Electric motor controller in electric compressor |
|||||||
申请号 | EP06113164.5 | 申请日 | 2006-04-26 | 公开(公告)号 | EP1724916B1 | 公开(公告)日 | 2008-12-31 |
申请人 | KABUSHIKI KAISHA TOYOTA JIDOSHOKKI; | 发明人 | Fukasaku, Hiroshi; Najima, Kazuki; Kawashima, Takashi; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | The present invention relates to an electric motor controller in an electric compressor. Specifically, the present invention relates to an electric motor controller installed in an electric compressor that compresses and discharges refrigerant in a compression chamber by compressing action of a compression member based on rotation of a rotary shaft rotated by the electric motor, and cools coils of the electric motor with the refrigerant. To protect coils of the electric motor in an electric compressor from electrical breakdown due to overheating, a measure has been proposed in which the electric compressor is stopped before the coils are overheated. However, if the electric compressor is stopped, the flow of refrigerant is stopped. This reduces the rate of decrease in the temperature of the coils, and thus extends the stopping period of the electric compressor. Therefore, the control, which stops the electric compressor, is not preferable. When an electric compressor is activated, a control for maximizing the displacement (maximum load operation) is normally performed. For a certain time after the activation, the amount of refrigerant circulation for cooling the coils is not sufficient. Therefore, if the ambient temperature is high when the electric compressor is activated, since the maximum load operation supplies a current of a maximum current value to the coils, the temperature of the coils are raised before coolant lowers the coil temperature. As a result, the coil temperature reaches a stop temperature set for preventing overheating after a short period from the activation. This stops the electric compressor. Document Document It is an objective of the present invention to provide an electric motor controller that is capable of protecting the coil of an electric motor without stopping the operation of an electric compressor immediately after activation. According to an aspect of the present invention, a controller for an electric motor in an electric compressor is provided as defined in claim 1. Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
A first embodiment of the present invention will now be described with reference to As shown in The discharge chamber 17 is connected to a suction chamber 181 in a motor housing 18 by an external refrigerant circuit 19. A heat exchanger 20 for drawing heat from refrigerant, an expansion valve 21, and a heat exchanger 22 for transferring the ambient heat to refrigerant are located on the external refrigerant circuit 19. Refrigerant in the discharge chamber 17 flows out to the external refrigerant circuit 19, and then returns to the suction chamber 181. Refrigerant conducted into the suction chamber 181 is drawn into the compression chambers 14 through a suction port 23. A rotor 24 of the electric motor M is attached to the rotary shaft 12, and a stator 25 of the electric motor M is fixed to the inner circumferential surface of the motor housing 18. The rotor 24 includes a rotor core 241 attached to the rotary shaft 12 and permanent magnets 242 provided on the circumferential surface of the rotor core 241. The permanent magnets 242 are arranged such that each adjacent pair along the circumferential direction of the rotor core 241 have different magnetic poles facing the stator 25. The stator 25 of the electric motor M includes an annular stator core 251 and a coil 252 wound about the stator core 251. The rotor 24 rotates when electricity is supplied to the coil 252, and the rotary shaft 12 rotates integrally with the rotor 24. Electricity is supplied to the coil 252 by an inverter 26. A temperature detector 27 is located inside the motor housing 18. The temperature detector 27 detects the temperature about the coil 252. Temperature information detected by the temperature detector 27, which functions as a temperature detection section, is sent to a control computer C. Based on the temperature information detected by the temperature detector 27, the control computer C controls supply of electricity to the electric motor M by the inverter 26. The control computer C is connected to and exchanges signals with an air-conditioner switch 28, a compartment temperature detector 29, and a compartment temperature setting device 30. When the air-conditioner switch 28 is ON, the control computer C controls current supplied from the inverter 26 based on the difference between a target compartment temperature set by the compartment temperature setting device 30 and the temperature detected by the compartment temperature detector 29. The control computer C stands by until the air-conditioner switch 28 is turned ON and an activation command is sent to the control computer C (step S1). When receiving an activation command (YES at step S1), the control computer C reads information related to a temperature Θx that has been detected by the temperature detector 27 prior to the activation of the electric motor M (step S2). The control computer C compares the detected temperature Θx with a predetermined reference temperature Θo (step S3). The reference temperature Θo is set lower than a protection temperature for preventing the coil 252 from being burnt. If the detected temperature Θx is less than or equal to the reference temperature Θo (NO at step S3), the control computer C executes a control of current supply (non-limiting control) for controlling the inverter 26, in which Imax is set as an upper limit value (limiting value) at step S4. Imax is a maximum value (maximum upper limit value) of the current that can be supplied to the coil 252. When the target compartment temperature and the detected temperature are largely different from each other, the current supply control (non-limiting control), in which the current value Imax can be supplied, is started. The control computer C determines whether it has received an operation stopping command that accompanies turning OFF of the air-conditioner switch 28 (step S5). If the control computer C has not received an operation stopping command (NO at step S5), the control computer C proceeds to step S4 and continues the non-limiting control. If the control computer C has received an operation stopping command (YES at step S5), the control computer C stops the operation of the electric motor M (step S6). Accordingly, the operation of the electric scroll compressor 10 is stopped. If the detected temperature Θx that has been detected prior to the activation of the electric motor M is higher than the reference temperature Θo (YES at step S3), the control computer C executes a control of current supply (limiting control) for controlling the inverter 26, in which Ao × Imax is set as an upper limit value (limiting value) at step S7. Ao is greater than 0, and less than 1. In this manner, the control computer C starts the current supply control in which the current value is less than or equal to the upper limit value (limiting value) Ao × Imax. During the limitation operation, even if the difference between a target compartment temperature and a detected temperature is great, a current that is greater than or equal to Ao × Imax is not supplied to the coil 252. The horizontal axis in the graph of The control computer C determines whether an elapsed time Tx from the start of the limiting control has reached a predetermined reference time To (step S8). If the elapsed time Tx has not reached the reference time To (NO at step S8), the control computer C determines whether it has received an operation stopping command that accompanies turning OFF of the air-conditioner switch 28 (step S9). If the control computer C has not received an operation stopping command (NO at step S9), the control computer C proceeds to step S7 and continues the limiting control. If the control computer C has received an operation stopping command (YES at step S9), the control computer C proceeds to step S6 and stops the operation of the electric scroll compressor 10. When the elapsed time Tx reaches the reference time To (NO at step S8), the control computer C shifts from the limiting control in which Ao x Imax is set as the upper limit value (limiting value) to the non-limiting control in which the Imax is set as the upper limit value (step S4). If the control computer C has not received an operation stopping command (NO at step S5), the control computer C proceeds to step S4 and continues the non-limiting control. If the control computer C has received an operation stopping command (YES at step S5), the control computer C stops the operation of the electric scroll compressor 10 (step S6). As described above, when temperature Θx detected by the temperature detector 27 reaches the predetermined reference temperature Θo, the control computer C functions as a limiting section that executes the limiting control to limit the upper limit value of current supplied to the coil 252 to the limiting value Ao × Imax, which is less than the maximum upper limit value Imax. The first embodiment provides the following advantages.
If the temperature of the coil 252 is suppressed to a value less than or equal to a maximum safety temperature (protection temperature) when a current of a constant limiting value Ao × Imax is supplied, the limiting value Ao × Imax at the time is adopted. Further, a time from the activation to when the circulation of refrigerant reaches all the sections may be adopted as the reference time To. In this manner, the limiting value Ao × Imax is easily defined (selected) through experiments in which the limiting value Ao × Imax is constant. That is, in a control in which the limiting value Ao × Imax is constant, it is easy to select a limiting value that suppress a temperature increase of the coil 252 to a value less than or equal to the maximum safety temperature. Also, a value of the reference time To is easily defined (selected) through experiments. That is, in a control in which the limiting control is cancelled when the reference time To has elapsed from the start of the limiting control, it is easy to select a reference time for suppressing a temperature increase of the coil 252 to a value less than or equal to the maximum value of the safety temperature. Further, in a period from the start of the limiting control to when the reference time To has elapsed, the limiting control with the limiting value Ao × Imax is continued. Therefore, compared to a case where a limiting value is gradually increased as in another embodiment described below, the temperature increase of the coil 252 is suppressed. A second embodiment according to the present invention will now be described with reference to flowcharts of In the second embodiment, the process from step S1 to step S4 (YES at S1 → S2 → NO at S3 → S4), and the process from step S1 to step S9 (YES at S1 → S2 → YES at S3 → S7 → NO at S8 → S9) are identical to those of the first embodiment. The process after step S4 is different from that in the first embodiment. As shown in If the detected temperature Θx is higher than the reference temperature Θo (YES at step S11), the control computer C executes a current supply control (limiting control) for controlling the inverter 26, in which A1 × Imax (A1 ≠ Ao) is set as an upper limit value (step S13). A1 is, for example, greater than Ao, and less than 1. As shown in If the detected temperature Θx is less than or equal to the reference temperature Θ1 (NO at step S16), the control computer C shifts the control for controlling the inverter 26 from the limiting control, in which A1 Imax is set to the upper limit value, to a non-limiting control, in which Imax is set to the upper limit value (step S17). Then, the control computer C determines whether it has received an operation stopping command (step S18). If the control computer C has not received an operation stopping command (NO at step S18), the control computer C proceeds to step S15. If the control computer C has received an operation stopping command (YES at step S18), the control computer C stops the operation of the electric scroll compressor 10 (step S19). In the second embodiment, the limiting control at the activation of the electric scroll compressor 10 (activation of the electric motor M) is the same as the first embodiment. However, in the operation after the activation, if the detected temperature Θx surpasses the reference temperature Θ1 (YES at step S16), the limiting control is executed at step S13. That is, the control computer C selects one of the limiting control and the non-limiting control not only at the activation but also in the operation after the activation based on the temperature about the coil 252 (step S16). Therefore, the coil 252 is prevented from excessively heated not only during the activation but also during the operation after the activation without stopping the operation. The invention may be embodied in the following forms.
Although the multiple embodiments have been described herein, it will be clear to those skilled in the art that the present invention may be embodied in different specific forms without departing from the spirit of the invention. The invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. A coil (252) of an electric motor (M) is cooled by refrigerant. A controller for the electric motor (M) controls a current supplied to the coil (252) within a range less than or equal to a predetermined maximum value (Imax). A temperature detection section (27) detects either a temperature of the coil (252) or a temperature about the coil (252). When a detection temperature (Θx) that is detected by the temperature detection section (27) prior to activation of the electric motor (M) reaches a predetermined reference temperature (Θo), a limiting section (C) executes a limiting control to limit an upper limit value of the current supplied to the coil (252) to a limiting value that is less than the maximum value (Imax). Accordingly, the coil of the electric motor is protected without stopping the operation of the electric compressor immediately after activation ( |