阅读说明：本技术 永磁同步电动机的控制装置以及图像形成装置 (Control device for permanent magnet synchronous motor and image forming apparatus ) 是由 吉川博之 铃木大地 橘优太 于 2019-05-31 设计创作，主要内容包括：本发明公开永磁同步电动机的控制装置以及图像形成装置。能够降低初始位置推测中的磁极位置的位移而提高初始位置推测的精度。无传感器型的永磁同步电动机的控制装置具有推测停止状态的转子的磁极位置即初始位置的初始位置推测部,在将电角度360度的搜索范围划分而成的n个角度位置的每一个角度位置对电枢施加用于搜索初始位置的脉冲串(PA1)。脉冲串(PA1)具有n个角度位置的1个角度位置的第1脉冲(P1)和多个第2脉冲(P2a、P2b),多个第2脉冲(P2a、P2b)是产生欲使转子向与第1方向相反的第2方向旋转的转矩的角度位置处的脉冲,第1方向是在通过该第1脉冲(P1)的施加而产生了使转子旋转的转矩时的旋转方向。(The invention discloses a control device for a permanent magnet synchronous motor and an image forming apparatus. The displacement of the magnetic pole position in the initial position estimation can be reduced to improve the accuracy of the initial position estimation. A control device for a sensorless permanent magnet synchronous motor includes an initial position estimating unit for estimating an initial position that is a magnetic pole position of a rotor in a stopped state, and applies a pulse train (PA1) for searching the initial position to an armature at each of n angular positions obtained by dividing a search range of an electrical angle of 360 degrees. The pulse train (PA1) has a1 st pulse (P1) and a plurality of 2 nd pulses (P2a, P2b) at 1 angular position of n angular positions, the plurality of 2 nd pulses (P2a, P2b) are pulses at angular positions at which a torque for rotating the rotor in a2 nd direction opposite to the 1 st direction is generated, and the 1 st direction is a rotational direction when a torque for rotating the rotor is generated by application of the 1 st pulse (P1).)

1. A control device for a permanent magnet synchronous motor of a sensorless type that rotates a rotor using a permanent magnet by using a rotating magnetic field generated by a current flowing through an armature, the control device comprising:

A driving unit that drives the rotor by applying a voltage to the armature;

An initial position estimating unit that estimates an initial position that is a magnetic pole position of the rotor in a stopped state; and

A control unit that controls the drive unit to apply a pulse train including voltage pulses for searching the initial position to the armature at each of n angular positions obtained by dividing a search range of an electrical angle of 360 degrees,

the pulse train includes a1 st pulse and a2 nd pulse, the 1 st pulse being a pulse at 1 angular position of the n angular positions, the 2 nd pulse being a pulse at an angular position at which a torque to rotate the rotor in a2 nd direction opposite to the 1 st direction is generated, the 2 nd pulse generating a torque larger than the torque generated by the 1 st pulse, and the 1 st direction being a rotation direction of the rotor when the torque to rotate the rotor is generated by applying the 1 st pulse.

2. A control device for a permanent magnet synchronous motor of a sensorless type that rotates a rotor using a permanent magnet by using a rotating magnetic field generated by a current flowing through an armature, the control device comprising:

A driving unit that drives the rotor by applying a voltage to the armature;

An initial position estimating unit that estimates an initial position that is a magnetic pole position of the rotor in a stopped state; and

A control unit that controls the drive unit to apply a pulse train including voltage pulses for searching the initial position to the armature at each of n angular positions obtained by dividing a search range of an electrical angle of 360 degrees,

The pulse train includes a1 st pulse and a plurality of 2 nd pulses, the 1 st pulse being a pulse at 1 angular position of the n angular positions, the 2 nd pulse being a pulse at an angular position at which a torque is generated to rotate the rotor in a2 nd direction opposite to the 1 st direction, the 1 st direction being a rotation direction of the rotor when the torque to rotate the rotor is generated by applying the 1 st pulse.

3. the control device of a permanent magnet synchronous motor according to claim 2,

the pulse train is a pulse train in which a plurality of groups of the 1 st pulse, the plurality of 2 nd pulses, and the 3 rd pulse are connected, and the 3 rd pulse is a pulse at an angular position at which a torque is generated to rotate the rotor in the 1 st direction.

4. the control device of a permanent magnet synchronous motor according to claim 3,

The number of pulses of the pulse train is the same as the number n of the angular positions.

5. The control device of a permanent magnet synchronous motor according to claim 4,

The number n of said angular positions is an integer multiple of 4,

The pulses constituting the pulse train are all pulses that generate magnetic field vectors at angular positions that do not correspond to other pulses,

In each group of the said pulse trains,

The plurality of 2 nd pulses are two pulses of a2 nd pulse and a3 rd pulse, the 2 nd pulse is an angular position separated by ± 90 degrees or more from a1 st position which is an angular position corresponding to the 1 st pulse, and the 3 rd position is an angular position closest to the 2 nd position,

The 3 rd pulse is a pulse at a4 th position, and the 4 th position is an angular position separated from the 3 rd position by ± 90 degrees or more.

6. The control device of a permanent magnet synchronous motor according to claim 3,

the number of said groups in said pulse train is the same as the number n of said angular positions,

In each group of the said pulse trains,

The 1 st pulse is a pulse that generates a magnetic field vector at an angular position that does not correspond to the 1 st pulse of the other group,

The plurality of 2 nd pulses are two pulses that generate magnetic field vectors at the same angular position separated by ± 90 degrees or more from the angular position corresponding to the 1 st pulse,

The 3 rd pulse is a pulse that generates a magnetic field vector at an angular position corresponding to the 1 st pulse.

7. The control device of a permanent magnet synchronous motor according to claim 6,

An initial position estimating unit estimates the initial position based on a current flowing through the armature when the 1 st pulse of each group in the pulse train is applied.

8. The control device of a permanent magnet synchronous motor according to claim 3,

The number of said groups in said pulse train is smaller than the number n of said angular positions,

In each group of the said pulse trains,

The 1 st pulse is a pulse that generates a magnetic field vector at an angular position that does not correspond to the 1 st pulse of the other group,

the plurality of 2 nd pulses are two pulses that generate magnetic field vectors at the same angular position separated by ± 90 degrees or more from the angular position corresponding to the 1 st pulse,

The 3 rd pulse is a pulse that generates a magnetic field vector at an angular position closest to the angular position corresponding to the 1 st pulse and not corresponding to the 3 rd pulse of the other group.

9. the control device of a permanent magnet synchronous motor according to claim 8,

An initial position estimating unit estimates the initial position based on currents flowing through the armature when the 1 st pulse of each group in the pulse train is applied and when the 3 rd pulses of the plurality of groups are applied.

10. The control device of a permanent magnet synchronous motor according to claim 8,

The initial position estimating unit estimates the initial position based on currents flowing through the armature when the 1 st pulse of each group in the pulse train is applied, when one of the two 2 nd pulses of a plurality of groups is applied, and when the 3 rd pulse of the plurality of groups is applied.

11. An image forming apparatus including the control device for the permanent magnet synchronous motor according to any one of claims 1 to 10, the image forming apparatus comprising:

A printer engine to print an image on a sheet at a print position,

And a roller that is rotationally driven by the sensorless permanent magnet synchronous motor controlled by the control device and conveys the sheet to the printing position.

12. The image forming apparatus according to claim 11,

The permanent magnet synchronous motor is an inner rotor type brushless motor.

Technical Field

The present invention relates to a control device for a permanent magnet synchronous motor and an image forming apparatus.

Background

In general, a Permanent Magnet Synchronous Motor (PMSM) has a stator having a winding (armature winding) and a rotor using a Permanent Magnet, and generates a rotating magnetic field by passing an alternating current through the winding. Thereby, the rotor rotates in synchronization with the rotating magnetic field.

In recent years, a sensorless permanent magnet synchronous motor is widely used. The sensorless type does not have a magnetic sensor or encoder for detecting the magnetic pole position. Therefore, in driving a sensorless permanent magnet synchronous motor, a method of estimating a magnetic pole position and a rotation speed of a rotor based on a current flowing through an induced voltage generated in a winding during rotation is used.

As a method of estimating a so-called initial position of a magnetic pole position of a rotor when a sensorless permanent magnet synchronous motor is stopped, there is a method called inductive sensing. This method utilizes the property that the inductance of the winding changes subtly depending on the magnetic pole position, and as described in patent document 1, the magnetic pole position is estimated by applying a voltage to the winding so as to sequentially excite each phase and comparing peak amplitude values of currents flowing through the winding during excitation of each phase.

By estimating the initial position, the stator can be appropriately excited according to the magnetic pole position of the rotor when the rotor is rotated thereafter.

as a conventional technique for improving the accuracy of the initial position estimation, there is a technique described in patent document 2. Patent document 2 discloses the following technique: the time for applying the voltage for estimating the initial position is controlled to a time at which the motor is not started.

Disclosure of Invention

In initial position estimation based on inductive sensing, a voltage is applied to a winding to generate a magnetic field at each of n angular positions obtained by dividing an angular position range of an electrical angle of 360 degrees (2 π) into n divisions. The current flowing through the winding is measured at each application. Then, the magnetic pole position is estimated based on the results of the plurality of measurements. For example, the angular position at which the current value is maximum is estimated as the magnetic pole position.

The voltage applied for the initial position estimation is set to be low in a range where an effective difference occurs in the measured current value according to the magnetic pole position, and the application time is set to be short in a measurable range.

However, depending on the direction of the generated magnetic field and the positional relationship between the magnetic pole positions at that time, a rotational torque may be generated by the magnetic field, and the rotor may slightly rotate. As a method of eliminating the rotation, it is considered to make the applied angular position of the odd number and the applied angular position of the even number different by 180 degrees.

However, in particular, in the inner rotor type motor, since inertia is smaller than that of the outer rotor type, even after the application of the odd-numbered stages is completed, the rotation may be continued by the inertia. Therefore, the application of the even-numbered application is performed during the rotation, and the action of the magnetic field generated in the application of the even-numbered application in which the angular positions are different by 180 degrees is limited to the braking action for stopping the inertial rotation, and the rotor is not rotated in the reverse direction. That is, the rotor is stopped in a state where the magnetic pole position is changed (slightly moved) by the rotation due to the application of the odd-numbered pieces.

There is a problem that the accuracy of the initial position estimation is lowered due to such displacement of the magnetic pole position. If the amount of displacement increases as the magnetic field is generated every time the angular position is changed in the initial position estimation, the accuracy of the initial position estimation is further degraded.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the displacement of the magnetic pole position in the initial position estimation and improve the accuracy of the initial position estimation.

A control device according to an embodiment of the present invention is a control device for a sensorless permanent magnet synchronous motor that rotates a rotor using a permanent magnet by using a rotating magnetic field generated by a current flowing through an armature, the control device including: a driving unit that drives the rotor by applying a voltage to the armature; an initial position estimating unit that estimates an initial position that is a magnetic pole position of the rotor in a stopped state; and a control unit configured to control the drive unit to apply a pulse train including a voltage pulse for searching the initial position to the armature at each of n angular positions obtained by dividing a search range of an electrical angle of 360 degrees, wherein the pulse train includes a1 st pulse and a2 nd pulse, the 1 st pulse is a pulse at 1 angular position of the n angular positions, the 2 nd pulse is a pulse at an angular position at which a torque for rotating the rotor in a2 nd direction opposite to the 1 st direction is generated, the 2 nd pulse generates a torque larger than the torque generated by the 1 st pulse, and the 1 st direction is a rotation direction of the rotor when the torque for rotating the rotor is generated by applying the 1 st pulse.

The pulse train may include a1 st pulse at an angular position of 1 of the n angular positions and a plurality of 2 nd pulses, the 2 nd pulse being a pulse at an angular position at which a torque to rotate the rotor in a2 nd direction opposite to the 1 st direction is generated, and the 1 st direction being a rotation direction of the rotor when the torque to rotate the rotor is generated by applying the 1 st pulse.

According to the present invention, the displacement of the magnetic pole position in the initial position estimation can be reduced to improve the accuracy of the initial position estimation.

Drawings

Fig. 1 is a diagram schematically showing a configuration of an image forming apparatus including a motor control device according to an embodiment of the present invention.

Fig. 2 is a diagram schematically showing the structure of the brushless motor.

Fig. 3 is a diagram showing a d-q axis model of the brushless motor.

Fig. 4 is a diagram showing an example of a functional configuration of the motor control device.

Fig. 5 is a diagram showing an example of the configuration of a motor driving unit and a current detecting unit in the motor control device.

Fig. 6 is a diagram showing an outline of the process of initial position estimation by full search.

Fig. 7 is a diagram showing an example of the measurement result of the current flowing through the armature in the initial position estimation by the full search.

Fig. 8 is a diagram showing a relationship between the direction of a voltage pulse for searching a magnetic pole position and the torque for rotating the rotor.

Fig. 9 is a diagram showing a basic search procedure for suppressing displacement of the magnetic pole position.

fig. 10 is a diagram showing the structure and action of the burst in the search sequence of fig. 9.

fig. 11 is a diagram showing an example of a sequence of rotation driving of the rollers for feeding paper.

Fig. 12 is a view showing an example 1 of the search procedure after improvement.

Fig. 13 is a diagram showing the structure and action of the pulse train of example 1 of fig. 12.

Fig. 14 is a view showing an example 2 of the search procedure after improvement.

Fig. 15 is a view showing an example 2 of the search procedure after improvement.

Fig. 16 is a diagram showing the structure and action of the pulse train of example 2 of fig. 14 and 15.

Fig. 17 is a view showing an example 3 of the improved search procedure.

Fig. 18 is a diagram showing the structure and action of the pulse train of example 3 of fig. 17.

Fig. 19 is a diagram showing an example 4 of the improved search procedure.

Fig. 20 is a diagram showing the structure and action of the burst of example 4 of fig. 19.

fig. 21 is a diagram showing an outline of a process flow in the motor control device.

Description of the reference numerals

1: an image forming apparatus; 2: a sheet material; 3. 3A, 3B: motors (permanent magnet synchronous motors); 10: a printer engine; 15: a paper feed roller (roller); 21. 21A, 21B: a motor control device (control device); 23: a vector control unit (control unit); 25: an initial position estimating unit; 26: a motor drive unit (drive unit); 31. 31 b: a stator (armature); 32. 32 b: a rotor; 90: a printing position; F. f1, F2: torque; i: current flow; pg 1-Pg 12: group (d); p1: pulse (1 st pulse); p2a, P2 b: pulse (pulse 2); p3: pulse (pulse 3); PA1, PA2, PA3, PA 4: a pulse train; PS: a magnetic pole position; PSs: an initial position; θ: angle (angular position); θ 1: angle 1 (position 1); θ 2: angle 2 (position 2); θ 3: angle 3 (position 3); θ 4: angle 4 (position 4).

Detailed Description

Fig. 1 shows an outline of a configuration of an image forming apparatus including a motor control device according to an embodiment of the present invention, and fig. 2 schematically shows a configuration of a brushless motor 3.

In fig. 1, an image forming apparatus 1 is an electrophotographic color printer including a tandem printer engine 10. The lower portion 1B is a sheet cassette having a two-stage structure including drawer type sheet feed trays 13A and 13B.

The image forming apparatus 1 forms a color or monochrome image according to a job input from an external host apparatus via a network. The image forming apparatus 1 includes a control circuit 100 for controlling the operation thereof. The control circuit 100 includes a processor for executing a control program and peripheral devices (ROM, RAM, etc.) thereof.

the printer engine 1A has 4 image forming units 11y, 11m, 11c, 11k, an intermediate transfer belt 12, and the like.

The image forming units 11y to 11k have the same basic configuration, and include a cylindrical photoreceptor, a charger, a developer, a cleaner, a light source for exposure, and the like. The intermediate transfer belt 12 is wound around between a pair of rollers and rotates. Inside the intermediate transfer belt 12, primary transfer rollers are disposed for each of the image forming units 11y to 11 k.

In the color printing mode, the image forming units 11Y to 11K form toner images of 4 colors of Y (yellow), M (magenta), C (cyan), and K (black) in parallel. The toner images of 4 colors are sequentially primary-transferred onto the rotating intermediate transfer belt 12. The toner image of Y is transferred first, and the toner image of M, the toner image of C, and the toner image of K are sequentially transferred in an overlapping manner.

In parallel with the formation of the toner image, the sheet (recording paper) 2 is fed out from one paper feed tray 13 selected according to the designation of the job by the pickup roller 14, and is conveyed to the registration roller 16 by the paper feed roller 15.

The primary-transferred toner image is secondarily transferred to the sheet 2 conveyed by the registration roller 16 at the printing position 90 opposite to the secondary transfer roller 17. After the secondary transfer, the sheet 2 is sent out to the upper paper discharge tray 19 through the inside of the fixing device 18. When passing through the fixing device 18, the toner image is fixed to the sheet 2 by heating and pressing.

The image forming apparatus 1 includes a plurality of motors as drive sources for rotating rotary members such as a photoreceptor, a developing device, and various rollers. One of the motors 3A rotationally drives a roller group of the upper stage paper feed tray 13A. The other motor 3B rotationally drives the roller group of the lower sheet feed tray 13B. These motors 3A, 3B are controlled by motor control devices 21A, 21B, respectively. The motor control devices 21A and 21B rotate or stop the motors 3A and 3B in accordance with instructions from the control circuit 100.

Hereinafter, the motor 3A and the motor 3B may be referred to as "motor 3" without distinction, and the motor control device 21A and the motor control device 21B may be referred to as "motor control device 21" without distinction.

In fig. 2, the motors 3a and 3b are DC brushless motors, and more specifically, Permanent Magnet Synchronous Motors (PMSM) of sensorless type.

The motor 3a shown in fig. 2(a) includes a stator 31 as an armature for generating a rotating magnetic field and an inner rotor 32 using a permanent magnet. The stator 31 has cores 36, 37, 38 of U-phase, V-phase, and W-phase arranged at an electrical angle interval of 120 °, and 3 windings (coils) 33, 34, 35 of Y-connection. The cores 36, 37, 38 are sequentially excited by passing three-phase ac currents of U-phase, V-phase, and W-phase through the windings 33 to 35, thereby generating a rotating magnetic field. The rotor 32 rotates in synchronization with the rotating magnetic field.

The motor 3B shown in fig. 2(B) includes a stator 31B that generates a rotating magnetic field and an outer rotor 32B that uses permanent magnets. The stator 31b has cores 36b, 37b, and 38b of U-phase, V-phase, and W-phase arranged at an electrical angle interval of 120 °, and 3 windings 33b, 34b, and 35b of Y-connection. The motor 3b also rotates in synchronization with the rotating magnetic field, similarly to the motor 3.

in general, an outer rotor type motor has higher inertia of a rotor (rotor) than an inner rotor type motor of the same stage, and thus has excellent stability at the time of constant speed rotation. In contrast, the inner rotor type motor has a small inertia and thus has excellent responsiveness.

In the image forming apparatus 1, in a multi-print job using a plurality of sheets 2, it is necessary to repeat the start and stop of the pickup roller 14 and the paper feed roller 15 in a short time. Therefore, the inner rotor type motor 3A having excellent responsiveness is used as the motors 3A and 3B.

In the example shown in fig. 2(a), the number of magnetic poles of the rotor 32 is 4. However, the number of magnetic poles of the rotor 32 is not limited to 4, and may be 2 or 6 or more. In addition, the number of slots of the stator 31 is not limited to 6. In short, the motor control devices 21A and 21B perform vector control (sensorless vector control) for estimating the magnetic pole position and the rotation speed of the motors 3A and 3B using a control model based on a d-q axis coordinate system.

Hereinafter, the rotational angle position of the N pole, which is indicated by two turns, of the S pole and the N pole of the rotor 32 is sometimes referred to as a "magnetic pole position PS" of the rotor 32. The direction from the rotation center of the rotor 32 to the magnetic pole position PS is sometimes referred to as a "magnetic pole direction".

Fig. 3 shows a d-q axis model of the motor 3. In the vector control of the motor 3, three-phase alternating current flowing through the windings 33 to 35 of the motor 3 is converted into direct current flowing through two-phase windings that rotate in synchronization with the permanent magnet as the rotor 32, thereby simplifying the control.

The magnetic flux direction (direction of N pole) of the permanent magnet is defined as d-axis, and the direction advancing by an electrical angle of pi/2 [ rad ] (90 DEG) from the d-axis is defined as q-axis. The d-axis and q-axis are model axes. With the U-phase winding 33 as a reference, the d-axis advance angle with respect thereto is defined as θ. The angle θ indicates an angular position (magnetic pole position PS) of the magnetic pole of the winding 33 with respect to the U-phase. The d-q coordinate system is located at a position which is based on the winding 33 of the U-phase and is advanced therefrom by an angle θ.

since the motor 3 does not have a position sensor for detecting the angular position (magnetic pole position) of the rotor 32, the motor control device 21 needs to estimate the magnetic pole position PS of the rotor 32. The γ axis is determined in accordance with the estimated angle θ m indicating the estimated magnetic pole position, and the position advanced by an electrical angle of pi/2 from the γ axis is determined as the δ axis. The γ - δ coordinate system is in a position with reference to the winding 33 of the U-phase and advanced therefrom by an estimation angle θ m. The delay amount of the presumed angle θ m with respect to the angle θ is defined as Δ θ. When the retardation amount Δ θ is zero, the γ - δ coordinate system coincides with the d-q coordinate system.

Fig. 4 shows an example of a functional configuration of the motor control device 21, and fig. 5 shows an example of configurations of the motor driving unit 26 and the current detection unit 27 in the motor control device 21. Fig. 6 shows an outline of the process of initial position estimation by full search, and fig. 7 shows an example of a measurement result of the current flowing through the armature in the initial position estimation by full search.

As shown in fig. 4, the motor control device 21 includes a vector control unit 23, a speed/position estimation unit 24, an initial position estimation unit 25, a motor drive unit 26, a current detection unit 27, and the like.

The motor drive unit 26 is a three-phase inverter that drives the rotor 32 by passing current through the windings 33 to 35 of the motor 3. As shown in fig. 5, the motor drive unit 26 includes transistors (e.g., field effect transistors: FETs) Q1 to Q6 having characteristics that are uniform for each phase, a pre-drive circuit 265, and the like.

the transistors Q1 to Q6 control the current I flowing from the DC power supply line 211 to the ground line via the windings 33 to 35. Specifically, the current Iu flowing through the winding 33 is controlled by the transistors Q1 and Q2, and the current Iv flowing through the winding 34 is controlled by the transistors Q3 and Q4. Then, the current Iw flowing through the winding 35 is controlled by the transistors Q5, Q6.

In fig. 5, the pre-drive circuit 265 converts the control signals U +, U-, V +, V-, W +, W-input from the vector control section 23 into voltage levels suitable for the respective transistors Q1 to Q6. The converted control signals U +, U-, V +, V-, W +, W-are input to control terminals (gates) of the transistors Q1 to Q6.

The current detection unit 27 includes a U-phase current detection unit 271 and a V-phase current detection unit 272, and detects currents Iu and Iv flowing through the windings 33 and 34. Since Iu + Iv + Iw is 0, the current Iw can be obtained by calculation from the values of the detected currents Iu and Iv.

The U-phase current detection unit 271 and the V-phase current detection unit 272 amplify and a/D convert a voltage drop caused by the shunt resistance inserted into the flow path of the currents Iu and Iv, and output the amplified voltage drop as detected values of the currents Iu and Iv. That is, the detection by the binary flow method is performed. The resistance value of the shunt resistor is a small value of the order of 1/10 Ω.

Returning to fig. 4, the vector control unit 23 controls the motor drive unit 26 based on the speed command value ω included in the command S1 from the control circuit 100. When executing a job, the control circuit 100 gives a speed command value ω corresponding to a processing speed set in accordance with the job to the vector control unit 23. Further, when the image forming apparatus 1 is powered on, when a job is executed, or when the power saving mode is returned to the normal mode, or the like, execution of the initial position estimation is instructed.

when instructed to start, the vector control unit 23 controls the motor drive unit 26 to generate a rotating magnetic field that rotates from the initial position estimated and stored by the initial position estimation unit 25.

the vector control unit 23 includes a speed control unit 41, a current control unit 42, an output coordinate conversion unit 43, a PWM conversion unit 44, and an input coordinate conversion unit 45. These units perform processing for vector control of the motor 3 as follows.

The speed control unit 41 determines the current command values I γ, I δ in the γ - δ coordinate system based on the speed command value ω from the control circuit 100 and the speed estimation value ω m from the speed/position estimation unit 24 so that the speed estimation value ω m approaches the speed command value ω.

The current control unit 42 determines the voltage command values V γ, V δ in the γ - δ coordinate system based on the current command values I γ, I δ.

The output coordinate conversion unit 43 converts the voltage command values V γ, V δ into the voltage command values Vu, Vv, Vw of the U-phase, V-phase, and W-phase based on the estimated angle θ m from the speed/position estimation unit 24.

The PWM conversion unit 44 generates control signals U +, U-, V +, V-, W +, W-based on the voltage command values Vu, Vv, Vw, and outputs the control signals U +, U-, V +, V-, W +, W-to the motor drive unit 26. The control signals U +, U-, V +, V-, W +, W-are signals for controlling the frequency and amplitude of the three-phase ac power supplied to the motor 3 by Pulse Width Modulation (PWM).

The input coordinate conversion unit 45 calculates a value of the W-phase current Iw from each value of the U-phase current Iu and the V-phase current Iv detected by the current detection unit 27. Then, estimated current values I γ and I δ in the γ - δ coordinate system are calculated based on the estimated angle θ m from the speed/position estimating unit 24 and the values of the currents Iu, Iv, Iw of the three phases. That is, the current is converted from three phases to two phases.

The speed/position estimating unit 24 obtains a speed estimated value ω m and an estimated angle θ m according to a so-called voltage-current equation based on the estimated current values I γ and I δ from the input coordinate converting unit 45 and the voltage command values V γ and V δ from the current control unit 42. The calculated estimated velocity value ω m is input to the velocity control unit 41, and the calculated estimated angle θ m is input to the output coordinate conversion unit 43 and the input coordinate conversion unit 45.

The initial position estimating unit 25 estimates an initial position PSs (see fig. 6) which is a magnetic pole position PS of the rotor 32 in a stopped state by using an inductive sensing method. The stopped state is not necessarily limited to a state in which the rotor 32 is completely stationary, and may be a state in which the rotor is rotating at a low speed close to zero or is immediately stationary with small amplitude vibration.

The estimation of the initial position PSs is as follows.

The initial position estimation in the present embodiment uses a so-called full search method in which a voltage pulse for searching for an initial position is applied to each of n angular positions obtained by equally dividing a search range of an electrical angle of 360 degrees into n divisions.

As the processing of the initial position estimation based on the full search, the speed control unit 41 controls the motor drive unit 26 to apply the pulse P (voltage pulse V θ) shown in fig. 6(a) and (B) a plurality of times while changing the angle θ when the rotor 32 is in the stopped state.

in fig. 6(a), the pulse P is a vector, and the direction thereof, that is, the angle θ of the pulse P is switched to 30 degrees each shifted by dividing the search range of 360 degrees in electrical angle by 12. That is, the pulse P is applied to each of 12 directions shifted by 30 degrees.

Hereinafter, the case where the pulse P is applied while changing its direction to estimate the initial position PSs is sometimes referred to as "search".

When a pulse P for search is applied, a current flows through each of the windings 33 to 35 according to the angle theta of the pulse P. The magnitude of the current is inversely proportional to the impedance of the windings 33-35 corresponding to the angle theta of the pulse P. The impedance of the windings 33 to 35 is mainly determined by their inductance, and is lowest on the d-axis in the direction of the N-pole of the permanent magnet. Therefore, when the current flowing by the application of the pulse P is maximum, the angular position of the pulse P is referred to as the d-axis. When the angle θ of the pulse P is set to the angular position of the winding 33 with respect to the U-phase, the angle θ of the pulse P is the d-axis.

Further, since a magnetic field (magnetic field vector) is generated by application of the pulse P, a torque for rotating the rotor 32 may be generated by the magnetic field. When torque is generated, the rotor 32 may rotate and the magnetic pole position may change.

In the present embodiment, in order to make the rotor 32 not rotate as much as possible, the 2 nd pulse P is generated so as to generate a magnetic field vector at another angle θ at which a torque is generated to rotate in the 2 nd direction opposite to the 1 st direction, which is a rotation direction by the torque generated by the application of the 1 st pulse P. In order to increase the torque by the 2 nd pulse P to be larger than the torque by the 1 st pulse P, the number of the 2 nd pulses P is increased or the size of the pulses P is increased.

In the vector control during the search, the pulse P can be applied by controlling the voltage command values V γ, V δ input to the output coordinate conversion unit 43 in the actual process for controlling the motor drive unit 26. However, in the search, voltage command values Vd and Vq are used instead of voltage command values V γ and V δ. In other words, in this case, pulse P can be applied by specifying angle θ by setting voltage command value Vq to zero and voltage command value Vd to an appropriate magnitude.

Note that, instead of supplying voltage command values Vd and Vq to current control unit 42, current command values Id and Iq may be supplied to current control unit 42, and after angle θ is corrected based on the angular difference between the current command and the voltage command, corrected angle θ may be input to current control unit 42 or output coordinate conversion unit 43. In this case, current control unit 42 generates voltage command values Vd and Vq for applying pulse P based on input current command values Id and Iq.

For example, as a process for searching, as shown in fig. 4, the speed control unit 41 supplies the current command values Id and Iq to the current control unit 42, and inputs the angle θ stored as the angle setting information 80 to the output coordinate conversion unit 43. The angle θ increases by 30 degrees (π/6) each time a pulse P is applied, for example, starting from 0 until 330 degrees (11 π/6) is reached.

Instead of the current command values I γ, I δ, the current control unit 42 determines the voltage command values V γ, V δ based on the current command values Id, Iq. That is, in the initial position estimation process, voltage command values Vd and Vq are determined in accordance with current command values Id and Iq. When voltage command value Vq is set to 0, the angle of voltage command value Vd matches angle θ of pulse P.

As described above, current control unit 42 may be configured to set the position and voltage value of pulse P by directly outputting voltage command values Vd and Vq without using current command values Id and Iq.

Instead of estimating the angle θ m, the output coordinate conversion unit 43 converts the voltage command values V γ, V δ into voltage command values Vu, Vv, Vw based on the angle θ. Based on the voltage command values Vu, Vv, Vw, the PWM conversion unit 44 generates a control signal U +, U-, V +, V-, W +, W-, and the motor drive unit 26 applies a pulse P to the motor 3 in accordance with the control signal U +, U-, V +, V-, W +, W-.

the waveform of each pulse P shown in fig. 6(B) is a single rectangle, but actually the waveform of the voltage applied to the motor 3 is composed of a plurality of rectangles each pulse-width-modulated at a clock cycle of 10kHz to 20kHz for each of the U-phase, V-phase, and W-phase, for example.

As shown in FIG. 6(B), the estimated current value I gamma flowing through the windings 33 to 35 increases with the application of each pulse P and decreases with the end of the application of each pulse P. The increase and decrease are changes in the exponential functionality. Each pulse P is applied at a timing at which the estimated current value I γ increased by the application of the previous pulse P decreases to the level before the increase. The period H for applying the pulse P is, for example, about 0.5 to 1 ms.

The initial position estimating unit 25 acquires the estimated current values I γ and I δ from the input coordinate converting unit 45 at the time when the time T0 shorter than the pulse width of each pulse P has elapsed since the rising edge of each pulse P. When the pulse P is applied 12 times, 12 estimated current values I γ are sequentially acquired. The estimated current values I gamma and I delta correspond to currents I flowing through windings 33 to 35 of the stator 31.

In the example shown in fig. 6(a), the initial angle θ s, which is an angle corresponding to the initial position PSs, is about 43 degrees. Therefore, in fig. 7, the estimated current value I γ when the searched angle θ is 30 degrees or 60 degrees close to the initial angle θ s is larger than the estimated current value I γ when the angle is other times, particularly when the angle is 210 degrees or 240 degrees close to the position directly opposite to the initial position PSs.

the initial position estimating unit 25 estimates an angle θ corresponding to the maximum estimated current value I γ among the 12 acquired estimated current values I γ as an initial angle θ s. Alternatively, two or more predetermined numbers of the 12 estimated current values I γ are extracted in order from the larger estimated current value I γ, and the angle at which the estimated current value I γ becomes the largest is calculated as the initial angle θ s by interpolation operation based on the extracted predetermined number of estimated current values I γ.

The speed control unit 41 inputs the notified initial angle θ s to the output coordinate conversion unit 43 as an initial value of the estimated angle θ m when the rotation of the rotor 32 is started. Thereby, the motor drive unit 26 is controlled so as to rotate the rotor 32 from the estimated initial position PSs.

Fig. 8 shows the relationship between the direction of the pulse P (voltage pulse V θ) for searching the magnetic pole position PS and the torques F1, F2 for rotating the rotor 32, fig. 9 shows a basic search procedure for suppressing the displacement of the magnetic pole position PS, and fig. 10 shows the structure and action of the pulse train PA0 relating to the search procedure of fig. 9.

In the initial position estimation, a torque F for rotating the rotor 32 may be generated based on a positional relationship between the direction of the generated pulse P and the magnetic pole position PS at that time. That is, in fig. 8, it is assumed that when the direction of the magnetic field vector based on the pulse P accidentally coincides with the d-axis passing through the magnetic pole position PS, the torque F is not generated, and the holding force for suppressing the rotation is generated. However, if the d-axis does not coincide with the d-axis, the 1 st direction torque F1 or the 2 nd direction torque F2 is generated. The torques F1 and F2 increase as the direction of the magnetic field vector approaches the q-axis.

when a torque F having a magnitude against the inertial force is generated, the rotor 32 rotates and the magnetic pole position PS is displaced. The displacement of the magnetic pole position PS reduces the accuracy of the initial position estimation. The decrease in accuracy causes a delay in the rise of the motor 3 at the time of starting.

In order to reduce the displacement amount of the magnetic pole position PS from the start to the end of the initial position estimation, as shown in fig. 9, it is considered that the direction (angle) of the odd-numbered generated pulses P and the direction of the even-numbered generated pulses P are different by 180 degrees.

In the example of fig. 9, the angles θ of the 1 st, 3 rd, 5 th, 7 th, 9 th, and 11 th are set to 0 °, 30 °, 60 °, 90 °, 120 °, and 150 ° in this order. The angles θ of the 2 nd, 4 th, 6 th, 8 th, 10 th, and 12 th are set to 180 °, 210 °, 240 °, 270 °, 300 °, and 330 ° in this order. That is, a pulse train PA0 including 12 pulses P11 to P22 shown in fig. 10 is applied.

in the search for applying such a pulse train PA0, for example, as shown in fig. 10, when the torque F1 is generated when the 1 st pulse P11 is applied, the torque F2 in the opposite direction is generated when the 2 nd pulse P12 is applied.

If the motor 3 is of an outer rotor type, even if the rotor 32 is rotated by the generation of the torque F, the torque F is reduced as the application of each pulse P11, P12 is completed, and the rotation is stopped before the next pulse is applied as the rotation speed is reduced.

However, as described above, in the case where the inner rotor type motor is used as the motor 3, the rotor 32 that starts to move due to the application of the 1 st pulse P11 may continue to rotate due to inertia even after the application of the pulse P11 is completed. However, since the pulse application cycle is short, the amount of rotation until the 2 nd pulse P12 is applied is about 1 °, and is sufficiently smaller than the division angle (30 ° in this example) of the search range.

The magnitude of the torque F2 based on the 2 nd pulse P12 is substantially equal to the magnitude of the torque F1 based on the 1 st pulse P11.

However, the torque F2 based on the 2 nd pulse P12 functions as a brake for stopping the inertial rotation of the rotor 32, but does not become a driving force for stopping the inertial rotation and rotating in the reverse direction. That is, the amount of displacement of the magnetic pole position PS until the inertial rotation is stopped is not reduced even if the pulse P12 is applied.

The 3 rd pulse P13 is applied in a state where the rotor 32 is stopped. As long as the direction based on the applied magnetic field vector does not coincide with the magnetic pole direction, a torque F is generated more or less. The torque F may be smaller than the torque F1 based on the 1 st pulse P11 and may be larger than the torque F1 based on the 1 st pulse P11. The torque based on the 3 rd pulse P13 is in the same direction as the torque F1 based on the 1 st pulse P11 in the figure, but may be in the opposite direction to the torque F1 based on the 1 st pulse P11.

in either case, when the rotor 32 is rotated by the newly generated torque F, the magnetic pole position PS is displaced and the displacement amount is not reduced even when the 3 rd and 4 th pulses are applied, as in the case of the 1 st and 2 nd pulse application. That is, the displacement amount from the start of the initial position estimation increases.

Thereafter, the displacement amount increases every time the odd-numbered pulses P15, P17, P19, P21 are applied.

The displacement of the magnetic pole position PS in the initial position estimation lowers the estimation accuracy, and also affects the timing setting of the paper feed control of the sheet 2 as described below.

Fig. 11 shows an example of a sequence of rotation driving of the rollers for paper feeding. Specifically, fig. 11(a) shows a plurality of stages of the paper feeding operation in the multi-print job, fig. 11(B) shows the timing of the roller control, and fig. 11(C) shows an example of the displacement of the sheet 2a due to the rotation of the motor 3 in the initial position estimation.

In fig. 11 a and 11B, at a timing t0, the paper feed roller group (the collective name of the pickup roller 14 and the paper feed roller 15) and the registration roller 16 are stopped. At this time, it is assumed that the initial position PSs of the motor 3 that drives the paper feed roller group has already been estimated.

At timing t1, the motor 3 is started and the feed roller group starts rotating. At timing t2, the uppermost sheet 2a is drawn out from the paper feed tray 13 and conveyed toward the registration roller 16.

After that, when the sheet 2a reaches the registration roller 16, the paper feed roller group is stopped (timing t 3). The following control is performed: in the first half of the conveyance (paper feed) from the paper feed tray 13 to the registration roller 16, the motor 3 is rotated at a high speed to improve productivity, and in the second half of the conveyance (paper feed), the motor 3 is decelerated to stop the sheet 2 at the position of the registration roller 16. The deceleration is started at a predetermined timing based on the output of the sheet sensor 51 disposed in the vicinity of the downstream side of the paper feed roller 15, for example.

At timing t4 suitable for registration (registration) of the image in secondary transfer with the sheet 2, the registration roller 16 starts rotating, and the sheet 2a is conveyed toward the printing position 90. At this time, the paper feed roller group is stopped.

at timing t5 delayed from timing t4, the paper feed roller group rotates again to start feeding the 2 nd sheet 2 b. By setting the time T45 from the timing T4 to the timing T5, the distance (paper interval) between the sheets 2a and 2b can be adjusted. Before paper feeding is resumed, the initial position PSs of the motor 3 may be estimated again as needed until a time t5 elapses after the 1 st sheet 2a passes through the paper feed roller 15.

At timing t6, when the sheet 2b reaches the registration roller 16, the paper feed roller group is stopped. Thereafter, the sheet 2b is conveyed to the printing position 90 in the same manner as the 1 st sheet, and the 3 rd sheet 2c is fed.

In the initial position estimation before the start of such a series of paper feeding operations, when the magnetic pole position PS of the motor 3 is displaced, the pickup roller 14 rotates. Therefore, as shown in fig. 11(C), at timing t0, the sheet 2a is sometimes fed by the length d 1. In this case, since the conveying distance D1 during paper feeding is shortened by the length D1, the conveying speed needs to be slowed down in order to stop the sheet 2a at the position of the registration roller 16. If the conveyance speed is slowed, the paper interval must be increased to prevent overlapping of the succeeding sheet 2 b. Therefore, productivity of multi-printing is lowered.

For example, when the upper stage paper feed tray 13A is used daily and the lower stage paper feed tray 13B is rarely used, the motor 3B of the motors 3A and 3B cannot be started up by only estimating the initial position at the time of power-on or the like in many cases. That is, the displacement amount of the magnetic pole position PS in each initial position estimation is continuously accumulated. Therefore, when the paper feed tray 13B is rarely used, the length d1 over which the sheet 2 is fed out is significantly longer than the length of the paper feed tray 13A, and therefore, the sheet 2 may be excessively fed to the registration roller 16 and a jam may occur.

Therefore, the image forming apparatus 1 is provided with a function of reducing the amount of displacement of the magnetic pole position PS by searching the initial position PS in a modified order from the search order shown in fig. 9. The configuration and operation of the image forming apparatus 1 will be described below, focusing on the improved search procedure.

In the present embodiment, the number n of directions in which the pulses P are generated is 12 that is an integral multiple of 4, and the division angle of the search range of the electrical angle 360 ° is 30 °. However, the number n is not limited to this, and may be a value 2 times or more the number 4, for example, 72 to 8. In this case, the division angle is a value in the range of 5 ° to 45 °.

Fig. 12 shows an example 1 of the search procedure after improvement, and fig. 13 shows the configuration and operation of the burst PA1 of the example 1 of fig. 12.

the search performed in the order of example 1 of fig. 12 is a search in which the burst PA1 shown in fig. 13 is applied. The number of pulses of the pulse train PA1 is 12, which is the same as the number of searched angles θ. That is, each of the 12 pulses constituting the pulse train PA1 generates a magnetic field vector at an angle θ that does not correspond to the other pulses, and the current I flowing through the windings 33 to 35 is measured every time a pulse is applied. The black circles in fig. 12 indicate the measured current I during the application of the pulse. The case where the number of pulses is equal to the number of times of measurement of the current I is the same as the case of the search based on the sequence shown in fig. 9.

The burst PA1 is a burst in which 3 groups Pg1, Pg2, and Pg3 in total, each consisting of 4 pulses P1, P2a, P2b, and P3, are connected.

The illustrated pulse train PA1 schematically shows an application period of a voltage to be actually applied to the motor 3 by pulse-width modulating each of the U-phase, V-phase, and W-phase. The same applies to other examples below.

In each of the groups Pg1, Pg2, and Pg3, the 1 st pulse P1 is the 1 st pulse P, which is the 1 st pulse P at the 1 st angle θ 1 among the 12 angles θ. The 1 st angle θ 1 is determined not to be repeated with the 1 st angle θ 1 corresponding to the 1 st pulse P1 of the other group.

The two pulses P2a and P2b of the 2 nd and 3 rd are the 2 nd pulse applied sequentially at the 2 nd angle θ 2 and the 3 rd angle θ 3 to generate the torque F to rotate the rotor 32 in the 2 nd direction opposite to the 1 st direction in the rotation direction of the rotor 32 when the torque F to rotate the rotor 32 is generated by the application of the 1 st pulse P1. The 2 nd angle θ 2 is set to an angle θ that is separated from the 1 st angle θ 1 by ± 90 ° or more (for example, 180 °). In this example, the 3 rd angle θ 3 is set to the angle θ closest to the 2 nd angle θ 2 among the angles θ not corresponding to the pulses of the other groups.

The 4 th pulse P3 is a3 rd pulse that generates a magnetic field vector at a4 th angle θ 4, and the 4 th angle θ 4 is an angle at which a torque F is generated to rotate the rotor 32 in the 1 st direction, which is the same as the rotation based on the 1 st pulse P1. The 4 th angle θ 4 is an angle θ separated from the 3 rd angle θ 3 by ± 90 ° or more (for example, 180 °).

In the present example 1, the 1 st, 2 nd, 3 rd, and 4 th angles θ 1, θ 2, θ 3, and θ 4 of the group Pg1 are set to 0 °, 180 °, 210 °, and 30 ° in this order. In the group Pg2, 60 °, 240 °, 270 °, and 90 ° are set in the same order, and in the group Pg3, 120 °, 300 °, 330 °, and 150 ° are set in the same order.

As shown in fig. 13, for example, when a torque F1 is generated when the 1 st pulse P1 (1 st pulse) of the foremost group Pg1 is applied, the rotor 32 rotates. The rotor 32 continues to rotate due to inertia even after the application of the pulse P1 is completed.

The opposite direction torque F2 is generated when the 2 nd pulse P2a (1 st 2 nd pulse) is applied. Thereby, the inertial rotation of the rotor 32 is stopped. However, the displacement amount of the magnetic pole position PS before the inertial rotation is stopped cannot be reduced by the torque F2 based on the pulse P2 a.

The above situation is the same as the situation when the pulses P11 and P12 in fig. 10 are applied.

Unlike the case of fig. 10, by the application of the 3 rd pulse P2b (2 nd pulse), a torque F2 in the same direction as the torque F2 based on the 2 nd pulse P2a is generated. Thus, although the timing of generation is different, the total amount of the torque F2 that is generated after the start of the displacement of the magnetic pole position PS by the 1 st pulse P1 and that acts to suppress the displacement is increased.

That is, since the torque F2 based on the pulse P2b is added to the torque F2 based on the pulse P2a, the rotation of the rotor 32 is not stopped but stopped and reversely rotated.

The reverse rotation started by the application of the 3 rd pulse P3 reduces the displacement amount of the magnetic pole position PS. However, after the application of the pulse P3 is completed, the rotor 32 continues to rotate in the reverse direction by inertia.

If the 4 th pulse P4 (3 rd pulse) is applied, a torque F1 in the same direction as the torque F1 based on the 1 st pulse P1 is generated. The torque F1 stops the reverse rotation based on the inertia of the 3 rd pulse P3.

Thus, the magnetic pole position PS is returned to the substantially original position by canceling the displacement of the magnetic pole position PS due to the 1 st pulse P1 and the 2 nd pulse P2a by the 3 rd pulse P2b and the 4 th pulse P3. Although not completely returned, at least the displacement amount of the magnetic pole position PS is reduced.

The configuration of the groups Pg2 and Pg3 other than the foremost group is basically the same as that of the group Pg1, except that the values of the angles θ 1 to θ 4 corresponding to the respective pulses are different. That is, any group is composed of the following pulses: a pulse P1 as a1 st pulse for searching for 1 angle θ; two pulses P2a, P2b as the 2 nd pulse which stops and reversely rotates the rotation; and a pulse P3 as a3 rd pulse for stopping the reverse rotation. Therefore, in the groups Pg2 and Pg3, similarly to the group Pg1, when a torque of a magnitude for rotating the rotor 32 is generated in each group and the magnetic pole position PS is displaced, the magnetic pole position PS can be returned to the original operational effect.

The arrangement order of the groups Pg1, Pg2, and Pg3 is not limited to the illustrated order, and can be arbitrarily replaced by a group unit. For example, the top may be set to the group Pg 3. In this case, the angle θ of the first pulse P is 90 °.

Fig. 14 and 15 show an improved search procedure 2 nd example, and fig. 16 shows the configuration and operation of a burst PA2 of the 2 nd example of fig. 14 and 15.

The search performed in the order of example 2 is a search in which the burst PA2 shown in fig. 16 is applied. The number of pulses of the pulse train PA2 is 48 which is more than 12 as the number n of searched angles θ. The pulse train PA2 includes pulses applied to reduce the displacement amount of the magnetic pole position PS in addition to the 12 pulses required for measuring the current I.

The burst PA2 is a burst in which 12 groups Pg1, Pg2, Pg3, Pg4, Pg5, Pg6, Pg7, Pg8, Pg9, Pg10, Pg11, and Pg12, which are the same as the number n of search angles θ, are connected. These groups Pg1 to Pg12 are each composed of 4 pulses P1, P2a, P2b, and P3.

As described above, the pulse P1 is the 1 st pulse at the 1 st angle θ 1, and the pulses P2a, P2b are the 2 nd pulses at the 2 nd angle θ 2 or the 3 rd angle θ 3. And, the pulse P3 is the 3 rd pulse at the 4 th angle θ 4.

the differences between the groups Pg1 to Pg12 of the burst PA2 of example 2 and the groups Pg1 to Pg3 of example 1 shown in fig. 12 are the values of the 2 nd angle θ 2, the 3 rd angle θ 3, and the 4 th angle θ 4.

In the above-described 1 st example, the value of the 2 nd angle θ 2 is different from the value of the 3 rd angle θ 3, whereas in the present 2 nd example, the same value is set at 180 ° apart from the 1 st angle θ 1. In the above-described example 1, the value of the 1 st angle θ 1 is different from the value of the 4 th angle θ 4, but in the present example 2, the same value is used.

for example, the 1 st, 2 nd, 3 rd, and 4 th angles θ 1, θ 2, θ 3, and θ 4 of the group Pg1 in this 2 nd example are set to 0 °, 180 °, and 0 ° in this order. In the group Pg2, 30 °, 210 °, and 30 ° are set in the same order, and in the last group Pg12, 330 °, 150 °, and 330 ° are set in the same order.

According to the initial position estimation of the applied pulse train PA2 of example 2, in each of the groups Pg1 to Pg12, the magnetic field vectors based on the pulses P1 and P2a and the magnetic field vectors based on the pulses P2b and P3 are in a positive-negative relationship, and the torque F of the magnetic pole position PS displacement and the torque F of the return displacement are set to be equal in magnitude. Thus, even if the magnetic pole position PS is displaced by the application of the pulse P1, the magnetic pole position PS is more reliably returned to the original position when the application of the pulse P3 is completed.

By combining 4 pulses P1, P2a, P2b, and P3, the effect of canceling the displacement of the magnetic pole position PS can be obtained for each group Pg, and therefore the order of arrangement of the groups Pg1 to Pg12 can be arbitrarily changed for each group.

Fig. 17 shows an example 3 of the improved search procedure, and fig. 18 shows the structure and operation of a burst PA3 of example 3 of fig. 17.

The search performed in the order of example 3 is a search in which the burst PA3 shown in fig. 18 is applied. The number of pulses of the pulse train PA3 is 24 which is larger than 12 which is the number n of angles θ searched for, but smaller than in the above-described 2 nd example. The pulse train PA3 includes pulses applied to reduce the displacement amount of the magnetic pole position PS in addition to the 12 pulses required for measuring the current I.

The burst PA3 is a burst in which 6 groups Pg1, Pg2, Pg3, Pg4, Pg5, and Pg6, which are smaller than 12 as the number n of angles θ of search, are connected. These groups Pg1 to Pg6 are each composed of 4 pulses P1, P2a, P2b, and P3.

The pulse P1 is the 1 st pulse at the 1 st angle θ 1, and the pulses P2a, P2b are the 2 nd pulses at the 2 nd angle θ 2 or the 3 rd angle θ 3. And, the pulse P3 is the 3 rd pulse at the 4 th angle θ 4.

In the present example 3, in each of the groups Pg1 to Pg6, the 2 nd angle θ 2 and the 3 rd angle θ 3 are set to the same value, and the 1 st angle θ 1 and the 4 th angle θ 4 are set to different values. For example, the 1 st, 2 nd, 3 rd, and 4 th angles θ 1, θ 2, θ 3, and θ 4 of the leading group Pg1 are set to 0 °, 180 °, and 30 ° in this order. In the last group Pg6, 300 °, 120 °, and 330 ° are set in the same order.

As shown in fig. 17(B), in groups Pg1 to Pg5 other than the last group Pg6, it was determined that the current I was measured when the 1 st pulse P1 was applied and when the 4 th pulse P3 was applied. That is, in each of the groups Pg1 to Pg5, the current I was measured 2 times. In the last group Pg6, it was determined that the current I was measured 1 time only when the 1 st pulse P1 was applied.

According to example 3, the time required for initial position estimation can be shortened by the number of pulses smaller than that in example 2.

Fig. 19 shows an example 4 of the improved search procedure, and fig. 20 shows the configuration and operation of a burst PA4 according to example 4 of fig. 19.

the search performed in the order of example 4 is a search in which the burst PA4 shown in fig. 20 is applied. The number of pulses of the pulse train PA4 is 20, which is larger than 12, which is the number n of angles θ searched, but smaller than the above-described example 3. The pulse train PA4 includes pulses applied to reduce the displacement amount of the magnetic pole position PS in addition to the 12 pulses required for measuring the current I.

the burst PA4 is a burst in which 5 groups Pg1, Pg2, Pg3, Pg4, and Pg5, which are smaller than 12 as the number n of angles θ of search, are connected. These groups Pg1 to Pg5 are each composed of 4 pulses P1, P2a, P2b, and P3.

The pulse P1 is the 1 st pulse at the 1 st angle θ 1, and the pulses P2a, P2b are the 2 nd pulses at the 2 nd angle θ 2 or the 3 rd angle θ 3. And, the pulse P3 is the 3 rd pulse at the 4 th angle θ 4.

In the present example 4, the 2 nd angle θ 2 and the 3 rd angle θ 3 are set to the same value in each of the groups Pg1 to Pg 5. This point is the same as example 3. In the groups Pg1 to Pg4, the 1 st angle θ 1 and the 4 th angle θ 4 are set to different values, and in the group Pg5, the 1 st angle θ 1 and the 4 th angle θ 4 are set to the same value.

Specifically, the 1 st angle θ 1, the 2 nd angle θ 2, the 3 rd angle θ 3, and the 4 th angle θ 4 of the first to 3 rd groups Pg1 to Pg3 are set to the same values as in example 3 (see fig. 17). The 1 st angle θ 1, the 2 nd angle θ 2, the 3 rd angle θ 3, and the 4 th angle θ 4 of the 4 th group Pg4 are set to 210 °, 60 °, and 270 ° in this order. In the last group Pg5, it is set to 330 °, 150 °, and 330 ° in the same order.

As shown in fig. 19B, in the groups Pg1 to Pg3, the current I was determined to be measured when the 1 st pulse (P1) was applied, when one of the 2 nd pulses (P2B) was applied, and when the 3 rd pulse (P4) was applied. It is considered that when the pulse P2b to be applied later among the plurality of 2 nd pulses (P2a, P2b) is applied, the magnetic pole position PS is close to the original position, and therefore, it is preferable to perform measurement when the pulse P2b is applied.

In the group Pg4, it was determined that the current I was measured when the 1 st pulse (P1) was applied and when the 3 rd pulse (P4) was applied. In the last group Pg5, it was determined that the current I was measured when the 1 st pulse (P1) was applied.

according to example 4, the time required for initial position estimation can be shortened by the number of pulses smaller than that in example 3.

Fig. 21 shows an outline of a processing flow in the motor control device 21.

An input of a start command from the control circuit 100 is waited (# 101). When a start command is input (# 101: yes), an initial position estimation process is performed (#102), and motor drive control for rotating the motor 3 is performed (# 103). The control of the motor drive is continued until a stop command is input from the control circuit 100 (# 14).

According to the above embodiment, at the time of the initial position estimation, a large torque capable of reversely rotating the rotor 32 rotated by inertia can be generated by applying the pulse twice, instead of generating a large torque capable of reversely rotating the rotor 32 rotated by inertia by applying the pulse 1 time. This makes it possible to return to the original state even if the magnetic pole position PS is displaced in each group Pg of the pulse train PA, and to reduce the displacement amount of the magnetic pole position PS in the initial position estimation and improve the accuracy of the initial position estimation.

In the above-described embodiment, when the rotation based on the inertia of the magnetic field vector is stopped in a relatively short time, the application of the 3 rd pulse may be omitted, and the 1 st pulse and the plurality of 2 nd pulses may form each group Pg of the pulse train PA. In this case, the magnetic pole position PS displaced by the application of the 1 st pulse can be brought closer to the original position by the application of the 2 nd pulse, and the displacement amount of the magnetic pole position PS in the initial position estimation can be reduced. The pulse trains PA1 to PA4 also include pulses for reducing the displacement amount of the magnetic pole position PS, and are pulse trains for searching for the initial position as a whole.

In the above-described embodiment, the initial position estimating unit 25 may store the angle setting information 80 for specifying the searched angle θ, and the initial position estimating unit 25 may specify the angle θ to the speed control unit 41.

in the above-described embodiment, the number of the 2 nd pulses in each group Pg of the pulse train PA may be 3 or more. Specific values of the 1 st angle θ 1, the 2 nd angle θ 2, the 3 rd angle θ 3, and the 4 th angle θ 4 are determined to be effective for reducing the amount of displacement of the magnetic pole position PS in each group Pg, and are not limited to the illustrated values.

The configuration, content, sequence, or timing of the whole or each part of the image forming apparatus 1 and the motor control device 21, the pulse period H, the pulse width, and the like in the pulse train PA can be appropriately changed according to the spirit of the present invention.