JP2010077859A - Engine starter and engine start control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine starter capable of improving fuel economy and quickly and positively restarting an engine, and an engine start control method. <P>SOLUTION: In this engine starter for restarting an engine 8 during idle stop by a preset engine restart condition being satisfied, it is estimated whether or not restarting of the engine 8 is possible by only a combustion start based on the state of the engine 8. When it is estimated that restarting is possible, a combustion start is performed, and when it is estimated that restarting is not possible, a combustion start and start assist are performed. In a state where restarting of the engine 8 is clearly possible by a combustion start, start assist is prevented from being unnecessarily performed, and electric consumption of a battery is suppressed. Further, in a state where success in starting is clearly not anticipated by only a combustion start, by performing start assist from the beginning, the engine 8 is quickly and positively restarted, and useless consumption of fuel is prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine starter and an engine start control method for restarting an engine by combustion start in which fuel is combusted in a combustion chamber of the engine during idling stop.

In recent years, with the aim of improving fuel economy and reducing CO ₂ emissions, idle stop technology has been developed that stops the engine operation while the vehicle is stopped, such as waiting for a signal, and automatically restarts the engine when the vehicle starts. Has been.

  As one of the methods for restarting the engine from the idling stop in which the engine operation is stopped, the fuel is injected into the combustion chamber using an engine that directly injects fuel into the combustion chamber (hereinafter referred to as an engine). There is known a technique (hereinafter referred to as combustion start) in which the crankshaft is rotated by burning and the engine is restarted.

  However, the probability of successful engine restart due to combustion start is not necessarily 100%. Thus, various techniques for assisting restart of the engine by rotating a crankshaft from the outside of the engine by a motor have been conventionally proposed.

  For example, in Patent Document 1, it is determined whether or not the restart of the engine by the combustion start is successful based on the rotational speed of the engine, and when it is determined that the engine has failed, the crankshaft is rotated by the start assist device. There has been proposed a technique for assisting restart of the engine.

  In Patent Document 2, the supply of excitation current to the field winding of the motor is started after the timing when the braking force starts to decrease, and then the torque current is supplied to the motor coil of the motor at the timing when the braking force further decreases. A technique for rotating the crankshaft and restarting the engine is disclosed.

  When a field winding type electric motor is used for the starting assist device, the time constant of the field winding is large, so that the torque rises slowly and there is a problem in response. However, as in the technique described in Patent Document 2, In addition, by supplying an excitation current to the field winding in advance, it is possible to generate torque instantaneously when a torque current is supplied to the motor coil, and it is determined that engine restart due to combustion start has failed. When it is done, the engine can be started immediately by driving the start assist device.

JP 2005-315197 A JP 2003-116204 A

  However, in the case of the technique disclosed in Patent Document 1, even if the combustion start alone is not clearly expected to succeed, only the combustion start is performed first, and the engine speed is successfully compared by comparing the engine speed and the threshold value. It is determined whether or not, and after obtaining the determination result that it has failed, the start assist drive by the start assist device is started. Therefore, the starting time becomes longer, and the fuel injected during that time is wasted, which may lead to deterioration of fuel consumption.

  And the technique of patent document 1 did not discuss at all about the setting method of the threshold value which judges the quality of engine restart. For example, the increasing tendency of the engine speed due to the start of combustion varies depending on the state of the engine such as the engine coolant temperature and the fuel pipe pressure.

  Therefore, if the threshold value for determining whether or not the restart is good is always fixed, when the combustion start is performed under conditions where the engine speed is difficult to increase, the engine can be restarted only by the combustion start. First, it is determined that the engine has failed to be restarted, and the electric motor is driven to consume power unnecessarily. The engine operation is performed to supplement the electric power, which may lead to deterioration of fuel consumption.

  On the other hand, in the technique described in Patent Document 2, the engine start is always assisted. Therefore, when the same technique is adopted for the engine, the engine can be restarted without external assistance by combustion start. Even here, there is a risk of consuming more power than necessary, leading to deterioration in fuel consumption.

  An object of the present invention is to provide an engine starter and an engine start control method capable of restarting an engine quickly and reliably while improving fuel efficiency.

  An engine starter according to the present invention that achieves the above object is an engine starter that restarts an engine in an idle stop state when a preset engine restart condition is satisfied, and whether or not the engine can be restarted only by combustion start. This is estimated based on the state of the engine. When it is estimated that restart is possible, combustion start is performed, and when it is estimated that restart is not possible, start assist is performed together with combustion start.

  According to the present invention, for example, in a state where the engine can be restarted by the combustion start clearly from the state of the engine, it is possible to prevent the start assist from being performed unnecessarily and to suppress the power consumption of the battery. Further, in a situation in which success cannot be clearly expected only by the combustion start, the engine can be restarted quickly and surely by performing the start assist from the beginning, and wasteful consumption of fuel can be prevented. Therefore, fuel consumption can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of the engine starting device in the present embodiment. The engine starter is mounted on an automobile (not shown), and includes an engine 8, a field winding type electric motor 1, power conversion means 4, and a control device 12.

  The engine 8 is a direct injection engine that directly injects fuel into the fuel chamber and operates the engine. The fuel injection means (not shown) is attached to the engine 8 so that the injection port faces the combustion chamber, and is supplied with high-pressure fuel through a fuel pipe (not shown). The engine 8 constitutes combustion starting means.

  The field winding type electric motor 1 includes a stator winding 2 and a field winding 3. The field winding type motor 1 and the engine 8 are connected to each other between a rotating shaft 1a of the field winding type motor 1 and a crank shaft 8a of the engine 8 by a power transmission means 7 such as a belt, and rotate integrally with each other. It is connected so that the rotational driving force of the field winding type electric motor 1 can be transmitted to the engine 8, and the rotational driving force of the engine 8 can be transmitted to the field winding type electric motor 1.

  The power conversion means 4 is constituted by, for example, a rectifier, converts DC power from the battery 6 into three-phase AC power, and supplies it to the field winding type electric motor 1. A field circuit 5 is incorporated in the power conversion means 4. The field circuit 5 operates so that the electric power from the battery 6 corresponds to a desired current value, and supplies electric power to the field winding 3 of the field winding type electric motor 1.

  The field winding type motor 1 operates as an electric motor by receiving excitation current from the field circuit 5 to the field winding 3 and torque current to a motor coil (not shown). The field winding type motor 1, the power conversion means 4, and the battery 6 constitute a start assist means.

  Further, by being rotated by the rotational driving force of the engine 8, an electromotive force is induced in the stator winding 2 to generate three-phase AC power, and the power conversion means 4 provided in the field winding type electric motor 1 is provided. It operates as a generator that supplies electric power to the battery 6 via.

  The engine coolant temperature Tw, the engine speed N, and the fuel pipe pressure P of the engine 8 are detected by the temperature detecting means 9, the engine speed detecting means 10, and the pressure detecting means 11, respectively, and are LIN (Local Interconnect Network) or CAN. It is sent to the control device 12 through communication means 16 such as (Control Area Network).

  Further, whether the brake pedal is depressed or whether the accelerator pedal is depressed is detected by the brake pedal sensor 17 and the accelerator pedal sensor 18, and a detection signal thereof is input to the control device 12.

  The control device (control means) 12 is configured by a computer having a CPU, a storage means, and the like, and executes a program preset in the storage means, thereby controlling the fuel injection control, ignition timing control, and engine of the engine 8. Perform restart control. Since the fuel injection control and the ignition timing control are the same as those in the prior art, detailed description thereof is omitted. In engine restart control, by executing a program, idle stop control means 13, combustion start availability estimation means 14, and engine restart quality determination means 15 are realized as internal functions of the control device 12.

  The idle stop control means 13 automatically stops the engine 8 by stopping the fuel supply to the combustion chamber when a preset engine stop condition is satisfied, and the preset engine start condition is satisfied. Occasionally, idle stop control is performed to automatically start the engine 8 by burning fuel in the combustion chamber.

  The combustion start possibility estimation means 14 performs processing for estimating whether or not the engine 8 can be restarted only by combustion start based on the state of the engine 8 such as the engine coolant temperature Tw and the pressure P in the fuel pipe. . The engine restart quality determination means 15 performs a process of determining whether or not the engine 8 has been successfully restarted based on the engine speed.

  Next, a restart control method for the engine 8 for restarting the engine 8 during idle stop will be described with reference to the flowchart of FIG.

  First, in step S101, it is determined whether or not the engine 8 is idling. Whether or not the engine is idling is determined based on a detection signal from the engine speed detecting means 10. For example, when the engine speed is 0, it is determined that the engine is idling.

  If the idle stop is being performed (YES in step S101), the process proceeds to step S102 and subsequent steps. If the idle stop is not being performed (NO in step S101), the process is terminated (END).

  In steps S102 to S302, processing for estimating whether or not the engine 8 can be restarted only by combustion start and processing for setting an engine restart pass / fail judgment threshold are performed according to the state of the engine 8. .

  First, in step S102, it is determined whether or not the engine coolant temperature Tw is equal to or higher than a preset reference temperature T2 (first reference temperature). If it is equal to or higher than the reference temperature T2 (YES in step S102), step S102 is performed. The process proceeds to S103.

  In step S103, it is determined whether or not the fuel pipe pressure P is equal to or higher than a preset reference pressure P2 (first reference pressure). If the fuel pipe pressure P is equal to or higher than the reference pressure P2 (step S103). The process proceeds to step S104, and the engine restart quality determination threshold value N2 (first engine restart quality determination threshold value) is set in step S104. Then, the process proceeds to step S105, and the combustion start possibility estimation flag is set to 1 indicating that the combustion start can be estimated (f = 1).

  On the other hand, if it is determined in step S102 that the engine coolant temperature Tw is lower than the reference temperature T2 (NO in step S102), or if it is determined in step S103 that the fuel pipe pressure P is lower than the reference pressure P2. (NO in step S103), the process proceeds to step S201.

  In step S201, it is determined whether or not the engine coolant temperature Tw is equal to or higher than a reference temperature T1 (second reference temperature). If it is equal to or higher than the reference temperature T1 (YES in step S201), the process proceeds to step S202.

  In step S202, it is determined whether or not the fuel pipe pressure P is equal to or higher than a preset reference pressure P1 (second reference pressure). If the fuel pipe pressure P is equal to or higher than the reference pressure P1 (step S202). YES), the process proceeds to step S203, and an engine restart quality determination threshold value N1 (second engine restart quality determination threshold value) is set in step S203.

  Then, the process proceeds to step S105, and the combustion start possibility estimation flag is set to 1 indicating that the combustion start can be estimated (f = 1). As described above, the engine restart pass / fail judgment threshold values N1 and N2 are changed and set according to the state of the engine 8 such as the engine coolant temperature Tw and the fuel pipe internal pressure P.

  Further, when it is determined in step S201 that the engine coolant temperature Tw is lower than the reference temperature T1 (NO in step S201), or when it is determined in step S202 that the internal pressure P of the fuel pipe is lower than the reference pressure P1. (NO in step S202), the process proceeds to step 301.

  In step S301, it is presumed that combustion start is impossible, that is, the engine 8 cannot be restarted only by combustion start, and in step S302, the combustion start possibility estimation flag is set to 0 indicating the estimation result that combustion start is impossible. (F = 0).

  Next, in steps S401 to S404, processing for determining whether or not the restart condition of the engine 8 is satisfied is performed. In step S401, it is determined whether or not the brake pedal is in a brake-off state. If the brake is off (YES in step S401), the process proceeds to step S501 assuming that the restart condition is satisfied.

  If the brake pedal is depressed (NO in step S401), the process proceeds to step S402 to make a determination based on depression of the accelerator pedal.

  In step S402, it is determined whether or not the accelerator pedal is depressed, and if the accelerator pedal is on (YES in step S402), the process proceeds to step S501 assuming that the restart condition is satisfied. If the accelerator is in an off state where the pedal is not depressed (NO in step S402), the process proceeds to step S403 to make a determination based on the remaining amount of the battery 6.

  In step S403, it is determined whether or not the remaining amount of the battery 6 is equal to or less than a preset threshold value. If it is equal to or less than the threshold value (YES in step S403), the engine 8 needs to be started and the battery 6 needs to be charged. Therefore, the process proceeds to step S501 assuming that the restart condition is satisfied. If the remaining amount of the battery 6 is equal to or greater than the threshold (NO in step S403), the process proceeds to step S404 to make a determination based on the load on the auxiliary machinery.

  In step S404, it is determined whether or not the load on the auxiliary equipment has increased due to the operation of the car air conditioner or the wiper, the lighting of the headlamp, or the like. If the load on the auxiliary equipment increases and there is a need for power generation (YES in step S404), it is determined that the restart condition is satisfied, and the process proceeds to step S501. If there is no increase in the load on the auxiliary equipment, (NO in step S404), the process returns to step S401, and the loop from step S401 to step S404 is repeated until the engine restart condition is satisfied.

  In step S501, combustion start of the engine 8 is started, and at the same time, supply of excitation current to the field winding 3 of the field winding type electric motor 1 is started. In step S502, it is determined whether or not the combustion start possibility estimation flag is set to 1. If the combustion start possibility estimation flag is set to 1 (YES in step S502), restart of the engine 8 is successful. The process proceeds to step S503 to determine whether or not the process has been performed.

  In step S503, the actual engine speed is compared with the engine restart pass / fail judgment threshold value at the determination timing tc set after a preset time has elapsed since the start of combustion start. It is determined whether or not the value is larger than the restart pass / fail judgment threshold (high rotation).

  For example, when the engine restart pass / fail judgment threshold value N2 is set in step S104, the actual engine speed N and the engine restart pass / fail judgment threshold value N2 are compared, and in step S203, the engine restart pass / fail judgment threshold value N1 is set. If it is set, the actual engine speed is compared with the engine restart pass / fail judgment threshold value N1.

  If the actual engine speed is greater than the engine restart pass / fail judgment threshold value (YES in step S503), it is determined that the engine 8 has been successfully restarted, and the process ends (END).

  On the other hand, if the actual engine speed is equal to or less than the engine restart pass / fail judgment threshold value in step S503 (NO in step S503), it is determined that the engine 8 has failed to be restarted, and start-up assistance by the field winding motor 1 is performed. To do so, go to step S601.

  When the combustion start possibility estimation flag is set to 0 in step S502 (NO in step S502), the probability that the engine 8 will be restarted successfully by combustion start is low. The process proceeds to step S601.

  In step S601, a torque assist is supplied to the motor coil of the field winding type electric motor 1 to drive the field winding type electric motor 1, and the crankshaft 1a is rotated to assist the start of the engine 8.

  Then, returning to step S503, it is determined whether or not the engine speed is equal to or higher than the engine restart quality determination threshold value. If the engine speed is larger than the engine restart quality determination threshold value (YES in step S503). ), It is determined that the engine 8 has been successfully restarted, and the processing is terminated (END).

  Next, based on FIG. 3, an example of a method for determining whether or not combustion start of the engine 8 is possible and setting threshold values N1 and N2 for determining whether or not the engine is restarted will be described.

  For example, as shown in FIGS. 3B and 3A, the engine coolant temperature Tw is lower than the reference temperature T1 (T1> Tw), or the fuel pipe pressure P is lower than the reference pressure P1 (P1> P). When either one of these is true, the success probability of combustion start is low, so it is determined that combustion start is impossible, and the determination result of whether combustion start is possible is 0 indicating that combustion start is impossible.

  Then, as shown in FIGS. 3B and 3B, the engine coolant temperature Tw is between the reference temperature T1 and the reference temperature T2 (T1 ≦ Tw <T2), and the fuel pipe pressure P is higher than the reference pressure P1. When the pressure is high (P1 <P), or the pressure P in the fuel pipe is between the reference pressure P1 and the reference pressure P2 (P1 ≦ P <P2), and the engine coolant temperature Tw is equal to or higher than the reference temperature T1 (T1 ≦ In the case of (Tw), it is determined that the combustion start is possible, and the determination result of whether combustion start is possible is 1 indicating that combustion start is possible. However, in such a situation, it is presumed that the increasing tendency of the engine speed is slower than usual. Therefore, the threshold value of the engine speed that is the determination criterion of the start / fail judgment is the engine restart pass / fail judgment threshold N1 (N1 <N2 ).

  Finally, as shown in FIGS. 3B and 3C, when the engine coolant temperature Tw is equal to or higher than the reference temperature T2 (T2 ≦ Tw), and the fuel pipe pressure P is equal to or higher than the reference pressure P2 (P2 ≦ P). Since it is a condition where combustion start is likely to be successful, the determination result of whether combustion start is possible is 1. In addition, since it is estimated that the engine speed after the combustion start is increasing as usual, the threshold value of the engine speed that is the determination criterion for determining whether the engine is restarting is higher than the engine restart determining threshold value N1. The engine restart quality determination threshold value N2 that is the engine speed is set.

  FIG. 4 is a diagram showing changes in engine speed due to differences in the state of the engine 8. The change in the engine speed indicated by the solid line in FIG. 4A is caused by the combustion start condition 1 that is the state of the engine 8, that is, as shown in FIGS. The increase in the rotational speed when the combustion start is performed under the combustion start conditions suitable for the combustion start such that the temperature is higher than T2 (T2 <Tw) and the pressure P in the fuel pipe is higher than the reference pressure P2 (P2 <P). Represents.

  On the other hand, the change in the engine speed indicated by the dotted line in FIG. 4A is based on the combustion start condition 2 that is the state of the engine 8, that is, the engine coolant Tw is the reference as shown in FIGS. When the temperature is between the temperature T1 and the reference temperature T2 (T1 ≦ Tw <T2) and the fuel pipe pressure P is equal to or higher than the reference pressure P1 (P1 ≦ P), or as shown in FIGS. In addition, the combustion start is performed in a state where the fuel pipe internal pressure P is between the reference pressure P1 and the reference pressure P2 (P1 ≦ P <P2) and the engine coolant temperature Tw is equal to or higher than the reference temperature T1 (T1 ≦ Tw). This represents an increase in the rotational speed.

  Under this condition, when the combustion start is performed under the combustion start condition 2, the increase in the engine speed after the combustion start is slower than when the combustion start is performed under the combustion start condition 1. Therefore, if the engine restart pass / fail judgment threshold value is always fixed to the value N2, the engine speed does not exceed the engine restart pass / fail judgment threshold value N2 at the time of the determination timing tc under the combustion start condition 1, so that only the combustion start is performed. Thus, although the engine 8 can be restarted, the engine restart quality determination means 15 determines that the restart of the engine 8 has failed.

  If the engine restart quality determination threshold value is always fixed to the value N1, the engine speed after combustion start under the combustion start condition 1 slightly changes the engine restart quality determination threshold value N1 at the time of the determination timing tc. If it has exceeded, the engine restart quality determination means 15 determines that the engine 8 has been successfully restarted. Originally, the engine speed should increase above the engine restart quality determination threshold N2, and It cannot be said that it is completely successful.

  Accordingly, the degree of increase in engine speed is predicted to some extent from the combustion start conditions 1 and 2, and the engine restart pass / fail judgment thresholds N1 and N2 are changed and set based on the combustion start conditions 1 and 2 (the state of the engine 8). Therefore, it is possible to make a more accurate determination of whether or not the engine is restarted.

  Next, the operation when the restart of the engine 8 fails as a result of performing only the combustion start based on the estimation result that the engine 8 can be restarted only by the combustion start will be described with reference to FIG. FIG. 5 is a time chart showing changes in the engine speed, the excitation current, and the motor torque when the restart of the engine 8 by only the combustion start fails.

  The combustion start possibility estimation means 14 estimates that the engine 8 can be restarted only by combustion start, and after the preset engine restart condition (see step S401 to step S404) is satisfied, the engine is timed at time t1. 8 combustion start and excitation of the field winding type electric motor 1 are started (see step S501). At this time, it is presumed that the engine 8 can be restarted only by the combustion start, and therefore the start assist by the field winding type electric motor 1 is not performed.

  Then, after the combustion start is executed, the engine restart quality determination is performed at the timing of time t2. In this case, the engine speed is below the engine restart quality determination threshold N (indicated by a broken line in FIG. 5), so that combustion is performed. It is determined that the restart of the engine 8 only by the start has failed.

  Therefore, starting assistance is performed by the field winding type electric motor 1, and torque current is supplied to the motor coil of the field winding type electric motor 1. Thereby, torque is instantly generated and start assist is started immediately.

  At the time of starting the start assist, the engine 8 has started to rotate to some extent by the combustion start. Therefore, the start assist time by the field winding type electric motor 1 is determined from the state in which the engine 8 is completely stopped. This can be done in a shorter time than the case, and the power consumption of the battery 6 can be suppressed and the fuel efficiency can be improved accordingly.

  If it is determined by the engine restart quality determination means 15 that the engine has been successfully started at time t3, the field winding type motor 1 stops assisting and the field winding type motor 1 shifts to the power generation mode. .

  Next, based on the estimation result that it is impossible to restart the engine 8 only by the combustion start, the operation when the combustion start and the start assist are performed from the beginning will be described with reference to FIG. FIG. 6 is a time chart showing changes in engine speed, excitation current, and motor torque when it is estimated that restart of the engine 8 is impossible only by combustion start.

  The combustion start possibility estimation means 14 estimates that restart of the engine 8 is impossible only by combustion start, and after a preset engine restart condition (see step S401 to step S404) is satisfied, the timing at time t1 Thus, the combustion start of the engine 8 and the excitation of the field winding type electric motor 1 are started simultaneously (see step S501).

  Then, torque is applied to the motor coil of the field winding type electric motor 1 at the timing of time t2 when the exciting current supplied to the field winding 3 of the field winding type electric motor 1 rises to a value sufficient to generate torque. A current is supplied to generate torque, and the engine 8 is started to assist.

  In this case, since it is already estimated by the combustion start possibility estimation means 14 that the engine 8 cannot be restarted only by the combustion start, the field is determined without waiting for the judgment result by the engine restart quality judgment means 15. The start assist of the engine 8 is performed by the winding type electric motor 1. Therefore, it is possible to avoid delaying the start of the engine 8 unnecessarily because only the combustion start is performed first as in the prior art even though the probability of the successful start of combustion is low.

  When the engine speed is higher than the engine restart quality determination threshold value N at the timing of time t3 and the engine restart quality determination means 15 determines that the engine 8 has been restarted successfully, The start assist by the magnetic winding type motor 1 is stopped, the engine speed increases to the idle speed, and the field winding type motor 1 shifts to the power generation mode.

  According to the engine starter and the engine start control method described above, it is estimated based on the state of the engine 8 whether or not the engine 8 can be restarted only by combustion start, and when it is estimated that restart is possible, the combustion start is performed. If it is estimated that the engine cannot be restarted, the start assist is performed together with the combustion start. Therefore, for example, in the state where the engine 8 can be restarted by the combustion start clearly from the state of the engine 8, it is unnecessary. It is possible to prevent the start assist from being performed, and to suppress the power consumption of the battery 6.

  Further, in a situation where success cannot be clearly expected only by combustion start, the field winding type motor 1 is driven from the beginning to perform start assist, thereby quickly restarting the engine 8 and preventing wasteful consumption of fuel. be able to. Therefore, fuel consumption can be improved.

  Further, according to the engine starter and the engine start control method described above, the engine restart pass / fail judgment threshold value is changed and set according to the state of the engine 8 such as the engine coolant temperature Tw and the fuel pipe internal pressure P. When the combustion start is performed under conditions where the rotational speed is difficult to increase, the engine restart pass / fail judgment threshold value is changed to a low value.

  Therefore, it is possible to prevent the engine 8 from being determined to have failed to restart even though the engine 8 can be restarted only by combustion start, and the field winding type motor 1 is driven wastefully. Can be prevented. Therefore, it is possible to prevent unnecessary power consumption by driving the field winding type electric motor 1, shorten the operation time of the engine 8 for supplementing the power consumption, and improve fuel consumption.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the engine cooling water temperature Tw and the fuel pipe internal pressure P are used as the state of the engine 8 for estimating whether combustion start is possible, but other parameters or more parameters are used. It may be used.

  Further, the engine restart quality determination threshold value N is changed using the engine coolant temperature Tw and the fuel pipe internal pressure P, but may be set using other parameters or more parameters.

  In this embodiment, the engine restart pass / fail judgment threshold is set in two stages, N1 and N2. However, the engine restart pass / fail judgment threshold may be set in more stages. The accuracy of the pass / fail judgment by the judging means can be improved.

1 is a block diagram schematically showing a configuration of an engine starter in the present embodiment. The flowchart explaining the engine starting control method in this Embodiment. The figure which shows the setting method of the judgment decision | availability of combustion start, and the engine restart quality judgment threshold value. The figure which shows the change of the engine speed by the difference in an engine state. 6 is a time chart showing changes in engine speed, excitation current, and motor torque when combustion start fails. 6 is a time chart showing changes in engine speed, excitation current, and motor torque when it is estimated that combustion cannot be started.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Field winding type motor 1a Rotating shaft 2 Stator winding 3 Field winding 4 Power conversion means 5 Field circuit 6 Battery 7 Power transmission means 8 Engine 8a Crankshaft 9 Temperature detection means 10 Engine rotation speed detection means 11 Pressure Detection means 12 Control device 13 Idle stop control means 14 Combustion start possibility estimation means 15 Engine restart quality judgment means 16 Communication means 17 Brake pedal sensor 18 Accelerator pedal sensor

Claims (10)

In an engine starter that restarts an engine during idle stop when a preset engine restart condition is satisfied,
Based on the state of the engine, it is estimated whether or not the engine can be restarted only by starting the combustion. When it is estimated that the engine can be restarted, the combustion is started. An engine starter characterized in that start assist is performed at the same time as starting. In an engine starter that restarts an engine during idle stop when a preset engine restart condition is satisfied,
Combustion starting means for restarting the engine by burning fuel in the combustion chamber of the engine;
A start assist means having an electric motor connected to the crankshaft of the engine, and assisting restart of the engine by rotating the electric motor;
Control means for controlling the combustion start means and the start assist means,
The control means estimates whether or not the engine can be restarted only by combustion start by the combustion start means based on the state of the engine, and when it is estimated that restart is possible, combustion start by the combustion start means The engine starting device is characterized in that when it is estimated that restarting is impossible, the starting assist is performed by the start assisting means together with the combustion starting by the combustion starting means.   3. The engine starter according to claim 2, wherein when the engine restart by the combustion start unit fails, the control unit performs start assist by the start assist unit. 4.   The control means compares the actual engine speed at a determination timing set after a preset time has elapsed from the start of combustion start by the combustion start means and an engine restart pass / fail judgment threshold, When the actual engine speed is higher than the engine restart quality determination threshold, it is determined that the engine has been successfully restarted. When the actual engine speed is less than the engine restart quality determination threshold, the engine restart is determined. The engine starter according to claim 2 or 3, wherein it is determined that the start has failed.   5. The engine starter according to claim 4, wherein the control unit changes and sets the engine restart pass / fail judgment threshold according to a state of the engine. Engine cooling water temperature detecting means for detecting the engine cooling water temperature, and fuel pipe pressure detecting means for detecting the pressure in the fuel pipe of the fuel injection means for injecting fuel into the combustion chamber,
The engine starting device according to any one of claims 2 to 5, wherein the control means detects the state of the engine based on the engine coolant temperature and the pressure in the fuel pipe.   The control means restarts the engine only by the combustion start by the combustion start means when the engine coolant temperature is not less than a preset reference temperature and the pressure in the fuel pipe is not less than a preset reference pressure. When it is estimated that the engine coolant temperature is lower than the reference temperature or at least one of the cases where the pressure in the fuel pipe is lower than the reference pressure, the engine is only required to start combustion by the combustion starting means. The engine starter according to claim 6, wherein it is estimated that restart of the engine is impossible.   The control means sets a first engine restart pass / fail judgment threshold when the engine coolant temperature is equal to or higher than a first reference temperature and the pressure in the fuel pipe is equal to or higher than the first reference pressure, and the engine coolant temperature is The temperature is between a first reference temperature and a second reference temperature set lower than the first reference temperature, and the pressure in the fuel pipe is lower than the first reference temperature and the first reference temperature. And a second engine restart pass / fail judgment threshold value that is lower than the first engine restart pass / fail judgment threshold value when the pressure is between the second reference pressure and the second reference pressure. The engine starter according to claim 6 or 7.   When the motor of the start assist means is a field winding type motor, supply of an excitation current to the field winding of the motor is started simultaneously with the start of combustion start by the combustion start means, and start by the start assist means The engine starter according to any one of claims 2 to 8, wherein supply of torque current to the motor coil of the electric motor is started simultaneously with the start of assist. In an engine start control method for restarting an engine in an idle stop by control of a computer when a preset engine restart condition is satisfied,
Estimating whether the engine can be restarted only by starting combustion based on the state of the engine;
If it is estimated that the engine can be restarted, starting combustion, and
An engine start control method, comprising: a step of performing start assist together with combustion start when it is estimated that the engine cannot be restarted.

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