Variable capacity compressor control apparatus for vehicle

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable capacity compressor control apparatus for controlling a variable capacity compressor for a vehicle.

2. Description of Related Art

Japanese Patent Application Laid-open Nos. 2000-317467, 2003-90284 and 2003-278660 disclose a refrigerant circulation circuit for an automotive air conditioner commonly. In Japanese Patent Application Laid-open No. 2000-317467, as shown in FIG. 1, the disclosed refrigerant circulation circuit comprises a compressor module CPM having a compressor CP and an outside refrigerant circuit 101. The outside refrigerant circuit 101 includes a condenser 102, an expansion valve 103 and an evaporator 104. In constituents of the compressor CP, a discharge chamber 107 is communicated with the condenser 102 through a communication pipe 108. A fixed choke 108a is interposed in the communication pipe 108. This compressor CP is a type of variable capacity by controlling pressure in a crank chamber 115. For this, the compressor module CPM is provided with a control valve 132 for controlling the pressure in the crank chamber 115 and a compressor ECU (Electronic Control Unit) 177. In order to allow the compressor CP to operate at torque corresponding to a torque setting command from an air-conditioner ECU 180 or an engine ECU 190, the compressor ECU 177 controls an opening degree of the control valve 132, so that the discharge flow rate of the compressor CP is changed to a value corresponding to a desired setting torque. Thus, since the engine ECU 190 dose not estimate a load torque on the compressor CP but employs a value of the load torque as engine control data, there is no need to prepare an estimation map for load torque with respect to each type of vehicle.

In the above-mentioned conventional automotive air conditioner, however, the driving torque of the compressor CP is controlled by altering control signals transmitted from the air-conditioner ECU 180 to the control valve 132 forcibly. Therefore, there is a tendency that during the control of the driving torque of the compressor CP, its amenity is damaged. Additionally, due to controlling of the discharge flow only, there is a possibility that a change in compression ratio causes abrupt torque fluctuations.

SUMMARY OF THE INVENTION

In the above-mentioned situation, it is an object of the present invention to provide a variable capacity compressor control apparatus which is capable of controlling its driving torque without producing such abrupt torque fluctuations.

In order to attain the above object, according to the first aspect of the invention, there is provided a variable capacity compressor control apparatus for a vehicle, comprising: a variable capacity compressor equipped with a control valve capable of changing a discharge volume of a refrigerant for an air conditioner therefrom; a valve control unit electrically connected to the control valve to determine an opening/closing duty ratio thereof on a basis of a preset in-cabin target temperature and various air conditioning parameters and output a compression-ratio control signal for driving the control valve with the opening/closing duty ratio determined; a flow meter arranged in a refrigerant pipe connected to the variable capacity compressor to detect a flow rate of the refrigerant for the air conditioner flowing into the variable capacity compressor; a signal processing unit electrically connected to the flow meter and the valve control unit to generate a flow-rate control signal based on the present flow rate of the refrigerant detected by the flow meter, the signal processing unit inputting the compression-ratio control signal outputted from the valve control unit and outputting a valve control signal formed by the flow-rate control signal and the compression-ratio control signal to the control valve; and an outside control unit electrically connected to the signal processing unit to input a driving condition of the vehicle and output a demand of reducing a driving torque of the variable capacity compressor to the signal processing unit when the present driving condition satisfies a predetermined condition, wherein when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal, thereby changing the valve control signal.

According to the second aspect of the invention, the compression-ratio control signal is a signal in the form of PWM control.

According to the third aspect of the invention, the control valve of the variable capacity compressor comprises: a suction pressure detecting section communicated with a suction chamber of the variable capacity compressor to detect a suction-side pressure Ps of refrigerant sucked into the variable capacity compressor; a discharge pressure detecting section communicated with a discharge chamber of the variable capacity compressor to detect a discharge-side pressure Pd of the refrigerant discharged from the variable capacity compressor; a crank-chamber communicating section communicated with a crank chamber of the variable capacity compressor; a pressure regulating passage formed to communicate the crank-chamber communicating section with the discharge pressure detecting section; a valve section having a valve body movably arranged in the pressure regulating passage and configured to open and close the pressure regulating passage with movements of the valve body in the pressure regulating passage; a pressure regulating spring which is responsive of the suction-side pressure Ps thereby to open and close the valve section; a suction-pressure-chamber communicating passage formed to communicate the suction pressure detecting section with the discharge pressure detecting section; and a driving section electrically connected to the signal processing section to actuate the valve body of the valve section thereby opening and closing the pressure regulating passage.

According to the fourth aspect of the invention, the outside control unit is an engine control unit for controlling a driving source of the vehicle.

According to the fifth aspect of the invention, when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal so as to reduce a voltage of the valve control signal.

According to the sixth aspect of the invention, when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal so as to reduce a pulse width of the valve control signal.

These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompany drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the constitution of a conventional apparatus;

FIG. 2 is a schematic view of an air conditioner for a vehicle, showing one embodiment of the present invention;

FIG. 3 is a circuit diagram showing the constitution of a flow meter on which the embodiment of the present invention is applied;

FIG. 4 is a time chart showing the operating characteristics of a variable capacity compressor in case of controlling its refrigerant flow rate by reducing voltage of control signals applied on a driving part of the compressor through flow control signals; and

FIG. 5 is another time chart showing the operating characteristics of the variable capacity compressor in case of controlling its refrigerant flow rate by reducing pulse-width of control signals applied on the driving part of the compressor through flow control signals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the accompanying drawings, a variable capacity compressor in accordance with an embodiment of the present invention and a control method of controlling the variable capacity compressor will be described below.

[Constitution of Air Conditioner for Vehicle]

Referring to FIGS. 2 and 3, the constitution of an air conditioner for vehicle will be described in detail. FIG. 2 is a structural schematic view of the air conditioner. FIG. 3 is a circuit diagram showing the constitution of a flow meter.

As shown in FIG. 2, the variable capacity compressor 1 of this embodiment constitutes an air conditioner for vehicle, sucks in refrigerant circulating in a pipe 74 under condition of low temperature and low pressure and compresses the refrigerant under condition of high temperature and high pressure for discharge. The discharged refrigerant is cooled down in a condenser 71 and adiabatically expanded at an expansion valve 72. In succession, the refrigerant changes its state into condition of low temperature and low pressure on absorbing heat from air passing through an evaporator 73 and is sucked into the variable capacity compressor 1 for next circulation in the pipe 74. Note that as a result of drawing heat by the refrigerant in the evaporator 73, air becomes dehumidified cool air.

The variable capacity compressor 1 is arranged outside a vehicle cabin, for example, in an engine compartment and driven by an engine (not shown) through a not-shown belt. The variable capacity compressor 1 includes a suction chamber 2, a discharge chamber 3 and a crank chamber 4. The suction chamber 2 is supplied with gas-phase refrigerant of low temperature and low pressure passing through the evaporator 73. The discharge chamber 3 is compressed by a piston (not shown) to feed the gas-phase refrigerant of high temperature and high pressure to the condenser 71. The crank chamber 4 is always communicated with the suction chamber 2 to allow the refrigerant in the suction chamber 2 to enter into the crank chamber 4. When the variable capacity compressor 1 stops its operation, the pressure in the crank chamber 4 becomes equal to that in the suction chamber 2.

The crank chamber 4 is communicated with the discharge chamber 3 through a control valve 10. When the control valve 10 opens, the crank chamber 4 is communicated with the discharge chamber 3, allowing the refrigerant in the discharge chamber 3 to enter into the crank chamber 4. When the control valve 10 closes, the discharge chamber 3 and the crank chamber 4 are insulated from each other, while the crank chamber 4 is communicated with the suction chamber 2. Thus, as a pressure difference between the suction chamber 2 and the crank chamber 4 is reduced, the stroke of the piston gets longer to increase a compressive capacity of the compressor 1.

On the other hand, when the control valve 10 opens so that the refrigerant on the discharge side enters into the crank chamber 4, the stroke of the piston gets shorter due to a pressure difference between the pressure in the crank chamber 4 and the pressure in the suction chamber 2 (i.e. former pressure>latter pressure), so that the compressive capacity of the compressor 1 is decreased.

The control valve 10 is controlled by a valve control signal composed of a compression-ratio control signal in the form of PWM (Pulse Width Modulation) outputted from a valve control unit 50 and a flow-rate control signal outputted on a basis of a detection result of a flow meter 60. The workload of the variable capacity compressor 1 is controlled since the control valve control unit 50 changes a duty ratio of the control valve 10 due to PWM control method to adjust the pressure in the crank chamber 4 and change the compressive capacity of the compressor 1.

The valve control unit 50 comprises a central processing unit (CPU) 51 for various calculations, a memory 52 for storing various program and data, such as read only memory (ROM) and random access memory (RAM), an input port (I/P) 53 for inputting an in-cabin target temperature and various air conditioning parameters etc., an output port (O/P) 54 and a bus 55 for interconnecting these elements with each other. The valve control unit 50 further includes a compression-ratio signal generating circuit 56 for generating the compression-ratio control signal. The compression-ratio signal generating circuit 56 is driven by a drive signal outputted from the output port 54. In connection, the compression-ratio signal generating circuit 56 is electrically connected to a signal processing unit 90 mentioned later.

For the air conditioning parameters, an air conditioner switch 61, a “just behind the evaporator” temperature sensor 62, a room-temperature sensor 63, and an atmosphere-temperature sensor 64, an insolation sensor 65 are connected to the input port 53. Further, the in-cabin target temperature is also inputted to the input port 53.

As shown in FIG. 2, the control valve 10 comprises a suction-pressure detecting section 12a arranged on one side of a body casing 11 and communicated with the suction chamber 2 to detect a suction-side pressure, a discharge-pressure detecting section 14a arranged at the center of the body casing 11 and communicated with the discharge chamber 3 to detect a discharge-side pressure and a driving section 30 arranged on the other side of the body casing 11 to drive a valve body 21, mainly.

Formed in the body casing 11 are a suction pressure chamber 12 that communicates with the suction chamber 2 through the suction-pressure detecting section 12a on one side of the casing 11, a discharge pressure chamber 14 that communicates with the discharge chamber 3 through the discharge-pressure detecting section 14a, a pressure regulating passage 15 that communicates the discharge pressure chamber 14 with the crank chamber 4, an auxiliary suction pressure chamber 13 comparted from the discharge pressure chamber 14 by a later-mentioned compartment section 22, a driver accommodating chamber 17 where the driving section 30 is arranged on the other side of the casing 11 and a suction pressure chamber communicating passage 13a that communicates the suction pressure chamber 12 with the auxiliary suction pressure chamber 13. On a shaft 20, there are successively and integrally formed a bellows 40, a valve body 21, the compartment section 22 and an armature 33 in this order from one side of the shaft 20 to the other side.

The bellows 40 is formed by a flexible bellows member 41 and a pressure regulating spring 42 disposed in the bellow member 41 to have a predetermined sprint constant. The bellows 40 is arranged in the suction pressure chamber 12. The bellows 40 has its one side formed integrally with one end of the shaft 20 and the other side fixed on an inner wall of the suction pressure chamber 12. The bellows 40 is sensitive against an inside pressure of the suction pressure chamber 12. Thus, when the suction-side pressure is smaller than a predetermined pressure, the pressure regulating spring 42 slides the shaft 20 to open a valve part 16.

The valve body 21 constitutes the valve part 16 together with the pressure regulating passage 15. With slide movements of the shaft 20, the valve body 21 opens and closes the pressure regulating passage 15.

The compartment section 22 is formed integrally with the shaft 20 and arranged slidably. The compartment section 22 divides off the discharge pressure chamber 14 from the auxiliary suction pressure chamber 13 in a sealed condition while changing both capacities of the auxiliary suction pressure chamber 13 and the discharge pressure chamber 14 by the compartment section's sliding.

The armature 33 is made of magnetic material and formed integrally with the other end of the shaft 20 to constitute the driving section 30.

The driving section 30 is arranged in the driver accommodating chamber 17 on the other side of the body casing 11. The driving section 30 is formed by a solenoid coil 31 arranged in the chamber 17, a yoke 32 arranged on an inner circumference of the solenoid coil 31 and made of magnetic material and the armature 33. In operation, the solenoid coil 31 is excited by the valve control signals composed of the compression-ratio control signal outputted from the control valve control unit 50 and the flow-rate control signal outputted on the basis of the detection result of the flow meter 60 to absorb the armature 30. As a result, the shaft 20 is slid to open the valve part 16.

A differential pressure setting spring 43 is interposed between the compartment section 22 in the auxiliary suction pressure chamber 13 and the yoke 32. When a differential pressure between the suction pressure and the discharge pressure exceeds a predetermined value, the shaft 20 is slid by the discharge pressure while the differential pressure setting spring 43 is shrinking, so that the valve part 16 is opened.

As shown in FIG. 2, the flow meter 60 of this embodiment is interposed in a pipe 66 connecting the evaporator 73 with the variable capacity condenser 1. The flow meter 60 is electrically connected to the signal processing unit 90. Further, an engine control unit 80 (as an outside control unit) is also electrically connected to the signal processing unit 90. In operation, various parameters representing an actual driving condition of the vehicle are inputted to the engine control unit 80. On detection of the driving condition of the vehicle, the engine control unit 80 controls the operation of the engine. Additionally, when the so-detected driving condition satisfies a predetermined condition mentioned later, the engine control unit 80 outputs a demand (signal) of reducing a driving torque of the variable capacity compressor to the signal processing unit 90.

As shown in FIG. 3, the flow meter 60 of this embodiment is a so-called heater type flow meter. This flow meter 60 is equipped with a constant temperature-difference control circuit (not shown) for maintaining temperature of a heat wire 67 higher than temperature of the suction refrigerant by constant temperature. This constant temperature-difference control circuit has a function to maintain the heat wire 67 under a constant temperature-difference condition. That is, if the heat wire 67 is cooled down by the suction refrigerant, the constant temperature-difference control circuit operates to increase a supply current for the heat wire 67 in order to maintain it under the constant temperature-difference condition. In such a case, simultaneously, the constant temperature-difference control circuit outputs a voltage signal corresponding to the above supply current for the heat wire 67, as a measured flow rate value. According to the embodiment, since a heater type flow meter constitutes the flow meter 60, it is possible to acquire an output corresponding to a mass flow rate directly. Therefore, there is no influence of refrigerant density (temperature, pressure) on measured values, allowing dispensation with a correction. In FIG. 3, reference numeral 68 denotes a temperature compensating resistance that is paralleled with the heat wire 67 in order to effect the above-mentioned function of the flow meter 60.

[Control Process for Control Valve]

(1^st. Embodiment)

Referring to FIG. 4, we now describe a case of controlling the refrigerant flow rate by reducing voltage of the control signal for the driving section 30 through the flow rate control signal.

First, when the air conditioner switch 61 is tuned on to operate the air conditioner for a vehicle, the valve control unit 50 changes a duty ratio of the valve control signal for the control valve 10 in accordance with the in-cabin target temperature and the air conditioning parameters detected by a variety of sensors (e.g. the “just behind the evaporator” temperature sensor 62, the room-temperature sensor 63, the atmosphere-temperature sensor 64, the insolation sensor 65) in order to make a room temperature (in-cabin temperature) the target temperature as soon as possible.

Suppose, during normal operating of the air conditioner, the driving condition of the engine changes to a predetermined condition where it is required to reduce a driving torque of the compressor 1 in view of maintaining the drivability of the vehicle. For example, there may be cited, a change from a normal traveling to acceleration; idling; some changes in engine's combustion mode (e.g. direct injection gasoline lo engine, lean burn engine).

In this case, the engine control unit 80 outputs a demand (signal) of immediately reducing the present driving torque of the variable capacity compressor 1 to the signal processing unit 90. Inputting the above demand signal, the signal processing unit 90 modulates the flow-rate control signal and produces a valve control signal whose voltage is lower than that of the valve control signal in the normal driving state (See FIG. 4). Next, the so-produced valve control signal is transmitted from the signal processing unit 90 to the driving section 30 of the valve 10 of the variable capacity compressor 1.

In this way, when the voltage of the valve control signal inputted to the driving section 30 is reduced, the capacity of the variable capacity compressor 1 becomes smaller. As a result, the flow rate of the refrigerant on circulation is reduced.

Here, it is noted that the driving torque of the variable capacity compressor 1 is determined from a following arithmetic expression (1) for calculating a compression energy (power) P0 and a following relational expression (2) between the energy (power) P0 and the driving torque with the use of parameters of suction-side pressure Ps, discharge-side pressure Pd and flow rate of the refrigerant. Thus, by restraining a maximum flow rate of the refrigerant, it is possible to restrain the upper limit of the driving torque of the compressor 1.

P0=(Ps·V/6120)·{n/(n−1)}·{(Pd/Ps)ˆ((n−1)/n)−1}·(ηv/ηad) (1)

where, V denotes specific volume ×compressor discharge rate;

n denotes polytropic index;

ηv denotes volumetric efficiency; and

ηad denotes compression efficiency.

P0=Driving Torque×Number of Revolutions (2)

With the above-mentioned constitution and control method, if the engine control unit 80 requires the variable capacity compressor 1 to restrain the driving torque, it is carried out to restrain the flow rate of the refrigerant so as not to exceed a predetermined driving torque through the flow-rate control signal. Consequently, with the restriction in the flow rate of the refrigerant (or refrigerant flow rate) to be supplied into the variable capacity compressor 1, it is possible to restrain the driving torque essential to drive the compressor 1 to a value less than the driving torque required by the engine control unit 80.

Additionally, according to the embodiment, since a parameter to be changed in accordance with the requirement by the engine control unit 80 is not the compression-ratio control signal but the flow-rate control signal, it is possible to prevent occurrence of abnormal noise because the refrigerant flow rate in the pipe does not change abruptly.

Further, since the refrigerant flow rate is detected by the flow meter 60 and the detection result is reflected on the flow-rate control signal, it is possible to restrain the driving torque less than a value required by the control unit 80 with higher accuracy.

Meanwhile, under a situation that a signal to reduce the driving torque is generated from the engine control unit 80 for a long time, there arises a possibility that the valve control unit 50 judges that the cooling capability of the compressor 1 runs short since the compressor control apparatus of the invention is constructed so as to restrain the refrigerant flow rate without going through the valve control unit 50. In such a case, the valve control unit 50 would intend to increase the refrigerant flow rate. Therefore, in order to avoid an occurrence of such a misjudgment, it may be carried out to allow the engine control unit 80 to output a command of fixing the control signal to the valve control unit 50.

(2^nd. Embodiment)

According to the second embodiment, as shown in FIG. 5, the flow rate of the refrigerant is restrained by reducing the pulse width of the control signal outputted to the driving section 30 through the flow-rate control signal.

The operation of the second embodiment will be described below.

First of all, it is noted that similarly to the first embodiment, the valve control unit 50 changes a duty ratio of the control signal impressed on the control valve 10 in view of establishing a target temperature in terms of the in-cabin temperature.

Suppose again, during normal operating of the air conditioner, the driving condition of the engine changes to a predetermined condition where it is required to reduce a driving torque of the compressor 1 in view of maintaining the drivability of the vehicle.

In this case, the engine control unit 80 outputs a demand (signal) of immediately reducing the present driving torque of the variable capacity compressor 1 to the signal processing unit 90. Inputting the above demand signal, the signal processing unit 90 modulates the flow-rate control signal and produces a valve control signal whose pulse width is smaller than that of the valve control signal in the normal driving state (see FIG. 5). Next, the so-produced valve control signal is transmitted 15 from the signal processing unit 90 to the driving section 30 of the valve 10 of the variable capacity compressor 1.

Note that the flow-rate control signal of this embodiment is established so as to have a frequency more than ten times of the frequency of the valve control signal.

In this way, according to the embodiment, when the demand of restraining the driving torque engine is generated from the engine control unit 80, the flow rate of the refrigerant is restrained by the flow-rate control signal in a manner that the driving torque of the compressor 1 does not exceed a predetermined value. Consequently, since the flow rate of the refrigerant to be supplied into the compressor 1 is suppressed, it is possible to reduce the driving torque necessary to drive the variable capacity compressor 1 less than a value required by the control unit 80.

Additionally, also in the second embodiment, since a parameter to be changed in accordance with the requirement by the engine control unit 80 is not the compression-ratio control signal but the flow-rate control signal, it is possible to prevent occurrence of abnormal noise because the refrigerant flow rate in the pipe does not change abruptly.

Finally, it will be understood by those skilled in the art that the foregoing descriptions are nothing but three embodiments of the disclosed variable capacity compressor control apparatus and therefore, various changes and modifications may be made within the scope of claims.

Claims

1. A variable capacity compressor control apparatus for a vehicle, comprising: a variable capacity compressor equipped with a control valve capable of changing a discharge volume of a refrigerant for an air conditioner therefrom; a valve control unit electrically connected to the control valve to determine an opening/closing duty ratio thereof on a basis of a preset in-cabin target temperature and various air conditioning parameters and output a compression-ratio control signal for driving the control valve with the opening/closing duty ratio determined; a flow meter arranged in a refrigerant pipe connected to the variable capacity compressor to detect a flow rate of the refrigerant for the air conditioner flowing into the variable capacity compressor; a signal processing unit electrically connected to the flow meter and the valve control unit to generate a flow-rate control signal based on the present flow rate of the refrigerant detected by the flow meter, the signal processing unit inputting the compression-ratio control signal outputted from the valve control unit and outputting a valve control signal formed by the flow-rate control signal and the compression-ratio control signal to the control valve; and an outside control unit electrically connected to the signal processing unit to input a driving condition of the vehicle and output a demand of reducing a driving torque of the variable capacity compressor to the signal processing unit when the present driving condition satisfies a predetermined condition, wherein when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal, thereby changing the valve control signal.
2. The variable capacity compressor control apparatus of claim 1, wherein the compression-ratio control signal is a signal in the form of PWM control.
3. The variable capacity compressor control apparatus of claim 1, wherein the control valve of the variable capacity compressor comprises: a suction pressure detecting section communicated with a suction chamber of the variable capacity compressor to detect a suction-side pressure Ps of refrigerant sucked into the variable capacity compressor; a discharge pressure detecting section communicated with a discharge chamber of the variable capacity compressor to detect a discharge-side pressure Pd of the refrigerant discharged from the variable capacity compressor; a crank-chamber communicating section communicated with a crank chamber of the variable capacity compressor; a pressure regulating passage formed to communicate the crank-chamber communicating section with the discharge pressure detecting section; a valve section having a valve body movably arranged in the pressure regulating passage and configured to open and close the pressure regulating passage with movements of the valve body in the pressure regulating passage; a pressure regulating spring which is responsive of the suction-side pressure Ps thereby to open and close the valve section; a suction-pressure-chamber communicating passage formed to communicate the suction pressure detecting section with the discharge pressure detecting section; and a driving section electrically connected to the signal processing section to actuate the valve body of the valve section thereby opening and closing the pressure regulating passage.
4. The variable capacity compressor control apparatus of claim 1, wherein the outside control unit is an engine control unit for controlling a driving source of the vehicle.
5. The variable capacity compressor control apparatus of claim 1, wherein when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal so as to reduce a voltage of the valve control signal.
6. The variable capacity compressor control apparatus of claim 1, wherein when the demand of reducing the driving torque is outputted from the outside control unit, the signal processing unit modulates the flow-rate control signal so as to reduce a pulse width of the valve control signal.

Priority Claims (1)

Number	Date	Country	Kind
P2005-207872	Jul 2005	JP	national

Variable capacity compressor control apparatus for vehicle

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CPC

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Priority Claims (1)