JPH0999730A - On vehicle air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect failure of one sensor by comparing mutual outputs of both sensors with each other in an on-vehicle air conditioner having an engine water temperature sensor and an outside air temperature sensor. SOLUTION: Whether or not three conditions under which detecting voltage VTW from an engine water temperature sensor falls within a voltage range when a sensor line of a sensor is disconnected and an outside air temperature sensor is normally operated and an engine water temperature TW calculated on the basis of the detecting voltage VTW and an outside air temperature calculated on the basis of detecting voltage VTA from an outside air temperature sensor satisfy an expression (TA>TW+x) are all satisfied is judged (steps S2 to S7). Whether or not a condition where these three condition are satisfied continues for time T is judged (a step 11) from a count value of a timer (t), and when this condition continues for the time T, it is judged that a sensor line of the sensor is disconnected, and fail-safe control such as an output value from the water temperature sensor is changed to a substitutive value is performed (a step 12). Herein, (x) is a correction value when the outside temperature TA is compared with the water temperature TW.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle air conditioner capable of detecting a failure of an engine water temperature sensor or an outside air temperature sensor.

[0002]

2. Description of the Related Art Conventionally, for example, a device shown in FIG. 4 is known as an on-vehicle air conditioner capable of detecting a failure of an engine water temperature sensor or an outside air temperature sensor.

The in-vehicle air conditioner 101 shown in FIG. 1 has an engine water temperature sensor 10 whose resistance value is variable according to the engine water temperature.
2, the outside air temperature sensor 103 whose resistance value is variable according to the outside air temperature, the sensor lines 104 and 105 to which the reference voltage VREF is applied via the serial resistors 101b and 101c, and the sensor lines 104 and 1, respectively.
It is mainly configured by a CPU 101a that detects the voltage of 05. Then, one terminal of each of the sensors 102 and 103 is connected to the sensor lines 104 and 1 respectively.
05, and the other terminals of the sensors 102 and 103 are grounded at the ground point GND.

When the sensor line 104 or 105 is broken, the voltage of the sensor line on the broken side is raised to a substantially reference voltage VREF. Therefore, the CPU 101
The a constantly monitors the voltages of the sensor lines 104 and 105, and when detecting that the voltage has become substantially the reference voltage VREF, determines that the sensor line is disconnected, and the output value from the sensor is set to the alternative value. Fail-safe control such as changing was performed.

[0005]

However, in the case where the above-mentioned conventional vehicle-mounted air conditioner has a structure as shown in FIG.
The following problems have occurred.

FIG. 1 is a diagram showing an example in which an in-vehicle air conditioner controls the room temperature by utilizing the output of a sensor belonging to another in-vehicle device. For example, since the engine water temperature is used by various in-vehicle devices for controlling the engine water temperature, if each in-vehicle device is provided with an engine water temperature sensor, the structure of each device becomes complicated and the manufacturing cost increases. Therefore, the engine water temperature sensor belonging to another vehicle-mounted device is used to simplify the structure of each device and reduce the manufacturing cost.

In FIG. 1, an in-vehicle air conditioner 1 has an outside air temperature sensor 2 similar to the outside air temperature sensor 103, a sensor line 3 to which a reference voltage VREFA is applied via a serial resistor 1b, and a sensor line 13 voltage. Is mainly composed of an amplifier 1c that amplifies the voltage of the sensor and a CPU 1a that detects the voltage of the amplifier 1c and the sensor line 3.
One terminal of the outside air temperature sensor 2 is connected to the sensor line 3
The other terminal of the outside air temperature sensor 2 is grounded at the grounding point GNDA on the side of the vehicle air conditioner 1.

On the other hand, an electronic control unit (hereinafter referred to as "ECU") 11 for controlling fuel supply to the engine, for example, has an engine water temperature sensor 12 similar to the engine water temperature sensor 102 and a reference via a serial resistor 11b. Sensor line 13 to which voltage VREFE is applied
And a CPU 11a for detecting the voltage of the sensor line 13
It is mainly composed of and. One terminal of the engine water temperature sensor 12 is connected to the sensor line 13, and the other terminal of the engine water temperature sensor 12 is connected to the ECU 11.
It is grounded at the grounding point GNDE on the side.

That is, the apparatus of FIG. 1 differs from the apparatus of FIG. 4 in that the engine water temperature sensor 12 does not belong to the vehicle air conditioner 1 side but to the ECU 11 side.

When the above-mentioned conventional failure detection method is applied to the vehicle-mounted air conditioner thus configured, that is, the voltage of the sensor line 13 is the reference voltage VRE on the vehicle-mounted air conditioner 1 side.
When it is determined that the sensor line 13 is broken when it becomes almost equal to FA, the in-vehicle air conditioner 1
Since there is a potential difference between the ground point GNDA and the ground point GNDE of the ECU 11, for example, the voltage of the sensor line 13 may satisfy the relationship of the following equation, and the disconnection may not be determined.

Sensor line voltage = VREFE <VR
EFA + GND potential difference However, the GND potential difference is the ground point GNDA and the ground point GN.
The potential difference from DE is shown.

That is, when the sensor line of the engine water temperature sensor 12 is disconnected when the voltage of the sensor line 13 satisfies the relationship of the above equation, the voltage of the sensor line 13 becomes substantially the reference voltage VREFE, but this reference voltage VREFE.
Is smaller than the actual reference voltage (= reference voltage VREFA + GND potential difference) that the CPU 1a uses as a reference for the disconnection determination.
In 1a, the disconnection cannot be determined.

As a countermeasure against this, a GND potential difference is estimated,
ECU for the reference voltage VREFA on the vehicle air conditioner 1 side
It is also conceivable to judge the disconnection of the sensor line with reference to the voltage at which the potential of the reference voltage VREFE on the 11 side becomes the lowest.

FIG. 5 shows the reference voltage VR in the apparatus of FIG.
It is a figure which shows an example of the relationship of EFE, VREFA, and GND electric potential difference.

In the example of FIG. 5, the ground point G of the vehicle air conditioner 1
The potential of NDA is higher than the potential of the ground point GNDE of the ECU 11, and the reference voltage VRE is used because there are other components that use the reference voltages VREFE and VREFA in addition to the engine water temperature sensor 12 and the outside air temperature sensor 2.
There is variability in FE and VREFA. The minimum values of the reference voltages VREFE and VREFA caused by this variation are respectively set as the minimum reference voltages VREFEMIN and VREFAMIN, and the maximum values thereof are respectively set to the maximum reference voltages VREFEMAX and VREFAMAX.
And Also, the ground point GNDA with respect to the ground point GNDE
If the maximum potential of is the maximum potential VGNDAMAX, in the example of the figure, the maximum potential VGNDAMAX> ground point GNDE
Therefore, the GND potential difference becomes a positive value. Therefore, the voltage value of the sensor line 13 detected by the CPU 1a of the in-vehicle air conditioner 1 is substantially a value smaller by the GND potential difference.

Reference voltages VREFE, VREFA and G
When the ND potential difference has such a relationship, the CPU 1a
It is also conceivable to set the voltage used as the reference for the disconnection determination to a "determination voltage (= minimum reference voltage VREFEMIN)" in FIG. 5, that is, a predetermined voltage value smaller than the minimum reference voltage VREFAMIN.

However, the judgment voltage is set to the minimum reference voltage V
If you set a predetermined voltage value smaller than REFAMIN, C
When the PU1a detects the predetermined voltage value, the resistance value of the engine water temperature sensor 12 is high, that is, the PU1a is the voltage value generated in the sensor line 13 due to the low engine water temperature, or the sensor line is broken. There is a problem in that it may not be possible to distinguish whether or not the voltage values are different.

The present invention has been made in view of the above problems. Even when one of the engine water temperature sensor and the outside air temperature sensor is provided on the side of another vehicle-mounted device, the sensor line It is an object of the present invention to provide an in-vehicle air conditioner capable of accurately determining a disconnection.

[0019]

In order to achieve the above object, the present invention provides an in-vehicle air conditioner equipped with an engine water temperature sensor for detecting engine water temperature and an outside air temperature sensor for detecting outside air temperature. It has a failure detection means for detecting a failure of the one sensor by comparing the outputs of the two.

According to the configuration of the present invention, the failure of one of the engine water temperature sensor and the outside air temperature sensor is detected by comparing the outputs of the engine water temperature sensor and the outside air temperature sensor. Even when the sensor is provided on the side of the other vehicle-mounted device, it is possible to accurately determine the disconnection of the sensor line of the one sensor.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a schematic configuration of an on-vehicle air conditioner according to an embodiment of the present invention. Since the vehicle-mounted air conditioner 1 of the present embodiment is different from the device described in the conventional example only in the control processing executed by the CPU 1a, the device of the conventional example is used, and the description of its constituent elements is omitted. To do.

As described above, only the outside air temperature sensor 2 belongs to the in-vehicle air conditioner 1 side, and the engine water temperature sensor 12 belongs to the ECU 11 side. Therefore, when the in-vehicle air conditioner 1 uses the engine water temperature, the sensor Via line 13
The output of the engine water temperature sensor 12 connected to the ECU 11 (voltage applied to the sensor line 13) is detected. That is, in the present embodiment, vehicle-mounted air conditioner 1 determines whether or not the sensor line of engine water temperature sensor 12 is broken. However, the engine water temperature sensor 12 is not limited to this.
Belongs to the in-vehicle air conditioner 1 side, and the outside air temperature sensor 2 is connected to the ECU 1
When it belongs to the other in-vehicle device side such as 1, the disconnection of the outside air temperature sensor 1 can be determined by the same method as the control process described later.

FIG. 2 is a flow chart showing a procedure of control processing executed by the CPU 1a. Of the processes executed by the CPU 1a, the process of this flowchart shows only the process of determining the disconnection of the sensor line of the engine water temperature sensor 12, and actually, the CPU 1a also performs other processes. Since it is not an essential process for explaining the above, the illustration and description of the process will be omitted.

In the figure, first, the voltage of the sensor line 13 is detected, and the detected value is set as the detected voltage VTW (step S1).

Next, it is judged whether the detected voltage VTW is within the range of the upper limit value and the lower limit value of the voltage detected when the sensor line of the engine water temperature sensor 12 is broken (step S2), and the detection is performed. If the voltage VTW is within this range, the engine water temperature TW is calculated from the detected voltage VTW (step S3).

In the following step S4, the above-mentioned step S1
Similarly, the voltage of the sensor line 3 is detected, and the detected value is set as the detection voltage VTA.

In step S5, whether the outside air temperature sensor 2 is operating normally, for example, whether the detected voltage VTA is substantially the reference voltage VREFA, that is, whether the sensor line of the outside air temperature sensor 2 is broken or not. It is determined whether or not the outside air temperature sensor 2 is operating normally (detection voltage V
When TA <substantially reference voltage VREFA, the outside air temperature TA is calculated from the detected voltage VTA in the same manner as in step S3 (step S6).

Next, it is determined whether or not the calculated engine water temperature TW and outside temperature TA satisfy the following equation (1) (step S7).

TA> TW + x (1) However, x is the factor that the outside air temperature sensor 2 is exposed to sunlight after the low temperature soak, and the temperature TA detected by the outside air temperature sensor 2 becomes the engine water temperature TW. The correction value (temperature) in consideration of the highest rise is shown.

FIG. 3 shows the outside air temperature sensor 2 during low temperature soak.
Air temperature and engine water temperature sensor 12 detected by
It is a diagram showing a transition of the engine water temperature detected by,
(A) shows a transition of the outside air temperature TA and the engine water temperature TW detected when the engine is started after the low temperature soak, and (b) shows the outside air temperature TA detected when the low temperature soak is performed after the engine is stopped. And (c) shows the transitions of the outside air temperature TA and the engine water temperature TW detected when the outside air temperature sensor 2 is exposed to sunlight after the low temperature soak. In the figure, the vertical axis represents the detected temperature and the horizontal axis represents time.

As can be seen from the graph (c), when the outside air temperature sensor 2 is exposed to sunlight after the low temperature soak, the detected outside air temperature TA rises by Δα ° C. above the detected engine water temperature TW. In the above formula (1), this increase Δα ° C. is considered as the temperature x. In the present embodiment, the amount of increase x is a constant Δα, but the amount of increase x is not limited to this and may be regarded as a variable.

The fact that the sensor line of the engine water temperature sensor 12 is broken can be determined from the above equation (1) when the engine water temperature sensor 12 is operating normally, as shown in FIGS. This is because the detected outside temperature TA does not become higher than the detected engine water temperature TW, as indicated by (). However, as described above, it is necessary to consider an exception such as that the outside air temperature sensor 2 is exposed to sunlight after the low temperature soak.

Returning to FIG. 2, TA>
When TW + x, the state of the flag Ft, which is indicated by "1", indicating that the timer t is measuring time is judged (step S8). Here, the timer t uses the steps S2, S
This is for measuring the time for which the state in which all of the conditions of S5 and S7 are satisfied continues.

When the flag Ft = 0 in the determination in step S8, that is, when the timer t has not yet started to count the time, the flag Ft is set ("1") (step S8).
9) After that, the timing of the timer t is started (step S1).
0).

On the other hand, the flag Ft =
When it is 1, that is, when the timer t is measuring time, it is determined whether the time t of the timer t is a predetermined time T (for example, several seconds) or more (step S11). When t ≧ T in this determination, that is, in steps S2, S5, and S7,
When the condition satisfying all of the conditions is continued for a predetermined time T, it is determined that the sensor line of the engine water temperature sensor 12 is broken, and the output value from the engine water temperature sensor 12 is changed to a substitute value, or the fail-safe operation is performed. After performing the control (step S12), the control process is ended.
On the other hand, when t <T in the determination of step S11, that is, the state in which all the conditions of steps S2, S5 and S7 are satisfied does not reach the predetermined time T, and the sensor line of the engine water temperature sensor 12 is disconnected. If it cannot be determined, this control process is immediately terminated.

On the other hand, when the detected voltage VTW is not within the voltage range at the time of disconnection in the judgment of the step S2, or when VTA≈VREFA is judged in the step S5, or TA ≦ TW + x is judged in the judgment of the step S7. At this time, the flag Ft is reset (“0”) (step S13), the timer t is reset to stop the time measurement (step S14), and then the control process is ended.

As described above, in the present embodiment,
By comparing the output detected by the outside air temperature sensor 2 operating normally and the output detected by the engine water temperature sensor 12, it is determined that the sensor line of the engine water temperature sensor 12 is broken. Even if the voltage applied to the sensor line fluctuates, the disconnection of the sensor line can be accurately determined.

As described above, in the present embodiment,
Although the disconnection of the sensor line of the engine water temperature sensor 12 is determined, the invention is not limited to this.
When the connection states of the outside air temperature sensor 2 and the outside air temperature sensor 2 are opposite, the disconnection of the outside air temperature sensor 2 can be determined by the same method as the above method.

[0040]

As described above, according to the present invention,
Since the failure of one of the engine water temperature sensor and the outside air temperature sensor is detected by comparing the outputs of the engine water temperature sensor and the outside air temperature sensor, one of the engine water temperature sensor and the outside air temperature sensor is provided on the other in-vehicle device side. Even in such a case, it is possible to accurately determine the disconnection of the sensor line of the one sensor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a schematic configuration of an in-vehicle air conditioner according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of control processing executed by a CPU on the in-vehicle air conditioner side of FIG.

3 is a diagram showing changes in the outside air temperature detected by the outside air temperature sensor of FIG. 1 and the engine water temperature detected by the engine water temperature sensor during a low temperature soak.

FIG. 4 is a schematic configuration diagram showing a schematic configuration of a conventional vehicle air conditioner.

5 is a diagram showing reference voltages VREFE and VR in the apparatus of FIG.
It is a figure which shows an example of the relationship of EFA and GND electric potential difference.

[Explanation of reference numerals] 1 vehicle-mounted air conditioner 1a CPU (fault detection means) 2 outside air temperature sensor 12 engine water temperature sensor

Claims (1)

[Claims] 1. An in-vehicle air conditioner comprising an engine water temperature sensor for detecting an engine water temperature and an outside air temperature sensor for detecting an outside air temperature, the failure of one of the sensors being detected by comparing outputs of the both sensors. An in-vehicle air conditioner having a failure detecting unit for detecting.