JP2015081745A - Electric compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric compressor capable of improving mobility by gradually decreasing a differential pressure between a discharge side and a suction side in the compressor.SOLUTION: An electric compressor includes: a compressor 3 that has a rotor and compresses a low pressure refrigerant by the rotation of the rotor so as to be a high pressure refrigerant; a motor 2 to drive the compressor 3; and a motor drive control device 4 to drive the motor 2. The motor drive control device 4 includes a control circuit 11 to control the motor 2 so that a reverse rotational speed is below the reverse rotational speed of the rotor to be generated by a differential pressure between the high pressure refrigerant and the low pressure refrigerant by applying a load to the motor 2 after stopping the motor 2.

Description

  The present invention relates to an electric compressor, and more particularly to a technique for preventing reverse rotation when a motor is stopped.

  A conventional electric compressor of this type is described in Patent Document 1, for example. The compressor motor control device described in Patent Document 1 is a zero vector energizing means for energizing all switching elements on the positive voltage side or the negative voltage side of the inverter device after the operation of the compressor motor is stopped. One of the DC excitation energizing means for energizing the switching element and one switching element on the negative voltage side is operated by the braking means to prevent reverse rotation of the compressor motor.

JP 2000-287485 A

  However, if the reverse rotation of the compressor motor is completely prevented by the braking means, a differential pressure remains on the discharge side and the suction side in the compressor. For this reason, when restarting, there is a possibility that the motor torque is insufficient and the start-up of the compressor may fail.

  An object of the present invention is to provide an electric compressor capable of gradually reducing a differential pressure between a discharge side and a suction side in a compressor to improve startability.

  The present invention includes a compressor that has a rotor and compresses low-pressure refrigerant into high-pressure refrigerant by rotation of the rotor, a motor that drives the compressor, and a motor drive control device that drives the motor. The motor drive control device performs control to apply a load to the motor after stopping the motor so that the reverse rotation speed is less than the reverse rotation speed of the rotor generated by the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant. A control circuit for controlling is provided.

  According to the present invention, the control circuit performs control to apply a load to the motor after stopping the motor, so that the reverse rotation speed is less than the reverse rotation speed of the rotor generated by the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant. Therefore, it is possible to provide an electric compressor capable of gradually reducing the differential pressure between the discharge side and the suction side in the compressor and improving the startability.

It is a lineblock diagram showing the electric compressor of a 1st embodiment of the present invention. It is a flowchart which shows operation | movement of the electric compressor of the 1st Embodiment of this invention. It is a figure which shows the time change of the rotation speed of a compressor by the control of the electric compressor of the 1st Embodiment of this invention, and the differential pressure | voltage of a discharge side and a suction side. It is a figure which shows the switching pattern at the time of direct current excitation energization and the switching pattern at the time of zero vector energization in the electric compressor of the 1st Embodiment of this invention.

  Hereinafter, an electric compressor according to an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration block diagram showing an electric compressor according to a first embodiment of the present invention. The electric compressor shown in FIG. 1 includes an inverter 1, a motor 2, a compressor 3, and a motor drive control device 4.

  The motor 2 is a three-phase AC motor, and drives the compressor 3 by being rotated by the AC power of the inverter 1. The inverter 1 converts a direct current from a direct current power source into an alternating current and supplies the alternating current to the motor 2.

  The inverter 1 includes a first series circuit of a high-side switching element Uh and a low-side switching element Ul, a second series circuit of a high-side switching element Vh and a low-side switching element Vl, and a high-side switching element Wh. And a third series circuit of the low-side switching element Wl are connected in parallel.

  Each switching element Uh, Vh, Wh, Ul, Vl, Wl is composed of an IGBT (insulated gate bipolar transistor). A diode is connected in antiparallel between the collector and emitter of each switching element Uh, Vh, Wh, Ul, Vl, Wl.

  One end of the high-side switching element Uh, one end of the high-side switching element Vh, and one end of the high-side switching element Wh are connected to the positive electrode of the DC power supply and one end of the capacitor C1. One end of the low-side switching element Ul, one end of the low-side switching element Vl, and one end of the low-side switching element Wl are connected to the negative electrode of the DC power supply and the other end of the capacitor C1.

  The other end of the high-side switching element Uh and the other end of the low-side switching element Ul are connected to the U phase of the motor 2. The other end of the high-side switching element Vh and the other end of the low-side switching element Vl are connected to the V phase of the motor 2. The other end of the high-side switching element Wh and the other end of the low-side switching element Wl are connected to the W phase of the motor 2.

  The inverter 1 converts the DC current from the DC power source into a three-phase AC current and supplies it to the motor 2 by turning on / off the six switching elements Uh, Ul, Vh, Vl, Wh, Wl. The motor 2 is composed of a synchronous motor, and is driven to rotate by the three-phase alternating current from the inverter 1 to drive the compressor 3.

  The compressor 3 has a rotor (not shown), and compresses the low-pressure refrigerant into a high-pressure refrigerant by the rotation of the rotor. The motor drive control device 4 is connected to the motor 2 and the inverter 1 to drive the motor 2 and prevent reverse rotation of the motor 2, and includes a microcomputer (MCU) 11 and a memory 12.

  During normal operation, the motor drive control device 4 detects the voltage of each phase of the U phase, V phase, and W phase of the motor 2, detects the position of the rotor in the motor 2 based on the voltage of each phase, Based on the position, six control signals G1, G2, G3, G4, G5, G6 for the six switching elements Uh, Ul, Vh, Vl, Wh, Wl are generated.

  The motor drive control device 4 applies the generated control signals G1, G2, G3, G4, G5, G6 to the gates of the six switching elements Uh, Ul, Vh, Vl, Wh, Wl, The switching elements Uh, Ul, Vh, Vl, Wh, Wl are turned on / off.

  The motor drive control device 4 detects the position of the rotor in the motor 2 during the reverse rotation relaxation control period (reverse rotation relaxation control time) for relaxing the reverse rotation of the rotor in the compressor 3 after the motor 2 stops. Do not do.

  The MCU 11 (corresponding to the control circuit of the present invention) in the motor drive control device 4 loads the motor 2 according to the reverse rotation relaxation control program read from the memory 12 during the reverse rotation relaxation control period after stopping the motor 2. Thus, reverse rotation relaxation control is performed to control the reverse rotation speed to be less than the reverse rotation speed of the rotor generated by the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant. The memory 12 stores a reverse rotation relaxation control program.

In addition, the MCU 11 sets the reverse rotation relaxation control time for applying a load to the motor 2 after stopping the motor 2 to a time when the differential pressure is reduced to a differential pressure at which the compressor 3 can be started. The memory 12 stores a reverse rotation relaxation control time for applying a load to the motor 2.
As a first method for performing reverse rotation relaxation control, the MCU 11 stops the motor 2 and then switches one of the three-phase high-side switching elements Uh, Vh, Wh of the inverter 1 to the three-phase low side. One of the switching elements Ul, Vl, Wl is intermittently turned on, or two of the three-phase high-side switching elements Uh, Vh, Wh and the three-phase low-side switching element Ul, One of Vl and Wl is intermittently turned on, or one of the three-phase high-side switching elements Uh, Vh and Wh and the three-phase low-side switching elements Ul, Vl and Wl Are intermittently turned on. However, the in-phase high-side switching element and the low-side switching element are not turned on at the same time.

  Further, as a second method for performing the reverse rotation relaxation control, the MCU 11 stops all the switching elements Uh, Vh, Wh for the three phases after the motor 2 is stopped, or the low side for the three phases. All the switching elements Ul, Vl, Wl are simultaneously and intermittently turned on.

  Next, the operation of the electric compressor of the first embodiment configured as described above will be described with reference to the flowchart shown in FIG. 2, FIG. 3 and FIG. FIG. 3 is a diagram showing temporal changes in the rotational speed of the compressor and the differential pressure between the discharge side and the suction side under the control of the electric compressor. FIG. 4 is a diagram showing a switching pattern at the time of DC excitation energization and a switching pattern at the time of zero vector energization in the electric compressor.

  First, in the normal operation period from time t0 to t1, the inverter 1 is controlled by the control signals G1, G2, G3, G4, G5, and G6 (rotation commands) from the motor drive control device 4, and the AC power from the inverter 1 The motor 2 is rotated at a normal rotation speed.

  For this reason, the compressor 3 is driven by the rotation of the motor 2, and the low-pressure refrigerant enters the compressor 3. In the compressor 3, the rotor rotates to compress the low-pressure refrigerant and send the high-pressure refrigerant to the discharge side. That is, the electric compressor is operated (step S11).

  Next, when an operation stop command for the electric compressor is sent from the MCU 11 to the inverter 1 at time t1 (step S13), driving of the switching elements Uh, Vh, Wh, Ul, Vl, Wl of the inverter 1 is stopped. . As a result, the electric compressor stops (step S15). Then, the reverse rotation of the rotor of the compressor 3 occurs due to the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant.

  Next, at time t2, the MCU 11 starts reverse rotation relaxation control of the rotor of the compressor 3 (step S17). That is, the MCU 11 performs a control to apply a load to the motor 2 after stopping the motor 2, so that the reverse rotation speed RV 2 is generated by the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant as shown in FIG. Reverse rotation relaxation control is performed to control the reverse rotation speed to be less than RV1.

  Specifically, after the motor 11 is stopped, the MCU 11 stops one of the three-phase high-side switching elements Uh, Vh, Wh of the inverter 1 and the three-phase low-side switching elements Ul, Vl, One of Wl is intermittently turned on, or two of the three-phase high-side switching elements Uh, Vh, Wh and one of the three-phase low-side switching elements Ul, Vl, Wl One of the three-phase high-side switching elements Uh, Vh, Wh and two of the three-phase low-side switching elements Ul, Vl, Wl are intermittently turned on. Turn it on. However, the in-phase high-side switching element and the low-side switching element are not turned on at the same time.

  As another method, the MCU 11 stops all the switching elements Uh, Vh, Wh for three phases or switching elements Ul, Vl, three for three phases after stopping the motor 2. All the switching elements of Wl are turned on simultaneously and intermittently.

  That is, as shown in FIG. 4, by setting the on-duty of the pulse signal to 10 to 20%, for example, a load is intermittently applied to the motor 2, so that the reverse rotation speed RV2 is increased between the high pressure refrigerant and the low pressure refrigerant. The rotor is controlled so as to be less than the reverse rotation speed RV1 generated by the differential pressure. That is, reverse rotation mitigation control for mitigating reverse rotation of the rotor is performed.

  Next, the MCU 11 reads the reverse rotation relaxation control time from the memory 12, and determines whether or not the reverse rotation relaxation control time has elapsed since the reverse rotation relaxation control was started (step S19).

  The reverse rotation relaxation control time is determined by the type of compressor, the differential pressure between the discharge side and the suction side of the compressor 3, the capacity of the compressor 3, the moment of inertia of the compressor 3, the friction during operation of the compressor 3, and the like. The

  Next, at time t3, the MCU 11 stops the reverse rotation relaxation control when the reverse rotation relaxation control time has elapsed since the start of the reverse rotation relaxation control (step S21). At this time, the differential pressure between the discharge side and the suction side of the compressor 3 is significantly reduced and can be returned to the equalized pressure. Therefore, there is no start failure.

  On the other hand, in Patent Document 1 (prior example), even after stop control, each phase voltage induced in the stator winding based on inertial rotation of the motor is detected, and a pulse signal is generated based on the detected each phase voltage. This pulse signal becomes a pulse signal with a narrow interval when the inertial rotational speed is fast, and becomes a pulse signal with a wide interval when the inertial rotational speed is slow.

  Further, when the inertial rotational speed of the motor reaches a predetermined value, the time is caught, and the inverter is brake controlled to stop the inertial rotation of the motor (time t11 in FIG. 3). This braking control is performed by direct current excitation energization or zero vector energization shown in FIG.

  In DC excitation energization or zero vector energization according to Patent Document 1, the on-duty is, for example, 80 to 90% as can be seen from FIG. That is, by increasing the ON time, the rotation of the rotor of the compressor 3 is stopped in a short time, so the differential pressure does not decrease. For this reason, a startup failure occurs during restart.

  As can also be seen from FIG. 3, when reverse rotation mitigation control is not performed, the reverse rotation speed RV1 of the compressor becomes the highest at time t21, and the reverse rotation state becomes smaller at time t23. Further, since the differential pressure is reduced in a short time, abnormal noise generated by reverse rotation becomes a practical problem.

  As described above, according to the electric compressor according to the first embodiment, after the motor is stopped, zero vector energization or DC excitation energization is intermittently performed by PWM control for a predetermined period, whereby the reverse rotation speed is set to the high-pressure refrigerant. Since the control is performed so as to be less than the reverse rotation speed of the rotor generated by the differential pressure with the low-pressure refrigerant, the reverse rotation of the rotor can be mitigated.

  As a result, the differential pressure between the discharge side and the suction side in the compressor can be gradually reduced to improve the startability. In addition, abnormal noise generated by reverse rotation can be reduced to a practically acceptable level.

1 Inverter
2 Motor 3 Compressor
4 Motor drive controller 11 MCU
12 memory

Claims (4)

A compressor having a rotor, and compressing the low-pressure refrigerant into the high-pressure refrigerant by rotation of the rotor;
A motor for driving the compressor;
A motor drive control device for driving the motor,
The motor drive control device performs control for applying a load to the motor after stopping the motor, so that the reverse rotation speed of the rotor is generated by the differential pressure between the high-pressure refrigerant and the low-pressure refrigerant. An electric compressor comprising a control circuit for controlling to be less than   The control circuit sets a control time for applying a load to the motor after stopping the motor to a time for reducing the differential pressure to a differential pressure at which the compressor can be started. The electric compressor according to claim 1. A three-phase bridge inverter having a three-phase series circuit composed of a high-side switching element and a low-side switching element and having the three-phase series circuit connected in parallel,
The control circuit stops one of the three-phase high-side switching elements and the three-phase switching elements so as not to simultaneously turn on the high-phase switching element and the low-side switching element in the same phase after stopping the motor. One of the low-side switching elements for the phase is intermittently turned on, or two of the three-phase high-side switching elements Uh, Vh, Wh and the three-phase low-side switching elements Ul, Vl, One of Wl is intermittently turned on, or one of three-phase high-side switching elements Uh, Vh, Wh and two of three-phase low-side switching elements Ul, Vl, Wl The electric compressor according to claim 1 or 2, wherein one is intermittently turned on. A three-phase bridge inverter having a three-phase series circuit composed of a high-side switching element and a low-side switching element and having the three-phase series circuit connected in parallel,
The control circuit simultaneously and intermittently turns on all the switching elements of the three-phase high-side switching elements or all of the three-phase low-side switching elements after stopping the motor. The electric compressor according to claim 1, wherein the electric compressor is provided.

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