JP2014046728A - Apparatus and method for diagnosis of fault in compressor of vehicle air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine fault due to sticking or the like of a compressor for an air conditioner.SOLUTION: When detecting the lowering of an engine speed at a predetermined lowering rate ΔNE1 or more during operation of a compressor for an air conditioner (t1), the operation of the compressor is stopped to avoid the occurrence of the engine stall, and the compressor is operated again after elapse of a first predetermined time ΔT1 (t2). When detecting an engine speed increase at a predetermined increase rate ΔNE2 or more (t4), following the lowering of the engine speed at the predetermined lowering rate ΔNE1 or more (t3), in a second predetermined time ΔT2 from the re-operation of the compressor, the fault due to the sticking of the compressor is determined. In this way, when the number of times determined as fault reaches a predetermined number of times (t7), the fault of the compressor is decided.

Description

  The present invention relates to a failure diagnosis of a compressor of an air conditioner (hereinafter referred to as “air conditioner”) mounted on a vehicle.

  In Patent Document 1, when a compressor of a vehicle air conditioner is operating, an increase in vehicle deceleration or a decrease in engine speed causes an engine stop unintended by the driver, so-called engine stall. As described above, a technique is described in which a determination threshold value is set according to the engine speed, and the operation of the compressor is temporarily stopped when the vehicle deceleration becomes equal to or higher than the determination threshold value.

  Further, in Patent Document 2, when a compressor for an air conditioner is started, liquid compression of the compressor is detected based on a reduction rate of the engine driving force or the engine rotation speed, and when the liquid compression is detected, the engine rotation speed rapidly decreases. The operation of the compressor is temporarily stopped to suppress this.

JP 2009-248799 A Japanese Patent No. 3318999

  However, in any of the above Patent Documents 1 and 2, when a predetermined period has elapsed since the operation of the compressor is stopped, it is considered that the overload state to the engine has ended and the compressor is restarted. It cannot cope with compressor failures such as sticking due to biting. In other words, even in the case of a compressor failure, the compressor is restarted after a predetermined period of time has elapsed since the compressor stopped, causing the engine to become overloaded, causing the engine speed to decrease repeatedly, causing discomfort, There is a risk of reaching.

  In addition, since the technology described in Patent Document 2 is intended to avoid liquid compression in the compressor immediately after the initial start-up from the non-operating state of the compressor, it detects the liquid compression of the compressor immediately after starting the compressor. Yes. However, a compressor failure due to sticking or the like usually occurs during the operation of the compressor. Therefore, in the configuration in which the diagnosis is performed only immediately after the first startup of the compressor as described in Patent Document 2, the failure due to the sticking or the like is detected. It cannot be diagnosed accurately.

  Therefore, it is conceivable to detect / determine a failure due to sticking of the compressor, etc., and to prohibit the restart of the compressor until the compressor is replaced or repaired at a maintenance shop or the like. However, if it is determined that there is no failure, the air conditioner will be deactivated until it is brought into the maintenance shop, which will cause significant inconvenience and dissatisfaction for the vehicle passengers. Fault diagnosis is desired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to accurately determine a failure due to, for example, the fixing of a compressor of an air conditioner.

  Therefore, in the present invention, when the engine speed is detected, and when the first engine speed reduction state is detected during the operation of the compressor of the air conditioner, the operation of the compressor is first stopped. After the first predetermined time has elapsed, the compressor is restarted. When the second engine speed reduction state is detected within the second predetermined time from the restart of the compressor, it is determined that the compressor has failed.

  If the first engine speed reduction state is detected during the operation of the air conditioner compressor, if the failure is determined immediately, the engine speed reduction state caused by vehicle deceleration, transmission shift operation, etc. Even in this case, there is a possibility that it is erroneously determined as a failure. Therefore, in the present invention, when the first engine speed reduction state is detected during the operation of the air conditioner compressor, the failure diagnosis is not performed immediately, but first, the engine speed reduction state is resolved to reduce the engine stall. In order to avoid the occurrence, the operation of the compressor is stopped, and the compressor is restarted after a lapse of the first predetermined time from the stop of the operation of the compressor.

  Then, the compressor failure is determined when a decrease in the second engine speed is detected within the second predetermined time from the restart of the compressor. As described above, since the failure of the compressor is determined only when a decrease in the engine speed is detected again immediately after the compressor is restarted, the possibility of erroneous determination is low and the accuracy is high. A compressor failure can be determined.

  Further, as described above, immediately after the initial start-up from the non-operating state of the compressor, the engine speed may be reduced due to liquid compression in the compressor. Since the failure determination is performed after the operation is stopped and restarted, there is no possibility that the engine speed reduction state due to the liquid compression immediately after the start of the compressor is erroneously determined as a failure.

  According to the present invention, it is possible to accurately determine a failure due to compressor sticking or the like while suppressing or avoiding the occurrence of engine stall due to a decrease in engine speed.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows simply the failure diagnosis apparatus of the compressor of the vehicle air conditioner which concerns on one Example of this invention. The flowchart which shows the flow of the failure diagnosis process of the compressor of the said Example. The timing chart which shows the behavior at the time of applying the failure diagnosis process of the compressor of the said Example.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically illustrates a compressor failure diagnosis apparatus for a vehicle air conditioner according to an embodiment of the present invention. As is well known, a vehicle air conditioner mounted on a vehicle performs heating, cooling, and dehumidification of a vehicle interior, and is driven to rotate by an engine 11 to suck, compress, and discharge a refrigerant, and to perform a refrigerant cycle. A compressor 12 that circulates the refrigerant therein, a condenser 13 that cools and liquefies the high-temperature and high-pressure refrigerant discharged from the compressor 12, and evaporates the refrigerant expanded under reduced pressure by an expansion valve (not shown). And an evaporator 14 for cooling the air by the heat of vaporization.

  The rotational power of the engine 11 is transmitted to the compressor 12 via a belt 15 and pulleys 16 and 17 (or chains and sprockets), and an electromagnetic clutch 18 is interposed in the power transmission path. The electromagnetic clutch 18 is driven and controlled by a command signal from the engine control unit 20, and the compressor 12 is activated when the electromagnetic clutch 18 is engaged, and the compressor 12 is stopped when the electromagnetic clutch 18 is released.

  The engine control unit 20 stores and executes various engine controls such as idle speed control and fuel injection control, as well as control processing such as failure diagnosis of the compressor 12 described later. The engine control unit 20 receives air conditioner information such as ON / OFF of the air conditioner and a set temperature by an air conditioner operating device 21 operated by a driver, and is detected by a crank angle sensor 22 (engine speed detection means). In addition to the engine speed, engine information such as the accelerator opening is input from the engine 11 side. Further, vehicle information such as the vehicle speed is input to the engine control unit 20, and a gear position, a lock-up signal (L / U), or the like is shifted from a transmission control unit (not shown) for driving and controlling the automatic transmission. Machine (T / M) information is input.

  FIG. 2 is a flowchart showing the flow of a failure diagnosis process due to the fixing of the compressor 12 for an air conditioner according to the present embodiment. This routine is repeatedly executed by the engine control unit 20 every predetermined period (for example, every 10 ms). The

  In step S11, it is determined whether or not the air conditioner compressor 12 is operating, that is, whether or not the electromagnetic clutch 18 is engaged. If the compressor 12 is operating, the process proceeds to step S12, and if the compressor 12 is not operating, the process proceeds to step S17 described later.

  In step S12, it is determined whether the engine speed change speed ΔNE is equal to or lower than a predetermined reduction speed ΔNE1 (negative value). Here, the change speed ΔNE is defined to be a positive value when the engine speed is increased / accelerated in this embodiment. Therefore, the change speed ΔNE when the engine speed is decreased / decelerated The predetermined decrease rate ΔNE1 is a negative value. Accordingly, in this step S12, it is determined whether or not the decrease speed | ΔNE | (the absolute value of the change speed ΔNE) of the engine speed is equal to or greater than the predetermined decrease speed | ΔNE1 | (the absolute value of ΔNE1). If the engine speed decrease speed | ΔNE | is equal to or greater than the predetermined decrease speed | ΔNE1 |, the process proceeds to step S13. If the engine speed decrease speed | ΔNE | is less than the predetermined decrease speed | ΔNE1 | Proceed to S17.

  In step S13, the timer 1 that measures the elapsed time from the start time of the operation stop of the compressor 12 (see times t1, t3, and t6 in FIG. 3) is started. The timer 1 and the timer 2 described later are built in the engine control unit 20.

  In step S14, it is determined whether or not the value of the timer 2 that measures the elapsed time from the restart time (see times t2 and t5 in FIG. 3) of the compressor 12 described later is equal to or less than the second predetermined time ΔT2. The second predetermined time ΔT2 is a value set in advance by a test or adaptation, and includes a period in which the engine speed temporarily fluctuates greatly when the compressor 12 is restarted when the compressor 12 is fixed. The time is set to be at least shorter than a first predetermined time ΔT1 described later. If the elapsed time from the re-operation of the compressor 12 is within the second predetermined time ΔT2, the process proceeds to step S15, and if it exceeds the second predetermined time ΔT2, the process proceeds to step S17.

  In step S15, it is determined whether or not the rotation speed return flag immediately after the restart is “1”. As will be described later, the engine speed return flag immediately after the restart is set to “1” when the engine speed increase speed ΔNE is equal to or higher than a predetermined increase speed ΔNE2 (see steps S18 and S21). It is reset to “0”. If the rotation speed return flag immediately after the restart is “1”, the process proceeds to step S30, the value of a sticking determination counter described later is cleared to “0”, and the process proceeds to step S22. If the engine speed return flag immediately after the restart is not “1”, the process proceeds to step S16.

  In step S16, the engine speed reduction flag immediately after re-operation is set to “1”. The engine speed reduction flag immediately after the restart is set to “1” in step S16 when it is determined in step S12 that the engine speed reduction speed | ΔNE | is equal to or greater than the predetermined reduction speed | ΔNE1 | This is reset to “0” in step S31 described later.

  In step S17, as in step S14, it is determined whether the value of timer 2 is equal to or shorter than the second predetermined time ΔT2, that is, whether the elapsed time from the start of re-operation of the compressor 12 is within the second predetermined time ΔT2. To do. If it is within the second predetermined time ΔT2, the process proceeds to step S18. If the second predetermined time ΔT2 is exceeded, the process proceeds to step S31, where both the rotation speed decrease flag immediately after reactivation and the rotation speed return flag immediately after reactivation are reset to “0”, and the determination of failure due to sticking is interrupted / prohibited. To do.

  In step S18, it is determined whether the engine speed changing speed (rise speed) ΔNE is equal to or higher than a predetermined increase speed ΔNE2. If the engine speed increase speed ΔNE is greater than or equal to the predetermined increase speed ΔNE2, the process proceeds to step S19, and if it is less than the predetermined increase speed ΔNE2, the process proceeds to step S22 described later.

  In step S <b> 19, it is determined whether or not the above-described immediately after reactivation rotational speed reduction flag is “1”. If the rotation speed decrease flag immediately after reactivation is “1”, the process proceeds to step S20. If the rotation speed decrease flag immediately after reactivation is not “1”, the process proceeds to step S22 described later.

  In step S20, "1" is added (incremented) to the value of the sticking determination counter, and the counter value is updated / integrated.

  In step S21, in response to the determination that the engine speed increase speed ΔNE is greater than or equal to the predetermined increase speed ΔNE2 in step S18, the engine speed return flag immediately after reactivation indicates this determination content (ΔNE ≧ ΔNE2). Set to “1”.

  In step S22, it is determined whether the value of the sticking determination counter is equal to or greater than a predetermined number of times (in this embodiment, twice). If the value of the sticking determination counter is equal to or greater than the predetermined number, the process proceeds to step S23, and if the value of the sticking determination counter is not equal to or greater than the predetermined number, the process proceeds to step S24.

  In step S23, it is determined that the compressor 12 has failed due to sticking, and the compressor sticking confirmation flag (see FIG. 3) is set to “1” representing the determination result (sticking confirmation). The value of the sticking confirmation flag is stored in a storage device in the engine control unit 20, and is held without being cleared even after the vehicle is stopped by turning off the ignition switch.

  In step S24, it is determined whether or not fixing is confirmed in step S23, that is, whether or not the value of the compressor fixing determination flag is “1”. If the fixing is confirmed, the process proceeds to step S29 described later, and if the fixing is not confirmed, the process proceeds to step S25.

  In step S25, it is determined whether the value of the timer 1 for measuring the operation stop time of the compressor 12 is equal to or less than the first predetermined time ΔT1. The first predetermined time ΔT1 is a value set in advance by a test or adaptation, and the compressor 12 is restarted by returning (increasing) the engine speed after the operation of the compressor 12 is stopped due to a decrease in the engine speed. Corresponds to the time from the stoppage necessary to reliably avoid the engine stall. If it is within the first predetermined time ΔT1, the process proceeds to step S26, and if it exceeds the first predetermined time ΔT1, the process proceeds to step S32 described later.

  In step S26, the engine speed may decrease due to the engine state or the vehicle state, that is, the engine speed may decrease due to a factor other than the failure of the compressor 12. It is determined whether or not. The state in which the engine speed is reduced depending on the engine state or the vehicle state as described above includes, for example, rapid deceleration of the vehicle by the driver's accelerator operation or brake operation, switching of the automatic transmission from the N range to the D range, automatic shifting The machine upshift, accelerator pedal ON / OFF operation, lock-up clutch operation, etc. If the engine rotational speed is reduced due to the engine state or the vehicle state, the process proceeds to step S27. Otherwise, the process proceeds to step S28.

  In step S27, the first predetermined time ΔT1 for determining the operation stop time of the compressor 12 is corrected to the increase side, and this first predetermined time ΔT1, that is, the time from the operation stop of the compressor 12 to the re-operation is extended.

  In step S28, the engine speed is increased by a predetermined amount, and this routine is terminated. For example, the idling target rotation speed is increased by a predetermined amount during idling, and the engine rotation speed is increased by a predetermined amount by downshifting the automatic transmission when the vehicle is running.

  In step S29, the electromagnetic clutch 18 is opened, and the operation of the air conditioner compressor 12 is stopped.

  In step S32, it is determined whether the value of the timer 1 for measuring the operation stop time of the compressor 12 is equal to or longer than the first predetermined time ΔT1. When the first predetermined time ΔT1 is reached, the process proceeds to step S33, and the timer 2 that measures the elapsed time from the start of re-operation of the compressor 12 (see times t2 and t5 in FIG. 3) is started.

  In step S34, the electromagnetic clutch 18 is engaged and the operation of the compressor 12 of the air conditioner is resumed.

  FIG. 3 is a timing chart showing the behavior when the failure diagnosis of this embodiment is applied. With reference to this FIG. 3, the characteristic structure and effect of a present Example are demonstrated.

  During the period from time t0 to time t1, the compressor 12 of the air conditioner is in operation, and idle speed control is performed in which the engine speed is feedback-controlled toward the target idle speed tNE. In the idle speed control at this time, since the compressor 12 is in operation, the target idle speed tNE is set to a high idle state that is higher by a predetermined amount (for example, about 100 rpm) than the normal value. If the compressor 12 is fixed by foreign matter biting during such compressor operation, the engine speed temporarily decreases temporarily, and accordingly, the engine speed decrease speed (absolute value of the change speed ΔNE) increases. Increases temporarily.

  At time t1, when it is detected that the decrease speed | ΔNE | of the engine speed is equal to or greater than the predetermined decrease speed | ΔNE1 | (step S12), it is determined that the first engine speed is decreasing. The operation of the compressor 12 is stopped (step S29), the engine speed is intentionally increased (step S28), and the operation is stopped so as to avoid the occurrence of engine stall due to an excessive decrease in the engine speed. The timer 1 that measures time is started to be measured (step S13). In the example of FIG. 3, since the engine is in the idling state, the target idle speed tNE is increased by a predetermined amount ΔtNE (for example, about 300 rpm) in step S28 in order to increase the engine speed by a predetermined amount. At this time, the change speed (rising speed) of the target idle speed tNE is limited so as not to cause a sudden torque fluctuation or a rotational fluctuation due to a sudden increase in the engine speed, as shown in FIG. The idle speed tNE is gradually increased.

  Thus, by stopping the operation of the compressor 12 at the time t1, the engine speed that has been greatly reduced temporarily due to the fixing of the compressor 12 rapidly increases and returns to the vicinity of the original engine speed. Therefore, as shown in FIG. 3, immediately before the time t1, the speed of decrease in the engine speed temporarily increases due to the fixing of the compressor 12, while immediately after the time t1, the operation of the compressor 12 is stopped and the engine speed is reduced. The increase speed of the engine speed is temporarily increased by the increase control.

  Thereafter, when the first predetermined time ΔT1 elapses from the start time t1 of the operation stop (time t2), the influence of the rotation fluctuation at the time t1 is eliminated, and the sufficient rotation speed can be increased and the compressor 12 is not generated. Is restarted, the compressor 12 is restarted, and the timer 2 for measuring the elapsed time from the restart time t2 is started (steps S32 to S34).

  When it is detected at time t3 immediately after the re-operation that the engine speed decrease speed | ΔNE | is equal to or greater than the predetermined decrease speed | ΔNE1 |, the engine speed decrease is performed in the same manner as the process at time t1. The operation of the compressor 12 is stopped so as to avoid the occurrence of engine stall (step S29).

  Then, before the elapsed time measured by the timer 2 reaches the second predetermined time ΔT2 (step S17), a state in which the engine rotational speed is decreased at a predetermined speed | ΔNE1 | or more is detected. (Step S12) After that, when an increase state of the engine speed at a predetermined increase speed ΔNE2 or more is detected (Step S18), it is determined that the compressor 12 is in a failure due to the fixation at time t4 in FIG. “1” is added to the counter value (number of determinations) (step S20).

  Thereafter, in the same manner as the processing at the times t2 to t4 described above, the re-operation (time t5), the operation stop (time t6), and the sticking determination (time t7) of the compressor 12 are performed, and the sticking determination number is a predetermined number of times. At time t7 that has reached (in this example, twice), it is determined that the compressor 12 has failed due to sticking (steps S22 and S23), and the compressor sticking confirmation flag indicates “1” indicating that sticking has been confirmed. Set to. When the fixing is thus determined, the subsequent operation of the compressor 12 for the air conditioner is prohibited regardless of the vehicle stop / start operation by the ignition switch or the air conditioner operation by the air conditioner operating device 21.

  [1] As described above, in this embodiment, at the time t1 when the engine speed decrease (first engine speed decrease state) equal to or higher than the first predetermined decrease speed | ΔNE1 | is detected during the operation of the compressor 12. First, the operation of the compressor 12 is stopped so as to avoid the occurrence of the engine stall by eliminating the engine rotational speed reduction state without performing the failure diagnosis due to the sticking. After the lapse of time ΔT1, the compressor 12 is restarted.

  Then, only when the engine speed reduction state (second engine speed reduction state) is detected again within the second predetermined time ΔT2 from the re-operation of the compressor 12, the failure due to the fixing of the compressor 12 is detected. Make a decision. In other words, the failure diagnosis is performed only after the compressor 12 is in operation, the operation is stopped due to a decrease in the engine speed, and the operation is restarted. Specifically, the engine speed decreases again (second state) immediately after the restart. The failure of the compressor 12 is determined only when a decrease in the engine speed is detected. Therefore, it is unlikely that a failure due to the fixing of the compressor 12 is erroneously determined when the engine speed decreases due to vehicle deceleration, a gear shifting operation, or the like, and the failure due to the fixing of the compressor 12 is accurately determined. It becomes possible to do.

  Further, as described above, immediately after the compressor 12 is started for the first time, the engine speed may decrease due to liquid compression in the compressor. Since the failure diagnosis is performed after the stop-re-operation, there is no possibility that the reduced state of the engine speed due to the liquid compression immediately after the start of the compressor 12 is erroneously determined as a failure.

  In the above embodiment, for the sake of simplification of control, it is determined for the first time that the engine speed has been reduced during the operation of the compressor (first engine speed reduction state) and the second time after the compressor is restarted. The subsequent determination of the engine speed reduction state (second engine speed reduction state) is performed as the same determination processing in step S12, but both determination processing is performed in order to improve the determination accuracy. The contents of may be different.

  [2] In the above embodiment, as a process for detecting a decrease in engine speed, the engine speed is decreased in step 12 of FIG. 2 mainly for the purpose of simplifying the control and reducing the calculation load / memory usage. When the speed | ΔNE | is equal to or greater than the predetermined decrease speed | ΔNE1 |, it is detected and determined that the engine speed is decreasing.

  [3] However, if the engine speed reduction state is determined based only on the engine speed reduction speed, the upshift of the automatic transmission and the driver's brake operation are performed, for example, during operation in the high speed range. This is not a decrease in the engine speed due to the failure of the compressor 12 but a decrease in the engine speed that does not cause an engine stall as in the case where the decrease speed of the engine speed temporarily increases due to the like. Nevertheless, it is determined that the engine rotational speed is decreasing, and the compressor 12 may be unnecessarily stopped.

  Therefore, in order to improve the detection accuracy of the engine speed reduction state, for example, in step S12 of FIG. 2, the engine speed reduction speed | ΔNE | is equal to or greater than the predetermined reduction speed | ΔNE1 | When the number is equal to or less than a predetermined value, it may be configured to detect and determine that the engine speed is in a reduced state. The predetermined value of the engine speed in this case is set to a value (for example, about 1000 rpm) higher than the target idle speed in the high idle state.

  [4] Alternatively, more simply, in step S12 of FIG. 2, it may be configured to determine whether or not the engine speed is equal to or less than a predetermined value. In this case, the predetermined value of the engine speed is set to a value lower than the target idle speed (for example, about 300 rpm).

  [5] Further, according to the configuration in which the electromagnetic clutch 18 is interposed in the power transmission path between the engine 11 and the compressor 12 as in the above embodiment, the operation of the compressor 12 is performed by switching between opening and closing of the electromagnetic clutch 18. Switching between stop and re-operation can be easily performed with good responsiveness.

  [6] In the above embodiment, the compressor 12 is determined to be faulty when the number of times determined to be a failure is equal to or greater than the predetermined number of times, instead of determining the failure by a single failure determination of the compressor 12 ( Steps S22 and S23). In this way, by determining a failure through a plurality of failure determinations, it is possible to more reliably prevent erroneous determination due to an accidental decrease in engine speed and the like, and to further improve diagnosis accuracy.

  [7] Further, when the failure of the compressor 12 is confirmed in this way, the determination result is stored using, for example, a sticking confirmation flag (see FIG. 3), and subsequent restart of the compressor 12 is prohibited. Yes. Therefore, there is no possibility that the compressor 12 will be erroneously operated despite the malfunction of the compressor 12, and the occurrence of engine stall due to the inadvertent operation of the compressor 12 can be reliably avoided.

  It should be noted that the stored failure determination result (the value of the sticking confirmation flag) can be canceled only by using a predetermined procedure or tool that can only be performed at a maintenance shop or the like. The reason for this is that if the operation can be canceled by an operation or procedure that can be easily performed by the driver, the air conditioner can be reactivated while the compressor 12 is broken, and an engine stall may occur.

  [8] When the engine speed rapidly decreases due to the fixing of the compressor 12, the engine speed is rapidly increased (returned) by stopping the operation of the compressor 12 by releasing the electromagnetic clutch 18. On the other hand, when the engine speed decreases rapidly due to factors other than the failure of the compressor 12, such as during upshifting or sudden deceleration, the operation of the compressor 12 is stopped as compared with the case of the failure of the compressor 12. The accompanying increase (return) of the engine speed becomes moderate.

  Therefore, in the above-described embodiment, when determining the failure after the restart, not only the engine speed decrease state exceeding the predetermined decrease speed | ΔNE1 | is detected within the second predetermined time ΔT2 from the restart of the compressor. It is determined that the compressor 12 has failed only when an engine speed increase state equal to or greater than the predetermined increase speed | ΔNE2 | is detected. As described above, by determining that a failure occurs only in a pattern in which the engine speed increase state continues in the second predetermined time ΔT2 following the engine speed decrease state, an upshift, rapid deceleration, etc. It is possible to more reliably suppress and prevent erroneous determination as a failure when the engine speed rapidly decreases due to factors other than the failure of the compressor 12, and further improve the diagnostic accuracy.

  [9] When the operation of the compressor is stopped due to a decrease in the engine speed due to the stuck compressor, if the engine speed decreases due to the engine / vehicle state during the operation stop, the operation is stopped. When the compressor 12 is restarted after the elapse of one predetermined time ΔT1, the decrease in the rotation speed due to the fixation of the compressor 12 overlaps, so that the engine rotation speed may be greatly decreased and engine stall may occur.

  Further, when the compressor 12 is not operated due to an accidental decrease in the engine speed due to an upshift or the like other than the fixing of the compressor 12, if the engine speed decreases due to the engine / vehicle state during the operation stop, When the compressor 12 is restarted after the elapse of the first predetermined time ΔT1 from the stoppage of operation, the engine speed becomes relatively low due to the accidental decrease in the engine speed even though the compressor 12 is not fixed. Since it is in a low state, there is a possibility that this reduced state of the engine speed is erroneously determined to be due to the stuck compressor.

  Therefore, in the above-described embodiment, a state in which the engine speed is accidentally reduced (due to the engine operating state or the vehicle operating state, such as during an upshift or vehicle deceleration) within the first predetermined time ΔT1 from the stop of the operation of the compressor 12 ( If the third engine speed reduction state is detected, the process proceeds from step S26 to step S27, and the first predetermined time ΔT1 is extended.

  As described above, when an accidental decrease in the engine speed occurs while the operation of the compressor 12 is stopped, the first predetermined time ΔT1 is extended to extend the operation stop time, thereby restoring the engine speed. A (rise) time can be secured, and a decrease in the engine speed when the compressor 12 is restarted after the first predetermined time ΔT1 has elapsed can be suppressed / relieved. As a result, it is possible to suppress the occurrence of engine stall when the compressor 12 is restarted, and to suppress / avoid erroneous determination.

  [10] Alternatively, an accidental engine speed reduction state (third engine speed reduction state) such as upshift or vehicle deceleration is detected within the first predetermined time ΔT1 after the compressor 12 is stopped. In such a case, it may be configured to prohibit the failure determination of the compressor 12 so as to reliably avoid the occurrence of an erroneous determination.

  [11] When misfire occurs due to an abnormality in a spark plug or an injector, a decrease in engine speed continuously occurs within a short time. Therefore, in this embodiment, when such a state is detected, the failure determination is interrupted / prohibited so as to avoid erroneous determination. In other words, when a state where the engine speed is reduced a plurality of times is detected, it is determined that a misfire has occurred due to the abnormality of the spark plug or the injector described above, and failure determination is prohibited. More specifically, if the engine speed return flag immediately after restart is determined to be “1” in step S12 in FIG. 2, the engine rotates immediately after restart in step S16 in the routine executed before this routine. The number decrease flag is set to “1”. From this, it is determined that a plurality of engine speed decreases are being experienced, and the process proceeds to step S30 to clear the sticking determination counter. The failure judgment is interrupted / prohibited.

  [12] If the operation of the compressor 12 is stopped by detecting a decrease in the engine speed in step S29 in FIG. 2, the engine speed is set in step S28 except when fixing is confirmed (S24). Increased by a predetermined amount. For example, when the vehicle is idling as in the above embodiment, the target idle speed is increased by a predetermined amount ΔtNE, and when the vehicle is running, the engine speed due to the downshift of the automatic transmission is increased by a predetermined amount. . Thus, by increasing the engine speed in advance before restarting the compressor 12, the occurrence of engine stall when the compressor 12 is restarted can be more reliably suppressed and avoided.

DESCRIPTION OF SYMBOLS 11 ... Engine 12 ... Compressor 18 ... Electromagnetic clutch 20 ... Engine control unit 22 ... Crank angle sensor (engine speed detection means)

Claims (13)

An engine speed detecting means for detecting the engine speed;
An operation stopping means for stopping the operation of the compressor when detecting a decrease in the first engine speed during operation of the compressor of the air conditioner;
Reactivation means for reactivating the compressor after a lapse of a first predetermined time from the operation stop of the compressor;
A failure determination means for determining a failure of the compressor when a decrease in the second engine speed is detected within a second predetermined time from the restart of the compressor;
A fault diagnosis apparatus for a compressor of an air conditioner for a vehicle, comprising:   2. The failure diagnosis device for a compressor of a vehicle air conditioner according to claim 1, wherein the first and second engine speed reduction states are states where the engine speed reduction speed is equal to or higher than a predetermined reduction speed. .   The reduced state of the first and second engine speeds is a state in which the speed of reduction of the engine speed is equal to or higher than a predetermined speed and the engine speed is equal to or lower than the predetermined speed. The failure diagnosis device for a compressor of a vehicle air conditioner according to 1.   2. The failure diagnosis device for a compressor of a vehicle air conditioner according to claim 1, wherein the reduced state of the first and second engine rotational speeds is a state where the engine rotational speed is equal to or lower than a predetermined rotational speed. An electromagnetic clutch is provided in a power transmission path between the engine and the compressor driven by the engine,
The compressor for a vehicle air conditioner according to any one of claims 1 to 4, wherein the operation stop means opens the electromagnetic clutch, and the reactivation means fastens the electromagnetic clutch. Fault diagnosis device.   6. The apparatus according to claim 1, further comprising a failure determination unit that determines a failure of the compressor when the number of times that the compressor is determined to be failed by the failure determination unit is a predetermined number of times or more. Failure diagnosis device for compressors for vehicle air conditioners.   7. The apparatus for diagnosing a failure of a compressor of a vehicle air conditioner according to claim 6, wherein when the failure of the compressor is determined by the failure determination means, the subsequent operation of the compressor is prohibited.   The failure determination means detects the second engine rotational speed decrease state and the subsequent engine rotational speed increase state within the second predetermined time from the restart of the compressor. The failure diagnosis device for a compressor of a vehicle air conditioner according to any one of claims 1 to 7, wherein it is determined that the compressor has failed.   The first predetermined time is extended when a condition that can cause the engine speed to decrease due to the state of the engine or the vehicle is detected within the first predetermined time after the compressor is stopped by the operation stop means. The failure diagnosis device for a compressor of a vehicle air conditioner according to any one of claims 1 to 8.   The failure of the compressor by the failure determination means is detected when a condition that can cause the engine speed to decrease due to the state of the engine or vehicle is detected within the first predetermined time from the stop of operation of the compressor by the operation stop means. 9. The failure diagnosis device for a compressor of a vehicle air conditioner according to claim 1, wherein the determination is prohibited.   The failure determination of the compressor by the failure determination means is prohibited when a plurality of engine speed reductions are detected within a second predetermined time from the restart of the compressor. 10. A failure diagnosis apparatus for a compressor of an air conditioner for a vehicle according to any one of 10 above.   12. The failure diagnosis apparatus for a compressor of a vehicle air conditioner according to claim 1, wherein when the operation of the compressor is stopped by the operation stop means, the engine speed is increased by a predetermined amount. Detects the engine speed,
When the first engine speed reduction state is detected during the operation of the compressor of the air conditioner, the operation of the compressor is stopped,
After the first predetermined time has elapsed from the stop of the operation of the compressor, the compressor is restarted,
A failure of the compressor is determined when a decrease in the second engine speed is detected within a second predetermined time from the restart of the compressor;
A failure diagnosis method for a compressor of a vehicle air conditioner.

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