BACKGROUND

The present disclosure relates to an onboard fluid machine and a method for controlling an onboard fluid machine.

Motor control includes position sensorless control for controlling a motor while estimating the rotation angle (rotation position) of the rotor. Japanese Laid-Open Patent Publication No. 2016-185040 describes an example of a controller that performs sensorless control. The controller applies voltage having a predetermined pulse width to phase coils in a positive direction and a negative direction to obtain the position of the rotor based on the current supplied when the voltage is applied.

SUMMARY

It is an object of the present disclosure to provide an onboard fluid machine and a method for controlling an onboard fluid machine capable of reducing the size of a motor.

Examples of the present disclosure will now be described.

Example 1

An onboard fluid machine including an inverter device and a motor is provided. The inverter device includes an inverter circuit having a switching element, the inverter circuit being configured to supply the motor with alternating-current power, a current controller configured to calculate a d-axis voltage command value and a q-axis voltage command value, and a rotation angle estimation unit configured to calculate a rotation angle of a rotor of the motor from a d-axis current and a q-axis current that flow into the motor and from the d-axis voltage command value and the q-axis voltage command value. The inverter device further includes a correction unit. The correction unit is configured to apply a pulse voltage to the motor when the motor is in a stopped state and correct a parameter for control of the motor in accordance with a comparison result of the d-axis current and the q-axis current, which flow into the motor when the pulse voltage is applied.

In the above-described configuration, when the motor is in a stopped state, pulse voltages are applied to the motor. In the above-described configuration, the saliency ratio (q-axis inductance/d-axis inductance) is estimated in accordance with the comparison result of the d-axis current and the q-axis current, which flow into the motor when the pulse voltages are performed. This indirectly detects the inductance of the motor. In the above-described configuration, the parameter for the control of the motor is corrected based on the estimated saliency ratio. Thus, the steady-state errors between the control phase and the maximum torque phase in the rotation of the rotor are reduced. This limits decreases in the output torque, sets the torque margin to be small, and reduces the size of the motor. The above-described saliency ratio estimation is to indirectly detect the inductance of the motor. The above-described estimation of the saliency ratio involves the use of larger changes in the q-axis inductance than in the d-axis inductance in accordance with the changes in the amount of the magnetic fluxes of the magnets. Additionally, in the present embodiment, the comparison result of the d-axis current and the q-axis current is used to correct the parameter for the control of the motor. This allows errors in the gain of the current sensors to be cancelled. As a result, correction values can be calculated more accurately.

In the production of the magnets of interior permanent magnet motors, variation occurs in the amount of the magnetic fluxes of the magnets. Because of the influence of magnetic saturation, the inductance of the motor decreases in proportion to the amount of the magnetic fluxes of the magnets. Thus, variation in the amount of the magnetic fluxes of the magnets results in the following problem. That is, when position sensorless control is used to estimate the rotation angle of the rotor from a motor current and an inverter output voltage (motor applied voltage), the estimated position of the rotor is inaccurate due to the inductance. More specifically, as shown inFIG. 11Aof the present application, when the control phase in the rotation of the rotor is deviated with respect to the maximum torque phase of the motor, the output torque of the motor decreases. A torque margin is needed to compensate for the decrease in the torque. This enlarges the motor. The above-described configuration solves such a problem.

Example 2

In the onboard fluid machine according to example 1, the rotation angle estimation unit is configured to estimate an angle of the rotor from a U-phase current, a V-phase current, and a W-phase current that flow into the motor when the pulse voltage is applied. In this configuration, the U-phase current, the V-phase current, and the W-phase current, which are needed to obtain the d-axis current and the q-axis current, are used to estimate the rotation angle of the rotor. Thus, when a pulse voltage is applied once, the saliency ratio and the rotation angle can both be estimated. The motor can be quickly reactivated by performing an advanced estimation of the rotation angle of the rotor when in a stopped state.

Example 3

In the onboard fluid machine according to example 1 or 2, the correction unit is configured to correct a power voltage detection value of the inverter circuit serving as the parameter for the control.

Example 4

In the onboard fluid machine according to example 1 or 2, the correction unit is configured to correct the d-axis voltage command value and the q-axis voltage command value, which serve as the parameter for the control.

Example 5

In the onboard fluid machine according to example 1 or 2, the correction unit is configured to correct a d-axis inductance and a q-axis inductance that serve as the parameter for the control.

Example 6

A control method for controlling an onboard fluid machine is provided. The onboard fluid machine includes an inverter device and a motor. The control method includes supplying, by an inverter circuit having a switching element, the motor with alternating-current power, calculating, by a current controller of the inverter device, a d-axis voltage command value and a q-axis voltage command value, calculating, by a rotation angle estimation unit, a rotation angle of a rotor of the motor from a d-axis current and a q-axis current that flow into the motor and from the d-axis voltage command value and the q-axis voltage command value, applying, by a correction unit of the inverter device, a pulse voltage to the motor when the motor is in a stopped state, comparing, by the correction unit, the d-axis current and the q-axis current, which flow into the motor when the pulse voltage is applied, and correcting, by the correction unit, a parameter for control of the motor in accordance with a result of the comparison.

Example 7

A non-transitory computer-readable storage medium that stores a program causing a processor to execute a control process for controlling an onboard fluid machine is provided. The control process includes supplying, by an inverter circuit having a switching element, the motor with alternating-current power, calculating, by a current controller of the inverter device, a d-axis voltage command value and a q-axis voltage command value, calculating, by a rotation angle estimation unit, a rotation angle of a rotor of the motor from a d-axis current and a q-axis current that flow into the motor and from the d-axis voltage command value and the q-axis voltage command value, applying, by a correction unit of the inverter device, a pulse voltage to the motor when the motor is in a stopped state, comparing, by the correction unit, the d-axis current and the q-axis current, which flow into the motor when the pulse voltage is applied, and correcting, by the correction unit, a parameter for control of the motor in accordance with a result of the comparison.

According to the present disclosure, it is capable of reducing the size of a motor.

Other aspects and advantages of the present disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure.

