Electronic control unit

Abstract

Electronic control unit with: - a motor (10) having a rotor (12) which rotates by receiving a supply of an electric current to a plurality of power supply phases; - an encoder (20) which outputs a pulse-shaped encoder signal synchronously with a rotation of the rotor (12); - a controller (40) that controls the ON and OFF of the supply of electric current to the plurality of phases based on a change in the encoder signal; and - a speed range determination unit (30) which determines in which of an acceleration range, a constant speed range and a deceleration range the rotation of the rotor (12) is currently located, wherein - the controller (40) delays an OFF-time phase at an OFF-time of supplying the electric current with respect to a change point of the encoder signal when the rotation of the rotor (12) is in the delay range to cause a counter force in a reverse direction with respect to a rotation direction of the rotor (12).

Description

[0001] The present invention generally relates to an electronic control unit that switches the power supply phases of a motor and rotates the rotor to a target position.

[0002] In a shift-by-wire system (i.e., shifting by electrical impulse) in a vehicle, a gear change of the vehicle is carried out by feeding an electric current in accordance with an operation of the driver to several power supply phases of the motor to control the motor which enables the gear change (i.e., the change of the gear range).

[0003] To achieve the responsiveness and accuracy of the shifting operation that best matches the driver's operation, the motor must be rotated at high speed and decelerated safely. To achieve such precise and responsive motor control, the electric power supply to each of the multiple phases must be precisely controlled. The accuracy of the power supply control by the drive circuit is subject to certain limitations due to the characteristics of the components in the drive circuit that outputs the drive signal to the inverter, as well as the characteristics of the inverter itself and the ambient temperature.

[0004] JP 2004-23931 A discloses a motor control device that introduces the concept of "speed-sensitive phase advance correction" Ks, which describes an advance of the power supply phase with respect to a current position of the rotor, thereby enabling variable adjustment of the phase advance Ks in accordance with the rotor speed. That is, a correction amount Ks of the phase advance of the power supply phase with respect to the rotation phase of the rotor is correctable in accordance with a rotation state of the rotor. For example, a small correction amount Ks is used in the initial rotation period of the rotor to achieve higher torque and thus improve acceleration performance, and subsequently, the correction amount Ks is increased as the rotor speed increases to achieve stable rotation of the rotor.

[0005] However, in the motor controller control scheme according to JP 2004-23931 A, the small correction amount Ks is used in the speed reduction range, i.e., when the rotor speed is reduced. Consequently, high-accuracy rotor positioning to a target position is only achieved when a sufficiently long speed reduction range can be reserved. More specifically, a "long" time is required to stop the rotor rotation in such a control scheme. That is, the motor controller control scheme according to JP 2004-23931 A does not provide sufficient responsiveness for deceleration control. This is because it is difficult to find a circuit component that can provide both a sharp increase in the electric current for acceleration (of the motor) and a sharp decrease in the electric current for deceleration.

[0006] DE 44 47 027 A1 discloses an iron core motor device with an iron core motor for rotating a rotor by switching (commutating) the phase in a power supply to a plurality of excitation coils and a control method therefor.

[0007] It is an object of the present invention to provide an electronic control unit which can provide high responsiveness in deceleration control of the motor without impairing a stop position accuracy of the rotor.

[0008] The problem is solved by the subject matter of the main claim. Advantageous further developments are specified in the subclaims.

[0009] According to the present invention, since the electric current drop is delayed relative to a power OFF (i.e., a power OFF) to the power supply phase compared to the conventional control, a counterforce, i.e., a stopping force for stopping the rotation of the rotor, is generated in a direction opposite to the rotation direction of the rotor. Consequently, idle rotation of the rotor is prevented, and a higher angular deceleration relative to the rotation deceleration is generated.

[0010] Accordingly, a time for stopping the rotation of the rotor rotating in the constant speed region is shortened. That is, the time of the deceleration region is shortened. More specifically, the responsiveness of the deceleration is improved according to the control scheme of the present invention.

[0011] The objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings: Fig. 1 is a block diagram showing a configuration of an electronic control unit according to a first embodiment of the present invention; Fig. 2 a front view of a stator and part of a rotor; Fig. 3 a front view of part of an encoder; Fig. 4 is a flowchart of an operation of an electronic control unit at the time of a change in an encoder signal; Fig. 5 a conversion table linking a current position of the rotor, a phase advance correction amount, and a power supply phase to which an electric current is supplied; Fig. 6 is a timing diagram relating to control by the electronic control unit; Fig. 7 is a flowchart showing the operation of the electronic control unit after the expiration of a delay timer; Fig. 8 is a diagram illustrating a force applied to the rotor; Fig. 9 a graph of the rotor speed over time; and Fig. 10 is a timing chart relating to control by the electronic control unit according to a second embodiment of the present invention.

[0012] Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, like / equivalent parts are designated by the same reference numerals. (First embodiment)

[0013] With reference to the Fig. 1 to 3, a configuration of the electronic control unit of the present embodiment is described.

[0014] An electronic control unit is a device installed in a vehicle that controls the shifting of an automatic transmission. More specifically, an electronic control unit is installed in a shift-by-wire vehicle in which the shifting or shift range is changed by controlling a stepping motor from an electronic control unit (ECU) (i.e., a controller), i.e., a motor controller, in accordance with a range-shifting operation of a driver of the vehicle.

[0015] As in Fig. 1, an electronic control unit 100 includes a motor 10 serving as part of an automatic transmission, an encoder 20 outputting a pulse-shaped signal synchronous with the rotation of the motor 10, a speed range determining unit 30 determining a speed range of rotation of the motor 10, and a controller 40 provided as an electronic control unit (ECU). The controller 40 controls the drive of the motor 10 via a drive circuit 50 that supplies electric power to the motor 10.

[0016] The electronic control unit 100 is electrically connected to a shift control unit 200, which is operated by the driver. The shift control unit 200 detects the driver's range shift operation and outputs range information about a shift range desired by the driver to the controller 40.

[0017] The electronic control unit 100 is mechanically connected to a transmission 400 that changes a torque and speed to transmit the power of an internal combustion engine 300 to the wheel

[0018] The transmission 400 changes a combination of gears that mesh with each other by the power of the engine 10 to change a power transmission path that transmits the power of the internal combustion engine 300. That is, the gear change is performed by the power of the engine 10.

[0019] As for the motor 10 in the present embodiment, the stepping motor (ie, a switched reluctance motor: SR motor) is used. As shown in Fig. 2, a stator 11 and a rotor 12 in the motor 10 are each provided with salient poles, allowing the permanent magnets to be distributed, thus enabling a simpler structure. For example, twelve salient poles 11a are formed on the inner circumference of the cylindrical stator 11 at equal intervals, and, on the other hand, eight salient poles 12a are formed on the outer circumference of the rotor 12 at equal intervals.

[0020] A salient pole 12a of the rotor 12 approaches or comes close to a salient pole 11a of the stator 11 as the rotor 12 rotates, and the poles 11a, 12a are opposed to each other at a small distance. More practically, the salient pole 11a with a U-phase winding 13 would then approach a salient pole 12a, then approach the next pole 11a with a V-phase winding 13, and then approach the next pole 11a with a W-phase winding 13 as the rotor 12 rotates. The number of salient poles 11a on the stator 11 and the number of salient poles 12a on the rotor 12 can be changed as appropriate.

[0021] When the electric current flows to the winding 13, a magnetic flux is generated within the energized salient pole 11a of the stator 11, and the pole 11a is magnetized. Now, the salient pole 12a of the rotor 12 is attracted close to the magnetized salient pole 11a, and the rotor 12 rotates. For example, when the electric current is supplied to the U-phase, the V-phase, and the W-phase in this order, the rotor 12 rotates in a view of the Fig. 2 clockwise.

[0022] The encoder 20 is implemented as a magnetic type rotary encoder. More precisely, as shown in Fig. 3, a circular rotary magnet 21 is arranged on the rotor 12, in which N and S poles are arranged at equal intervals and at equal widths (i.e., with an equal pitch angle) along the circular shape of the magnet 21. The rotary magnet 12 is arranged coaxially with the rotor 12 for rotation with the rotor 12. The pitch angle of the N / S poles on the rotary magnet 21 is set to 7.5 degrees in the present embodiment.

[0023] The encoder 20 has magnetism detection elements 22 and 23, such as a Hall element, at the position opposing the rotating magnet 21.

[0024] The magnetism detecting element 22 outputs an A signal as the encoder signals (SIG. A in the Fig. 3). On the other hand, the magnetism detection element 23 outputs a B signal as the encoder signal (SIG. B in the Fig. 3).

[0025] The encoder signal output from each of the magnetism detection elements 22 and 23 assumes an H value (high value or high level value) when each of the magnetism detection elements 22 and 23 opposes the N pole of the rotary magnet 21, and an L value (low value or low level value) when each of the elements 22 and 23 opposes the S pole. That is, every 7.5 degrees of rotation of the rotor 12 and the rotary magnet 21, the encoder signal is periodically output as high or low.

[0026] The magnetism detection element 22 and the magnetism detection element 23 are spaced apart by 48.75 degrees in the rotation direction of the rotor 12.

[0027] Consequently, the phase difference between the A signal and the B signal is 3.75 degrees as a rotation angle of the rotor 12. More specifically, with respect to the A signal, the B signal is output with a phase delay of 1 / 4 period.

[0028] The encoder 20 outputs the A signal and the B signal to the controller 40. The controller 40 counts the change points, ie, the rising / falling edges, of the A / B signals to detect the rotation angle of the rotor 12 and switches the power supply phase, ie, into which of the U / V / W phase the electric current is supplied.

[0029] Since the phase difference between the A signal and the B signal, as described above, is 3.75 degrees as the rotation angle of the rotor 12, the rotor 12 rotates 3.75 degrees during one count of the encoder signal. The encoder signals count up when the rotor 12 rotates forward and count down when the rotor 12 rotates reversely. Consequently, based on an initial count value of the encoder 20, the current position of the rotor 12 is uniquely detected based on the current count value.

[0030] The speed range determining unit 30 determines a speed range based on an angle difference X between the rotation angle of the current position of the rotor 12 and the rotation angle of the target position.

[0031] The speed range can be described more practically as either an acceleration range in which the angular difference X is greater than or equal to a predetermined threshold value P (i.e., X ≥ P), a constant speed range in which X is greater than or equal to a threshold value Q and less than the predetermined threshold value P (i.e., Q ≤ X < P), or a deceleration range in which X is less than the threshold value Q (i.e., X < Q).

[0032] The speed range determining unit 30 determines the speed range based on the relationship between the angle difference X and the threshold values P and Q. When determining the speed range, each of the values X, P, and Q can be treated as the rotation angle of the rotor 12 or as the number of encoder signal counts with respect to the rotor 12, since the rotation angle and the encoder signal counts are tied to a one-to-one relationship.

[0033] Furthermore, the speed range can be determined by detecting an angular acceleration with respect to the rotation of the motor 10.

[0034] When the angular acceleration of the rotor 12 is positive and the rotation of the rotor 12 is accelerating, the speed range is defined as the acceleration range. When the angular acceleration of the rotor 12 is zero and the angular velocity of the rotor 12 is nearly constant, the speed range is defined as the constant speed range. When the angular acceleration of the rotor 12 is negative and the rotation of the rotor 12 is decreasing, the speed range is defined as the deceleration range.

[0035] Specifically, the speed range determination unit 30 determines that the speed range is the acceleration range when a count-up interval or a count-down interval of the A signal decreases over time, for example, or that the speed range is the deceleration range when the count-up interval or the count-down interval of the A signal increases over time. When the count-up interval or the count-down interval of the A signal is constant, the speed range is determined as the constant speed range.

[0036] The encoder signal output by the encoder 20 is used to detect the current position of the rotor 12 and the angular acceleration of the rotor 12. The speed range determination unit 30 determines which of the speed ranges the rotor 12 is currently in and transmits the information indicating the determined speed range to the controller 40.

[0037] The controller 40 is, for example, a shift-by-wire ECU. The controller 40 controls the inverter that forms the drive circuit 50. The drive circuit 50 is configured to supply electric power to each of the U / V / W phases based on commands from the controller 40. The controller 40 calculates the rotational speed of the rotor 12 based on the encoder signal output from the encoder 20. Then, the controller 40 determines the power supply phase to which the electric power is supplied based on the rotational speed range and the rotational speed of the rotor 12 input by the rotational speed range determination unit 30. If the electric power is supplied without considering phase lead correction, the count pulse or count value of the encoder signal reaches 1 after one cycle of phase switching orof the phase change from U-phase → UV-phase → V-phase → VW-phase → W-phase → WU-phase → U-phase 12, and the rotor 12 rotates by 45 degrees. Furthermore, in the present embodiment, the controller 40 is configured to control the drive circuit to delay the OFF timing of supplying the electric power to the power supply phase, that is, to enable the OFF timing to be delayed from the normal OFF timing. Such control by the controller 40 will be described in more detail below.

[0038] The drive circuit 50 is a three-phase drive inverter circuit of known design. The drive circuit 50 includes three pairs of inverter circuits (not shown), and each of the inverter circuits supplies electric power to the U-phase, V-phase, and W-phase based on commands from the controller 40.

[0039] Below, with reference to the Fig. 4 - 7, the control of the electronic control unit 100 of the present embodiment is described. The flowchart shown in the Fig. 4 occurs when the encoder signal changes, a power supply command value is output which instructs the controller 40 into which of the power supply phases the electrical current is to be fed.

[0040] As in Fig. 4, step S1 is performed first. Step S1 is a step in which the controller 40 detects the rotational speed of the rotor 12. Although the encoder 20 outputs the encoder signal, a transition between high and low of the encoder signal occurs every phase difference of 7.5 degrees. Since the encoder signal in the present embodiment includes the A signal and the B signal, and the phase difference between the A signal and the B signal is 3.75 degrees, the angular difference between the previous change point of the encoder signal and the current change point of the encoder signal is detected as 3.75 degrees. That is, while one edge of the encoder signal is counted, the rotor 12 rotates by 3.75 degrees. The controller 40 detects the angular velocity, that is, the rotational speed, based on the delay between the detection of the previous change point of the encoder signal and the detection of the current change point of the encoder signal.

[0041] Next, step S2 follows. Step S2 is a step in which the speed range determination unit 30 determines the speed range of the rotor 12. As described above, the speed ranges include the acceleration range, the constant speed range, and the deceleration range. The speed range determination unit 30 determines the speed range based on the angular difference X between the rotation angle of the current position of the rotor 12 and the rotation angle of the target position.

[0042] The speed range determining unit 30 determines that the speed range is the acceleration range when the angular difference X is greater than the predetermined threshold value P (X ≥ P). Further, the speed range determining unit 30 determines that the speed range is the constant speed range when the angular difference X is greater than or equal to the threshold value Q and less than the predetermined threshold value P (Q ≤ X < P). When the angular difference X is less than the threshold value Q (X < Q), the speed range is determined to be the deceleration range.

[0043] Step S3 then follows.

[0044] Step S3 is a step in which the controller 40 calculates a phase advance correction amount Ks. The phase advance correction amount Ks is calculated based on the rotational speed of the rotor 12 calculated in step S1 and the rotational speed range of the rotor 12 calculated (ie, determined) in step S2.

[0045] To generate the torque that drives the rotor 12, it is necessary to advance the power supply phase with respect to the rotation phase of the rotor 12. Since the rate of change of the number of count pulses of the encoder signal edge increases as the rotation speed of the rotor 12 increases after the start of driving the rotor 12, the switching timing of the power supply phase also becomes faster, ie, it advances further.

[0046] When the rotational speed of the rotor 12 becomes high, there is a possibility that the drive torque will drop because the switching timing of the power supply phase cannot keep up with the rotation of the rotor 12. To solve this problem, the controller 40 controls, in advance, the power supply phase to advance the rotational phase of the rotor 12 depending on the rotational speed and speed range of the rotor 12. The amount of advance depends on the rotational speed and speed range. This amount of advance is the phase advance correction amount Ks.

[0047] Although the phase advance correction amount Ks is an angle value measured by a unit angle of 7.5 degrees, the amount Ks can be converted into the number of counts (ie, the count value) in the present embodiment.

[0048] The phase advance correction amount Ks assumes a large value as the rotational speed of the rotor 12 increases. Furthermore, the controller 40 controls the phase advance correction amount Ks to increase over time when the rotor 12 is in the acceleration range. Conversely, the controller 40 controls the phase advance correction amount Ks to decrease when the rotor 12 is in the deceleration range. Regarding the calculation of the phase advance correction amount Ks, reference is made to JP 2004-23931 A.

[0049] Step S4 then follows.

[0050] Step S4 is a step that determines the power supply phase into which the controller 40 supplies the electrical current.

[0051] The controller 40 determines the power supply phase based on a conversion table contained in the Fig. 5, as well as a current position N (i.e., the number of counting pulses) and the phase advance correction amount Ks (i.e., the number of counting pulses) of the rotor 12.

[0052] In the present embodiment, when the supply of electric current to the power supply phase has completed a cycle, such as from U-phase → UV-phase → V-phase → VW-phase → W-phase → WU-phase, the number of counting pulses either increases or decreases by 12. Consequently, the surplus or remainder resulting from dividing a sum M, which is an addition of the current position N and the phase advance correction amount Ks (ie, M = N + Ks), by a divider 12 serves as a factor that determines the power supply phase. In the Fig. 5 such an excess or remainder is called M mod 12.

[0053] The power supply phase determined in step S4 is used as a power supply command value (U i , Vi , W i ) is calculated. The power supply command value is set to 1 when electric power supply to a specific phase is instructed, and set to zero when electric power supply is not instructed.

[0054] For example, if M mod 12 = 3, then (Ui, V i , W i ) = (0, 0, 1). According to another example, if M mod 12 = 8, (Ui, V i , W i ) = (1, 1, 0).

[0055] Then step S5 takes place.

[0056] Step S5 is a step in which the controller 40 determines whether the speed range of the rotor 12 is the deceleration range. Based on the speed range information input from the speed range determination unit 30, the controller 40 determines in step S5 whether the rotor 12 is in the deceleration range or whether the rotor 12 is in the acceleration range or the constant speed range.

[0057] If the determination in step S5 is YES (ie, if the rotor 12 is in the deceleration region), the process proceeds to step S6.

[0058] Step S6 is a step in which the controller 40 calculates the power supply phase in which the OFF timing of the supply of the electric power is delayed.

[0059] Since the OFF timing is synchronous with the edge of the encoder signal when the OFF timing is not delayed, a delay of the OFF timing means that the phase is delayed with respect to the OFF timing of supplying the electric current to the power supply phase from the change point (ie, the edge) of the encoder signal.

[0060] Referring to the previous power supply phase before the phase switching and the current power supply phase calculated in step S4, the controller 40 determines the phase in which the command value has changed from 1 → 0 as a delayed power supply phase to which the supply of the electric power will be delayed.

[0061] For example, assuming that the previous power supply phases are the U phase and the V phase, that is (U i-1 , V i-1 , W i-1) = (1, 1, 0), and further assume that the current power supply phase calculated in step S4 is the V phase, ie (Ui, V i , W i ) = (0, 1, 0), the controller 40 selects the U phase as the delayed power supply phase in which the OFF time of supplying the electric power is delayed, since the power supply phase in which the command value has changed from 1 → 0 is the U phase.

[0062] Step S7 then follows.

[0063] Step S7 is a step in which the controller 40 calculates the delay time of the OFF timing in the power supply phase, which is calculated in step S6. That is, step S7 is a step in which the amount of phase delay of the OFF timing in the delayed power supply phase with respect to the edge of the encoder signal is calculated. It should be noted that the delay time corresponds to the amount of phase delay because the encoder signal depends on the rotational speed of the rotor 12, and the delay time is converted based on the rotational speed of the rotor 12.

[0064] The delay time (ie the amount of phase delay) is determined with reference to the Fig. 6 described.

[0065] Fig. Figure 6 shows a timing chart illustrating (i) the A signal and the B signal each describing the encoder signal, (ii) the command value of each of the power supply phases, and (iii) the change of the electric current flowing to each of the power supply phases.

[0066] The solid line shows a curve after delaying the phase of the OFF time, and the dashed line shows a curve of the conventional control in which the phase delay does not occur.

[0067] Fig. 6 shows, for ease of understanding, an example in which the phase advance correction amount is not applied.

[0068] Based on the assumption in step S6, the previous power supply phases are the U phase and the V phase, and the current power supply phase is the V phase. The power supply phase in which the phase delay of the OFF time of electric power supply occurs is the U phase.

[0069] In such a case, as in Fig. As shown in Figure 6, the start of the drop of the electric current flowing to the U phase is delayed in conjunction with the phase delay of the power supply command value in the U phase. Consequently, before the electric current flowing to the U phase drops to zero, the supply of electric current in the W phase, which is the first power supply phase, starts at an ON time after the OFF time in another phase, that is, which is the phase at which the electric current starts to flow.

[0070] That is, an interval between the drop in the supply of electric current in the U phase at the OFF time and the rise in the supply of electric current in the W phase at the ON time is shortened. More specifically, the drop in the U phase and the rise in the W phase overlap each other. The situation can also be described as determining / controlling the amount of phase lag such that (i) a drop in the supply of electric current at the OFF time in one phase and (ii) an increase in the supply of electric current at a first ON time in another phase after the OFF time in one phase have a smaller interval or overlap each other.

[0071] Consequently, the amount of phase delay depends on a rate of change in the decay of the electric current or on the value of the electric current at the time of starting the decay.

[0072] Here, the rate of change of the electric current depends on the reactance and the resistance of the winding 13 wound around the salient pole 11a of the stator 11. Furthermore, the value of the electric current at the time of starting the drop in the supply of the electric current depends on a power supply voltage that supplies the electric current to the winding 13.

[0073] Consequently, based on the reference values, that is, based on a certain reactance and resistance value of the winding 13 and a certain power supply voltage, a reference phase delay amount θ is determined in advance.

[0074] That is, the delay time (ie, the amount of phase delay) calculated in step S7 is equivalent to the amount θ of the reference phase delay under the conditions described above, that is, based on a reference reactance and a reference resistance value of the winding 13 and a reference power supply voltage.

[0075] Then, under such a condition, an interval between (i) a decrease in the supply of the electric current at the OFF time in one phase and (ii) an increase in the supply of the electric current at an ON time in another phase is shortened, or the time points of (i) and (ii) overlap each other.

[0076] Hereinafter, the situation is described by way of example as an overlap control by the controller 40 to cause an overlap between a decrease in the supply of the electric current at the OFF time in one phase and an increase in the supply of the electric current at an ON time in another phase.

[0077] As described above, the rate of change of the electric current depends on the reactance and resistance of the winding 13, and the time for the electric current to drop to zero depends on the power supply voltage. Therefore, in step S7, a correction amount δθ is preferably applied to the phase delay amount.

[0078] The rate of change increases as the temperature of the winding 13 increases, i.e., the temperature of the motor 10 increases, resulting in a shorter fall time of the electric current for the electric current to fall to zero. Consequently, the controller 40 determines the amount of phase delay to have a large value by setting δθ > 0 under conditions where the temperature of the motor 10 is above a reference value. In this way, the fall in the electric current supply at the OFF time in one phase and the rise in the electric current supply at the first ON time in the other phase after the OFF time in one phase are controlled so that both overlap with each other.

[0079] The fall time of the electric current, that is, a time required for the electric current flowing through the winding 13 to fall to zero, becomes shorter as the power supply voltage is lower. Consequently, the controller 40 determines the amount of phase delay to have a large value by setting δθ > 0 under the conditions where the power supply voltage is below a reference value. In this way, the increase in the supply of the electric current is caused at the first ON time in the other phase after the OFF time in one phase, before the fall in the supply of the electric current reaches zero at the OFF time in one phase.

[0080] Further, in order to set the OFF timing of the delayed power supply phase, which is delayed with respect to a change point of the encoder signal, ie, set to a point which is before, ie, ahead of the next change point of the encoder signal, the amount of the phase delay may have any upper limit.

[0081] This is because if the amount of phase delay extends beyond the next change point of the encoder signal, the supply pattern of the electric current may be desynchronized and the operation of the motor 11 may become erroneous.

[0082] In the present embodiment, the controller 40 may preferably determine δθ such that a condition of θ + δθ < 3.75 degrees is satisfied.

[0083] Since the change in the encoder signal depends on the rotational speed of the rotor 12, the amount of phase delay can be converted into the delay time. That is, the controller 40 can preferably set the delay time of the OFF time for the power supply command value to decrease to zero before the rotor 12 rotates an angle of 3.75 degrees.

[0084] Step S8 then follows.

[0085] Step S8 is a step in which the controller 40 sets a delay timer using a known timer circuit provided in the controller 40 based on the delay time calculated in step S7. The supply of electric power to the power supply phase for which the command value has changed from 1 → 0 continues until the current delay timer expires. In the example described above, the supply of electric power to the U phase continues.

[0086] Then step S9 follows.

[0087] Step S9 is a step in which the controller 40 calculates the power supply command values (U j , V j , W j ), which take into account the phase delay of the OFF time, calculates and outputs.

[0088] The power supply command value taking the phase delay into account is calculated as a logical sum of the previous power supply command values (U i-1 , V i-1 , W i-1 ) and the current power supply command values (Ui, V i , W i ) provided. That is, (U j , V i , W j ) = (U i-1 | U i , V i-1 | V i , W i-1 | W i ).

[0089] In the example described above, since (U i-1 , V i-1 , W i-1 ) = (1, 1, 0) and (Ui, V i , W i ) = (0, 1, 0), thus (Uj , V i , W j ) = (1, 1, 0). In this way, the output of the previous power supply command value is essentially continued, that is, left unchanged. It should be noted that the power supply command values calculated in step S9 are valid until the delay timer ends.

[0090] Consequently, as described above, when the rotor 12 is in the deceleration region, the power supply command values (U j , V j , W j ) taking the phase delay into account from the controller 40 and the drive circuit 50 is operated based on the power supply command values.

[0091] On the other hand, if the rotor 12 is in the acceleration region or the constant speed region, the determination in step S5 is NO. If the determination in step S5 is NO, as shown in Fig. 4, step S10.

[0092] Step S10 is a step in which the controller 40 calculates the current power supply command values (U i , V i , W i ) calculated in step S4. Subsequently, the drive circuit 50 is operated based on the current power supply command value. That is, the power supply phase is switched without performing the phase delay from the OFF time.

[0093] Now, when the delay timer set in step S8 ends, the controller 40 outputs the power supply command values in accordance with the time set in the Fig. 7. That is, step S11 occurs.

[0094] Step S11 is a step in which the controller 40 calculates the current power supply command values (U i , V i , W i) calculated in step S4. Subsequently, the drive circuit 50 is operated based on the current power supply command values. That is, under the condition that the delay timer ends, the phase delay of the OFF timing is terminated, and the supply of electric power to the desired power supply phase is carried out.

[0095] The operational effects of the electronic control unit 100 of the present embodiment will be described below.

[0096] For example, assuming that the power supply phase transition occurs in the sequence UV phase → V phase → VW phase, the following effects are achieved. That is, when the power supply phase transitions from the UV phase to the V phase, the attractive force from the electric current supply in the U phase disappears due to the OFF of the electric current supply in the U phase, and the salient pole 12a of the rotor 12 is attracted by the attractive force caused by the electric current supply in the V phase. As a result, the rotor 12 rotates.

[0097] In the present embodiment, when the rotation of the rotor 12 is in the deceleration range, by delaying the OFF timing of the electric power supply in the U phase with respect to the conventional power supply phase switching, the attractive force is maintained at a time point where the conventional attractive force has already been reduced due to the electric power supply in the U phase. Consequently, the angular acceleration of the rotor 12 is increased with respect to the rotation deceleration.

[0098] Specifically, in the present embodiment, the drop in the supply of electric current supplied to the U-phase and the subsequent increase in the supply of electric current in the W-phase overlap each other. As a result, the attractive force caused by the supply of electric current in the U-phase is still maintained, that is, is continuously exerted, in a period in which the supply of electric current is caused only in the V-phase. Consequently, in a period of V-phase power supply, a counterforce opposite to the rotation direction of the rotor 12 is securely exerted on the rotor 12 in a continuous manner. Consequently, a time for stopping the rotation of the rotor 12 is shortened.

[0099] The conventional drive control method of the rotor 12 can, by introducing the phase advance correction amount, reduce a time for accelerating the rotor 12, that is, shorten a time for increasing the rotational speed of the rotor 12 from the acceleration region to the constant speed region, thereby potentially improving the responsiveness to the shift change according to the driver's operation. In contrast, in the deceleration region, the conventional drive control method can only reduce the rotational speed of the rotor 12 by simply reducing the phase advance correction amount to zero.

[0100] However, in the present embodiment, the electronic control unit 100 effectively maintains the attraction force to delay the OFF time of supplying the electric current to the power supply phase, so as to enable the reduction of the time for rotating the rotor 12 by the same amount as in the Fig. 9. That is, in the present embodiment, the responsiveness to the driver's operation in the deceleration range is improved.

[0101] Furthermore, although in the present embodiment, an example is described in which the fall of the electric current with respect to the OFF of the electric power supply in one phase and the rise of the electric current with respect to the first ON in another power supply phase overlap with each other after the OFF time in one phase, such an overlap is not necessarily required.

[0102] Since a counter force opposite to the rotational direction of the rotor 12 is caused by delaying the drop in the supply of the electric current with respect to the OFF of the supply of the electric current with respect to the conventional OFF timing, the decelerating angular acceleration for reducing the rotational speed of the rotor 12 is increased in this way. (Second embodiment)

[0103] When the power supply command value is changed from 1 → 0 at the OFF time of supplying the electric current to the power supply phase, the change rate of the falling of the electric current flowing to the power supply phase becomes controllable with sufficient accuracy by performing the PWM control of the power supply command value.

[0104] The elements in the electronic control unit 100 are the same as those in the first embodiment, and the control such as the calculation of the rotational speed of the rotor 12, the determination of the rotational speed range, the calculation of the power supply phase that delays the OFF timing, and the like are also the same as those in the first embodiment. Therefore, repeated reference will not be made to them in the present embodiment.

[0105] The controller 40 of the present embodiment uses a different output method for outputting the power supply command value in the power supply phase in which the OFF timing is delayed than the output method in the first embodiment.

[0106] As in Fig. 10, the controller 40 in the present embodiment outputs the power supply command value by executing the PWM control during a delay timer action period. Fig. 10 shows a delay in the U-phase OFF timing when a UV-phase power supply state transitions to a V-phase power supply state. As the electric current supply curve, a solid line represents the electric current behavior in the present embodiment, and a dashed line represents the electric current behavior in the first embodiment.

[0107] As described in the first embodiment, the delay of the OFF time of the U phase means that the delay timer set in step S8 of the Fig. 4 is effective. During the period in which the delay timer is effective, the controller 40 in the present embodiment performs the PWM control of the power supply command values entirely for such a period or for a part of such a period.

[0108] In the Fig. 10, during a W-phase delay period in the U-phase power supply time, the W-phase power supply command value is PWM controlled. Similarly, during a U-phase delay period in the V-phase power supply time, the U-phase power supply command value is PWM controlled.

[0109] According to the above description, compared with the case where the power supply command value is designed to change from 1 → 0, the change speed of the electric current falling can be controlled very accurately without using the PWM control.

[0110] The above effects can be understood as an ability to perform high-precision control of the attractive force that reverses the rotation of the rotor 12, that is, the time to stop the rotation of the rotor 12 as well as the stop position of the rotor 12 are controllable with high accuracy according to the invention. (Other embodiments)

[0111] Although the present invention has been described above with reference to its embodiments, it can be modified in various ways without being limited to the embodiments described above.

[0112] In each of the above-described embodiments, although the number of salient poles 11a in the stator 11 is described as 12 and the number of salient poles 12a in the rotor 12 is described as 8, the number of salient poles may be other than 12 or 8. Furthermore, the pitch of the poles on the rotary magnet 21 in the encoder 20 is also not limited to 7.5 degrees. Moreover, although the number of power supply phases is three, that is, U / V / W phase, in each of the above-described embodiments, the number of power supply phases is not limited to three.

[0113] Furthermore, although the rotational speed of the rotor 12 in step S1 of the Fig.4 is detected, based on the encoder signal, the speed of the rotor 12 can be detected separately by another sensor without using the encoder 20.

[0114] In the same way, the determination of the speed range in step S2 can be carried out separately by the rotation angle sensor or the like.

[0115] Furthermore, in the second embodiment, although the power supply command value is described as being PWM controlled during a part of the delay timer operating period in the PWM control, such PWM control of the power supply command value may be performed entirely during the delay timer operating period.

[0116] Furthermore, although the second embodiment does not address the duty ratio during the PWM control, the duty ratio may be reduced with increasing time for the substantially linear decrease of the electric current for the OFF control of the power supply phase, so as to enable the highly accurate speed reduction control of the rotor 12.

Claims

[1] Electronic control unit with: - a motor (10) having a rotor (12) which rotates by receiving a supply of an electric current to a plurality of power supply phases; - an encoder (20) which outputs a pulse-shaped encoder signal synchronously with a rotation of the rotor (12); - a controller (40) that controls the ON and OFF of the supply of electric current to the plurality of phases based on a change in the encoder signal; and - a speed range determination unit (30) which determines in which of an acceleration range, a constant speed range and a deceleration range the rotation of the rotor (12) is currently located, wherein - the controller (40) delays an OFF-time phase at an OFF-time of supplying the electric current with respect to a change point of the encoder signal when the rotation of the rotor (12) is in the delay range to cause a counter force in a reverse direction with respect to a rotation direction of the rotor (12). [2] Electronic control unit according to claim 1, characterized by that the controller (40) provides overlap control by delaying the OFF-time phase of the supply of the electric current with respect to the change point of the encoder signal, the overlap control being effected between a drop in the supply of the electric current at the OFF-time in one phase and an increase in the supply of the electric current at an ON-time in another phase, the ON-time being observed as a first after the OFF-time in the one phase. [3] Electronic control unit according to claim 1 or 2, characterized by that the controller (40) controls an amount of supply of the electric current in the OFF-time phase with respect to the drop in the supply of the electric current by pulse width modulation control at the OFF time of supply of the electric current. [4] Electronic control unit according to one of claims 1 to 3, characterized by that the OFF time of supply of the electric current delayed with respect to the change point of the encoder signal is set to a point which is before a next change point of the encoder signal. [5] Electronic control unit according to one of claims 1 to 4, characterized bythat the lower a power supply voltage feeding the electric current into each of the plurality of phases, the higher an amount of delay of the OFF timing phase determined by the controller (40) with respect to the change point of the encoder signal. [6] Electronic control unit according to one of claims 1 to 5, characterized by that the higher a motor temperature is, the higher an amount of delay of the OFF timing phase determined by the controller (40) with respect to the change point of the encoder signal is.

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