JP2009150301A - Start control device for internal combustion engine - Google Patents

Abstract

An object of the present invention is to suppress an increase in energy consumption while avoiding that the rotational speed of an internal combustion engine stays at a rotational speed at which a resonance phenomenon is likely to occur for a long time.
An internal combustion engine start control device (1) rotates an internal combustion engine (11) capable of using a fuel (141) containing alcohol and at least until the internal combustion engine is started. A start control device for an internal combustion engine in a vehicle including a motor (12). When starting the internal combustion engine, the start control device of the internal combustion engine detects a change rate of the rotational speed until the rotational speed of the internal combustion engine reaches a lower limit value of a resonance rotational speed region in which a resonance phenomenon occurs. Means (320) and control means (310) for controlling the motor so that the fluctuation ratio increases on condition that the detected fluctuation ratio is smaller than the fluctuation threshold.
[Selection] Figure 1

Description

  The present invention relates to a technical field of an internal combustion engine start control device in a vehicle such as an internal combustion engine capable of using a fuel including gasoline and alcohol, and a hybrid vehicle including a motor / generator.

  In this type of start control device, for example, the motor is controlled based on the alcohol concentration of the alcohol-mixed fuel, the cranking rotation speed is changed, and the upper limit value of the fuel injection amount is made variable according to the alcohol concentration. A control device has been proposed (see Patent Document 1). Alternatively, at the time of restart after completion of warm-up of the internal combustion engine, the period required for the restart is measured to determine the startability rank. Based on the startability rank, a start control device has been proposed in which the torque of the motor is increased as the startability is worsened to increase the cranking rotation speed (see Patent Document 2).

  Further, there has been proposed a drive device that cranks the internal combustion engine with a relatively large cranking torque and rapidly increases the rotational speed until the rotational speed of the internal combustion engine passes through a rotational speed region where a resonance phenomenon is likely to occur. (See Patent Document 3). Further, a system has been proposed in which the fuel property (cetane number) is determined from the time required for starting the internal combustion engine and the coolant temperature at the time of starting, and combustion control is performed in accordance with the determined property ( (See Patent Document 4).

JP 2007-211659 A JP 2000-161118 A JP-A-2005-48596 JP 2002-201997 A

  However, according to Patent Document 1, the motor is controlled based only on the alcohol concentration, and the resonance phenomenon due to the rotational speed of the internal combustion engine is not considered. Then, there is a technical problem that there is a possibility of staying at a rotational speed at which resonance is likely to occur for a long time. According to Patent Documents 2 and 4, control is performed according to the time required for starting the internal combustion engine. Then, the time required for start-up is improved at the next start-up, but at the time of the start-up this time, there is a technical problem that there is a possibility that the rotation speed is likely to cause a resonance phenomenon for a long time. On the other hand, according to Patent Document 3, since the rotational speed is constantly increased, there is a technical problem that energy consumption may increase.

  The present invention has been made in view of the above-mentioned problems, for example, and is a start control device for an internal combustion engine that can suppress an increase in energy consumption while avoiding staying at a rotational speed at which resonance easily occurs for a long time. It is an issue to provide.

  In order to solve the above problems, an internal combustion engine start control device of the present invention rotates an internal combustion engine capable of using a fuel containing alcohol and at least until the internal combustion engine is started. A start control device for an internal combustion engine in a vehicle including a motor, wherein when the internal combustion engine is started, the rotation speed of the internal combustion engine reaches a lower limit value in a resonance rotation speed region in which a resonance phenomenon occurs. And a control means for controlling the motor so that the fluctuation ratio increases on condition that the detected fluctuation ratio is smaller than a fluctuation threshold.

  According to the start control device for an internal combustion engine of the present invention, a vehicle on which the start control device is mounted can use fuel containing alcohol, for example, an internal combustion engine that is an engine, and at least until the internal combustion engine is started. During this period, a motor for rotating the internal combustion engine is provided. Here, “the internal combustion engine is started” means that a normal combustion state is obtained in the combustion chamber, or that the internal combustion engine is in a complete explosion state. In other words, it means that cranking in the internal combustion engine is completed. “Rotating the internal combustion engine” typically means cranking the crankshaft of the internal combustion engine.

  The “motor” according to the present invention is typically a motor for driving the vehicle, but may be a dedicated motor for cranking an internal combustion engine such as a starter motor. Or the motor implement | achieved in a motor generator (motor generator) may be sufficient. That is, as long as it can function as a motor, it may mean a motor / generator typically used in a hybrid vehicle.

  The “fuel containing alcohol” according to the present invention is typically a mixed fuel of alcohol and another fuel such as gasoline (ie, alcohol-mixed fuel). It may be fuel.

  For example, the fluctuation rate detection means configured to include a memory, a processor, etc., when starting the internal combustion engine, until the rotational speed of the internal combustion engine reaches a lower limit value of a resonance rotational speed region in which a resonance phenomenon occurs. Detects the fluctuation rate of the engine speed. Here, the “variation ratio” according to the present invention is, for example, a fluctuation or change in the rotational speed per unit time (that is, an increase speed or a downward speed of the rotational speed), a fluctuation in the rotational speed within a predetermined period, or Means changes. Alternatively, for example, it may mean the rotational acceleration of the cranking shaft. Note that the “predetermined period” may be, for example, a period from the start of cranking to the elapse of a predetermined time, or a period from one rotation speed to another rotation speed.

  Note that “when starting the internal combustion engine” typically means, for example, a time when a start command signal is transmitted from an ECU (Electronic Control Unit), or a cranking start time of the internal combustion engine. In addition, the time when the start command signal is transmitted or the time that is slightly later than the cranking start time, the time when the start command signal is transmitted or the predetermined minute time from the cranking start time, etc. May be included.

  In addition, “until the rotational speed reaches the lower limit value of the resonant rotational speed region in which the resonance phenomenon occurs” is an arbitrary period from the start of cranking of the internal combustion engine to the time when the rotational speed reaches the lower limit value of the resonant rotational speed region. It means at a point in time or in any period. In other words, the detection may be performed until the lower limit value of the resonance rotation speed region is reached, but typically, the rotation speed is within a period until reaching a predetermined value lower than the lower limit value of the resonance rotation speed region by a margin. In addition, the detection is performed continuously, intermittently, or once within a period in which the rotational speed including the margin is estimated not to reach the lower limit value of the resonance rotational speed region.

  For example, the control means configured to include a memory, a processor, etc., detects fluctuations from when the fluctuation ratio is detected by the fluctuation ratio detection means until the rotation speed reaches the lower limit value of the resonance rotation speed region in which the resonance phenomenon occurs. On the condition that the ratio is smaller than the fluctuation threshold, the motor is controlled so that the fluctuation ratio increases. Here, the “variation threshold” according to the present invention is a value that determines whether or not to control the motor so that the variation ratio increases, and is set in advance as a fixed value or a variable value according to some parameter. Value. Such a variation threshold is determined empirically or experimentally or by simulation, for example, by determining the relationship between the variation rate and the passage time of the resonance rotation speed region, and based on the determined relationship, for example, a few seconds If it is set as a fluctuation rate that passes through the resonance speed range in a time that does not give the driver a sense of incongruity due to the occurrence of a resonance phenomenon, or a time that does not cause a problem in the drive system of the internal combustion engine or the like Good.

  If the motor is controlled so that the fluctuation rate increases according to the time until the internal combustion engine is started, there is a possibility that the passing time in the resonance rotational speed region becomes longer at the time of the current start. Further, when the internal combustion engine is started after a long time (for example, one day) from the previous start, if the motor is controlled according to the time required until the previous start, there is a possibility that the control becomes inappropriate. . On the other hand, if the motor is controlled so that the fluctuation rate always increases, the energy consumption may increase.

  However, in the present invention, the fluctuation ratio is detected by the fluctuation ratio detecting means until the rotation speed of the internal combustion engine reaches the lower limit value of the resonance rotation speed region in which the resonance phenomenon occurs. Then, on the condition that the detected fluctuation ratio is smaller than the fluctuation threshold, the motor is controlled by the control means so that the fluctuation ratio increases. For this reason, the motor can be controlled according to the fluctuation rate of the rotational speed at the start of the internal combustion engine this time. Therefore, when the detected fluctuation ratio is smaller than the fluctuation threshold, the motor can be controlled so that the fluctuation ratio increases, and the internal combustion engine can be started quickly through the resonance rotational speed region. In addition, it is possible to avoid giving the driver an uncomfortable feeling due to the vibration of the vehicle caused by staying in the resonance rotational speed region for a long time. On the other hand, if the detected fluctuation ratio is larger than the fluctuation threshold, typically, the motor can be controlled so as to maintain at least the fluctuation ratio, thereby suppressing an increase in energy consumption.

  As a result, according to the start control device for an internal combustion engine of the present invention, it is possible to suppress an increase in energy consumption while avoiding staying at a rotational speed at which a resonance phenomenon is likely to occur for a long time.

  In one aspect of the start control apparatus for an internal combustion engine according to the present invention, the control means includes determination means for determining whether or not the detected variation ratio is smaller than the variation threshold, and is determined to be smaller than the variation threshold. In this case, the motor is controlled so that the fluctuation ratio increases, and when it is determined that the fluctuation ratio is larger than the fluctuation threshold, the motor is controlled so as to maintain at least the fluctuation ratio.

  According to this aspect, for example, it is possible to determine whether or not the fluctuation ratio detected relatively easily is smaller than the fluctuation threshold by the judging means including a memory, a processor, a comparator, and the like. Very advantageous.

  The determination means determines whether or not the detected fluctuation ratio is smaller than a fluctuation threshold. The control means controls the motor so that the fluctuation ratio increases when it is determined that the fluctuation ratio is smaller than the fluctuation threshold. On the other hand, when it is determined that it is larger than the fluctuation threshold, the motor is controlled so as to maintain at least the fluctuation ratio. Here, “to maintain at least” typically means that the fluctuation rate is not reduced. That is, typically, if the rotational speed is increased at a constant rate, it means that the rate is increased at that rate. Alternatively, the motor may be controlled so that the variation rate increases slightly or slightly. In any case, the time until the determination is completed can be secured by not increasing the fluctuation ratio (for example, the speed of increase in the rotational speed) more than necessary until the determination is completed. In other words, the determination can be completed with certainty before resonance occurs. If the detected variation ratio is “equal” to the variation threshold, it may be included in either case.

  In another aspect of the internal combustion engine start control device of the present invention, the internal combustion engine further includes temperature detection means for detecting the temperature of the internal combustion engine when the internal combustion engine is started. The motor is controlled so that the torque of the motor varies according to the detected temperature on condition that the temperature is lower than a temperature threshold.

  According to this aspect, the temperature detecting means detects the temperature of the internal combustion engine when starting the internal combustion engine. Here, the “temperature of the internal combustion engine” is typically the temperature of the combustion chamber wall of the internal combustion engine or the temperature of the cooling water for cooling the internal combustion engine, but it may be the outside air temperature. The temperature detection means is not limited to starting the internal combustion engine, and may detect or measure the temperature of the internal combustion engine periodically, irregularly, or continuously. In addition, such temperature detection may be detected directly using, for example, a temperature sensor, or other parameters having a predetermined relationship with temperature are detected and calculated from the detected parameters, that is, It may be detected or estimated indirectly.

  The control means controls the motor so that the torque varies according to the detected temperature on condition that the detected temperature is lower than the temperature threshold. Here, “so that the torque is variable” typically means that a torque larger than the motor torque at the time of normal starting, such as when starting the internal combustion engine at 10 degrees Celsius, is detected. This means that the output is made according to the temperature.

  The “temperature threshold” according to the present invention is a value that determines whether or not to control the motor so as to vary the torque according to the detected temperature, and is a fixed value or according to some parameter in advance. It is a value set as a variable value. Such a temperature threshold is obtained by empirically or experimentally or by simulation, for example, by determining the relationship between the temperature of the internal combustion engine and the viscosity of the engine oil, and the viscosity of the engine oil is notable based on the determined relationship. What is necessary is just to set as temperature to become high.

  On the other hand, on the condition that the detected temperature is higher than the temperature threshold value, the control means typically controls the motor so that the torque at the normal start is output.

  As a result, for example, the viscosity of the engine oil becomes high and it is expected that the rotation speed is difficult to increase. For example, even at a low temperature such as -30 degrees Celsius, the motor is controlled so that the torque increases. Therefore, the internal combustion engine can be started quickly, which is very advantageous in practice.

  In another aspect of the start control device for an internal combustion engine according to the present invention, the control means includes a rotation speed setting means for setting a target rotation speed that is the rotation speed at which the internal combustion engine can be started, and the set target Motor control means for controlling the motor so as to reach the rotational speed.

  According to this aspect, the rotational speed setting means sets the target rotational speed that is the rotational speed at which the internal combustion engine can be started. Here, the “target rotational speed” according to the present invention is typically a rotational speed necessary for obtaining an in-cylinder pressure capable of starting the internal combustion engine, but a rotational speed larger than the rotational speed by a predetermined value. It may be a number. The motor control means controls the motor so as to reach the set target rotational speed.

  Thereby, for example, the internal combustion engine can be reliably started within a predetermined time. Alternatively, the motor can be controlled to efficiently increase the rotational speed of the internal combustion engine to reach the target rotational speed, and an increase in energy consumption can be suppressed.

  In this aspect, the engine further includes alcohol concentration detection means for detecting the concentration of alcohol contained in the fuel when the internal combustion engine is started, and the rotation speed setting means is configured to detect the concentration according to at least the detected concentration. A target rotational speed may be set.

  If comprised in this way, according to alcohol concentration, an internal combustion engine can be started appropriately and reliably, and it is very advantageous practically. In general, since alcohol is less volatile than gasoline, it is difficult to obtain an in-cylinder pressure capable of starting the internal combustion engine unless the rotational speed of the internal combustion engine is increased. It has been found by the inventor's research that the rotational speed at which the cylinder pressure capable of starting the internal combustion engine can be obtained depends on the alcohol concentration.

  The alcohol concentration detection means detects the concentration of alcohol contained in the fuel when starting the internal combustion engine. The alcohol concentration detection means is not limited to starting the internal combustion engine, and may detect or measure the concentration of alcohol contained in the fuel periodically, irregularly, or continuously. In addition, such concentration detection may be performed directly using, for example, a concentration sensor, or other parameters having a predetermined relationship with the concentration are detected and calculated from the detected parameters. It may be detected or estimated indirectly. The rotation speed setting means sets the target rotation speed according to at least the detected density. The rotation speed setting means may set the target rotation speed in accordance with, for example, the temperature of the internal combustion engine, that is, in accordance with the concentration and temperature, in addition to the detected concentration.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment according to a start control device for an internal combustion engine of the present invention will be described with reference to FIGS. In the following embodiments, an engine is taken as an example of the internal combustion engine of the present invention.

(Configuration of start control device)
First, the configuration of the engine start control device according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram of an engine start control device according to the present embodiment.

  In FIG. 1, a start control device 1 includes an engine 11 and a motor / generator as an example of a “motor” according to the present invention that rotates the engine 11 via a shaft 13 until at least the engine 11 starts. (MG) 12 and a fuel tank 14 that stores fuel 141 containing alcohol and that can supply fuel 141 to the engine 11 via a delivery pipe 15, for example, is mounted on a vehicle such as a hybrid vehicle. .

  The start control device 1 includes a rotation speed sensor 21 that detects the rotation speed of the engine 11, a temperature sensor 22 that detects the temperature of the engine 11, a concentration sensor 23 that detects the concentration of alcohol contained in the fuel 141, and an ECU 30. It is comprised with. The ECU 30 includes a CPU (Central Processing Unit) 310 having a rotation speed setting unit 311, a motor control unit 312, and a determination unit 313, a variation rate detection unit 320, a storage unit 330, and an input / output unit 340. ing.

  Based on the signal indicating the rotation speed of the engine 11 from the rotation speed sensor 21, the fluctuation ratio detection unit 320 detects a fluctuation ratio that is, for example, a fluctuation in the rotation speed per unit time. The storage unit 330 is, for example, a nonvolatile memory such as an EEPROM (Electronically Erasable and Programmable Read Only Memory), a backup ROM, or a flash memory.

  The “temperature sensor 22”, “density sensor 23”, “CPU 310”, “rotation speed setting unit 311”, “motor control unit 312”, “determination unit 313”, and “variation rate detection unit 320” according to the present embodiment. ”,“ Temperature detection means ”,“ alcohol concentration detection means ”,“ control means ”,“ rotation speed setting means ”,“ motor control means ”,“ determination means ”and“ variation ratio detection means ”according to the present invention, respectively. Is an example. In this embodiment, a part of the ECU 30 for various electronic controls is used as a part of the control device.

(Startup control process)
Next, the start control process executed by the ECU 30 in the vehicle on which the engine 11 start control device 1 configured as described above is mounted will be described with reference to the flowchart of FIG. The start control process is executed when the engine 11 is started mainly when the vehicle starts to run or when the vehicle is running only by the motor / generator 12.

  In FIG. 2, first, the temperature sensor 22 detects the temperature of the engine 11 (step S101). Subsequently, the determination unit 313 determines whether or not the detected temperature is lower than a temperature threshold value that is, for example, -20 degrees Celsius (Step S102). When it is determined that the temperature is higher than the temperature threshold value (step S102: No), the motor control unit 312 outputs the motor / generator so that the torque at the normal start time indicated by the solid line a in FIG. 12 is started to start cranking of the engine 11 (step S107).

  FIG. 3A is a conceptual diagram showing an example of a temporal change in torque output from the motor / generator 12 when the engine 11 is started in the present embodiment, and FIG. FIG. 3 is a conceptual diagram showing an example of a change over time in the rotational speed of the engine 11. Note that a band R in FIG. 3B indicates a resonance rotational speed region of the drive system including the engine 11 according to the present embodiment. The lower limit value of the resonance speed region is, for example, about 300 engine revolutions, and the upper limit value is, for example, about 400 revolutions. In addition, the engine speeds r1 and r2 in FIG. 3B indicate the target speed set by the speed setting unit 311. The engine speed r1 indicates a target speed at a normal start, and the engine speed r2 indicates a target speed when a low temperature and alcohol concentration, which will be described later, are detected.

  In the vehicle drive system according to the present embodiment, no clutch is interposed between the engine 11 and a wheel (not shown), and therefore the frequency of the engine 11 due to cranking is at least one of the components constituting the drive system. It is considered that resonance occurs due to the vicinity of the natural frequency.

  Returning to FIG. 2 again, when it is determined that the detected temperature is lower than the temperature threshold (step S102: Yes), the determination unit 313 determines whether or not the concentration of alcohol contained in the fuel 141 can be detected. (Step S103). Whether or not the concentration can be detected may be determined based on whether or not there is a response from the concentration sensor 23, for example.

  When it is determined that detection is possible (step S103: Yes), the concentration sensor 23 detects the concentration of alcohol contained in the fuel 141 (step S104). Next, the rotation speed setting unit 311 sets the target rotation speed so as to be, for example, the engine rotation speed r2 in FIG. 3A according to the detected concentration and the detected temperature. Subsequently, the motor control unit 312 changes the torque of the motor / generator 12 in accordance with the detected temperature and, for example, a broken line in FIG. 3A so as to reach the target rotational speed set within a predetermined time. The motor / generator 12 is controlled so as to output torque as indicated by d, and cranking of the engine 11 is started (step S105).

  Here, the correspondence relationship between the alcohol concentration and the temperature of the engine 11 and the cranking rotational speed necessary for starting the engine 11 will be described with reference to FIGS. 4 and 5. FIG. 4 is a characteristic diagram showing an example of the correspondence between the alcohol concentration and the cranking speed, and FIG. 5 is a characteristic showing an example of the correspondence between the temperature of the engine 11 and the cranking speed. FIG.

  The solid line T1 in FIG. 4 indicates the correspondence at −30 degrees Celsius, the broken line T2 indicates the correspondence at −10 degrees Celsius, and the alternate long and short dash line T3 indicates the correspondence at 25 degrees Celsius. . As shown in FIG. 4, it can be seen that the cranking speed increases as the alcohol concentration increases at any temperature. And the increase becomes remarkable, so that temperature becomes low.

  A solid line E85 in FIG. 5 indicates a correspondence relationship of fuel having an alcohol concentration of 85%, a broken line E20 indicates a correspondence relationship of fuel having an alcohol concentration of 20%, and an alternate long and short dash line E10 indicates a fuel having an alcohol concentration of 10%. The correspondence relationship is shown. As shown in FIG. 5, at any concentration, the cranking rotational speed increases as the temperature of the engine 11 decreases. And the increase becomes remarkable, so that alcohol concentration becomes high.

  The correspondence shown in FIGS. 4 and 5 is due to the fact that alcohol volatility is lower than gasoline volatility. In other words, the alcohol is not sufficiently vaporized unless the temperature of the air in the cylinder is increased by increasing the cranking speed and increasing the pressure in the cylinder.

  Here, the correspondence between the cranking rotation speed and the pressure in the cylinder of the engine 11 will be described with reference to FIGS. 6 and 7. FIG. 6 is a characteristic diagram showing an example of a correspondence relationship between the cranking rotational speed necessary for starting the engine 11 and the pressure in the cylinder of the engine 11 when fuel with an alcohol concentration of 85% is used. FIG. 7 is a characteristic diagram showing an example of a correspondence relationship between the cranking rotation speed necessary for starting the engine 11 and the pressure in the cylinder of the engine 11 at −30 degrees Celsius.

Each point P _T1 , P _T2, and P _T3 in FIG. 6 indicates the pressure in the cylinder necessary to start the engine 11 at −30 degrees Celsius, −10 degrees Celsius, and 25 degrees Celsius, respectively. As shown in FIG. 6, it can be seen that the lower the temperature of the engine 11, the higher the pressure in the cylinder.

Each point P _E85 , P _E50, and P _E20 in FIG. 7 indicates the pressure in the cylinder that is necessary to start the engine 11 when fuel having an alcohol concentration of 85%, 50%, and 20% is used, respectively. ing. As shown in FIG. 7, the higher the alcohol concentration, the higher the pressure in the cylinder.

  Therefore, the rotational speed setting unit 311 obtains the pressure in the cylinder necessary for starting the engine 11 by an arithmetic expression using the alcohol concentration and the temperature of the engine 11 as variables, and can obtain the obtained pressure. Calculate the cranking speed and set the target speed. Alternatively, the characteristic diagrams as shown in FIGS. 4 and 5 are stored in advance in the storage unit 330 as a map, and the engine 11 is started from the stored map based on the detected concentration and the detected temperature. The cranking rotational speed necessary for the acquisition is acquired, and the acquired cranking rotational speed is set as the target rotational speed. If it is determined that the alcohol concentration cannot be detected, the rotation speed setting unit 311 may set the target rotation speed by setting the alcohol concentration to a predetermined fixed value (for example, 0%, for example). Good.

  Returning to FIG. 2 again, when it is determined that the alcohol concentration cannot be detected (step S103: No), the rotation speed setting unit 311 sets the target rotation speed in accordance with the detected temperature. Subsequently, the motor control unit 312 changes the torque of the motor / generator 12 in accordance with the detected temperature and attains the target rotational speed set within a predetermined time, for example, in FIG. The motor / generator 12 is controlled so that torque is output as indicated by the dashed line c, and cranking of the engine 11 is started (step S104).

  Here, the target rotational speed is set as the engine rotational speed r1. Also, the two-dot chain line c in FIG. 3A changes in the same manner as the broken line d in FIG. 3A at the beginning of cranking of the engine 11 and changes in the same way as the solid line a from the middle.

  Next, after the cranking of the engine 11 is started by the processing of step S105, S106, or S107, the fluctuation ratio detecting unit 320 is until the rotation speed of the engine 11 reaches the lower limit value of the resonance rotation speed region. Detects the fluctuation ratio of the rotational speed based on the signal indicating the rotational speed of the engine 11 from the rotational speed sensor 21 (step S108). Subsequently, the determination unit 313 determines whether or not the detected variation ratio is smaller than the variation threshold (step S109).

  If it is determined that the variation is smaller than the variation threshold (step S109: Yes), the motor control unit 312 controls the motor / generator 12 so that the variation rate of the rotational speed increases (step S110). Specifically, for example, when the rotational speed changes as shown by a solid line a in FIG. 3B, the rotational speed changes as shown by an alternate long and short dash line b after time t1, as shown in FIG. The motor / generator 12 is controlled so that a torque as indicated by a one-dot chain line b in FIG. On the other hand, when it is determined that the value is larger than the fluctuation threshold value (step S109: No), the process is temporarily terminated.

  As a result, according to the start control device 1 according to the present embodiment, an increase in energy consumption can be suppressed while avoiding staying in the resonance rotational speed region for a long time.

  In the present embodiment, the concentration of alcohol contained in the fuel 141 is directly detected by the concentration sensor 23. For example, the air-fuel ratio is detected by an air-fuel ratio sensor or the like, and the detected air-fuel ratio is detected. Based on this, the concentration of alcohol may be detected or estimated. Specifically, the alcohol concentration may be detected or estimated from the air-fuel ratio fluctuation and the fuel supply amount. This is because, as described above, alcohol has lower volatility than gasoline, and in order to obtain a predetermined air-fuel ratio, more fuel must be supplied than gasoline-only fuel. In this case, the alcohol concentration is detected or estimated during the previous operation of the engine 11. In this case, the case where it is determined in step S103 that “alcohol concentration cannot be detected” is, for example, a case where a long time (for example, one day) has elapsed since the previous operation of the engine 11.

  It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. An engine start control device is also included in the technical scope of the present invention.

1 is a block diagram of an engine start control device according to an embodiment of the present invention. It is a flowchart which shows the starting control process which ECU which concerns on embodiment of this invention performs. FIG. 3A is a conceptual diagram showing an example of a temporal change in torque output from the motor / generator when the engine is started in the embodiment of the present invention, and FIG. It is a conceptual diagram which shows an example of the time change of rotation speed. It is a characteristic view which shows an example of the correspondence between alcohol density | concentration and cranking rotation speed. It is a characteristic view which shows an example of the correspondence between engine temperature and cranking rotation speed. FIG. 5 is a characteristic diagram showing an example of a correspondence relationship between a cranking rotational speed necessary for starting the engine and a pressure in a cylinder of the engine when a fuel having an alcohol concentration of 85% is used. FIG. 5 is a characteristic diagram showing an example of a correspondence relationship between cranking rotation speed necessary for starting the engine and pressure in a cylinder of the engine at −30 degrees Celsius.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Start control apparatus, 11 ... Engine, 12 ... Motor generator, 13 ... Shaft, 14 ... Fuel tank, 15 ... Delivery pipe, 21 ... Revolution sensor, 22 ... Temperature sensor, 23 ... Concentration sensor, 30 ... ECU, 141 ... Fuel, 310 ... CPU, 311 ... Rotation speed setting unit, 312 ... Motor control unit, 313 ... Determination unit, 320 ... Fluctuation ratio detection unit, 330 ... Storage unit

Claims (5)

An internal combustion engine capable of using a fuel comprising alcohol, and a start control device for the internal combustion engine in a vehicle comprising a motor that rotates the internal combustion engine at least until the internal combustion engine starts.
When starting the internal combustion engine, a fluctuation ratio detecting means for detecting a fluctuation ratio of the rotation speed until the rotation speed of the internal combustion engine reaches a lower limit value of a resonance rotation speed region in which a resonance phenomenon occurs.
And a control means for controlling the motor such that the fluctuation ratio increases on condition that the detected fluctuation ratio is smaller than a fluctuation threshold. The control means includes
Determining means for determining whether or not the detected variation ratio is smaller than the variation threshold;
When it is determined that the fluctuation threshold value is smaller, the motor is controlled so that the fluctuation ratio increases.
2. The start control device for an internal combustion engine according to claim 1, wherein the motor is controlled to maintain at least the fluctuation ratio when it is determined that the fluctuation threshold is larger than the fluctuation threshold. A temperature detecting means for detecting the temperature of the internal combustion engine when starting the internal combustion engine;
The said control means controls the said motor so that the torque of the said motor may vary according to the detected temperature on the condition that the detected temperature is lower than a temperature threshold value. The start control device for an internal combustion engine according to 1 or 2. The control means includes
A rotational speed setting means for setting a target rotational speed that is the rotational speed capable of starting the internal combustion engine;
The start control device for an internal combustion engine according to any one of claims 1 to 3, further comprising: motor control means for controlling the motor so as to reach the set target rotational speed. An alcohol concentration detecting means for detecting a concentration of alcohol contained in the fuel when the internal combustion engine is started;
The start control device for an internal combustion engine according to claim 4, wherein the rotation speed setting means sets the target rotation speed according to at least the detected concentration.

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