JPH115436A - Air conditioner for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately detects the failure condition of a temperature detecting means of an evaporator by comparing the signal from a turning-on/off detecting means for detecting the turning on/off time of a compressor and the signal from a turning-on/off estimating means for estimating the turning-on/off time with each other. SOLUTION: A thermistor 5 as an evaporation temperature detecting means is arranged in the downstream of an evaporator 4. Cabin-inside and cabin-outside various condition detecting signal, which gives an influence to the turning-on/off control of a compressor 1, is input to a first computing unit 7, and the turning- on/off time is estimated. Real turning-on/off time is input, to a second computing unit 8 from a turning-on/off detecting device 16. A failure judging unit 9 compares the estimated turning-on/off time and the real turning-on/off time are compared with each other. In the case where a time difference of both the turning-on time and turning-off time is within the range at ±30% of the estimated time, the thermistor 5 is judged normal. In the case where the time difference exceeds the predetermined value continuously ten time, failure of the thermistor 5 is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle air conditioner, and more particularly to a vehicle air conditioner capable of detecting a failure of an evaporator temperature detecting means for detecting an air temperature downstream of an evaporator.

[0002]

2. Description of the Related Art In general, in a vehicle air conditioner, a heat exchange medium of a high temperature and a high pressure by a compressor flows into a condenser provided in a front part outside the vehicle and is cooled by exchanging heat with outside air. After it is easily vaporized, it flows into the evaporator and absorbs heat from the air passing through the evaporator to vaporize, and then returns to the compressor and circulates again.

[0003] The drive (on / off) control of the compressor is performed based on the temperature detected by an evaporator temperature detector provided downstream of the evaporator. Usually, a thermistor whose resistance value changes in accordance with a difference in temperature is used as the evaluation temperature detecting means. Although the thermistor is coated with a material having excellent waterproof properties, condensed water is likely to adhere to the downstream side of the evaporator, and is likely to be damaged by inundation due to respiration.

Conventionally, a failure of a thermistor is determined by detecting a change in resistance value from a voltage value, and if the voltage value is within a predetermined range, it is determined to be normal.

[0005]

By the way, the failure of the thermistor includes not only disconnection and short circuit but also a considerable number of cases in which it is impossible to detect an appropriate temperature with a predetermined resistance value due to aging deterioration or the like. is there. This failure occurs when water adheres to the surface of the electrode due to water infiltration due to the respiration, and ionization occurs due to energization.

[0006] In such a failure, the resistance value of the thermistor, that is, the voltage value applied to the thermistor is within a predetermined range set in advance, and there is a problem that the failure cannot be detected by the conventional method.

Accordingly, an object of the present invention is to provide an air conditioner for a vehicle which can appropriately detect a failure state of an evaporator temperature detecting means.

[0008]

In order to achieve the above object, the present invention comprises an evaporator temperature detecting means for detecting an air temperature downstream of an evaporator, and a compressor based on the detected temperature from the evaporator temperature detecting means. An on / off detecting means for detecting the on / off time of the compressor, and an on / off for predicting the on / off time of the compressor based on various conditions inside and outside the vehicle. It is provided with an OFF predicting means and a failure estimating means for estimating a failure of the evaluation temperature detecting means by comparing signals from the ON / OFF detecting means and the ON / OFF predicting means.

The failure estimating means may estimate that the evaporator temperature detecting means is faulty when the difference between the signals from the on / off detecting means and the on / off estimating means exceeds a predetermined value.

Thus, even if the failure cannot be determined only from the value detected by the evaporator temperature detecting means, the presence or absence of the failure can be detected based on other detection data.

The on / off predicting means includes an outside air temperature detecting means for detecting an outside air temperature, an inside air temperature detecting means for detecting an inside air temperature, a blower voltage detecting means for detecting a voltage applied to an in-vehicle fan. The on / off time of the compressor may be predicted based on the detection signal from the engine speed detecting means for detecting the engine speed.

Each of the detection means turns on the compressor.
Any condition can be used as long as the condition affecting the turning off can be detected.

Therefore, when the outside air is introduced, the compressor is turned on and off based on detection signals from the outside air temperature detecting means, the blower voltage detecting means and the engine speed detecting means.
The off time is predicted, and in the case of inside air circulation, the on / off time of the compressor may be predicted based on detection signals from the inside air temperature detecting means, the blower voltage detecting means and the engine speed detecting means.

[0014]

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

FIG. 1 shows a circulation cycle of a heat exchange medium in a vehicle air conditioner according to the present invention. In this circulation cycle, the heat exchange medium returns to the compressor 1 from the compressor 1 via the condenser 2, the throttle valve 3, and the evaporator 4, and circulates as in the conventional case. A thermistor 5 serving as an evaporator temperature detecting means is provided downstream of the evaporator 4. The thermistor 5 changes its electric resistance value based on the temperature change of the air flowing around the thermistor 5. The periphery is coated with a material having excellent waterproof properties, and the detection signal is input to the control device 6. I have.

The control device 6 includes a first calculation unit 7 and a second
An arithmetic unit 8 and a failure determination unit 9 are provided.

The first arithmetic unit 7 includes various conditions inside and outside the vehicle which are considered to affect on / off control of the compressor 1 from the outside air sensor 10, the inside air sensor 11, the blower voltage detecting device 12, the engine speed detecting device 13, and the like. A detection signal is input. Then, based on these detection signals, the on / off time of the compressor 1 is predicted as described later. The outside air sensor 10 is provided at a front part of the vehicle and detects an outside air temperature. The inside air sensor 11
It is arranged in the front part in the vehicle and detects the inside air temperature. The blower voltage detection device 12 detects a voltage value applied to a blower motor 14 a that drives the in-vehicle blower fan 14. The engine speed detector 13 detects the speed of the engine 15.

The second arithmetic section 8 is supplied with a detection signal from an on / off detection device 16 for detecting the on / off state of the compressor 1.

The detection signal (voltage applied to the thermistor 5) from the thermistor 5 is input to the failure determination unit 9. Then, the on time Ton and the off time Toff of the compressor 1 predicted by the first arithmetic unit 7
And the actual ON time Ton 'and OFF time Toff' of the compressor 1 input to the second arithmetic unit 8 to detect a failure of the thermistor 5 and drive a notification unit 17 such as a buzzer as described later. It has become.

The failure detection (with a constant resistance value) of the thermistor 5 by the vehicle air conditioner having the above-described configuration is as follows.

As shown in the flowchart of FIG. 2, first, detection data including the outside air temperature Tout, the inside air temperature Tin, the blower voltage V, and the engine speed R is read from each of the detection means 10, 11, 12, and 13 (step S1). ).
Then, the on-time Ton and the off-time Toff of the compressor 1 are predicted from the read detection data (steps S2 and S3). Further, the actual on-time Ton 'and off-time Toff' of the compressor 1 are read (Step S).
4).

Next, the predicted on-time Ton and off-time Toff are compared with the actual on-time Ton 'and off-time Toff', respectively (steps S5 and S6). As a result of comparison, any time difference (absolute value) between ON time and OFF time
Is also ± of the predicted on-time Ton and off-time Toff.
Values within 30% (in FIG. 2, on time is x, off time is y
Indicated by ), It is determined that the thermistor 5 is operating normally, and the on / off control of the compressor 1 is continued based on the temperature detected by the thermistor 5.

Further, even if any one of the time differences is ± 30%
If the time difference exceeds the predetermined time (step S7), it is determined whether or not the time difference exceeds ± 30% for 10 consecutive times (step S8).

As a result, the time difference was ± 30 consecutively for 10 times.
If not, the steps S1 to S4 are repeated again. If it exceeds, the thermistor 5 is judged to be faulty, and this is reported (step S1).
9) The compressor 1 is kept off (step S10).

Thus, the failure of the thermistor 5 having a constant resistance value, which cannot be detected by the conventional method, is detected, and the evaporator 4 is prevented from freezing.
It is now possible to prevent failure.

The prediction of the on / off time of the compressor 1 (steps S2 and S3) uses a graph determined as follows.

A graph for estimating the on-time is based on experiments. First, the on-time of the compressor 1 with respect to each data detected by the outside air sensor 10, the inside air sensor 11, the blower voltage detecting device 12 and the engine speed detecting device 13 is shown. The change rates of Ton1 to Ton4 were determined.

More specifically, the conditions including the inside air temperature Tin, the blower voltage V and the engine speed R were kept constant, and only the outside air temperature Tout was changed to detect the on-time Ton1.
The results obtained are as shown in FIG.

Similarly, only the inside air temperature Tin, only the blower voltage V, and only the engine speed R are changed to detect the on-time Ton2 to Ton4. The obtained results are as shown in the graphs of FIGS.

As described above, the ON time T of the compressor 1
Since only one of the four conditions affecting on is changed, the relationship (change rate) between the changing condition and the on-time Ton can be detected without being affected by other conditions. .

Next, by making the outside air temperature Tout, the inside air temperature Tin, the blower voltage V, and the engine speed R different from each other, the ON times Ton1 to Ton are obtained for the four cases.
4 were detected. Here, the ON times Ton1 to Ton4 were respectively detected under the conditions shown in the following table.

[0032]

[Table 1]

From these values and the graphs of FIGS. 3 to 6, αon to δon were calculated according to the following equations.

[0034]

(Equation 1)

Each graph was determined by calculating αon to δon from the simultaneous equations.

The graph for estimating the off-time of the compressor 1 was made as follows in the same manner as the on-time estimation. However, when the compressor 1 is in the off state, the engine speed R has no effect. Therefore, the off time is predicted based on the outside air temperature Tout, the inside air temperature Tin, and the blower voltage V.

Only the outside air temperature Tout, only the inside air temperature Tin,
The results obtained by changing only the blower voltage V are shown in FIGS.
This is as shown in the graph of FIG.

In the same manner as described above, the off times were respectively detected under the conditions shown in the following table, and αoff to γoff were calculated from these values and the graphs in FIGS.

[0039]

[Table 2]

Based on the determined graph, each of the detection data input from the outside air sensor 10, the inside air sensor 11, the blower voltage detector 12, and the engine speed detector 13 is turned on time Ton and off time Toff according to the following equations. Were calculated, and by adding these, the on / off time of the compressor 1 was predicted.

(Equation 2)

As described above, in the embodiment, the on / off time of the compressor 1 can be predicted based on the outside air temperature Tout, the inside air temperature Tin, the blower voltage V, and the engine speed R. Therefore, even if the thermistor 5 fails while having a constant resistance value, it can be detected.

In the above embodiment, the air-conditioning state is not taken into account. However, the method of estimating the on / off time of the compressor 1 may be different between the case where the air conditioning in the vehicle is the inside air circulation and the case where the outside air is introduced. .

That is, in the case of the inside air circulation, the inside air temperature Ti
The on / off time of the compressor 1 is predicted from n, the blower voltage V and the engine speed R. In the case of introducing outside air, the on / off time of the compressor 1 is predicted from the outside air temperature Tout, the blower voltage V, and the engine speed R. The graph for prediction is determined in the same manner as in the above embodiment.

[0044]

As is apparent from the above description, according to the vehicle air conditioner of the present invention, the on / off state of the compressor is determined based on various conditions inside and outside the vehicle that affect the driving of the compressor.
Since the on / off prediction means for predicting the off time is provided,
From the deviation from the actual on / off time, it is possible to detect a failure of the evaporator temperature detecting means with a constant resistance value, which cannot be detected conventionally.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a vehicle air conditioner according to the present invention.

FIG. 2 is a flowchart for detecting the presence or absence of a failure of the thermistor shown in FIG.

FIG. 3 is a graph showing the relationship between the outside air temperature and the ON time of a compressor.

FIG. 4 is a graph showing the relationship between the inside air temperature and the ON time of the compressor.

FIG. 5 is a graph showing a relationship between a blower voltage and an ON time of a compressor.

FIG. 6 is a graph showing the relationship between the engine speed and the ON time of the compressor.

FIG. 7 is a graph showing the relationship between the outside air temperature and the off-time of the compressor.

FIG. 8 is a graph showing the relationship between the inside air temperature and the off time of the compressor.

FIG. 9 is a graph showing a relationship between a blower voltage and a compressor off time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 4 Evaporator 5 Thermistor (evaporation temperature detection means) 6 Control device 7 1st arithmetic part (ON / OFF prediction means) 9 Failure determination part (Failure estimation means) 16 ON / OFF detection apparatus (ON / OFF detection means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuko Nakashiki 5658 Yoshikawa, Hachihonmatsu-cho, Higashihiroshima-shi, Hiroshima Japan Climate Systems Co., Ltd.

Claims (4)

[Claims] 1. An air conditioner for a vehicle, comprising: evaporator temperature detecting means for detecting an air temperature downstream of an evaporator; and controlling on / off of a compressor based on a temperature detected by the evaporator temperature detecting means. On / off detection means for detecting the on / off time of the compressor, on / off prediction means for estimating the on / off time of the compressor based on various conditions inside and outside the vehicle, the on / off detection means and on / off A vehicle air conditioner comprising: failure estimating means for estimating a failure of the evaporative temperature detecting means by comparing signals from the estimating means. 2. The failure estimating means estimates that the temperature estimating means is faulty when the difference between the signals from the on / off detecting means and the on / off estimating means exceeds a predetermined value. The vehicle air conditioner according to claim 2, wherein: 3. The on / off predicting means includes: an outside air temperature detecting means for detecting an outside air temperature; an inside air temperature detecting means for detecting an inside air temperature; and a blower voltage detecting means for detecting a voltage applied to a fan for blowing air in the vehicle. An engine speed detecting means for detecting an engine speed;
The vehicle air conditioner according to claim 1 or 2, wherein the on / off time of the compressor is predicted based on a detection signal from the vehicle. 4. The on / off prediction means predicts an on / off time of a compressor based on detection signals from an outside air temperature detecting means, a blower voltage detecting means and an engine speed detecting means in the case of introducing outside air. 4. The method according to claim 3, wherein in the case of internal air circulation, the on / off time of the compressor is predicted based on detection signals from the internal air temperature detecting means, the blower voltage detecting means and the engine speed detecting means. Vehicle air conditioner.