Automotive air conditioning system having refrigerant compressor with externally controlled variable displacement mechanism

Abstract: The present invention discloses an automotive air conditioning system for conditioning air in an automobile passenger compartment. The automotive air conditioning system includes a compressor (100) with an externally controlled variable displacement mechanism, a control apparatus (10) for controlling operation of the compressor (100), an evaporator forming a part of the automotive air conditioning system, and an electromagnetic clutch (101) associated with the compressor (100) so as to intermittently transmit a power of an engine of an automobile to the compressor (100). The control apparatus (10) controls the operation of the compressor (100) in order to quickly adequately compensate a reduction of an accelerating performance of the automobile without sacrificing an adequate air conditioning in the automobile passenger compartment.

Description: The present invention relates to an automotive air conditioning system, and more particularly, to an automotive air conditioning system which includes a refrigerant compressor with an externally controlled variable displacement mechanism. Generally, in an automotive air conditioning system, a refrigerant compressor is intermittently driven by an automobile engine through an electromagnetic clutch which is associated with the compressor in response to changes in the demand for air conditioning in an automobile passenger compartment so that temperature of air in the automobile passenger compartment is maintained at the required temperature. According to Japanese Patent Application Publication No. 55-148614, when the amount of demand for acceleration of the automobile is equal to or greater than one certain value, operation of the refrigerant compressor is stopped by means of deenergization of the electromagnetic clutch so that the power outputted from the automobile engine is effectively used for driving the automobile. However, this manner of stopping operation of the refrigerant compressor causes an inadequate air conditioning in the automobile passenger compartment because that no air conditioning is carried out in the automobile passenger compartment due to a stop of operation of the refrigerant compressor. In order to resolve this drawback, Japanese Patent Application publication No. 57-195884 discloses an automobile air conditioning system which includes a refrigerant compressor with an externally controlled variable displacement mechanism. According to this Japanese Patent Application Publication, when the amount of demand for acceleration of the automobile is equal to or greater than one certain value, a capacity of the refrigerant compressor is forcibly reduced to the minimum displacement so as to produce a surplus power which is shared with driving the automobile. However, when the capacity of the refrigerant compressor is forcibly reduced to the minimum displacement in the smaller displacement stage, a negligible amount of the surplus power is produced while the air conditioning in the automobile passenger compartment is inadequately carried out. Therefore, when the amount of demand for acceleration of the automobile is equal to or greater than one certain value in the smaller compressor displacement stage, the capacity of the compressor is merely uselessly controlled. Furthermore, as shown in Figure 1, when the capacity of the refrigerant compressor is forcibly reduced to the minimum displacement in the larger displacement stage, a sufficient amount of the surplus power can not be instantly obtained in comparison with the manner of stopping operation of the compressor by means of deenergization of the electromagnetic clutch. Therefore, when the amount of demand for acceleration of the automobile is equal to or greater than one certain value in the larger compressor displacement stage, a reduction of the accelerating performance of the automobile due to operation of the compressor is not quickly sufficiently compensated. US-A-5022232 discloses an automotive air conditioning system including a compressor with a variable displacement mechanism, an evaporator forming a part of the automotive air conditioning system, controlling means for controlling operation of the compressor, and a transmitting means for intermittently transmitting power for moving an automobile to the compressor, the controlling means including sensing means for sensing a heat load on the evaporator, sensing means for sensing an amount of demand for acceleration of the automobile, sensing means for sensing an amount of torque acting on a drive shaft of the compressor; judging means for judging whether the amount of the torque acting on the drive shaft of the compressor is smaller than a first predetermined amount, greater than a second predetermined amount which is greater than the first predetermined amount, or equal to or greater than the first predetermined amount but equal to or smaller than the second predetermined amount; operating means for selectively operating the transmitting means and the variable displacement mechanism in response to a judgement of the judging means. Accordingly, it is an object of the present invention to provide an automotive air conditioning system which can quickly and adequately compensate a reduction of the accelerating performance of an automobile without sacrificing an adequate air conditioning in an automobile passenger compartment during operation of the automotive air conditioning system. According to a first aspect of the present invention an automotive air conditioning system including a compressor with a variable displacement mechanism, an evaporator forming a part of the automotive air conditioning system, controlling means for controlling operation of the compressor, and a transmitting means for intermittently transmitting power for moving an automobile to the compressor, the controlling means including a sensor for sensing a heat load on the evaporator; a switching device for sensing an amount of demand for acceleration of the automobile; first control unit for determining an amount of torque acting on a drive shaft of the compressor; a second control unit for judging whether the amount of demand for acceleration of the automobile is equal to or greater than a predetermined amount, and for judging whether the amount of the torque acting on the drive shaft of the compressor is smaller than a first predetermined amount, greater than a second predetermined amount which is greater than the first predetermined amount, or equal to or greater than the first predetermined amount but equal to or smaller than the second predetermined amount; a third control unit for selectively operating the transmitting means and the variable displacement mechanism in response to a judgement of the second control unit, the third control unit operating the variable displacement mechanism so as to vary a capacity of the compressor from the minimum to the maximum value thereof in response to changes in the heat load on the evaporator when the amount of demand for acceleration of the automobile is smaller than the predetermined amount, or both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is smaller than the first predetermined amount; the third control unit operating the transmitting means so as not to transmit the power for moving the automobile to the compressor both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is greater than the second predetermined amount; the third control unit further operating the variable displacement mechanism so as to forcibly reduce the capacity of the compressor to the minimum value thereof both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is equal to or greater than the first predetermined amount but is equal to or smaller than the second predetermined amount. According to a second aspect of the present invention an automotive air conditioning system including a compressor with a variable displacement mechanism, an evaporator forming a part of the automotive air conditioning system, controlling means for controlling operation of the compressor, and a transmitting means for intermittently transmitting power for moving an automobile to the compressor, the controlling means including a sensor for sensing a heat load on the evaporator; a switching device for sensing an amount of demand for acceleration of the automobile; a second sensor for detecting the temperature of air outside the automobile; second control unit for judging whether the amount of demand for acceleration of the automobile is equal to or greater than a predetermined amount, and for judging whether the temperature of air outside the automobile is smaller than a first predetermined amount, greater than a second predetermined amount which is greater than the first predetermined amount, or equal to or greater than the first predetermined amount but equal to or smaller than the second predetermined amount; a third control unit for selectively operating the transmitting means and the variable displacement mechanism in response to a judgement of the second control unit, the third control unit operating the variable displacement mechanism so as to vary a capacity of the compressor from the minimum to the maximum value thereof in response to changes in the heat load on the evaporator when the amount of demand for acceleration of the automobile is smaller than the predetermined amount, or both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is smaller than the first predetermined amount; the third control unit operating the transmitting means so as not to transmit the power for moving the automobile to the compressor both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is greater than the second predetermined amount; the third operating unit further operating the variable displacement mechanism so as to forcibly reduce the capacity of the compressor to the minimum value thereof both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is equal to or greater than the first predetermined amount but is equal to or smaller than the second predetermined amount. In the accompanying drawings: Figure 1 is a graph illustrating a manner of compensation for a reduction of the accelerating performance of an automobile in accordance with one prior art example of an automobile air conditioning system. Figure 2 is a partial schematic block diagram of an automotive air conditioning system in accordance with a first embodiment of the present invention. Figure 3 is a graph illustrating relationships which are obtained by an operational manner of a compressor used in the automotive air conditioning system shown in Figure 2. Figure 4 is a flow chart of an operational manner of a control apparatus used in the automotive air conditioning system shown in Figure 2. Figure 5 is a time chart of an operational manner of a control apparatus used in the automotive air conditioning system shown in Figure 2. Figure 6 is a partial schematic block diagram of an automotive air conditioning system in accordance with a second embodiment of the present invention. Figure 7 a graph illustrating a relationship obtained by an operational manner of the compressor used in the automotive air conditioning systems shown in Figures 2 and 6. Figure 8 is a flow chart of an operational manner of a control apparatus used in the automotive air conditioning system shown in Figure 6. Figure 9 is a time chart of an operational manner of a control apparatus used in the automotive air conditioning system shown in Figure 6. Figure 2 illustrates a partial schematic block diagram of an automotive air conditioning system in accordance with a first embodiment of the present invention. With reference to Figure 2, the automotive air conditioning system includes refrigerant compressor 100 having a variable displacement mechanism which has already disclosed in EP-A1-486257, and control apparatus 10 which controls operation of compressor 100. As disclosed in EP-A1-486257, the variable displacement mechanism of compressor 100 comprises an externally controlled valve device having a solenoid coil. The variable displacement mechanism of compressor 100 has already described in detail in EP-A1-486257 so that a further explanation thereof is omitted. Control apparatus 10 includes first, second and third control units 11, 12 and 13. Thermo-sensor 14 detects temperature T of air immediately leaving from an evaporator (not shown) which forms a part of the automotive air conditioning system, and is-connected to first control unit 11 through a wire. First control unit 11 is connected to both second and third control units 12 and 13 through the respective wires. Second control unit 12 is connected to third control unit 13 through a wire. Third control unit 13 is connected to the solenoid coil of the externally controlled valve device of the variable displacement mechanism of compressor 100 through a wire. Third control unit 13 is further connected through another wire to an electromagnetic coil of electromagnetic clutch 101 which is associated with compressor 100 so as to intermittently transmit the rotational motion of an external power source, such as an automobile engine to a drive shaft of compressor 100. Thermo-sensor 14 generates first control signal S1 which represents temperature T of air immediately leaving from the evaporator. First control signal S1 is sent to first control unit 11 from thermo-sensor 14 through the wire so as to be processed therein as follows. First control unit 11 operates as a proportional-plus-integral controller so as to generate a proportional-plus-integral control signal as second control signal S2 which will be described in detail later. Second control signal S2 is sent-to both second and third control units 12 and 13 from first control unit 11 through the respective wires. Third control unit 13 operates to process second control signal S2 so as to output electric current I, of which value varies from Imin (0 ampere) to Imax (1.0 ampere) in response to changes in value of second control signal S2, to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. With reference to Figure 3 illustrating relationships which are obtained by an operational manner of compressor 100, when the externally controlled valve device of the variable displacement mechanism receives electric current I of which value is Imax, the control point of pressure in the compressor suction chamber is maintained at the maximum value so that the compressor operates with the minimum displacement. Therefore, the torque which acts on the compressor drive shaft is maintained at the minimum value. On the other hand, when the externally controlled valve device of the variable displacement mechanism receives electric current I of which value is Imin, the control point of pressure in the compressor suction chamber is maintained at the minimum value so that the compressor operates with the maximum displacement. Therefore, the torque which acts on the compressor drive shaft is maintained at the maximum value. Furthermore, the control point of pressure in the compressor suction chamber varies from the maximum to minimum value thereof in response to the changes in electric current I as indicated by a solid line in Figure 3. The torque acting on the compressor drive shaft varies from the maximum to minimum value thereof in response to changes in electric current I as indicated by a dashed line in figure 3. Accordingly the capacity of compressor 100 can be controlled by changing the value of electric current I so that temperature T of air immediately leaving from the evaporator is maintained at the set temperature Tset. First control unit 11 further operates as follow. When temperature T of air immediately leaving from the evaporator falls to or below a first predetermined value Ta at which a frost is begun to form at an exterior surface of the evaporator, first control signal S1 is processed in first control unit 11 to generate third control signal S3, which is sent to third control unit 13 to be processed therein so as to deenergize the electromagnetic coil of electromagnetic clutch 101. Therefore, operation of compressor 100 is stopped in order to prevent frost forming at the exterior surface of the evaporator. Once third control signal S3 is generated in first control unit 11, deenergization of the electromagnetic coil of electromagnetic clutch 101 is maintained until temperature T of air immediately leaving from the evaporator rises to or above second predetermined value Tb which is greater than first predetermined value Ta. When temperature T of air immediately leaving from the evaporator rises above second predetermined value Tb, first control signal S1 is processed in first control unit 11 to generate fourth control signal S4, which is sent to third control unit 13 to be processed therein so as to energize the electromagnetic coil of electromagnetic clutch 101. Therefore, operation of compressor 100 is restarted. Accordingly, the electromagnetic coil of electromagnetic clutch 101 is energized and deenergized by the respective third and fourth control signals S4 and S3 generated at third control unit 13. That is, the operation of compressor 100 is stopped and restarted by the respective third and fourth control signals S3 and S4 generated at third control unit 13. Switching device 15 is associated with an acceleration pedal of an automobile, and is connected to second control unit 12 through a wire. Switching device 15 is turned on so as to start operation of second control unit 12 when the amount of demand for acceleration of an automobile is equal to or greater than one certain value, that is, when the stepping amount of the acceleration pedal is equal to or greater than one certain stepping amount. On the other hand, switching device 15 is turned off so as to stop operation of second control unit 12 when the amount of demand for acceleration of the automobile is less than the above-mentioned one certain value, that is, when the stepping amount of the acceleration pedal is less than the above-mentioned one certain stepping amount. Accordingly, second control unit 12 operates only when the amount of demand for acceleration of the automobile is equal to or greater than one certain value. Furthermore, operation of second control unit 12 overrides operation of first control unit 11. Furthermore, switching device 15 can be a pressure switch associated with an intake-manifold used for the automobile engine, or a switching device associated with a throttling device used for the automobile engine. Second control unit 12 operates to judge whether compressor 100 operates with a larger, an intermediate or a smaller displacement by means of processing second control signal S2 therein. With reference to Figure 3 again, operation of second control unit 12 is as follows. When second control unit 12 judges that compressor 100 operates with the larger displacement, i.e., the solenoid coil of the externally controlled valve device of the variable displacement mechanism receives electric current I of which value is equal to or greater than Imin but is smaller than one predetermined value Ia, second control unit 12 generates fifth control signal S5. Fifth control signal S5 is sent to third control unit 13 from second control unit 12, and is processed therein so as to deenergize the electromagnetic coil of electromagnetic clutch 101. When second control unit 12 judges that compressor 100 operates with the intermediate displacement, i.e., the solenoid coil of the externally controlled valve device of the variable displacement mechanism receives electric current I of which value is equal to or greater than one predetermined value Ia but is equal to or smaller than another predetermined value Ib which is greater than one predetermined value Ia, second control unit 12 generates sixth control signal S6. Sixth control signal S6 is sent to third control unit 13 from second control unit 12, and is processed therein so as to output electric current I of which value is Imax to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. Therefore, the capacity of compressor 100 is forcibly reduced to the minimum displacement. When second control unit 12 judges that compressor 100 operates with the smaller displacement, i.e., the solenoid coil of the externally controlled valve device of the variable displacement mechanism receives electric current I of which value is greater than another predetermined value Ib but is equal to or smaller than Imax, second control unit 12 generates no control signal. Therefore, the operation of control apparatus 10 is substantially left to only operation of first control unit 11. With reference to Figure 4 in addition to Figures 2 and 3, an operational manner of control apparatus 10 is described in detail below. In Figure 4, symbol "n" and appended symbol "n" indicate the number of times of the operation of control apparatus 10 after the automotive air conditioning system is turned on. When the automotive air conditioning system is turned on at step 201, a counter (not shown) which is associated with control apparatus 10 is reset at step 202, and the electromagnetic coil of electromagnetic clutch 101 is energized at step 203 sequentially. Step 203 sequentially proceeds to step 204, at which whether the number of the counter is zero is judged. If the number of the counter is zero, that is, if the first operation of control apparatus 10 is not completed after the automotive air conditioning system is turned on, step 204 proceeds to step 205. On the other hand, if the number of the counter is not zero, that is, if at least first operation of control apparatus 10 has been completed after the automotive air conditioning system is turned on, step 204 proceeds to step 301. At step 205, whether temperature Tn of air immediately leaving from the evaporator is higher than first predetermined value Ta is judged. If temperature Tn is higher than Ta, step 205 proceeds to step 208. On the other hand, if temperature Tn is equal to or below Ta, step 205 proceeds to step 206. It step 206, the electromagnetic coil of electromagnetic clutch 101 is deenergized in order to avoid frost forming at the-exterior surface of the evaporator, and step 206 sequentially proceeds to step 207. At step 207, whether temperature Tn is equal to or higher than second predetermined value Tb is judged. If temperature Tn is equal to or higher than Tb, step 207 proceeds to step 203. On the other hand, if temperature Tn is below Tb, the deenergization of the electromagnetic coil of electromagnetic coil 101 is maintained. At step 208, whether temperature Tn of air immediately leaving from the evaporator is higher than third predetermined value Tc is judged. If temperature Tn is higher than Tc, step 208 proceeds to step 210. On the other hand, if temperature Tn is equal to or below Tc, step 208 proceeds to step 209. At step 209, second control signal S2 which is shown by, for convenience, a form of electric current I which is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism is generated in accordance with the following formula. In = In-1 + K{(ΔTn - ΔTn-1 ) + A·ΔTn} In formula (1), ΔTn is (Tn - Tset), and K and A are the different constant values, respectively. Furthermore, in the first operation of control apparatus 10, Imin and (Tc - Tset) are substituted for In-1 and ΔTn-1 in formula (1), respectively. Step 209 sequentially proceeds to step 211 in which whether electric current In is greater than Imax is judged. If electric current In is greater than electric current Imax, step 211 proceeds to step 212. On the other hand, if electric current In is equal to or smaller than electric current Imax, step 211 proceeds to step 213. At step 212, electric current Imax is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. At step 213, electric current In is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. At step 210, electric current Imin is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. At step 301 whether switching device 15 is turned on is judged. If switching device 15 is turned on, step 301 proceeds to step 302. On the other hand, if switching device 15 is not turned on, step 301 proceeds to step 205. At step 302, whether electric current In is greater than second predetermined value Ib is judged. If electric current In is greater than second predetermined value Ib, step 302 also proceeds to step 205. On the other hand, if electric current In is equal to or smaller than second predetermined value Ib, step 302 proceeds to step 303. At step 303, a first and second timers start to run. Sequentially, step 303 proceeds to step 304 at which whether electric current In is greater than first predetermined value Ia is Judged. If electric current In is equal to or greater than first predetermined value Ia, step 304 proceeds to step 306. On the other hand, if electric current In is smaller than first predetermined value Ia, step 304 proceeds to step 305. At step 306, electric current Imax is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. Step 306 sequentially proceeds to step 307 at which whether the first timer runs a first predetermined time t1 is judged. If the first timer does not run the first predetermined time t1, electric current Imax is still outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. On the other hand, if the first timer runs the first predetermined time t1, step 307 proceeds to step 310. At step 305, the electromagnetic coil of electromagnetic clutch 101 is deenergized. Step 305 sequentially proceeds to step 308 at which whether the first timer runs first predetermined time t1 is judged. If the first timer does not run the first predetermined time t1, deenergization of the electromagnetic coil of electromagnetic clutch 101 is maintained. On the other hand, if the first timer runs the first predetermined time t1, step 308 proceeds to step 309 at which the electromagnetic coil of electromagnetic clutch 101 is energized again. Step 309 sequentially proceeds to step 310 at which electric current In is outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. Step 310 sequentially proceeds to step 311 at which the first timer is reset. Step 311 sequentially proceeds to step 312 at which whether the second timer runs a second predetermined time t2 which Is longer than the first predetermined time t1 is judged. If the second timer does not run the second predetermined time t2, electric current In is still outputted from third control unit 13 to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. On the other hand, if the second timer runs the second predetermined time t2, step 312 proceeds to step 313 at which the second timer in reset. The respective steps 212, 213, 210 and 313 proceeds to step 214 at which the number of counter is increased by one as the operation of control apparatus 10 is completed once. Step 214 sequentially proceeds to step 215 at which the automotive air conditioning system is required to be turned off is judged. If the automotive air conditioning system is required to be turned off, the automotive air conditioning system is turned off so that the operation thereof is terminated. On the other hand, if the automotive air conditioning system is not required to be turned off, step 215 returns to step 204 so that the operation of control apparatus 10 is repeated. As described above, each of the steps from step 205 to the respective steps 212, 213 and 210 is carried out in accordance with the operation of first control unit 11. Furthermore, each of the steps from step 302 to step 313 is carried out in accordance with the operation of second control unit 12. Figure 5 is a time chart illustrating the different operational stages of control apparatus 10. With reference to Figure 5 in addition to Figure 4, each of the steps from step 302 to step 313 via steps 306 and 307 in Figure 4 is carried out in stages (a) and (b). The difference between stage (a) with (b) is the length of ON-time of switching device 15. In stage (a), the length ta of ON-time of switching device 15 is shorter than second predetermined time t2. Therefore, each of the steps from step 302 to step 313 via steps 306 and 307 in Figure 4 is carried out only once in stage (a). On the other hand, in stage (b), the length tb of ON-time of switching device 15 is slightly longer than second predetermined time t2. Therefore, each of the steps from step 302 to step 313 via steps 306 and 307 in Figure 4 is carried out twice in stage (b). Furthermore, each of the steps from step 302 to step 313 via steps 305, 308 and 309 in Figure 4 is carried out in stages (c) and (d). The difference between stage (c) with (d) is the length of ON-time of switching device 15. In stage (c), the length tc of ON-time of switching device 15 is shorter than second predetermined time t2. Therefore, each of the steps from step 302 to step 313 via steps 305, 308 and 309 in Figure 4 is carried out only once in stage (c). On the other hand, in stage (d), the length td of ON-time of switching device 15 is slightly longer than second predetermined time t2. Therefore, each of the steps from step 302 to step 313 via steps 305, 308 and 309 in Figure 4 is carried out twice in stage (d). As described above, the automotive air conditioning system according to the first embodiment of the present invention can quickly and adequately compensate a reduction of the accelerating performance of the automobile without sacrificing an adequate air conditioning in the automobile passenger compartment during operation of the automotive air conditioning system. Figure 6 illustrates a partial schematic block diagram of an automotive air conditioning system in accordance with a second embodiment of the present invention. In Figure 6, the same numerals are used to denote the corresponding elements shown in Figure 2 so that an explanation thereof is omitted. In the second embodiment, control apparatus 10′ includes second control unit 12′ which is connected to both switching device 15 and auxiliary thermo-sensor 16 through the respective wires. Auxiliary thermo-sensor 16 detects temperature Ts of an automobile outside air, and generates seventh control signal S7 which represents temperature Ts of the automobile outside air. Seventh control signal S7 is sent to second control unit 12′ from auxiliary thermo-sensor 16 through the wire so as to be processed therein. In the second embodiment, a relationship which is obtained by an operational manner of compressor 100 and is illustrated in Figure 7 is utilized in the operation of control apparatus 10′. As illustrated in Figure 7, when temperature Ts of an automobile outside air is lower than first predetermined value Ts1, an amount of the torque acting on the compressor drive shaft is small. On the other hand, when temperature Ts of the automobile outside air is higher than second predetermined value Ts2, the amount of the torque acting on the compressor drive shaft is large. Furthermore, when temperature Ts of the automobile outside air is equal to or higher than first predetermined value Ts1 but is equal to or lower than second predetermined value Ts2, the amount of the torque acting on the compressor drive shaft is medium. Second control unit 12′ operates to judge whether temperature Ts of the automobile outside air is lower than first predetermined value Ts1, equal to or higher than first predetermined value Ts1 but equal to or lower than second predetermined value Ts2, or higher than second predetermined value Ts2 by means of processing seventh control signal S7 therein. With reference to figure 7 again, operation of second control unit 12′ is as follows. When second control unit 12′ judges that temperature Tb of the automobile outside air is lower than first predetermined value Ts1, second control unit 12′ generates no control signal. Therefore, the operation of control apparatus 10′ is substantially left to only operation of first control unit 11. When second control unit 12′ judges that temperature Ts of the automobile outside air is higher than second predetermined value Ts2, second control unit 12′ generates fifth control signal S5. Fifth control signal S5 is sent to third control unit 13 from second control unit 12′, and is processed therein so as to deenergize the electromagnetic coil of electromagnetic clutch 101. When second control unit 12′ judges that temperature Ts of the automobile outside air is equal to or higher than first predetermined value Ts1 but is equal to or lower than second predetermined value Ts2, second control unit 12′ generates sixth control signal S6. Sixth control signal S6 is sent to third control unit 13 from second control unit 12′, and is processed therein so as to output electric current I of which value is Imax to the solenoid coil of the externally controlled valve device of the variable displacement mechanism. Figure 8 is a flow chart illustrating an operational manner of control apparatus 10′. Only difference between Figure 8 and Figure 4 which is the flow chart illustrating the operational manner of control apparatus 10 of the first embodiment is that steps 302 and 304 in Figure 4 are replaced with steps 302′ and 304′ in Figure 8, respectively. At step 302′ in Figure 8, whether temperature Ts of the automobile outside air is lower than first predetermined value Ts1 is judged. At step 304′ in Figure 8, whether temperature Ts of the automobile outside air is equal to or lower than second predetermined value Ts2 is judged. Figure 9 is a time chart illustrating the different operational stages of control apparatus 10′. With reference to Figure 9 in addition to Figure 8, each of the steps from step 302′ to step 313 via steps 306 and 307 in Figure 8 is carried out in stages (a) and (b). The difference between stage (a) with (b) is the length of On-time of switching device 15. In stage (a), the length ta of ON-time of switching device 15 is shorter than second predetermined time t2. Therefore, each of the steps from step 302′ to step 313 via steps 306 and 307 in Figure 8 is carried out only once in stage (a). On the other hand, in stage (b), the length tb of ON-time of switching device 15 is slightly longer than second predetermined time t2. Therefore, each of the steps from step 302′ to step 313 via steps 306 and 307 in Figure 8 is carried out twice in stage (b). Furthermore, each of the steps from step 302′ to step 313 via steps 305, 308 and 309 in Figure 8 is carried out in stages (c) and (d). The difference between stage (c) with (d) is the length of ON-time of switching device 15. In stage (c), the length tc of ON-time of switching device 15 is shorter than second predetermined time t2. Therefore, each of the steps from step 302′ to step 313 via steps 305, 308 and 309 in Figure 8 is carried out only once in stage (c). On the other hand, in stage (d), the length td of ON-time of switching device 15 is slightly longer than second predetermined time t2. Therefore, each of the steps from step 302′ to step 313 via steps 305, 308 and 309 in Figure 8 is carried out twice in stage (d). The effect of the second embodiment is similar to the effect of the first embodiment so that an explanation thereof is omitted.

Claims: An automotive air conditioning system including a compressor (100) with a variable displacement mechanism, an evaporator forming a part of the automotive air conditioning system, controlling means for controlling operation of the compressor, and a transmitting means (101) for intermittently transmitting power for moving an automobile to the compressor, the controlling means including a sensor (14) for sensing a heat load on the evaporator; a switching device (15) for sensing an amount of demand for acceleration of the automobile; first control unit (11) for determining an amount of torque acting on a drive shaft of the compressor; a second control unit (12) for judging whether the amount of demand for acceleration of the automobile is equal to or greater than a predetermined amount, and for judging whether the amount of the torque acting on the drive shaft of the compressor is smaller than a first predetermined amount, greater than a second predetermined amount which is greater than the first predetermined amount, or equal to or greater than the first predetermined amount but equal to or smaller than the second predetermined amount; a third control unit (13) for selectively operating the transmitting means (101) and the variable displacement mechanism in response to a judgement of the second control unit, the third control unit (13) operating the variable displacement mechanism so as to vary a capacity of the compressor (100) from the minimum to the maximum value thereof in response to changes in the heat load on the evaporator when the amount of demand for acceleration of the automobile is smaller than the predetermined amount, or both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is smaller than the first predetermined amount; the third control unit (13) operating the transmitting means so as not to transmit the power for moving the automobile to the compressor (100) both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is greater than the second predetermined amount; the third control unit (13) further operating the variable displacement mechanism so as to forcibly reduce the capacity of the compressor (100) to the minimum value thereof both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the amount of the torque acting on the drive shaft of the compressor is equal to or greater than the first predetermined amount but is equal to or smaller than the second predetermined amount. An automotive air conditioning system according to claim 1, wherein the sensor is a thermo-sensor (14) for detecting temperature of air immediately leaving from the evaporator. An automotive air conditioning system according to claim 2, wherein the first control unit (11) determines from the temperature detected by the thermo-sensor (14) the amount of torque acting on the drive shaft of the compressor (100). An automotive air conditioning system according to any one of the preceding claims, wherein the automobile includes an engine from which the power for moving the automobile is derived. An automotive air conditioning system according to claim 4, wherein the switching device (15) is an acceleration pedal used for the engine. An automotive air conditioning system according to claim 4 or claim 5, wherein the second control unit (12) is associated with the acceleration pedal used for the engine. An automotive air conditioning system according to claim 4 or claim 5, wherein the switching device is a pressure switch associated with an intake-manifold used for the engine. An automotive air conditioning system according to claim 4 or claim 5, wherein the switching device is a switching device associated with a throttling device used for the engine. An automotive air conditioning system according to any one of the preceding claims, wherein the transmitting means is an electromagnetic clutch (101). An automotive air conditioning system according to claim 9, wherein the electromagnetic clutch (101) includes an electro-magnetic coil. An automotive air conditioning system according to any one of the preceding claims, wherein the variable displacement mechanism includes an externally controlled valve device having a solenoid coil. An automotive air conditioning system including a compressor (100) with a variable displacement mechanism, an evaporator forming a part of the automotive air conditioning system, controlling means for controlling operation of the compressor, and a transmitting means (101) for intermittently transmitting power for moving an automobile to the compressor, the controlling means including a sensor (14) for sensing a heat load on the evaporator; a switching device (15) for sensing an amount of demand for acceleration of the automobile; a second sensor (16) for detecting the temperature of air outside the automobile; second control unit (12') for judging whether the amount of demand for acceleration of the automobile is equal to or greater than a predetermined amount, and for judging whether the temperature of air outside the automobile is smaller than a first predetermined amount, greater than a second predetermined amount which is greater than the first predetermined amount, or equal to or greater than the first predetermined amount but equal to or smaller than the second predetermined amount; a third control unit (13) for selectively operating the transmitting means (101) and the variable displacement mechanism in response to a judgement of the second control unit, the third control unit (13) operating the variable displacement mechanism so as to vary a capacity of the compressor (100) from the minimum to the maximum value thereof in response to changes in the heat load on the evaporator when the amount of demand for acceleration of the automobile is smaller than the predetermined amount, or both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is smaller than the first predetermined amount; the third control unit (13) operating the transmitting means so as not to transmit the power for moving the automobile to the compressor (100) both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is greater than the second predetermined amount; the third operating unit (13) further operating the variable displacement mechanism so as to forcibly reduce the capacity of the compressor (100) to the minimum value thereof both when the amount of demand for acceleration of the automobile is equal to or greater than the predetermined amount and when the temperature of air outside the automobile is equal to or greater than the first predetermined amount but is equal to or smaller than the second predetermined amount.

Inventors: TAGUCHI YUKIHIKO, TAGUCHI, YUKIHIKO, TAGUCHI, YUKIHIKO, C/O SANDEN CORPORATION
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1992
Main classification: B60H1
IPC codes: B60H1