JP2018087559A - Control method of compression self-ignition type engine and control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase of vibration irrespective of a variation of a resonance rotation number caused by an atmospheric temperature.SOLUTION: This control method of a compression self-ignition type engine includes: a rotation specification process for specifying an engine rotation number; an atmospheric temperature specification process for specifying an atmospheric temperature; a fuel supply amount setting process for setting a target supply amount of fuel which should be supplied to a cylinder from a fuel supply device on the basis of the engine rotation number which is specified by the rotation number specification process; and a threshold setting process for setting a threshold of the resonance band area in which vibration is liable to become large on the basis of the atmospheric temperature which is specified by the atmospheric temperature specification process. In the fuel supply amount setting process, the target supply amount when supplying the fuel in order to raise a rotation number from a state that the engine rotation number is lower than a lower limit rotation number of the resonance band area is set to a value by which the engine rotation number at the fuel supply in a succeeding cycle is deviated from the resonance band area, and in the threshold setting process, at least the lower limit rotation number of the resonance band area is shifted to a low-rotation side compared with the case that the atmospheric temperature is low when the atmospheric temperature is high.SELECTED DRAWING: Figure 5

Description

  The present invention includes a cylinder and a fuel supply device that supplies fuel to the cylinder, and a method for controlling an in-vehicle compression ignition engine that burns fuel supplied from the fuel supply device by self-ignition in the cylinder, and Relates to the device.

  In a vehicle equipped with an engine as described above, it is known that vibration increases when the engine speed reaches a specific rotation range. The main cause of this increase in vibration is considered to be that resonance occurs with the engine that is the excitation source in the power train including, for example, the engine and the transmission. In a general vehicle, the engine speed at which such resonance occurs (hereinafter referred to as “resonance speed”) is adjusted to be a value (for example, about 300 to 500 rpm) lower than the idle speed. This is to ensure the riding comfort of the vehicle by preventing resonance during normal operation of the engine.

  On the other hand, when the resonance rotational speed is set lower than the idle rotational speed as described above, there is a concern that the vibration of the power train increases when the engine is started. In other words, in the process where the engine speed increases to the idle speed due to cranking and combustion at the start of the engine, the vibration of the power train increases as the engine speed passes through the resonance speed and its vicinity (resonance band). There is a concern to do.

  It is known to take measures as described in Patent Document 1 below for such a problem. In this Patent Document 1, when a spark ignition engine is started, an ignition timing that is originally set to be considerably retarded for activation of the catalyst is set to a specific number in which the number of combustions from the start of the ignition is predetermined. The ignition timing is advanced to a timing close to the compression top dead center, and a sufficiently large torque is generated only when the number is the number of times (when the number of combustions is expected to occur at the number of revolutions included in the resonance band). I am doing so. As a result, the time spent in the resonance band is shortened, so that an increase in powertrain vibration can be suppressed.

JP2015-113774A

  Here, even if the ignition timing and the fuel supply amount are controlled as specified when the engine is started, the mode in which the rotational speed increases due to the difference in various conditions is not necessarily uniform, and the rotational speed is reduced to the idle rotational speed. There is a slight increase or decrease in the number of combustions required to raise. For this reason, even if the ignition timing is advanced only at the predetermined number of combustion times as in Patent Document 1, there is a possibility that the intended effect of passing through the resonance band in a short time may not be obtained. .

  Moreover, according to the knowledge of the inventor of the present application, the resonance rotational speed is not always constant and varies depending on the temperature condition. It is considered that this is mainly due to the fact that the elastic modulus of the mount member that supports the power train changes depending on the outside air temperature. In Patent Document 1, since the fluctuation of the resonance rotational speed due to such temperature conditions is not taken into consideration, there is a possibility that the intended effect cannot be obtained.

  The present invention has been made in view of the above circumstances, and a control method for a compression ignition engine capable of effectively suppressing an increase in vibration regardless of fluctuations in the resonance rotational speed due to outside air temperature, and An object is to provide a control device.

  In order to solve the above-described problems, the present invention includes a cylinder and a fuel supply device that supplies fuel to the cylinder, and the fuel supplied from the fuel supply device is burned by self-ignition in the cylinder. The method of controlling the compression ignition type engine of the present invention is based on the engine speed specified by the engine speed determined by the engine speed determined by the engine speed determined by the engine speed determined by the engine speed determined by the engine speed determined by the outside air temperature specified process. And a fuel supply amount setting step for setting a target supply amount of fuel to be supplied from the fuel supply device to the cylinder, and a resonance band in which vibration is likely to increase based on the outside air temperature specified by the outside air temperature specifying step. A threshold setting step for setting a threshold rotation number, and in the fuel supply amount setting step, in order to increase the rotation number from a state where the engine rotation number is lower than the lower limit rotation number of the resonance band The target supply amount when supplying the fuel is set to a value such that the engine speed at the time of fuel supply in the next cycle deviates from the resonance band, and in the threshold setting step, at least the lower limit rotation speed of the resonance band, When the outside air temperature is high, it is shifted to a low rotation side as compared with a low temperature (Claim 1).

  In addition, the present invention controls a vehicle-mounted compression ignition engine that includes a cylinder and a fuel supply device that supplies fuel to the cylinder, and burns the fuel supplied from the fuel supply device by self-ignition in the cylinder. A fuel supply device based on a crank angle sensor for detecting a change in the crank angle of the engine, an outside air temperature sensor for detecting an outside air temperature, and an engine speed specified by using the crank angle sensor. A fuel supply amount setting unit for setting a target supply amount of fuel to be supplied to the cylinder from the engine, and a threshold value for setting a threshold rotation speed of a resonance band in which vibration is likely to increase based on the outside air temperature detected by the outside air temperature sensor A setting unit, and the fuel supply amount setting unit is a target for supplying fuel to increase the engine speed from a state where the engine speed is lower than the lower limit engine speed of the resonance band. The supply amount is set to a value such that the engine speed at the time of fuel supply in the next cycle deviates from the resonance band, and the threshold setting unit sets at least the lower limit rotation speed of the resonance band when the outside air temperature is high. Is shifted to the low rotation side as compared with the low case (Claim 5).

  According to the present invention, the target supply amount when the fuel is supplied to the cylinder in a state where the engine speed is lower than the lower limit rotational speed of the resonance band where vibration is likely to be large is the engine speed when the fuel is supplied in the next cycle. Since the value is set so as to deviate from the resonance band, it is possible to avoid combustion within the resonance band, and effectively suppress the increase in vibration due to the torque generated by the combustion. be able to.

  In addition, when the outside air temperature is high, at least the lower limit rotational speed of the resonance band is shifted to the low speed side compared to the low speed, so the rotational speed (resonance rotation) of the powertrain including the engine and the transmission is generated. The number of engine revolutions at the time of fuel supply in the next cycle is adjusted by adjusting the target fuel supply amount based on the lower limit rotational speed of the resonance band that reflects the fluctuation. The resonance band can be removed with high probability. Thereby, the vibration of the power train can be effectively suppressed regardless of the fluctuation of the resonance rotational speed due to the outside air temperature.

  The resonance band is preferably set in a part of a region where the rotational speed is lower than the idle rotational speed. In this case, the fuel supply amount setting step in the control method is a step of setting a target fuel supply amount at start-up when the engine speed is lower than the idle speed (Claim 2), and the fuel supply in the control device The amount setting unit can set a target supply amount of fuel at start-up when the engine speed is lower than the idle speed (Claim 6).

  According to this configuration, it is possible to effectively suppress vibration at the start of the engine. In addition, since the resonance band is less than the idling speed, there is no fear that resonance of the power train occurs during normal operation of the engine, and the commercial value of the engine can be improved.

  In the control method, preferably, in the fuel supply amount setting step, the engine speed is increased from a state where the engine speed is lower than a predetermined engine speed set to a lower speed side than a lower limit engine speed of the resonance band. Therefore, the target supply amount when supplying fuel is set to a small value so that the engine speed at the time of fuel supply in the next cycle is less than the lower limit speed of the resonance band, and the engine speed is set to the predetermined speed. The target supply amount when fuel is supplied to increase the rotational speed from a state between the engine speed and the lower limit rotational speed of the resonance band, and the engine rotational speed at the time of fuel supply in the next cycle is the upper limit of the resonance band. The value is set to a large value exceeding the rotation speed, and in the threshold setting step, the predetermined rotation speed, the lower limit rotation speed and the upper limit rotation speed of the resonance band are respectively set to the outside air temperature. Is shifted to the low rotation side as compared with the case lower when higher (claim 3). In the control device, it is preferable that the fuel supply amount setting unit starts the engine speed from a state where the engine speed is lower than a predetermined speed set at a lower speed than the lower limit speed of the resonance band. The target supply amount at the time of supplying fuel for increasing is set to a small value such that the engine speed at the time of fuel supply in the next cycle is less than the lower limit speed of the resonance band, and the engine speed is The target supply amount when fuel is supplied in order to increase the rotation speed from a state between the predetermined rotation speed and the lower limit rotation speed of the resonance band, and the engine rotation speed when fuel is supplied in the next cycle is the resonance band. The threshold value setting unit sets the predetermined rotation number, the lower limit rotation number and the upper limit rotation number of the resonance band, and the outside air temperature, respectively. It is shifted to the low rotation side as compared with the case low when have (claim 7).

  According to this configuration, the target supply amount of fuel is increased or decreased depending on whether the engine speed is close to or far from the lower limit speed of the resonance band, and in any case, the engine speed at the time of fuel supply in the next cycle becomes the resonance band. Therefore, it is possible to prevent the torque generated by the combustion based on the fuel supply in the next cycle from causing a large vibration in the power train.

  In addition, a predetermined rotation speed that is a threshold for determining increase / decrease in the target supply amount, and a resonance band (its lower limit rotation speed and upper limit rotation speed) that is a range that should be avoided as the engine rotation speed at the time of fuel supply in the next cycle, When the outside air temperature is high, the engine is shifted to the low rotation side as compared with the low air temperature, so that the vibration of the power train can be effectively suppressed regardless of the fluctuation of the resonance rotational speed due to the outside air temperature.

  In the control method, preferably, in the fuel supply amount setting step, a target supply amount when fuel is supplied to increase the engine speed from a state where the engine speed is higher than the upper limit engine speed of the resonance band, When the difference between the upper limit engine speed and the engine speed is small, it is set to be smaller than when it is large. In the threshold setting step, the upper limit engine speed of the resonance band is set when the outside air temperature is high. Is shifted to the low rotation side as compared with the case of low (Claim 4). In the control device, preferably, the fuel supply amount setting unit supplies a target supply amount when fuel is supplied to increase the engine speed from a state where the engine speed is higher than the upper limit engine speed of the resonance band. Is set to be smaller when the difference between the upper limit engine speed and the engine speed is smaller than when the engine speed is large, and the threshold value setting unit sets the upper limit engine speed of the resonance band to the higher outside air temperature. In this case, the rotation is shifted to the low rotation side as compared with the low case (Claim 8).

  According to this configuration, it is possible to avoid generation of a large torque due to combustion in a state close to the upper limit rotational speed of the resonance band (that is, vibration is easily induced) regardless of the outside temperature, and the vibration increases by the torque. Can be suppressed.

  As described above, according to the control method and control device for a compression ignition engine of the present invention, it is possible to effectively suppress an increase in vibration regardless of fluctuations in the resonance rotational speed due to the outside air temperature.

It is a figure showing the whole diesel engine composition to which the control method or control device concerning one embodiment of the present invention was applied. It is a figure which shows the pulse signal input from a crank angle sensor on the change axis | shaft of a crank angle, and is a figure for demonstrating the method of calculating the rotation speed at the time of normal driving | operation of an engine. It is a flowchart which shows the specific procedure of control at the time of engine starting. FIG. 5 is a diagram corresponding to FIG. 4 for explaining a method of calculating the number of revolutions when starting the engine. It is a graph which shows the change of the fuel supply amount according to the engine speed at the time of starting, (a) shows the change pattern when outside temperature is low, (b) shows the change pattern when outside temperature is high, respectively. Yes. It is a graph which shows the relationship between the rotation speed difference with respect to the upper limit rotation speed of a resonance zone | band, and fuel supply amount.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing an overall configuration of a diesel engine to which a control method or control device according to an embodiment of the present invention is applied. The diesel engine shown in the figure is a four-cycle diesel engine mounted on a vehicle as a driving power source. The engine body 1 of this engine is of a so-called in-line 4-cylinder type, and includes a cylinder block 3 having four cylinders 2 arranged in a row in a direction orthogonal to the plane of the paper, and a cylinder so as to close each cylinder 2 from above. It has a cylinder head 4 provided on the upper surface of the block 3 and a piston 5 inserted in each cylinder 2 so as to be reciprocally slidable.

  A combustion chamber 6 is defined above the piston 5, and light oil as fuel is supplied to the combustion chamber 6 by injection from a fuel injection valve 15 described later. The injected fuel (light oil) is self-ignited (compression ignition) in the combustion chamber 6 where the temperature and pressure are increased by the compression action of the piston 5, and the piston 5 pushed down by the expansion force due to the combustion reciprocates vertically. It comes to exercise.

  Below the piston 5, a crankshaft 7 that is an output shaft of the engine body 1 is provided. The crankshaft 7 is connected to the piston 5 via a connecting rod (not shown), and is driven to rotate around the central axis according to the reciprocating motion (vertical motion) of the piston 5.

  Here, in a four-cycle four-cylinder diesel engine as shown in the figure, the piston 5 provided in each cylinder 2 moves up and down with a phase difference of 180 ° (180 ° CA) in crank angle. For this reason, the timing of combustion (fuel injection therefor) in each cylinder 2 is set to a timing shifted in phase by 180 ° CA. Specifically, if the cylinder numbers of the four cylinders 2 are number 1, 2, 3, 4 in order from the front of the page, the combustion is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder. Done. Therefore, for example, if the first cylinder is in the compression stroke, the third cylinder, the fourth cylinder, and the second cylinder are in the intake stroke, the exhaust stroke, and the expansion stroke, respectively.

  The cylinder head 4 is provided with an intake port 9 and an exhaust port 10 that open to the combustion chamber 6 of each cylinder 2, and an intake valve 11 and an exhaust valve 12 that open and close the ports 9 and 10. The intake valve 11 and the exhaust valve 12 are driven to open and close in conjunction with the rotation of the crankshaft 7 by valve mechanisms 13 and 14 including a pair of camshafts and the like disposed in the cylinder head 4.

  The cylinder head 4 is provided with one fuel injection valve 15 (corresponding to “fuel injection device” in the claims) for each cylinder 2. Each fuel injection valve 15 is connected to a fuel supply pipe 20 extending from a common rail (not shown) that stores fuel in a pressure accumulation state. Each fuel injection valve 15 receives fuel supplied from the fuel supply pipe 20 in a combustion chamber. A required amount of fuel is supplied to each cylinder 2 by high-pressure injection at 6.

  A water jacket (not shown) through which cooling water flows is provided inside the cylinder block 3 and the cylinder head 4, and a water temperature sensor SN1 for detecting the temperature of the cooling water (engine water temperature) in the water jacket is provided. The cylinder block 3 is provided.

  The cylinder block 3 is provided with a crank angle sensor SN2 for detecting the rotation angle of the crankshaft 7 (that is, the crank angle) and the rotation speed of the crankshaft 7 (that is, the engine speed). The crank angle sensor SN2 outputs a pulse signal according to the rotation of the crank plate 25 that rotates integrally with the crankshaft 7.

  Specifically, a large number of teeth 25 a arranged at a constant pitch project from the outer peripheral portion of the crank plate 25. The crank angle sensor SN2 is provided so as to face the teeth 25a of the crank plate 25, and detects the passage of each tooth 25a moving in the circumferential direction as the crank plate 25 rotates, thereby detecting a pulse signal ( ON / OFF signal) is output. The crank angle and the engine speed are detected based on the pulse signal from the crank angle sensor SN2.

  Although FIG. 1 is a schematic view and is not accurate, in the present embodiment, a large number of teeth 25a are provided on the outer peripheral portion of the crank plate 25 so as to be arranged at equal intervals every minute angle (for example, 6 ° CA). Yes. For this reason, the pulse signal output from the crank angle sensor SN2 is a signal having a constant cycle in which ON / OFF is repeated for each pitch angle of the teeth 25a. However, a specific angular range in the outer periphery of the crank plate 25 is a missing tooth portion 25b in which teeth are omitted. The chipped tooth portion 25b is provided as a reference for specifying the crank angle.

  The cylinder head 4 is provided with a cam angle sensor SN3 for detecting the angle of a cam shaft included in the valve mechanism (the valve mechanism 14 for the exhaust valve 12 here). The cam angle sensor SN3 generates a pulse signal for generating cylinder identification information (information for identifying which cylinder is in which stroke) according to the passage of the teeth of the signal plate that rotates integrally with the camshaft. Output.

  An intake passage 28 and an exhaust passage 29 are connected to the intake port 9 and the exhaust port 10, respectively. Intake air (fresh air) introduced into the combustion chamber 6 from the outside flows through the intake passage 28, and exhaust gas (combustion gas) discharged from the combustion chamber 6 to the outside flows through the exhaust passage 29.

  In the intake passage 28, the range from the engine body 1 to the upstream side by a predetermined distance is a branch passage portion 28a branched for each cylinder 2, and the upstream end of each branch passage portion 28a is connected to a common surge tank 28b. It is connected. A single tubular common passage portion 28c is provided on the upstream side of the surge tank 28b.

  An intake throttle valve 30 for adjusting the intake air amount to each cylinder 2 is provided in the common passage portion 28c. The intake throttle valve 30 is basically fully opened during operation of the engine or maintained at a high opening degree close thereto, and is closed only when necessary, such as when the engine is stopped, to block the intake passage 28.

  The cylinder block 3 is provided with a starter motor 34 for starting the engine. The starter motor 34 has a motor body 34a and a pinion gear 34b that is rotationally driven by the motor body 34a. The pinion gear 34b meshes with a ring gear 35 connected to one end of the crankshaft 7 so as to be detachable. When starting the engine using the starter motor 34, the pinion gear 34b moves to a predetermined meshing position and meshes with the ring gear 35, and the rotational force of the pinion gear 34b is transmitted to the ring gear 35. Thus, the crankshaft 7 is rotationally driven.

(2) Control system Each part of the engine configured as described above is centrally controlled by an ECU (engine control unit) 50. As is well known, the ECU 50 is a microprocessor including a CPU, a ROM, a RAM, and the like.

  Various information is input to the ECU 50 from various sensors provided in the engine. That is, the ECU 50 is electrically connected to the above-described water temperature sensor SN1, crank angle sensor SN2, and cam angle sensor SN3, and based on input signals from these sensors SN1 to SN3, the engine water temperature, crank angle, Various information such as engine speed and cylinder identification information is acquired.

  In addition, an outside air temperature sensor SN4 for detecting outside air temperature is provided in an engine room of a vehicle on which the engine is mounted. Furthermore, each part of the vehicle includes, for example, an in-vehicle sensor SN4 for detecting various types of information such as the vehicle traveling speed (vehicle speed), the accelerator pedal opening (accelerator opening), and the brake pedal ON / OFF (presence of braking). Is provided. The ECU 50 is electrically connected to the outside air temperature sensor SN4 and the in-vehicle sensor SN5, and based on the input signals from these sensors SN4 and SN5, various information related to the vehicle such as the vehicle speed, the accelerator opening degree, and the presence or absence of a brake, Get outside temperature.

  The ECU 50 controls each part of the engine while executing various calculations based on the information obtained from the sensors SN1 to SN5. The “fuel supply amount setting unit” and the “threshold setting unit” according to claims Is equivalent to. Specifically, the ECU 50 is electrically connected to the fuel injection valve 15, the intake throttle valve 30, the starter motor 34, and the like. Based on the result of the above calculation, the ECU 50 sends control signals to these devices. Output.

  More specific functions of the ECU 50 will be described. During the operation of the engine, the ECU 50 calculates the required torque (load) of the engine based on, for example, the vehicle speed and the accelerator opening detected by the in-vehicle sensor SN5, and changes in the crank angle detected by the crank angle sensor SN2. Based on the above, the engine speed is calculated. Further, a target supply amount of fuel to be supplied to each cylinder 2 is set based on various conditions such as the calculated required torque and engine speed, and an amount of fuel corresponding to the set target supply amount is set to each cylinder 2. The fuel injection valve 15 of each cylinder 2 is controlled so as to be supplied to the cylinder.

  Further, a so-called idling stop function is added to the engine of this embodiment. That is, the ECU 50 has a function of automatically stopping or restarting the engine under a predetermined specific condition. For example, the ECU 50 performs fuel injection when a plurality of conditions such as the vehicle speed is substantially zero, the accelerator pedal is OFF (accelerator opening is zero), and the brake pedal is ON are all satisfied. The fuel supply from the valve 15 is cut and the engine is automatically stopped. On the other hand, after the engine is automatically stopped, at least one of a plurality of conditions such as the accelerator pedal being switched from OFF to ON (accelerator opening is greater than zero) and the brake pedal being switched from ON to OFF. When one of the conditions is satisfied, the engine is restarted by restarting the fuel supply from the fuel injection valve 15 or the like.

(3) Control during normal operation Next, a specific example of control applied during normal operation of the engine, that is, during operation after engine start (forced start with ignition ON or restart after automatic stop) is completed. An example, in particular, a method for calculating the engine speed and a method for setting the target supply amount of fuel will be described.

  FIG. 2 is a diagram illustrating a pulse signal input from the crank angle sensor SN2 to the ECU 20 on the change axis of the crank angle. FIG. 2 also shows a change in stroke of the cylinder 2 for injecting fuel. The compression top dead center of the cylinder 2 is 360 ° CA, the intake bottom dead center is 180 ° CA, and the exhaust top dead center is 0 ° CA.

  During normal operation of the engine, the ECU 50 starts processing for setting a target supply amount of fuel to be supplied to the cylinder 2 at a predetermined crank angle C6 during the compression stroke. Specifically, when it is confirmed that the crank angle has become C6 based on the detected value of the crank angle sensor SN2, the engine speed is calculated based on the time change of the crank angle before C6 (details thereof). The method will be described later). Then, based on the calculated engine speed, the required engine torque (load) calculated from the vehicle speed and accelerator opening detected by the in-vehicle sensor SN5, and the engine water temperature detected by the water temperature sensor SN1, the fuel An amount of fuel to be injected from the injection valve 15, that is, a target supply amount of fuel is set.

  In the example of FIG. 2, the pilot injection F0 is executed in the middle of the compression stroke of each cylinder 2, and the main injection F1 is executed in the latter half of the compression stroke. As a result, the total injection amount by the pilot injection F0 and the main injection F1 is set based on the engine speed, the required torque, and the engine water temperature.

  The timing of the pilot injection F0 is set to a timing slightly deviated from the crank angle C6 at which the process for setting the target supply amount of fuel is started. In other words, a period corresponding to a certain crank angle difference exists between the time point of the crank angle C6 and the time point of the pilot injection F0, and at least the engine speed and the target supply amount of fuel are included in the period. It is set to be a period required for the specified calculation or longer.

  Here, the timing at which the pilot injection F0 and the main injection F1 are executed is not limited to the timing as shown in FIG. 2, and may vary according to the engine speed, the required torque, the engine water temperature, and the like. Further, the injection pattern from the fuel injection valve 15 is not limited to the pattern in which the pilot injection and the main injection are performed twice, and a pattern in which the injection is performed three times or more may be employed, or only once. In some cases, a pattern of jetting is used. The ECU 50 performs a process for setting the fuel injection pattern and the injection timing in addition to the process for setting the target fuel supply amount described above. However, in order to perform these settings based on the engine speed at the time of the crank angle C6, the timing of the first fuel injection is set to the retard side of the crank angle C6 in any injection pattern. It is like that.

  Expression (1) shown in FIG. 2 is an arithmetic expression for calculating the engine speed N at the time of the crank angle C6. As shown in this equation (1), the engine speed N (rpm) at the time of the crank angle C6 is measured for each elapsed time in a plurality of divided sections (D1 to D6) set before the crank angle C6. It is calculated based on the values (Δt1 to Δt6).

  Specifically, in this embodiment, a crank angle range (for example, a range of 180 ° CA) from a predetermined crank angle C0 during the intake stroke to the crank angle C6 during the compression stroke is divided into six, Six divided sections from the first divided section D1 to the sixth divided section D6 are set (C1 to C5 are crank angles at the boundaries of the divided sections). The ECU 50 determines the time from the start to the end of each of the first to sixth divided sections D1 to D6, that is, the elapsed time Δt1 to Δt6 of each divided section D1 to D6, based on the count value of the timer built in itself. measure. Then, the ECU 50 calculates the engine speed N by the equation (1) based on these data.

  In Expression (1), the term A surrounded by a chain line, that is, the difference between the crank angle C6 and the crank angle C0 (C6-C0) is the sum of the time measurement values of each of the divided sections D1 to D6 (Δt1 + Δt2... + Δt6). The value divided by represents the average angular velocity during the period in which the crank angle changes from C0 to C6, in other words, the average value of the angular velocities of the divided sections D1 to D6. Since the engine speed N (rpm) is the number of rotations of the crankshaft 7 per minute, the engine speed is obtained by multiplying this average angular velocity (A term) by 60 (s) / 360 (° CA). N (rpm) can be calculated.

  As described above, during normal operation of the engine, the average angular velocities of the divided sections D1 to D6 are calculated using the time measurement values Δt1 to Δt6 of the plurality of (here, six) divided sections D1 to D6, and The engine speed is calculated based on the average angular velocity.

  Here, in the example of FIG. 2, the pulse signal in the sixth divided section D6 is always OFF. This sixth divided section D6 corresponds to the missing tooth portion 25b of the crank plate 25 shown in FIG. This is because it is a section. That is, while the missing tooth portion 25b passes in front of the crank angle sensor SN2, the ON signal associated with the passage of the tooth 25a is not output from the crank angle sensor SN2, so the pulse signal is always OFF. The sixth divided section D6 is a no-signal section corresponding to the period from the start to the end of the missing tooth portion 25b.

  In the in-line four-cylinder engine as in the present embodiment, the phase difference between the cylinders 2 is 180 ° CA. Therefore, as shown in FIG. 2, the sixth divided section D6 corresponds to the non-signal section (corresponding to the missing tooth portion 25b). ) Is only two of the four cylinders, and in the other two cylinders, the sixth divided section D6 is not a no-signal section. For example, if the sixth divided section is a no-signal section in the first cylinder and the fourth cylinder, the sixth divided section D6 is not a no-signal section in the second and third cylinders. However, even if the sixth divided section D6 is a no-signal section, since the start and end of the section can be specified by switching ON / OFF, the elapsed time Δt6 of the sixth divided section D6 can be measured. That is, in specifying the engine speed and the target supply amount of fuel, whether or not the sixth divided section D6 is a no-signal section is not particularly affected. In other words, the method for specifying the engine speed and the target fuel supply amount is the same for any of the first to fourth cylinders.

(4) Control at the time of engine start Next, the contents of control executed by the ECU 50 at the time of engine start will be described. Here, the “start” of the engine includes not only the forced start of the engine when the ignition is turned on, but also the restart of the engine that has been automatically stopped (idling stop), that is, the automatic start of the engine. The control at the time of forced engine start will be described as an example. In the automatic engine start, the cylinder identification information is known, so unlike the forced start, the control in step S3 described later is unnecessary, but the remaining control is substantially the same.

  FIG. 3 is a flowchart showing a specific procedure for control during forced start of the engine. When the ignition is turned on and the control shown in this flowchart is started, the ECU 50 starts cranking for driving the starter motor 34 to forcibly rotate the crankshaft 7 (step S1).

  Further, together with the start of cranking, the ECU 50 sets engine speed threshold values X1, X2, and X3 shown in FIG. 5 based on the outside air temperature detected by the outside air temperature sensor SN4 (step S2). Hereinafter, when X1 is the first rotation speed, X2 is the second rotation speed, and X3 is the third rotation speed, the third rotation speed X3 is lower than the idle rotation speed Y, and the second rotation speed X2 is the third rotation speed X3. The first rotation number X1 is set to be lower than the second rotation point number X2. As is well known, the idle speed Y is the engine speed set when the accelerator pedal is OFF (accelerator opening is zero) and the vehicle is stopped after the start of the engine is completed. .

  The range from the second rotational speed X2 to the third rotational speed X3 is a rotational range in which the vibration of the power train including the engine and the transmission is likely to be large. In other words, the second rotational speed X2 is the lower limit rotational speed of the resonance band R, and the third rotational speed X3 is the upper limit rotational speed of the resonance band R. The resonance band R is set so as to include the rotation speed (resonance rotation speed) corresponding to the resonance frequency of the power train.

  That is, in the power train including the engine and the transmission, when the frequency of vibration of the engine body 1 that is the excitation source reaches a certain frequency, the entire power train vibrates greatly due to resonance. If the rotational speed corresponding to the frequency at which such resonance occurs, that is, the resonant rotational speed is equal to or higher than the idle rotational speed Y, resonance of the power train occurs during normal operation of the engine, and the ride comfort of the vehicle deteriorates. . Therefore, in general, the arrangement and material characteristics (elastic coefficient, etc.) of the mount member that mounts the power train on the vehicle body are adjusted so that the resonance rotational speed is lower than the idle rotational speed. Also in this embodiment, the mount member and the like are set so that the resonance rotational speed is lower than the idle rotational speed Y, as in such a general vehicle. A predetermined range including the rotation speed close to the resonance rotation speed, that is, a range from the second rotation speed X2 slightly lower than the resonance rotation speed to the third rotation speed X3 slightly higher than the resonance rotation speed, the vibration of the power train is large. It is set as a resonance band R that is likely to occur. In the case of the present embodiment, the resonance band R is set at a substantially middle portion of the region below the idle rotation speed Y, and the first rotation speed X1 is set on the lower rotation side of the resonance band R. . The first rotational speed X1 corresponds to the “predetermined rotational speed” in the claims.

  Here, the resonance frequency of the powertrain varies somewhat depending on the outside air temperature. This corresponds to the change in the elastic modulus of the mount member due to the difference in the outside air temperature. As a result, the rotational speed at which resonance occurs, that is, the resonant rotational speed is shifted to the low rotational speed side or the high rotational speed side due to the temperature change, and accordingly, it is desirable to shift the resonance band R to the low rotational speed side or the high rotational speed accordingly. It is. Therefore, the ECU 50 variably sets the lower limit rotation speed and the upper limit rotation speed of the resonance band R, that is, the second rotation speed X2 and the third rotation speed X3, based on the outside air temperature detected by the outside air temperature sensor SN4. More specifically, since it is known that the resonance rotational speed shifts to a lower rotational speed as the outside air temperature becomes higher, the lower limit rotational speed and the upper limit rotational speed of the resonance band R (second rotational speed X2 and third rotational speed X3). However, the higher the outside air temperature, the lower the rotation speed is set. Similarly, the first rotation speed X1 is also set so as to shift to the low rotation side as the outside air temperature increases so as to interlock with the resonance band R.

  After setting the respective threshold values (X1, X2, X3) relating to the rotational speed as described above, the ECU 50 completes reading of the cylinder identification information based on the input signals from the crank angle sensor SN2 and the cam angle sensor SN3. It is determined whether or not (step S3). This reading is completed at least while the crankshaft 7 is rotated twice (in other words, the camshaft is rotated once) by cranking.

  When it is determined YES in step S3 and it is confirmed that reading of the cylinder identification information is completed, the ECU 50 supplies the first fuel to the cylinder 2 in the compression stroke at that time in order to supply the first fuel to the fuel injection valve 15 of the cylinder 2. The fuel is injected from (Step S4). The amount of fuel supplied by the first fuel injection is determined in advance so as to be an appropriate amount that does not cause misfire and does not generate excessive combustion torque. Note that when the engine water temperature is low (in other words, the wall surface temperature of the combustion chamber 6 is low), the ratio of the fuel to be vaporized in the injected fuel is reduced. Therefore, the amount of fuel supplied can be set within an appropriate range according to the engine water temperature. The increase / decrease correction may be performed.

  After the first combustion based on the fuel injection is performed, the ECU 50 determines whether the crank angle of the cylinder that reaches the compression stroke next to the cylinder in which the first combustion is performed has reached C6 shown in FIG. Is determined based on an input signal from the crank angle sensor SN2 (step S5). The crank angle C6 shown in FIG. 4 represents the crank angle at which the fuel injection amount setting process is started, as in the case of the control during the normal operation already shown in FIG. 2 and 4, the crank angle at which the fuel injection amount setting process is started is C6. However, the crank angle C6 in FIG. 2 (normal operation) and the crank angle in FIG. C6 need not be the same and may be different. The same applies to the crank angle C5 described later.

  When it is determined YES in step S5 and it is confirmed that the crank angle has reached C6, the ECU 50 calculates the engine speed N based on the input signal from the crank angle sensor SN2 (step S6).

  Specifically, the ECU 50 calculates the engine speed N using the equation (2) shown in FIG. As shown in this equation (2), the engine speed N (rpm) at the time of the crank angle C6 is the passage of the sixth divided section D6 set between the crank angle C6 and the crank angle C5 slightly before it. It is calculated based on the measured time value Δt6. That is, the ECU 50 divides the difference (C6-C5) between the crank angles C6 and C5 by the time measurement value Δt6 from the start to the end of the sixth divided section D6, thereby obtaining an angular velocity (formula ( 2) of B) is obtained, and the engine speed N (rpm) is calculated by multiplying the angular velocity by 60 (s) / 360 (° CA).

  As described above, when the engine is started, the angular velocity of the divided section D6 is calculated using the time measurement value Δt6 of the sixth divided section D6 which is the divided section immediately before the crank angle C6, and this single divided section is used. The engine speed N is calculated based only on the angular velocity of the section D6. In other words, when the engine is started, the time measurement values Δt1 to Δt6 of the first to sixth divided sections D1 to D6 that should be considered if the engine is in normal operation (FIG. 2), 5 of the past. The engine speed is calculated using only the most recent time measurement value (Δt6) of one divided section, ignoring the time measurement values (Δt1 to Δt5) of the two divided sections.

  When the engine speed N at the time of the crank angle C6 is calculated as described above, the ECU 50 determines whether the calculated engine speed N is equal to or higher than the first speed X1 set in step S2. It is determined whether or not (step S7).

  If it is determined NO in step S7 and it is confirmed that the engine speed N at the time of the crank angle C6 is less than the first speed X1 (N <X1), the ECU 50 performs the compression stroke at this time. The target supply amount of fuel to be supplied to a certain cylinder 2, that is, the amount of fuel to be injected from the fuel injection valve 15 of the cylinder 2 is set to a predetermined first supply amount (step S8). This first supply amount is such that the engine speed at the time when fuel is injected into the cylinder that will reach the next compression stroke is less than the second speed X2 (the lower limit speed of the resonance band R) set in step S2. Is set to a relatively small amount.

  That is, when a large amount of fuel is injected into a cylinder that is currently in the compression stroke whose engine speed is less than the first speed X1, the engine speed increases by a relatively large amount due to the torque generated by the combustion of the injected fuel. Then, when the fuel is injected into the cylinder that will reach the next compression stroke, that is, the engine speed at the time of fuel injection in the next cycle, which is performed after a lapse of about 180 ° CA from now, the second rotational speed X2 is likely to exceed halfway. It will be a bad value. In this case, combustion due to combustion injection in the next cycle occurs in the resonance band R (between the second rotation speed X2 and the third rotation speed X3) where the vibration of the power train is likely to increase, and accompanying the combustion The generated torque is thought to cause a large vibration in the powertrain. Therefore, in order to avoid such a situation, in step S7 described above, the target supply amount of fuel is a small amount set in advance so that the engine speed at the time of fuel injection in the next cycle is as low as possible below the second speed X2. The first supply amount is set.

  On the other hand, when it is determined YES in step S7 and it is confirmed that the engine speed N at the crank angle C6 is equal to or higher than the first speed X1 (N ≧ X1), the ECU 50 It is determined whether N is less than the second rotation speed X2 that is the lower limit rotation speed of the resonance band R (step S9).

  When it is determined YES in step S9 and it is confirmed that the engine speed at the time of the crank angle C6 is equal to or greater than the first speed X1 and less than the second speed X2 (X1 ≦ N <X2), the ECU 50 Sets the target supply amount of the fuel to the maximum supply amount that is the largest value in the range of the fuel supply amount that can be set when the engine is started (step S10).

  In other words, the amount of fuel that can be supplied to the cylinder 2 when the engine is started is that excess fuel that cannot react with air is excessive from the minimum supply amount that is the lower limit supply amount necessary for igniting the fuel (not causing misfire). It is necessary to set one of the ranges up to the maximum supply amount that is the upper limit supply amount determined so as not to increase. In step S10, the maximum supply amount that is the upper limit of the range is set as the target supply amount of fuel. Here, the minimum supply amount and the maximum supply amount of fuel differ according to the engine water temperature (in other words, the wall surface temperature of the combustion chamber 6). For example, since the fuel vaporization rate decreases as the engine water temperature decreases, the minimum supply amount and the maximum supply amount increase as the engine water temperature decreases. The ECU 50 stores in advance the minimum supply amount and the maximum supply amount that change according to the engine water temperature in this way, and the maximum supply amount that conforms to the current engine water temperature (the temperature detected by the water temperature sensor SN1) from among them. Is set as the target supply amount of fuel. Note that the target supply amount of fuel is set to the maximum supply amount because a large amount of fuel is burned to generate a large torque, and the engine speed at the time of fuel injection in the next cycle is set to a speed exceeding the resonance band R. This is to raise it at once.

  On the other hand, when it is determined NO in step S9 and it is confirmed that the engine speed N at the time of the crank angle C6 is greater than or equal to the second speed X2 (N ≧ X2), the ECU 50 It is determined whether N is greater than the third rotation speed X3 set in step S2 as the upper limit rotation speed of the resonance band R (step S11).

  If it is determined YES in step S11 and it is confirmed that the engine speed N at the crank angle C6 is greater than the third speed X3 (N> X3), the ECU 50 determines the target fuel supply amount. The second supply amount, which is a value that changes according to the difference from the third rotation speed X3, is set (step S12).

  FIG. 6 shows a difference obtained by subtracting the third rotational speed X3 that is the upper limit rotational speed of the resonance band R from the engine rotational speed N at the current time (at the time of the crank angle C6) (hereinafter simply referred to as the rotational speed difference), It is the graph which showed the relationship with the target supply amount of the fuel set by step S12. As shown in the figure, the target supply amount of fuel is proportionally larger as the rotational speed difference is larger in the range where the rotational speed difference is less than the threshold value Z (in other words, the smaller the rotational speed difference is, the more proportional the fuel supply is. To be smaller). If the target supply amount when the rotational speed difference matches the threshold value Z is W, the target supply amount when the rotational speed difference exceeds the threshold value Z is a constant value (W ) Is maintained.

  On the other hand, if NO is determined in step S11 and the engine speed N at the time of the crank angle C6 is not less than the second speed X2 and not more than the third speed X3 (X2 ≦ N ≦ X3), that is, the resonance band When it is confirmed that the rotational speed is included in R, the ECU 50 proceeds to step S10 and sets the target supply amount of fuel to the maximum supply amount.

  When the target supply amount of fuel is set in any of the above steps S8, S10, S12, the ECU 50 causes the fuel injection valve 15 of the cylinder in the compression stroke to supply an amount of fuel that matches the set target supply amount. Inject (step S13). Here, in this embodiment, as shown in FIG. 4, a pattern for performing two injections of pilot injection F0 and main injection F1 is selected when the engine is started. Therefore, in step S13, the fuel injection valve 15 is controlled so that the sum of the injection amounts of the pilot injection F0 and the main injection F1 matches the target supply amount. The injection amounts of pilot injection F0 and main injection F1 can be determined based on a predetermined division ratio and the target injection amount.

  When the fuel injected in step S13 burns, the ECU 50 performs the above step when the cylinder that reaches the compression stroke next to the cylinder in which the combustion is performed reaches the crank angle C6 (FIG. 4) during the compression stroke. The engine speed N is calculated by the same procedure as S6 (step S14), and it is determined whether or not the calculated speed N is equal to or higher than a predetermined idle speed Y (step S15). If NO is determined in step S15 and it is confirmed that the engine start is not completed (N <Y), the process returns to step S7, and YES is determined and the engine start is completed (N ≧ Y). ) Is confirmed, this flow is terminated and the control shifts to the normal operation.

  Two graphs (a) and (b) in FIG. 5 show specific examples of the change pattern of the fuel supply amount at the time of engine start set by the control as described above. The broken line waveform in graph (a) shows the change pattern of the fuel supply amount when the outside air temperature is low, and the broken line waveform in graph (b) shows the change in fuel supply amount when the outside air temperature is high. The pattern is shown. In addition, the black circles or white circles in the respective waveforms represent the fuel injections in the nth cycle (n = 1, 2,...) When the first fuel injection after the start of the start is the first fuel injection. From the left, the fuel injection is in the first cycle, the second cycle, the third cycle, and so on. That is, the position of the horizontal axis of each point represents the engine speed when the fuel injection of the nth cycle is performed, and the position of the vertical axis of each point represents the injection amount by the fuel injection of the nth cycle.

  In the graph of FIG. 5A corresponding to the start at a low temperature condition, the first pattern indicated by a solid line indicates the engine speed at the time of fuel injection in the second cycle after the start of the start, more specifically in the second cycle. This is a change pattern of the fuel supply amount when the engine speed at the crank angle C6 immediately before fuel injection is lower than the first speed X1, and the second pattern indicated by the alternate long and short dash line is the second cycle It is a change pattern of the fuel supply amount when the engine speed at the time of fuel injection is higher than the first speed X1.

  In the first pattern (solid line waveform) shown in FIG. 5A, the engine speed (point P2) at the time of fuel injection in the second cycle is lower than the first speed X1. For this reason, in the fuel injection in the second cycle, a relatively small amount of fuel corresponding to the first supply amount (step S8) described above is injected. As a result, the range of increase in the engine speed is suppressed, and the engine speed (point P3) at the next (third cycle) fuel injection is higher than the second speed X2 that is the lower limit speed of the resonance band R. The value is kept low. On the other hand, in the fuel injection in the third cycle, a large amount of fuel corresponding to the above-described maximum supply amount (step S10) is injected. As a result, the engine speed (point P4) at the next (fourth cycle) fuel injection increases to a value higher than the third speed X3, which is the upper limit speed of the resonance band R.

  On the other hand, in the second pattern (the dashed line waveform), the engine speed (point P2 ') at the time of fuel injection in the second cycle is higher than the first speed X1. For this reason, in the fuel injection in the second cycle, a large amount of fuel corresponding to the above-described maximum supply amount (step S10) is injected. As a result, the engine speed (point P3 ') at the time of the next (third cycle) fuel injection is increased to a value higher than the third speed X3 that is the upper limit speed of the resonance band R. That is, in the second pattern, the number of times of combustion required to exceed the resonance band R is reduced by one as compared with the first pattern described above.

  Further, the fuel injection amount after exceeding the resonance band R is also different between the first pattern and the second pattern. That is, in the first pattern, the engine speed (point P4) at the time of fuel injection in the fourth cycle immediately after exceeding the resonance band R is somewhat larger than the third speed X3. On the other hand, in the second pattern, the engine speed (point P3 ′) at the time of fuel injection in the third cycle immediately after exceeding the resonance band R is larger than the third speed X3. It is small compared. For this reason, the fuel injection amount immediately after exceeding the resonance band R is set to be smaller in the second pattern than in the first pattern. The broken line L shown in the graph of FIG. 5A is a limit line for changing the fuel injection amount after exceeding the resonance band R, and the setting of the injection amount is limited below the line L. Represents that

  Compared with the start under the low temperature condition as described above (FIG. 5A), the upper limit rotation speed and the lower limit rotation speed of the resonance band R (when the start under the high temperature condition shown in FIG. 2nd rotation speed X2 and 3rd rotation speed X3) and 1st rotation speed X1 are each shifted to the low rotation side compared with the time of low temperature conditions (representing each rotation speed before shift with a broken line) ) For this reason, under a high temperature condition, a pattern with a small number of times of combustion required to exceed the resonance band R is easily obtained as in the second pattern shown in FIG. That is, as shown in FIG. 5B, there is a higher probability that the engine speed (point P2 ″) at the time of fuel injection in the second cycle will be higher than the first speed X1 after the shift. If it becomes higher than X1, a large amount of fuel corresponding to the above-mentioned maximum supply amount (step S10) is injected in the fuel injection of the second cycle, so the engine speed at the time of the next (third cycle) fuel injection (Point P3 ″) increases to a value higher than the third rotational speed X3, which is the upper limit rotational speed of the resonance band R after the shift.

(5) Operation, etc. As described above, in the present embodiment, the engine speed is lower than the resonance band R, which is the rotation range in which the vibration of the powertrain (engine, transmission, etc.) tends to increase during engine startup. The target supply amount when supplying fuel to the cylinder 2 in the state is set to a value such that the engine speed at the time of fuel supply in the next cycle deviates from the resonance band R, and the resonance band R is higher as the outside air temperature is higher. Since it is variably set so as to shift to the low rotation side, even if the resonance rotational speed at which the resonance of the power train occurs varies depending on the outside air temperature, combustion within the resonance band R is avoided with a high probability. There is an advantage that vibration at the time of engine start can be effectively suppressed.

  More specifically, in the above embodiment, the engine speed at the time of the crank angle C6 that is the crank angle immediately before fuel injection is lower than the second speed X2 that is the lower limit speed of the resonance band R. When the number of revolutions is less than X1, the target fuel supply amount is set to a relatively small value (first supply amount) so that the engine revolution number at the time of fuel supply in the next cycle is less than the second revolution number X2. Is done. On the other hand, when the engine speed at the time of the crank angle C6 is equal to or higher than the first speed X1 and lower than the second speed X2, the engine speed at the time of fuel supply in the next cycle is the upper limit speed of the resonance band R. The target supply amount of fuel is set to a sufficiently large value (maximum supply amount) so as to exceed the third rotation speed X3.

  Thus, in the above embodiment, the target fuel supply amount is equal to or less than the lower limit rotational speed (second rotational speed X2) of the resonance band R when the engine rotational speed at the crank angle C6 is close. Since the engine speed at the time of fuel supply in the next cycle is set to a value that deviates from the resonance band R, it is possible to prevent torque generated by combustion based on fuel supply in the next cycle from causing large vibrations in the powertrain. Can do.

  In addition, as described above, the first rotational speed X, which is a threshold for determining the increase or decrease in the target supply amount of fuel, and the resonance band R (the lower limit and the range that is desired to be avoided as the engine rotational speed at the time of fuel supply in the next cycle). The upper rotational speed X2, X3) is shifted to the lower rotational speed as the outside air temperature is higher, so even if the rotational speed at which the powertrain resonance (resonant rotational speed) fluctuates due to the influence of the outside air temperature, By adjusting the target fuel supply amount based on the position of the resonance band R reflecting the fluctuation, the engine speed at the time of fuel supply in the next cycle can be removed from the resonance band R with high probability. Thereby, it is possible to effectively suppress the vibration at the time of starting the engine regardless of the fluctuation of the resonance rotational speed due to the outside air temperature.

  In the above embodiment, the target supply amount when the fuel is supplied in a state where the engine speed is higher than the third rotation speed X3 that is the upper limit rotation speed of the resonance band R is the third rotation speed X3 and the engine rotation speed. Therefore, it is possible to avoid the generation of a large torque due to combustion in a state close to the resonance band R (that is, vibration is easily induced) regardless of the outside temperature. It is possible to suppress an increase in vibration due to the torque.

  Moreover, in the said embodiment, six time obtained by measuring the elapsed time of the division | segmentation area D1-D6 which divided | segmented the predetermined crank angle range into six at the time of normal driving | running whose engine speed is more than idle speed Y. While the engine speed is calculated based on the measured values Δt1 to Δt6 (see FIG. 2), at the time of start-up when the engine speed is less than the idle speed Y, one of the divided sections D1 to D6 is divided. Since the engine speed is calculated based only on the time measurement value Δt6 of the section D6 (see FIG. 4), the engine speed can be accurately calculated, and the target fuel supply amount is calculated based on the calculated engine speed. There is an advantage that can be set appropriately.

  That is, when the engine is started, the engine speed is lower and the fluctuation is more severe than that during normal operation. For this reason, the elapsed time from the start to the end of a certain crank angle range (for example, the range of 180 ° CA) is longer at the start than at the normal operation, and the crank time is increased by the time. The fluctuation amount of the angular velocity of the crankshaft 7 that fluctuates from the start to the end of the angular range is also larger at the start than at the normal time. Therefore, when the engine speed is calculated in the same manner as during normal operation using all the time measurement values Δt1 to Δt6 of the six divided sections D1 to D6 at the time of starting the engine, a crank over a relatively long time The time change of the angle is averaged, and it becomes difficult to accurately reflect the actual engine speed, which may have fluctuated in the meantime, in the calculated value.

  On the other hand, in the above-described embodiment, the engine speed is determined using only the time measurement values Δt6 of one divided section D6, instead of using all the time measurement values Δt1 to Δt6 of the six divided sections D1 to D6. Since it is calculated, even if it is the engine speed at the time of starting with a low value and a large fluctuation, it can be calculated relatively accurately.

  In the above embodiment, when the engine is started, the target supply amount of fuel to be supplied to the cylinder 2 is set based on the relatively accurate engine speed calculated as described above. An appropriate target supply amount corresponding to the rotation speed close to the rotation speed can be set. That is, by supplying fuel to the cylinder 2 in accordance with the set target supply amount, the engine speed at the start can be increased in a targeted manner, and the engine speed at each fuel supply is within the resonance band R. Entering can be avoided with a higher probability.

  In the above-described embodiment, the outside air temperature is directly detected by the outside air temperature sensor SN4 provided in the engine room. However, some state quantity (for example, intake air temperature) that changes in conjunction with the outside air temperature is detected and detected. The outside air temperature may be estimated based on the value.

  In the above embodiment, the target supply amount of fuel is set based on the engine speed calculated at the crank angle C6, which is the crank angle immediately before fuel is injected from the fuel injection valve 15 into the cylinder 2. However, the engine speed immediately before the injection may be estimated from the engine speed calculated somewhat before the fuel injection, and the target supply amount of fuel may be set based on the estimated engine speed.

  Further, in the above embodiment, the upper limit rotation speed and the lower limit rotation speed (that is, the second rotation speed X2 and the third rotation speed X3) of the resonance band R and the first rotation speed X1 are reduced as the outside air temperature increases. However, the rotational speeds X1, X2, and X3 may be changed stepwise with at least one outside air temperature threshold as a boundary. Further, the object to be changed according to the outside air temperature may be at least the lower limit rotational speed (second rotational speed X2) of the resonance band R, and the other two threshold values (first rotational speed X1 and third rotational speed) are It may be a fixed value.

  Further, in the above-described embodiment, the target fuel supply amount is within a range where the difference (rotational speed difference) between the upper limit rotational speed (third rotational speed X3) of the resonance band R and the engine rotational speed is equal to or less than the threshold value Z shown in FIG. However, the target supply amount may be changed stepwise according to the rotation speed difference.

  Further, in the above-described embodiment, a small amount of fuel injection (step S4) performed as the first fuel injection after the start of the engine start, and at least one injection amount in which the injection amount is adjusted according to the subsequent increase in the engine speed. Through the fuel injection (steps S8 and S10), the engine speed is increased to a higher rotation side than the resonance band R in which vibration is likely to increase (see FIG. 5). Step S4) is not essential. For example, when the resonance band R is shifted to a lower rotation side than the example of FIG. 5, the engine speed when the first fuel injection is performed (the engine speed reached only by cranking) is the first speed. It will rise to the vicinity of X1. In this case, the first small amount of fuel injection (step S4) is not necessary, and it is possible to suddenly execute fuel injection (step S8 or S10) according to the engine speed.

  In the above-described embodiment, an example in which the control method or the control device of the present invention is applied to a diesel engine that compresses and ignites light oil has been described. However, the engine to which the present invention can be applied is not limited to a diesel engine. The present invention can also be suitably applied to a so-called HCCI gasoline engine that is pre-mixed with and then subjected to compression ignition. That is, it can be said that the diesel engine or the HCCI gasoline engine has a higher compression ratio than that of a normal spark ignition type gasoline engine, and vibration at the time of starting tends to increase. For this reason, the present invention capable of more precisely controlling the fuel supply at the time of starting the engine is suitable for these compression ignition engines.

2 cylinder 15 fuel injection valve (fuel supply device)
50 ECU (fuel supply amount setting unit, threshold setting unit)
SN2 Crank angle sensor R Resonance band X1 First rotation speed (predetermined rotation speed)
X2 Second rotation speed (lower limit rotation speed of resonance band)
X3 3rd rotation speed (upper limit rotation speed of resonance band)

Claims (8)

A method for controlling an in-vehicle compression ignition engine comprising a cylinder and a fuel supply device for supplying fuel to the cylinder, and burning the fuel supplied from the fuel supply device by self-ignition in the cylinder,
A rotational speed identification step for identifying the engine rotational speed;
An outside air temperature identifying step for identifying the outside air temperature,
A fuel supply amount setting step of setting a target supply amount of fuel to be supplied from the fuel supply device to the cylinder based on the engine rotation speed specified in the rotation speed specifying step;
A threshold setting step for setting a threshold rotational speed of a resonance band based on the outside air temperature specified by the outside air temperature specifying step, and vibration is likely to increase.
In the fuel supply amount setting step, the target supply amount for supplying fuel to increase the rotational speed from a state where the engine rotational speed is lower than the lower limit rotational speed of the resonance band is set to the engine at the time of fuel supply in the next cycle. Set the value so that the rotational speed is out of the resonance band,
In the threshold value setting step, at least the lower limit rotational speed of the resonance band is shifted to a lower rotational speed side when the outside air temperature is high than when it is low. In the control method of the compression ignition type engine according to claim 1,
The resonance band is set in a part of a region where the rotational speed is lower than the idle rotational speed,
The control method for a compression ignition engine, wherein the fuel supply amount setting step is a step of setting a target fuel supply amount at start-up when the engine speed is lower than the idle speed. In the control method of the compression ignition type engine according to claim 1 or 2,
In the fuel supply amount setting step, when fuel is supplied to increase the rotational speed from a state where the engine rotational speed is lower than the predetermined rotational speed set lower than the lower limit rotational speed of the resonance band. The target supply amount is set to a small value so that the engine speed at the time of fuel supply in the next cycle is less than the lower limit speed of the resonance band, and the engine speed is the predetermined speed and the lower limit speed of the resonance band. The target supply amount when fuel is supplied to increase the rotational speed from a state between the engine speed and the engine speed when the fuel is supplied in the next cycle exceeds a maximum rotational speed of the resonance band. Set to
In the threshold value setting step, the predetermined rotation number, and the lower limit rotation number and the upper limit rotation number of the resonance band are shifted to a lower rotation side when the outside air temperature is higher than when it is low. A control method of a compression ignition engine characterized by the above. In the control method of the compression ignition type engine according to any one of claims 1 to 3,
In the fuel supply amount setting step, the target supply amount when fuel is supplied in order to increase the engine speed from a state where the engine speed is higher than the upper limit engine speed of the resonance band is set to the upper engine speed and the engine engine speed. When the difference between and is small, it is set to be smaller than when it is large,
In the threshold value setting step, the upper limit number of rotations of the resonance band is shifted to a lower rotation side when the outside air temperature is high than when the outside air temperature is low. An apparatus for controlling an on-vehicle compression ignition engine that includes a cylinder and a fuel supply device that supplies fuel to the cylinder, and burns the fuel supplied from the fuel supply device by self-ignition in the cylinder,
A crank angle sensor for detecting a change in the crank angle of the engine;
An outside air temperature sensor for detecting outside air temperature,
A fuel supply amount setting unit for setting a target supply amount of fuel to be supplied from the fuel supply device to the cylinder based on the engine speed specified using the crank angle sensor;
A threshold setting unit configured to set a threshold rotation speed of a resonance band based on the outside air temperature detected by the outside air temperature sensor, in which vibration is likely to increase;
The fuel supply amount setting unit sets a target supply amount when fuel is supplied to increase the rotational speed from a state where the engine rotational speed is lower than the lower limit rotational speed of the resonance band, and the engine at the time of fuel supply in the next cycle Set the value so that the rotational speed is out of the resonance band,
The control device for a compression ignition engine, wherein the threshold value setting unit shifts at least a lower limit rotational speed of the resonance band to a low rotational side when the outside air temperature is high compared to a low rotational speed. The control apparatus for a compression ignition engine according to claim 5,
The resonance band is set in a part of a region where the rotational speed is lower than the idle rotational speed,
The control device for a compression ignition engine, wherein the fuel supply amount setting unit is capable of setting a target fuel supply amount at start-up when the engine speed is lower than the idle speed. The control apparatus for a compression ignition engine according to claim 5 or 6,
The fuel supply amount setting unit is configured to supply fuel to increase the rotational speed from a state where the engine rotational speed is lower than a predetermined rotational speed that is set to a lower rotational speed than the lower limit rotational speed of the resonance band. The target supply amount is set to a small value so that the engine speed at the time of fuel supply in the next cycle is less than the lower limit speed of the resonance band, and the engine speed is the predetermined speed and the lower limit speed of the resonance band. The target supply amount when fuel is supplied to increase the rotational speed from a state between the engine speed and the engine speed when the fuel is supplied in the next cycle exceeds a maximum rotational speed of the resonance band. Set to
The threshold value setting unit shifts the predetermined rotation speed and the lower limit rotation speed and the upper limit rotation speed of the resonance band to a lower rotation side when the outside air temperature is higher than when it is low. A control device for a compression ignition engine. In the control apparatus for the compression ignition engine according to any one of claims 5 to 7,
The fuel supply amount setting unit sets the target supply amount when fuel is supplied to increase the engine speed from a state where the engine speed is higher than the upper limit engine speed of the resonance band, the upper engine speed and the engine speed. When the difference between and is small, it is set to be smaller than when it is large,
The control device for a compression ignition engine, wherein the threshold value setting unit shifts the upper limit rotation speed of the resonance band to a lower rotation side when the outside air temperature is higher than when it is low.

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