JPS58122215A - Air conditioner for automobile - Google Patents

Abstract

PURPOSE:To extend the service life and improve the drivability of a titled device by a method wherein the ratio of rest time of cooling device operation is automatically adjusted in accordance with the cooling load, while the configuration of the relevant circuit is formed so as to maintain the driving/resting cycle at a constant value. CONSTITUTION:When the cooling switch for the lowest temperature is at OFF state, the comparator A2 of a square wave generator 40 for a control unit generates square waves while performing the comparison with the output of a triangle-wave generator 30 with and an adjusting resistor VR, and the divided voltage of a fixed resistor R2 as a reference voltage. Accordingly, a rectangular wave being formed in accordance with the combined resistance consisting of an upstream side sensor Ra the detected temperature of the upstream side sensor Ra is outputted and the energizing time period between the input terminal (a) and the output terinal (b) of a drive circuit 60 is suitably adjusted. Therefore, the switching ON/OFF operation of the drive circuit 60 is performed based upon said energizing time length, resulting in the determination of the operation time length of the cooling device. On the other hand, when the cooling switch for the lowest temperature is at ON state, the cooling device operation is continued regardless of the change in the temperature of the upstream side sensor Ra, thereby extending the service life and improving the drivability of the titled device.

Description

[Detailed description of the invention] The present invention relates to an air conditioner for an automobile.

In a known device of this type, as shown in the system diagram of FIG. Rec,
High pressure pressure suinochi 11. The air passes through the low-pressure gas inch 10, expands with the expansion valve Ev, and after being endothermically gasified in the evaporator (1) Evp, circulates through the circuit returning to the compressor 12, while the air sucked in by the fan 6 is cooled in the evaporator Bvp. Later, the upper part of the car was blown out, and the lower part of the inside of the car was blown out.

The air is divided into three sides of the defroster air outlet.

As shown in the circuit diagram of FIG. 2, this air conditioner is controlled by turning on the ignition switch 2 using the battery 1 as a power source, the relay 3 is energized, its contact 3a is turned on, and by selecting the position of the fan switch 4, The voltage of the evaporator fan motor 6 is controlled via the resistor 5, and the fan switch 4 is in the position [).

When either M or H is selected, the air conditioner switch 70 is turned on and the thermostat 9 for controlling the air outlet temperature inside the vehicle is turned on.
．． The relay 8 is energized via the compressor protection low pressure case 10 and the high pressure switch 11, and its contact 8a is turned on, so that the electromagnetic clutch 12' is energized and the compressor 12 is driven by the engine (2). , a cooling operation circuit is configured.

As the compressor 12 operates, the temperature of the evaporator Evp decreases, and the air passing through it is cooled and blown into the vehicle.
Detects the air temperature at or near that temperature, controls the compressor on and off so that the temperature remains constant, and sets the temperature on the thermostat to generally be around O'C, which prevents the evaporator from freezing. Ru.

The temperature control of the air blown into the car by modern car air conditioners is generally done by the so-called air mix method, in which the air is cooled by an evaporator, dehumidified, reheated by a heater, and then blown into the car at an appropriate temperature. If you input 7, the compressor will always be efficient and the porator temperature will be Q
Since the compressor is operated to maintain a temperature close to C, the compressor is operated frequently even in the mid-season or winter months when it does not require much cooling capacity (3), causing deterioration in fuel efficiency and drivability.

Some methods to solve this problem include detecting the temperature inside the car, outside air temperature, etc., and controlling the cooling cycle on and off so that the temperature at or near the evaporator port changes depending on the inside temperature or the outside air temperature. In such a device, the on/off interval or period of the cooling cycle is shortened due to the cooling load, the durability life of the electromagnetic clutch is shortened, the on/off frequency is high, and drivability is deteriorated.

The present invention has been proposed in view of the above circumstances, and aims to provide an automotive air conditioner that extends its service life and improves drivability, and includes means for detecting an air conditioning load; (4) A circuit that automatically changes the time ratio of operation and stop of the cooling device based on the detected value of the air conditioning load, and a circuit that keeps the period of operation and stop of the cooling device constant during operation. It is characterized by

An embodiment of the present invention will be explained with reference to the drawings. FIG. 3 is a system diagram thereof, FIG. 4 is a control circuit diagram of FIG. 3, FIG. 5 is a partially enlarged view of FIG. 4, and FIGS. Figures are number 5
A voltage waveform diagram at points A and B in the figure, and FIG. 8 is a diagram showing the relationship between the upstream sensor temperature and the cooling device operating rate according to the present device in FIG. 4.

First, in Figs. 3 and 4, the same symbols as in Figs. 1 and 2 indicate the same members as in Figs. 1 and 2, respectively, and R and a are negative characteristic thermistors (hereinafter referred to as 11. The upstream sensor Ra may be a sensor that detects the temperature inside the vehicle, the temperature outside the vehicle, or the temperature of both the interior of the vehicle and the outside air.11. 11. e is a negative characteristic thermistor (hereinafter referred to as evaporator sensor) that detects the evaporator temperature or the temperature near it; 11. a, R
The detected value of e is input to the controller 20.

Figure 4 shows a configuration in which the drive circuit section of the controller 20 (input terminal a and output terminal 1 in Figure 5) is connected between the air conditioner switch 7 and the low pressure cass inch 100 instead of the thermostat 9 (5) in Figure 2. As will be described later, the operation of the compressor 12 is controlled to be turned on or off via the relay 8.

That is, the controller 20, as shown in FIG.
A triangular wave generator (or sawtooth generator) 30, a square wave generator 40 which uses this output as an input on one side and a reference voltage determined by an upstream sensor Ra as a + side input and generates a square wave; It is composed of a drive circuit 60 that responds to the output of the wave generator 40, and a frost prevention circuit 50 that turns off the drive circuit 60 when the evaporator temperature is below a predetermined value based on the detected value of the evaporator sensor Re, and at the same time re-centers the triangular wave generator 30. . Although not specifically described, the controller 20 has a constant voltage circuit that generates a constant voltage Vcc for control.

First, the triangular wave generator 30 is an integrator consisting of a square wave generator having a capacitor C1 at -(6) inputs of an amplifier A1, and a negative feedback circuit C, r(, The output waveform becomes a triangular wave shown in FIG. 6 at point A, and has a constant period indicated by tl.

This (and capacitor CI, C2, fixed resistance ■ (11~R
6 and R22, r(, 23 are appropriately selected as constants that determine the peak value and frequency, and this frequency becomes the cycle for turning on and off the cooling device, and generally has a constant value of 60 seconds before and after.

Next, the square wave generator 40 inputs the output of the triangular wave generator 30 to one terminal, compares it with a reference voltage determined by the temperature of the upstream sensor, and generates a T-T or L level square wave. The output voltage VB at point B becomes a square wave as shown in FIG. "The higher the temperature of the second-flow sensor, the greater the on-time (H level) ratio becomes. (7) Depending on the relationship with the driving circuit 60, it is turned on when it is at H level and turned off when it is at L level. Note that an adjustment resistor VR is inserted in series with the upstream sensor I%a, and Ra and VR,
A coldest switch SW is provided to bypass the fixed resistances Rr~R, I+, which determine control constants.

Further, the drive circuit 60 is composed of transistors Tr+ and Tr2 which are connected in a darling manner, and the square wave generator 4
When the output voltage VB of the frost prevention circuit 50 and the output voltage Vc of the frost prevention circuit 50 are I-level, a switching circuit is constructed that conducts between the input terminal a and the output terminal 1), and
, +s is a fixed resistance.

The frost prevention circuit 50 also includes a comparator A4 which compares the voltage determined by the evaporator sensor Re as a negative input with a reference voltage on the positive side, and generates a level output when the evaporator temperature falls below a predetermined temperature. The output side is the transistor Tr+ of the drive circuit 60.
The base of the comparator A4 is connected through a diode D1 which blocks this when it is at the T-f level (8), and is connected to the base side of the transistor 3 which discharges the charge of the capacitor CI of the triangular wave generator 30. is,
l(, 1a to i%2a are fixed resistances that determine the control constants.

In such a device, if the air conditioner switch 7 shown in FIG. 4 is turned on and the cooling device is on, and the coldest switch SW is open in FIG.
0 comparator A3 is connected to upstream sensor Ra and adjustment resistor V
Combined resistance and fixed resistance of R1]'(, 90 minutes voltage is used as a reference voltage and compared with the output of the triangular wave generator 30 to generate a square wave. Therefore, if the temperature detected by the upstream sensor R, a is high,
The reference voltage of comparator A3 becomes high and outputs a long square wave of F level, and the input terminal a of the drive circuit 60 and the output terminal 1)
conduction time becomes longer. Conversely, the upstream sensor It, a
When the detected temperature of the comparator A3 is low, the reference voltage of the comparator A3 decreases, outputting a short square wave with a level T (level T), and driving circuit 60
The conduction time between the 0 Å force terminal a and the output terminal (9) becomes shorter. Therefore, the duty ratio of the operating time of the cooling device controlled by the switching of the drive circuit 60 is determined by the detected temperature of the upstream sensor I(, a), and the adjusting resistor connected in series with the upstream sensor Ra. By adjusting vTt,
This condition can be adjusted as shown in FIG. Furthermore, when the coldest switch SW is closed, the comparator A3 can be fixed to the T-rubel regardless of the temperature change of the upstream sensor 1 (a), that is, the cooling device can be operated continuously.

On the other hand, if the evaporator temperature falls below a predetermined temperature, for example O'C, due to operation of the cooling device, the evaporator will freeze.
0, the voltage produced by the evaporator sensor Re and the reference voltage determined by the fixed resistors R116 and R+7 are compared by the comparator A4, and the voltage produced by the evaporator sensor R
, e becomes a predetermined temperature or lower (10), the comparator A4 becomes L level.

Therefore, the base voltage of the transistor Tri of the drive circuit 60 decreases regardless of the output of the comparator A3, so that there is no continuity between the input terminal a and the output terminal 1), that is, it is turned off, and the cooling device is stopped.

At the same time, since the output of the comparator A4 becomes L level, the transistor Tra is turned on and the charge of the capacitor CI of the triangular wave generator 30 is discharged, thereby stopping the oscillation of the triangular wave and setting it accordingly.

When the evaporator temperature rises due to the cooling system stopping,
The output of the comparator A4 becomes 1 level again, the transistor Tr3 is turned off, and the drive circuit 60 is operated by the triangular wave generator 30 and the square wave generator 40. Here, the diode DI prevents the output of the comparator A4 I- level from being applied to the base of the transistor Tr+, so that when the comparator A4 is at the I4 level, the base voltage of the transistor Tr+ is It is determined by the output voltage of comparator A3 (11).

According to such a device, the following effects can be achieved.

(1) When the temperature detected by the upstream sensor is high, the operating time ratio of the cooling device becomes large, and conversely, when the temperature detected by the upstream sensor is low, the operating time ratio of the cooling device becomes small.

Therefore, in response to the upstream sensor representing the cooling load, the cooling capacity is automatically controlled to the optimum value, making it possible to save power by preventing overcooling.

(2) Since the operating and stopping cycles of the cooling device are always constant, the durability of the electromagnetic clutch that drives the cooling device is improved, and driver reliability is also improved.

(3) When the evaporator temperature drops to the frost temperature, the evaporator sensor activates the frost prevention circuit, stops the cooling system, and generates a triangular wave (
12) When the device is reset and the 70-stroke prevention circuit is released, initialization can be performed to prevent subsequent on/off disturbances.

(4) The optimal value can be easily selected by operating the adjustment resistance that adjusts the degree of cooling according to the passenger's wishes.

(5) At the passenger's request or when it is necessary to dehumidify the interior of the vehicle, the cooling or dehumidifying capacity can be maximized by turning on the coldest switch.

(6) By automatically controlling the functions (1) to (3) above, it is possible to eliminate the troublesome operation and contribute to safe driving.

In short, according to the present invention, there is provided a means for detecting an air conditioning load, a circuit that automatically changes the time ratio between operation and stop of the cooling device based on the detected value of the air conditioning load, and the cooling device operation (13). The present invention is industrially extremely useful because it provides a high-performance air conditioner for automobiles by including a circuit that keeps the cycle of operation and stop constant.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a known car air conditioner, Fig. 2 is a control circuit diagram of Fig. 1, Fig. 3 is a system diagram of an embodiment of the present invention, Fig. 4 is a control circuit diagram of Fig. 3, Figure 5 is a partially enlarged view of Figure 4, Figures 6 and 7 are voltage waveform diagrams at points A and B in Figure 5, respectively, and Figure 8 is the temperature of the upstream sensor according to this device in Figure 4. It is a line diagram showing the relationship between and the cooling device operation/rate. ■...Battery, 2...Ignition switch, 3
... Relay, 3a... Relay contact, 4... Fan switch, 5... Register, 6... Fan, 7...
・Air conditioner switch, 8... Relay, 8a... Relay contact, 10... Low pressure switch, 11... High pressure switch, (14) 12... Compressor, 12'... Electromagnetic clutch, 2
0... Controller, 30... Triangular wave generator, 40...
・Square wave generator, 50...Frost prevention circuit, 60・
... Drive circuit, R, a... Upstream sensor, R, e, Evaporator sensor, SW... Coolest switch, Sub-agent and patent attorney Masafumi Tsukamoto also 1 Evp' / Mitsubo Kasukani ( 15)

Claims (1)

[Claims] means for detecting an air conditioning load; a circuit that automatically changes the time ratio of operation and stop of the cooling device based on the detected value of the air conditioning load; and a circuit that makes the period of operation and stop of the cooling device constant during operation. An air conditioner for an automobile characterized by comprising a circuit.