Rotary electric machine for vehicles

In a vehicular rotary electric machine, a switching section includes a bridge circuit having plurality of upper arms and plurality of lower arms. The arms include switching elements. A diode is connected in parallel to each switching element. One end of the switching element of each of the upper arms is connected to a positive terminal of a battery and one end of the switching element of each of the lower arms is connected to a negative terminal of the battery via a vehicle body. The switching section rectifies induced phase voltage of an armature winding. A section sets ON-timing of the switching elements. A section sets OFF-timing of the switching elements. When the switching element of each lower arm is OFF, a detector detects an energization period in which current flows to the diode. A calculator calculates a rotation frequency based on the detected energization period.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2010-228867 filed Oct. 8, 2010 the description of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary electric machine for a vehicle mounted in a car, a truck, and the like.

2. Description of the Related Art

An rotary electric machine for a vehicle is known, in which the output voltage of an armature winding is rectified using an inverter circuit having a plurality of switching elements (refer to, for example, Japanese Patent No. 4023353. In the rotary electric machine for a vehicle, the timing at which the switching element of a certain phase is turned OFF is set to a point at which a delay time based on rotation frequency has elapsed from a point at which the phase voltage of another phase has reached a predetermined threshold value. The rotation frequency used in control such as that described above is detected based on the amount of time between points at which the alternating-side main electrode voltages of the upper arm elements of two adjacent phases exceed a predetermined threshold value (the time difference between points at which the voltages of two phase windings exceed a predetermined threshold value).

In a vehicle power generator disclosed in Japanese Patent No. 4023353, when power generation voltage changes in accompaniment with fluctuations in electrical load and the like, the point at which the phase voltage exceeds the predetermined threshold value shifts. Therefore, a problem occurs in that the accuracy of rotation frequency detection decreases with the change in power generation voltage. For example, the power generation voltage increases when the electrical load is suddenly reduced. Therefore, the point at which the phase voltage exceeds the predetermined threshold value becomes slightly earlier. Thus, the amount of time between the two points at which rotation frequency detection is performed becomes shorter compared to when the power generation voltage is constant. A judgment that the rotation frequency has increased is erroneously made.

SUMMARY

Hence it is desired to provide an rotary electric machine for a vehicle capable of improving accuracy of rotation frequency calculation.

An exemplary embodiment provides an rotary electric machine for a vehicle is disclosed, including: an armature winding having phase windings of two phases or more; a switching section that configures a bridge circuit having a plurality of upper arms and lower arms configured by switching elements to which a diode is connected in parallel, in which one end of the switching element of the upper arm is connected to a positive terminal side of a battery and one end of the switching element of the lower arm is connected to a negative terminal side of the battery via a vehicle body, and that rectifies an induced phase voltage of the armature winding; an ON-timing setting section that sets an ON-timing of the switching elements; an OFF-timing setting section that sets an OFF-timing of the switching elements; an energization period detector that detects an energization period in which current flows to the diode connected in parallel to the switching element, when the switching element of each of the lower arms is OFF, the energization period being a period from a time when the phase voltage reaches, from a first threshold value, a second threshold; and a rotation frequency calculator that calculates rotation frequency based on the energization period detected by the energization period detector.

One end side of the switching element of the lower arm is connected (grounded) to the vehicle body. Therefore, even when sudden fluctuations in electrical load occur, the fluctuations in the power generation voltage (phase voltage) are small. Accuracy of rotation frequency calculation can be improved through use of the energization period detected based on the power generation voltage.

In addition, the above-described rotation frequency calculator preferably calculates the rotation frequency based on at least one of the cycle of a start timing and the cycle of an end timing of the energization period. In general, the start timing and the end timing of the energization period are required for the various processes required to be performed in synchronization control. Therefore, processes and configurations can be simplified by the timings also being used for rotation frequency calculation.

In addition, the above-described ON-timing setting section preferably sets the point at which the phase voltage reaches the first threshold value as the ON-timing of the switching element of the lower arm. As a result of the first threshold value used to set the ON-timing of the switching element of the lower arm also being used for rotation frequency calculation, a comparison operation of the phase voltage and the first threshold value can be shared. Processes and configurations can be simplified.

In addition, the above-described OFF-timing setting section preferably sets the OFF-timings of the respective switching elements of the upper arm and the lower arm based on the rotation frequency calculated by the rotation frequency calculator. As a result, synchronization control for turning ON/OFF the switching elements can be performed with a simple configuration, without use of a separate component, such as a sensor, for detecting the rotation frequency.

In addition, the above-described rotation frequency calculator preferably calculates a first rotation frequency based on the cycle of the start timing of the energization period, and calculates a second rotation frequency based on the cycle of the end timing of the energization period. The OFF-timing setting section preferably sets the OFF-timing of the switching element of the lower arm based on the first rotation frequency, and sets the OFF-timing of the switching element of the upper arm based on the second rotation frequency. In addition, the above-described OFF-timing setting section preferably sets the OFF-timings of the respective switching elements of the upper arm and the lower arm included in the subsequent cycle of the phase voltage based on the rotation frequency calculated by the rotation frequency calculator. As a result, OFF-control of the switching elements can be performed using the newest rotation frequency.

In addition, the above-described rotation frequency calculator preferably calculates rotation frequency by averaging at least one of the cycle of the start timing of the energization period and the cycle of the end timing taken over a plurality of cycles. As a result, the rotation frequency can be stably set, even when rotational fluctuations occur.

In addition, the above-described rotation frequency calculator preferably determines the rotation frequency by calculating K/C, when the result of the measurement of at least one of the period of the start timing of the energization period and the cycle of the end timing is C, and a coefficient for converting cycle to rotation frequency is K. As a result, the rotation frequency can be determined by a simple calculation using the obtained cycle. Processing load of rotation frequency calculation can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A vehicle power generator according to an embodiment to which an rotary electric machine for a vehicle of the present invention is applied will be described with reference to the drawings.FIG. 1is a diagram of a configuration of a vehicle power generator according to the present embodiment. As shown inFIG. 1, a vehicle power generator1according to the present embodiment includes two stator windings (armature windings)2and3, a field winding4, two rectifier module groups5and6, and a power generation control device7. The two rectifier module groups5and6correspond to a switching section.

One stator winding2is a multi-phase winding (such as a three-phase winding composed of an X-phase winding, a Y-phase winding, and a Z-phase winding) wound around a stator core (not shown). In a similar manner, the other stator winding3is also a multi-phase winding (such as a three-phase winding composed of a U-phase winding, a V-phase winding, and a W-phase winding). The stator winding3is wound around the above-described stator core in a position shifted by an electrical angle of 30 degrees from the stator winding2. According to the present embodiment, a stator is configured by the two stator windings2and3, and the stator core.

The field winding4is wound around a field pole (not shown) disposed opposing the inner peripheral side of the stator core and configures a rotor. The field pole becomes magnetized by excitation current being sent to the field winding4. The stator windings2and3generate an alternating current as a result of a rotating magnetic field generated when the field pole is magnetized.

One rectifier module group5is connected to one stator winding2and configures a three-phase full-wave rectification circuit (bridge circuit) as a whole. The rectifier module group5converts the alternating current induced in the stator winding2to a direct current. The rectifier module group5includes a quantity of rectifier modules corresponding with the quantity of phases in the stator winding2(three rectifier modules for a three-phase winding). In other words, the rectifier module group5includes rectifier modules5X,5Y, and5Z. The rectifier module5X is connected to the X-phase winding included in the stator winding2. The rectifier module5Y is connected to the Y-phase winding included in the stator winding2. The rectifier module5Z is connected to the Z-phase winding included in the stator winding2.

The other rectifier module group6is connected to the other stator winding3and configures a three-phase full-wave rectification circuit (bridge circuit) as a whole. The rectifier module group6converts the alternating current induced in the stator winding3to a direct current. The rectifier module group6includes a quantity of rectifier modules corresponding with the quantity of phases in the stator winding3(three rectifier modules for a three-phase winding). In other words, the rectifier module group6includes rectifier modules6U,6V, and6W. The rectifier module6U is connected to the U-phase winding included in the stator winding3. The rectifier module6V is connected to the V-phase winding included in the stator winding3. The rectifier module6W is connected to the W-phase winding included in the stator winding3.

The power generation control device7is an excitation control circuit that controls the excitation current sent to the field winding4connected by an F terminal. The power generation control device7adjusts the excitation current, thereby controlling the output voltage VBof the vehicle power generator1(output voltage of each rectifier module) to become a regulated voltage Vreg. For example, the power generation control device7stops the supply of excitation current to the field winding4when the output current VBbecomes higher than the regulated voltage Vreg. The power generation control device7supplies the excitation current to the field winding4when the output voltage VBbecomes lower than the regulated voltage Vreg. As a result, the power generation control device7can perform control such that the output voltage VBbecomes the regulated voltage Vreg. In addition, the power generation control device7is connected to an electronic control unit (ECU)8(external control device) by a communication terminal L and a communication line. The power generation control device7performs two-way serial communication (such as Local Interconnect Network [LIN] communication using LIN protocol) with the ECU8. Communication messages are transmitted and received.

The vehicle power generator1according to the present embodiment is configured as described above. Next, details of the rectifier module5X and the like will be described.

FIG. 2is a diagram of a configuration of the rectifier module5X. The other rectifier modules5Y,5Z,6U,6V, and6W have the same configuration. As shown inFIG. 2, the rectifier module5X includes two metal-oxide-semiconductor (MOS) transistors50and51, and a control circuit54. The MOS transistor50is an upper arm (high-side) switching element. The source of the MOS transistor50is connected to the X-phase winding of the stator winding2, and the drain is connected to a positive terminal of an electrical load10or a battery9by a charging line12. The MOS transistor51is a lower arm (low-side) switching element. The drain of the MOS transistor51is connected to the X-phase winding, and the source is connected to a negative terminal of the battery9(grounding using the vehicle body). A series circuit composed of the two MOS transistors50and51is disposed between the positive terminal and the negative terminal of the battery9. The X-phase winding is connected to the connection point of the two MOS transistors50and51. A diode is connected in parallel between the source and drain of each MOS transistor50and51. The diode is actualized by a parasitic diode (body diode) of each MOS transistor50and51. However, a diode that is a separate component may be further connected in parallel. A configuration is also possible in which a switching element other than the MOS transistor is used in at least one of the upper arm and lower arm.

FIG. 3is a diagram of a detailed configuration of the control circuit54. As shown inFIG. 3, the control circuit54includes a control section100, a power source160, an output voltage detecting section110, an upper MOS VDSdetecting section120, a lower MOS VDSdetecting section130, a temperature detecting section150, and drivers170and172.

The power source160starts operation at a timing at which the excitation current is supplied to the field winding4from the power generation control device7, and supplies operating voltage to each element included in the control circuit54. The power source160also stops supplying the operating voltage when the supply of excitation current is stopped. The power source160is started and stopped in adherence to instructions from the control section100.

An output terminal (G1) of the driver170is connected to the gate of the high-side MOS transistor50. The driver170generates a drive signal for turning ON and OFF the MOS transistor50. In a similar manner, an output terminal (G2) of the driver172is connected to the gate of the low-side MOS transistor51. The driver172generates a drive signal for turning ON and OFF the MOS transistor51.

The output voltage detecting section110is configured by, for example, a differential amplifier and an analog-to-digital converter that converts the output from the differential amplifier to digital data. The output voltage detecting section110outputs data corresponding to the voltage of the output terminal (B terminal) of the vehicle power generator1(or the rectifier module5X). The analog-digital converter may be provided on the control section100side.

The upper MOS VDSdetecting section120detects the drain-source voltage VDSof the high-side MOS transistor50. The upper MOS VDSdetecting section120then compares the detected drain-source voltage VDSwith a predetermined threshold value, and outputs a signal based on whether the detected drain-source voltage VDSis higher or lower than the predetermined threshold value.

FIG. 4is a diagram of a specific example of voltage comparison performed by the upper MOS VDSdetecting section120. InFIG. 4, the horizontal axis indicates the drain-source voltage VDSbased on the output voltage VBof the drain side. The vertical axis indicates the voltage level of the signal outputted from the upper MOS VDSdetecting section120. As shown inFIG. 4, when the phase voltage VPincreases and becomes higher than the output voltage VBby 0.3V or more, the drain-source voltage VDSbecomes 0.3V or higher. Therefore, the output signal from the upper MOS VDSdetecting section120changes from a low voltage level (0V) to a high voltage level (5V). Then, when the phase voltage VPbecomes lower than the output voltage VBby 1.0V or more, the drain-source voltage VDSbecomes −1.0V or less. Therefore, the output signal from the upper MOS VDSdetecting section120changes from a high voltage level to a low voltage level.

A value V10(FIG. 7) that is 0.3V higher than the output voltage VB, described above, corresponds with a first threshold value. The first threshold value is used to detect, with certainty, a starting point of a diode energization period. The first threshold value is set to a value higher than a value that is the sum of the output voltage VBand the drain-source voltage VDSof the MOS transistor50when the MOS transistor50is turned ON. The first threshold value is also set to a value lower than a value that is the sum of the output voltage VBand a forward voltage VFof the diode connected in parallel with the MOS transistor50. A value V20(FIG. 7) that is 1.0V lower than the output voltage VB, described above, corresponds with a second threshold value. The second threshold value is used to detect, with certainty, an end point of the diode energization period. The second threshold value is set to a value lower than the output voltage VB. A period from when the phase voltage VPreaches the first threshold value until the second threshold is reached is an “ON period” of the upper arm. The starting point and the end point of the ON period are shifted from those of the “diode energization period” when the diode is actually energized while the MOS transistor50is in the OFF state. According to the present embodiment, synchronization control is performed based on this ON period.

The lower MOS VDSdetecting section130detects the drain-source voltage VDSof the low-side MOS transistor51. The lower MOS VDSdetecting section130then compares the detected drain-source voltage VDSwith a predetermined threshold value, and outputs a signal based on whether the detected drain-source voltage VDSis higher or lower than the predetermined threshold value.

FIG. 5is a diagram of a specific example of voltage comparison performed by the lower MOS VDSdetecting section130. InFIG. 5, the horizontal axis indicates the drain-source voltage VDSbased on a ground terminal voltage VGNDthat is a battery negative-terminal voltage of the drain side. The vertical axis indicates the voltage level of the signal outputted from the lower MOS VDSdetecting section130. As shown inFIG. 5, when the phase voltage VPdecreases and becomes lower than the ground voltage VGNDby 0.3V or more, the drain-source voltage VDSbecomes −0.3V or less. Therefore, the output signal from the lower MOS VDSdetecting section130changes from a low voltage level (0V) to a high voltage level (5V). Then, when the phase voltage VPbecomes higher than the ground voltage VGNDby 1.0V or more, the drain-source voltage VDSbecomes 1.0V or higher. Therefore, the output signal from the lower MOS VDSdetecting section130changes from a high voltage level to a low voltage level.

A value V11(FIG. 7) that is lower than the ground voltage VGNDby 0.3V, described above, corresponds with the first threshold value. The first threshold value is used to detect, with certainty, the starting point of the diode energization period. The first threshold value is set to a value lower than a value that is the difference of the ground voltage VGNDand the drain-source voltage VDSof the MOS transistor51when the MOS transistor51is turned ON. The first threshold value is also set to a value higher than a value that is the difference of the ground voltage VGNDand the forward voltage VFof the diode connected in parallel with the MOS transistor51. A value V21(FIG. 7) that is 1.0V higher than the output voltage VB, described above, corresponds with the second threshold value. The second threshold value is used to detect, with certainty, the end point of the diode energization period. The second threshold value is set to a value higher than the ground voltage VGND. A period from when the phase voltage VPreaches the first threshold value until the second threshold is reached is an “ON period” of the lower arm. The ON period of the lower arm corresponds with an “energization period” recited in the scope of claims. The starting point and the end point of the ON period are shifted from those of the “diode energization period” when the diode is actually energized while the MOS transistor51is in the OFF state. According to the present embodiment, synchronization control is performed based on this ON period. In addition, the first threshold value (V11) and the second threshold value (V21) corresponding with the lower arm, described above, corresponds with a first threshold value and a second threshold value recited in the scope of claims.

The temperature detecting section150is configured by, for example, a diode disposed near the MOS transistors50and51and the control section100, and an analog-to-digital converter that converts the forward voltage of the diode to digital data. The forward voltage of the diode has temperature dependency. Therefore, the temperature near the MOS transistors50and51and the like can be detected based on the forward voltage. The analog-to-digital converter or the overall temperature detecting section150may be provided within the control section100.

The control section100judges the timing for starting a synchronized rectification operation, sets the ON/OFF-timings of the MOS transistors50and51for performing synchronized rectification, drives the drivers170and172in correspondence with the ON/OFF-timing settings, judges load-dump protection operation transition timing, performs a protection operation, and the like.

FIG. 6is a diagram of a detailed configuration of the control section100. As shown inFIG. 6, the control section100includes a rotation frequency calculator101, a synchronization control start judging section102, an upper MOS ON-timing judging section103, a lower MOS ON-timing judging section104, a target electrical angle setting section105, an upper MOS·TFBtime calculating section106, an upper MOS OFF-timing calculating section107, a lower MOS·TFBtime calculating section108, a lower MOS OFF-timing calculating section109, a load-dump judging section111, and a power source start/stop judging section112. Each of the configurations above are embodied by, for example, a predetermined operation program stored in a memory or the like being loaded and run by a central processing unit (CPU) in synchronization with a clock signal generated by a clock generating circuit. Alternatively, the configurations may be configured by hardware. Specific operations of each configuration will be described hereafter.

The upper MOS ON-timing judging section103and the lower MOS ON-timing judging section104correspond with an “ON-timing setting section”. The target electrical angle setting section105, the upper MOS·TFBtime calculating section106, the upper MOS OFF-timing calculating section107, the lower MOS·TFBtime calculating section108, and the lower MOS OFF-timing calculating section109correspond with an “energization period detector”.

The rectifier module5× and the like according to the present embodiment are configured as described above. Next, operations of the rectifier module5× and the like will be described.

(1) Power Source Start/Stop Judgment

The power source start/stop judging section112monitors the presence of a pulse width modulated (PWM) signal (excitation current) supplied from the F terminal of the power generation control device7to the field winding4. The power source start/stop judging section112instructs the power source160to start when the PWM signal is continuously outputted for 30 μsec. In addition, the power source start/stop judging section112instructs the power source160to stop when the output of the PWM signal is discontinued for one second. In this way, the rectifier module5X and the like start operation when the supply of excitation current to the field winding4is started, and stops operation when the supply of excitation current is stopped. Therefore, as a result of the rectifier module5X and the like being operated only during power generation by the vehicle power generator1, wasteful power consumption can be suppressed.

(2) Synchronization Control Operation

FIG. 7is an operation timing chart for the synchronized rectification control (synchronization control) performed by the control section100. InFIG. 7, an “upper arm ON-period” indicates the output signal from the upper MOS VDSdetecting section120. An “upper MOS ON-period” indicates the ON/OFF-timings of the high-side MOS transistor50. A “lower arm ON-period” indicates the output signal from the lower MOS VDSdetecting section130. A “lower MOS ON-period” indicates the ON/OFF-timings of the low-side MOS transistor51. TFB1, TFB2, target electrical angle, and ΔT will be described hereafter. The synchronization control shown inFIG. 7is performed after the synchronization control start judging section102judges that the timing for starting synchronization control has been reached.

The upper MOS ON-timing judging section103monitors the output signal from the upper MOS VDSdetecting section120(upper arm ON-period). The upper MOS ON-timing judging section103judges the rise of the output signal from a low voltage level to a high voltage level to be the ON-timing of the high-side MOS transistor50. The upper MOS ON-timing judging section103sends an instruction to the driver170. The driver170turns ON the MOS transistor50in adherence to the instruction.

The upper MOS OFF-timing calculating section107judges the elapse of a predetermined amount of time after the MOS transistor50is turned ON to be the OFF-timing of the MOS transistor50. The upper MOS OFF-timing calculating section107sends an instruction to the driver170. The driver170turns OFF the MOS transistor50in adherence to the instruction.

The predetermined amount of time used to decide the OFF-timing is variably set each time such as to be earlier than the end point of the upper arm ON-period (the point at which the output signal from the upper MOS VDSdetecting section120falls from a high voltage level to a low voltage level) by a “target electrical angle”.

The target electrical angle is a margin provided such that, when an instance in which the MOS transistor50is normally turned OFF and rectification is performed through the diode is considered, the OFF-timing of the MOS transistor50is not later than the end point of the energization period in diode rectification. The target electrical angle setting section105sets the target electrical angle. The target electrical angle setting section105sets the target electrical angle based on rotation frequency calculated by the rotation frequency calculator101. The target electrical angle is set to a large value in a low-speed rotation range and a high-speed rotation range. The target electrical angle is set to a small value in an intermediate range between the low-speed rotation range and the high-speed rotation range. The setting of the target electrical angle based on rotation frequency will be described hereafter.

In a similar manner, the lower MOS ON-timing judging section104monitors the output signal from the lower MOS VDSdetecting section130(lower arm ON-period). The lower MOS ON-timing judging section104judges the rise of the output signal from a low voltage level to a high voltage level to be the ON-timing of the low-side MOS transistor51. The lower MOS ON-timing judging section104sends an instruction to the driver172. The driver172turns ON the MOS transistor51in adherence to the instruction.

The lower MOS OFF-timing calculating section109judges the elapse of a predetermined amount of time after the MOS transistor51is turned ON to be the OFF-timing of the MOS transistor51. The lower MOS OFF-timing calculating section109sends an instruction to the driver172. The driver172turns OFF the MOS transistor51in adherence to the instruction.

The predetermined amount of time used to decide the OFF-timing is variably set each time such as to be earlier than the end point of the lower arm. ON-period (the point at which the output signal from the lower MOS VDSdetecting section130falls from a high voltage level to a low voltage level) by a “target electrical angle”.

The target electrical angle is a margin provided such that, when an instance in which the MOS transistor51is normally turned OFF and rectification is performed through the diode is considered, the OFF-timing of the MOS transistor51is not later than the end point of the energization period in diode rectification. The target electrical angle setting section105sets the target electrical angle.

In actuality, the end points of the upper arm ON-period and the lower arm ON-period are unknown at the point at which the MOS transistors50and51are turned OFF. Therefore, the upper MOS OFF-timing calculating section107and the lower MOS OFF-timing calculating section109feed back information from a half-cycle earlier. As a result, the setting accuracy of the OFF-timings of the MOS transistor50and the MOS transistor51is increased.

For example, the OFF-timing of the high-side MOS transistor50is set as follows. The lower MOS TFBtime calculating section108calculates time TFB2(FIG. 7), from when the low-side MOS transistor51is turned OFF until the end point of the lower arm ON-period, from a half-cycle earlier. The upper MOS OFF-timing calculating section107determines ΔT that is the time TFB2subtracted by the target electrical angle. When rotation and the like are stable, the time TFB2and the target angle become equal, and ΔT=0. However, ΔT often does not become zero due to: (A) rotational fluctuations accompanying acceleration of the vehicle, (B) pulsations in the engine rotation, (C) fluctuations in the electrical load, (D) fluctuations in the operating clock cycle when the CPU runs a predetermined program and actualizes the control section100, and (E) a turn-OFF delay between when the drivers170and172are instructed to turn OFF the MOS transistors50and51and when the MOS transistors50and51are actually turned OFF.

Therefore, the upper MOS OFF-timing calculating section107corrects the lower MOS ON-period used by the lower MOS OFF-timing calculating section109a half-cycle earlier based on ΔT and sets the upper MOS ON-period. As a result, the upper MOS OFF-timing calculating section107decides the OFF-timing of the MOS transistor50. Specifically, when a correction coefficient is α, the upper MOS ON-period is set by a following formula.
(upper MOS ON-period)=(lower MOS ON-period from half-cycle earlier)+ΔT×α

In a similar manner, the OFF-timing of the low-side MOS transistor51is set as follows. The upper MOS TFBtime calculating section106calculates time TFB1(FIG. 7), from when the high-side MOS transistor51is turned OFF until the end point of the upper arm ON-period, from a half-cycle earlier. The lower MOS OFF-timing calculating section109determines ΔT that is the time TFB1subtracted by the target electrical angle. The lower MOS OFF-timing calculating section109corrects the upper MOS ON-period used by the upper MOS OFF-timing calculating section107a half-cycle earlier based on ΔT and sets the lower MOS ON-period. As a result, the lower MOS OFF-timing calculating section109decides the OFF-timing of the MOS transistor51. Specifically, when a correction coefficient is α, the lower MOS ON-period is set by a following formula.
(lower MOS ON-period)=(upper MOS ON-period from half-cycle earlier)+ΔT×α

In this way, the high-side MOS transistor50and the low-side MOS transistor51are alternately turned ON at the same cycle as when diode rectification is performed. A low-loss rectification operation using the MOS transistors50and51is performed.

(3) Method of Setting Target Electrical Angle

Next, a method of setting the target electrical angle will be described. The target electrical angle is set to a value based on the rotation frequency. A reason for this is that the value of the target electrical angle (minimum value) required to perform synchronization control such that the timings at which the MOS transistors50and51are turned OFF are not later than the end points of the upper arm ON-period and the lower arm ON-period is dependent on the rotation frequency. Specifically, the value of the required target electrical angle is changed based on the rotation frequency for the same reason ΔT does not become zero due to: (A) rotational fluctuations accompanying acceleration of the vehicle, (B) pulsations in the engine rotation, (C) fluctuations in the electrical load, (D) fluctuations in the operating clock cycle when the CPU runs a predetermined program and actualizes the control section100, and (E) a turn-OFF delay between when the drivers170and172are instructed to turn OFF the MOS transistors50and51and when the MOS transistors50and51are actually turned OFF, as described above regarding the operation for setting the OFF-timings performed by the upper MOS OFF-timing calculating section107and the lower MOS OFF-timing calculating section109.

FIG. 8is a diagram showing the fluctuations in electrical angle when sudden acceleration of the vehicle (sudden increase in rotation frequency) is assumed (corresponding to the instance described in A, above). InFIG. 8, the horizontal axis indicates the rotation frequency of the vehicle power generator1. The vertical axis indicates the electrical angle indicating the extent of fluctuations in the length of the upper arm ON-period and in the length of the lower arm ON-period when rotational fluctuations occur in which the rotation frequency of the vehicle power generator1rises from 2000 rpm to 16000 rpm in one second. The characteristics indicated by the solid line inFIG. 8correspond to when the rotor has eight poles. The characteristics indicated by the dotted line correspond to when the rotor has six poles.

As shown inFIG. 8, the extent of ON-period fluctuations indicated by the electrical angle increases as the rotation frequency decreases. The extent of ON-period fluctuations indicated by the electrical angle decreases as the rotation frequency increases. When these characteristics are reflected, the target electrical angle is required to be set to a larger value, the further the rotation frequency is towards the low-speed rotation range. The target electrical angle is required to be set to a smaller value, the further the rotation frequency is towards the high-speed rotation range.

FIG. 9is a diagram showing the fluctuations in electrical angle when fluctuations in engine rotation of ±40 rpm are assumed (corresponding to the instance described in B, above). InFIG. 9, the horizontal axis indicates the rotation frequency of the vehicle power generator1. The vertical axis indicates the electrical angle indicating the extent of fluctuations in the length of the upper arm ON-period and in the length of the lower arm ON-period when the above-described fluctuations in engine rotation occur, with a pulley ratio of 2.5. The characteristics indicated by the solid line inFIG. 9correspond to when the rotor has eight poles. The characteristics indicated by the dotted line correspond to when the rotor has six poles.

As shown inFIG. 9, the extent of ON-period fluctuations indicated by the electrical angle increases as the rotation frequency decreases. The extent of ON-period fluctuation indicated by the electrical angle decreases as the rotation frequency increases. When these characteristics are reflected, the target electrical angle is required to be set to a larger value, the further the rotation frequency is towards the low-speed rotation range. The target electrical angle is required to be set to a smaller value, the further the rotation frequency is towards the high-speed rotation range.

FIG. 10is a diagram showing the fluctuations in electrical angle when sudden fluctuations in electrical load are assumed (corresponding to the instance described in C, above). InFIG. 10, the horizontal axis indicates the rotation frequency of the vehicle power generator1. The vertical axis indicates the electrical angle indicating the extent of fluctuations in the length of the upper arm ON-period and in the length the lower arm ON-period when an electrical load10of 50 A is cut off and the output voltage VBchanges to 13.5V to 14.0V. The characteristics indicated by the solid line inFIG. 10correspond to when the rotor has eight poles. The characteristics indicated by the dotted line correspond to when the rotor has six poles.

As shown inFIG. 10, the extent of ON-period fluctuations indicated by the electrical angle increases as the rotation frequency decreases. The extent of ON-period fluctuations indicated by the electrical angle decreases as the rotation frequency increases. When these characteristics are reflected, the target electrical angle is required to be set to a larger value, the further the rotation frequency is towards the low-speed rotation range. The target electrical angle is required to be set to a smaller value, the further the rotation frequency is towards the high-speed rotation range.

FIG. 11is a diagram showing the fluctuations in electrical angle when a turn-OFF delay by the drivers170and172is assumed (corresponding to the instance described in E, above). InFIG. 11, the horizontal axis indicates the rotation frequency of the vehicle power generator1. The vertical axis indicates the electrical angle indicating the extent of fluctuations in the length of the upper arm ON-period and in the length of the lower arm ON-period when a turn-OFF delay between when the drivers170and172are respectively given an instruction to turn OFF the MOS transistors50and51and when the MOS transistors50and51are actually turned OFF is 15 μsec. The characteristics indicated by the solid line inFIG. 11correspond to when the rotor has eight poles. The characteristics indicated by the dotted line correspond to when the rotor has six poles.

As shown inFIG. 11, the extent of ON-period fluctuations indicated by the electrical angle decreases as the rotation frequency decreases. The extent of ON-period fluctuations indicated by the electrical angle increases as the rotation frequency increases. When these characteristics are reflected, the target electrical angle is required to be set to a smaller value, the further the rotation frequency is towards the low-speed rotation range. The target electrical angle is required to be set to a larger value, the further the rotation frequency is towards the high-speed rotation range.

In addition to those described above, fluctuations in the clock cycle are also required to be taken into consideration (corresponding to the instance described in D, above). For example, when a 2 MHz system clock is used and its accuracy is ±β%, or in other words, fluctuations of β% occur, the fluctuations in the length of the upper arm ON-period and in the length of the lower arm ON-period increase, the further the rotation frequency is towards the high-speed rotation range. The fluctuations decrease, the further the rotation frequency is towards the low-speed rotation range. A reason for this is that, although the accuracy of the clock is constant regardless of the rotation frequency, the amount of time equivalent to a single electrical angle cycle of the phase voltage VPbecomes shorter, the further the rotation frequency is towards the high-speed rotation range. Therefore, the relative proportion of the clock fluctuation during the ON period increases. When these characteristics are reflected, the target electrical angle is required to be set to a smaller value, the further the rotation frequency is towards the low-speed rotation range. The target electrical angle is required to be set to a larger value, the further the rotation frequency is towards the high-speed rotation range.

FIG. 12is a diagram showing the fluctuations in electrical angle when a combination of the various factors corresponding to the instances in A to E, described above, is assumed. InFIG. 12, the horizontal axis indicates the rotation frequency of the vehicle power generator1. The vertical axis indicates a cumulative value of electrical angle fluctuations corresponding to the various factors. The characteristics S inFIG. 12indicate the cumulative value of electrical angle fluctuations when the rotor has eight poles.

As shown inFIG. 12, when the various factors corresponding to the instances in A to E are combined, the extent of electrical angle fluctuations increases, the further the rotation frequency is towards the high-speed rotation range and the low-speed rotation range. In an intermediate-speed rotation range, the extent of electrical angle fluctuations decreases. The target electrical angle setting section105reflects these characteristics. In other words, the target electrical angle setting section105sets the target electrical angle to a larger value in the low-speed rotation range and the high-speed rotation range. The target electrical angle setting section105sets the target electrical angle to a smaller value in the intermediate-speed rotation range. The two types of characteristics indicated by P and Q inFIG. 12indicate the target electrical angles set in this way. One of the target electrical angles indicated by P is that in which the value continuously changes based on the rotation frequency. In this instance, the minimum value of the target electrical angle can be set based on the rotation frequency. The other of the target electrical angles indicated by Q is that in which the value changes in steps based on the rotation frequency. In this instance, for example, a plurality of values that change based on the rotation frequency are merely required to be stored in table format. Therefore, the configuration required for variably setting the target electrical angle can be simplified.

(4) Specific Example of Rotation Frequency Calculation

Next, a specific example of the rotation frequency calculation performed by the rotation frequency calculator101will be described. The rotation frequency calculator101monitors the output signal from the lower MOS VDSdetecting section130, and calculates the rotation frequency based on the cycle of a start timing of the lower MOS ON-period. The start timing of the lower MOS ON-period is also the ON-timing of the low-side MOS transistor51. Therefore, the rotation frequency calculator10can also be said to calculate the rotation frequency based on the interval of the ON-timing of the low-side MOS transistor51.

FIG. 13is a flowchart of the operation procedures for rotation frequency calculation performed by the rotation frequency calculator101. The operation procedures shown inFIG. 13are repeated at a predetermined cycle sufficiently shorter than the cycle at which the lower arm ON-period is repeated (cycle of the phase voltage).

The rotation frequency calculator101monitors the output signal from the lower MOS VDSdetecting section130. The rotation frequency calculator101judges whether or not the output signal has risen from a low voltage level to a high voltage level and the start timing of the lower arm ON-period has been detected (whether or not the ON-timing of the low-side MOS transistor51has been reached) (Step100). When the start timing of the lower arm ON-period is detected, the rotation frequency calculator101judges YES. Next, the rotation frequency calculator101holds the value of a cycle counter Ct at the present point as a cycle C (Step101). Here, the value of the cycle counter Ct is reset with the start timing of the lower arm ON-period. The value increases by one every time the operation procedures shown inFIG. 13are performed once. At the start timing of the next lower arm ON-period, the value that has increased up to this point is read out. Therefore, “holds the value of a cycle counter Ct at the present point as a cycle C” at Step101refers to reading out the value of the cycle counter Ct that has increased up to the present point at the start timing of the next lower arm ON-period.

Next, the rotation frequency calculator101calculates a rotation frequency N of the vehicle power generator1using the following formula (Step102).
N=K/C,
in which, K represents a coefficient for converting the cycle Ct to a rotation frequency, and has a value that is decided based on the time interval at which the value of the cycle counter Ct increases (the time interval at which the operation procedures inFIG. 13are performed) and the like.

Next, the rotation frequency calculator101resets the cycle counter Ct to zero (Step103) and completes the series of operations related to rotation frequency calculation. On the other hand, when the start timing of the lower arm ON-period is not detected, the rotation frequency calculator101judges NO at Step100. The rotation frequency calculator101updates the value of the cycle counter Ct by adding one (Step104) and completes the series of operations related to rotation frequency calculation. The updating of the value of the cycle counter Ct is repeated at a predetermined cycle until the value of the cycle counter Ct is reset at Step103.

As described above, in the vehicle power generator1according to the present embodiment, one end side (source) of the low-side MOS transistor51is connected to the negative terminal of the battery9via the vehicle body (grounding). Therefore, even when sudden fluctuations in electrical load10occurs, the fluctuations in power generation voltage (phase voltage) are small. The accuracy of rotation frequency calculation can be improved through use of the lower MOS ON-period (specifically, the cycle of the start timing) detected based on the power generation voltage.

In addition, the first threshold value used to set the ON-timing of the low-side MOS transistor51is also used in rotation frequency calculation. Therefore, the lower MOS VDSdetecting section130that performs the comparison operation between the phase voltage and the first threshold value voltage can be commonly used. Processes and configurations can be simplified.

In addition, the upper MOS OFF-timing calculating section107and the lower MOS OFF-timing calculating section109set the OFF-timings of the MOS transistor50and the MOS transistor51based on the rotation frequency calculated by the rotation frequency calculator101. Therefore, synchronization control for turning ON/OFF the MOS transistors50and51can be performed with a simple configuration, without use of a separate component, such as a sensor, for detecting the rotation frequency.

According to the above-described embodiment, the timing at which the rotation frequency calculated using the rotation frequency calculator101is reflected in the OFF-timing settings of the MOS transistors50and51is not described. The OFF-timings are preferably set using the newest rotation frequency information. In other words, the OFF-timing of each MOS transistor50and51included in the subsequent cycle of the phase voltage is preferably set based on the rotation frequency calculated by the rotation frequency calculator101. As a result, highly accurate OFF-control of the MOS transistors50and51can be performed using the newest rotation frequency.

According to the above-described embodiment, the value of the target electrical angle is variably set based on the rotation frequency. However, the value of the target electrical angle may also be set by combining temperature and output current with the rotation frequency.

For example, in general, the fluctuations in the cycle of a clock generated by a clock generator increases as the temperature rises. When an instance in which the clock generator is included within the rectifier module5X and the like is considered, the temperature detected by the temperature detecting section150can be considered to match the temperature of the clock generator. The target electrical angle setting section105sets the target electrical angle to a larger value when the temperature detected by the temperature detecting section150is high and the target electrical angle is increasing in relation to the rotation frequency. The target electrical angle setting section105sets the target electrical angle to a smaller value, the lower the temperature is. As a result of effects attributed to temperature being considered, the target electrical angle can be further set to an appropriate value. Further loss reduction and improvement in power generation efficiency can be achieved.

In general, the larger the output current, the steeper the rise and drop in phase voltage VPis. Conversely, the smaller the output current, the more gradual the rise and drop in phase voltage VPis. As described above, the point at which the upper arm ON-period ends and the timing at which the current flowing to the diode connected in parallel with the MOS transistor50actually stops are shifted. The extent of shifting becomes more noticeable during small output in which the change in phase voltage VPis gradual. The target electrical angle setting section105sets the target electrical angle to a larger value, the smaller the output current is. The target electrical angle setting section105sets the target electrical angle to a smaller value, the larger the output current is. As a result of the effects attributed to changes in output current being considered, the target electrical angle can be further set to an appropriate value. Further loss reduction and improvement in power generation efficiency can be achieved. The size of the output current can be judged by the ON-duty of the PWM signal supplied from the F terminal of the power generation control device7to the field winding4being monitored. Alternatively, the size of the output current may be judged by, for example, a current detection resistor being inserted between the source of the MOS transistor51shown inFIG. 2and the negative terminal (grounding) of the battery9. The judgment is made based on both end voltages of the current detection resistor.

FIG. 14andFIG. 15are diagrams of the configurations of a variation example in which a current detecting section is added and the size of the output current is judged. The configuration shown inFIG. 14is the rectifier module5X shown inFIG. 2to which a current detection resistor55has been added. The configuration shown inFIG. 15is the control circuit54shown inFIG. 3to which an output current detecting section152has been added. The output current detecting section152detects the output current based on both end voltages of the current detection resistor55. In this instance, the size of the output current is judged based on the current value of the current flowing through the MOS transistor51of the rectifier module5X. However, instead, the size of the output current may be judged by the current value of the current flowing through the charging line12or the output terminal being directly detected using a current sensor.

The present invention is not limited to the above-described embodiment. Various modifications can be made without departing from the spirit of the present invention. For example, according to the above-described embodiment, the rotation frequency is calculated based on the cycle of the start timing of the lower MOS ON-period. However, the rotation frequency can be calculated based on the cycle of the end timing of the lower MOS ON-period.

FIG. 16is a flowchart of a variation example of the operation procedures for rotation frequency calculation performed by the rotation frequency calculator101. The operation procedures shown inFIG. 16differ from the operation procedures shown inFIG. 13in that the operation at Step100is replaced with the operation at Step200. At Step200, the rotation frequency calculator101monitors the output signal from the lower MOS VDSdetecting section130. The rotation frequency calculator101judges whether or not the output signal has dropped from a high voltage level to a low voltage level, and an end timing of the lower arm ON-period has been detected. The operations at the other steps are the same as those shown inFIG. 13. The value of the cycle counter Ct is reset at the end timing of the lower arm ON-period. The value is increased by one every time the operation procedures inFIG. 16are performed once. The value that has increased up to the present point is read out at the end timing of the next lower arm ON-period.

In addition, the rotation frequency may be calculated using the cycles of both the start timing and the end timing of the lower MOS ON-period.

FIG. 17is a flowchart of another variation example of the operation procedures for rotation frequency calculation performed by the rotation frequency calculator101. In the operation procedures shown inFIG. 17, a rotation frequency N1is calculated based on the cycle of the start timing of the lower MOS ON-period and a rotation frequency N2is calculated based on the cycle of the end timing, through combination of the operation procedures inFIG. 13and the operation procedures inFIG. 16.

The rotation frequency calculator101monitors the output signal from the lower MOS VDSdetecting section130. The rotation frequency calculator101judges whether or not the start timing of the lower arm ON-period has been detected (Step300). The rotation frequency calculator101also judges whether or not the end timing has been detected (Step304). When the start timing of the lower arm ON-period is detected, the rotation frequency calculator101judges YES at Step300. Next, the rotation frequency calculator101holds the value of a cycle counter CU at this point as a cycle C1(Step301) and calculates the rotation frequency N1of the vehicle power generator1using the following formula (Step302).
N1=K/C1

Next, the rotation frequency calculator101resets the cycle counter Ct1to zero (step303) and completes the series of operations related to rotation frequency calculation.

In addition, when the end timing of the lower arm ON-period is detected, the rotation frequency calculator101judges Yes at Step304. Next, the rotation frequency calculator101holds the value of a cycle counter Ct2at this point as a cycle C2(Step305) and calculates the rotation frequency N2of the vehicle power generator1using the following formula (Step306).
N2=K/C2

Next, the rotation frequency calculator101resets the cycle counter Ct2to zero (step307) and completes the series of operations related to rotation frequency calculation.

When neither the start timing nor the end timing, of the lower arm ON-period is detected, the rotation frequency calculator101judges NO at both Step300and Step304. The rotation frequency calculator101updates the values of the two cycle counters Ct1and Ct2by adding one (Step308and Step309) and completes the series of operations related to rotation frequency calculation. The updating of the value of the cycle counter Ct1is repeatedly performed at a predetermined cycle until the value of the cycle counter Ct1is reset at Step303. The updating of the value of the cycle counter Ct3is repeatedly performed at a predetermined cycle until the value of the cycle counter Ct2is reset at Step307.

In this way, the two types of rotation frequencies N1and N2can be obtained. For example, the OFF-timing setting of the low-side MOS transistor51immediately thereafter is performed using one rotation frequency N1. The OFF-timing setting of the high-side MOS transistor50is performed using the other rotation frequency N2. As a result, OFF-control using the newest rotation frequencies can be performed for the high-side MOS transistor50, as well as for the low-side MOS transistor51.

According to the above-described embodiment, the rotation frequency is calculated by a single cycle of the start timing (or the end timing) of the lower MOS ON-period being measured. However, the rotation frequency can be determined by a plurality of cycles being averaged. For example, with reference to the operation procedures inFIG. 13, using the cycle C held at Step101taken over a plurality of cycles and averaging the cycles C can be considered. Alternatively, using the rotation frequency N calculated at Step102taken over a plurality of cycles and averaging the rotation frequencies N can be considered. As a result, the rotation frequency can be stably set even when rotational fluctuations occur.

In the descriptions referencingFIG. 13,FIG. 16, andFIG. 17, the values of the cycle counters Ct, Ct1, and Ct2are increased by one every time the operation procedures shown in the drawings are repeated at a predetermined cycle. However, the operation may be actualized using a counter configured by hardware. In this instance, the counter is counted upwards in synchronization with a predetermined clock signal. When the start timing and the end timing of the lower MOS ON-period are detected, the counter value can be read out and the counter can be reset.

According to the above-described embodiment, rotation frequency calculation is performed based on at least one of the cycle of the start timing and the cycle of the end timing of the lower MOS ON-period. However, rotation frequency calculation may be performed based on the cycle of a timing related to the lower MOS ON-period other than the start timing and the end timing. For example, rotation frequency calculation may be performed based on a cycle of a point at which a predetermined amount of time has elapsed form the start timing of the lower MOS ON-period. In this instance as well, in a manner similar to that when the cycle of the start timing or the cycle of the end timing is used, the accuracy of rotation frequency calculation can be improved.

According to the above-described embodiment, at Step102inFIG. 13, at Step102inFIG. 16, and at Step302and Step306inFIG. 17, the rotation frequency calculator101determines the rotation frequency using a predetermined formula (such as N=K/C). However, the relationship between the cycle C and the rotation frequency N can be held in map format or table format. When the cycle C is obtained, the corresponding rotation frequency N can be determined by referencing the map or table.

According to the above-described embodiment, the target electrical angle setting section105may increase the value of the target electrical angle when the frequency of instances in which the timings at which the MOS transistors50and51are turned OFF are later than the timing at which the energization period (upper arm ON-period and lower arm ON-period) ends increases. As a result, even when a state in which the timings at which the MOS transistors50and51are turned OFF are later than the energization period frequently occurs for whatever reason, control can be changed such that the MOS transistors50and51are turned OFF before the energization period ends.

According to the above-described embodiment, an instance in which the target electrical angle is set to a larger value in the low-speed rotation range and the high-speed rotation range, and to a smaller value in the intermediate-speed rotation range is described. However, the target electrical angle may be variably set with focus on the relationship between the low-speed rotation range and the high-speed rotation range, or with focus on the relationship between the intermediate-speed rotation range and the high-speed rotation range.

Specifically, when the rotation frequency is divided into the low-speed rotation range, the intermediate-speed rotation range, and the high-speed rotation range, the target electrical angle setting section105sets the target electrical angle to a larger value when the rotation frequency calculated by the rotation frequency calculator101is in the low-speed rotation range. The target electrical angle setting section105sets the target electrical angle to a smaller value when the rotation frequency is in the intermediate-speed rotation range. As a result, the appropriate value of the target electrical angle can be set for each rotation frequency in the range up to the intermediate-speed rotation range. Loss reduction and improvement in power generation efficiency can be achieved in the range up to the intermediate-speed rotation range. In this instance, the target electrical angle in the high-speed rotation range may be increased with the increase in rotation frequency, in a manner similar to that according to the above-described embodiment (FIG. 12). Alternatively, the target electrical angle may be held constant.

Alternatively, when the rotation frequency is divided into the low-speed rotation range, the intermediate-speed rotation range, and the high-speed rotation range, the target electrical angle setting section105preferably sets the target electrical angle to a larger value when the rotation frequency calculated by the rotation frequency calculator101is in the high-speed rotation range. The target electrical angle setting section105preferably sets the target electrical angle to a smaller value when the rotation frequency is in the intermediate-speed rotation range. As a result, the appropriate value of the target electrical angle can be set for each rotation frequency in the range from intermediate-speed rotation range and higher. Loss reduction and improvement in power generation efficiency can be achieved in the range from the intermediate-speed rotation range and higher. In this instance, the target electrical angle in the low-speed rotation range may be increased with the decrease in rotation frequency, in a manner similar to that according to the above-described embodiment (FIG. 12). Alternatively, the target electrical angle may be held constant.

According to the above-described embodiment, two stator windings2and3, and two rectifier module groups5and6are included. However, the present invention can be applied to a vehicle power generator including one stator winding2and one rectifier module group5.

According to the above-described embodiment, an instance in which the rectification operation (power generation operation) is performed using each rectifier module5X and the like is described. However, the present invention can be applied to an rotary electric machine for a vehicle that performs motor operation by converting a direct current applied from the battery9to an alternating current and supplying the alternating current to the stator windings2and3, by changing the ON/OFF timings of the MOS transistors50and51.

According to the above-described embodiment, the two rectifier module groups5and6each include three rectifier modules. However, the number of rectifier modules may be other than three.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

INDUSTRIAL APPLICABILITY

As described above, the present invention is capable of securing a period in which current flows to the diode after the MOS transistors50and51are turned OFF and shortening this period, by variably setting the value of the target electrical angle based on the rotation frequency. Therefore, loss occurring as a result of diode rectification can be reduced, and power generation efficiency can be improved.