FR2711731A1 - Detection device relating to the air-conditioning of a motor vehicle with an injection computer - Google Patents

Abstract

The device of the invention comprises a first sensor (36) for measuring the instantaneous value of the high pressure (HP) leaving the compressor (14) of an air-conditioning appliance (12), a second sensor (138) for measuring the instantaneous value of a second information item related to the operation of the air-conditioning appliance, and memory means (44) forming a table with two inputs connected respectively to the two sensors and one output, this table being filled on the basis of previous data regarding the relationship between the power absorbed (PA) by the air-conditioning and chosen ranges of values measured by the first and second sensors, this making it possible instantaneously to provide an estimation of the absorbed power, which estimation is transmitted to an injection computer (10) to adjust the power provided by the engine (M) of the vehicle.

Description

Detection device relating to the air conditioning of a motor vehicle provided with an injection computer
The invention relates to a detection device relating to the air conditioning of a motor vehicle provided with an injection computer, the device being intended to be added to an air conditioning device comprising a closed refrigerant circuit with a compressor, a condenser, a pressure reducing valve and an evaporator, the latter receiving an air flow from a blower to produce a flow of air conditioning, the device comprising an air conditioning computer intended to provide the injection computer with an estimate of the power absorbed by air conditioning, so that it takes into account the instantaneous real needs of the engine, on the one hand for driving the vehicle, and on the other hand for driving the compressor.

The compressor uses, in fact, part of the power of the engine since it is driven by the latter via a clutch which can take two different states under the action of control means.

Even if the compressor only absorbs a small part of the power supplied by the engine when it is running, it becomes increasingly important to have information on the instantaneous power actually absorbed by the compressor to take it into account in the injection parameters, in order to optimize engine efficiency.

This optimization of efficiency makes it possible to reduce fuel consumption and reduce the pollutants emitted in the exhaust gases.

In the absence of such information, the injection computer must compensate for the most severe case, that is to say for the maximum value of the power absorbed, which rarely occurs in practice.

This drawback is not too troublesome in the case of a constant capacity compressor, the operation of which is ensured cyclically by means of the clutch interposed between the engine and the compressor.

Operation is then more or less acceptable since the instantaneous power absorbed is little different from the maximum power.

On the other hand, this drawback becomes much more serious in the case of variable capacity compressors, the use of which is becoming more and more widespread.

Indeed, the actual instantaneous energy consumed by such a compressor can be much lower than its nominal power, that is to say its maximum power.

Consequently, if no change is made to the injection management mode, the compensation by the injection becomes all the more excessive the lower the power actually absorbed by the compressor.

 I1 results in poor engine performance, resulting in excessive fuel consumption and emission of pollutants.

In another field, it is known to provide an electromechanical member, for example of the pressure switch type, mounted on the high pressure side of the air conditioning circuit.

Such a body essentially performs three functions: a first function associated with a high level to provide high pressure security, a second function associated with an intermediate level to ensure the starting or stopping of a second level of ventilation of the condenser and a third function associated with a low level for detecting the lack of refrigerant.

This pressure switch, which can also be replaced by a pressure sensor, therefore does not provide any information to the injection computer.

It had been estimated, for some time, that there could be a simple and one-to-one relationship between the value of the high pressure, that is to say the value of the pressure of the refrigerant at the outlet of the compressor, and the power absorbed by this one.

However, it results from the numerous works and tests carried out by the
Applicant that such a relationship cannot be established.

It is therefore one of the objects of the invention to propose a device making it possible to provide, indirectly, an estimate of the power absorbed by the air conditioning, so that the injection of the engine can be adjusted exactly.

It is also an object of the invention to provide such a device capable of providing such an estimate within acceptable precision limits taking into account increasingly stringent standards in the fight against pollution.

It is another object of the invention to provide such a device which is of reliable construction and of low production cost.

To this end, the invention provides a detection device of the type defined in the introduction, this device comprising - a first sensor for measuring the instantaneous value of the high pressure at the outlet of the compressor, - a second sensor for measuring the instantaneous value of a second information related to the operation of the air conditioning unit, and - memory means forming a table with two inputs, connected respectively to the two sensors, and one output, this table being filled as a function of prior data, on the relationship between the power absorbed by the air conditioning and selected ranges of values measured by the first and second sensors, and instantly providing an estimate of the power absorbed by the air conditioning, an estimate which is sufficiently precise to allow the injection computer to adjust the power supplied by engine.

Thus, the device uses the instantaneous values of two pieces of information, one of which is the high pressure at the outlet of the compressor and the other is linked to the operation of the air conditioning apparatus.

These two pieces of information are applied to the memory means forming a table with two inputs, which provide, as a function of the data they contain, an estimate of the power absorbed by the air conditioning. This estimate is provided by the output of the memory means and applied to the injection computer.

It will be understood that these memory means thus constitute a sort of mapping which makes it possible to define the value of the power absorbed as a function of selected ranges of values measured by the first sensor on the one hand and the second sensor on the other hand.

The estimate of the absorbed power is supplied to the injection computer which takes it into account as an injection parameter.

In a first embodiment of the invention, the second information measured by the second sensor relates to the speed of rotation of the compressor.

In fact, it was found that this speed information, combined with the first information on the value of the high pressure, made it possible to provide a very precise estimate of the power absorbed by the air conditioning.

In practice, this second information can be taken from the speed of rotation of the vehicle engine, since there is a constant transmission ratio between the vehicle engine and the compressor.

In a second embodiment of the invention, the second information measured by the second sensor relates to the temperature of the evaporator.

This second embodiment also makes it possible to give a precise estimate of the pressure absorbed by the compressor.

In this second embodiment of the invention, the second sensor measuring the temperature of the evaporator can be constituted by a thermistor probe placed in the fins of the evaporator.

Alternatively, the second sensor may be a probe placed within the refrigerant.

In a third embodiment of the invention, the second information measured by the second sensor relates to the low pressure at the inlet of the compressor.

This sensor can be placed at any desired location between the evaporator and the compressor.

In a fourth embodiment of the invention, the second information measured by the second sensor relates to the temperature of the outside air flow supplying the blower.

It then suffices to provide a temperature sensor measuring the value of the temperature of the outside air supplying the blower.

These last two embodiments give lower precision than the first two, but nevertheless very acceptable in practice.

Whatever the embodiment chosen, the first sensor can be installed either between the outlet of the compressor and the inlet of the condenser, or preferably between the outlet of the condenser and the inlet of the expansion valve.

In the latter case, the sensor can also be located in the desiccant tank which is generally placed at the outlet of the condenser or even in a part of the regulator.

In the description which follows, given solely by way of example, reference is made to the appended drawings, in which - FIG. 1 is a diagram of an installation of a motor motor vehicle, provided with a detection device according to the invention - Figure 2 is a view similar to that of Figure 1 in a first embodiment of the invention; - Figure 3 is a view similar to Figure 2 in an alternative embodiment - Figure 4 is a graph showing the value of the power absorbed as a function of the pressure of the compressor and different curves representing the speed of the compressor - Figure 5 is a view similar to that of FIG. 2 in a second embodiment of the invention; FIG. 6 is a graph giving the value of the power absorbed as a function of the pressure of the compressor and of various curves representing the temperature of the evaporator; - Figure 7 is a view similar to that of Figure 1 in a third embodiment of the invention; and - Figure 8 is a view similar to that of Figure 1 in a fourth embodiment.

First of all, reference is made to FIG. 1 which represents an installation forming part of a motor vehicle driven by a heat engine M controlled by an injection computer 10 of conventional structure.

The vehicle is equipped with an air conditioning device 12 comprising, in a conventional manner, a closed refrigerant circuit comprising a compressor 14, a condenser 16, a desiccant tank 18, a pressure reducer 20 and an evaporator 22, traversed in this order by the refrigerant.

The evaporator 22 receives an air flow from a blower 24 supplied by an external air flow 26 through a duct 28 to produce a flow of conditioned air 30 intended to be sent into the passenger compartment of the vehicle .

The installation also includes an air conditioning computer 32 connected to the air conditioning device 12 to control its operation according to commands set by the user and parameters defined in advance.

In known manner, the air conditioning computer 32 is also connected to the injection computer 10 by: - a first link 48 also called "AC-ON", by which the air conditioning computer signals to the injection computer that the air conditioning must be start-up, and - a second link 50 also called "AC-OFF", by which the injection computer can prohibit the start-up of the air conditioning, for example when the heat engine is under heavy stress.

The general structure of the installation, as just described so far, is known per se.

this is an all or nothing influence of the injection computer on the air conditioning. This operating mode is not entirely satisfactory, for the reasons already indicated. However, the complexity of the parameters governing the air conditioning circuits has so far been considered as preventing the provision of more advanced interaction, under reasonable cost conditions.

However, the Applicant has observed that better operation can be obtained, subject to an appropriate choice of the parameters measured. In particular, it is currently estimated that the first parameter must be the high pressure at the outlet of the compressor.

Several possibilities then exist, with at least one other parameter. Although the laws are complex, it becomes possible, with a limited number of values stored, to define a representation which is sufficiently precise to allow a satisfactory evaluation of the power demand of the air conditioning on the heat engine.

Thus, in accordance with the invention, the vehicle comprises a detector device 34 which comprises the air conditioning computer 32, a first sensor 36 for measuring the instantaneous value of the high pressure (HP) at the outlet of the compressor 14 and a second sensor 38 for measure the instantaneous value of a second piece of information related to the operation of the air conditioning unit. The sensors 36 and 38 are connected, respectively through links 40 and 42, to two respective inputs of the memory means 44, which deliver an output at 46 making it possible to deliver a precise estimate of the absorbed power (PA) of the compressor 14, which is supplied to the injection computer 10.

The memory means 44, also called "calculation means
PA ", can be considered as an integral part of the air conditioning computer 32, as shown diagrammatically in FIG. 1.

In FIG. 1, the location of the second sensor 38 has not been intentionally specified to show the installation in the general case.

In the first embodiment shown in FIG. 2, the second sensor, designated here under the reference 138, is capable of measuring a second piece of information relating to the speed of rotation of the compressor 14.

This second sensor can be installed directly on the compressor 14 as shown in FIG. 2 or else in any other place of the vehicle giving information on the speed of the engine M.

Indeed, as the compressor 14 is driven by the motor
M with a constant ratio and through a clutch (not shown), it is possible to use, as second information, information taken from the speed of rotation of the engine (in revolutions per minute) provided by the account -tours of the vehicle, for example.

As shown in FIG. 2, the first sensor 36 is installed between the outlet of the compressor and the inlet of the condenser 16.

However, given that the refrigerant is at a particularly high temperature in this portion of the circuit and that the latter is additionally subjected to the vibrations of the compressor, it may be advantageous to place the sensor 36 between the outlet of the condenser 16 and the inlet of the regulator 20, as shown diagrammatically in broken lines in FIG. 2.

In this portion of the circuit, the refrigerant is at low temperature and not very agitated. It should be noted that this portion of the circuit also extends to the desiccant tank 18 and to part of the regulator 20.

We now refer to FIG. 3 which constitutes a variant of FIG. 2.

In this variant, the second information delivered by the second sensor 138 is applied to the injection computer 10 via a line 52 and then to the memory means 44 by a line 54. It will be understood that the installations of FIGS. 2 and 3 operate on the same principle.

To better understand the operation of the memory means of the invention, in the particular case of the aforementioned first embodiment, reference will now be made to FIG. 4 which shows a graph giving the value of the absorbed power (PA) represented by ordered, as a function of the input pressure or high pressure (HP) of the compressor and of curves established for different discrete values V1, V2, Vu, ... Vn of the speed of the compressor.

It has been established experimentally that the PA value can be determined as a function of the HP value for a given speed Vi of the compressor.

On the HP / PA graph, the curves representing the speeds V1 to Vn consist of a first line segment S common, whatever the speed of the compressor, and this as long as the value HP has not reached a threshold HPs which corresponds to a PAS threshold.

As soon as this threshold HP5 is exceeded, the first segment S divides to form a bundle of segments which appear in the manner of a fan and each correspond to the values V1 to Vn mentioned above.

Thus, for a value HPo greater than HPs, and for a given speed Vi of the compressor, there corresponds a value PAo of the power absorbed.

it then suffices to establish a table or cartography by filling it as a function of preliminary data, as defined above, which establishes a relationship between the absorbed power PA and selected ranges of values, namely compressor pressure values (HP) measured by the first sensor and compressor speed values (V) measured by the second sensor.

Such tables can be produced using means accessible to those skilled in the art.

Thus, when the memory means receive, using the previous example, the instantaneous value of the high pressure HPo and the instantaneous value of the speed of the compressor Vi, they automatically deduce therefrom an estimate of the corresponding value of the absorbed power PAo .

On the same principle, it is possible to make other embodiments which differ from the first by the nature of the second information provided by the second sensor.

In the embodiment of FIG. 5, the second sensor, designated here under the reference 238, measures the temperature of the evaporator and thus provides second information relating to this temperature.

The second sensor 238 can be constituted by a thermistor probe, of conventional structure, placed in the fins of the evaporator.

In a variant1 the probe can be placed within the refrigerant itself, for example in a duct or even in the pressure reducer 20.

In this second embodiment, the memory means constitute a table filled as a function of preliminary data on the relationship between the absorbed power PA and of the selected ranges of HP values measured by the first sensor and of temperature values (T) measured by the second sensor.

The graph in FIG. 6 is similar to the graph in FIG. 4 except that it shows curves T1 to Tn established for different discrete values of temperature of the evaporator instead of different discrete values of the speed of the compressor.

As in the case of FIG. 4, there is a common segment for values of HP lower than HP9 and then a bundle of segments in a fan as soon as HP is higher than the aforementioned threshold value.

In the embodiment of FIG. 7, to which we now refer, the second sensor, designated here under the reference 338, is placed between the evaporator 22 and the compressor 14. It thus provides second information relating to the value low pressure (BP) at the compressor inlet.

For this third embodiment of the invention, one could draw a graph similar to those of Figures 4 and 6 above.

In the fourth embodiment of the invention, shown in FIG. 8, the second sensor is designated under the reference 438.

it provides second information relating to the temperature of the external air flow 26 supplying the blower.

Again, it is possible to draw a graph similar to those of Figures 4 and 6.

It should however be noted that the third and fourth embodiments of the invention give a less precise estimate of the value of the power absorbed, compared to the estimates given by the first two embodiments of the invention, especially the first.

In the embodiments of FIGS. 5, 7 and 8, the first sensor 36 can be located in any suitable location, either between the outlet of the compressor and the inlet of the condenser, or preferably between the outlet of the condenser and the inlet regulator.

The device of the invention thus makes it possible to provide a sufficiently precise estimate of the power absorbed by the compressor and to give this information to the injection computer to allow it to adjust the power supplied by the engine.

Claims (10)

Claims 1. Detection device relating to the air conditioning of a motor vehicle provided with an injection computer, the device being intended to be added to an air conditioning device (12) comprising a closed refrigerant circuit with a compressor (14 ), a condenser (16), an expansion valve (20) and an evaporator (22), the latter receiving an air flow (26) from a blower (24) to produce an air-conditioned air flow (30), the device (34) comprising an air conditioning computer (32) intended to provide the injection computer (10) with an estimate of the power absorbed (PA) by the air conditioning, characterized in that it comprises - a first sensor (36 ) to measure the instantaneous value of the high pressure (HP) at the outlet of the compressor (14), - a second sensor (38; 138; 238; 338; 438) to measure the instantaneous value of a second piece of information, linked to the operation of the air conditioning apparatus (12), and - memory means (44) forming a table two inputs, connected to the two sensors respectively. and an output, this table being filled as a function of preliminary data on the relationship between the power absorbed (PA) by the air conditioning and selected ranges of values measured by the first and second sensors, and instantly providing an estimate of the power absorbed ( PA) by air conditioning, an estimate which is sufficiently precise to allow the injection computer (10) to adjust the power supplied by the engine (M). 2. Device according to claim 1, characterized in that the second information measured by the second sensor (138) relates to the speed of rotation of the compressor (14). 3. Device according to claim 2, characterized in that the second information is taken from the speed of rotation of the engine (M) of the vehicle, which thus drives the compressor (14). 4. Device according to claim 1, characterized in that the second information measured by the second sensor (238) relates to the temperature of the evaporator (22). 5. Device according to claim 4, characterized in that the second sensor (238) measuring the temperature of the evaporator (22) is a thermistor probe placed in the fins of the evaporator. 6. Device according to claim 4, characterized in that the second sensor (238) measuring the temperature of the evaporator (22) is a probe placed within the refrigerant. 7. Device according to claim 1, characterized in that the second information measured by the second sensor (338) relates to the low pressure (BP) at the inlet of the compressor (14). 8. Device according to claim 1, characterized in that the second information measured by the second sensor (438) relates to the temperature of the external air flow (26) supplying the blower (24). 9. Device according to one of claims 1 to 8, characterized in that the first sensor (36) is installed between the outlet of the compressor (14) and the inlet of the condenser (16). 10. Device according to one of claims 1 to 8, characterized in that the first sensor (36) is installed between the outlet of the condenser (16) and the inlet of the regulator (20).