b, the crank angle sensor 27, the pressure sensor 28, and the cam angle sensor 36 described above. An intake air temperature sensor that detects the temperature, a water temperature sensor that detects the temperature (water temperature) of the cooling water of the engine 20, and the like are connected, and detection signals from various sensors are input. The engine ECU 50 outputs a drive signal to the throttle motor 22a, a drive signal to the injector 23, a control signal to the ignition coil 29 that applies a discharge voltage to the spark plug 25, and the like. In order to output the required power based on the driver's operation from the engine 20, the engine ECU 50 has the shift position SP from the shift position sensor 82 that detects the operation position of the shift lever 81 and the depression amount of the accelerator pedal 83. Signals such as the accelerator opening Ac from the accelerator pedal position sensor 84 to be detected, the brake pedal position BP from the brake pedal position sensor 86 to detect the depression amount of the brake pedal 85, and the vehicle speed V from the vehicle speed sensor 88 are also input via the input port. Have been entered.

  Next, the operation of the gasoline automobile 10 of the present embodiment, particularly the operation associated with the idle stop control will be described below. In the gasoline automobile 10, the engine 20 is automatically stopped when a predetermined stop condition is satisfied, and thereafter, idle stop control is performed in which the engine 20 is automatically restarted when a predetermined restart condition is satisfied. Below, the automatic stop control routine performed by this idle stop control is demonstrated.

  FIG. 3 is a flowchart of this automatic stop control routine. This routine is executed by the engine ECU 50 at predetermined timings (for example, every several msec) during engine operation. When this routine is started, the engine ECU 50 determines that the accelerator opening Ac from the accelerator pedal position sensor 84 is accelerator OFF, the brake pedal position from the brake position sensor 86 is brake ON, and the vehicle speed V is 0. It is determined whether stop conditions are met (step S100). When the predetermined stop condition is not met, this routine is finished as it is. On the other hand, when predetermined stop conditions are met, the energization to the injector 23 of each cylinder 20a of the engine 20 is stopped and the energization to the spark plug 25 is stopped (step S110). As a result, since the ignition and fuel injection of each cylinder 20a of the engine 20 are stopped, the engine 20 does not generate torque for rotating the crankshaft 37. For this reason, the crankshaft 37 rotates only with an inertial force. Since this inertial force is attenuated by the compression pressure generated in the cylinder in the compression stroke, the rotation of the crankshaft 37 converges toward the stop.

  Next, the engine ECU 50 determines whether or not the engine speed Ne has fallen below a predetermined threshold value Nth (step S120), and when the engine speed Ne has not fallen below the predetermined threshold value Nth. If the engine speed Ne falls below a predetermined threshold value Nth, it is predicted as to which cylinder will be the compression stroke cylinder at the time of stop (step S125), and the throttle opening S at which the intake air amount is minimized. That is, the throttle motor 22a is controlled so that the throttle opening S becomes 0 ° (step S130). The predetermined threshold value Nth is set to a rotational speed sufficiently lower than the idle rotational speed. However, it is assumed that the crankshaft 37 rotates at least 2 to 3 cycles after the engine speed Ne becomes equal to or lower than a predetermined threshold value Nth. Further, the throttle opening S is defined by the angle of the throttle valve 22, and when the throttle opening S is 0 °, it is in a fully closed state, and when it is 90 °, it indicates a fully open state. The throttle opening S before the throttle opening S is set to 0 ° is an idling opening that maintains the idling speed.

  Here, an example of a method for predicting the compression stroke cylinder at the time of stop is shown below. First, after the engine 20 is rotated only by inertial force, the crank angle when the engine speed Ne is attenuated by the compression pressure and the engine speed Ne reaches a predetermined threshold value Nth, and then in the vicinity of the suction port 23a. When the pressure Pe falls below a predetermined lower limit value Pmin, control is performed to make a predetermined throttle opening degree Sc (see below), and the relationship with the crank angle when the engine 20 is stopped after being further attenuated. Obtain a map experimentally. In step S120, the crank angle CA when the engine speed Ne is equal to or smaller than the predetermined threshold value Nth is obtained, and the crank angle CA at the time of engine stop corresponding to the crank angle CA is read from the previous map. The compression stroke cylinder at the time of stop is predicted from the correspondence relationship between the crank angle CA of 2 and the stroke of each cylinder. The crank angle CA is obtained based on the pulse output from the crank angle sensor 27 and the pulse output from the cam angle sensor 36. In this embodiment, the cam angle sensor 36 is set to output a pulse every time the first cylinder enters the expansion stroke, and the crank angle sensor 27 rotates the crankshaft 37 by a predetermined angle (for example, a crank angle of 10 ° CA). It is set to output a pulse every time. Therefore, the crank angle is reset to zero each time a pulse is output from the cam angle sensor 36, and the crank angle is advanced by a predetermined angle each time a pulse is output from the crank angle sensor 27, so that the crank angle is reduced to zero. It can be calculated in a range of ˜720 °.

  Subsequently, the engine ECU 50 determines from the output value of the pressure sensor 28 whether or not the pressure Pe in the vicinity of the suction port 23a falls below a predetermined lower limit value Pmin (step S140), and the pressure Pe is lower than the predetermined lower limit value. If it is not less than Pmin, the process waits as it is, and when the pressure Pe falls below a predetermined lower limit value Pmin, the throttle motor 22a is controlled so that the throttle opening S becomes the predetermined throttle opening Sc (step S150). Here, the predetermined lower limit value Pmin is set to a negative pressure such that a sufficient air flow rate is obtained at the intake port 23a when the air amount is increased as the predetermined throttle opening degree Sc. The predetermined throttle opening degree Sc is determined as a value such that the compression pressure of the engine increases and the piston 33 stops at a predetermined stop position in the compression stroke. Here, the predetermined throttle opening degree Sc is set to 20 °. The predetermined threshold value Nth, the predetermined lower limit value Pmin, and the predetermined throttle opening degree Sc are the stop intervals of the compression stroke of the piston 33 when performing a series of operations from the fuel cut to the engine stop in step S110. Relevant to stop at.

  Next, the engine ECU 50 determines whether or not the predicted stop-time compression stroke cylinder has reached the intake stroke immediately before the stop (step S160). This determination is based on the engine speed Ne obtained from the pulse of the crank angle sensor 27 to determine whether or not the compression stroke cylinder at the time of stop is immediately before stopping, and the crank angle obtained as described above is determined as the crank angle shown in FIG. This is performed by determining which stroke the compression stroke cylinder at the time of stop is in light of the correspondence between CA and the stroke of each cylinder. For example, when the stop-time compression stroke cylinder is the third cylinder, as shown in FIG. 2 (c), the intake stroke starts when the crank angle reaches 180 °, and the timing immediately before the intake stroke is 180 °. -Α.

  In step S160, when the stop-time compression stroke cylinder has not reached the timing immediately before the intake stroke, the process waits as it is, and when the stop-time compression stroke cylinder has reached the timing immediately before the intake stroke, the injector 23 of that cylinder is energized. Fuel is injected (step S170), and this routine ends. As a result, the fuel injected from the injector 23 is mixed with the air in the intake port 23a to become an air-fuel mixture, and the air-fuel mixture is sucked into the combustion chamber 32 of the stop-time compression stroke cylinder when the intake valve 24 is opened. . Thereafter, the piston 33 receives the compression pressure of the air-fuel mixture and stops within the stop section.

  FIG. 4 is a timing chart when the engine 20 is stopped. A series of operations will be described with reference to FIG. First, after a predetermined stop condition is satisfied, when the engine speed Ne falls below a predetermined threshold value Nth (t1), the engine ECU 50 predicts a stop-time compression stroke cylinder (here, the third cylinder). The throttle opening S is set to 0 °. Then, the pressure Pe in the vicinity of the suction port 23a decreases. When the pressure Pe falls below a predetermined lower limit value Pmin, the air amount is increased with the throttle opening S as the predetermined throttle opening Sc (t2). If the throttle opening Sc is set to a predetermined value, the amount of air taken into the cylinder increases and the compression pressure generated in the cylinder in the compression stroke increases, so the engine speed converges rapidly toward the stop. When the third cylinder reaches the intake stroke immediately before stopping, fuel is injected into this cylinder. At this time, since the air amount is increased after the pressure Pe is once set to a negative pressure, the flow rate of the intake air at the time of fuel injection is high even when the movement of the piston is slow. After that, the third cylinder receives the compression pressure of the air-fuel mixture and cannot overcome the top dead center leading to the expansion stroke (t3), and stops in the position near the front of the TDC, that is, in the stop section of FIG. t4). At this time, the crankshaft 37 rotates in the reverse direction by the amount that the piston 33 is pushed down and stops (t3-t4).

  Next, a case where the engine is restarted will be described. After the automatic stop control routine, the engine ECU 50 restarts the engine 20 when a predetermined start condition such as turning off the brake and turning on the accelerator is satisfied. Specifically, the engine ECU 50 cranks the engine 20 with a starter motor (not shown), applies a discharge voltage to the spark plug 25 immediately before the stop-time compression stroke cylinder reaches the expansion stroke, and generates a spark. Ignite the cylinder. Then, immediately after cranking by the starter motor, the air-fuel mixture confined in this cylinder before the engine stops burns to generate combustion torque to assist the cranking. For this reason, the engine 20 can be easily restarted.

  According to the gasoline automobile 10 of the present embodiment described in detail above, after the engine stop request, the amount of air supplied to each cylinder of the engine 20 is reduced, and then the pressure Pe (from the throttle valve 22 to the intake valve 24) Based on the pressure in the vicinity of the suction port 23a), the throttle valve 22 is controlled so as to reach a predetermined throttle opening Sc at which the air amount increases. Thus, the vibration of the engine 20 can be reduced because the air amount is reduced after the engine stop request. Further, since the air amount is increased based on the pressure in the vicinity of the suction port 23a after the air amount is decreased, variations in the piston stop position can be suppressed.

  Further, when the pressure in the vicinity of the suction port 23a falls below a predetermined lower limit value Pmin, the air amount is increased, that is, the air amount is increased after the negative pressure state is once set. Easy to inhale.

  Furthermore, the gasoline automobile 10 of the present embodiment performs idle stop control, and when the idle stop control is performed, the engine stop and restart are repeated many times during traveling. Therefore, it is significant to apply the present invention.

  Furthermore, a cylinder that stops in the compression stroke when the engine 20 is stopped is predicted, and the fuel is injected into the cylinder 23 before the engine 20 stops, so that the fuel is injected and compressed. The cylinder can be ignited immediately after the engine 20 is restarted to obtain combustion energy, which is easy to restart. Further, even when the movement of the piston immediately before the engine stops is slow, the pressure in the vicinity of the suction port 23a is once reduced to a negative pressure and then the amount of air is increased to increase the flow rate of the intake air. Compared with a low flow velocity, the air-fuel mixture in which air and fuel are sufficiently mixed can be put in a cylinder that stops in the compression stroke. For this reason, the misfire at the time of igniting a specific cylinder at the time of engine restart can be reduced. In addition, it is possible to predict the cylinder to be stopped in the compression stroke and to put fuel.

  Then, when the throttle valve 22 is controlled so that the air amount becomes small after the engine stop request, the air amount is minimized (the throttle opening is 0 °) when the rotational speed Ne of the engine 20 falls below a predetermined low rotational speed Nth. ), The compression pressure of the engine 20 is minimized, and the vibration of the engine 20 is easily reduced. Further, since the amount of air supplied downstream of the throttle valve 22 is minimized, the pressure from the throttle valve 22 to the engine 20 can be easily made negative.

  In addition, the means for adjusting the air amount adjusts the air amount by the throttle valve, so that it is not necessary to provide a valve for adjusting the air amount separately from the throttle valve.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, fuel is put in a specific cylinder in the automatic stop control routine, but the piston stops at a piston stop position where the engine can be easily started without putting fuel in the specific cylinder. You may control as follows. The engine startability depends on the piston stop position because the force required to compress the air sucked into the cylinder and the time from cranking to the first explosion vary depending on the piston stop position. Therefore, if the piston is stopped at a piston stop position at which the engine 20 is easy to restart (for example, near a crank angle of 120 ° in FIG. 2), the startability is improved compared to the piston having a different stop position. Can do. The engine stop control device may be applied to a normal vehicle that does not perform idling stop control.

  In the above-described embodiment, the air amount is increased when the pressure Pe in the vicinity of the suction port 23a falls below the predetermined lower limit value Pmin. However, as information on the pressure Pe, the throttle opening S is set to 0 ° in step S130. The engine ECU 50 may control the throttle valve 22 so that the air amount increases when the elapsed time exceeds a predetermined time. Here, the predetermined time is a time after the throttle opening S is set to 0 °, and is determined as an empirically obtained time during which the pressure Pe falls below the predetermined lower limit value Pmin. Alternatively, the amount of change in the crank angle after the throttle opening S is set to 0 ° in step S130 is used as information on the pressure Pe, and the engine ECU 50 determines that the amount of air when the amount of change in the crank angle exceeds a predetermined angle. You may control the throttle valve 22 so that it may become large. Here, the predetermined angle is the change amount of the crank angle after the throttle opening S is set to 0 °, and the change amount of the crank angle at which the pressure Pe falls below the predetermined lower limit value Pmin is obtained empirically. It is defined as. Even in such a case, it is possible to reduce vibration of the engine 20 when the engine is stopped and to suppress variations in the stop position of the piston 33.

  Further, in the above-described embodiment, when the pressure Pe in the vicinity of the suction port 23a falls below a predetermined lower limit Pmin, the throttle opening S is set to a predetermined throttle opening Sc that is a constant value. However, the throttle opening S may be adjusted based on the engine speed Ne and the change amount ΔNe of the engine speed so that the cylinder predicted in step S125 is reliably stopped in the compression stroke. In the above-described embodiment, the cylinder predicted according to a certain empirical rule after the stop condition is satisfied is stopped in the compression stroke at the time of stop, but the cylinder as expected may not always stop in the stop section due to the influence of disturbance or the like. The cylinder predicted by adjusting the throttle opening S to control the compression pressure is more accurately stopped in the stop section. Specifically, as shown in FIG. 5, a basic engine speed change curve in which the cylinder predicted at the throttle opening degree Sc stops in the compression stroke is determined empirically. And after performing the process of step S100-S140 of the automatic stop control routine mentioned above, it is set as the predetermined throttle opening Sc (step S150). Next, the engine speed Ne and the change amount ΔNe of the engine speed are obtained from the pulse of the crank angle sensor 27 and the change of the pulse, and the actual engine speed is calculated using the engine speed Ne and the change amount ΔNe. The throttle opening 22 is corrected so that Ne matches the basic engine speed change curve, and the throttle valve 22 is controlled so that the corrected throttle opening is obtained. In this way, in order to control the air amount and adjust the compression pressure of the engine based on the engine speed Ne and its change amount ΔNe, the cylinder predicted in step S125 is stopped so as to become the compression stroke cylinder at the time of stop. Cheap.

  Furthermore, in the above-described embodiment, the throttle valve 22 is controlled so that the throttle opening S becomes 0 ° when the engine speed Ne falls below the predetermined low speed Nth in S130. Alternatively, the throttle valve 22 may be controlled so that the throttle opening S becomes small (for example, idling opening). Even in this case, since the amount of air supplied to the suction port 23a is small and the pressure Pe becomes a constant negative pressure, the vibration of the engine when the engine is stopped can be reduced and the variation in the stop position of the piston can be suppressed.

  In the embodiment described above, the compression stroke cylinder when the engine is stopped is predicted. However, the engine stop control may be performed so that a specific cylinder (for example, the third cylinder) becomes the compression stroke cylinder when the engine is stopped. . For example, control (for example, control using a starter motor as a generator) may be performed so that the third cylinder becomes a compression stroke cylinder when stopped. Alternatively, the compression stroke cylinder when the engine is stopped may be sequentially changed every time the idle stop control is executed. When the compression stroke cylinder when the engine is stopped is fixed to a specific cylinder, the state of the cylinder may be different from other cylinders as the idle stop control is repeated. Is less likely to do that.

  In the above-described embodiment, the MRE rotation sensor is employed as the crank angle sensor 56. However, a Hall element is disposed at a position facing the magnet rotor attached to the crankshaft 37 to convert the magnetic flux density change into a voltage change. A magnetoelectric conversion sensor may be employed, or a photoelectric sensor that detects a crank angle by rotating a disk with a light-emitting diode and a phototransistor facing each other and cutting a slit therebetween may be employed. You may employ | adopt the electromagnetic induction pick-up type sensor which outputs a pulse whenever the tooth | gear of the gear rotating integrally with the crankshaft 37 approaches the core of a coil. However, considering that good output can be obtained even when the crankshaft 37 rotates at a low speed, an MRE rotation sensor, a magnetoelectric conversion sensor, or a photoelectric sensor is preferable.

  Furthermore, in the above-described embodiments, the description has been given by taking the four-cylinder engine as an example, but the present invention can be similarly applied to other multi-cylinder engines.

  Furthermore, in the above-described embodiments, the port type in which fuel is injected into the intake port is adopted as the fuel injection method, but a direct injection type in which fuel is directly injected into the cylinder may be adopted.

  Further, in the above-described embodiment, the case where the present invention is applied to the gasoline vehicle 10 that performs the idling stop control is illustrated. However, the present invention is applied to a hybrid vehicle configured to transmit the power of the engine and the motor generator to the vehicle drive shaft. May be.

It is a block diagram which shows the outline of a structure of the gasoline automobile 10 of a present Example. It is explanatory drawing showing the correspondence of crank angle CA and the stroke of each cylinder. It is a flowchart of the automatic stop control routine of a present Example. It is a timing chart at the time of the stop of the engine 20 of a present Example. FIG. 5 is an explanatory diagram of control of the throttle opening when the engine 20 is stopped.

Explanation of symbols

  10 Gasoline car, 16 Drive shaft, 17 Automatic transmission, 18 Differential gear, 19 Drive wheel, 20 Engine, 21 Air cleaner, 22 Throttle valve, 22a Throttle motor, 22b Throttle valve position sensor, 23 Injector, 23a Suction port, 24 Suction valve , 25 Spark plug, 26 Exhaust valve, 27 Crank angle sensor, 28 Pressure sensor, 29 Ignition coil, 31 Intake passage, 32 Combustion chamber, 33 Piston, 34, 35 Cam, 34a, 35a Cam shaft, 36 Cam angle sensor, 37 Crankshaft, 50 Electronic control unit for engine (engine ECU), 52 CPU, 54 ROM, 56 RAM, 81 Shift lever, 82 Shift position sensor , 83 an accelerator pedal, 84 an accelerator pedal position sensor, 85 brake pedal, 86 a brake pedal position sensor, 88 vehicle speed sensor.

Claims (8)

An air amount adjusting means for adjusting the amount of air supplied to each cylinder of the engine;
Fuel injection means for injecting fuel to each cylinder;
Fuel injection control means for controlling the fuel injection amount of the fuel injection means so as to be a predetermined air-fuel ratio, and for stopping the fuel injection of the fuel injection means to the engine when an engine stop request is made;
Pressure of the controls the air amount adjusting means so that the air amount after the engine stop request is made smaller, later the air quantity adjusting means is controlled so that the air quantity is reduced until the engine compression stroke The amount of air for controlling the air amount adjusting means so that the amount of air becomes larger when it falls below a predetermined lower limit value that is related so that the piston of the internal combustion engine stops in the stop section Adjustment control means;
An engine stop control device. When the air amount adjustment control unit controls the air amount adjustment unit so that the air amount becomes large, when the engine is stopped, the rotation speed of the engine is such that a predetermined cylinder stops in a predetermined stroke. And controlling the air amount adjusting means based on the amount of change in the engine speed.
The engine stop control device according to claim 1 . The air amount adjustment control unit controls the air amount adjustment unit so that the air amount becomes small after the fuel injection control unit stops the fuel injection of the fuel injection unit by idle stop control. wherein controlling the air quantity adjusting means so that the amount of air is increased when the pressure from the control so as to decrease after the air quantity adjusting means to said engine is below the predetermined lower limit value,
The engine stop control device according to claim 1 or 2 . The fuel injection control means causes the fuel injection means to inject fuel before the engine stops with respect to a cylinder that stops in a compression stroke when the engine stops.
The engine stop control device according to claim 3 . The engine stop control device according to claim 4 ,
Stop prediction means for predicting which cylinder stops in the compression stroke when the engine is stopped before the engine is stopped,
An engine stop control device. The air amount adjustment control means controls the air amount adjustment means so that the air amount decreases after the engine stop request, and the air amount is adjusted when the engine speed falls below a predetermined low speed. Controlling the air amount adjusting means so that
Engine stop control device according to any one of claims 1-5. The air amount adjusting means is a throttle valve.
Engine stop control device according to any one of claims 1-6. Vehicle equipped with an engine stop control device according to any one of claims 1-7.

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