Motor, rotation period detection method thereof, motor rotation period detection sensor assembly, and power generator

A motor which is capable of realizing further space saving and cost reduction. A cylindrical outer rotor 11 is rotatable around a central axis CL thereof. A plurality of magnets 13 are arranged at equal intervals on an inner circumferential surface of the outer rotor 11. Three Hall elements 15 to 17 are arranged to oppose the respective magnets 13 and detect switching of magnetic poles caused by movement of the respective magnets 13 passing through each vicinity of the Hall elements 15 to 17 when the outer rotor 11 rotates. The Hall element 17 is comprised of a linear Hall element that outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the respective magnets 13. One of the respective magnets 13 is arranged offset along the central axis CL as compared to the other magnets 13.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a motor, a rotation period detection method thereof, a motor rotation period detection sensor assembly, and a power generator, and particularly to a three-phase brushless motor and a rotation period detection method thereof.

Description of the Related Art

Recently, a driving motor served also as a power generator often applied to vehicles or motorcycles. A three-phase brushless motor is often used as the driving motor. The three-phase brushless motor is provided with a cylindrical outer rotor160of which one end is opened, a plurality of stators161which are housed inside the outer rotor160and radially protrude from a central axis of the outer rotor160, and a plurality of magnets162which are arranged at equal intervals on an inner circumferential surface of the outer rotor160as illustrated inFIG. 16. The plurality of magnets162have alternately different magnetic poles.

It is necessary to apply three-phase AC voltages to each coil of the stators161in order to cause the three-phase brushless motor to function as the driving motor, and thus, three phases (a U-phase, a V-phase, and a W-phase) in the three-phase brushless motor are detected, and used for converting, for example, a voltage applied from a battery into the three-phase AC voltages. To correspond to this, three pulsed Hall elements163are arranged among the respective stators161corresponding to the U-phase, the V-phase, and the W-phase, respectively, in the three-phase brushless motor, and each of the pulsed Hall elements163outputs each switching timing of the magnetic pole of the U-phase, the V-phase, and the W-phase of each of the magnets162relatively moving with respect to each of the pulsed Hall elements163as a pulsed signal.

In addition, in the three-phase brushless motor, the outer rotor160is connected with a crankshaft and thus, an ignition period of an engine which matches with a rotation period of the crankshaft can be detected. The ignition period of the engine needs to be detected once per single rotation of the outer rotor160, and thus, is different from each period of the three phases. Thus, one rotation period detecting magnet164is provided on, for example, an outer circumferential surface of the outer rotor160, a pulsed Hall element165for detection of the rotation period is provided to oppose the rotation period detecting magnet164, and the pulsed Hall element165detects a change of a magnetic flux density caused by the rotation period detecting magnet164, thereby outputting the rotation period of the outer rotor160as a pulsed signal.

Meanwhile, the rotation period detecting magnet164is provided separately from the magnets162are in order to detect individually the ignition period of the engine in the above-described three-phase brushless motor, but a three-phase brushless motor, which abolishes the rotation period detecting magnet164has been proposed in order to realize reduction in the number of parts for cost reduction and space saving. In such a three-phase brushless motor, not only the pulsed Hall elements163for detection of the three phases but also the pulsed Hall element165for detection of the rotation period is also arranged among the respective stators161as illustrated inFIG. 17. At this time, only the pulsed Hall element165is arranged offset in the central-axis direction of the outer rotor160, and one of the magnets162is arranged offset in the opposite direction of the pulsed Hall element165as illustrated inFIG. 18. To be specific, a relative movement trajectory (indicated by the broken line inFIG. 18) of the pulsed Hall element165with respect to each of the magnets162opposes the respective magnets162except for the offset magnet162, while respective relative movement trajectories (indicated by the alternate long and short dash line inFIG. 18) of the pulsed Hall elements163with respect to each of the magnets162oppose all the magnets162. Accordingly, each of the pulsed Hall elements163for detection of the three phases is capable of detecting the switching of the magnetic pole caused by movement of the all magnets162including the offset magnet162without missing, but the pulsed Hall element165is difficult to detect the switching of the magnetic pole caused by the offset magnet162. As a result, each of the pulsed Hall elements163outputs a pulsed signal that covers the switching of the magnetic poles of the three phases caused by the all magnets162including the offset magnet162without missing as illustrated inFIG. 19, while the pulsed Hall element165merely outputs a pulsed signal which lacks the switching of the magnetic pole caused by the offset magnet162. That is, apart lacking the switching of the magnetic pole of the pulsed signal output from the pulsed Hall element165corresponds to the timing at which the pulsed Hall element165just opposes the offset magnet162, and thus, the part lacking the switching of the magnetic pole of the pulsed signal of the pulsed Hall element165is detected with reference to the switching of the magnetic pole of the three phases, thereby detecting the rotation period of the outer rotor160, that is, the ignition period of the engine. Although the number of the pulsed Hall elements163for detection of the three phases is different from the example mentioned above, a power generation device for a vehicle, which is an example of such a three-phase brushless motor in which one magnet is provided to be offset detecting an ignition period of an engine, is described in Japanese Patent No. 4766563.

However, the three-phase brushless motor illustrated inFIGS. 16 and 17requires the pulsed Hall element for detection of the rotation period in addition to the pulsed Hall elements163for detection of the three phases, that is, requires the four pulsed Hall elements, and thus, it is difficult to realize further space saving and cost reduction.

SUMMARY OF THE INVENTION

The invention provides a motor, a rotation period detection method thereof, a motor rotation period detection sensor assembly, and a power generator capable of realizing further space saving and cost reduction.

Accordingly, a first aspect of the invention provides a motor which includes a cylindrical outer rotor that is rotatable around a central axis thereof, a plurality of magnets that are arranged at equal intervals on an inner circumferential surface of the outer rotor, a plurality of stators that are housed inside the outer rotor and radially protrude from the central axis, and three Hall elements that are arranged to oppose the plurality of magnets, and in which the three Hall elements detect switching of magnetic poles caused by movement of the plurality of magnets passing through each vicinity of the Hall elements when the outer rotor rotates, at least one of the Hall elements is comprised of a linear Hall element which outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the plurality of magnets, and at least one of the magnets is comprised of an offset magnet which is arranged offset along the central axis as compared to the other magnets.

Accordingly, a second aspect of the invention provides a motor which includes a cylindrical outer rotor that is rotatable around a central axis thereof, a plurality of magnets that are arranged at equal intervals on an inner circumferential surface of the outer rotor, a plurality of stators that are housed inside the outer rotor and radially protrude from the central axis, and three Hall elements that are arranged to oppose the plurality of magnets, and in which the three Hall elements detect switching of magnetic poles caused by movement of the plurality of magnets passing through each vicinity of the Hall elements when the outer rotor rotates, at least one of the Hall elements is comprised of a linear Hall element which outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the plurality of magnets, and an absolute value of a magnetic force of at least one of the magnets is set to be larger than an absolute value of each magnetic force of the other magnets.

Accordingly, a third aspect of the invention provides a method of detecting a rotation period of a motor which includes a cylindrical outer rotor that is rotatable around a central axis thereof, a plurality of magnets that are arranged at equal intervals on an inner circumferential surface of the outer rotor, a plurality of stators that are housed inside the outer rotor and radially protrude from the central axis, and three Hall elements that are arranged to oppose the plurality of magnets, and in which the three Hall elements detect switching of magnetic poles caused by movement of the plurality of magnets passing through each vicinity of the Hall elements when the outer rotor rotates, at least one of the Hall elements is comprised of a linear Hall element which outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the plurality of magnets, and at least one of the magnets is comprised of an offset magnet which is arranged offset along the central axis as compared to the other magnets, the method of detecting the rotation period of the motor including analyzing the linear signal representing the linear change of the magnetic flux density using two thresholds.

Accordingly, a fourth aspect of the invention provides a sensor assembly applied to a motor which includes a cylindrical outer rotor that is rotatable around a central axis thereof, a plurality of magnets that are arranged at equal intervals on an inner circumferential surface of the outer rotor, and a plurality of stators that are housed inside the outer rotor and radially protrude from the central axis, and in which at least one of the magnets is comprised of an offset magnet which is arranged offset along the central axis as compared to the other magnets, the sensor assembly including three Hall elements that are arranged to oppose the plurality of magnets, and an analysis circuit that includes two comparators, in which the three Hall elements detect switching of magnetic poles caused by movement of the plurality of magnets when the outer rotor rotates, at least one of the Hall elements is comprised of a linear Hall element that outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the plurality of magnets, the two comparators are connected to the linear Hall element, the linear signal representing the linear change of the magnetic flux density and a threshold are input to each of the comparators, the respective thresholds input to the respective comparators are different from one another, and the analysis circuit analyzes the linear signal representing the linear change of the magnetic flux density using the respective thresholds.

Accordingly, a fifth aspect of the invention provides a power generator which includes a cylindrical outer rotor that is rotatable around a central axis thereof, a plurality of magnets that are arranged at equal intervals on an inner circumferential surface of the outer rotor, a plurality of stators that are housed inside the outer rotor and radially protrude from the central axis, and three Hall elements that are arranged to oppose the plurality of magnets, and in which the three Hall elements detect switching of magnetic poles caused by movement of the plurality of magnets passing through each vicinity of the Hall elements when the outer rotor rotates, at least one of the Hall elements is comprised of a linear Hall element that outputs a linear signal representing a linear change of a magnetic flux density caused by movement of the plurality of magnets, and at least one of the magnets is comprised of an offset magnet that is arranged offset along the central axis as compared to the other magnets.

According to the invention, the at least one Hall element of the three Hall elements arranged to oppose the plurality of magnets is comprised of the linear Hall element that outputs the linear signal representing the linear change of the magnetic flux density caused by movement of the plurality of magnets, and the at least one magnet is comprised of the offset magnet arranged offset along the central axis of the cylindrical outer rotor as compared to the other magnets. That is, a distance from the offset magnet to the linear Hall element when the offset magnet passes through the vicinity of the linear Hall element is different from distance from each of the other magnets to the linear Hall element when each of the other magnets passes through the vicinity of the linear Hall element. Alternatively, the absolute value of the magnetic force of the at least one magnet is set to be larger than the absolute value of each magnetic force of the other magnets. As a result, an change status of the magnetic flux density caused by the movement of the offset magnet or an change status of the magnetic flux density caused by the movement of the magnet, which is set to have the large absolute value in the magnetic force detected by the linear Hall element is different from an change status of the magnetic flux density caused by the movement of the other magnets, and appears as a specific point in the change status in the linear signal representing the linear change of the magnetic flux density. Therefore, when the specific point of the change status in the linear signal representing the linear change of the magnetic flux density is detected, it is possible to detect a timing at which the offset magnet or the magnet set to have the large absolute value in the magnetic force passes through the vicinity of the linear Hall element. Herein, each rotation period of the offset magnet or the magnet set to have the large absolute value in the magnetic force is nothing but a rotation period of the outer rotor, and thus, in this invention, it is possible to detect the rotation period of the outer rotor as well as to detect the switching of the magnetic poles (of three phases) caused by the movement of the plurality of magnets in the three Hall elements. As a result, it is possible to realize further space saving and cost reduction.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is an exploded perspective view showing main components of a motor according to the embodiment, andFIG. 2is a perspective view of an outer rotor inFIG. 1.

InFIG. 1, a motor10is comprised of a three-phase brushless motor, and is provided with a cylindrical outer rotor11of which one end is opened, a plurality of stators12which are housed inside the outer rotor11and radially protrude from a central axis CL of the outer rotor11, and a plurality of magnets13which are arranged at equal intervals on the inner circumferential surface of the outer rotor11.

Each of the stators12is formed of a stator core which is an iron core and a coil wound around the stator core, and erects outwardly from the rim of an annular base14arranged coaxially with the central axis CL of the outer rotor11. The base14is fixed to an engine body structure (not shown), for example, a cylinder block.

The outer rotor11is engaged with a crankshaft (not shown) which is a shaft arranged along the central axis CL, and rotates together with the crankshaft. The respective magnets13are form of magnet plates each having a substantially rectangular shape, and have alternately different magnetic poles on the inner circumferential surface of the outer rotor11with regard to a circumferential direction of the outer rotor11.

In the motor10, the outer rotor11is rotationally driven by an electromagnetic force when three-phase AC voltages are applied to each coil of the plurality of stators12, thereby generating a rotational torque of the crankshaft. Meanwhile, the coils of the plurality of stators12are caused to generate current through electromagnetic induction when the outer rotor11is rotated by the crankshaft, thereby generating electric power.

In addition, the motor10is provided with three Hall elements15to17which are arranged among the respective stators12to oppose the respective magnets13. When the outer rotor11rotates, each of the magnets13passes through the vicinity of each of the Hall elements15to17, each magnetic flux density detected by the Hall elements15to17is periodically changed since the respective magnets13have alternately different magnetic poles as described above. Each of the Hall elements15and16is comprised of a pulsed Hall element, and outputs a switching timing of the magnetic pole in the detected magnetic flux density as a pulsed signal. The Hall element17is comprised of a linear Hall element, and outputs a signal which represents a linear change of the detected magnetic flux density. The respective Hall elements15to17are arranged to be separated from each other in order to detect changes during respective single period of the magnetic flux densities generated by the same pair of13in a shifted manner each by 120°. To be specific, the Hall element15detects a V-phase, the Hall element16detects a W-phase, and the Hall element17detects a U-phase.

FIG. 3is a diagram indicating arrangement of the respective magnets13and an arrangement of the respective Hall elements15to17when the inner circumferential surface of the outer rotor11is viewed from the central axis CL of the outer rotor11with the open end side of the outer rotor11as the top.

InFIG. 3, among the respective magnets13, one of the S-pole magnets13is arranged offset toward the open end side of the outer rotor11(the upper side inFIG. 3) in relation to a direction along the central axis CL (hereinafter, referred to as a “central-axis direction”) as compared to the other magnets13. It should be noted that the magnet13arranged offset toward the open end side of the outer rotor11will be referred to as the “offset magnet13”, hereinafter. Since the single offset magnet13is present, the timing of the change of the magnetic flux density, caused by the movement of the offset magnet13, and the rotation period of the outer rotor11match each other when the outer rotor11rotates. Therefore, it is possible to detect the rotation period of the outer rotor11by detecting the timing of the change of the magnetic flux density caused by the movement of the offset magnet13.

In addition, the Hall elements15and16are arranged at the same position in relation to the central-axis direction, but the Hall element17is arranged offset toward the open end side of the outer rotor11as compared to the Hall elements15and16, and arranged to be separated from the non-offset magnets13(hereinafter, referred to as the “other magnets13”) farther than the Hall elements15and16in relation to the central-axis direction. That is, the offset magnet13and the Hall element17are offset toward the same open end side of the outer rotor11, and thus, the Hall element17is closer to the offset magnet13than the Hall elements15and16, and the offset magnet13is closer to the Hall element17than the other magnets13. To be specific, when the outer rotor11rotates, a relative movement trajectory (indicated by the alternate long and short dash line inFIG. 3) drawn by the Hall elements15and16with respect to the moving respective magnets13opposes all the magnets13while a relative movement trajectory (indicated by the broken line inFIG. 3) drawn by the Hall element17with respect to the moving respective magnets13opposes only the offset magnet13and does not oppose the other magnets13. It should be noted that a magnetic flux collecting plate18is arranged between each of the Hall elements15to17as shown inFIG. 4, and each of the corresponding magnets13, thereby improving the detection sensitivity of the magnetic flux densities according to the respective Hall elements15to17.

FIG. 5is a diagram indicating signals output from the Hall elements15to17inFIG. 3.

InFIG. 5, the Hall element15outputs the switching timing of the magnetic pole of the V-phase as a pulsed signal, and the Hall element16outputs the switching timing of the magnetic pole of the W-phase as a pulsed signal when the outer rotor11rotates.

On the other hand, the Hall element17outputs a linear signal representing the linear change of the magnetic flux density caused by the movement of each of the magnets13(hereinafter, referred simply to as a “linear signal”). A distance from each of the other magnets13to the Hall element17is not changed when the other magnets13pass through the vicinity of the Hall element17, and thus, an absolute value of a magnetic flux density detected by the Hall element17is not changed. On the other hand, a distance from the offset magnet13to the Hall element17when the offset magnet13passes through the vicinity of the Hall element17is shorter than the distance from each of the other magnets13to the Hall element17when each of the other magnets13passes through the vicinity of the Hall element17, and thus, an absolute value of a magnetic flux density (hereinafter, referred to as the “magnetic flux density of the offset magnet13”) detected by the Hall element17when the offset magnet13passes through the vicinity of the Hall element17is larger than the absolute value of the magnetic flux density (hereinafter, referred to as the “magnetic flux density of the other magnets13”) detected by the Hall element17when each of the other magnets13passes through the vicinity of the Hall element17.

To correspond to this, the switching timing of the magnetic pole of the U-phase and the rotation period of the outer rotor11are detected from the linear signal using two thresholds. To be specific, a value (hereinafter, referred to as a “U-phase threshold”) (indicated by the alternate long and short dash line inFIG. 5), which is smaller than both the absolute value of the magnetic flux density caused by the other magnets13, and the absolute value of the magnetic flux density caused by the offset magnet13, for example, a zero-level value is set as the threshold for detection of the switching timing of the magnetic pole of the U-phase. In addition, a value (hereinafter, referred to as a “rotation threshold”) (indicated by the broken line inFIG. 5), which is larger than the absolute value of the magnetic flux density caused by the other magnets13and is smaller than the absolute value of the magnetic flux density caused by the offset magnet13, is set as the threshold for detection of the rotation period of the outer rotor11.

When the linear signal rises or drops, the linear signal exceeds or falls below the U-phase threshold as long as the magnetic pole of the magnetic flux density detected by the Hall element17is switched, and thus, the timing at which the linear signal exceeds or falls below the U-phase threshold is considered as the timing at which the magnetic pole of the magnetic flux density detected by the Hall element17is switched, that is, the switching timing of the magnetic pole of the U-phase in the embodiment. In addition, the absolute value of the magnetic flux density caused by the offset magnet13is larger than the absolute value of the magnetic flux density caused by the other magnets13as described above, and thus, a timing at which the linear signal exceeds the rotation threshold is considered as a timing at which the offset magnet13passes through the vicinity of the Hall element17, that is, the rotation period in the embodiment.

In the motor10, the switching timing of the magnetic pole of the U-phase and the rotation period are detected based on the linear signal by an analysis circuit19to be described later.

FIG. 6is a circuit diagram showing a configuration of the analysis circuit19provided in the motor10.

InFIG. 6, the analysis circuit19includes the Hall elements15to17and two comparators20and21which are connected, respectively, to an output end of the Hall element17. The Hall elements15and16output the switching timings of the magnetic poles of the V-phase and the W-phase as the pulsed signals. On the other hand, the Hall element17outputs the linear signal, the U-phase threshold and the output linear signal are input to the comparator20, the comparator20outputs, for example, zero when the linear signal exceeds the U-phase threshold, and outputs, for example, one when the linear signal falls below the U-phase threshold. That is, the comparator20outputs the switching timing of the magnetic pole of the U-phase, which is the timing at which the linear signal exceeds or falls below the U-phase threshold, as the pulsed signal. The rotation threshold and the linear signal are input to the comparator21, and the comparator21outputs, for example, one when the linear signal exceeds the rotation threshold, and outputs, for example, zero when the linear signal falls below the rotation threshold. That is, the comparator21outputs the rotation period which is the timing at which the linear signal exceeds the rotation threshold as the pulsed signal. It should be noted that the analysis circuit19is provided in a base plate23of a sensor assembly22in the embodiment to be described later.

In addition, the Hall elements15to17are assembled on consideration of assembling workability and the like in the motor10.

FIG. 7is a perspective view schematically showing a configuration of the sensor assembly which includes the Hall elements15to17. The upper side ofFIG. 7is the open end side of the outer rotor11, and the vertical direction ofFIG. 7matches the central-axis direction.

InFIG. 7, the sensor assembly22is arranged along or horizontally with respect to the central-axis direction, and includes the base plate23, which is arranged on the open end side of the outer rotor11than each of the stators12, and the Hall elements15to17which protrude from the base plate23toward the opposite side to the open end side of the outer rotor11. The Hall elements15to17intrude between the respective stators12(not shown) and oppose the respective magnets13. A protruding amount of the Hall element17from the base plate23is smaller than each protruding amount of the Hall elements15and16from the base plate23, and thus, the Hall element17is arranged offset toward the open end side of the outer rotor11as compared to the Hall elements15and16.

According to the motor10, when the outer rotor11rotates, the linear signal of the Hall element17is analyzed by the analysis circuit19, and the analysis circuit19using the two comparators20and21detects the timing at which the linear signal exceeds or falls below the U-phase threshold and outputs the detected timing as the switching timing of the magnetic pole of the U-phase in the pulsed signal as well as detects the timing at which the linear signal exceeds the rotation threshold and outputs the detected timing as the rotation period in the pulsed signal. That is, it is possible to detect both the switching timing of the magnetic pole of the U-phase and the rotation period using the single Hall element17. As a result, it is possible to detect the switching timings of magnetic poles of the U-phase, the V-phase, and the W-phase and the rotation period using the three Hall elements15to17, and hence it is possible to reduce the number of the Hall elements. In addition, it is possible to reduce a size of the base plate23for attachment of the respective Hall elements also in the sensor assembly22. Accordingly, it is possible to realize further space saving and cost reduction.

In the motor10, the offset magnet13is closer to the Hall element17than the other magnets13, and the Hall element17is closer to the offset magnet13than the Hall elements15and16. Further, the Hall element17is arranged to be separated from the other magnets13in relation to the central-axis direction farther than the Hall elements15and16. Accordingly, the absolute value of the magnetic flux density caused by the offset magnet13detected by the Hall element17is reliably larger than the absolute value of the magnetic flux density caused by the other magnets13detected by the Hall element17. As a result, it is possible to reliably detect the timing at which each of the offset magnets13passes through the vicinity of the Hall element17, that is, the rotation period.

Since the pulsed Hall element is likely to cause a waveform breakage or timing (duty) disturbance by being affected by noise, it is not possible to accurately detect the rotation period when the pulsed Hall element is used for detection of the rotation period. In particular, when the rotation period is shifted in a case in which the detected rotation period is used for ignition control of the engine, such a shift influences badly on the advancing and retarding control of ignition timing. On the contrary, the linear Hall element is used for detection of the rotation period in the motor10. In general, noise generated in the linear signal is likely to be detected as an abnormal value (for example, a local peak value or an unnatural inflection point) when the linear Hall element outputs the linear signal, it is preferable to perform a process of removing the noise on the linear signal, and it is possible to remove the noise by, for example, providing feedback resistors arranged to be parallel, respectively, to the comparators20and21in the analysis circuit19ofFIG. 6, causing the comparators20and21to perform hysteresis operation, and performing a process of removing the abnormal value on the linear signal prior to forming the output waveform of the comparators20and21.

As above, the invention has been described using the above-described embodiment, but the invention is not limited to the above-described embodiment.

For example, the magnet13may be arranged offset toward the opposite side to the open end side of the outer rotor11although the magnet13is arranged offset toward the open end side of the outer rotor11in the above-described motor10.

FIG. 8is a diagram indicating arrangement of the respective magnets13and arrangement of the respective Hall elements15to17when the inner circumferential surface of the outer rotor11is viewed from the central axis CL of the outer rotor11in a motor according to a first variation of the embodiment.

InFIG. 8, among the respective magnets13, the one S-pole magnet13is arranged offset toward the opposite side to the open end side of the outer rotor11in relation to the central-axis direction as compared to the other magnets13, and as a result, the offset magnet13is distant from the Hall element17farther than the other magnets13. It should be noted that the magnet13that is arranged offset toward the opposite side to the open end side of the outer rotor11will be referred to as a “second offset magnet13” hereinafter.

FIG. 9is a diagram indicating signals output by the respective Hall elements15to17inFIG. 8.

InFIG. 9, a distance from the second offset magnet13to the Hall element17when the second offset magnet13passes through the vicinity of the Hall element17is longer than a distance from each of the other magnets13to the Hall element17when each of the other magnets13passes through the vicinity of the Hall element17, and thus, an absolute value of a magnetic flux density which is detected by the Hall element17when the second offset magnet13passes through the vicinity of the Hall element17(hereinafter, referred to as “the magnetic flux density of the second offset magnet13”) is smaller than the absolute value of the magnetic flux density caused by the other magnets13.

To correspond to this, the same U-phase threshold (indicated by the alternate long and short dash line inFIG. 9) as inFIG. 5, for example, the zero-level value is set as a threshold for detection of the switching timing of the magnetic pole of the U-phase, and a value (hereinafter, referred to as referred to as a “second rotation threshold”) (indicated by the broken line inFIG. 9), which is smaller than the absolute value of the magnetic flux density caused by the other magnets13and is larger than the absolute value of the magnetic flux density caused by the second offset magnet13is set as a threshold for detection of the rotation period of the outer rotor11in the first variation.

Similarly toFIG. 5, the timing at which the linear signal exceeds or falls below the U-phase threshold is considered as the switching timing at which the magnetic pole of the magnetic flux density detected by the Hall element17, that is, the switching timing of the magnetic pole of the U-phase in the first variation. In addition, the absolute value of the magnetic flux density caused by the second offset magnet13is larger than the U-phase threshold of the zero-level, but is smaller than the absolute value of the magnetic flux density caused by the other magnets13as described above. Therefore, there is no case in which the linear signal corresponding to the magnetic flux density caused by the second offset magnet13exceeds the second rotation threshold. Here, the comparator21outputs a pulsed signal lacking one pulse as compared to a pulsed signal output by the comparator20in a single rotation of the outer rotor11when the second rotation threshold is input to the comparator21of the analysis circuit19shown inFIG. 6. Thus, it is possible to detect the rotation period of the outer rotor11by comparing the pulsed signals of the U-phase, the V-phase, and the W-phase and the pulsed signal output by the comparator21so as to logically fix a period “A” shown inFIG. 9.

In addition, for example, a plurality of the offset magnets13may be provided to offset in the central-axis direction although only one of the offset magnets13is provided to offset in the above-described motor10.

FIG. 10is a diagram indicating arrangement of the respective magnets13and arrangement of the respective Hall elements15to17when the inner circumferential surface of the outer rotor11is viewed from the central axis CL of the outer rotor11in a motor according to a second variation of the embodiment.

InFIG. 10, among the respective magnets13, two of the magnets13are arranged offset toward the open end side of the outer rotor11in relation to the central-axis direction as compared to the other magnets13, and as a result, the two offset magnets13are closer to the Hall element17than the other magnets13.

FIG. 11is a indicating signals output by the respective Hall elements15to17inFIG. 10.

InFIG. 11, a distance from each of the two offset magnets13to the Hall element17when each of the two offset magnets13passes through the vicinity of the Hall element17is shorter than the distance from each of the other magnets13to the Hall element17when each of the other magnets13pass through the vicinity of the Hall element17, and thus, the absolute value of the magnetic flux density of each of the two offset magnets13is larger than the absolute value of the magnetic flux density caused by the other magnets13similarly toFIG. 5.

To correspond to this, the same U-phase threshold (indicated by the alternate long and short dash line inFIG. 11) as inFIG. 5, for example, the zero-level value is set as a threshold for detection of the switching timing of the magnetic pole of the U-phase, and the same rotation threshold (indicated by the broken line inFIG. 11) as inFIG. 5is set as a threshold for detection of the rotation period of the outer rotor11in the second variation.

Similarly toFIG. 5, a timing at which the linear signal exceeds or falls below the U-phase threshold is considered as the switching timing at which the magnetic pole of the magnetic flux density detected by the Hall element17, that is, the switching timing of the magnetic pole of the U-phase in the second variation. In addition, the timing at which the linear signal exceeds the rotation threshold is considered as a timing at which each of the two offset magnets13passes through the vicinity of the Hall element17, that is, a rotation period similarly toFIG. 5. Accordingly, it is possible to detect both the switching timing of the magnetic pole of the U-phase and the rotation period using the single Hall element17.

In addition, the magnetic flux density of each of the two offset magnets13changes when each of the two offset magnets13passes through the vicinity of the Hall element17, and thus, the linear signal includes two different timings at which each absolute value of the magnetic flux densities caused by the respective two offset magnet13is larger than the absolute value of the magnetic flux density caused by the other magnets13corresponding to the timing at which each of the two offset magnets13passes through the vicinity of the Hall element17. Therefore, it is possible to detect each rotation period of the two offset magnets13, that is, two rotation periods at different timings using the single Hall element17by detecting the timing at which the linear signal exceeds the rotation threshold.

Further, each offset amount of a third offset magnet13and a fourth offset magnet13may be set to different in the case of providing the plurality of (two) magnets13to be offset in the central-axis direction.

FIG. 12is a diagram indicating arrangement of the respective magnets13and arrangement of the respective Hall elements15to17when the inner circumferential surface of the outer rotor11is viewed from the central axis CL of the outer rotor11in a motor according to a third variation of the embodiment.

InFIG. 12, among the respective magnets13, the two magnets13are arranged offset toward the open end side of the outer rotor11in relation to the central-axis direction as compared to the other magnets13, and as a result, the two offset magnets13are closer to the Hall element17than the other magnets13. In addition, each offset amount of the two offset magnets13toward the open end side is different. Hereinafter, the offset magnet13which is offset the closest to the open end side will be referred to as the “the third offset magnet13”, and the offset magnet13which is positioned at the opposite side of the open end side than the third offset magnet13will be referred to as the “fourth offset magnet13”.

FIG. 13is a indicating signals output by the respective Hall elements15to17inFIG. 12.

InFIG. 13, a distance from each of the third offset magnet13and the fourth offset magnet13to the Hall element17when each of the third offset magnet13and the fourth offset magnet13passes through the vicinity of the Hall element17is shorter than the distance from each of the other magnets13to the Hall element17when each of the other magnets13pass through the vicinity of the Hall element17, and thus, an absolute value of a magnetic flux density which is detected by the Hall element17when the third offset magnet13passes through the vicinity of the Hall element17(hereinafter, referred to as the “magnetic flux density caused by the third offset magnet13”) and an absolute value of a magnetic flux density which is detected by the Hall element17when the fourth offset magnet13passes through the vicinity of the Hall element17(hereinafter, referred to as the “magnetic flux density caused by the fourth offset magnet13”) are larger than the absolute value of the magnetic flux density caused by the other magnets13similarly toFIG. 5. In addition, the distance from the third offset magnet13to the Hall element17when the third offset magnet13passes through the vicinity of the Hall element17is shorter than the distance from the fourth offset magnet13to the Hall element17when the fourth offset magnet13passes through the vicinity of the Hall element17, and thus, the absolute value of the magnetic flux density caused by the third offset magnet13is larger than the absolute value of the magnetic flux density caused by the fourth offset magnet13.

To correspond to this, the same U-phase threshold (indicated by the alternate long and short dash line inFIG. 13) as inFIG. 5, for example, the zero-level value is set as a threshold for detection of the switching timing of the magnetic pole of the U-phase, and a value (hereinafter, referred to as referred to as a “third rotation threshold”) (indicated by the alternate long and two short dashes line inFIG. 13), which is larger than the absolute value of the magnetic flux density caused by the other magnets13and the absolute value of the magnetic flux density caused by the fourth offset magnet13and smaller than the absolute value of the magnetic flux density caused by the third offset magnet13, is set and further, a value (hereinafter, referred to as a “fourth rotation threshold”) (indicated by the broken line inFIG. 13), which is larger than the absolute value of the magnetic flux density caused by the other magnets13and is smaller than the absolute value of the magnetic flux density caused by the fourth offset magnet13and the absolute value of the magnetic flux density caused by the third offset magnet13, are set as thresholds for detection of rotation periods of the outer rotor11in the third variation.

Similarly toFIG. 5, the timing at which the linear signal exceeds or falls below the U-phase threshold is considered as the switching timing at which the magnetic pole of the magnetic flux density detected by the Hall element17, that is, the switching timing of the magnetic pole of the U-phase in the third variation. In addition, the absolute value of the magnetic flux density caused by the third offset magnet13becomes larger than the absolute value of the magnetic flux density caused by the fourth offset magnet13as described above, and thus, a timing at which a linear signal exceeds the third rotation threshold (a period “B” inFIG. 13) is considered as a timing at which the third offset magnet13passes through the vicinity of the Hall element17. Further, the absolute value of the magnetic flux density caused by the fourth offset magnet13becomes larger than the absolute value of the magnetic flux density caused by the other magnets13and smaller than the absolute value of the magnetic flux density caused by the third offset magnet13as described above, and thus, a timing at which linear signal exceeds the fourth rotation threshold and does not exceed the third rotation threshold (a period “C” inFIG. 13) is considered as a timing at which the fourth offset magnet13passes through the vicinity of the Hall element17. Both the timing at which the third offset magnet13passes through the vicinity of the Hall element17and the timing at which the fourth offset magnet13passes through the vicinity of the Hall element17correspond to the rotation periods of the outer rotor11, and accordingly, it is possible to detect both the switching timing of the magnetic pole of the U-phase and the rotation period using the single Hall element17.

In addition, the period “B” and the period “C” occur at the different timings as shown inFIG. 13, and thus, it is possible to detect the rotation period of the third offset magnet13and the rotation period of the fourth offset magnet13, that is, the two rotation periods at different timings using the single Hall element17.

In addition, for example, a magnetic force of only one of the magnets13may be set to be different from each magnetic force of the other magnets13although only one of the magnets13is provided to be offset in the above-described motor10.

FIG. 14is a diagram indicating arrangement of the respective magnets13and arrangement of the respective Hall elements15to17when the inner circumferential surface of the outer rotor11is viewed from the central axis CL of the outer rotor11in a motor according to a fourth variation of the embodiment.

InFIG. 14, an absolute value of a magnetic force of one of the magnets13which has S-pole is set to be larger than the absolute value of the magnetic force of the other magnets13. It should be noted that the magnet13having the larger absolute value of the magnetic force set will be referred to as the “magnetic-force-changed magnet13” (shown with the hatching inFIG. 14) hereinafter. Since there is the only one magnetic-force-changed magnet13, it is possible to detect a rotation period of the outer rotor11by detecting a timing of change of a magnetic flux density caused by movement of the magnetic-force-changed magnet13.

FIG. 15is a diagram indicating signals output from the Hall elements15to17inFIG. 14.

When the other magnets13pass through the vicinity of the Hall element17, each magnetic force of the other magnets13is not changed inFIG. 15, and thus, the absolute value of the magnetic flux density thereof, which is detected by the Hall element17, is not changed. On the other hand, the absolute value of the magnetic force of the magnetic-force-changed magnet13is larger than the absolute value of the magnetic force of the other magnets13when the magnetic-force-changed magnet13passes through the vicinity of the Hall element17, and thus, an absolute value of a magnetic flux density which is detected by the Hall element17when the magnetic-force-changed magnet13passes through the vicinity of the Hall element17(hereinafter, referred to as the “magnetic flux density caused by the magnetic-force-changed magnet13”) is larger than the absolute value of the magnetic flux density caused by the other magnets13.

To correspond to this, the same U-phase threshold (indicated by the alternate long and short dash line inFIG. 15) as inFIG. 5, for example, the zero-level value is set as a threshold for detection of the switching timing of the magnetic pole of the U-phase, and a value (hereinafter, referred to as a “fifth rotation threshold”) (indicated by the broken line inFIG. 15), which is larger than the absolute value of the magnetic flux density caused by the other magnets13and is smaller than the absolute value of the magnetic flux density caused by the magnetic-force-changed magnet13is set as a threshold for detection of a rotation period of the outer rotor11in the fourth variation.

Similarly toFIG. 5, the timing at which the linear signal exceeds or falls below the U-phase threshold is considered as the switching timing at which the magnetic pole of the magnetic flux density detected by the Hall element17, that is, the switching timing of the magnetic pole of the U-phase in the fourth variation. In addition, the absolute value of the magnetic flux density caused by the magnetic-force-changed magnet13is larger than the absolute value of the magnetic flux density caused by the other magnets13as described above, and thus, a timing at which a linear signal exceeds the fifth rotation threshold is considered as a timing at which the magnetic-force-changed magnet13passes through the vicinity of the Hall element17, that is, the rotation period in the fourth variation. Accordingly, it is possible to detect both the switching timing of the magnetic pole of the U-phase and the rotation period using the single Hall element17.

It should be noted that the motor10according to the above-described embodiment may be applied not only to the driving motor (motor generator) which serves also as the power generator but also to a stator AC power generator, and can be applied to almost any three-phase brushless motor which serves also as a power generator.

In addition, the rotation period, which is detected by the motor10according to the embodiment, may be used not only for the ignition control of the engine, but also for another control using the rotation period of the crankshaft.

Further, the Hall element17is configured using the linear Hall element in the motor10according to the embodiment, but the Hall element15or the Hall element16may be configured using the linear Hall element, and the rotation period of the outer rotor11may be detected using the Hall element15or the Hall element16.

This application claims the benefit of Japanese Patent Application No. 2015-145722 filed on Jul. 23, 2015 which is hereby incorporated by reference herein in its entirety.