阅读说明：本技术 电动压缩机 (Electric compressor ) 是由 川田顺贵 于 2018-12-07 设计创作，主要内容包括：本发明在防止开关元件破损的同时,迅速地使压缩机构的旋转停止。电动压缩机(1)包括具有多个开关元件IGBT(Q1～Q6)的电动机驱动电路(52)、控制多个开关元件IGBT(Q1～Q6)的驱动从而驱动电动机(4)的控制部(53)、以及检测流过电动机驱动电路(52)的电流的电流检测单元(54)。控制部(53)通过进行控制多个开关元件IGBT(Q1～Q6)中的规定的开关元件IGBT(Q2、Q4、Q6等)的驱动的制动控制,执行使压缩机构(3)的旋转停止的停止控制。控制部(53)在所述制动控制中,在检测电流值I低于第1阈值I<Sub>1</Sub>的情况下,调整所述规定的开关元件IGBT(Q2、Q4、Q6等)的驱动模式,以使得检测电流值I不超过比第1阈值I<Sub>1</Sub>要低的第2阈值I<Sub>2</Sub>。(The invention prevents the switch element from being damaged and stops the rotation of the compression mechanism rapidly. The electric compressor (1) is provided with a motor drive circuit (52) having a plurality of switching element IGBTs (Q1-Q6), a control unit (53) for controlling the drive of the plurality of switching element IGBTs (Q1-Q6) to drive a motor (4), and a current detection means (54) for detecting a current flowing through the motor drive circuit (52). The control unit (53) performs braking control for controlling the drive of predetermined switching element IGBTs (Q2, Q4, Q6, and the like) among the plurality of switching element IGBTs (Q1-Q6), thereby executing stop control for stopping the rotation of the compression mechanism (3). The control unit (53) controls the braking such that the detected current value I is lower than a 1 st threshold value I 1 In the case of (2), adjusting the regulationSo that the detected current value I does not exceed the 1 st threshold value I, the drive mode of the switching element IGBT (Q2, Q4, Q6, etc.) 1 2 nd threshold I to be low 2 。)

1. An electric compressor comprising:

a compression mechanism that compresses a refrigerant by rotation and discharges the compressed refrigerant;

a motor that drives the compression mechanism;

a motor drive circuit connected between the motor and a direct-current power supply and having a plurality of switching elements; and

a control unit that executes motor drive control for driving the motor by controlling the drive of the plurality of switching elements in response to an external compressor operation command, and stop control for stopping the rotation of the compression mechanism by performing brake control for controlling the drive of a predetermined switching element among the plurality of switching elements to apply a load to the motor after all the switching elements are turned off in response to an external compressor stop command,

the electric compressor is characterized in that it is provided with,

includes a current detection unit for detecting a current flowing through the motor drive circuit,

in the braking control, the control unit turns off all the switching elements when the detected current value detected by the current detection means is higher than a predetermined 1 st threshold value,

in the braking control, when the detected current value is lower than the 1 st threshold value, the control unit adjusts the drive mode of the predetermined switching element so that the detected current value does not exceed a predetermined 2 nd threshold value lower than the 1 st threshold value.

2. The motor-driven compressor according to claim 1,

the 2 nd threshold is a peak value of a starting current generated at the time of starting in the motor drive control.

3. Motor compressor according to claim 1 or 2,

the adjustment of the drive mode of the predetermined switching element in the braking control is performed by changing, for each predetermined period, a duty ratio at which a time period indicating an on state of the predetermined switching element is a proportion of the predetermined period.

4. The motor-driven compressor according to claim 3,

when the braking control is started, the control unit increases the duty ratio by a predetermined ratio when the detected current value is equal to or less than the 2 nd threshold value after the predetermined switching element is turned on for a period of time based on an initial duty ratio predetermined for the duty ratio, and maintains the duty ratio or decreases the duty ratio by the predetermined ratio when the detected current value is higher than the 2 nd threshold value.

5. Motor compressor according to any one of claims 1 to 4,

the plurality of switching elements are configured to have a pair of high-side elements and low-side elements of the same phase connected in series corresponding to a plurality of phases in parallel between a high-voltage line and a ground line of the direct-current power supply,

the predetermined switching elements to be adjusted in the drive mode are all the high-side elements or all the low-side elements,

as the braking control, the control unit executes zero-vector energization that brings all of the high-side devices or all of the low-side devices into an on state simultaneously and intermittently.

Technical Field

The present invention relates to an electric compressor used for compressing a refrigerant in an air conditioner for a vehicle or the like and including an inverter and a motor, and more particularly to braking control of the motor.

Background

As such an electric compressor, for example, an electric compressor described in patent document 1 is known. The electric compressor described in patent document 1 converts dc power from a dc power supply into three-phase ac power by an inverter, and supplies the three-phase ac power to a motor for driving the compressor. In such an electric compressor, it is known that, when the compressor is stopped, the compression mechanism rotates in reverse due to a pressure difference between a suction pressure region and a discharge pressure region of refrigerant in the compression mechanism, and abnormal noise may be generated due to the reverse rotation.

In this regard, in the electric compressor described in patent document 1, as a measure for preventing the occurrence of the reverse rotation and the abnormal noise, the brake control is performed when the compressor is stopped. Specifically, in the electric compressor, when a compressor stop command is input from the outside, the energization of the plurality of switching elements constituting the inverter is cut off, and thereafter, zero-vector energization or direct-current excitation energization is performed as the braking control. That is, in the electric compressor, all of the switching elements on the positive voltage side or the negative voltage side among the plurality of switching elements are energized during the zero vector energization, and one switching element on the positive voltage side and one switching element on the negative voltage side are energized during the dc excitation energization, thereby preventing the reverse rotation of the compression mechanism.

Disclosure of Invention

Technical problem to be solved by the invention

However, when the energization of all the switching elements is cut off in response to an external compressor stop command as in the electric compressor described in patent document 1, the compression mechanism rotates due to inertia. Therefore, in this state, when the braking control (the zero vector energization or the dc excitation energization) is performed, the rotational energy of the compression mechanism appears as a current (may also be referred to as a so-called regenerative current) flowing through the circuit of the inverter. Therefore, when the rotation of the compression mechanism is abruptly stopped by the brake control, the current flowing through the circuit of the inverter is abruptly increased, and an excessive current may flow through the switching element constituting the circuit of the inverter. In this case, the switching element may be damaged, and it is necessary to investigate this.

In view of such circumstances, an object of the present invention is to provide an electric compressor capable of quickly stopping rotation of a compression mechanism while preventing a switching element from being damaged.

Technical scheme for solving technical problem

According to one aspect of the present invention, there is provided a motor-driven compressor including: a compression mechanism that compresses a refrigerant by rotation and discharges the compressed refrigerant; a motor that drives the compression mechanism; a motor drive circuit connected between the motor and a direct-current power supply and having a plurality of switching elements; and a control unit that executes motor drive control for driving the motor by controlling the drive of the plurality of switching elements in response to an external compressor operation command, and stop control for stopping the rotation of the compression mechanism by performing brake control for controlling the drive of a predetermined switching element among the plurality of switching elements to apply a load to the motor after all the switching elements are turned off in response to an external compressor stop command. The motor-driven compressor includes a current detection unit that detects a current flowing through the motor drive circuit. In the braking control, the control unit turns off all the switching elements when the detected current value detected by the current detecting means is higher than a predetermined 1 st threshold value. In the braking control, when the detected current value is lower than the 1 st threshold value, the control unit adjusts the drive mode of the predetermined switching element so that the detected current value does not exceed a predetermined 2 nd threshold value lower than the 1 st threshold value.

Effects of the invention

In the electric compressor according to one aspect of the present invention, when the detected current value detected by the current detecting means is higher than a predetermined 1 st threshold value during the braking control by the control unit, the control unit forcibly turns off all the switching elements. Therefore, for example, the breakage of the switching element can be reliably prevented by setting the 1 st threshold to a value sufficiently lower than a value of breakage or the like of the switching element. In the braking control, when the detected current value is lower than the 1 st threshold value, the control unit adjusts the drive mode of the predetermined switching element so that the detected current value does not exceed a predetermined 2 nd threshold value lower than the 1 st threshold value. Therefore, since the braking control can be continued while the breakage of the switching element is reliably prevented, the rotation of the compression mechanism can be quickly stopped, and the reverse rotation of the compression mechanism and the occurrence of abnormal noise caused by the reverse rotation can be quickly prevented or suppressed.

Thus, the electric compressor can be provided, which can reliably prevent the switch element from being damaged and can rapidly stop the rotation of the compression mechanism.

Drawings

Fig. 1 is a view showing a schematic external view of an electric compressor according to an embodiment of the present invention.

Fig. 2 is a schematic circuit diagram of a motor drive circuit including the electric compressor.

Fig. 3 is a schematic diagram showing a state in a case where an overcurrent flows through the motor drive circuit at the time of stop control.

Fig. 4 is a schematic diagram showing a state in which the overcurrent is prevented from flowing through the motor drive circuit at the time of stop control.

Fig. 5 is a flowchart for explaining an outline of the control operation of the control unit.

Fig. 6 is a flowchart for explaining an operation of the stop control by the control unit.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 shows an outline of an external appearance of an electric compressor according to an embodiment of the present invention.

The electric compressor 1 in the present embodiment is incorporated in a refrigerant circuit of a vehicle air conditioner, for example, and sucks in a refrigerant of the vehicle air conditioner, compresses the refrigerant, and discharges the refrigerant. The electric compressor 1 is a so-called inverter-integrated electric compressor, and includes a housing 2, a compression mechanism 3 that compresses and discharges a refrigerant by rotation, a motor 4 that drives the compression mechanism 3, and an inverter 5 that supplies power to the motor 4.

The housing 2 houses the compression mechanism 3, the motor 4, and the inverter 5 therein. In the present embodiment, the housing 2 is configured to include a main housing 2A, an inverter housing 2B, and cover members 2C, 2D. These (2A to 2D) are integrally fastened by bolts or the like.

The main casing 2A accommodates a compression mechanism 3 and a motor 4. The compression mechanism 3 and the motor 4 are arranged in series along the central axis X of the drive shaft 4a of the motor 4. The inverter case 2B accommodates an inverter 5 therein. Thus, the electric motor 4 is disposed between the compression mechanism 3 and the inverter 5 in the housing 2. The inverter case 2B is formed of a cylindrical portion and a bottom wall portion on one end side thereof. The opening portion on the other end side of the cylindrical portion of the inverter case 2B is closed by a cover member 2D. Therefore, the region inside the housing 2 is partitioned by the bottom wall portion of the inverter housing 2B into a 1 st space S1 accommodating the compression mechanism 3 and the motor 4 and a 2 nd space S2 accommodating the inverter 5.

The compression mechanism 3 is, for example, a scroll-type compression mechanism having a fixed scroll and an orbiting scroll which are engaged with each other, and is connected to the drive shaft 4 a. The orbiting scroll is connected to a drive shaft 4a so as to be capable of orbiting around the axial center of the fixed scroll, and a compression chamber is formed between the orbiting scroll and the fixed scroll. The volume of the compression chamber is changed by the orbiting scroll performing the orbiting scroll movement. Then, the low-pressure refrigerant sucked into the main casing 2A from the low-pressure portion of the refrigerant circuit through the suction port, not shown, is compressed in the compression chamber and guided to the central portion of the compression mechanism 3. The refrigerant guided to the center portion of the compression mechanism 3 is discharged to the high-pressure portion of the refrigerant circuit through a discharge port, not shown.

The motor 4 is composed of, for example, a 3-phase brushless motor, and has a U-phase coil, a V-phase coil, and a W-phase coil connected in a star configuration.

Fig. 2 is a schematic diagram of a circuit of the inverter 5 including a motor drive circuit 52 described later in the present embodiment.

The inverter 5 converts dc power from an external dc power supply B, such as a battery, not shown, into three-phase ac power, and supplies the three-phase ac power to the motor 4. The inverter 5 has a smoothing capacitor 51, a motor drive circuit 52, a control unit 53 for controlling the drive of the motor drive circuit 52, and a current detection means 54 as its circuit configuration.

The capacitor 51 smoothes a dc voltage from an external dc power supply B, and supplies the smoothed dc voltage to the motor drive circuit 52.

The motor drive circuit 52 is connected between the motor 4 and the dc power supply B, and includes a plurality of switching elements, i.e., identical Insulated Gate bipolar transistors (hereinafter referred to as "IGBTs") Q1 to Q6.

The driving (on/off) of each of IGBTQ1 to Q6 as the plurality of switching elements is controlled by control unit 53, and thereby the dc voltage from capacitor 51 is converted into an ac voltage and supplied to motor 4. IGBTQ1 to Q6 are divided into a U-phase arm, a V-phase arm, and a W-phase arm connected in parallel to each other between a high-voltage line H (in other words, a high-voltage-side line) and a ground line L (in other words, a ground-side line) of a dc power supply B. Capacitor 51 is connected to a portion closer to dc power supply B than a connection point of U-phase arm in high-voltage line H and ground line L.

The U-phase arm includes two IGBTs (Q1, Q2) connected in series between a high-voltage line H and a ground line L. For two IGBTs (Q1, Q2), diodes D1, D2 are connected in anti-parallel with the IGBTs, respectively.

The V-phase arm also includes two IGBTs (Q3, Q4) connected in series between the high-voltage line H and the ground line L. For two IGBTs (Q3, Q4), diodes D3, D4 are connected in anti-parallel with the IGBTs, respectively.

The W-phase arm also includes two IGBTs (Q5, Q6) connected in series between the high-voltage line H and the ground line L. For two IGBTs (Q5, Q6), diodes D5, D6 are connected in anti-parallel with the IGBTs, respectively.

In the present embodiment, the IGBTs (Q1, Q3, Q5) correspond to "high-side elements" (in other words, power-side elements) according to the present invention, the IGBTs (Q2, Q4, Q6) correspond to "low-side elements" (in other words, ground-side elements) according to the present invention, and the IGBTs (Q1, Q2), the IGBTs (Q3, Q4), and the IGBTs (Q5, Q6) correspond to "a pair of high-side elements and low-side elements in the same phase" according to the present invention, respectively. In this way, the motor drive circuit 52 is configured such that the motor drive circuit 52 includes a pair of high-side elements and low-side elements (IGBTs (Q1, Q2), IGBTs (Q3, Q4), and IGBTs (Q5, Q6)) connected in series and having the same phase, in parallel, between the high-voltage line H and the ground line L of the dc power supply B, and corresponding to the three phases.

The U-phase arm, the V-phase arm, and the W-phase arm are connected at their respective intermediate points to one end of the coil of the corresponding phase of the motor 4. That is, the intermediate point of the IGBT (Q1, Q2) is connected to the U-phase coil, the intermediate point of the IGBT (Q3, Q4) is connected to the V-phase coil, and the intermediate point of the IGBT (Q5, Q6) is connected to the W-phase coil.

The controller 53 controls the driving of the motor drive circuit 52, and executes motor drive control for supplying electric power to the motor 4 to drive the motor 4, and stop control for stopping the rotation of the compression mechanism 3 (specifically, the orbital rotation of the orbiting scroll).

In the motor drive control, the control unit 53 controls the driving of IGBTQ1 to Q6 as a plurality of switching elements in response to a compressor operation command from the outside of the vehicle air-conditioning control device or the like, thereby driving the motor 4. For example, in the motor drive control, the controller 53 converts the dc voltage from the capacitor 51 into an ac voltage by PWM control of IGBTQ1 to Q6 (control for generating a voltage modulated with a pulse width at a constant cycle so as to obtain a sine wave approximately), and supplies the ac voltage to the motor 4 to drive the motor 4. Specifically, in the motor drive control, controller 53 generates an approximate ac voltage by controlling the ratio of the on period (conduction period) of the IGBTs (Q1, Q3, Q5) as the high-side elements and the on period (conduction period) of the IGBTs (Q2, Q4, Q6) as the low-side elements in each phase arm, based on the sinusoidal voltage supplied to U, V, W for each phase.

In the stop control, the controller 53 stops the rotation of the compression mechanism 3 (the orbiting movement of the orbiting scroll) by performing brake control for applying a load to the motor 4 by controlling the driving of a predetermined switching element (hereinafter, appropriately referred to as a brake control element) of the IGBTQs 1 to Q6 after all of the IGBTQs 1 to Q6 are put into an off state (power-on/off state) in response to a compressor stop command from the outside of the vehicle air-conditioning control device or the like. That is, when a signal of a compressor stop command is input from the outside in the motor drive control, the controller 53 switches to the stop control mode, and first controls the driving of IGBTQ1 to Q6 so that all IGBTQ1 to Q6 are in the off state. Thereby, the compression mechanism 3 is in the inertial rotation state. The control unit 53 applies a load to the motor 4 by performing the braking control for controlling the driving of the braking control element in a state where the compression mechanism 3 is performing the inertial rotation. As a result, a braking force against the inertial rotation of the compression mechanism 3 connected to the motor 4 is generated, and the rotation of the compression mechanism 3 is stopped. The magnitude of the braking force for the rotation of the compression mechanism 3 generated by the braking control is determined based on the characteristics of the compression mechanism 3, the motor 4, the on period of the braking control element, and the like. The details of the stop control including the braking control in the control unit 53 and the braking control elements will be described in further detail later.

The current detection unit 54 is used to detect the current flowing through the motor drive circuit 52, and may be a suitable method such as a method of detecting by a shunt resistor provided in the motor drive circuit 52 or a method of detecting by a current sensor. In the present embodiment, the current detection means 54 is formed by a so-called single shunt method in which a shunt resistance is used. Specifically, the current detection means 54 is constituted by one shunt resistor 54a provided on the ground line L connecting the motor drive circuit 52 and the ground side of the dc power supply B, and a current detection portion 54B that detects a current (phase current) flowing through the shunt resistor 54 a. A signal corresponding to the detected current value I detected by the current detecting section 54b is input to the control section 53. When the shunt resistor is used, the shunt resistor is not limited to the single shunt method, and may be a 3-shunt method. In this case, although not shown, the shunt resistors 54a are provided between the IGBTs (Q2, Q4, Q6) as the low-side elements in the motor drive circuit 52 and the ground line L.

As described above, after the control unit 53 drives all of the IGBTQs 1 to Q6 to the off state in response to the compressor stop command from the outside, the compression mechanism 3 is rotated by inertia. Therefore, in this state, as shown in fig. 3, as the braking control, for example, control is performed in which all the low-side devices or all the high-side devices (in fig. 3, the low-side device IGBTs (Q2, Q4, Q6)) are simultaneously in a conductive state (also referred to as a Hi state). In this case, the rotational energy of the compression mechanism 3 appears as a current (which may also be referred to as a so-called regenerative current) flowing through the motor drive circuit 52. Here, if the braking force for the rotation of the compression mechanism 3 generated by the braking control is excessive, the rotation of the compression mechanism 3 is stopped promptly immediately after the braking control is started. That is, as shown in fig. 3, assuming that the control section 53 performs control of maintaining the low-side element IGBT (Q2, Q4, Q6) in an on state (in other words, driving the low-side element at a duty ratio of 100%) at the same time as the braking control, an overcurrent flows through the motor drive circuit 52. As shown in the lowest stage of fig. 3, the overcurrent appears as a sudden increase in the detected current value I detected by the current detection unit 54 b. As a result, the low-side device IGBTs (Q2, Q4, Q6) and the like may be broken by an overcurrent.

As a countermeasure against this problem, the control unit 53 of the present embodiment is configured to execute a control operation described in detail below.

Next, the stop control including the brake control performed by the control unit 53 will be described in detail with reference to fig. 4. Fig. 4 is a schematic diagram for explaining a current flowing through the motor drive circuit 52 at the time of the stop control.

In the braking control in the stop control, the control unit 53 controls the current detecting means 54 to detect a detected current value I higher than a predetermined 1 st threshold value I₁In the case of (3), all IGBTQ1 to Q6 are turned off.

Further, in the braking control, the control unit 53 detects that the current value I is lower than the 1 st threshold value I₁In the case of (1), the drive mode of the brake control element is adjusted so that the detected current value I does not exceed the 1 st threshold value I₁Defined 2 nd threshold value I to be low₂. As a result, as shown in the bottom of fig. 4, the peak value of the current flowing through the motor drive circuit 52 by the braking control is significantly reduced by Δ I from the peak value when the braking control element is driven at a duty ratio of 100% (in the case of fig. 3) as shown by the broken line.

In the present embodiment, all of the low-side device IGBTs (Q2, Q4, Q6) are used as the brake control elements of the predetermined switching elements to be adjusted in the drive mode.

In the present embodiment, the 1 st threshold value I₁The current value is set to a value lower than the current value that may cause the IGBT to break, for example, a value corresponding to an abnormal current value that may occur when an overload occurs in the motor 4. 2 nd threshold value I₂Set as the start generated at the start in the motor drive controlPeak value of the kinetic current. Due to the 2 nd threshold value I₂Is flowing through the motor drive circuit 52 at start-up, so that the 2 nd threshold I is set₂The current tolerant IGBTQ is selected as IGBTQ 1-Q6. In addition, the 2 nd threshold value I₂A rated current value I flowing through the motor drive circuit 52 during the motor drive control after the start₀Is high. I.e. 1 st threshold value I₁2 nd threshold I₂Rated current value I₀The relationship of (1) holds.

Specifically, the adjustment of the drive mode of all the low-side device IGBTs (Q2, Q4, Q6) in the braking control is performed by changing, for each predetermined period T, a duty ratio D at which the time indicating the on state of all the low-side device IGBTs (Q2, Q4, Q6) occupies a ratio of the predetermined period T.

More specifically, at the start of the braking control, the control section 53 controls the brake device to start at an initial duty ratio D predetermined based on the duty ratio D₀After all the low-side element IGBTs (Q2, Q4, Q6) are set to the on state, the detected current value I is lower than the 2 nd threshold value I₂When the duty ratio D is increased by a predetermined ratio Δ D, the detected current value I is higher than the 2 nd threshold value I₂In the case of (3), the duty ratio D is maintained or reduced by a predetermined ratio Δ D. In the present embodiment, the following case is explained as an example: when detected current value I is larger than 2 nd threshold value I, control unit 53₂When the duty ratio is high, the duty ratio D is decreased by a predetermined ratio Δ D.

More specifically, as the braking control, control unit 53 executes zero-vector energization that simultaneously and intermittently turns on all of the low-side device IGBTs (Q2, Q4, Q6). That is, the zero vector energization is not maintained as shown in fig. 3 but is released (turned off) by the period (time) corresponding to the duty ratio D for each cycle T as shown in fig. 4 in the brake control period.

Next, the control operation of the control unit 53 will be described in more detail with reference to fig. 4 to 6. Fig. 5 is a flowchart for explaining the entire control operation of the control unit 53, and fig. 6 is a flowchart for explaining the operation of the stop control performed by the control unit 53. The STEPs 1 and 2 described below correspond to the motor drive control, and the STEPs 3 to 7 correspond to the stop control.

When a signal of a compressor operation command from the outside such as a vehicle air conditioning control device is input to the control unit 53 (STEP1), the control unit 53 executes the motor drive control, and thereby supplies ac power to the motor 4 to drive (rotate) the motor 4 (STEP 2).

When a signal of a compressor stop command from the outside such as a vehicle air conditioning control device is input to the control unit 53 during execution of the motor drive control, the control unit 53 switches to the stop control mode. Then, in response to the signal of the compressor stop command, the control unit 53 immediately drives all of IGBTQ1 to Q6 to the off state (power-on off state) (STEP 3). At this time, the controller 53 starts counting the time t1 from the input time of the compressor stop command and proceeds to STEP 4.

In STEP4, control unit 53 determines whether or not the compressor stop command is a stop command based on a failure of the motor or the like or a protection function. If the compressor stop command is a stop command for a protection function due to a failure of the motor or the like, that is, if the compressor stop command is an abnormal stop (STEP 4: yes), the process proceeds to STEP5, and if the compressor stop command is not a stop command for a protection function due to a failure of the motor or the like (STEP 4: no), the process proceeds to STEP 6.

In STEP5, the control unit 53 does not execute the brake control (brake control non-operation), and directly sets all IGBTQ1 to Q6 to the off state, and the number of rotations of the compression mechanism 3 gradually decreases, and in the brake control non-operation state, the rotation of the compression mechanism 3 is stopped. In this case, since the electric compressor 1 is in an abnormal state, the braking control is not executed in order to prevent occurrence of a secondary failure or the like due to the braking control in this state.

In STEP6, the control unit 53 shifts to the state of the brake control (brake control operation) in the stop control. When the control unit 53 is in the brake control operation state, as shown in fig. 6, it is first determined whether or not a predetermined time t01(t1 > t01) has elapsed from the time t1 when the compressor stop command is input (STEP 61). When a predetermined time t01 has elapsed at time t1 (STEP 61: yes), the control unit 53 proceeds to STEP62 to start the execution of the braking control. On the other hand, when the predetermined time t01 has not elapsed at the time t1 (STEP 61: no), the controller 53 repeats STEP61 until the elapse. When a predetermined time t01 has elapsed from the time of input of the compressor stop command, the number of revolutions of the inertial rotation of the compression mechanism 3 is appropriately reduced compared to the number of revolutions immediately after the input of the compressor stop command. The predetermined time t01 can be determined as appropriate depending on the characteristics of the compression mechanism 3 and the motor 4, and the like.

In STEP62, based on the initial duty ratio D₀The time period of (2) causes all the low-side element IGBTs (Q2, Q4, Q6) to be driven to an on state. At this time, all the high side element IGBTs (Q1, Q3, Q5) are maintained in the off state. Initial duty cycle D₀The setting is made variable in the control unit 53, for example, about 50%. Then, the controller 53 starts counting time t2 from the start time of the braking control (i.e., the time when all the low-side device IGBTs (Q2, Q4, Q6) are turned on), and proceeds to STEP 63.

In STEP63, control unit 53 determines whether or not detected current value I detected by current detecting section 54 is higher than 1 st threshold value I₁. When the detected current value I is higher than the 1 st threshold value I₁In the case of (STEP 63: YES), the process proceeds to STEP 64. When the detected current value I is lower than the 1 st threshold value I₁If (STEP 63: NO), the process proceeds to STEP 65.

In STEP64, control unit 53 drives all the low-side element IGBTs (Q2, Q4, Q6) to an off state (in other words, the duty ratio D is 0%). Accordingly, all IGBTQ1 to Q6 are in the off state, the braking control by the control unit 53 ends, and the control unit 53 proceeds to STEP7 to end the stopping control.

In STEP65, control unit 53 determines whether or not detected current value I is equal to 2 nd threshold value I₂The following. When the detected current value I is at the 2 nd threshold value I₂If so (STEP 65: YES), the process proceeds to STEP66AWhen the detected current value I is not at the 2 nd threshold value I₂In the following case, in other words, the 2 nd threshold value I is exceeded₂If (STEP 65: NO), the process proceeds to STEP 66B.

In STEP66A, the current value I is detected at the 2 nd threshold value I₂Therefore, the control unit 53 increases the duty ratio D by a predetermined ratio Δ D (β%). the Δ D for increase adjustment is preset in the control unit 53 together with Δ D for decrease adjustment described later, so as to be changeable based on the characteristics of the compression mechanism 3 and the motor 4, and the Δ D for increase adjustment may be identical to or different from the Δ D for decrease adjustment, and the control unit 53 drives all the low-side element IGBTs (Q2, Q4, and Q6) to the on state at the same time using the duty ratio D increased by Δ D from the previous value, whereby the braking force is also increased more than the previous time.

In STEP66B, although the 2 nd threshold value I is exceeded₂However, if STEP63 is NO, it is detected that the current value I is smaller than the 1 st threshold value I₁Condition (I)₂＜I＜I₁). Therefore, although it is slightly allowable to increase the braking force generated by the braking control, in the present embodiment, the control in the direction of reducing the braking force is performed in order to improve the reliability of preventing the IGBT from being broken. That is, control unit 53 decreases duty ratio D by a predetermined ratio Δ D (═ γ%). The control unit 53 drives all the low-side element IGBTs (Q2, Q4, Q6) to the on state at the same time using the duty ratio D reduced by Δ D from the last value. This also reduces the braking force more than before. The adjustment of the duty ratio D is performed for each predetermined period T, and the control unit 53 proceeds to STEP 67.

In STEP67, control unit 53 determines whether or not current duty D is 100%. When the current duty ratio D is 100% (STEP 67: yes), the control unit 53 enters a state in which the compression mechanism 3 is clamped at the maximum braking force (STEP 68). On the other hand, when the current duty D is less than 100% (STEP 67: no), the control unit 53 returns to STEP63, for example, and performs increase/decrease adjustment of the duty D based on the determination result in STEP65 (STEP66A, STEP66B) as long as it is not determined as yes in STEP63 and until the current duty D reaches 100% (STEP 67: yes).

In STEP68, the control unit 53 is in a state of clamping the compression mechanism 3 at the maximum braking force, and proceeds to STEP 69. In a state where the compression mechanism 3 is clamped at the maximum braking force, the rotation of the compression mechanism 3 is not necessarily stopped, and the inertial rotation may be performed in a state of positive rotation. The normal rotation refers to a rotation direction in a normal compressor operation state.

In STEP69, control unit 53 determines whether or not a predetermined time t02(t2 > t02) has elapsed from the time of starting the braking control (i.e., the time when all of the low-side device IGBTs (Q2, Q4, Q6) are turned on) at time t2 (braking time). When time t02 elapses at time t 2(STEP 69: yes), control unit 53 proceeds to STEP64, turns off all IGBTQ1 to Q6, and ends the braking control by control unit 53. Then, the control unit 53 proceeds to STEP7, and ends the stop control.

On the other hand, when the predetermined time t02 has not elapsed at the time t 2(STEP 69: no), the controller 53 proceeds to STEP 69A.

In STEP69A, control unit 53 determines whether or not detected current value I is in an increasing trend. When the detected current value I does not have a downward trend or slightly fluctuates (STEP 69A: no), the control unit 53 returns to STEP68 and maintains the clamping of the compression mechanism 3 at the maximum braking force.

On the other hand, when the detected current value I is in the rising trend (STEP 69A: yes), the control unit 53 resets the duty ratio D to return to the initial duty ratio D, for example₀And returns to STEP 63. If it is not determined as yes in STEP63, the control unit 53 executes the control of each STEP until time t2 reaches time t02(STEP 69: yes). The predetermined time t02 may be determined as appropriate according to the characteristics of the compression mechanism 3 and the motor 4.

Here, as described above, in STEP68, the compression mechanism 3 may be rotated by inertia so as to rotate in the positive direction even in a state where the compression mechanism 3 is clamped at the maximum braking force. Therefore, in order to reliably stop the inertial rotation of the compression mechanism 3, it is necessary to maintain this state for a predetermined time after the maximum braking force is reached. Therefore, the control unit 53 determines whether or not a sufficient braking time has elapsed from the time t2 when the braking control is started, by STEP69 (time t 02).

In the scroll-type compression mechanism 3, even when the rotation of the compression mechanism 3 that performs inertial rotation in a normal rotation mode is stopped, if the rotation of the orbiting scroll is stopped in a state where the rotational angle position of the orbiting scroll with respect to the fixed scroll is within the predetermined angular range, the communication between the high-pressure discharge pressure region and the low-pressure suction pressure region is maintained. As a result, the orbiting scroll, which is temporarily stopped, may start to rotate in the reverse direction due to a pressure difference between the discharge pressure region and the suction pressure region. In this regard, in the present embodiment, as described below, the reverse rotation can be detected by STEP 69A. That is, the positive rotation of the compression mechanism 3 is stopped until the time t2 from the start time of the braking control reaches the predetermined time t 02. In this state, the detected current value I is zero or substantially zero. Then, when the orbiting scroll of the compression mechanism 3 stops within the predetermined angular range in which the orbiting scroll is caused to perform reverse rotation by the pressure difference, for example, the orbiting scroll starts to perform reverse rotation. At this time, a regenerative current is generated by the reverse rotation, and as a result, the detected current value I starts to rise. STEP69A detects the rise of the detected current value I, thereby detecting the reverse rotation of the compression mechanism 3 (STEP 69A: yes). Then, control unit 53 restores duty ratio D to initial duty ratio D₀The braking control is executed for the reverse rotation to stop the reverse rotation quickly, thereby suppressing or preventing the generation of abnormal noise.

In other words, in the present embodiment, the control unit 53 ends the braking control when a state in which the increase in the detected current value is not detected (STEP 69A: no) continues from the start time of the braking control until a predetermined time t02 elapses (STEP 69: yes) after the braking force to the compression mechanism 3 by the braking control reaches a maximum (STEP 67: yes), and continues the braking control when the braking force to the compression mechanism by the braking control reaches a maximum (STEP 67: yes) and when the increase in the detected current value I is detected (STEP 69A: yes) before a predetermined time t02 elapses from the start time of the braking control (STEP 69: no).

In order to prevent the reverse rotation, for example, a sensor or the like for detecting a rotational position of a crank pin or the like for revolving the orbiting scroll is provided. Then, the control unit 53 may constantly monitor the rotational angular position of the orbiting scroll by the sensor or the like, and control the driving of the IGBT so that the maximum braking force is generated at the timing when the orbiting scroll is stopped in the angular range other than the predetermined angular range.

According to the electric compressor 1 of the present embodiment, in the braking control performed by the control unit 53, when the detected current value I is higher than the 1 st threshold value I₁In this case, the control unit 53 forcibly turns off all IGBTQ1 to Q6. Thus, for example, by applying only the 1 st threshold I₁By setting the value to be sufficiently lower than the value for IGBT breakage or the like, it is possible to reliably prevent IGBT breakage. In the braking control, the detected current value I is lower than the 1 st threshold value I₁In the case of (1), the drive modes of all the low-side element IGBTs (Q2, Q4, Q6) are adjusted by the control section 53 so that the detected current value I does not exceed the 1 st threshold value I₁Defined 2 nd threshold value I to be low₂. Therefore, since the braking control can be continued while reliably preventing the IGBT from being broken, the rotation of the compression mechanism 3 can be quickly stopped, and the reverse rotation of the compression mechanism 3 and the occurrence of abnormal noise caused by the reverse rotation can be quickly prevented or suppressed. Thus, the electric compressor 1 can be provided, which can reliably prevent the IGBT as the switching element from being damaged and can quickly stop the rotation of the compression mechanism 3.

In addition, in the present embodiment, the following configuration is adopted: 2 nd threshold value I₂The peak value of the starting current generated at the time of starting in the motor drive control is configured. Thus, the flow can be controlled by the brake controlThe value of the current passing through the motor drive circuit 52 is substantially suppressed in the vicinity of the starting current generated during the normal operation, and therefore, the IGBT can be more reliably prevented from being damaged.

In the present embodiment, the following structure is adopted: the adjustment of the drive mode of all the low-side device IGBTs (Q2, Q4, Q6) in the braking control is performed by changing the duty ratio D for each predetermined period T. Thereby, the adjustment of the driving mode can be easily performed.

In the present embodiment, the following structure is adopted: when the braking control is started, the control unit 53 controls the brake based on a predetermined initial duty ratio D₀All the low-side element IGBTs (Q2, Q4, Q6) are set to the on state. Thereby, by only setting the initial duty ratio D₀By setting the current to a value sufficiently lower than 100% (50% in the present embodiment), the value of the current flowing through the motor drive circuit 52 at the start of the braking control can be reliably suppressed to be lower than the 1 st threshold value I₁Sufficiently low so that breakage of the IGBT can be prevented more reliably.

In the present embodiment, the following structure is adopted: control unit 53 controls duty ratio from initial duty ratio D₀Starting the braking control based on a predetermined initial duty ratio D₀After all the low-side element IGBTs (Q2, Q4, Q6) are set to the on state in the time period of (1), the detection current value I is at the 2 nd threshold value I₂In the following case, the duty ratio D is increased by a predetermined ratio Δ D, and when the detected current value I is higher than the 2 nd threshold value I₂In the case of (3), the duty ratio D is reduced by a predetermined ratio portion Δ D. That is, in the case where it is sufficiently allowed to increase the braking force generated by the brake control (I ≦ I)₂) The braking force is increased, and in other cases, the braking force is reduced for safety. This can stop the rotation of the compression mechanism 3 more quickly, and can more reliably reduce the risk of breakage of the IGBT.

In the present embodiment, the braking control elements that are the predetermined switching elements to be adjusted in the drive mode are all low-side element IGBTs (Q2, Q4, Q6), but are not limited thereto, and may be all high-side element IGBTs (Q1, Q3, Q5).

In addition, in the present embodiment, the following structure is adopted: in STEP66B, control unit 53 detects that current value I is higher than 2 nd threshold value I₂In this case, the duty ratio D is decreased by a predetermined ratio Δ D, but is not limited thereto. The control unit 53 may be configured such that the control unit 53 sets the detected current value I to be higher than the 2 nd threshold value I in STEP66B₂At this time, the duty ratio D is maintained at the last value.

In the present embodiment, as the braking control, the controller 53 executes zero-vector energization for simultaneously and intermittently bringing all of the low-side element IGBTs (Q2, Q4, Q6) or all of the high-side element IGBTs (Q1, Q3, Q5) into an on state, but the present invention is not limited thereto. For example, control section 53 may intermittently drive (1) one of the high-side element IGBTs (Q1, Q3, Q5) and one of the low-side element IGBTs (Q2, Q4, Q6) into an on state, or (2) two of the high-side element IGBTs (Q1, Q3, Q5) and one of the low-side element IGBTs (Q2, Q4, Q6) into an on state, or (3) one of the high-side element IGBTs (Q1, Q3, Q5) and two of the low-side element IGBTs (Q2, Q4, Q6) into an on state. In these cases, the IGBT to be driven is determined so that the high-side device and the low-side device of the same phase are not in the on state at the same time. That is, for example, when one of the high-side element IGBTs (Q1, Q3, Q5) and one of the low-side element IGBTs (Q2, Q4, Q6) are intermittently driven to an on state, when Q1 is selected as the high-side element, Q4 or Q6 is selected as the low-side element.

While the embodiment of the present invention and the modification thereof have been described above, the present invention is not limited to the above embodiment and modification, and it goes without saying that further modifications and changes can be made based on the technical idea of the present invention.

Description of the reference symbols

1 … electric compressor, 3 … compression mechanism, 4 … motor, 52 … motor drive circuit, 53 … control part, 54 … current detection unit, B … DC power supply, D … duty ratio, D₀… initial duty cycle, H … high voltage line, L… ground line, I₁… threshold 1, I₂… threshold 2, IGBTs (Q1, Q3, Q5) … high side elements, IGBTs (Q2, Q4, Q6) … low side elements, Q1 to Q6 … switching elements (IGBTs).