JPS6358723B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to an air conditioner for an automobile, and more particularly to an air conditioner for an automobile equipped with a failure detection means suitable for detecting a failure of a temperature control door. [Background of the Invention] It is generally known that conventional air conditioners for automobiles use failure detection indicators such as disconnections, short circuits, and motor locks of various sensors.
Further, it is disclosed in Japanese Patent Application Laid-Open No. 58-11111 that it is possible to determine whether the magnitude of an output signal from a control element for controlling a temperature-controlled door is within a set range or not, and to display a failure of the control element on a display device based on the result. It is known from the publication No.-141912. However, no method has been established to easily and reliably detect failures in temperature-controlled doors. [Object of the Invention] The present invention has been made in view of the above, and its object is to provide an automotive vehicle that can easily detect a failure of a temperature-controlled door and prevent false detection due to delayed response of the door. Our goal is to provide air conditioning equipment. [Summary of the Invention] A feature of the present invention is that the control device (microcomputer) that controls the temperature control door according to the difference between the vehicle interior temperature and the target set temperature has a target voltage that indicates the target position of the temperature control door and When the absolute value of the difference between the voltage given from the potentiometer linked to the temperature control door indicating the controlled position of the temperature control door is greater than a predetermined value, and this state continues for a predetermined time, the temperature control door is closed. The present invention is characterized in that it is provided with a failure detection means that determines that there is a failure and causes the failure display means to display the failure. [Embodiments of the Invention] The present invention will be described in detail below with reference to the embodiments shown in FIGS. 1 to 5 and 7 to 9, and FIGS. 6 and 10. FIG. 1 is an overall configuration diagram showing an embodiment of an air conditioner for an automobile according to the present invention. The automotive air conditioner of this embodiment sucks air from outside and inside the vehicle,
A heat exchange unit 1 that heats or cools and blows out air into the vehicle interior, a control unit 2 that electrically controls each device of this heat exchange unit 1, and a control unit 2 that controls the start/stop of this device and the desired set temperature. It is composed of an operation section 3 for inputting information, and sensors for inputting a vehicle interior temperature signal and an equipment status signal of the heat exchange section 1 to a control section 2. The heat exchange unit 1 includes a heat exchange unit case 10.
Outside air intake port 1 that sucks air from outside the vehicle into the interior of the vehicle
01 and a suction door 111 that controls the opening and closing of the inside air suction port 102 that sucks air inside the vehicle, and this suction door 111 is controlled to three positions by a two-stage action negative pressure actuator 112 and a return spring 113. . That is, each negative pressure working chamber of the negative pressure actuator 112 is connected to the solenoid valves 114 and 11.
5, the suction port door 111 is connected to a negative pressure source such as a negative pressure pump through a solenoid valve 114, 115.
When both of the solenoid valves 114 and 11 are not energized, the force of the return spring 113 closes the inside air suction port 102 to take in outside air, and the solenoid valves 114 and 11
When both 5 are energized, negative pressure actuator 1
The outside air suction port 101 is closed by the negative pressure supplied to both negative pressure working chambers 12, and the inside air is sucked. Also, the solenoid valve 114 is energized, and the solenoid valve 11
5 is not energized, the negative pressure actuator 11
Since the negative pressure acts only on one of the negative pressure working chambers, the suction port door 111 stops at the intermediate position in the above state, and both the outside air suction port 101 and the inside air suction port 102 are opened, and the inside and outside air intake is stopped. state. The heat exchanger unit case 100 is also provided with a blower 121 that sucks air through suction ports 101 and 102 and sends it to the heat exchanger described later. The air volume by the blower 121 is controlled by controlling the applied voltage supplied to the motor 123 by a driver 122 controlled by the control unit 2 . An evaporator 131 is provided downstream of the blower 121, and this evaporator 131 constitutes a compression refrigeration cycle with a compressor 132, a condenser (not shown), an expansion valve 133, etc., and cools the air passing through it. It has become a means. The compressor 132 is driven by the automobile engine via an electromagnetic clutch 132a, and its driving and non-driving are controlled by a control signal from the control unit 2. The compressor relay 132b energizes and de-energizes the electromagnetic clutch 132a. It is done by doing. A heater core 141 serving as a heating means is provided downstream of the evaporator 131.
1 circulates the engine cooling water (hot water) of the automobile, and heats the air passing through the heater core 141. A temperature control door 142 is provided for controlling the amount of heating by increasing or decreasing the amount of air passing through the heater core 141. The temperature control door 142 is rotated by a negative pressure actuator 145 connected to a negative pressure source via electromagnetic valves 143 and 144 and a return spring 146. Solenoid valve 14
When neither of the solenoid valves 143 and 144 are energized, the negative pressure actuating chamber of the negative pressure actuator 145 operates as the solenoid valve 143,
Since the temperature control door 142 is connected to the atmosphere through the return spring 144, no negative pressure acts on the temperature control door 142.
46 rotates in the direction in which θ shown in FIG. 1 decreases. In other words, the heater core 141
This will increase the amount of air passing through. When the solenoid valve 143 is energized and the solenoid valve 144 is not energized, the negative pressure working chamber of the negative pressure actuator 141 is connected to the negative pressure source via the solenoid valves 144 and 143, and negative pressure is applied. As a result, the temperature control door 14
2 rotates against the return spring 146 in a direction in which θ increases. That is, heater core 1
41 in a direction that reduces the amount of air passing through. A potentiometer 147 that operates in conjunction with the temperature control door 142 inputs a position signal corresponding to the position of the temperature control door 142 to the control unit 2 in the form of a voltage V _T (V _T increases as θ increases). ), the control unit 2 is
Although specific processing will be described later, if the difference ΔV _T between the target position and the detected position is larger than a predetermined value, it is determined that there is a failure. Although the details will be described later, the temperature control door 142 is feedback-controlled with the above configuration, and the amount of air passing through the heater core 141 is increased from zero (θ increases) to 100% (θ increases) of the blower air volume A sent by the blower 121. is controlled to zero). In addition, air that does not pass through the heater core 141 is
Passing through the bypass 103 provided in parallel to 41,
It mixes with the heated air that has passed through the heater core 141 and is blown into the vehicle interior. The air that has passed through the evaporator 131 and the heater core 141 or the bypass 103 enters the vehicle interior through the upper outlet 104 and the lower outlet 10.
5 or into the vehicle interior from the differential air outlet 106 to the windshield. A mode door 151 is provided to switch the air outlet into the vehicle interior, and this mode door 151 is connected to the air inlet door 11.
2-stage action negative pressure actuator 152 similar to 1
It is controlled to 3 positions by Negative pressure actuator 1
The two negative pressure working chambers 52 each have a solenoid valve 15.
When both the solenoid valves 153 and 154 are not energized, the return spring 155 closes the upper outlet 104 and air is blown out from the lower outlet 105. Ru. Furthermore, when both the solenoid valves 153 and 154 are energized, the negative pressure actuator 1
A negative pressure source is connected to both negative pressure working chambers 52, the mode door 151 closes the lower outlet 105, and air is blown out from the upper outlet 104. When the solenoid valve 153 is energized and the solenoid valve 154 is not energized, only one negative pressure working chamber of the negative pressure actuator 152 is connected to the negative pressure source.
An intermediate position in the above state, that is, the upper air outlet 10
4. Both lower air outlets 105 are open,
Air is blown out from both outlets 104 and 105, which is a so-called bi-level state. The differential air outlet 106 is opened and closed by a differential door 156. (It is common to configure the system so that a small amount of air is blown out even when the differential door 156 is closed.)
The differential door 156 is driven by a negative pressure actuator 158 connected to a negative pressure source via a solenoid valve 157 and a return spring 159. Solenoid valve 15
7 is energized, the negative pressure actuator 15
8, the differential door 156 opens against the return spring 159, and when the electromagnetic valve 157 is not energized, the differential door 156 is closed by the action of the return spring 159. Immediately downstream of the evaporator 131, the air temperature immediately after passing through the evaporator 131, that is, the discharge air temperature.
A discharge air temperature sensor 160 consisting of a thermistor or the like that detects T _C is provided to detect the discharge air temperature.
T _C is input to the control unit 2 in the form of voltage V _C. Further, a vehicle interior temperature sensor 170 is installed at an appropriate position in the vehicle interior, and inputs the vehicle interior temperature _TR to the control unit 2 in the form of a voltage _VR . By the way, the temperature sensor signal with the characteristics shown in Fig. 6
V _C , V _R , i.e. 4.5~0.5V, i.e. −17~
The temperature of 80° C. is converted into a digital quantity by an A/D conversion circuit 21 shown in FIG. 5 and inputted to a microcomputer 22. However, in the case of failure detection, on the low voltage side due to short circuits, etc., the necessary
A voltage corresponding to 80°C can be input, but if the high voltage side is due to a disconnection, etc., the voltage corresponding to -17°C will be insufficient, so the temperature should be set based on the voltage (4.95V) corresponding to -50°C. In order to compare the sensor signals, a comparison circuit 24 is provided as shown in FIG. 4 to detect a failure in the temperature sensors 160, 170. The control unit 2 includes sensors such as temperature sensors 160 and 170 and an A-D converter 21 that converts analog signals from the operation unit 3 into digital signals, a comparison circuit 24 for sensor failure detection, and an A-D converter 21.
and a microcomputer 22 that performs arithmetic processing using digital signals from the operating section 3, and an interface circuit 23 that controls each device in the heat exchange section 1 using output signals from the microcomputer 22. FIG. 2 is a functional block diagram of the microcomputer 22. The interface circuit 23 connects the solenoid valves 114 and 11 of the heat exchange section 1.
5,143,144,153,154,157,
It is composed of transistors 231 to 238 as switch elements that control the compressor relay 132b, and a DA converter 239 that supplies an analog voltage to the driver 122 that supplies power to the motor 123. The operation unit 3 includes an air conditioner switch (not shown) for starting and stopping this device, a temperature setting device 31 for setting a desired temperature in the vehicle interior, a dehumidification switch 32 for manually dehumidifying the interior of the vehicle, and a differential air outlet 106. It consists of a differential switch 33 that blows air out to the windshield, a malfunction indicator lamp 34, and the like. The desired temperature of the passenger compartment (target set temperature T _S ) is set by the temperature setting device 31.
is input to the control unit 2 as a voltage V _S , and the operation signals V _DEH ,
V _DEF is input to the control unit 2 in the form of voltage levels. Next, the operation of the automobile air conditioner configured as described above will be explained. 3 and 4 are flowcharts of the operation of the control section 2. FIG. The numbers in parentheses in FIGS. 3 and 4 are step numbers indicating the order of the flow. As shown in the figure, the operation of this device is as follows from step (201) in FIG.
~ (203) initialization, step (204) ~
(218) repeats an infinite number of times, and during the processing of this main routine shown in FIG. ) and an interrupt routine of steps (220) to (228). First, when this device is activated by the air conditioner switch, the I/O data of the microcomputer 22 of the control section 2 is set to the initial value determined in step (201), and the RAM of the microcomputer 22 is set in step (202). is cleared. next,
The voltage V T of the potentiometer 147 corresponding to the position (θ=0) of the temperature control door 142 is the voltage V _T of the A-D converter 2.
1, it is converted into a digital quantity [V _T ] and read as the initial value of the door reference position (203). Note that this door reference position signal is monitored and updated by the interrupt routine (224) (for details on setting and updating the temperature control door reference position, see Japanese Patent Application Laid-Open No. 1983-1999).
(described in Publication No. 84216). Next, move on to the main routine. A voltage V _S corresponding to the target set temperature T _S set by the operation unit 3,
Voltage V _R corresponding to cabin temperature T _R , discharge air temperature T _C
The voltage V _C corresponding to is converted into digital values [V _S ], [V _R ], and [V _C ] through the conversion circuit shown in FIG. 5 and the processing shown in FIG. (204). FIG. 7 is a detailed flowchart of step (204) in FIG. The voltage V _S corresponding to T _S is input (240-0), the discharge air temperature sensor 160 and the cabin temperature sensor 170 are selected (204-2), and the output voltage is converted into a digital quantity by the A-D converter 21. and input it to the microcomputer 22 (204-3). The microcomputer 22 determines whether the signal voltage has become low due to a short circuit, etc. (204-4), and if it is low, it is assumed that there is a short circuit, and the corresponding failure flag is stored in the memory of the microcomputer 22. Set (204-5).
Furthermore, when the target is the internal air temperature T _R , (204-6),
By raising and lowering the set temperature T _S , it is replaced with a voltage equivalent to room temperature so that it can be used as a manual air conditioner (204-7), and the discharge air temperature immediately after the evaporator 131 is changed.
At T _C , in order to prevent the evaporator 131 from freezing, it is replaced with a voltage corresponding to a low temperature (204-
8). When the signal voltage exceeds the upper limit that can be converted into a digital quantity (204-9), resistor 24
2,243 (see Figure 5) to determine whether it exceeds the reference voltage of 4.95V for failure detection (204-10), and if it exceeds it, it is considered as a failure such as a disconnection, A corresponding failure flag is set in the memory of the microcomputer 22 (204-11), and the process is moved to step (204-6) (204-12). Note that reading of the voltage V _T corresponding to the position of the temperature control door 142 is performed by a dyma interrupt, which will be described later. Next, returning to FIG. 3, [V _R ] and [V _C ] are converted into digital values [T _R ] and [T _C ] (205). [V _S ] is the target set temperature T _S using the first-order conversion formula.
Convert it to a digital value [T _S ] (206). Then, the deviation [ΔT] between the target set temperature [T _S ] and _{the cabin temperature [T R ] is} calculated (207). Next, failure detection for the cooler and heater functions is performed using the deviation [ΔT]. Heater function,
When the cooler function and the temperature control door 142 are functioning normally, the microcomputer 22 counts them using time interrupts, which will be described later.
Each failure detection counter provided in the memory of the main routine is cleared in step (208) of the failure diagnosis processing of the main routine. If the abnormal state continues and the counter is no longer cleared, when the counter reaches a predetermined value, it is assumed that the corresponding function has failed, and a corresponding failure flag is set in the memory in the microcomputer 22. FIG. 8 is a detailed flowchart of step (208) in FIG. First, it is determined whether the absolute value of the difference between the temperature control door target voltage and the actually detected voltage is below a predetermined value ΔQ _T (208-1), and if it is normal and below the predetermined value, the temperature control door will malfunction. Clear the detection counter (208-2). In addition, it is determined whether the difference between the target set temperature and the inside air temperature is less than a predetermined value ΔT (208-3), and when it is normal and less than the predetermined value, a counter for heater failure detection is cleared (208-4). ). Also, it is determined whether the control signal On the other hand, when it is in the cooler region (X<0), it is further determined whether the difference between the target set temperature and the inside air temperature is greater than or equal to a predetermined value ΔT' (208-6), and if it is normal than ΔT', a cooler failure is detected. Clear the counter for (208-7). In addition, in the step (208-9) of failure display processing,
When any failure detection flag is set in the memory of the microcomputer 22, the failure display lamp 34 of the operation section 3 is turned on to notify the driver. The above fault detection count is performed by the fault detection counter process (227) shown in FIG. 9, which is executed at a constant cycle.
Let's do it. The temperature control door failure detection counter is counted up (227-1), and when the temperature control door failure detection counter reaches a number corresponding to the elapse of a predetermined time (for example, 10 seconds) (227-2), the temperature control door failure detection is performed. A flag is set in the memory of the microcomputer 22 (227-3). Also, the heater failure detection counter is counted up (227-4), and when the heater failure detection counter reaches a number corresponding to the elapse of a predetermined time (for example, 20 minutes) (227-5), the heater failure detection flag is set. It is set in the memory of the microcomputer 22 (227-6). Also, the cooler failure detection counter is counted up (227-7), and the cooler failure detection counter is counted up for a predetermined period of time (for example, 20 minutes).
When the number corresponds to the elapsed time (227-8), a cooler failure detection flag is set in the memory of the microcomputer 22 (227-9). Furthermore, returning to Figure 3, next, [X] = k [ΔT]
+1/τ∫[ΔT]dt PI calculation is performed. first,
The integral term in the above equation is obtained by adding the temperature deviation [ΔT] every predetermined time specified by the timer processing (226) of the interrupt routine in FIG. 4 (209). Furthermore, the control signal [X] is obtained by adding k [ΔT] to this integral term (210). Note that k and τ in the above equation are constants determined by the control system (details of the above PI calculation process can be found in the patent application filed in 1983-
57836). Further, when a dehumidification operation is performed by the dehumidification switch 32, a temporary correction value [ΔX] is added as the final process in step (210), and the value is set as a corrected value. This dehumidification operation will be described later. The control signal [X] obtained in this way is an amount corresponding to the amount of heat required as the cabin heat load in the process of controlling the cabin temperature _TR to the target set temperature T _S , and in this example, > 0, τ > 0, so when [X] > 0, the heating power is increased, and the larger the [X] value is, the greater the heating power is, and when [X] < 0, the cooling power is [-X] means that the larger the value, the greater the cooling power required as the cabin heat load. The operation of this air conditioner based on the value of this control signal [X] will be explained with reference to FIG. 10. FIG. 10 is a diagram explaining the operation of the heat exchange section 1 in FIG.
The control signal [X] is plotted on the horizontal axis. First, the temperature control door target voltage [V _T0 ] for the control signal [X] is determined by calculation (211). This target voltage [V _T0 ] is a linear expression regarding [X],
[X] is

At [0], [V _T0 = [V _T1 ], and at a predetermined positive value of [X] [X ₃ ], [V _T0 ]
= [V _T2 ]. Here, [V _T1 ]
is the potentiometer 14 with the temperature control door 142 closing the passage to the heater core 141 (θ is maximum)
[V _T2 ] corresponds to the voltage caused by the potentiometer 147 when the path to the heater core 141 is completely open (θ=0). Next, in the interrupt processing routine, the voltage V _T from the potentiometer 147 is read as a position signal of the temperature control door 142, and converted to a digital value (T _T ) by the A-D converter 21 (222). The position of the temperature control door 142 is controlled by comparing the voltages [V _T0 ] and [V _T ] (223). That is, first, [ΔV _T ]=[V _T0 ] -
Find [V _T ] and find the predetermined value [ΔV _TP ]
>0, “1” at [ΔV _T ]≧[ΔV _TP ],
Control signal [T ₁ ] that becomes “0” when [ΔV _T ] < [ΔV _TP ]
and a control signal [T ₂ ] which becomes "1" when [-ΔV _TP ]≦[ΔV _T ]≦[ΔV _TP ] and becomes "0" in a range other than the above. Then, the control signals [T ₁ ] and [T ₂ ] are “1”
When , the switch elements 233 and 234 are turned on, the solenoid valves 143 and 144 are energized, and the state becomes "0".
Power is not applied when . With _the above operation, as described above, the temperature control door 14 _is
2 is rotated in the direction of increasing θ, and [ΔV _T ]<[-
ΔV _TP ], the temperature control door 142 is rotated in the direction in which θ decreases. Further, in the range of [-ΔV _TP ]≦[ΔV _TP ], the temperature control door 142 is in a stationary state, and the position θ of the temperature control door 142 at this time is determined by the control signal [X].
The position corresponds to the target voltage [V _T0 ] corresponding to . Next, returning to step (215) of the main routine, the target temperature [T _C0 ] of the discharge air temperature T _C is determined as follows. For a predetermined negative value of [X] [X ₂ ], if [X]≦[X ₂ ], [T _C0 ] is the lowest possible value [T _C1 ] just before the evaporator surface freezes (this example (2.5℃), and in the range of [X]≧[X ₂ ],
[X] = [X ₂ ] and [T _C1 ] [X] =

[0] is a predetermined value [T _C2 ] (25° C. in this embodiment), which is a value determined by a linear equation connecting two points. In addition, [X]=

Near [0], the cabin heat load is a region where neither heating power nor cooling power is required, and the outside air temperature T ₀ is close to the target set temperature T _S. In this region, there is almost no need to operate the cooling means, so [T _C2 ≒
Set [ _TS ]. In the next step (216), the target discharge air temperature [T _C0 ] and the discharge air temperature [T _C ] are compared, and the temperature difference [ΔT _C ] = [T _C0 ] - [T _C ] is calculated. Then, a compressor control signal [C] is generated based on the value of [ΔT _C ]. That is, [ΔT _C ]≧

At [0], [C] is “0”, [ΔT _C ]<

[0] and [C] are “1”
becomes. When the compressor control signal [C] is "1", the switch element 235 is turned on at step (218), and the compressor relay 132b is energized. Then, by turning on the compressor relay 132b, the magnetic clutch 132a is excited, the compressor 132 is operated, and the evaporator 131 is turned on.
The air passing through is cooled and the discharge air temperature T _C decreases. As the discharge air temperature T _C decreases, [ΔT _C ]≧

[0] becomes [C]=

It becomes [0]. Therefore, at the final step (218) of the main routine, the compressor 132 becomes inactive. In this way, by repeating the operation and non-operation of the compressor 132, the discharge air temperature T _C becomes
The temperature is maintained close to the target temperature [T _C0 ] determined by the control signal [X]. However, as mentioned above, [X]≧0
In the range of , the cabin heat load requires heating power, and if the target set temperature T _S > the cabin outside air temperature T ₀ , on the other hand,
T _C0 > T _C2 ≒ T _S , and the suction door 111
Since this draws air outside the vehicle interior, the temperature of the air sent to the evaporator 131 is close to the temperature outside the vehicle interior T ₀ . Therefore, even if the cooling means does not operate, [ΔT _C ]>0
Therefore, the compressor 132 does not operate. Then, [T _C ]≒[T ₀ ]. The blower air volume A is approximately proportional to the voltage V _F supplied to the motor 123. The voltage V _F supplied to this motor 123 is controlled as follows. first,
Find the target voltage [V _F ] corresponding to the control signal [X]. Also, for the predetermined negative value [X ₁ ] and positive value [X ₄ ] of [X], [X]≦
[X ₁ ], [X] ≧ [X ₄ ], the maximum value [V _F1 ] (12V in this example), the above negative value [X ₂ ], positive value [X ₃ ], the maximum value [V _F2] ] (4V in this embodiment). Then, in the range of [ _{X 1} ]≦[ _{X ]} ≦[ _{X 2} ], [ V _F ] is determined, and in the range of [X _{3 ]} ≦ [ _X ] ≦ [X ₄ ], _{the linear} Determine [V _F ] from the formula (217). The target value [V _F ] obtained above is converted into an analog voltage V _FS by the DA converter 239 of the interface circuit 23 in step (218), and the motor 123 is controlled by the driver 122 controlled by this voltage V _FS . The voltage V _F applied to the motor 123 is controlled to drive the motor 123 . Depending on the value of the control signal [X], below [X ₁ ],
V _F is maximum, that is, blower air volume A is maximum
A _MAX , and between [X ₁ ] and [X ₂ ], the blower air volume A decreases almost linearly from the maximum A _MAX to the minimum A _MIN , and between [X ₂ ] and [X ₃ ], the blower air volume A decreases to the minimum. A _MIN
Between [X ₃ ] and [X ₄ ], it increases linearly from the minimum A _MIN to the maximum A _MAX , and above [X ₄ ], it is continuously controlled to reach the maximum A _MAX . Ru. In addition to the above operations, the suction port door 111,
The mode door 151 is also controlled by the value of the control signal [X]. That is, [X]≦

[0] is “1”, [X]
≧

Control signal [I ₁ ] that becomes “0” at [0], [X]≦
A control signal [I ₂ ] is created that becomes "1" when [X 5 ] and " ₀ " when [X]≧[X ₅ ] (212). Note that [X ₅ ] is a negative value, such that [X ₁ ]<[X ₅ ]<[X ₂ ]. When the control signals [I ₁ ] and [I ₂ ] are "1", the switch elements 231 and 232 are activated in step (218).
turns on, energizes the solenoid valves 114 and 115, and becomes “0”.
At this time, the electromagnetic valves 114 and 115 are not energized. When the control signal [X] is [X]≦[X ₅ ],
As described above, [I ₁ ] and [I ₂ ] both become "1", the solenoid valves 114 and 115 are energized, and the suction port door 111 enters a state in which the actuator 112 sucks inside air. [X]≧

When [0], both [I ₁ ] and [I ₂ ] are "0", and the suction port door 111 is pulled by the return spring 113 to be in a state of sucking outside air. [X ₅ ]≦[X]≦

At [0], [I ₁ ] is “1” and [I ₂
]
is "0", the suction port door 111 is at an intermediate position, and is in a state of sucking air from inside and outside. Similarly, the mode door 151 is also controlled by the value of the control signal [X]. however,

[0]＜[X ₆ ]＜
[X ₆ ] and [X ₇ ], which are [X ₇ ] < [X ₃ ], are determined in advance. “1” when [X] < [X ₇ ], “0” when [X]≧[X ₇ ]
The control signal [O ₁ ] becomes “1” when [X] < [X ₆ ],
A control signal [O ₂ ] that becomes “0” when [X]≧[X ₆ ] is generated (213). Then, the mode door 151 is driven in step (218) as follows based on the values of the control signals [O ₁ ] and [O ₂ ]. When [X] < [X ₆ ], the control signals [O ₁ ] and [O ₂ ] are both "1", and the switch elements 236, 23
7 are both turned on, the solenoid valves 153 and 154 are energized, and the mode door 151 is closed to the actuator 15.
2 causes the air to blow upward. Further, when [X]>[X ₇ ], both [O ₁ ] and [O ₂ ] are "0", so the solenoid valves 153 and 154 are not energized, and the mode door 151 is connected to the return spring 1.
55, the air is in a downward blowing state. [X ₆ ]≦[X]≦[X ₇ ], [O ₁ ] is “1”,
Since [O ₂ ] is "0", the electromagnetic valve 153 is energized, but the electromagnetic valve 154 is not energized, so the mode door 151 is in an intermediate position, and is in a state of upward and downward blowing. According to the embodiment of the present invention described above, in addition to detecting failures such as short circuits and disconnections of the discharge air temperature sensor 160 and the passenger compartment temperature sensor 170, the target voltage indicating the target position of the temperature control door 142 is detected. If the absolute value of the difference from the voltage indicating the actual position is larger than a predetermined value, it is determined that the temperature control door 142 is malfunctioning and a malfunction is displayed, so that the malfunction can be detected early. The next failure can be prevented from occurring. [Effects of the Invention] As described above, according to the present invention, in addition to being able to easily detect a failure of a temperature-controlled door, since the element of time is included in the failure detection, false detection of the door due to delay in response is eliminated. This has the effect of preventing secondary failures from occurring.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of an automotive air conditioner according to the present invention, FIG. 2 is a functional block diagram showing an embodiment of the microcomputer shown in FIG. 1, and FIGS. 1 is an operation flowchart showing an example of the operation of the control section, FIG. 5 is a circuit diagram showing an example of the temperature sensor voltage detection section of FIG.
The figure is a characteristic diagram of the temperature sensor, Figure 7 is a flowchart showing details of step (204) in Figure 3, Figure 8 is a flowchart showing details of step (208) in Figure 3, and Figure 9 is a flowchart showing details of step (208) in Figure 3. is step (227) in Figure 4.
FIG. 10 is a flowchart showing details of the operation of the heat exchange section of FIG. 1. DESCRIPTION OF SYMBOLS 1...Heat exchange part, 2...Control part, 3...Operation part, 21...A-D converter, 22...Microcomputer, 23...Interface circuit, 2
4... Comparison circuit, 31... Temperature setting device, 34...
Failure indicator lamp, 100... Heat exchange unit case, 103... Bypass, 111... Suction port door, 121... Blower, 131... Evaporator,
141... Heater core, 142... Temperature control door, 1
47... Potentiometer, 151... Mode door, 160... Discharge air target sensor, 170...
Vehicle interior temperature sensor.

Claims (1)

[Claims] 1 Cooling means, heating means and cabin temperature sensor,
The electric signal from the outside air temperature sensor and the potentiometer linked to the temperature control door is taken in via an analog/digital converter to control the temperature control door according to the difference between the cabin temperature and the target set temperature. a control means for automatically controlling the vehicle interior temperature to the target temperature setting; failure determination means for determining the temperature control door to be in failure if the absolute value of the difference between the target opening signal of the means and the detected opening signal of the temperature control door exceeds a predetermined amount and continues for a predetermined time;
An air conditioner for an automobile, comprising a failure display means for indicating a failure based on an output signal of the determination means.