Motor driving control device

Abstract

To respond to deterioration of motor grease or the like caused by fluctuations of the ambient temperature or long-term operation, thereby suppressing an actuation failure when conducting forced commutation actuation of a sensorless motor.SOLUTION: A motor driving control device 100 includes a forced commutation frequency control unit 8, a motor driving unit 4 including an oscillator 9 that can change an oscillation frequency by changing a capacitance value of a variable capacitance diode D1, and a voltage control unit 2 that generates voltage of a voltage value corresponding to a voltage setting signal and applies the generated voltage to the variable capacitance diode. The forced commutation frequency control unit 8 controls the voltage generated by the voltage control unit 2 variably and starts actuation on the basis of the ambient temperature and if the actuation fails, updates the forced commutation frequency and tries the actuation again. Thereafter, until the limit of a voltage changeable range of the voltage control unit 2 is reached, the voltage generated by the voltage control unit 2 is changed to update the forced commutation frequency. Actuating a sensorless motor is repeated until the actuation is successfully performed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a motor drive control device that controls, for example, forced commutation startup (forced commutation drive) of a sensorless motor. [Background technology]

[0002] Since a sensorless motor cannot detect the rotor position at start-up, a forced commutation start is performed when starting the motor, and then drive control is generally performed in which the induced voltage generated in the coil is used to transition to normal drive.

[0003] For example, Patent Document 1 states in paragraph

[0011] that "even if the frequency of the output signal CLK of the startup circuit is set to an optimal frequency, if it deviates from the optimal frequency due to factors such as variations in elements and temperature characteristics, problems may occur in which startup is not possible or startup takes too long."

[0004] For example, in

[0013] of Patent Document 1, as a countermeasure, it is described that "when starting a sensorless motor, the start-up phase switching frequency at which current is passed through the multiple-phase motor drive coils by the current control circuit is changed from a high frequency that the rotor rotation does not adequately follow to a low frequency, thereby starting the rotor rotation and starting the sensorless motor." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3263993 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 describes measures to be taken when the characteristics of the start-up circuit deviate from the optimal frequency due to variations in elements or variations in temperature characteristics, but startup failures can also occur due to fluctuations in the ambient temperature of the sensorless motor or deterioration of motor grease after long periods of operation. Patent Document 1 does not mention this point at all.

[0007] Patent Document 1 mentions a drive control that varies the starting phase switching frequency from a high frequency to which the rotor rotation does not sufficiently follow, to a low frequency. However, with this drive control, the starting phase switching frequency changes continuously over time.

[0008] Therefore, even if there exists a frequency during the frequency change that can respond to fluctuations in the ambient temperature of the sensorless motor or deterioration of motor grease, etc. due to long-term operation, that frequency is only realized for an instant, and it is thought to be difficult to stably start a sensorless motor in response to fluctuations in the ambient temperature or deterioration of motor grease, etc. due to long-term operation.

[0009] An object of the present invention is to be able to cope with deterioration of motor grease and the like due to fluctuations in ambient temperature and long-term operation when performing forced commutation startup of a sensorless motor, thereby suppressing startup failures.

[0010] Other objects of the present invention will become apparent to those skilled in the art by referring to the following exemplary aspects and best modes, as well as the accompanying drawings. [Means for solving the problem]

[0011] In order to facilitate an understanding of the outline of the present invention, embodiments according to the present invention will be exemplified below.

[0012] In a first aspect, a motor drive control device includes a forced commutation frequency control section that controls a forced commutation frequency when a sensorless motor is forced to be commutated and started up, a motor drive section that includes an oscillator capable of changing an oscillation frequency by changing a capacitance value of a variable capacitance diode, and that is capable of generating a forced commutation start signal of the forced commutation frequency based on an oscillation signal of the oscillator, to drive the sensorless motor, and a voltage control section that generates a voltage of a voltage value corresponding to a voltage setting signal supplied from the forced commutation frequency control section, and applies the generated voltage to the variable capacitance diode. By changing the voltage setting signal based on the ambient temperature, the voltage generated by the voltage control unit is variably controlled, and as a result, when the ambient temperature is low, the forced commutation frequency is set lower to set a longer forced commutation period compared to when the ambient temperature is high, and start-up is initiated. If start-up of the sensorless motor at the set forced commutation frequency fails, the forced commutation frequency is updated and a restart is attempted. If this second start-up attempt also fails, thereafter, the voltage generated by the voltage control unit is changed to update the forced commutation frequency until the limit of the voltage variable range of the voltage control unit is reached, and start-up of the sensorless motor is repeated until start-up is successful.

[0013] According to this aspect, the voltage applied to the variable capacitance diode can be variably controlled in response to the ambient temperature. Here, the following relationship exists between the applied voltage of the variable capacitance diode, the capacitance of the variable capacitance diode, the forced commutation frequency, and the forced commutation period. When the applied voltage to the variable capacitance diode (in other words, the reverse voltage or reverse voltage) is small, the depletion layer does not expand as much as when the applied voltage is large, so the distance between the electrodes of the capacitor becomes smaller, and therefore the capacitance (capacitance value) of the variable capacitance diode becomes larger.

[0014] Therefore, when the applied voltage to the variable capacitance diode is "small", the capacitance of the variable capacitance diode becomes "large", and when the capacitance of the variable capacitance diode is "large", the forced commutation frequency is set "low" and the forced commutation period is set "long". On the other hand, when the voltage applied to the variable capacitance diode is "large", the capacitance of the variable capacitance diode becomes "small", and when the capacitance of the variable capacitance diode is "small", the forced commutation frequency is set "high" and the forced commutation period is set "shorter". In other words, by variably controlling the voltage applied to the variable capacitance diode, it is possible to change the forced commutation frequency and appropriately vary the forced commutation period, thereby making it possible to respond to fluctuations in the ambient temperature and suppressing start-up failures.

[0015] In a second aspect dependent on the first aspect, the forced commutation frequency control unit may, when setting a forced commutation frequency and starting startup, set the forced commutation frequency lower if the ambient temperature is low compared to when the ambient temperature is high, and when updating the forced commutation frequency and attempting restart, perform a first restart process by lowering the voltage generated by the voltage control unit compared to when the previous restart was performed, and if the restart fails, repeat the first restart process, and if the voltage generated by the voltage control unit reaches a minimum value of a voltage variable range, return the voltage generated by the voltage control unit to a predetermined voltage value and increase the voltage generated by the voltage control unit based on the predetermined voltage value, thereby performing a second restart process, and if the restart fails, repeat the second restart process, and if the restart fails, cancel the second restart process if the voltage generated by the voltage control unit reaches a maximum value of a voltage variable range.

[0016] In the second mode, when the ambient temperature is low during start-up of the sensorless motor, the forced commutation frequency is set lower than when the ambient temperature is high. When the ambient temperature is low, the viscosity of the oil in the motor bearings increases, and the motor rotor's rotation speed tends to increase more slowly than when the temperature is high. Therefore, the voltage applied to the variable capacitance diode is reduced, the forced commutation frequency is lowered, and the forced commutation period is lengthened, thereby controlling the switching timing of the control current for the motor rotor and each of the motor's U, V, and W phases to suit the temperature environment. This can reduce start-up failures of the sensorless motor. Furthermore, when attempting a restart by updating the forced commutation frequency, it is possible that the cause of the failure of the previous startup may be that the grease in the motor bearings has deteriorated due to long-term operation, causing the motor rotor's rotational speed to slow down. Taking this into consideration, first, the voltage applied to the variable capacitance diode is reduced, the forced commutation frequency is lowered, and the forced commutation period is set to a longer period, and a restart (first restart process) is attempted.

[0017] If the restart is not successful even after repeated restarts and the applied voltage of the variable capacitance diode reaches the minimum value of the voltage variable range, it is possible that the failure to start is due to some cause other than, for example, grease deterioration, so the voltage is temporarily returned to a predetermined voltage (for example, the voltage at the first start of the current operation), and then the applied voltage is gradually increased from the predetermined voltage, the forced commutation frequency is increased, and the forced commutation period is set to a short period to attempt restart (second restart process).If the applied voltage of the variable capacitance diode reaches the maximum value of the voltage variable range, it means that startup has failed over the entire variable range of the applied voltage of the variable capacitance diode, so the restart attempt is stopped and a process such as a fault notification is carried out. According to the second aspect, even if startup fails, the variable range of the applied voltage of the variable capacitance diode is utilized as much as possible to appropriately change the applied voltage and attempt restart, thereby increasing the possibility of successful startup of the sensorless motor.

[0018] In a third aspect dependent on the first or second aspect, a plurality of the variable capacitance diodes may be connected in parallel, and a voltage commonly applied to the plurality of variable capacitance diodes may be generated by a digital potentiometer, or each of the voltages applied to each of the plurality of variable capacitance diodes may be generated by a multi-channel digital potentiometer.

[0019] According to the third aspect, by varying the capacitances of the multiple variable capacitance diodes in common or individually, it is possible to more finely control the switching of the load capacitance of the oscillator, thereby improving the accuracy of setting the forced commutation frequency.

[0020] In a fourth aspect dependent on any one of the first to third aspects, after the forced commutation start-up of the sensorless motor is successful, the forced commutation frequency control unit may store the ambient temperature and the forced commutation start-up success voltage at the current start-up in a database, and at the next or subsequent forced commutation start-up, the most recent past forced commutation start-up success voltage at the same ambient temperature as the ambient temperature at the time of the previous start-up may be used as the voltage to be applied to the variable capacitance diode.

[0021] In a fourth aspect, when the forced commutation start-up of the sensorless motor is successful, at least the ambient temperature and the forced commutation start-up success voltage are stored in the database. This "forced commutation start-up success voltage" includes the result of updating the applied voltage value of the variable capacitance diode after at least one failed start-up, and therefore reflects the fluctuation of the applied voltage value according to the degree of deterioration of the sensorless motor. Then, at the next or subsequent forced commutation start-up, the most recent successful forced commutation start-up voltage at the same ambient temperature as the start-up is used as the voltage to be applied to the variable capacitance diode, making it possible to set an appropriate applied voltage corresponding to the degree of deterioration of the sensorless motor.

[0022] In a fifth aspect dependent on any one of the first to fourth aspects, after successful forced commutation startup of the sensorless motor, the forced commutation frequency control unit may store in a database an accumulated operating time (taking temperature into consideration) obtained by multiplying the ambient temperature at the current startup and a temperature coefficient corresponding to the ambient temperature by the current operating time, and adding the accumulated operating time (taking temperature into consideration) obtained by adding the accumulated operating time (taking temperature into consideration) up to now, and a forced commutation startup success voltage, and may determine deterioration of the sensorless motor based on the accumulated operating time (taking temperature into consideration) at the time of the next or subsequent forced commutation startup, and variably control the applied voltage of the variable capacitance diode according to the degree of deterioration.

[0023] In the fifth aspect, the voltage applied to the variable capacitance diode is variably controlled in consideration of not only the ambient temperature but also the degree of deterioration of the sensorless motor. For example, in the fourth aspect above, the most recent applied voltage at the same ambient temperature is used, but in this aspect, for example, instead of using the most recent applied voltage as is, it is possible to use an applied voltage that is estimated to be more appropriate by taking into account the degree of deterioration of the sensorless motor. Therefore, for example, even if the deterioration of the grease of the sensorless motor becomes quite noticeable after long-term operation, it is possible to set a more appropriate forced commutation frequency (and forced commutation period) that corresponds to the situation. In addition, in this embodiment, the degree of deterioration of the sensorless motor is determined not by the accumulated value of the operating time but by the accumulated operating time (considering temperature). This accumulated operating time (considering temperature) is obtained by multiplying the current operating time by a temperature coefficient (a weighting coefficient indicating the degree of deterioration at that temperature) determined in response to the ambient temperature, and adding the product (in other words, the current operating time (considering temperature)) to the accumulated operating time (considering temperature) up to now. This makes it possible to more accurately determine the degree of deterioration of the sensorless motor. This improves the accuracy of setting (or updating) the applied voltage of the variable capacitance diode.

[0024] In a sixth aspect dependent on any one of the first to fifth aspects, the forced commutation frequency control unit, after successfully performing forced commutation startup of the sensorless motor, stores in a database an accumulated operating time (taking temperature into consideration) obtained by adding an operating time (taking temperature into consideration) obtained by multiplying an ambient temperature at this startup and a temperature coefficient corresponding to the ambient temperature by the current operating time, to an accumulated value of operating times (taking temperature into consideration) up to now, and a forced commutation startup success voltage, and when updating an applied voltage to the variable capacitance diode and attempting restart, may determine deterioration of the sensorless motor based on the accumulated operating time (taking temperature into consideration), and when the degree of deterioration is large, set a larger voltage fluctuation range in updating the applied voltage to the variable capacitance diode compared to when the degree of deterioration is small.

[0025] The sixth aspect has the same gist as the fifth aspect, except that while in the fifth aspect the applied voltage to the variable capacitance diode at "start-up" is varied according to the degree of deterioration of the sensorless motor, in the sixth aspect the applied voltage to the variable capacitance diode at "restart-up" is varied.

[0026] In the sixth aspect, when attempting to restart by updating the voltage applied to the variable capacitance diode, if it is determined that the degree of deterioration of the sensorless motor is large, it is considered that a slight change in the applied voltage is often insufficient to successfully restart, considering that the control sensitivity of a deteriorated motor has decreased. Therefore, taking this into consideration, the voltage fluctuation range (voltage update range) for each restart is set larger than when it is determined that the degree of deterioration is small, and restart is attempted. This increases the possibility of successful restart even when the sensorless motor is severely deteriorated.

[0027] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief description of the drawings]

[0028] [Figure 1]FIG. 1 is a diagram showing a general drive control method for a sensorless motor. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of the motor drive control device and the motor drive control section of the present invention. [Diagram 3] FIG. 3 is a diagram showing another example of the configuration of the motor drive control device of the present invention. [Figure 4] FIG. 4 is a diagram showing still another example of the configuration of the motor drive control device of the present invention. [Diagram 5] FIG. 5 is a diagram showing still another example of the configuration of the motor drive control device of the present invention. [Figure 6] FIG. 6 is a flowchart showing an example of a control procedure of the motor drive control device of the present invention. [Figure 7] FIG. 7A is a diagram showing an example of the correspondence relationship between the ambient temperature and the voltage applied to a variable capacitance diode, and FIG. 7B is a diagram showing an example of the correspondence relationship between the ambient temperature and a temperature coefficient. [Figure 8] FIG. 8 is a diagram showing an example of driving history information stored in the driving history database. [Figure 9] FIG. 9 is a diagram showing the effect of extending the operating life of a sensorless motor according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The best mode described below is used to easily understand the present invention. Therefore, those skilled in the art should be aware that the present invention is not unduly limited by the mode described below.

[0030] Please refer to Fig. 1. Fig. 1 is a diagram showing a general drive control method for a sensorless motor. The period from time t0 to t1 is a forced commutation period TA, during which forced commutation control is performed. The period from time t1 to t2 is a rotation speed transition period TB, during which TB (and the period after time t2) induced voltage control is performed.

[0031] At time t0, the rotation speed of the sensorless motor is RS, and at time t1, the rotation speed reaches the switching rotation speed RTth, and forced commutation startup is successful. At time t2, the rotation speed of the sensorless motor reaches the target rotation speed RTtg, and thereafter, this rotation speed RTtg is maintained.

[0032] If the rotation speed of the sensorless motor does not reach the switching rotation speed RTth within a specified period, forced commutation startup will fail. Possible causes of forced commutation startup failure include fluctuations in ambient temperature and deterioration of motor grease due to long-term operation, but with conventional sensorless motors, the load capacity of the oscillator is fixed, and it cannot be denied that it is sometimes difficult to flexibly respond to fluctuations in ambient temperature and deterioration of motor grease due to long-term operation.

[0033] In the present invention, the load capacitance of the oscillator is configured with a variable capacitance diode, and if forced commutation startup fails, the voltage applied to the variable capacitance diode (reverse voltage, reverse voltage) is changed to appropriately set the forced commutation frequency and forced commutation period, and an attempt is made to restart, thereby increasing the possibility of successful restart.

[0034] Next, reference is made to Fig. 2. Fig. 2 is a diagram showing an example of the configuration of a motor drive control device and a motor drive control section of the present invention. In A-1 of Fig. 2, a motor drive control device 100 that controls the drive of a sensorless motor 6 has a motor drive control section 1 configured with a microcomputer or the like, a voltage control section 2, a variable capacitance section 3, and a motor drive section 4.

[0035] The motor drive control unit 1 includes a forced commutation frequency control unit 8, and a non-volatile memory 116 that stores a temperature control database DB1 and an operation history database DB2. The forced commutation frequency control unit 8 controls the forced commutation frequency when the sensorless motor 6 is forced to be commutated and started. The forced commutation frequency control unit 8 can refer to a temperature control database DB1 and an operation history database DB2 as necessary (this will be described later).

[0036] The variable capacitance section 3 includes a variable capacitance diode D1 and a DC blocking capacitor C0.

[0037] The motor drive unit 4 includes an oscillator 9. This oscillator 9 is called a commutation oscillator in which a load capacitance constituting an oscillation circuit is provided outside the oscillator 9, and the above-mentioned variable capacitance diode D1 constitutes the load capacitance.

[0038] By changing the capacitance value of the variable capacitance diode D1, it is possible to change the oscillation frequency of the oscillator 9. When the oscillator 9 starts oscillating, the discharge current Ic and the charge current Id of the variable capacitance diode D1, which are AC signals, flow through the DC blocking capacitor C0.

[0039] The oscillator 9 oscillates, for example, a triangular wave signal by an oscillation operation, converts this triangular wave oscillation signal into a square wave by, for example, shaping the waveform, and also divides the oscillation signal to appropriately change the frequency, thereby generating a drive signal (including a forced commutation start signal) DR for the sensorless motor 6. The motor drive unit 4 drives the sensorless motor 6 by the generated drive signal DR.

[0040] The capacitance value of the variable capacitance diode D1 changes depending on the applied voltage (applied voltage, reverse voltage, or reverse voltage). A voltage control unit 2 is provided to variably control the capacitance of the variable capacitance diode D1. Based on a voltage setting signal VS supplied from a forced commutation frequency control unit 8, the voltage control unit 2 generates a voltage having a voltage value corresponding to the voltage setting signal VS, and applies the generated voltage to the variable capacitance diode D1. In this specification, the voltage applied to the variable capacitance diode is mainly referred to as the “applied voltage.” This “applied voltage” is a voltage that is generated by the voltage control unit 2 based on the voltage setting signal VS supplied from the forced commutation frequency control unit 8. In addition, if restart is successful after repeatedly changing the applied voltage and attempting to restart, the applied voltage may be described as the "forced commutation start-up success voltage."

[0041] Furthermore, the forced commutation frequency control unit 8 variably controls the voltage (applied voltage) generated by the voltage control unit 2 by changing the voltage setting signal VS based on the ambient temperature (sometimes simply referred to as temperature) TC of the sensorless motor 6 measured by the temperature sensor 5. As a result, when the ambient temperature TC is low, the forced commutation frequency is set lower than when the ambient temperature TC is high, thereby setting a longer forced commutation period and starting forced commutation startup.

[0042] Furthermore, if forced commutation frequency control unit 8 fails to start sensorless motor 6 at the set forced commutation frequency, it updates the forced commutation frequency (in other words, applied voltage) and attempts to restart it, and if this second start-up attempt also fails, it thereafter changes the voltage (applied voltage) generated by voltage control unit 2 to update the forced commutation frequency until the limit of the voltage variable range of voltage control unit 2 is reached, and repeats starting of sensorless motor 6 until start-up is successful.

[0043] The motor drive control unit (microcomputer or the like) 1 supplies a speed control signal VC, which is a control signal for the rotation speed of the motor, to the motor drive unit 4. The motor drive unit 4 also supplies a speed signal RP indicating the detected rotation speed of the motor to the motor drive control unit 1 (including the forced commutation frequency control unit 8).

[0044] Furthermore, after the forced commutation start-up is successful and the control shifts to induced voltage control, the induced voltage IDV of the sensorless motor 6 is supplied to the motor drive unit 4, and the motor drive unit 4 controls the phase of the drive signal DR based on this induced voltage IDV.

[0045] Next, A-2 in Fig. 2 is referred to. A-2 in Fig. 2 shows an example of a specific configuration of the motor drive control unit 1 shown in A-1 in Fig. 2. In A-2 in Fig. 2, the same parts as those in A-1 in Fig. 2 are denoted by the same reference numerals.

[0046] The forced commutation frequency control unit 8 in the motor drive control unit 1 includes an ambient temperature measurement unit 104, an applied voltage setting unit 106 (including a voltage change unit 107), a start-up / failure judgment unit 108 (including a start-up judgment unit 110 and a failure judgment unit 112), and an operation history database update unit 114.

[0047] The ambient temperature measuring unit 104 detects the ambient temperature based on the ambient temperature TC of the sensorless motor 6 measured by the temperature sensor 5 . The applied voltage setting unit 106 generates a voltage setting signal VS, and supplies the generated voltage setting signal VS to the voltage control unit 2 . When the voltage change unit 107 receives a notification signal indicating a startup failure from the startup determination unit 110 of the startup / failure determination unit 108, it changes the voltage value of the voltage setting signal VS by a predetermined value (predetermined voltage width) based on, for example, a predetermined rule. This changes the applied voltage, and the voltage change unit 107 attempts to start the sensorless motor 6 again with this applied voltage. A start-up determination unit 110 of the start-up / failure determination unit 108 determines the success / failure of the forced commutation start-up based on a speed signal RP indicating the rotation speed of the motor. In addition, the failure determination unit 112, for example, attempts to restart the device by changing the applied voltage as much as possible within the voltage variable range of the voltage control unit 2, and if restart is still not possible, it determines that a failure has occurred and performs processing such as notifying the user that a failure has occurred.

[0048] After the forced commutation startup is successful (for example, after operation ends), the operation history database update unit 114 updates the operation history database DB2 by storing predetermined information (operation history information) in the operation history database DB2. The operation history information may include, for example, the "date" when the operation was performed, the "operating time," the "ambient temperature," the "temperature coefficient (a weighting coefficient indicating the degree of deterioration at that temperature, and used to more accurately determine the degree of deterioration of the motor)," the "operating time (considering temperature)" obtained by multiplying the current operating time by the temperature coefficient, the "accumulated operating time (considering temperature)" obtained by adding the operating time (considering temperature) to the accumulated value of the operating time (considering temperature) up to now, and the "forced commutation start-up success voltage in the voltage control unit."

[0049] The information stored in the temperature control database DB1 included in the nonvolatile memory 116 may include the "applied voltage corresponding to the ambient temperature" and the above-mentioned "temperature coefficient." The "applied voltage corresponding to the ambient temperature" is a voltage applied to the variable capacitance diode D1 that corresponds to the ambient temperature when the forced commutation startup is performed.

[0050] In addition, this "applied voltage corresponding to the ambient temperature" may be automatically updated as needed based on the "ambient temperature" during the most recent operation and the "forced commutation start success voltage in the voltage control unit" corresponding to that ambient temperature, both stored in the operation history database DB2. Such automatic updating can be achieved by employing a database system that manages the two databases DB1 and DB2 in association with each other.

[0051] In this manner, when the applied voltage setting unit 106 attempts to start the sensorless motor 6 by adopting the most recent past forced commutation start-up success voltage at the same ambient temperature, it only needs to refer to the temperature control database DB1 and there is no need to refer to the operation history database DB2. This simplifies the start-up process and reduces the burden on the applied voltage setting unit 106. However, the above configurations (stored information) of the databases DB1 and DB2 are merely examples and are not limited to these.

[0052] Next, reference is made to Figs. 3 to 5. Fig. 3 is a diagram showing another example of the configuration of a motor drive control device of the present invention. Fig. 4 is a diagram showing yet another example of the configuration of a motor drive control device of the present invention. Fig. 5 is a diagram showing yet another example of the configuration of a motor drive control device of the present invention. In Figs. 3 to 5, parts common to Fig. 2 described above are given the same reference numerals.

[0053] In FIG. 3, the voltage control unit 2 in A-1 of FIG. 4, the variable capacitance section 3 in FIG. In the variable capacitance section 13, a plurality of variable capacitance diodes D1 to Dm (m is a natural number equal to or greater than 2) are connected in parallel. In addition, in FIG. 4, a voltage commonly applied to the plurality of variable capacitance diodes D1 to Dm is generated by a digital potentiometer 11. In addition, in FIG. 5, a multi-channel variable capacitance unit is configured by combining a plurality of variable capacitance diodes D1 to Dn (n is a natural number equal to or greater than 2) connected in parallel with a plurality of DC blocking capacitors C1 to Cn, and each variable capacitance unit is generated by a multi-channel digital potentiometer 17.

[0054] In the example of FIG. 3, the voltage control section can be easily realized by a digital potentiometer. In addition, in the examples of Figures 4 and 5, the capacitance of each of the multiple parallel-connected variable capacitance diodes can be varied either in common or individually, making it possible to more finely control the switching of the oscillator's load capacitance and improving the accuracy of setting the forced commutation frequency.

[0055] Next, reference is made to Fig. 6. Fig. 6 is a flow chart showing an example of a control procedure of the motor drive control device of the present invention.

[0056] Before starting the motor, first, the motor temperature is measured by a temperature sensor (step S1), and then the rotation speed during steady operation (during induced voltage control) is set (step S2).

[0057] Next, a voltage value of the applied voltage of the variable capacitance diode (in other words, the voltage generated by the voltage control unit 2) corresponding to the ambient temperature of the sensorless motor is set (step S3). At this time, the voltage control unit 2 can refer to the temperature control database DB1 and the operation history database DB2 as appropriate. In a preferred embodiment, the applied voltage of the variable capacitance diode can be determined by the "applied voltage corresponding to the ambient temperature" stored in the temperature control database DB1.

[0058] As described above, the forced commutation frequency is determined by the voltage applied to the variable capacitance diode (step S4), and this sets a forced commutation period of an appropriate length corresponding to the ambient temperature (motor temperature).

[0059] In other words, when the temperature is low, the viscosity of the oil in the motor bearings is higher than when the temperature is high, and the increase in rotational speed of the motor rotor is slower, so the forced commutation frequency is lowered and the forced commutation period is lengthened to match the switching timing of the control current for the motor rotor and each of the motor's U, V, and W phases. Since the capacitance of a variable capacitance diode increases when the applied voltage (reverse voltage) decreases, control is performed to lower the reverse voltage applied to the variable capacitance diode compared to when the motor temperature is high.

[0060] After the forced commutation frequency is set, the sensorless motor is started (step S5).

[0061] If the start-up is successful (Y in step S6), the process proceeds to step S16 and switches to induced voltage control. When the driving is completed (step S17), predetermined information is stored in the driving history database DB2 (step S18), and the driving history database DB2 is updated accordingly. A specific example of updating the driving history database DB2 will be described later with reference to FIG.

[0062] If startup fails (N in step S6), it is determined whether the applied voltage is minimum or not (step S7). If it is not minimum (N in step S7), the voltage value is reduced from the immediately previous applied voltage (step S8), thereby increasing the capacitance of the variable capacitance diode and lowering the forced commutation frequency, in other words, lengthening the forced commutation period (step S9), and startup is performed again.

[0063] Here, the process of attempting restart by lowering the voltage, for example, by a predetermined voltage width, from the immediately preceding applied voltage is referred to as a "first restart process."

[0064] The cause of the failure to restart is thought to be that the grease in the motor bearings has deteriorated due to long-term operation, causing the motor rotor's rotation speed to slow down. Taking this into consideration, first, the voltage applied to the variable capacitance diode is reduced, the forced commutation frequency is lowered, and the forced commutation period is set to a longer period, and restart (first restart process) is repeatedly attempted.

[0065] After step S9, the process returns to step S6 to determine whether or not the startup is successful. If the startup is successful (Y in step S6), the process proceeds to step S16, where induced voltage control is started.

[0066] On the other hand, if the answer is Y in step S7, this means that startup has failed even when the applied voltage has been minimized within the range in which it can be varied. In this case, the voltage is temporarily returned to a predetermined voltage (for example, the voltage at the initial startup of the current operation) (step S10).

[0067] Next, it is determined whether or not the applied voltage is the maximum voltage in the variable range (step S11).

[0068] If the applied voltage is not the maximum (N in step S11), the set voltage is increased above the above-mentioned predetermined voltage (step S12), thereby reducing the capacitance of the variable capacitance diode and increasing the forced commutation frequency, in other words, shortening the forced commutation period (step S13), and start-up is attempted again (step S14).

[0069] Here, the process of attempting restart by increasing the voltage value by a predetermined voltage width from the immediately preceding applied voltage is referred to as a "second restart process."

[0070] In this case, since it is possible that the startup has failed due to some cause other than, for example, grease deterioration, the applied voltage to the variable capacitance diode is temporarily returned to a predetermined voltage (for example, the voltage at the initial startup of the current operation), and then the applied voltage is gradually increased from that predetermined voltage, the forced commutation frequency is increased, the forced commutation period is set to a short value, and a restart (second restart process) is repeatedly attempted.

[0071] If the start-up is successful (Y in step S15), the process proceeds to step S16, where induced voltage control is started. Thereafter, when the driving ends (step S17), predetermined information is stored in the driving history database DB2 (step S18), and the driving history database DB2 is updated accordingly.

[0072] If the startup has failed (N in step S15), the process returns to step S11, where the applied voltage is increased and startup is attempted again.

[0073] If the answer is Y in step S11, it means that an attempt was made to change the applied voltage as much as possible within the variable range of the voltage and restart the device, but the restart was unsuccessful. In this case, the second start-up process is stopped, and the process proceeds to step S19 to notify the user of the failure (for example, a message indicating that a failure has occurred is displayed on the display).

[0074] In this way, according to the forced commutation startup method shown in FIG. 6, when starting up a sensorless motor, if the ambient temperature is low, the forced commutation frequency can be set lower than when the ambient temperature is high. This makes it possible to set an appropriate forced commutation frequency (forced commutation period) that suits the ambient temperature, and makes it possible to suppress start-up failures due to temperature.

[0075] Furthermore, even if startup fails, the variable range of the applied voltage of the variable capacitance diode is utilized as effectively as possible, the applied voltage is appropriately changed, and restart attempts are made as many times as possible, thereby increasing the possibility of successful startup of the sensorless motor.

[0076] Next, reference is made to Fig. 7. Fig. 7(A) is a diagram showing an example of the correspondence relationship between the ambient temperature and the voltage applied to a variable capacitance diode, and Fig. 7(B) is a diagram showing an example of the correspondence relationship between the ambient temperature and the temperature coefficient.

[0077] In FIG. 7A, for example, when the ambient temperature is 40° C., the voltage applied to the variable capacitance diode is 6.5V, and when the ambient temperature is 20° C., the voltage applied to the variable capacitance diode is 5.0V.

[0078] As explained above, when the ambient temperature is low, the viscosity of the oil in the motor bearings increases compared to when the temperature is high, and the increase in the rotation speed of the motor rotor tends to be slower. Therefore, the voltage applied to the variable capacitance diode is reduced, the forced commutation frequency is lowered, and the forced commutation period is lengthened, thereby controlling the switching timing of the control current for the motor rotor and each phase of the motor U, V, and W to suit the temperature environment. This makes it possible to reduce failures in starting up the sensorless motor. However, the applied voltage versus ambient temperature shown in Figure 7(A) is an example, and is not limited to this.

[0079] An example of a temperature coefficient for the ambient temperature is shown in Fig. 7(B). The temperature coefficient is a weighting coefficient that indicates how easily deterioration progresses at a given temperature, and is introduced to accurately evaluate the degree of deterioration of the motor.

[0080] For example, when the ambient temperature is 40°C, the temperature coefficient is 2.33, and when the ambient temperature is 20°C, the temperature coefficient is 1.00. The higher the ambient temperature, the more the deterioration of the motor grease will be accelerated. Therefore, when the temperature is high, the temperature coefficient value is larger than when it is low.

[0081] As described above, in this embodiment, the degree of deterioration of the sensorless motor is determined not by a simple accumulated value of the operation time but by the accumulated operation time (considering temperature). This accumulated operation time (considering temperature) is obtained by multiplying the current operation time by a temperature coefficient determined corresponding to the ambient temperature and adding the product (in other words, the current operation time (considering temperature)) to the accumulated operation time (considering temperature) up to now. By using the temperature coefficient, it is possible to obtain the accumulated operation time (considering temperature) as an index for more accurately determining the degree of deterioration of the sensorless motor. By determining the applied voltage of the variable capacitance diode taking this accumulated operation time (considering temperature) into consideration, it is possible to improve the accuracy of setting (or updating) the applied voltage.

[0082] Next, reference will be made to Fig. 8. Fig. 8 is a diagram showing an example of driving history information stored in the driving history database.

[0083] The operation history database DB2 stores (memorizes) operation history information. The operation history information includes the "date" when the operation was performed, the "operation time", the "ambient temperature", the "temperature coefficient (a weighting coefficient indicating the degree of deterioration at that temperature, and a coefficient used to more accurately determine the degree of deterioration of the motor)", the "operation time (considering temperature)" obtained by multiplying the current operation time by the temperature coefficient, the "accumulated operation time (considering temperature)" obtained by adding the operation time (considering temperature) to the accumulated value of the operation time (considering temperature) up to now, and the "forced commutation start-up success voltage".

[0084] In the example of Figure 8, attention is focused on the driving history information for "January 10, 2021", "January 11, 2021", "January 10, 2023", and "January 11, 2023". (1) In the operation history information for January 10, 2021, the operation time is "8h", the ambient temperature is "5℃", the temperature coefficient is "0.50", the operation time (considering temperature) is "4h", the cumulative operation time (considering temperature) is "1500h", and the forced commutation start-up success voltage of the voltage control unit is "4.0V". (2) In the operation history information for January 11, 2021, the operation time is "4h", the ambient temperature is "10℃", the temperature coefficient is "0.67", the operation time (considering temperature) is "2.7h", the cumulative operation time (considering temperature) is "1502.7h", and the forced commutation start-up success voltage of the voltage control unit is "4.5V". (3) In the operation history information for January 10, 2023, the operation time is "8h", the ambient temperature is "5℃", the temperature coefficient is "0.50", the operation time (considering temperature) is "4h", the cumulative operation time (considering temperature) is "6000h", and the forced commutation start-up success voltage of the voltage control unit is "3.5V". (4) In the operation history information for January 11, 2023, the operation time is "4h", the ambient temperature is "10°C", the temperature coefficient is "0.67", the operation time (considering temperature) is "2.7h", the cumulative operation time (considering temperature) is "6002.7h", and the forced commutation start-up success voltage of the voltage control unit is "4.0V".

[0085] Here, we compare (1) and (2) above. The operation dates of (1) and (2) differ by only one day, and there is almost no difference in the accumulated operation time (considering temperature). However, the forced commutation drive control voltage is 4.0V in (1), while it has risen to 4.5V in (2). This is thought to be due to the difference in ambient temperature. The ambient temperature in (1) is 5°C, while in (2) it has risen to 10°C.

[0086] As explained above, when the ambient temperature is low, the viscosity of the oil in the motor bearings increases and the rotational speed of the motor rotor tends to increase more slowly than when the temperature is high. For this reason, it is preferable to set the voltage applied to the variable capacitance diode to a low value. Taking this into consideration, the forced commutation start-up set voltage in (1) above is set lower than in (2).

[0087] As described above, according to this embodiment, an appropriate voltage is set in accordance with the ambient temperature, so that forced commutation startup can be achieved that flexibly responds to changes in ambient temperature and with fewer failures.

[0088] Furthermore, according to this embodiment, it is possible to flexibly deal with deterioration of the motor. Now, let us compare (1) and (3) above. The ambient temperature is 5°C in both cases. However, the cumulative operating time (taking temperature into account) is 1500h in (1), whereas it has increased to 6000h in (3). Therefore, it is believed that the motor has deteriorated considerably in the case of (3) compared to the case of (1).

[0089] However, the motor also started successfully in (3). This is because the forced commutation start-up success voltage in (1) was 4.0 V, but in (3) the forced commutation start-up success voltage was updated to 3.5 V (0.5 V lower than in (1)) in response to the motor deterioration.

[0090] Also, compare (2) and (4) above. The ambient temperature is 10°C in both. However, the cumulative operating time (considering temperature) is 1502.7h in (2), while it has increased to 6002.7h in (4). Therefore, it is believed that the motor has deteriorated considerably in the case of (4) compared to the case of (2).

[0091] However, the motor also started successfully in (4). This is because the forced commutation start-up success voltage in (2) was 4.5 V, but in (4) the forced commutation start-up success voltage was updated to 4.0 V (0.5 V lower than in (2)) in response to the motor deterioration.

[0092] In this way, according to this embodiment, it is possible to realize forced commutation startup with fewer failures, taking into consideration not only the ambient temperature but also the degree of deterioration of the motor.

[0093] As described above, the information on the "forced commutation start-up success voltage" corresponding to the ambient temperature in the operation history database DB2 is reflected in the temperature control database DB1. Specifically, when the latest data on the "forced commutation start-up success voltage" corresponding to the ambient temperature is obtained, this latest data may be overwritten on the data on the set voltage at the same temperature in the temperature control database DB1.

[0094] The forced commutation frequency control unit 8 shown in A-1 of Fig. 2 can refer to the temperature control database DB1 when performing forced commutation startup of the sensorless motor, and can adopt the most recent forced commutation startup set voltage at the same temperature (in other words, the most recent overwritten set voltage) as the set voltage for the current startup. However, this is just one example, and the present invention is not limited to this example.

[0095] For example, when performing forced commutation startup of a sensorless motor, the forced commutation frequency control unit 8 attempts to use the most recent past successful forced commutation startup voltage at the same temperature, but it may be assumed that the most recent past data is somewhat old and the current motor is in a state where it has deteriorated further. In this case, the forced commutation frequency control unit 8 can also autonomously set a set voltage suited to the current degree of deterioration of the motor, based on the current accumulated operating time (taking temperature into consideration).

[0096] It is also possible to change the amount of change in the set voltage at restart based on the accumulated operating time (considering temperature).In other words, when updating the voltage applied to the variable capacitance diode and attempting restart, if it is determined that the degree of deterioration of the sensorless motor is large, it is likely that a slight change in the applied voltage will be insufficient to successfully restart the motor, considering that the control sensitivity of a deteriorated motor has decreased. In consideration of this, the forced commutation frequency control unit 8 may attempt restart by setting the voltage fluctuation range (voltage update range) for each restart to be larger than when the degree of degradation is determined to be small. This increases the chances of successful restart even if the sensorless motor is severely deteriorated.

[0097] As described above, according to this embodiment, by variably controlling the set voltage in response to at least one of the change in ambient temperature and the degree of deterioration of the motor, it is possible to realize forced commutation start-up and restart with fewer failures.

[0098] Next, reference is made to Fig. 9. Fig. 9 is a diagram showing the effect of extending the operating life of a sensorless motor according to the present invention. In Fig. 9, the horizontal axis represents the accumulated operating time (temperature time), and the vertical axis represents the applied voltage of the variable capacitance diode. In the example of Fig. 9, the ambient temperature is assumed to be 20°C (room temperature: standard temperature). The initially set applied voltage when the ambient temperature is 20°C is assumed to be "5.0V" following the example of Fig. 7(A).

[0099] In the period from time t100 to t200, forced commutation startup is successful at the initially set applied voltage of 5.0 V.

[0100] However, after time t200, deterioration of the motor becomes evident, and as a result, the voltage at which forced commutation start-up is successful gradually decreases over time.

[0101] At time t300, forced commutation start-up fails. In the conventional technology, the forced commutation frequency cannot be varied, so the operating life of the sensorless motor is the time from time t100 to t200. In contrast, in the present invention, forced commutation startup can be successfully achieved even during the period from t200 to t300 by changing the voltage applied to the variable capacitance diode. Therefore, according to this embodiment, the operating life can be extended by the time t200 to t300 compared to the conventional case.

[0102] In this way, according to this embodiment, the inherent characteristics of the sensorless motor can be fully utilized to extend the operating life as much as possible. Sensorless motors are also used, for example, to control various parts of a vehicle, and it is said that the number of sensorless motors used in electric vehicles will increase. Effectively extending the operating life of each sensorless motor also contributes to improving the reliability of the system in which the sensorless motor is used.

[0103] Thus, according to the present invention, when a sensorless motor is forced to start up through commutation, it is possible to cope with deterioration of motor grease and the like caused by fluctuations in ambient temperature and long periods of operation, thereby preventing start-up failures.

[0104] The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, the number of variable capacitance diodes used can be freely changed. Also, after one operation is completed, more diverse information can be stored in a database to be used for the next start-up.

[0105] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art could easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0106] 1···Motor drive control unit (microcomputer or the like), 2···Voltage control unit, 3···Variable capacitance unit, 4···Motor drive unit, 5···Temperature sensor, 6···Sensorless motor (motor), 8···Forced commutation frequency control unit, 11···Digital potentiometer, 17···Multi-channel digital potentiometer, 104···Ambient temperature measurement unit, 106···Applied voltage setting unit, 107···Voltage changing unit, 108···Startup / failure judgment unit, 110···Startup judgment unit, 112... Fault determination section, 114... Operation history database update section, 116... Nonvolatile memory, D1 to Dm (Dn)... Variable capacitance diodes, C0 to Cn... DC blocking capacitors, DB1... Temperature control database, DB2... Operation history database, VS... Voltage setting signal, VC... Speed ​​control signal, DR... Drive signal (including forced commutation start signal), IDV... Induced voltage, TC... Ambient temperature (temperature), and RP... Speed ​​signal.

Claims

1. a forced commutation frequency control unit that controls a forced commutation frequency when a sensorless motor is started with forced commutation; a motor drive unit including an oscillator capable of changing an oscillation frequency by changing a capacitance value of a variable capacitance diode, and capable of driving the sensorless motor by generating a forced commutation start signal having the forced commutation frequency based on an oscillation signal of the oscillator; a voltage control unit that generates a voltage having a value corresponding to a voltage setting signal supplied from the forced commutation frequency control unit, and applies the generated voltage to the variable capacitance diode; having The forced commutation frequency control unit includes: The voltage control unit variably controls the voltage generated by changing the voltage setting signal based on the ambient temperature of the sensorless motor, and thereby, when the ambient temperature is low, the forced commutation frequency is set lower than when the ambient temperature is high, thereby setting a longer forced commutation period and starting the motor; if the start-up of the sensorless motor at the set forced commutation frequency fails, the forced commutation frequency is updated and a restart is attempted, and if the second restart also fails, thereafter, the voltage generated by the voltage control unit is changed to update the forced commutation frequency until the limit of the voltage variable range of the voltage control unit is reached, and the start-up of the sensorless motor is repeated until the start-up is successful. Motor drive control device.

2. The forced commutation frequency control unit includes: When starting the inverter with a forced commutation frequency set, if the ambient temperature is low, the forced commutation frequency is set lower than if the ambient temperature is high; If you want to update the forced commutation frequency and try restarting, A first restart process is performed by lowering the voltage generated by the voltage control unit compared to the voltage generated at the previous restart, and if the restart fails, the first restart process is repeatedly performed, and if the voltage generated by the voltage control unit reaches a minimum value of a voltage variable range, the voltage generated by the voltage control unit is returned to a predetermined voltage value; Using the predetermined voltage value as a reference, the voltage generated by the voltage control unit is increased to perform a second restart process; If the restart fails, the second restart process is repeatedly performed, and if the voltage generated by the voltage control unit reaches a maximum value of a voltage variable range, the second restart process is stopped. The motor drive control device according to claim 1 .

3. A plurality of the variable capacitance diodes are connected in parallel, and a voltage to be commonly applied to the plurality of variable capacitance diodes is generated by a digital potentiometer; Or, Each of the voltages applied to each of the plurality of variable capacitance diodes is generated by a multi-channel digital potentiometer. The motor drive control device according to claim 1 .

4. The forced commutation frequency control unit includes: After the forced commutation start of the sensorless motor is successful, the ambient temperature and the forced commutation start success voltage at this start are stored in a database, and At the next or subsequent forced commutation start-up, the previous forced commutation start-up success voltage at the same ambient temperature as the start-up is set as the voltage to be applied to the variable capacitance diode. The motor drive control device according to claim 1 .

5. The forced commutation frequency control unit includes: After the forced commutation start of the sensorless motor is successful, The ambient temperature at this startup and The cumulative operating time (considering temperature) is obtained by adding the operating time (considering temperature) obtained by multiplying the current operating time by the temperature coefficient corresponding to that ambient temperature to the cumulative value of the operating time (considering temperature) up to now. Forced commutation start success voltage, is stored in the database, At the next or subsequent forced commutation start-up, deterioration of the sensorless motor is judged based on the accumulated operating time (taking temperature into consideration), and the applied voltage of the variable capacitance diode is variably controlled according to the degree of deterioration. The motor drive control device according to claim 1 .

6. The forced commutation frequency control unit includes: After the forced commutation start of the sensorless motor is successful, The ambient temperature at this startup and The cumulative operating time (considering temperature) is obtained by adding the operating time (considering temperature) obtained by multiplying the current operating time by the temperature coefficient corresponding to that ambient temperature to the cumulative value of the operating time (considering temperature) up to now. Forced commutation start success voltage, is stored in the database, When attempting to restart the device by updating the applied voltage to the variable capacitance diode, Deterioration of the sensorless motor is determined based on an accumulated operating time of the temperature consideration method, and when the degree of deterioration is large, a voltage fluctuation range in updating the applied voltage of the variable capacitance diode is made larger than when the degree of deterioration is small. The motor drive control device according to claim 1 .

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