JP4928763B2 - Control device for electric compressor - Google Patents

Description

  The present invention relates to a control device for an electric compressor, and more specifically, a board on which a switching element constituting a part of the control device is mounted is housed in a casing of an electric compressor used in an in-vehicle air conditioner. It is related with the control apparatus of the said electric compressor in the case where it is carried out.

  An on-vehicle air conditioner in an electric vehicle, a fuel cell vehicle, or the like not equipped with an engine has a compressor with a built-in electric motor as a power source for compressing and circulating a refrigerant. Since the electric motor needs to be rotated at a desired number of revolutions according to a command from the main controller of the air conditioner, a separate controller is necessary. The control device includes an electric circuit or an electronic circuit. Specifically, it is composed of electronic elements such as a central processing unit and a memory, and switching elements (power transistor elements) such as IGBTs and FETs for constituting a so-called inverter circuit (switching circuit). Some of these control devices are integrated with an electric compressor in order to save space.

  The switching element is used to supply a large amount of electric power to the electric motor and control the rotational speed of the electric motor. However, since the final purpose of the control is the rotational speed of the electric motor, it is intended to control this to a desired value. Then, power consumption may become excessive during the control process, and sometimes an overcurrent that may damage the control device may flow. The electric vehicle and the fuel cell vehicle use a battery as a power source, and the wheels, lamps, and audio are also operated with the same power from the same battery. Therefore, overconsumption of power in the air conditioner is another factor attached to the vehicle. There is a possibility of affecting the device, for example, pushing the device to stop.

  In such a case, the DC voltage and / or DC current of the inverter circuit is detected, and if the current exceeds a permissible value, the rotational speed of the electric compressor is reduced or the battery voltage falls below the permissible value. The idea is to reduce the rotational speed of the electric compressor. Moreover, the device of calculating | requiring power consumption from the said DC voltage or direct current by calculation, and controlling the rotation speed of an electric compressor so that it may become below an allowable value is also disclosed (for example, patent document 1).

JP-A-6-72135

  However, since there is a demand for miniaturization, in an electric compressor integrated with a control device, the temperature of a switching element such as an IGBT must also be taken into consideration. Normally, switching devices such as IGBTs are designed for grounding heat dissipation design. However, since they are housed in the engine room (motor room) and in the housing of the electric compressor, the heat dissipation design is not easy. Absent. And not only the heat balance of the switching element that flows a large current but also the heat balance in consideration of the relationship with the refrigerant circulation function of the electric compressor, the power supply and the rotation speed of the compressor must be controlled. .

  Therefore, the present invention has been made in view of the above, and in the control device for the electric compressor that is integrally mounted on the casing of the electric compressor, the rotational speed of the compressor and the electric compressor It is an object of the present invention to provide a control device for an electric compressor that effectively uses electric power while protecting the switching elements constituting the control device from excessive heat generation in consideration of the relationship with the refrigerant circulation function.

In order to solve the above-described problems and achieve the object, a control device for an electric compressor according to the present invention is an electric motor that is determined from a motor rotation speed command from a main control device of an air conditioner and a motor stator current. A control device having a rotation speed control unit that controls the rotation speed of an electric compressor based on a difference from the rotation speed, and a board physically configuring the control device is housed in a casing of the electric compressor In the control device for the electric compressor, the rotation speed control unit needs to protect the switching elements constituting the control device regardless of the motor rotation speed command from the main control device of the air conditioner. When a certain condition A relating to the inverter output current or the switching element temperature is satisfied, the cooling capacity by the refrigerant circulation exceeds the heat generation of the switching element and the current Have a rotational speed limiting control unit for maintaining the rotational speed of the electric compressor in a rotational speed between the upper limit rotation speed and lower limit rotation speed for a predetermined of Hiroshidai occurs, and the predetermined condition A, 1 sec The maximum value of the absolute value of the inverter output current is a condition that the value of a certain ratio with respect to the rated current of the switching element, which is known in advance, is exceeded .

  The control device for the electric compressor is generally controlled on the basis of the difference between the motor speed command from the main controller of the air conditioner and the motor speed calculated from the motor stator current fed back. It is. For example, the current command is generated by multiplying the difference by a gain or integrating the difference. In general, the current command is converted into a rectangular voltage waveform by PWM, and output to an inverter for control.

  By the way, there is a type of control device for an electric compressor in which a board that physically constitutes the control device is housed in a casing of the electric compressor. This type of control device is cooled by a refrigerant that is a compression target of the electric compressor. Since the switching elements such as IGBTs constituting the inverter handle a large current, they easily generate heat, and a refrigerant is also used for this cooling through a casing.

  The heat balance of the switching element in the control device configured as described above is affected by both the heat generation of the element itself and the cooling by the refrigerant. According to the experiments and simulations of the inventor, in a specific rotation speed range of the electric compressor, the cooling capacity by the refrigerant circulation exceeds the heat generation of the element compared to other rotation speed ranges, and the value of the current flowing to the inverter is increased. I understood the feature that it can be enlarged. The present invention pays attention to this, and the rotation speed control unit is subject to certain conditions that require protection of the switching elements constituting the control device regardless of the motor rotation speed command from the main controller of the air conditioner. Thus, the rotation speed of the electric compressor is maintained within a rotation speed between a desired upper limit rotation speed and a lower limit rotation speed. The certain condition relates to the inverter current value.

  The constant conditions that require protection of the switching elements that constitute the control device may include the temperature of the switching elements themselves, the difference between the current command and the actual current, etc. In this invention, focus on the rated current of the switching elements. If a current exceeding 90% of this is output from the inverter, it is indirectly determined that the upper limit of the current that can be passed through the switching element or the upper limit set value of the overcurrent limiter is approached. it can.

Moreover, the electric compressor according to the present invention is an inverter that represents the stable state of the switching element when the rotation speed limit control unit is no longer satisfying the predetermined condition A in the control device for the electric compressor. When a certain condition B relating to the output current or the switching element temperature is satisfied, the required rotational speed from the main control device is compared with the actual operational rotational speed, and the actual operational rotational speed is greater than the required rotational speed. When the rotational speed is decreased by a constant rotational speed, and the actual operating rotational speed is smaller than the required rotational speed, the actual operational rotational speed is increased by a constant rotational speed , and the constant condition B is the maximum value of the inverter output current absolute value, is the condition of being divided by a value smaller than a certain percentage of the rated current of the switching elements employed in the certain condition a It is obtained by the.

  Since the rotational speed limit control is to control the rotational speed separately from the rotational speed command from the main control circuit of the HVAC, when the control is canceled, there is a possibility that a difference occurs between the actual operational rotational speed and the required rotational speed. There is sex. Therefore, the present invention compares the required rotational speed from the main controller with the actual operating rotational speed in order to prevent a sudden rotational speed change from occurring in the compressor when the rotational speed restriction control is canceled. When the actual operation speed is larger than the required rotation speed, the actual operation speed is decreased by a certain rotation speed, and when the actual operation rotation is smaller than the required rotation speed, the actual operation rotation speed is reduced to a certain rotation speed. It is intended to increase by minutes.

Moreover, the electric compressor according to the present invention is an inverter that represents the stable state of the switching element when the rotation speed limit control unit is no longer satisfying the predetermined condition A in the control device for the electric compressor. When the constant condition B relating to the output current or the switching element temperature is not satisfied, it is continuously determined whether the constant condition A is satisfied while maintaining the rotation speed when the constant condition A is not satisfied. If the condition A is satisfied, the rotation speed of the electric compressor is maintained within a rotation speed between a predetermined upper limit rotation speed and a lower limit rotation speed , and the constant condition B is the inverter output current during one second. that the maximum value of the absolute value, and to be a condition that is divided by a value smaller than a certain percentage of the rated current of the switching elements employed in the certain condition a A.

  In this invention, the rotation speed of the electric compressor is often not immediately stabilized due to the influence of the control circuit placed in a high temperature environment or the influence of the refrigerant load, so the rotation speed limit control is performed while maintaining the rotation speed for the time being. Judge whether it is appropriate to continue or it is appropriate to control with the release condition. This ensures proper operation of the switching element in an intermediate state between the state where the switching element should be protected from excessive high temperature and the stable state.

The condition A is used to determine whether or not the switching element should be protected from excessive high temperature, and the condition B is used to determine whether or not the switching element is stabilized. The condition A and the condition B can be selected separately from the condition A and the condition B. For the above reason, the maximum value of the inverter output current absolute value in one second is determined by the condition B. It is realistic and appropriate to make the condition that a value smaller than a certain ratio to the current is divided.

  The control device for the electric compressor according to the present invention is the control device for the electric compressor that is integrally mounted on the casing of the electric compressor, and includes the rotation speed of the compressor and the refrigerant circulation function of the electric compressor. In consideration of the relationship, the switching elements constituting the control device can be protected from excessive heat generation.

  Embodiments of an electric compressor control device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  FIG. 1 is an external view showing an electric compressor in which a control device is integrated with a casing. A housing 2 of the electric compressor 1 has a box-shaped portion 4 that can accommodate a substrate 3 constituting a control device. The substrate 3 is accommodated in this portion. An electric signal from a power source, a temperature detector, etc., an electric signal from the main controller of the air conditioner, and the like are input to the board 3 from the outside of the electric compressor 1. The output of the substrate 3 is a current (voltage) to the electric motor and becomes an input of the electric motor provided in the housing 2.

  FIG. 2 is a graph showing the relationship between the rotational speed of the electric compressor and the current margin against overcurrent, where the horizontal axis represents the rotational speed (rps) and the vertical axis represents the current margin (Arms). The current margin is a current margin with respect to a current limiter value set in advance in the inverter circuit. In addition, here, the results obtained by examining three values of the high-pressure side pressure / low-pressure side pressure of the compressor are shown. That is, the case where the pressure loads on the compressor are different is shown.

  As shown in the figure, in the control of the electric motor compressor, simply reducing the rotational speed cannot increase the margin of current. Further, even if the rotational speed is increased, the current margin does not increase. The temperature of the IGBT, which is a switching element that constitutes the inverter, basically has a tendency to increase as the rotation speed of the electric motor increases. However, when the rotation speed of the electric compressor increases, a large amount of refrigerant to be compressed circulates. As a result, the cooling effect on the switching element by the refrigerant increases.

  Combined with the cooling effect of the refrigerant, it has been found that the electric motor of the electric compressor has a larger current margin in a certain rotation speed region than in other regions. This showed the same tendency with the three curves 5, 6, and 7 when the pressure load of the compressor was changed. If this is utilized, even if the motor was previously stopped due to the heat generation temperature of the switching element, it can be stopped by controlling the rotation speed so that it falls within a specific range obtained through experiments and simulations. The state can be avoided. In other words, in the present invention, even when the current margin is reduced in the low rotation range during normal operation, it is possible to cool the IGBT by increasing the number of revolutions, thereby cooling the IGBT, and the current margin is also reduced. Can be big. For this reason, it is possible to protect the switching elements constituting the switch circuit by controlling the electric compressor at a rotation speed that allows the current margin.

  FIG. 3 is a block diagram showing the positioning of the rotation speed limit control unit with respect to the overall control of the electric compressor. In general, the rotational speed control of the electric compressor is based on a rotational speed command from a main controller that manages the temperature management of the air conditioner (HVAC 8). The rotation speed command is input to the rotation speed control unit 9 and converted into an output to the inverter 10. In order to simplify the explanation, the rotation speed control unit 9 is a large concept including a so-called servo circuit such as a current command calculation unit and a PWM circuit.

  The rotation speed controller 9 feeds back the magnitude and phase of the stator current of the electric motor 11. The rotational speed can be grasped from the information, and a so-called servo circuit is configured by the difference from the rotational speed command from the HVAC 8. Further, a rotation speed limit control section 12 is provided in a part of the rotation speed control section 9, and the control process set in the rotation speed limit control section 12 is executed when the inverter output current has a fixed relationship. Is done.

  FIG. 4 is a flowchart showing a control process executed by the rotation speed limit control unit. Here, the control is mainly performed by limiting the rotational speed of the electric compressor, and this is referred to as rotational speed limit control. First, the condition A for starting such control is the switching in which the maximum value of the absolute value of the inverter output current during 1 second is known in advance during the conventional rotation speed control of the electric compressor. It is larger than the rated current of the element × 0.9 (this is referred to as a limit start current) (step S101).

  This condition A is obtained from experiments and simulations, and is not necessarily limited to the value of the rated current of the switching element × 0.9, but the temperature of the switching element is high, for example, 90 degrees Celsius or more, and the refrigerant circulation In the rotational speed region where the cooling capacity is low due to the above, it is necessary to determine in some form a condition such that the current control circuit or (program) makes a state immediately before the motor control stops. For example, the inverter output current value may be used as described above, or the temperature of the switching element may be used directly. When this condition is satisfied, it is determined whether or not the actual operation rotational speed of the electric compressor is smaller than a predetermined rotational speed N1 (step S102).

  When the actual operation speed is smaller than the predetermined speed N1 which is the lower limit of the speed to be controlled, the current margin becomes small at that speed, and the motor is not stopped by the inverter limiter. Since the possibility of not being increased increases, the rotational speed is increased by a predetermined rotational speed N3, for example, 10 (rps) (step S103). Note that N1 is a value set in advance by experiments and simulations, and if it is determined from FIG. 1, a value near 80 (rps) where the current margin becomes large is appropriate.

  After step S103, it takes a time for the temperature and the rotation speed to stabilize, for example, 10 (sec), if necessary, and then determines whether it is necessary to continue the rotation speed control operation (step S107). This determination uses a condition A that determines whether or not the maximum value of the inverter output current absolute value during one second in step S101 is larger than a known limit start current. If it is determined by the first determination (step S102) that the actual rotational speed is greater than a predetermined N1, it is determined whether it is greater than N2 that is the upper limit of the rotational speed to be controlled (step S104). Note that N2 is a value set in advance by experiments and simulations in the same manner as N1, and if it is determined from FIG. 1, a value around 120 (rps) is appropriate.

  If the actual rotational speed is larger than the predetermined rotational speed N2 that is the upper limit of the rotational speed to be controlled, there is a possibility that the current margin becomes small at that rotational speed and the motor must be stopped. Therefore, the rotational speed is decreased by a predetermined rotational speed N4, for example, 10 (rps) (step S106). After this step, if necessary, it takes a time for the temperature to stabilize, for example, 10 (sec), and thereafter, it is determined whether it is necessary to continue the rotational speed control operation (step S107). This condition A is as described above.

If the above determination (step S104) is not satisfied, that is, if the actual operation speed of the electric compressor is N1 or more and N2 or less , switching is performed even though the switching element cooling effect by the refrigerant of the electric compressor is high. Since the maximum current value (absolute value) output by the inverter is large up to 0.9 times the rated current of the element, no further cooling effect can be expected, and the electric compressor is given priority to protection of the switching element. Is stopped (step S105).

  If the above steps (steps S101 to S107) other than the case of stopping the electric compressor are executed, the electric compressor can be controlled while suppressing the heat generation of the switching element. For this reason, the inverter output current also has a margin with respect to the limit, and becomes stable. In order to grasp the state, a condition B is used in which the maximum value of the inverter output current absolute value in one second is smaller than the rated current of the switching element previously known × 0.85 (step S108). This is referred to as a release condition for convenience. The release condition can also be said to be a condition for starting a step (step S109 or step S113) after releasing the control (steps S101 to S107) that keeps the rotational speed of the electric compressor within a predetermined range. Moreover, since the rated current of the switching element is lowered due to the temperature of the refrigerant, the temperature outside the electric compressor, or the like, or the heat generation of the switching element, the conditions A and B are set in consideration of that.

When the release condition is satisfied, a comparison determination is made between the actual operation rotational speed and the required rotational speed. When the actual operation rotational speed is larger than the required rotational speed, the rotational speed is lowered by a predetermined rotational speed, for example, 2 (rps) (step S114). On the other hand, when the actual operation rotational speed is not larger than the required rotational speed, the rotational speed is increased by a predetermined rotational speed, for example, 2 (rps) (step S115). After these steps S114 and S115, it is necessary to take a time for the temperature to stabilize, for example, 10 (sec) as necessary, and to continue the rotation speed control operation again (whether the same limit control condition as in step S107 is satisfied) Whether or not ) is determined (step S116). This is because it is determined whether or not the inverter output current is to be increased by adjusting the actual operation speed and the required speed.

When it is necessary to continue the rotation speed control operation (the restriction control condition is satisfied ) , the control is shifted to step S102 in order to control the rotation speed so that the switching element cooling effect is high. In these steps (steps S113, S114, and S115), the rotational speed limit control is canceled separately from the rotational speed command from the HVAC main control circuit by the rotational speed limit control. In this case, it is intended to prevent a sudden change in the rotational speed from occurring in the compressor.

  If the condition is not satisfied in the determination in step S116, it is determined whether or not the actual operation rotational speed is the same as the required rotational speed (step S117). A series of controls are terminated so as to maintain the number of rotations (step S118). If the actual rotational speed is different from the required rotational speed, the control is shifted to step S113 so as to be the same. In determining whether or not the actual operation speed is the same as the requested speed, it is unrealistic to request that the actual speed is exactly the same. It is preferable to do this.

Returning to step S108, if the release condition is not satisfied, it is necessary to first hold the rotational speed (step S109) and continue the rotational speed control operation again (whether the rotational speed limit control condition is satisfied ). (Step S110), and if necessary ( if satisfied ) , the control is transferred to step S102 in order to control the rotational speed to fall between the desired rotational speeds N1 and N2. If it is not necessary to continue the rotational speed control operation (if the rotational speed restriction control condition is not satisfied ) , it is determined again whether the release condition is satisfied (step S111), and if satisfied, the release condition is determined in step S108. As in the case where the above is satisfied, control is passed to step S113.

  If the release condition is not satisfied even in step S111, it is determined in step S109 whether the rotation speed has been maintained for a sufficient time T1, and if sufficient, the control is transferred to step S113. Control is transferred to S109 to sufficiently maintain the number of rotations. In the series of steps (steps S109 to S112), since the rotation speed of the electric compressor is not immediately stabilized due to the influence of a control circuit placed in a high temperature environment, the rotation speed limit control is continued while maintaining the rotation speed for the time being. This is a step for determining whether this is appropriate or whether it is appropriate to control with the release condition. The sufficient time may be about 1 minute empirically.

  If it carries out as mentioned above, in the control device of the electric compressor carried in one with the case of an electric compressor, the relation with the number of rotations of a compressor and the refrigerant circulation function of an electric compressor is considered. The switching elements constituting the control device can be protected from excessive heat generation. In addition, since the motor is rotated using the rotation speed range with the highest cooling capacity, the current value that can be passed can be afforded, and the rate of motor stoppage can be reduced. Value is improved. When the inverter temperature is used as the condition A or the condition B when the rotation speed limit control is performed, in step S101, S107, S108, S110, S111, and S116 in FIG. 4, is the inverter temperature larger than a predetermined value? It can be replaced with the condition of small.

  The control device for the electric compressor according to the present invention includes a control device that controls the motor (compressor) rotation speed and the like of the electric compressor used for refrigerant circulation of the vehicle-mounted air conditioner, and in particular, a switching element that constitutes an inverter. It is suitable for production and use of a control device for an electric compressor that is integrally mounted on the casing of the electric compressor.

It is an external view which shows the electric compressor with which the control apparatus was integrated with the housing | casing. It is a graph which shows the relationship between the rotation speed of an electric compressor, and the electric current margin with respect to an overcurrent, a horizontal axis is rotation speed (rps) and a vertical axis | shaft is a current margin (Arms). It is a block diagram which shows the positioning of the rotation speed restriction | limiting control part with respect to the whole control of an electric compressor. It is a flowchart which shows the control process which a rotation speed restriction | limiting control part performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric compressor 2 Case 3 Board | substrate 4 Box-shaped part 5, 6, 7 Compression load curve 8 HVAC (air conditioning apparatus)
9 Rotational speed control unit 10 Inverter 11 Electric motor 12 Rotational speed limit control units N1 to N4 Predetermined rotational speed

Claims (3)

A control device having a rotation speed control unit that controls the rotation speed of the electric compressor based on the difference between the motor rotation speed command from the main controller of the air conditioner and the motor rotation speed calculated from the motor stator current. In the control device for the electric compressor in which the board that physically configures the control device is housed in the casing of the electric compressor,
The rotation speed control unit is an inverter output current or a switching element that represents a state in which protection of the switching element constituting the control device is required regardless of the motor rotation speed command from the main control device of the air conditioner When a certain condition A related to temperature is satisfied, the electric motor is operated within a rotation speed between a predetermined upper limit rotation speed and a lower limit rotation speed in which the cooling capacity by the refrigerant circulation exceeds the heat generation of the switching element and a current margin is generated. It has a rotational speed limiting control unit for maintaining the rotational speed of the compressor, and,
The constant condition A is a condition that the maximum value of the absolute value of the inverter output current during one second exceeds a predetermined ratio value with respect to the rated current of the switching element, which is known in advance. Control device. The rotation speed limit control unit, when the constant condition A is not satisfied, and when the constant condition B regarding the inverter output current or the switching element temperature indicating the stable state of the switching element is satisfied, When the actual operating speed is larger than the required rotational speed, the actual operating speed is decreased by a certain rotational speed, and the actual operating speed is reduced to the required rotational speed. If it is smaller, increase the actual operation speed by a fixed speed , and
The constant condition B is a condition that the maximum value of the inverter output current absolute value in one second is a value smaller than a constant ratio with respect to the rated current of the switching element employed in the constant condition A. The control device for an electric compressor according to claim 1 . The rotation speed limit control unit is the case where the constant condition A is not satisfied, and when the constant condition A regarding the inverter output current or the switching element temperature indicating the stable state of the switching element is not satisfied, the constant condition A While maintaining the rotation speed when the engine is no longer satisfied, it is determined whether or not the predetermined condition A is satisfied, and if the predetermined condition A is satisfied, it is between the predetermined upper limit rotation speed and the lower limit rotation speed. Maintaining the rotational speed of the electric compressor within the rotational speed ; and
The constant condition B is a condition that the maximum value of the inverter output current absolute value in one second is a value smaller than a constant ratio with respect to the rated current of the switching element employed in the constant condition A. The control apparatus for an electric compressor according to claim 1 or 2 .

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