JP4243604B2 - Electric compressor drive device - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is a drive device for an electric compressor, and is particularly suitably used for an electric vehicle or a hybrid electric vehicle that can drive the electric compressor in a state where there is a differential pressure between the suction port and the discharge port. The present invention relates to a drive device for an electric compressor.

  In an air conditioner in a conventional gasoline engine automobile, the engine and the compression portion of the compressor are mechanically connected by a belt, and the compression portion of the compressor is driven by driving the engine. Therefore, when the air conditioner switch is turned on, the driving force of the engine is transmitted to the compressor by the belt, and the compressor can be driven.

  In a compressor used for such an air conditioner or the like, a pressure difference (hereinafter referred to as “differential pressure”) is generated between the suction port and the discharge port of the compressor immediately after the operation state is stopped. In order to restart the compressor with this differential pressure, a larger torque is required than when there is no differential pressure. However, in the case of an air conditioner for a gasoline engine vehicle, since the compressor is driven by the driving force of the engine as described above, it can be started without any problem even when there is a differential pressure.

  However, since an air conditioner of an electric vehicle drives a compressor with a DC voltage from a battery, there is a problem in starting when there is a differential pressure (hereinafter referred to as “differential pressure starting”). More specifically, as described above, at the time of differential pressure startup, a larger torque is required than during normal startup, and a large startup voltage is required to obtain a large torque. However, when the starting voltage is increased, the overcurrent protection circuit is activated and the supply of the starting voltage to the electric compressor is stopped. This overcurrent protection circuit is generally provided to limit the maximum current so that current does not flow excessively in an electric compressor or the like, and limits the maximum current by a current threshold. Therefore, it is conceivable to increase the setting of the current threshold of the overcurrent protection circuit so that a large starting voltage can be applied, but if this is the case, the excessive current causes damage to the semiconductor elements used in the drive device, or to the electric compressor. There is a problem in that the permanent magnet of the built-in motor is demagnetized and the efficiency of the electric compressor is deteriorated or damaged. In addition, in the case of an automobile, since the electric compressor is stopped every time the key switch of the automobile is turned off, the differential pressure is frequently activated, and the above problem becomes more serious.

  On the other hand, in the case of a room air conditioner using an electric compressor, since the air-conditioned space is relatively wide, the temperature change is small even after 2 to 3 minutes until the pressure difference disappears, and the electric compressor is turned on after the pressure difference disappears. Even if it starts, the user does not feel so uncomfortable. In the case of a room air conditioner, once the compressor is operated, it is hardly forcibly stopped from the outside, and therefore the frequency of differential pressure activation is reduced. Therefore, it is not necessary to consider such differential pressure activation in the room air conditioner.

  However, in the case of an air conditioner for an electric vehicle, the power is frequently turned on and off, and the user feels uncomfortable when the air-conditioning space is narrow and waiting for activation until the differential pressure disappears like a room air conditioner. . For this reason, there is a demand for an air conditioner for an electric vehicle that can drive an electric compressor even when there is a differential pressure.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a drive device for an electric compressor that can start the electric compressor even in the presence of a differential pressure.

  An electric compressor driving apparatus according to the present invention includes an electric compressor that compresses and discharges a sucked refrigerant by a sensorless brushless motor, a DC voltage generating means that outputs a DC voltage, and a rotating magnetic field in the sensorless brushless motor. In order to form a DC / AC conversion means for converting a voltage output from the DC voltage power source into a rectangular pulse train-like pseudo AC voltage and outputting it to the sensorless brushless motor, and a current larger than a set current threshold value An overcurrent protection means for preventing the sensorless brushless motor from flowing, and an operation from the start of the sensorless brushless motor to a steady state, which is a sensorless brushless mode, and a steady state operation mode. An electric compressor having a steady mode In the driving device, a differential pressure detecting means for detecting a differential pressure that is a difference between the suction and discharge pressures of the electric compressor and a timer for setting a differential pressure starting time that is a time for changing the setting of the current threshold in the driving device And when the differential pressure is detected, the current threshold of the overcurrent protection circuit is higher during the differential pressure start time than when the differential pressure is not detected, and is permanent in the sensorless brushless motor. The threshold value changing means for setting the magnet demagnetization limit or less, and the voltage value of the pseudo AC voltage applied to the sensorless brushless motor during the startup mode time when the differential pressure is detected is the difference. And a starting duty ratio control means for controlling the duty ratio of the pulse of the pseudo AC voltage so as to be larger than when no pressure is detected, Timer means sets the differential pressure start time than the startup mode hours.

  The drive device for an electric compressor according to the present invention detects a differential pressure, which is a pressure difference between the pressure at the suction port and the pressure at the discharge port, of the electric compressor at the time of start-up by the differential pressure detection means, and there is a differential pressure. Sometimes, for a predetermined differential pressure activation time, the current threshold of the overcurrent protection means is set higher than when there is no differential pressure. At this time, the duty ratio of the rectangular pulse of the AC voltage output from the DC / AC conversion means is increased so that the value of the AC voltage applied to the sensorless brushless motor built in the electric compressor is increased by the starting duty ratio control means. Control. The timer means sets the differential pressure activation time to at least the activation mode time, and during or in addition to the activation mode, the operation mode of the electric compressor is unstable and the activation mode in which the flowing current value is large. The current threshold is set to a high value even immediately after the transition to the steady mode.

  Preferably, in the electric compressor driving device, the differential pressure starting time increases stepwise or linearly according to the differential pressure, and the current threshold of the overcurrent protection means increases as the differential pressure at the time of starting increases. Set to a higher value for a longer time.

  Preferably, in the electric compressor driving apparatus, the current threshold increases stepwise or linearly according to the differential pressure, and the current threshold is set higher as the differential pressure at the time of startup is larger.

  Preferably, in the electric compressor driving device, the starting duty ratio control means controls the magnitude of the duty ratio so that the voltage value of the AC voltage increases stepwise or linearly according to the differential pressure. The higher the starting pressure differential, the higher the starting voltage is applied to the motor in the electric compressor.

  In the electric compressor driving device, since there is a certain correlation between the differential pressure and the motor temperature, a temperature sensor that detects the temperature of the electric compressor can be used as the differential pressure detecting means. .

  In the electric compressor driving device, in order to perform correction based on the outside air temperature, the differential pressure detecting means may be provided with a temperature sensor for detecting the outside air temperature in addition to the temperature sensor for detecting the temperature of the electric compressor.

  According to the electric compressor driving device of the present invention, the differential pressure of the electric compressor is detected at the time of start-up, and when there is a differential pressure, the current threshold of the overcurrent protection means is set high, and the electric compressor is higher than usual. Apply start-up voltage. As a result, a high motor torque is obtained at the time of starting, and the electric compressor can be started even when there is a differential pressure.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the differential pressure starting time is increased in accordance with the magnitude of the differential pressure at the time of starting. Therefore, the larger the differential pressure, the longer the current threshold value. Can be set.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the current threshold value is increased in accordance with the magnitude of the differential pressure at the time of startup. Therefore, the larger the differential pressure, the higher the current threshold value can be set. Therefore, the larger the differential pressure at start-up, the higher the current can flow through the electric compressor and the electric compressor driving device, so that the value of the AC voltage applied to the electric compressor can be increased.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the duty ratio control means is configured so that the value of the AC voltage applied to the electric compressor is increased according to the magnitude of the differential pressure at the time of startup. Therefore, the higher the differential pressure at start-up, the higher the voltage applied to the electric compressor and the higher the motor output.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the differential pressure activation time is set to the activation mode time, so that the current threshold value is not erroneously set high in the steady mode.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the differential pressure activation time is set to the time after a predetermined time has elapsed since the end of the start-up mode. Since the change is made, the electric compressor can be stably operated even in an unstable period immediately after the steady state is reached.

  According to the drive device for the electric compressor of the present invention having a preferred configuration, the differential pressure detecting means is constituted by a temperature sensor that detects the temperature of the electric compressor, and thus can be realized with a simple configuration and at a low cost.

  According to the electric compressor driving apparatus of the present invention having a preferred configuration, the differential pressure detecting means is provided with a temperature sensor for detecting the outside air temperature in addition to the temperature sensor for detecting the temperature of the electric compressor, thereby responding to the outside air temperature. Correction is possible and detection accuracy is improved.

  Embodiments of an electric compressor driving apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an electric compressor driving apparatus suitably used for an air conditioner of an electric vehicle. In this figure, the electric compressor 10 includes a refrigerant compression chamber 11 in which an operation member (for example, a piston) 12 is accommodated for compressing the refrigerant. Further, a refrigerant suction port 16 and a refrigerant discharge port 17 are connected to the compression chamber 11, and these constitute a part of the refrigerant circulation circuit. A sensorless brushless motor (hereinafter referred to as “motor”) 13 that is a driving source of the compressor 10 includes a stator 14 in which a coil is wound around a yoke, and a rotor 15 having a permanent magnet. The operation member 12 is driven and connected to the operation member 12. The operation member 12 is driven by driving the motor 13, and the refrigerant sucked from the suction port 16 is compressed in the compression chamber 11 and discharged from the discharge port 17.

  The motor 13 is connected to the battery 3 which is a DC power source via the switch 1, the DC / AC conversion circuit (hereinafter referred to as “inverter”) 5 and the overcurrent protection circuit 7, and the inverter 5 is turned on by turning on the switch 1. An operating voltage is applied via the switch. The inverter 5 includes a plurality of switching transistors 18. By turning on / off these transistors, the inverter 5 converts the DC voltage output from the battery 3 into a three-phase pseudo AC voltage in the form of a rectangular pulse train and supplies it to the motor 13. The compressor 10 is driven. As apparent from FIGS. 2A and 2B showing the voltage waveform, the AC voltage value can be controlled by adjusting the duty ratio (t / T) of each pulse. When it is increased, the AC voltage increases, and a high starting voltage is applied to the motor 13. The voltage waveform in FIG. 2 shows the U, V, and W phase voltages as viewed from the neutral point of the motor 13.

On the other hand, the current flowing through the motor 13 is limited by the overcurrent protection circuit 7. In this overcurrent protection circuit 7, as shown in FIG. 3, two resistors 33 and 34 are connected in series between a power supply line Vdd and a ground line GND for providing a reference potential, and in parallel with one resistor 33, PNP A transistor 31 and a resistor 35 are connected, and two different types of reference input terminal (+) of the comparator 39 are provided depending on a signal output from the NAND gate 29 of the activation condition setting unit 9 to be described later to the transistor 31. A reference voltage is selectively input. The overcurrent protection circuit 7 also includes a current sensor 37 that detects a current flowing through the inverter 5 so that a comparison voltage corresponding to the detected current value is input to the comparison input terminal (−) of the comparator 39. The comparator 39 compares the input reference voltage with the comparison voltage, and outputs the comparison result to the inverter 5. Specifically, in the present driving device, two current thresholds I _TH-L and I _TH-H , which are the limit values of the current flowing through the inverter 5, are obtained by inputting two different reference voltages to the reference input terminal of the comparator 39. , And one of the current threshold _values I _TH-L or I _TH-H is set according to the signal output from the start condition setting unit 9 to the transistor 31. Then, the current value detected by the current sensor 37 is compared with the current threshold value I _TH-L or I _TH-H by the comparator 39. If the detected current value is smaller than the current threshold value, each transistor 18 of the inverter 5 is On the contrary, when the detected current value is larger than the current threshold value, the transistor 18 of the inverter 5 is set so as to maintain the off state (that is, cannot be turned on).

  Returning to FIG. 1, the start condition setting unit 9 sets conditions for starting the compressor 10. Before describing the start condition setting unit 9, the operation mode of the compressor 10 will be briefly described. In general, in the case of an electric compressor equipped with a sensorless brushless motor, the start-up voltage is controlled without considering the position of the rotor with respect to the stator from the start-up to the steady state. This operation mode is referred to as “startup mode”. Thereafter, when the rotation of the motor is stabilized and becomes a steady state, the position of the motor with respect to the stator is detected from the voltage induced in the coil, and the drive voltage of the motor is feedback-controlled according to the position. Hereinafter, this operation mode is referred to as “steady mode”. Switching from the startup mode to the steady mode is performed based on time, and the mode is automatically switched from the startup mode to the steady mode when a predetermined time has elapsed from the start of startup. Hereinafter, this predetermined time is referred to as “start-up mode time”. The starting condition setting unit 9 sets the current threshold value of the overcurrent protection circuit 7 in the starting mode and the duty ratio of the pulse applied to the motor 13.

  In order to perform these controls, the activation condition setting unit 9 includes a pressure difference (differential pressure) detection means 27 at the suction port 16 and the discharge port 17 of the compressor 10, a threshold value changing unit 21, and an activation duty ratio control unit 23. And a starting voltage control unit 20 including a timer 25 and a NAND gate 29.

  As the differential pressure detecting means, a temperature sensor 27 is used in the present embodiment. The reason is that even when the compressor 10 is stopped, the temperature does not drop rapidly but tends to gradually decrease with time, and there is a substantially constant relationship between the temperature and the differential pressure. This is because the differential pressure can be roughly estimated by measuring. Specifically, in this embodiment, it is determined that there is no differential pressure if the temperature of the compressor 10 is less than 40 ° C., and that there is a differential pressure if the temperature is 40 ° C. or higher.

  As shown in FIG. 4, the starting duty ratio control unit 23 has a normal starting duty ratio control mode M <b> 1 when there is no differential pressure (the temperature of the compressor 10 is less than 40 ° C.), and when there is a differential pressure (the compressor 10 And a differential pressure starting duty ratio control mode M2 having a temperature of 40 ° C. or higher, and when it is determined that there is no differential pressure based on the output from the temperature sensor 27, the former normal starting duty ratio control mode M1 When the duty ratio is controlled with time, and it is determined that there is a differential pressure, the duty ratio is controlled with time according to the latter differential pressure starting duty ratio control mode M2. Further, the duty ratio at each point in the differential pressure starting duty ratio control mode M2 is larger than that in the normal starting duty ratio control mode M1, and a larger voltage is applied to the motor 13 at the time of starting the differential pressure than at the time of normal starting. It is supposed to be.

The timer 25 sets a differential pressure starting time which is a time for setting the current threshold to a high value I _TH-H when there is a differential pressure at the time of starting. In the present embodiment, as shown in FIG. 5B, the differential pressure activation time is set to a time t2 when a predetermined time has elapsed after the activation mode ends.

  The threshold value changing unit 21 creates a threshold value setting signal that is different when it is determined that there is no differential pressure from the output from the temperature sensor 27 and when it is determined that there is a differential pressure, and outputs this.

The NAND gate 29 performs an NAND operation on the output from the timer 25 and the output from the threshold changing unit 21 and outputs the operation result to the overcurrent protection circuit 7. Specifically, as shown in FIG. 6, when it is determined that there is no differential pressure in the compressor 10 (when the temperature of the compressor 10 is less than 40 ° C.), the current threshold I _TH-L of the overcurrent protection circuit 7 is 30. Set to Amps. On the other hand, when it is determined that the compressor 10 has a differential pressure (when the temperature of the compressor 10 is 40 ° C. or higher), the current threshold I _TH-H of the overcurrent protection circuit 7 is set to 40 amperes. These current thresholds I _TH-L and I _TH-H are set to be equal to or less than the demagnetization limit of the magnet. Further, the demagnetization limit characteristic shown in FIG. 6 shows an example in a ferrite magnet.

The start-up control of the electric compressor driving device configured as described above will be described with reference to the flowchart shown in FIG. This control is started by turning on the start switch 1 of the electric compressor driving device. When the switch 1 is turned on, the start-up control is started, the output of the temperature sensor 27 is detected (S1), and then the presence or absence of a differential pressure is determined from the output (S2). When there is no differential pressure, the threshold value changing unit 21 outputs a first threshold value setting signal to set the current threshold value of the overcurrent protection circuit 7 to I _TH-L . As a result, the current threshold in the overcurrent protection circuit 7 is set to I _TH-L (30 amperes) (S3). Next, the starting duty ratio control unit 23 sets the normal starting duty ratio control mode M1 (see FIG. 4) (S4), and the voltage applied to the motor 13 according to the mode M1 is changed over time during the starting mode time. To change. When the startup mode time ends, the program enters the steady mode, and the duty ratio control in the steady mode is performed (S13).

If there is a differential pressure during startup, a differential pressure startup time t2 is set (S6). Next, the threshold value changing unit 21 outputs a second threshold value setting signal to set the current threshold value of the overcurrent protection circuit 7 to I _TH-H . Thereby, during the differential pressure starting time t2, the current threshold value in the overcurrent protection circuit 7 is set to I _TH-H (40 amperes) (S7). This current threshold value I _TH-H is larger than the current threshold value I _TH-L (30 amperes) set at the time of normal startup (see FIG. 8), and a larger current than that at the time of normal startup is allowed to flow to the motor 13. . However, since the current threshold I _TH-H is set lower than the demagnetization limit of the magnet, the magnet is demagnetized and the reversibility is not lost. Subsequently, the starting duty ratio control unit 23 sets the differential pressure starting duty ratio control mode M2 (see FIG. 4) (S8), and controls the voltage applied to the motor 13 according to this control mode during the starting mode time. To do. In the differential pressure starting duty ratio control mode M2, as shown in FIG. 4, the duty ratio at each time is larger than that in the normal starting duty ratio control mode. Therefore, a larger voltage is applied to the motor at the time of differential pressure startup than during normal startup. Therefore, even if there is a differential pressure, the motor 13 rotates to compress the refrigerant and the air conditioner operates. When the start mode time ends (S9), the start duty ratio control unit 23 shifts from the differential pressure start duty ratio control mode M2 to the steady mode duty ratio control (S10). Thereafter, when the differential pressure activation time t2 ends (S11), the threshold value changing unit 21 turns off the second threshold value setting signal and sets the current threshold value of the overcurrent protection circuit 7 as the current mode threshold value (S12). Duty ratio control in the steady mode is performed (S13).

  As described above, when there is a differential pressure at the time of starting, the current threshold of the overcurrent protection circuit 7 is set high for a predetermined time, and during that time, a high starting voltage is applied to drive the compressor 10 and operate the air conditioner. it can. FIG. 9 shows the relationship between the battery output voltage and the compressor startable differential pressure. According to the differential pressure startup of the present invention, the compressor can be started even when there is a higher differential pressure with a lower input voltage than in the conventional startup control. Can understand. Further, since the current threshold is set to be equal to or less than the demagnetization limit of the permanent magnet in the motor, the reversibility of the permanent magnet is not lost.

  In the above description, as shown in FIG. 5 (b), the differential pressure activation time is set to the time when a predetermined time has elapsed after the completion of the activation mode. The reason is that the compressor immediately after shifting from the activation mode to the steady mode. This is because the operation 10 is unstable, and an overcurrent may flow through the motor 13. This differential pressure start-up time increases stepwise or linearly according to the differential pressure, and the larger the differential pressure at start-up, the higher the current threshold of the overcurrent protection means is set to a higher value for a longer time. May be.

In the above description, the current threshold of the overcurrent protection circuit is set to a different value depending on whether or not there is a differential pressure. However, if there is a differential pressure, the current threshold is set according to the degree of the differential pressure. May be changed stepwise or linearly.
Similarly, the duty ratio control mode at startup may be defined as a function of the differential pressure, and the duty ratio control mode may be changed stepwise or linearly according to the differential pressure.

  Furthermore, in the above description, the differential pressure is estimated only from the temperature of the compressor. However, when the outside air temperature changes, more accurate detection can be performed by correcting the detection value according to the outside air temperature. Therefore, as shown in FIG. 1, in the differential pressure detecting means, a temperature sensor 28 for detecting the outside air temperature may be provided outside the compressor in addition to the temperature sensor 27 for detecting the temperature of the compressor. Furthermore, a pressure detection device may be provided at the suction port and the discharge port of the compressor to detect the actual differential pressure, and the current threshold value, the duty ratio, and the differential pressure activation time may be changed based on the detection result.

The block diagram of the drive device of the electric compressor of this invention. The figure which shows the waveform of the pseudo alternating voltage which is an output of an inverter. The circuit diagram of an overcurrent protection circuit. The figure which shows the time change from the time of starting of the duty ratio of the rectangular pulse which comprises the pseudo alternating voltage applied to an electric compressor. The figure which shows the output of a timer. The figure which shows the relationship between the temperature of an electric compressor, the current threshold value of an overcurrent protection circuit, and the demagnetization limit of the permanent magnet of the rotor of an electric compressor. The flowchart which shows operation | movement of the drive device of an electric compressor. The figure which shows the relationship between the peak value of starting current, and the elapsed time after starting. The figure which shows the relationship between an input voltage and a startable differential pressure | voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Switch, 3 ... Battery, 5 ... Inverter (DC alternating current conversion circuit), 7 ... Overcurrent protection circuit, 9 ... Starting condition setting part, 10 ... Electric compressor, 11 ... Refrigerant compression chamber, 12 ... Operating member, 13 ... DC brushless motor, 14 ... stator, 15 ... rotor, 16 ... refrigerant inlet, 17 ... refrigerant outlet, 18 ... switching transistor, 20 ... start-up voltage control unit, 21 ... threshold changing unit, 23 ... start-up duty ratio Control unit 25 ... Timer 27 ... Temperature sensor (for detecting motor temperature) 28 ... Temperature sensor (for detecting outside temperature) 29 ... NAND gate 31 ... PNP transistor 33-35 ... Resistance 37 ... Current sensor 39 ... Comparator.

Claims (6)

An electric compressor that compresses and discharges the sucked refrigerant by a sensorless brushless motor, a DC voltage generating means that outputs a DC voltage, and an output from the DC voltage power source to form a rotating magnetic field in the sensorless brushless motor. DC / AC converting means for converting the generated voltage into a pseudo-AC voltage in the form of a rectangular pulse train and outputting the pseudo-AC voltage to the sensorless brushless motor; A start-up mode that is an operation mode that does not consider the position of the rotor of the sensorless brushless motor from when the sensorless brushless motor is started to a steady state, and a steady-state operation mode. Driving an electric compressor having a steady mode In the location,
Differential pressure detecting means for detecting a differential pressure that is a difference between the suction and discharge pressures of the electric compressor at the time of startup;
Timer means for setting a differential pressure starting time which is a time for changing the setting of the current threshold;
When the differential pressure is detected, the current threshold of the overcurrent protection circuit is higher during the differential pressure starting time than when the differential pressure is not detected, and the permanent magnet in the sensorless brushless motor is reduced. Threshold changing means for setting below the magnetic limit;
When the differential pressure is detected, the pseudo alternating current voltage applied to the sensorless brushless motor during the start-up mode time is larger than when the differential pressure is not detected. A starting duty ratio control means for controlling the duty ratio of the pulse of the voltage,
The said timer means sets the said differential pressure starting time more than the said starting mode time, The drive device of the electric compressor characterized by the above-mentioned. 2. The electric compressor driving device according to claim 1, wherein the differential pressure starting time increases stepwise or linearly according to the differential pressure. 3. The electric compressor driving device according to claim 1, wherein the current threshold value is changed stepwise or linearly according to the differential pressure. 4. The drive device for an electric compressor according to claim 1, wherein the starting duty ratio control means changes the AC voltage value stepwise or linearly according to the differential pressure. 5. An electric compressor driving device that controls the magnitude of a duty ratio. 5. The electric compressor driving device according to claim 1, wherein the differential pressure detecting unit includes a temperature sensor that detects a temperature of the electric compressor. 6. 5. The electric compressor driving device according to claim 1, wherein the differential pressure detection unit includes a temperature sensor that detects a temperature of the electric compressor and a temperature sensor that detects an outside air temperature. 6. An electric compressor drive device.

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