Electric motor drive device and electric pump device

Abstract

The present invention provides a driving device for an electric motor and an electric pump device that can detect a step-out in a plurality of rotation speed regions while suppressing structural complexity. The driving device (100) for the electric motor (110) is a driving device (100) for the electric motor (110) that does not have a position detection sensor, and comprises: a driving unit (20) that drives the electric motor (110) according to a command value input from the outside; a rotation speed detection unit (13) that detects the rotation speed of the electric motor (110) driven by the driving unit (20); and a step-out judgment unit (15) that judges that the electric motor (110) is out of step when the rotation speed detected by the rotation speed detection unit (13) is less than a predetermined threshold value. Furthermore, the predetermined threshold value is changed according to the command value input from the outside.

Description

Technical Field

[0001] The present invention relates to an electric motor drive device and an electric pump device having no position detection sensor, and in particular to an electric motor drive device and an electric pump device having a step-out determination unit for determining whether the electric motor is losing step. Background Art

[0002] Conventionally, there is known a control device for a brushless motor that includes a step-out determination unit for determining that the electric motor is out of step, but does not include a position detection sensor (see, for example, Patent Document 1).

[0003] The control device of the brushless motor described in the above-mentioned patent document 1 has an abnormality detection mechanism (out-of-step judgment unit) that judges that the brushless motor is abnormal based on the condition that the axis error exceeds a predetermined reference value. Here, "axis error" refers to the axis deviation angle between the dq axis, which is the rotating coordinate axis, and the imaginary dq axis in control, when the magnetic flux axis of the brushless motor is used as the d axis and the axis orthogonal to the d axis is used as the q axis. Specifically, in the above-mentioned patent document 1, the axis error is calculated using a predetermined formula based on the voltage command value, the current value, the rotation speed and the brushless motor constant. Then, based on the condition that the axis error exceeds a predetermined reference value, the brushless motor is judged to be abnormal.

[0004] In the case of a brushless motor, if the shaft error is within the range of ±90 degrees, the brushless motor is stable. In the case of weak magnetic field control, the shaft error is controlled within the range of ±60 degrees. Therefore, in the above-mentioned Patent Document 1, it is configured to be judged as abnormal when the shaft error exceeds ±60 degrees.

[0005] In addition, in a brushless motor without a position detection sensor, the position of the rotor is detected based on the induced voltage generated in the brushless motor. However, if the rotation speed of the brushless motor is relatively low, the induced voltage of the brushless motor is not generated (or the induced voltage is weak), so the position of the brushless motor (rotor) cannot be detected. Therefore, in the area where the rotation speed of the brushless motor is relatively low, there is a possibility of step loss (the rotor rotates in a state that is not synchronized with the input command value). In addition, even in the area where the rotation speed of the brushless motor is relatively high, there is a possibility of step loss due to a sudden change in the rotation speed of the rotor. In the above-mentioned patent document 1, the axis error is calculated based on the voltage command value. Therefore, it is considered that not only the step loss in the area where the rotation speed of the brushless motor is relatively low (the area where the duty cycle of the voltage command value is small), but also the step loss in the area where the rotation speed of the brushless motor is relatively high (the area where the duty cycle of the voltage command value is large) is detected. That is, it is considered that in the above-mentioned patent document 1, it is configured to be able to detect step loss in the area of ​​the rotation speed of multiple brushless motors.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-60781

[0007] However, the control device for the brushless motor described in the above-mentioned patent document 1 determines the abnormality (loss of step, etc.) of the brushless motor in the region of multiple rotation speeds, and therefore the shaft error must be calculated by a prescribed formula based on the voltage command value, the current value, the rotation speed, and the brushless motor constant. Here, generally, in order to detect the current value, an amplifier for amplifying the signal of the detected current is required. Therefore, in the structure described in the above-mentioned patent document 1, there is a problem that the structure for detecting the abnormality of the brushless motor becomes relatively complicated. Summary of the invention

[0008] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an electric motor drive device and an electric pump device capable of detecting step-out in a plurality of rotation speed ranges while suppressing complexity of the structure.

[0009] In order to achieve the above-mentioned purpose, the driving device of an electric motor according to the first aspect of the present invention is a driving device of an electric motor without a position detection sensor, wherein the device comprises: a driving unit, which drives the electric motor according to a command value input from the outside; a rotation speed detection unit, which detects the rotation speed of the electric motor driven by the driving unit; and a step-out judgment unit, which judges that the electric motor is losing step when the rotation speed detected by the rotation speed detection unit is less than a prescribed threshold value, and is configured so that the prescribed threshold value is changed according to the command value input from the outside.

[0010] In the driving device of the electric motor of the first aspect of the present invention, as described above, there is a step-out judgment unit, which judges that the electric motor is out of step when the rotation speed detected by the rotation speed detection unit is less than a predetermined threshold value, and is configured so that the predetermined threshold value is changed according to the command value input from the outside. In this way, the predetermined threshold value is changed according to the command value input from the outside, so that the step-out can be detected in the region of multiple command values ​​(i.e., rotation speed) according to the predetermined threshold value corresponding to the command value. In addition, the step-out is judged only based on the rotation speed (whether the rotation speed is less than the predetermined threshold value), so unlike the case where the current value is used in addition to the rotation speed in the judgment of the step-out, it is not necessary to set an amplifier for detecting the current value. Therefore, it is possible to detect the step-out in the region of multiple rotation speeds while suppressing the complexity of the structure. In addition, by comparing the rotation speed detected by the rotation speed detection unit with the predetermined threshold value (whether the rotation speed is less than the predetermined threshold value), it is judged whether the step-out has occurred, so it is not necessary to calculate by a relatively complex formula. Therefore, it is possible to suppress the load of the driving device from increasing.

[0011] In the electric motor drive device of the above-mentioned first aspect, it is preferably constructed that the specified threshold value includes a first threshold value when the command value input from the outside is greater than the specified value, and a second threshold value smaller than the first threshold value when the command value input from the outside is less than the specified value, and the specified threshold value is selected as one of the first threshold value and the second threshold value according to the command value input from the outside.

[0012] If configured in this way, when the command value input from the outside is greater than a predetermined value (a relatively high rotation speed region), it is possible to easily determine whether the electric motor is losing step by comparing the rotation speed detected by the rotation speed detection unit with the first threshold value. In addition, when the command value input from the outside is less than a predetermined value (a relatively low rotation speed region), it is possible to easily determine whether the electric motor is losing step by comparing the rotation speed detected by the rotation speed detection unit with the second threshold value.

[0013] In the electric motor driving device according to the first aspect, it is preferable that, when the step-out determination unit determines that the electric motor is losing step, a voltage command to the electric motor is stopped to stop the electric motor.

[0014] According to this configuration, when it is determined that the electric motor is losing synchronism, the electric motor is stopped. Therefore, it is possible to suppress the continuation of driving the electric motor in a state where the electric motor is losing synchronism.

[0015] In this case, it is preferable that the electric motor in a stopped state is restarted when the step-out determination unit determines that the electric motor is stepping out of step.

[0016] Here, generally, when the electric motor stops, the rotor stops at a predetermined position due to the magnetic field of the permanent magnet. And by restarting the electric motor with the rotor stopped at the predetermined position, the electric motor can be started while preventing the loss of step.

[0017] The electric pump device of the second aspect of the present invention comprises: an electric pump, which is driven by an electric motor without a position detection sensor; and a driving device of the electric motor, the driving device of the electric motor includes: a driving unit, which drives the electric motor according to a command value input from the outside; a rotation speed detection unit, which detects the rotation speed of the electric motor driven by the driving unit; and a step-out judgment unit, which judges that the electric motor is losing step when the rotation speed detected by the rotation speed detection unit is less than a prescribed threshold value, and is configured so that the prescribed threshold value is changed according to the command value input from the outside.

[0018] In the electric pump device of the second aspect of the present invention, as described above, the driving device of the electric motor driving the electric pump is provided with a step-out judgment unit, which judges that the electric motor is stepping out when the rotation speed detected by the rotation speed detection unit is less than a predetermined threshold value, and is configured so that the predetermined threshold value is changed according to the command value input from the outside. In this way, the predetermined threshold value is changed according to the command value input from the outside, so that the step-out can be detected in the region of multiple command values ​​(i.e., rotation speed) according to the predetermined threshold value corresponding to the command value. In addition, the step-out is judged only according to the rotation speed (whether the rotation speed is less than the predetermined threshold value), so unlike the case where the current value is used in addition to the rotation speed in the judgment of the step-out, it is not necessary to set an amplifier for detecting the current value. Therefore, it is possible to provide an electric pump device that can detect the step-out in the region of multiple rotation speeds while suppressing the complexity of the structure. In addition, by comparing the rotation speed detected by the rotation speed detection unit with the predetermined threshold value (whether the rotation speed is less than the predetermined threshold value), it is judged whether the step-out has occurred, so it is not necessary to calculate by a relatively complicated formula. Therefore, it is possible to provide an electric pump device that can suppress the load of the driving device from increasing.

[0019] That is, in the electric motor driving device of another structure of the present application, the command value input from the outside is a duty ratio corresponding to the target rotation speed of the electric motor. If it is configured in this way, the step-out is caused by the rotation speed of the electric motor, so the prescribed threshold value for judging the step-out can be appropriately selected according to the command value input from the outside. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a block diagram of an electric motor driving device (electric pump device) according to an embodiment.

[0021] Figure 2 This is a diagram showing the relationship between an input instruction and a predetermined threshold value for determining whether or not a step-out occurs according to one embodiment.

[0022] Figure 3 This is a flowchart for explaining the operation of the electric motor driving device according to one embodiment.

[0023] Description of reference numerals:

[0024] 13 ... rotation speed detection unit; 15 ... step-out determination unit; 20 ... driving unit; 100 ... driving device; 110 ... electric motor; 200 ... electric pump device; 210 ... electric pump. DETAILED DESCRIPTION

[0025] Next, embodiments of the present invention will be described with reference to the drawings.

[0026] Reference Figure 1 as well as Figure 2The structure of the driving device 100 (electric pump device 200) of the electric motor 110 according to the present embodiment will be described. The electric motor 110 is a DC brushless motor that does not include a position detection sensor.

[0027] like Figure 1 As shown, the electric pump device 200 is configured to be driven by the electric motor 110. The electric pump device 200 is, for example, an electric water pump device for cooling an inverter.

[0028] The drive device 100 includes an IC (integrated circuit) 10. A command value is input to the IC 10. Specifically, the command value is a duty ratio (%) corresponding to a target rotation speed of the electric motor 110.

[0029] In addition, the IC 10 includes a power supply voltage correction unit 11. The voltage of the power supply supplied to the IC 10 is input to the power supply voltage correction unit 11. In addition, there is a case where the voltage of the power supply supplied to the IC 10 varies. Therefore, the power supply voltage correction unit 11 is configured to output a signal related to the correction to the output PWM duty calculation unit 12 in such a manner that the variation of the voltage of the power supply supplied to the IC 10 does not affect the rotation speed of the electric motor 110.

[0030] The IC 10 also includes an output PWM duty calculation unit 12. The output PWM duty calculation unit 12 is configured to generate a PWM signal based on an input command value and a signal related to correction output from the power supply voltage correction unit 11.

[0031] In addition, the drive device 100 includes a drive unit 20. The drive unit 20 is configured to drive the electric motor 110 according to a command value input from the outside. Specifically, the drive unit 20 drives a switching element (not shown) inside the drive unit 20 according to a PWM signal output from the output PWM duty calculation unit 12. Therefore, the electric motor 110 is driven at a desired rotation speed.

[0032] Furthermore, the drive device 100 includes a position detection unit 30 . The position detection unit 30 is configured to detect (estimate) the position of a rotor (not shown) based on an induced voltage generated in the electric motor 110 .

[0033] In addition, IC10 includes a rotation speed detection unit 13. The rotation speed detection unit 13 is configured to detect (estimate) the rotation speed of the rotor based on the position of the rotor (not shown) detected (estimated) by the position detection unit 30. In addition, the rotation speed of the rotor detected by the rotation speed detection unit 13 is output to the outside of IC10.

[0034] In addition, IC10 includes a threshold determination unit 14. The threshold determination unit 14 is configured to determine a threshold value (rotation speed) for determining whether the electric motor 110 is out of step. Here, in the present embodiment, the predetermined threshold value is changed according to a command value (duty ratio (%)) input from the outside. Specifically, Figure 2 As shown, the prescribed threshold value includes a first threshold value when the command value input from the outside is greater than a prescribed value, and a second threshold value that is smaller than the first threshold value when the command value input from the outside is less than the prescribed value. For example, the prescribed value of the command value (duty cycle) is 30%. For example, the first threshold value is 800rpm. For example, the second threshold value is 160rpm. And, it is configured to select one of the first threshold value and the second threshold value as the prescribed threshold value according to the command value input from the outside. For example, the first threshold value and the second threshold value are pre-stored in a storage unit (not shown), and one of the first threshold value and the second threshold value is selected according to the command value. In addition, the out-of-step is caused by the rotational speed of the electric motor, so the prescribed threshold value for judging the out-of-step can be appropriately selected according to the command value (duty cycle) input from the outside.

[0035] In addition, if Figure 1 As shown, in this embodiment, IC10 includes a step-out judgment unit 15. The step-out judgment unit 15 is configured to judge that the electric motor 110 is step-out when the rotation speed detected by the rotation speed detection unit 13 is less than a predetermined threshold value. In addition, the step-out judgment unit 15 selects a first threshold value (e.g., 800 rpm) when the command value (duty cycle) is, for example, 30% or more. In addition, the step-out judgment unit 15 judges that the electric motor 110 is step-out when the rotation speed detected by the rotation speed detection unit 13 is less than the first threshold value. In detail, the step-out judgment unit 15 judges that the electric motor 110 is step-out when the rotation speed detected by the rotation speed detection unit 13 is less than the first threshold value for a predetermined time period (e.g., 3 seconds). Therefore, the step-out can be detected in a region where the rotation speed of the electric motor 110 is relatively high. In addition, the step-out judgment unit 15 selects a second threshold value (e.g., 160 rpm) when, for example, the command value (duty cycle) is less than 30%. Furthermore, the step-out determination unit 15 determines that the electric motor 110 is step-out when the rotation speed detected by the rotation speed detection unit 13 is less than the second threshold value. Specifically, the step-out determination unit 15 determines that the electric motor 110 is step-out when the rotation speed detected by the rotation speed detection unit 13 is less than the second threshold value for a predetermined time period (for example, 3 seconds). Therefore, the step-out can be detected in a region where the rotation speed of the electric motor 110 is relatively low.

[0036] In addition, in the present embodiment, when the step-out determination unit 15 determines that the electric motor 110 is stepping out, the voltage command to the electric motor 110 is stopped to stop the electric motor 110. Specifically, when the step-out determination unit 15 determines that the electric motor 110 is stepping out, the output of the PWM signal from the output PWM duty calculation unit 12 to the drive unit 20 is stopped. Therefore, the electric motor 110 is stopped. In addition, the electric motor 110 is stopped for 1 second, for example. At this time, the rotor of the electric motor 110 stops at a predetermined position.

[0037] Furthermore, when the step-out determination unit 15 determines that the electric motor 110 is stepping out, the electric motor 110 in the stopped state is restarted. That is, the electric motor 110 is restarted in a state where the rotor of the electric motor 110 is stopped at a predetermined position. That is, the output of the PWM signal from the output PWM duty calculation unit 12 to the drive unit 20 is restarted. Therefore, the electric motor 110 is started while suppressing step-out.

[0038] Next, refer to Figure 3 The operation of the driving device 100 for the electric motor 110 will be described.

[0039] First, in step S1 , a command value is input to the IC 10 .

[0040] Next, in step S2, a predetermined threshold is determined by the threshold determination unit 14. Specifically, when the command value is equal to or greater than a predetermined value, the first threshold is selected. On the other hand, when the command value is less than a predetermined value, the second threshold is selected.

[0041] Next, in step S3, the voltage of the power supplied to IC10 is input to power voltage correction unit 11, so that power voltage correction unit 11 recognizes the voltage of the power supplied to IC10. Then, power voltage correction unit 11 outputs a signal related to correction to output PWM duty calculation unit 12.

[0042] Next, in step S4, the output PWM duty calculation unit 12 generates a PWM signal based on the input command value and the correction-related signal output from the power supply voltage correction unit 11. Then, the driving unit 20 drives the electric motor 110 based on the generated PWM signal.

[0043] Next, in step S5, the rotation speed detection unit 13 detects (estimates) the rotation speed of the rotor based on the position of the rotor (not shown) detected (estimated) by the position detection unit 30. Then, the detected rotation speed of the rotor is input to the step-out determination unit 15, so that the step-out determination unit 15 recognizes the rotation speed of the rotor.

[0044] Next, in step S6, the step-out determination unit 15 determines whether the rotation speed detected by the rotation speed detection unit 13 is less than a predetermined threshold value in a time period of, for example, 3 seconds. If the step-out determination unit 15 determines that the rotation speed is not less than the predetermined threshold value, the process returns to step S1. In addition, if the step-out determination unit 15 determines that the rotation speed is less than the predetermined threshold value, the process determines that the electric motor 110 is step-out. Then, the process proceeds to step S7.

[0045] Next, in step S7 , the voltage command to the electric motor 110 is stopped, and the electric motor 110 is stopped for, for example, 1 second.

[0046] Next, in step S8, the electric motor 110 is restarted.

[0047] (Effects of this embodiment)

[0048] This embodiment can achieve the following effects.

[0049] In the present embodiment, as described above, the predetermined threshold for the out-of-step judgment unit 15 to judge the out-of-step is changed according to the command value input from the outside. Therefore, since the predetermined threshold is changed based on the command value input from the outside, it is possible to detect the out-of-step in the region of multiple command values ​​(i.e., rotational speed) according to the predetermined threshold corresponding to the command value. In addition, the out-of-step is judged only based on the rotational speed (whether the rotational speed is less than the predetermined threshold), so unlike the case where the current value is used in addition to the rotational speed in the judgment of the out-of-step, there is no need to set an amplifier for detecting the current value. Therefore, it is possible to detect the out-of-step in the region of multiple rotational speeds while suppressing the complexity of the structure. In addition, by comparing the rotational speed detected by the rotational speed detection unit 13 with the predetermined threshold (whether the rotational speed is less than the predetermined threshold), it is determined whether there is a out-of-step, so there is no need to calculate by a relatively complex formula. Therefore, it is possible to suppress the load of the drive device 100 from increasing.

[0050] In addition, in the present embodiment, as described above, when the command value input from the outside is greater than the prescribed value (in a relatively high rotation speed region), it is possible to easily determine whether the electric motor 110 is out of step by comparing the rotation speed detected by the rotation speed detection unit 13 with the first threshold value. In addition, when the command value input from the outside is less than the prescribed value (in a relatively low rotation speed region), it is possible to easily determine whether the electric motor 110 is out of step by comparing the rotation speed detected by the rotation speed detection unit 13 with the second threshold value.

[0051] In addition, in the present embodiment, as described above, the electric motor 110 is stopped when it is determined that the electric motor 110 is losing synchronism. Therefore, it is possible to suppress the continuation of driving the electric motor 110 while the electric motor 110 is losing synchronism.

[0052] In addition, in the present embodiment, as described above, by restarting the electric motor 110 in a state where the rotor is stopped at a predetermined position, the electric motor 110 can be started while suppressing a step loss.

[0053] [Modifications]

[0054] The embodiments disclosed this time should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the description of the above embodiments, and also includes all modifications (variations) within the meaning and scope equivalent to the claims.

[0055] For example, in the above embodiment, an example of using two thresholds (a first threshold and a second threshold) to determine whether the electric motor is out of step is shown, but the present invention is not limited to this. For example, three or more thresholds may be used to determine whether the electric motor is out of step. In addition, the threshold used to determine whether the electric motor is out of step may also change continuously in accordance with the command value.

[0056] In the above embodiment, an example is shown in which the predetermined value (duty ratio) for selecting the first threshold value and the second threshold value is 30%, but the present invention is not limited to this. For example, the predetermined value may be a value other than 30%.

[0057] In addition, in the above embodiment, an example is shown in which the first threshold is 800 rpm and the second threshold is 160 rpm, but the present invention is not limited thereto. For example, the first threshold and the second threshold may be values ​​other than the above values.

[0058] In addition, in the above embodiment, when the step-out determination unit determines that the electric motor is stepping out, the electric motor is stopped for 1 second, but the present invention is not limited thereto. For example, the time period during which the electric motor is stopped may be a value other than 1 second.

[0059] In addition, in the above-mentioned embodiment, an example in which the electric pump device is an electric water pump device is shown, but the present invention is not limited to this. For example, the present invention can also be applied to an electric pump device such as an electric oil pump device.

Claims

1. A driving device for an electric motor, which is a driving device for an electric motor without a position detection sensor, comprising: a driving unit that drives the electric motor according to a command value input from the outside; a rotation speed detection unit that detects the rotation speed of the electric motor driven by the driving unit; as well as a step-out determination unit for determining that the electric motor is losing step when the rotation speed detected by the rotation speed detection unit is less than a predetermined threshold value, The predetermined threshold value is changed according to the command value input from the outside, The predetermined threshold value is selected as a first threshold value based on the command value input from the outside when the command value is equal to or greater than a predetermined value, and a second threshold value smaller than the first threshold value is selected when the command value is smaller than the predetermined value.

2. The driving device of the electric motor according to claim 1, wherein: When the step-out determination unit determines that the electric motor is losing step, a voltage command to the electric motor is stopped to stop the electric motor.

3. The driving device of the electric motor according to claim 2, wherein: When the step-out determination unit determines that the electric motor is stepping out of step, the electric motor in a stopped state is restarted.

4. The electric motor driving device according to any one of claims 1 to 3, wherein: The command value input from the outside is a duty ratio corresponding to the target rotation speed of the electric motor.

5. An electric pump device comprising: an electric pump driven by an electric motor having no position detection sensor; and the driving device of the electric motor, The driving device of the electric motor comprises: a driving unit that drives the electric motor according to a command value input from the outside; a rotation speed detection unit that detects the rotation speed of the electric motor driven by the driving unit; as well as a step-out determination unit for determining that the electric motor is losing step when the rotation speed detected by the rotation speed detection unit is less than a predetermined threshold value, The predetermined threshold value is changed according to the command value input from the outside, The predetermined threshold value is selected as a first threshold value based on the command value input from the outside when the command value is equal to or greater than a predetermined value, and the second threshold value is selected when the command value is smaller than the predetermined value.

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