JP5752917B2 - Engine starter - Google Patents

Description

  The present invention relates to an engine starter using a swingback function that temporarily rotates a crankshaft in the reverse direction in response to a high load range in a compression stroke at the time of engine start.

  Conventionally, a prior art of an engine starter that performs swingback by detecting a crank angle when the engine is started is known (see Patent Document 1). That is, in this prior art, cranking is performed by reversely rotating the crankshaft just before the compression top dead center based on the crank angle detected at the time of starting the engine and then rotating in the forward direction. If such a swingback function is used, cranking can be started from a position that is in a light load range as viewed in the forward rotation direction of the engine (before the compression top dead center in the reverse direction), so the output torque of the motor is relatively small However, it is considered that the high load range near the compression top dead center can be easily overcome.

JP 2003-343404 A (paragraphs 0040 and 0046, FIG. 1 and FIG. 6)

  The above prior art detects a mechanical crank angle when realizing the swingback function, and uses a rotor angle sensor as a sensing device for that purpose. The rotor angle (position) sensor is composed of a Hall element or a magnetoresistive (MR) element. Even in the above-described prior art, a plurality of sensor elements are used to detect the rotor angle in conjunction with the crank angle. It is mounted on the periphery (for example, the outer periphery of the boss).

  The rotor angle sensor can also be used for phase control (energization control) when driving a brushless motor. That is, in general, a drive control circuit (motor driver) for a brushless motor detects a position (phase) relating to the rotation of the motor with reference to the output of the rotor angle sensor, and controls energization timing for the stator coil.

  However, in order to accurately detect the rotor angle with a non-contact sensor such as a Hall element or a magnetoresistive element, it is necessary to arrange the individual sensor elements with extremely high accuracy, and advanced technology is required for their mounting. Is done. Moreover, since a position detecting magnet or the like must be mounted separately from the rotor as required, there is a problem that the number of parts increases accordingly.

  For this reason, from the viewpoint of miniaturization and cost reduction of the motor, it is desired to realize a technology for detecting the angle (position) of the rotor without using a device such as a Hall element and performing drive control without a sensor. . However, if the sensor is completely abolished in the drive control of the motor, it will no longer be possible to detect the crank angle linked to the rotor position at the start of the engine. In this case, the above swing back function is realized. Another problem arises that it becomes impossible.

  Accordingly, an object of the present invention is to provide a technique that can effectively use the swingback function when starting the engine even when the motor drive control is performed without a sensor.

In order to solve the above problems, the present invention employs the following solutions.
The engine starter according to the present invention drives the motor in the direction of rotating the engine in reverse according to the start operation of the engine, and then moves the motor in the direction of rotating the engine forward based on the change in the current value supplied to the coil. The drive is switched.

  That is, in the above solution, even if the rotor position and the crank angle of the engine are not detected, the vicinity of the compression top dead center is reached from the change in the current value (detected current) supplied to the coil during reverse rotation (swing) In this case, the motor drive is switched from reverse rotation to normal rotation. Thereby, a swingback function at the time of starting the engine can be realized without using a rotor position sensor.

  Preferably, in the above solution, when the current value detected while driving the motor in the direction of rotating the engine in the reverse direction is equal to or greater than a predetermined set value, the driving of the motor is switched in the direction of rotating the engine in the forward direction. And

  When the engine is reversely rotated from a stopped state, the load generated before the reverse compression top dead center and the current value supplied to the motor coil as a result will be tested in advance. We can know through etc. Therefore, if the above set value is determined in advance from the current value expected to occur before (in the vicinity of) the compression top dead center in the reverse direction, it can be easily determined based on the change in the current value detected at the actual start. The driving of the motor can be switched from the reverse rotation to the forward rotation.

  Preferably, in the above solution, when the current value detected while driving the motor in the direction of rotating the engine in the reverse direction continues for a predetermined set time, the engine rotates forward. The driving of the motor can be switched in the direction to be generated.

  In this case, even if the current value may change beyond the set value due to some factor (for example, external noise) in the situation where the compression top dead center in the reverse direction is not actually reached, the change continues. If it is not typical but temporary, the motor can be continuously driven in reverse rotation. Thereby, malfunction at the time of engine starting can be prevented, and a swing back function can be realized reliably.

  In the engine starter according to the present invention, it is also possible to execute the control for reducing the ratio of the energization time during which the current is supplied to the motor coil while the motor is being driven in the reverse direction of the engine. .

  As described above, in the swingback at the time of starting, it is known that the value of the current flowing through the motor near the compression top dead center in the reverse direction changes to a set value or more. This is based on the assumption that the inductance of a plurality of coils is almost uniform. Actually, even if each coil has the same number of turns, the total length of the windings between the coils due to manufacturing variations May be different, or the windings used may not be homogeneous from coil to coil. Therefore, in practical use, it is unlikely that the inductance is completely uniform in all coils.

  For this reason, in the swingback at the time of starting the engine, even if the compression top dead center is not yet reached, if a coil having a large inductance that protrudes above the average is energized, the current value becomes conspicuous during that time. May rise. In this case, it is not appropriate to end the swingback only from a change in the surface current value, and more careful consideration is required for motor drive control.

  Therefore, in the present invention, in the swingback at the time of starting, the influence due to the inductance variation for each coil is removed by executing together with the control for reducing the ratio of the energization time when the motor is driven in the reverse direction. That is, when the ratio of the energization time to the coil is reduced during driving of the motor, the value of the current flowing through the coil is usually considered to be reduced accordingly. Such a phenomenon appears evenly with respect to a coil having a larger inductance than the average.

  Therefore, if the actual current value clearly rises (changes) on the contrary even though the ratio of the energization time is reduced at the time of swingback, this is not due to the variation in inductance among coils. In other words, it can be understood (determined) that it accurately represents that the vicinity of compression top dead center in the reverse direction has been reached by swingback. As a result, the swing back can be ended at an appropriate position based on the change in the current value, and the engine can be normally rotated from the position to start the engine appropriately.

  In this case, the ratio of the energization time during which the current is supplied to the motor coil can be gradually reduced over a plurality of stages. For example, it is preferable to maximize the ratio of energization time at the initial stage of rotation and gradually decrease the ratio of energization time as the rotation of the motor proceeds from there.

  In this case, since the coil is energized at the maximum rate at the initial stage of rotation, a sufficient torque can be obtained against the inertia from the stopped state. After that, if the motor rotates smoothly during the swingback process, the required torque also decreases accordingly.Therefore, even if the energization time ratio is decreased step by step, the torque in the reverse direction continues. Can be sufficiently obtained.

  After that, if the current value actually flowing through the coil changes noticeably at the stage when the ratio of the energization time is reduced to some extent, it has actually reached the vicinity of the compression top dead center in the reverse direction. Therefore, the swing back can be suitably terminated at that position. If the motor drive is switched from this position to the direction of normal rotation of the engine, the engine can be easily cranked from the light load range in the normal rotation direction, and the engine can be started smoothly using its inertial force. Can do.

  According to the engine starter of the present invention, the startability of the engine can be improved by realizing the swingback function at the start without using a sensor for detecting the rotor position. As a result, the motor can be reduced in size and weight and cost can be reduced, and as a whole, the number of parts can be reduced and more inexpensive products can be supplied to the market.

It is a figure showing roughly composition of an engine starting device of one embodiment. It is a flowchart which shows the example of a procedure of the start control main process which CPU performs regarding engine start control. It is a flowchart which shows the specific example of a procedure of swing back completion | finish determination processing. 6 is a timing chart showing how various values and states change over time through a start control main process and a swingback end determination process. It is the conceptual diagram which simplified and showed the machine model at the time of using a three-phase motor by 6 poles.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically illustrating a configuration of an engine starter 10 according to an embodiment. The engine starter 10 starts an engine 14 using a three-phase motor 12 that is, for example, a three-phase AC motor. The engine 14 is, for example, a four-cycle single-cylinder internal combustion engine, and functions as a drive source for the power system by being mounted on a power system (not shown) such as a motorcycle.

  The three-phase motor 12 includes, for example, U-phase, V-phase, and W-phase coils (motor coils, stator coils, etc.) 12u, 12v, and 12w, and also includes, for example, permanent magnets (magnets) as a rotor (not shown). Three permanent magnets are provided corresponding to the U-phase, V-phase, and W-phase coils 12u, 12v, and 12w, respectively. For example, an output shaft of a three-phase motor 12 is connected to a rotor (not shown), and this output shaft is connected to a crankshaft (not shown) of the engine 14.

  The engine starter 10 includes a sensorless motor driver unit 20. That is, the motor driver unit 20 can perform drive control of the three-phase motor 12 without a sensor. Here, “sensorless” means that the rotor phase is detected without mounting a rotor position sensor such as a Hall element or a magnetoresistive element on the three-phase motor 12 to realize drive control of the three-phase motor 12. ing. Since such sensorless drive control is well known, its details are omitted here.

  The motor driver unit 20 includes, for example, a three-phase driver 22. The three-phase driver 22 forms a three-phase bridge using, for example, six switching elements (MOSFETs not shown). Since the configuration of the three-phase bridge is known, the description thereof is omitted here with illustration.

The motor driver unit 20 has three driver terminals 20a, 20b, and 20c connected to the three-phase driver 22, and these driver terminals 20a, 20b, and 20c are terminals 12a, 12b, and 12c of the three-phase motor 12, respectively. It is connected to the.
Further, the motor driver unit 20 has three power terminals 20 x and 20 y connected to the three-phase driver 22. The positive and negative (+, −) terminals of the battery 24 are connected to the power terminals 20x and 20y, respectively.

  The motor driver unit 20 has a current detector 26. The current detector 26 is, for example, a magnetic proportional current sensor using the Hall effect, and the current detector 26 is a current value supplied to the coils 12 u, 12 v, 12 w of the three-phase motor 12 through the three-phase driver 22. Is detected.

  The motor driver unit 20 has a CPU (central processing unit) 30. The CPU 30 is a semiconductor integrated circuit incorporating, for example, an EEPROM 30 a or a main RAM (not shown), and the CPU 30 executes phase control of the three-phase motor 12 using the three-phase driver 22. The EEPROM 30a stores a control program, an energization control map in which energization patterns for the respective MOSFETs of the three-phase driver 22 are determined in advance, a phase angle table necessary for phase control of the three-phase motor 12, and the like (both shown) Not stored).

  In addition, the motor driver unit 20 includes a pre-driver 32. The pre-driver 32 is a transistor array such as an FET, for example, and receives a phase control signal from the CPU 30 and outputs a drive signal to the three-phase driver 22.

  A starter switch 34 is attached to a power system (not shown). The starter switch 34 is, for example, a switch component (for example, a mechanical push switch) that is operated when a user of the power system starts the engine 14.

  The signal line of the starter switch 34 is connected to the external terminal 20d of the motor driver unit 20, and when a start operation (for example, pressing operation) is performed on the starter switch 34, a start operation signal (ON signal) is transmitted through the external terminal 20d. ) Is input to the CPU 30. In the state where the starting operation is not performed, the starter switch 34 is normally OFF (normally open).

  Further, the CPU 30 can read the current value supplied to the coils 12u, 12v, 12w of the three-phase motor 12 by inputting the detection signal from the current detector 26 described above. The read current value can be used not only for motor phase control by the CPU 30 but also for the following engine start control.

[Engine start control]
FIG. 2 is a flowchart illustrating a procedure example of a start control main process executed by the CPU 30 regarding the start control of the engine 14. This start control main process is stored in the EEPROM 30a of the CPU 30 as a control program. Hereinafter, the start control main process will be described in order.

  Step S10: First, the CPU 30 takes in the current value supplied to the coils 12u, 12v, 12w of the three-phase motor 12 based on the input signal from the current detector 26. If the engine 14 is stopped and the three-phase motor 12 is not driven (when stopped), the current value taken here is “0 A”.

  Step S12: Next, based on the operation signal from the starter switch 34, the CPU 30 checks whether or not the user's operation on the starter switch 34 has been confirmed from OFF to ON. In this case, in order to prevent an excessive malfunction, it may be determined that the starter switch 34 has been determined from OFF to ON by using a delay timer for the ON signal of the starter switch 34. For example, the ON signal from the starter switch 34 is output when the start operation continues for a certain delay time (for example, several tens of ms) after the user actually starts the start operation. This prevents malfunction when the user accidentally touches the starter switch 34, and enables stable starting control of the engine 14 thereafter.

  If the user actually performs a starting operation at this time, the CPU 30 confirms that the starter switch 34 has been determined from OFF to ON (step S12: Yes), and executes the next step S14.

  Step S14: The CPU 30 confirms whether or not the current control state is before swingback. The “control state” here is a status value (flag value) set by the CPU 30 on the program, for example, and is set to “before swingback (00H)” in the default state. The status value representing the “control state” can be stored in the status area of the built-in RAM, for example. Therefore, since the “control state” is “before swingback” for the first time (step S14: Yes), the CPU 30 then proceeds to step S16.

  Step S16: Here, the CPU 30 determines an energization duty (ratio of energization time per unit time) to the motor 12. For example, a duty control map (not shown) stored in advance in the EEPROM 30a can be used to determine the energization duty. In other words, in the duty control map (not shown), a characteristic for decreasing the energization duty for the three-phase motor 12 in a stepwise manner according to the elapsed time from the start of the swingback of the engine 14 is set. For example, the energization duty is assumed to be 100% in the initial state, and thereafter decreased by 10% every time a certain time (about several tens of ms) elapses. However, such a map setting is merely an example, and other settings may be used.

  Step S18: When the energization duty is determined in the previous step S16, the CPU 30 drives the three-phase motor 12 in reverse rotation with the determined energization duty. Specifically, an energization pattern for driving the three-phase motor 12 in a direction in which the engine 14 is rotated in the reverse direction with respect to the current rotor phase is selected, and a drive signal for the three-phase driver 22 is output. Thereby, each MOSFET is switched inside the three-phase driver 22, and the energization direction (during reverse rotation driving) of the coils 12u, 12v, 12w is controlled. In addition, since the drive control itself of the three-phase motor 12 is well-known, the detailed description is abbreviate | omitted here.

  Step S20: When reverse rotation driving of the three-phase motor 12 is executed, the CPU 30 executes swingback end determination processing. In this process, it is determined whether or not to end the swingback, that is, whether or not the crank angle of the engine 14 has reached the vicinity of the compression top dead center in the reverse direction. Here, when the determination condition of “end of swing back” is satisfied, the CPU 30 sets the “control state” to “after end of swing back”. On the other hand, if the “swing back end” determination condition is not yet satisfied, the CPU 30 returns to the start control main process without particularly changing the “control state”. A specific determination method will be described later with reference to another flowchart.

[Before swingback (Swingback end determination is not established)]
When the “control state” is “before swingback”, the CPU 30 repeats the above steps S10 to S18. During this time, the three-phase motor 12 is driven in the direction in which the engine 14 is rotated in the reverse direction, and the engine 14 is swung back. Further, the energization duty for the coils 12u, 12v, 12w gradually decreases with the passage of time from the start of the swingback (step S18).

[After swing back]
Thereafter, when the swing back end determination is actually established and the “control state” is set to “after swing back end”, the CPU 30 goes through the above steps S10 to S14 (No “after swing back end”). Proceed to step S22.

  Step S22: In this case, the CPU 30 drives the three-phase motor 12 to rotate forward. Specifically, an energization pattern for driving the three-phase motor 12 in the direction in which the engine 14 is normally rotated with respect to the current rotor phase is selected, and a drive signal for the three-phase driver 22 is output. Thereby, each MOSFET is switched inside the three-phase driver 22, and the energization direction (during forward rotation driving) of the coils 12u, 12v, 12w is controlled. Thereby, the cranking of the engine 14 is actually performed.

  As the user continues to operate the starter switch 34 during the cranking of the engine 14, the CPU 30 repeatedly executes step S22 through step S10 to step S14 (No “after swingback is completed”).

  When the engine 14 is started and the user stops operating the starter switch 34, the signal from the starter switch 34 is turned off. In this case, in step S12, since it is not possible to confirm after confirmation from OFF to ON (step S12: No “others”), the CPU 30 executes step S24.

Step S24: In this case, the CPU 30 stops driving the three-phase motor 12. As a result, the power supply to the three-phase motor 12 is stopped with respect to the start control of the engine 14.
Thereafter, while it is determined that the starter switch 34 has not been determined from OFF to ON (step S12: No “others”), the CPU 30 performs step S24 through step S10 to step S12 (No “others”). repeat.

[Swingback end determination processing]
FIG. 3 is a flowchart illustrating a specific procedure example of the swingback end determination process. Hereinafter, the contents of the swingback end determination process will be described along a procedure example.

  Step S30: First, the CPU 30 checks whether or not the captured current value is equal to or greater than a set value. The “set value” here can be set in advance with reference to a current value that flows when the torque of the three-phase motor 12 is in a high load region near the compression top dead center in the reverse direction of the engine 14. . The “set value” may be experimentally set using the actual engine 14 or the three-phase motor 12. If the current value does not reach the set value (No “others”), the CPU 30 ends the swingback end determination process and returns to the start control main process.

On the other hand, when the acquired current value is equal to or greater than the set value (step S30: Yes), the CPU 30 proceeds to the next step S32.
Step S32: Here, the CPU 30 activates the timer counter and executes the measurement of the duration time. The timer counter is used until it is determined in step S30 that the current value is not greater than or equal to the set value, or after that, the “control state” is set to “after swingback”.

  Step S34: The CPU 30 determines from the value of the timer counter being measured whether the duration so far is equal to or longer than the set time. The “set time” here is based on the time when the crank angle of the engine 14 actually reaches the vicinity of the compression top dead center in the reverse direction and the torque of the three-phase motor 12 is maintained in the high load range. It can be set in advance. Here, similarly, the “set time” may be set experimentally using the actual engine 14 or the three-phase motor 12. If the continuation time up to this point has not reached the set time (No “others”), the CPU 30 ends the swing back end determination process and returns to the start control main process.

  Step S36: On the other hand, when it is confirmed that the duration time is equal to or longer than the set time (step S34: Yes), the CPU 30 changes the setting of “control state” to “after end of swingback”. As a result, the “swing back end determination” is performed on the control.

  Step S38: When the end of the swingback is determined, the CPU 30 stops the reverse drive of the three-phase motor 12 here. Then, the CPU 30 ends the swingback end determination process and returns to the start control main process.

  In the starting control main process (FIG. 2) after the return, since the process proceeds from step S14 (No “after swingback is completed”) to step S22 as described above, the control of the three-phase motor 12 by the CPU 30 is forward rotation drive. . Thereby, the cranking of the engine 14 can be started smoothly after the determination of the end of the swingback.

[Simplified model]
FIG. 4 is a timing chart showing how various values and states change over time through the start control main process and the swingback end determination process. Here, various values and states are simplified to some extent to prevent complication of the description.

[Time t0]
For example, it is assumed that the start operation by the user is performed at a certain time t0 on the horizontal axis in FIG. 4 and the change of the starter switch 34 from OFF to ON is confirmed. In this case, the determination in step S12 is (Yes) in the control by the CPU 30, and the swingback operation (reverse drive of the three-phase motor 12) is started after step S14.

[Change in current value]
In FIG. 4, (A): Here, a current waveform as a simplified model is shown. With the start of reverse drive of the three-phase motor 12, the waveform of the current value is observed as a periodic change at each phase switching point (60 °). For example, when energization of the three-phase motor 12 is started at the previous time t0, the detected current value rises to a peak value while showing a waveform close to a first-order lag response. Then, once the current value waveform falls at the next phase switching point (for example, time t1), it rises again to the next peak value while showing a waveform close to the first order lag response. Thereafter, the waveform of the current value shows a periodic change at each phase change point (for example, times t2, t3, t4).

[Energizing duty]
In FIG. 4, (B): The energization duty as the simplified model is decreased stepwise by 10% every time a certain time elapses, for example, assuming that the start initial time (time t0) of the start control is 100%. In this simplified example, for example, the energization duty is reduced to 90% after a lapse of a certain time (time t1) from the start of the start control (time t0), and the energization duty is 80% after the elapse of the next certain time (time t2). The energization duty decreases to 70% after the next fixed time has elapsed (time t3), and further decreases to 60% after the next fixed time has elapsed (time t4). Further, it can be seen that the peak value appearing in the current waveform (A) gradually decreases as the energization duty decreases gradually. Here, for simplification of explanation, the energization duty is changed for each phase switching point of the motor 12 on the time axis, but the phase switching point and the energization duty change point are not necessarily determined in actual control. There is no need to match.

[Reverse drive]
In FIG. 4, (C): With the start of the start control, the reverse drive status (for example, drive signal) is ON from time t0 on the control by the CPU 30.

[Control state]
In FIG. 4, (D): “Control state” is set to “Before swingback” by default as described above. For this reason, the “control state” remains “before swingback” from the start of start control (time t0) until the swingback end determination is made.

[Change after time t5]
For example, it is assumed that the current value becomes equal to or greater than the set value (Ia) at a certain time t5. The set value (Ia) in this case is a current value that can be generated when the high load region is reached in the vicinity of the compression top dead center in the reverse direction in the present embodiment as described above.

  When the current value becomes equal to or greater than the set value (Ia), the measurement of the duration time by the timer counter is started under the control of the CPU 30 from that time (time t5) (step S32 in FIG. 3).

[Time t6]
Thereafter, it is assumed that the state where the current value is equal to or greater than the set value (Ia) continues for the set time (τ) or longer. In this case, the condition for determining the end of the swingback is satisfied under the control of the CPU 30 (step S34 in FIG. 3: Yes).
Therefore, at time t6, the “control state” is changed to “after the completion of the swingback”, and the reverse drive of the three-phase motor 12 is stopped (OFF).

  Although the change after this is not particularly shown, the three-phase motor 12 is driven to rotate forward after the end of the swingback as described above (step S22 in FIG. 2), and the engine 14 is moved from the light load range in the forward rotation direction. Ranking can be started.

[Machine model]
FIG. 5 is a conceptual diagram showing a simplified machine model when the three-phase motor 12 is used with six poles. In this case, six-pole three-phase motors 12-1 to 12-6 are arranged every 60 ° per one rotation (360 °) of the engine 14. Each of these six-pole three-phase motors 12-1 to 12-6 is provided with three-phase coils 12u, 12v, and 12w. In FIG. 5, in order to prevent complication, the symbols of the coils 12u, 12v, and 12w are attached only to the one-pole three-phase motor 12-1. Hereinafter, an operation example in the case where the above swingback function is used in a structure in which the six-pole three-phase motors 12-1 to 12-6 are arranged will be described.

  For example, a case is assumed where the compression top dead center (TDC) of the engine 14 is located vertically above in FIG. Further, in FIG. 5, the counterclockwise direction is the forward rotation direction of the engine 14. Here, for simplification, the structure in which the three-phase motors 12-1 to 12-6 are arranged every 60 ° with the compression top dead center (TDC) as a reference is shown, but the actual arrangement is not necessarily the same. There is no need to do it.

[Start swing back]
For example, assume that the crankshaft of the engine 14 is stopped at a position near 300 ° before compression top dead center in the reverse direction in the initial state. When starting control is started from here, the three-phase motor 12 is driven in reverse as a whole as indicated by the white arrow along the outer periphery of the three-phase motor 12.

  Considering the simplified model, for example, at this time, for example, the three-phase motor 12 is driven in reverse at an energizing duty of 100% in the first 60 ° section (from 300 ° to 240 ° before reverse compression top dead center). In the section of 60 ° (from 240 ° to 180 ° before reverse compression top dead center), the reverse drive is performed with an energization duty of 90%. Then, the next 60 ° (180 ° to 120 ° before reverse compression top dead center) is reversely driven at an energization duty of 80%, and the next 60 ° (120 ° to 60 ° before reverse compression top dead center). In the section of (°), it is driven in reverse at an energization duty of 70%.

(Before reverse compression top dead center)
Then, the last 60 ° (60 ° to 0 ° before reverse compression top dead center) is reversely driven with an energization duty of 60%. However, before the compression top dead center in the reverse direction, the three-phase motor 12 becomes a high load region as a whole, and the current value flowing through the three-phase motors 12-1 to 12-6 of each pole as described above is the set value (Ia). It changes to the above. Then, when the state where the current value is equal to or greater than the set value (Ia) continues for the set time (τ) or longer, it is determined that the swingback is ended under the control of the CPU 30, and the reverse drive of the three-phase motor 12 is stopped.

  Then, as indicated by the hatched arrows along the outer periphery of the three-phase motor 12, the three-phase motor 12 is driven to rotate forward as a whole from the position before the compression top dead center in the reverse direction. It will be. Therefore, by starting cranking from the light load region in the forward rotation direction, the load at the compression top dead center can be easily overcome and the startability of the engine 14 can be improved. Here, for simplification, the energization duty is decreased every 60 °, but it is not necessary to decrease the energization duty accurately by 60 ° in actual control.

  According to the engine starter 10 of the above-described embodiment, even if the drive control of the three-phase motor 12 is performed without a sensor (no Hall element sensor is used), the swingback function is reliably realized and the engine 14 is controlled. Startability can be improved. Thus, the entire power system including the three-phase motor 12 can be reduced in size and weight, and the manufacturing cost can be greatly reduced by reducing the number of components.

  In addition, by reducing the energization duty stepwise during reverse rotation drive before swingback, it is possible to accurately determine the end of swingback and correct it without erroneously recognizing a temporary increase in current value due to noise or the like. Direction cranking can be started.

  In particular, in the structure in which a plurality of (six poles) three-phase motors 12-1 to 12-6 are arranged as shown in FIG. 5, the inductances of the coils 12 u, 12 v, 12 w are different due to manufacturing variations. Often the value is non-uniform. In this case, if there are coils 12u, 12v, and 12w that protrude from the average and have a large inductance value, the current value that flows there tends to be temporarily increased. In this embodiment, since the current value during the reverse rotation driving is equal to or greater than the set value (Ia) and the end of the swingback is determined on the condition that the state continues for the set time (τ) or longer, the inductance value is determined. This is also advantageous in that it is possible to accurately determine the end of the swingback and start cranking in the positive direction without erroneously recognizing an increase in the current value due to variations in the current.

  The present invention is not limited to the embodiments described above, and can be implemented with various modifications. In one embodiment, the energization duty is decreased by 10%, but such a decrease width may be arbitrarily changed. Further, the pattern for decreasing the energization duty is not limited to a stepwise pattern, and a pattern that continuously decreases without stepping may be employed.

  Further, the state model and the machine model listed in FIGS. 4 and 5 are merely examples, and it goes without saying that various models can be considered in practice.

DESCRIPTION OF SYMBOLS 10 Engine starter 12 Three-phase motor 12u, 12v, 12w Coil 14 Engine 20 Motor driver unit 22 Three-phase driver 24 Battery 26 Current detector 30 CPU
34 Starter switch

Claims (2)

A motor that applies torque in the forward direction or the reverse direction to the stopped engine;
A current detector for detecting a current value supplied to the coil of the motor;
In response to a start operation of the engine, the motor is driven in a direction to rotate the engine in the reverse direction so as to reduce the proportion of energization time during which current is supplied to the coil of the motor, and while the motor is being driven. A state in which the current value is equal to or greater than a predetermined set value over a predetermined set time because the change in the current value detected by the current detector has changed from a tendency toward decreasing to increasing with time. An engine starter comprising: control means for switching the drive of the motor in a direction in which the engine is rotated forward when the engine is continued . The engine starter according to claim 1 ,
The control means includes
An engine starter characterized by gradually reducing the ratio of energization time during which current is supplied to the motor coil over a plurality of stages.

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