Abstract:
An air conditioner has a controller that controls the operation of a refrigerant circuit that has a compressor, a condenser, an expansion valve or orifice tube, and an evaporator. The condenser receives a compressed refrigerant from the compressor and condenses the refrigerant to either a liquid phase or a saturated liquid-vapor phase. The condensed refrigerant is then passed through the expansion valve or orifice tube to expand the refrigerant and to delivery the refrigerant to the evaporator. When the compressor is first started, various sounds and vibrations are created that may be unpleasant to humans. Also, if the engine is cold, then the compressor may have liquid refrigerant that can increase the torque needed to start the compressor. The controller pulses the compressor between ON and OFF operating states to reduce or eliminate these sounds and/or manage the start up torque of the compressor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally relates to an air conditioner. More specifically, the present invention relates to an air conditioner control system for reducing refrigerant noise and for managing torque, during initial engagement of a compressor of the air conditioner.  
         [0003]     2. Background Information  
         [0004]     A typical automobile air conditioner includes a compressor, a condenser, an expansion valve or orifice tube, and an evaporator. The compressor compresses a cool vapor-phase refrigerant (e.g., Freon, R134a) to heat the same, resulting in a hot, high-pressure vapor-phase refrigerant. This hot vapor-phase refrigerant runs through a condenser, typically a coil that dissipates heat. The condenser condenses the hot vapor-phase refrigerant into liquid refrigerant. The liquid refrigerant is throttled through an expansion valve, which evaporates the refrigerant to a cold, low-pressure saturated liquid-vapor-phase refrigerant. This cold saturated liquid-vapor-phase refrigerant runs through the evaporator, typically a coil that absorbs heat from the air fed to the passenger compartment.  
         [0005]     When the compressor of an air conditioner is first started, the rapid pressure changes that occur with the compressor cycling from OFF to ON can create various sounds and vibrations that may be unpleasant to humans. The origin of these sounds and vibrations include, but not limited to, purging liquid from the compressor (known as slugging) and the refrigerant passing through the expansion valve or orifice tube. Also, if the engine is cold and liquid refrigerant is present in the compressor then this slugging of the refrigerant can increase the torque needed to start the compressor. This increase in the compressor torque requirement can have an adverse affect on the performance of the vehicle.  
         [0006]     In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved air conditioner control system that is quieter and/or easier to operate at start up. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention relates to an air conditioner comprising a heat removal device, an evaporator, a compressor and a controller. As mentioned above, it has been discovered that after engagement of the compressor of the air conditioner refrigerant noises occur. For example, these refrigerant noises can be due to purging liquid from the compressor (e.g., slugging) and/or due to refrigerant passing through the expansion valve or orifice tube. These sounds may include, but are not limited to, a bang, a knock, a clunk, a clang, a hissing etc., and may also include multiple variations, combinations, and repetitions thereof.  
         [0008]     One object of the present invention is to provide an air conditioner with control logic that is quieter and/or easier to operate at start up. In other words, the air conditioner of the present invention was basically contrived to avoid to the greatest extent possible the adverse effects of the compressor being started, e.g., minimizes the refrigerant noises at compressor start up and/or decrease the compressor torque requirements due to slugging at compressor start up.  
         [0009]     In view of the forgoing, an air conditioner is provided that basically comprises a heat removal device, an evaporator, a compressor and a controller. The heat removal device is configured to receive a refrigerant in a compressed state and remove heat from at least a portion of the refrigerant. The evaporator is in fluid communication with the heat removal device to receive the refrigerant, and is configured to evaporate at least a portion of the refrigerant. The compressor is in fluid communication with the evaporator, and configured to compress the refrigerant and deliver the refrigerant in the compressed state to the heat removal device. The controller is operatively coupled to the compressor to selectively operate the compressor in response to a compressor request signal. The controller is configured to cycle the compressor between at least one ON operating state for a period of time and at least one OFF operating state for a prescribed period of time and then operate the compressor for an additional period of time.  
         [0010]     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Referring now to the attached drawings which form a part of this original disclosure:  
         [0012]      FIG. 1  is a simplified schematic diagram of a portion of vehicle equipped with a refrigerant circuit in accordance with a first embodiment of the present invention;  
         [0013]      FIG. 2  is a first flowchart showing an initialization control logic or operations executed by the engine control unit or computer for a full time pulsing logic in accordance with the first embodiment of the present invention;  
         [0014]      FIG. 3  is a second flowchart showing a preferred full time pulsing control logic or operations executed by the computer in accordance with the first embodiment of the present invention;  
         [0015]      FIG. 4  is a third flowchart showing an exemplary normal control logic or operations executed by the computer in accordance with the first embodiment of the present invention;  
         [0016]      FIG. 5  is a fourth flowchart showing a modified pulsing control logic or operations executed by the computer as part of the pulsing control logic shown in  FIG. 3 ;  
         [0017]      FIG. 6  is a fifth flowchart showing an initialization control logic or operations executed by the engine control unit or computer for a one time pulsing logic in accordance with a second embodiment of the present invention; and  
         [0018]      FIG. 7  is a sixth flowchart showing a one time pulsing control logic or operations executed by the computer in accordance with the first embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.  
         [0020]     Referring initially to  FIG. 1 , an air conditioner  10  is illustrated in accordance with a first embodiment of the present invention. The air conditioner  10  according to the present invention is particularly suitable for an automobile or other passenger vehicle (such as but not limited to a car, an SUV, a minivan, a station wagon, a pick-up truck, etc.,) as well as refrigeration systems for homes and industrial use. In the illustrated embodiment, the air conditioner  10  is driven by a vehicle engine  12  in a conventional manner. Basically, the air conditioner  10  has a refrigerant circuit that includes an evaporator  14 , a compressor  16  with an electromagnetic clutch, a condenser  18  and an expansion valve or orifice  20 . Typically, the condenser  18  is located in front of a radiator  21  that cools the engine coolant of the engine  12 . These components  14 ,  16 ,  18  and  20  are conventional components that are well known in the air conditioning field. Since these components  14 ,  16 ,  18  and  20  are well known in the air conditioning field, the structures of the components  14 ,  16 ,  18  and  20  will not be discussed or illustrated in detail herein.  
         [0021]     The compressor  16  is fluidly connected to the condenser  18  via a refrigerant pipe or conduit. The evaporator  14  is also fluidly connected to the compressor  16  via a refrigerant pipe or conduit. The expansion valve  20  is fluidly connected to the condenser  18  via a refrigerant pipe or conduit, and to the evaporator  14  by a refrigerant pipe or conduit. Thus, a refrigerant (e.g., Freon, R134a) is circulated through the refrigerant circuit of the air conditioner  10  to cool the passenger compartment or vehicle cabin.  
         [0022]     In particular, the compressor  16  receives and compresses a cool vapor-phase refrigerant from the evaporator  14 . The compressor  16  is energizing or de-energizing the electromagnetic clutch of the compressor  16 . The compression action heats the refrigerant, resulting in a hot, high-pressure vapor-phase refrigerant. This hot vapor-phase refrigerant is then fed through the condenser  18 , such as an air-cooled coil that dissipates heat. The condenser  18  condenses the hot vapor-phase refrigerant into a liquid-phase refrigerant or a saturated liquid-vapor-phase refrigerant. In the preferred embodiment of the present invention, the condenser  18  condenses the refrigerant by air cooling. Thus, the condenser  18  of the preferred embodiment is a heat removal device. The condensed refrigerant is then delivered through the expansion valve  20 , which expands the liquid-phase or saturated liquid-vapor-phase refrigerant to a cold, low-pressure liquid-vapor-phase refrigerant having a higher vapor content. Thus, the high pressure refrigerant passes through the expansion valve  20  so as to be throttled to a low pressure and temperature. The cold liquid-vapor-phase refrigerant (having a higher vapor content than the refrigerant exiting the condenser) runs through the evaporator  14 , typically a coil that absorbs heat from and cools the air delivered to the passenger compartment or vehicle cabin.  
         [0023]     The operations of the air conditioner  10  are controlled by a set of operator controls  22  that are located in the cabin of the vehicle. The operator controls  22  typically will include an ON/OFF switch, a temperature control and a blower of fan speed control. Once the operator turns on the air conditioner  10 , a control signal is received by a computer controller  24  of the computer or engine control unit ECU. In other words, the computer controller  24  operates the air conditioner  10  in accordance with the settings of the operator controls  22 .  
         [0024]     The computer controller  24  basically controls the operation of the air conditioner  10  by operating the compressor  16  between an ON operating state and an OFF operating state. For example, the computer controller  24  selectively activates and deactivates a compressor clutch of the compressor  16  to switch between the ON operating state and the OFF operating state. More specifically, the computer controller  24  selectively activates the compressor  16  between the ON and OFF operating states based on various control signals so as to substantially maintain the passenger compartment or vehicle cabin at a prescribed temperature setting that was set by the operator controls  22 . Moreover, the computer controller  24  selectively controls a fan or blower  26  at a prescribed fan speed in accordance with a fan speed setting that was set by the operator controls  22 .  
         [0025]     In the illustrated embodiment, the normal control logic of the air conditioner  10  is based on control signals from one or more of the following sensors: an outside air temperature sensor  30 , a refrigerant pressure transducer or sensor  32 , an evaporator temperature sensor  34 , and an engine coolant temperature sensor  36 . The outside air temperature sensor  30  is configured and arranged to detect the outside air temperature Ta, and output a signal to the computer controller  24  that is indicative of the outside air temperature Ta. Preferably, the outside air temperature sensor  30  is disposed in front of the condenser  18 . The refrigerant pressure transducer or sensor  32  is configured and arranged to detect the refrigerant pressure P inside the condenser  18 , and output a signal to the computer controller  24  that is indicative of the refrigerant pressure P. The evaporator temperature sensor  34  is configured and arranged to detect the evaporator temperature Te, and output a signal to the computer controller  24  that is indicative of the evaporator temperature Te. The engine coolant temperature sensor  36  is configured and arranged to detect the temperature of the engine coolant Tw, and output a signal to the computer controller  24  that is indicative of the temperature of the engine coolant Tw.  
         [0026]     The precise of control of the air conditioner  10  during normal control operations is not important to the present invention. Thus, the normal control logic of the air conditioner  10  will only be briefly discussed below in a simplified manner with respect to the flow chart illustrated in  FIG. 4 . Rather, the description of the present invention will focus on the control logic or operations during initial engagement of the compressor  16  of the air conditioner  10  for reducing refrigerant noise and for managing compressor torque. The control logic or operations during initial engagement of the compressor  16  of the air conditioner  10  is controlled by the computer controller  24 .  
         [0027]     The computer controller  24  preferably includes a microprocessor and an air conditioner control program that controls the compressor  16  as discussed below. The computer controller  24  can also include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The microprocessor of the computer controller  24  is programmed to control the air conditioner  10 . The memory circuit stores processing results and control programs for controlling the operation of the compressor  16 . The computer controller  24  is operatively coupled to the engine control unit ECU in a conventional manner. The internal RAM of the computer controller  24  stores statuses of operational flags and various control data. The internal ROM of the computer controller  24  stores the control logic for various operations of air conditioner  10 . It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the computer controller  24  can be any combination of hardware and software that will carry out the functions of the present invention. In other words, “means plus function” clauses as utilized in the specification and claims should include any structure or hardware and/or algorithm or software that can be utilized to carry out the function of the “means plus function” clause.  
         [0028]     Basically, the computer controller  24  is configured and arranged to initially cycle the compressor  16  between at least one ON operating state for a predetermined period of time and at least one OFF operating state for a prescribed period of time, and then subsequently operate the compressor  16  using normal logic for an additional period of time, i.e., until the cabin temperature has reached the temperature setting that was set by the operator utilizing the operator controls  22 . Preferably, the computer controller  24  includes a compressor ON timer that is configured to at least measure the time that the compressor  16  is in the ON operating state and a compressor OFF timer that is configured to at least measure the time that the compressor  16  is in the ON operating state.  
         [0029]     In the full time logic, this cycling of the compressor  16  by the computer controller  24  occurs each and every time the compressor  16  is started. Preferably, the computer controller  24  produces a compressor request signal to start the compressor  16  once the air conditioner  10  has been turned ON. In the illustrated embodiment, when the compressor request signal is issued, a compressor request flag CompReq is set to “I 1  ” to represent that the compressor  16  has been set to an ON operating state. When the compressor request signal has been sent to turn OFF the compressor  16 , then the compressor request flag CompReq is set to “ 0 ” to represent that the compressor  16  has been set to an OFF operating state.  
         [0030]     Depending upon the particular application, the computer controller  24  can be set to repeatedly cycle the compressor  16  between the ON operating state and the OFF operating state as needed and/or desired. This cycling of the compressor  16  between the ON and OFF operating states reduces the refrigerant noises occurring during start up of the compressor  16 , as well as reduces the torque load on the engine  12  that may occur due to slugging of the compressor  16 . This control logic of the present invention is preferably run in a timing loop such that other routines can be conducted without waiting.  
         [0031]     In one possible embodiment of the present invention, the compressor  16  is turned ON for approximately one second and then turned OFF for one second before the compressor  16  is continuously run until the evaporator  14  reaches the desired temperature needed for cooling the vehicle cabin in response to the temperature setting by the operator controls  22 . Of course, it will apparent to those skilled in the art from this disclosure that the cycling times can be extended or shortened. Preferably, the entire cycling of the compressor  16  between the ON and OFF operating states occurs within approximately three or four seconds. Of course, these prescribed time periods can be extended depending upon the applications. Moreover, the prescribed period for the ON and OFF operating states can be varied based on the ambient temperature. For example, the computer controller  24  can be configured to increase the length of the prescribed time period for the OFF operating state when the ambient temperature becomes lower, while maintaining the prescribed time period for the ON operating state constant or varying the length of the prescribed time period for the ON operating state as needed and/or desired for the particular situation.  
         [0032]     The control operations executed by the computer controller  24  will now be described with reference to the functional block diagrams or flow charts of FIGS.  2  to  7 . Many of the functions described below are functions that are preferably executed using software processing. The control routine of  FIG. 2  is only executed shortly after the engine  12  is started. The control routines of  FIGS. 3 and 7 , on the other hand, are periodically executed in a cyclic manner at a prescribed fixed time interval when the engine  12  is operating in accordance with certain predetermined operating conditions, e.g., when the air conditioner  10  has been turned ON.  
         [0033]     Referring first to  FIG. 2 , a first flowchart is illustrated showing an initialization control logic executed by the computer controller  24  for a full time pulsing logic in accordance with the first embodiment of the present invention. The initialization control logic of  FIG. 2  is conducted shortly after the engine is started, but prior to starting the compressor  16 . Preferably, the initialization control logic is executed by the computer controller  24  each time the engine  12  is started. This control logic is preferably suspends all other control processes relating to the compressor  16 , until the compressor  16  has been cycled between the ON and OFF operating states at least once.  
         [0034]     In step S 1  of  FIG. 2 , the computer controller  24  is configured to determine if the initialization control logic has been already completed. If the initialization control logic has not been completed, then the computer controller  24  proceeds to step S 2 . If the initialization control logic has been already completed, then the processing ends.  
         [0035]     In step S 2 , the computer controller  24  is configured to clear the compressor ON timer (i.e., set ONTMR=0). Thus, the compressor ON timer will start counting from zero when the main control routine is executed by the computer controller  24  as explained below.  
         [0036]     Next in step S 3 , the computer controller  24  is configured to clear the compressor OFF timer (i.e., set ONTMR=0). Thus, the compressor OFF timer will start counting from zero when the main control routine is executed by the computer controller  24  as explained below.  
         [0037]     In step S 4 , the computer controller  24  is configured to set the compressor  16  to the OFF operating state (i.e., set CompReq=0) such that the operation of the compressor  16  is initially delayed until the compressor  16  has been cycled through at least one ON operating state and at least one OFF operating state.  
         [0038]     In step S 5 , the computer controller  24  sets a flag indicating the initialization has been completed such that subsequent processing of the initialization control logic ends, until the engine  12  is turned off and restarted.  
         [0039]     Referring now to  FIG. 3 , a flowchart is illustrated showing a preferred full time pulsing control logic executed by the computer controller  24  in accordance with the first embodiment of the present invention. The full time pulsing control logic of  FIG. 3  is conducted after the initialization control logic has been completed.  
         [0040]     In step S 11 , the computer controller  24  executes normal control logic to set the compressor request flag CompReq to “1”, or “0”. The normal control logic will be explained later with reference to  FIG. 4 .  
         [0041]     In step S 12 , the computer controller  24  is configured to determine if the compressor request flag CompReq is set to the ON operating state (CompReq=“1”) or if the compressor request flag CompReq is set to the OFF operating state (CompReq=“0”). If the compressor request flag CompReq is set to “0”, then the control process proceeds to step S 13 , because the operation of the compressor  16  is not necessary at this time.  
         [0042]     In step S 13 , the computer controller  24  is configured to clear the compressor ON and OFF timers ONTMR and OFFTMR. In other words, the times ONTMR and OFFTMR counted by the compressor ON and OFF timers are both set to “0”. Then, the computer controller  24  proceeds to step S 14 .  
         [0043]     In step S 14 , the computer controller  24  turns OFF the compressor  16  if the compressor  16  is not already in the OFF operating state.  
         [0044]     However, in step S 12 , if the compressor request flag CompReq is set to “1”, then there is a compressor request to turn ON the compressor  16  to cool down the evaporator  14 . Thus, the computer controller  24  proceeds to step S 15 .  
         [0045]     In step S 15 , the computer controller  24  is configured to determine if a prescribed amount of time N 1  has elapsed since the compressor  16  has been activated. In other words, in step S 15 , the computer controller  24  determines if the compressor  16  has been in the ON operating state for a prescribed period of time N 1  as measured by the compressor ON timer. In particular, in step S 15 , the computer controller  24  compares the elapsed time ONTMR counted by the ON timer to the prescribed period of time N 1 . Initially, the elapsed time ONTMR is set to “0” due to the initialization control logic or due to step S 13 . This prescribed period of time can be determined using experimental data for the particular situation. In the case where the engine has just been started and the air conditioner has been turned ON, the computer controller  24  will determine that the elapsed time ONTMR has not exceeded the prescribed period of time N 1 , because the elapsed time ONTMR counted by the ON timer was previously set to “0”. Thus, the computer controller  24  will proceed to step S 16 .  
         [0046]     In step S 16 , the computer controller  24  increments the elapsed time ONTMR by a predetermined amount. Preferably, the value of the prescribed period of time N 1  is directly correlated to the processing time to run the full time control logic. In other words, each increment preferably corresponds to the amount of time that has elapsed since the computer controller  24  last compared the elapsed time ONTMR counted by the ON timer to the prescribed period of time N 1  in step S 15 . For example, this entire routine might be executed once every 0.1 second. If this is the case, then each increment of the ON timer is equivalent to 0.1 second in step S 16 .  
         [0047]     Once the elapsed time ONTMR is incremented in step S 16 , the computer controller  24  proceeds to step S 17 . In step S 17 , the compressor  16  is turned ON. In particular, the compressor  16  includes an electromagnetic clutch that is engaged by the computer controller  24  to operate the compressor  16 .  
         [0048]     The processing by the computer controller  24  returns to the beginning of this main routine such that the computer controller  24  continues to execute steps S 11 , S 12 , S 15 , S 16 , and S 17  until the elapsed time ONTMR has been incremented such that the prescribed period of time N 1  has elapsed. In other words, the computer controller  24  determines in step S 15  that the elapsed time ONTMR counted by the ON timer has exceeded the prescribed period of time N 1 . Thus, the computer controller  24  proceeds to step S 18 .  
         [0049]     In step S 18 , the computer controller  24  determines if the elapsed time OFFTMR counted by the compressor OFF timer has reached or exceeded a prescribed amount of time, i.e., if a prescribed amount of time F 1  has elapsed since the compressor  16  has been turned OFF. Initially, the elapsed time OFFTMR is set to “0” by step S 3  of the initialization control logic before the compressor  16  is first started or by step S 13  after the compressor request flag CompReq is set to the OFF operating state (CompReq=“0”). Accordingly, at least initially, the computer controller  24  proceeds to step S 19  after the compressor  16  is first started.  
         [0050]     In step S 19 , the computer controller  24  increments the elapsed time OFFTMR by a prescribed amount of time. Similar to the incrementing of the elapsed time ONTMR, the prescribed amount of time for incrementing the elapsed time OFFTMR counted by the OFF timer is preferably based on the execution time of the computer controller  24  to complete a complete loop from the prior comparison between the elapsed time OFFTMR counted by the elapsed time OFFTMR and the prescribed amount of time F 1  in step S 18 .  
         [0051]     Once the elapsed time OFFTMR has been incremented in step S 19 , the computer controller  24  proceeds to step S 14  to deactivate the compressor  16  if it has not already been deactivated. Accordingly, the computer controller  24  continuously executes steps S 11 , S 12 , S 15 , S 18 , S 19 , and S 14 , until the elapsed time OFFTMR exceeds the prescribed amount of time F 1 . If the elapsed time OFFTMR exceeds the prescribed amount of time F 1 , then the computer controller  24  proceeds to step S 17 , where the computer controller  24  activates the compressor  16 .  
         [0052]     Once both the elapsed time ONTMR exceeds the prescribed amount of N 1  and the elapsed time OFFTMR exceeds the prescribed amount of F 1 , then the compressor  16  runs continuously until the evaporator temperature Te of the evaporator  14  exceeds a predetermined threshold for cooling the vehicle cabin. More particularly, the control logic shown in  FIG. 4  is continuously executed so long as the air conditioner remains ON.  
         [0053]     Referring now to  FIG. 4 , an exemplary normal control logic is illustrated for controlling the compressor  16  to substantially maintain the vehicle cabin temperature that has been set by the operator controls  22 . Of course, it will be apparent to those skilled in the art from this disclosure that other control programs can be utilized for maintaining cabin temperature as needed and/or desired without departing from the scope of the present invention.  
         [0054]     In step S 21 , first, the computer controller  24  determines if the air conditioner  10  has been turned ON. In other words, the computer controller  24  determines if the operator has turned the ON/OFF switch of the operator controls  22  to an ON position, and thus, the operator has requested air conditioning for the vehicle cabin. If the computer controller  24  determines that the air conditioner  10  has been turned ON, then the computer controller  24  proceeds to step S 22 .  
         [0055]     In step S 22 , the computer controller  24  is configured to measure the evaporator temperature Te of the evaporator  14 . In particular, the computer controller  24  receives a control signal from the evaporator temperature sensor  34  that is indicative of the current evaporator temperature Te, and then the computer controller  24  proceeds to step S 23 .  
         [0056]     In step S 23 , the computer controller  24  determines whether the compressor  16  is currently in an ON operating state. When the air conditioner  10  is initially turned ON, the compressor  16  is initially maintained in the OFF operating state due to step S 4  of the initialization control logic. Thus, initially, the computer controller  24  proceeds from step S 23  to step S 24 .  
         [0057]     In step S 24 , the computer controller  24  determines if the evaporator temperature Te has exceeded a prescribed ON temperature threshold value ONTHRESH for the evaporator  14 . In other words, the computer controller  24  determines whether the evaporator temperature Te is too warm and the compressor should be turned ON to cool down the evaporator  14 . Of course, if the air conditioner  10  has just been turned ON, the evaporator temperature Te will most likely be greater than the prescribed ON temperature threshold value ONTHRESH. Thus, the computer controller  24  will at least initially proceed to step S 25 .  
         [0058]     In step S 25 , the compressor request flag CompReq is set to 1 (CompReq=“1”) so that the compressor  16  will be activated as the processing continues. Thus, the computer controller  24  proceeds to step S 12 , discussed above, to determine whether the compressor request flag CompReq is set to “0” or “1”. After the initially cycling of the compressor  16 , when the evaporator temperature Te of the evaporator  14  was determined to be greater than the prescribed ON temperature threshold value ONTHRESH in step S 24  and the compressor request flag CompReq was set to 1 in step S 25 , the computer controller  24  proceeds from step S 12  to steps S 15 , S 18  and S 16 , where the compressor  16  is turned ON. Thus, the computer controller  24  then continuously loops through the control loops of  FIGS. 3 and 4  until the evaporator temperature Te exceeds the prescribed OFF temperature threshold value OFFTHRESH for the evaporator  14  as explained below.  
         [0059]     On the other hand, in step S 24 , if the evaporator temperature Te is less than the prescribed ON temperature threshold value ONTHRESH for the evaporator  14 , then the computer controller  24  proceeds directly to steps S 12 , S 13  and S 14 , such that the elapsed times ONTMR and OFFTMR are cleared and the compressor  16  is maintained in the OFF operating state.  
         [0060]     Referring back to step S 23 , if the compressor  16  is currently in the ON operating state, then the computer controller  24  proceeds from step S 23  to step S 26  for when to turn OFF the compressor  16 .  
         [0061]     In step S 26 , the computer controller  24  determines if the evaporator temperature Te is below the prescribed OFF temperature threshold value OFFTHRESH for the evaporator  14 . If the evaporator temperature Te has fallen below the prescribed OFF temperature threshold value OFFTHRESH, then the computer controller  24  proceeds to step S 27 .  
         [0062]     In step S 27 , the computer controller  24  sets the compressor request flag CompReq to 0 (CompReq=“0”). Then, the computer controller  24  proceeds to step S 12  of the flow chart shown in  FIG. 3 . Since the compressor request flag CompReq has been set to “0”, the computer controller  24  proceeds from step S 12  to S 14  where the ONTMR and the OFFTMR are both cleared or set to “0” and where the compressor  16  is deactivated to the OFF operating state. The compressor  16  will remain in the OFF operating state, until the evaporator temperature Te rises above the prescribed ON temperature threshold value ONTHRESH for the evaporator  14 , which is determined in step S 24 .  
         [0063]     Thus, the computer controller  24  continues to execute the control logic of  FIGS. 3 and 4  until the air conditioner  10  has been turned OFF by the operator controls  22 .  
         [0064]     Referring now to  FIG. 5 , a modified full time control logic is illustrated in accordance with the present invention. Basically, the control logic of  FIG. 5  adds new steps S 18   a  and S 18 B to the control logic of  FIG. 3 . Accordingly, only steps S 18   a  and S 18   b  will be discussed.  
         [0065]     Basically, the control logic shown in  FIG. 5  adds an additional compressor ON/OFF cycle to the control logic of  FIG. 3 . In other words, after the prescribed times N 1  and F 1  has both elapsed (ONTMR&gt;N 1  and OFFTMR&gt;F 1 ), the computer controller  24  first determines whether or not the elapse time ONTMR has exceeded a second prescribed period of time N 2  in step S 18   a  for reactivating the compressor  16  for the second prescribed period of time N 1 . Next, the computer controller  24  determines whether or not the elapse time OFFTMR has exceeded a second prescribed period of time F 2  in step S 18   b  for deactivating the compressor  16  for the second prescribed period of time F 1 .  
         [0066]     In other words, after the elapse times ONTMR and OFFTMR have exceeded the first prescribed values N 1  and F 1 , then the computer controller  24  first determines if the second prescribed compressor ONTMR has exceeded the prescribed time N 2 . If the time ONTMR counted by the ON timer has not exceeded the prescribed time period N 2 , then the computer controller  24  proceeds to step S 16  to increment the elapse time ONTMR by a prescribed amount.  
         [0067]     Then, the computer controller  24  proceeds to step S 17  to reactivate the compressor  16  for a second time. The control logic continues to loop through steps S 18   a , steps S 16  and S 17  until the elapse time ONTMR counted by the ON timer exceeds the prescribed time N 2 . Once the prescribed time N 2  has been exceeded, then the computer controller  24  proceeds to step S 18   b.    
         [0068]     In step S 18   b , the computer controller  24  determines if the elapse time OFFTMR counted by the OFF timer has exceeded the second prescribed time F 2 . If not, the computer controller  24  proceeds to step S 19  where the elapse time OFFTMR is incremented. Then the computer controller  24  proceeds to step S 14  where the compressor  16  is deactivated, if not previously deactivated. The control loop continues to process through steps S 18   b , S 19 , and S 14  to maintain the compressor  16  in the OFF operating state until the elapse time OFFTMR exceeds the prescribed time F 2 . Once the prescribed time F 2  has been exceeded, the processing proceeds to step S 17  where the compressor  16  is reactivated. Now, the computer controller  24  operates the cycling of the compressor  16  according to the normal control logic of  FIG. 4 .  
         [0069]     It will be apparent to those skilled in the art from this disclosure that additional cycles can be added for pulsating the compressor  16  between ON and OFF operating states by adding additional steps similar to steps S I  8   a  and S I  8   b  that include larger prescribed times N 3 , N 4 , . . . and F 3 , F 4 , . . . that are counted by the ON and OFF timers, respectively.  
         [0070]     Now referring to  FIGS. 6 and 7 , a one time pulsing logic in accordance with a second embodiment of the present invention will now be discussed. The control logic illustrated in  FIGS. 6 and 7  are utilized separately from the prior full time pulsing logic. The control logic of  FIGS. 6 and 7  is directed to minimize the noise due to slugging and/or manage the torque load on the engine due to the liquid refrigerant in the compressor  16 . Thus, after, the initial pulsing or cycling of the compressor  16 , the air conditioner  10  is operated according to the normal control logic of  FIG. 4 .  
         [0071]     Referring initially to the initialization logic of  FIG. 6 , basically, the initialization control logic of  FIG. 6  is identical to the initialization control logic of  FIG. 2 , except that additional steps have been added such that pulsing of the compressor  16  between ON and OFF operating states only occurs when the engine  12  is cold and when there is a possibility of liquid refrigerant accumulating in the compressor  16 . Thus, during initialization, when the engine is cold (i.e., Tw&lt;EC 1 ), the computer controller  24  clears the timers (OFFTMR and ONTMR) so that the compressor  16  is cycled or pulsed at least once before conducting the normal control logic of  FIG. 4 . However, if the engine is hot (i.e., Tw&gt;EC 1 ), then the computer controller  24  sets the timers such that the pulsing of the compressor  16  does not occur (i.e., OFFTMR&gt;F 1  and ONTMR&gt;N 1 ) and the normal control logic of  FIG. 4  is immediately used when the air conditioner  10  is turned ON.  
         [0072]     Specifically, in step S 32 , the computer controller  24  measures engine coolant temperature Tw to determine the current temperature of the engine  12 . More specifically, the engine coolant temperature sensor  36  sends a signal to the computer controller  24  that is indicative of the coolant temperature of the engine  12 .  
         [0073]     Then in step S 37 , the computer controller  24  determines if the engine coolant temperature Tw has fallen below a prescribed engine coolant temperature EC 1 . In other words, the computer controller  24  is determining whether the engine temperature Tw has fallen below a temperature in which there is a probability that a liquid refrigerant has accumulated in the compressor  16 . If the computer controller  24  determines that the engine coolant temperature Tw has fallen below the prescribed engine coolant temperature EC 1 , then the computer controller  24  proceeds to step S 33 . However, if the engine coolant temperature Tw has not fallen below the prescribed coolant temperature EC 1 , then the computer controller proceeds to step S 38 .  
         [0074]     In step S 38 , the computer controller  24  sets the elapsed time OFFTMR counted by the OFF timer to a value that is greater than the prescribed time F 1 . Thus, the computer controller  24  effectively deactivates the OFF timer in step S 38 . The computer controller  24  then proceeds to step S 39 .  
         [0075]     In step S 39 , the computer controller  24  sets the elapsed time ONTMR counted by the ON timer to a value that is greater than the prescribed time N 1 . Thus, the computer controller  24  effectively deactivates the ON timer such that the compressor  16  is not pulsed between the ON and OFF operating states when the engine coolant temperature Tw is greater than the prescribed engine coolant temperature EC 1 .  
         [0076]     When the computer controller  24  is utilizing the one time pulse control logic of  FIG. 7 , then the compressor  16  is cycled between ON and OFF operating states only the very first time the air conditioner  10  is operated. In other words, when the compressor  16  cycles between ON and OFF operating states during normal operation, the compressor  16  is not pulsed between ON and OFF operating states for the purpose of reducing noise as in the prior embodiment. This is because the elapsed times ONTMR and OFFTMR counted by the ON timer and OFF timer, respectively, are not cleared until the engine  12  has been restarted.  
         [0077]     In step S 41 , the computer controller  24  executes normal control logic to set the compressor request flag CompReq to “1”, or “0” as explained above with reference to  FIG. 4 .  
         [0078]     In step S 42 , the computer controller  24  is configured to determine if the compressor request flag CompReq is set to the ON operating state (CompReq=” 1”) or if the compressor request flag CompReq is set to the OFF operating state (CompReq=“0”). If the compressor request flag CompReq is set to “0”, then the control process proceeds to step S 43 , because the operation of the compressor  16  is not necessary at this time.  
         [0079]     In step S 43 , the computer controller  24  turns OFF the compressor  16  if the compressor  16  is not already in the OFF operating state.  
         [0080]     However, in step S 42 , if the compressor request flag CompReq is set to “1”, then there is a compressor request to turn ON the compressor  16  to cool down the evaporator  14 . Thus, the computer controller  24  proceeds to step S 44 .  
         [0081]     In step S 44 , the computer controller  24  is configured to determine if a prescribed amount of time N 1  has elapsed since the compressor  16  has been activated. In other words, in step S 44 , the computer controller  24  determines if the compressor  16  has been in the ON operating state for the prescribed period of time N 1  as measured by the compressor ON timer. In particular, in step S 44 , the computer controller  24  compares the elapsed time ONTMR counted by the ON timer to the prescribed period of time N 1 . If the elapsed time ONTMR is set to “0” due to the initialization control logic, then the computer controller  24  will proceed to step S 45 .  
         [0082]     In step S 45 , the computer controller  24  increments the elapsed time ONTMR by a predetermined amount. Preferably, the value of the prescribed period of time N 1  is directly correlated to the processing time to run the full time control logic.  
         [0083]     Once the elapsed time ONTMR is incremented in step S 45 , the computer controller  24  proceeds to step S 46 . In step S 46 , the compressor  16  is turned ON. In particular, the compressor  16  includes an electromagnetic clutch that is engaged by the computer controller  24  to operate the compressor  16 .  
         [0084]     The processing by the computer controller  24  returns to the beginning of this main routine such that the computer controller  24  continues to execute steps S 41 , S 42 , S 44 , S 45 , and S 46  until the elapsed time ONTMR has been incremented such that the prescribed period of time N 1  has elapsed. In other words, the computer controller  24  determines in step S 44  that the elapsed time ONTMR counted by the ON timer has exceeded the prescribed period of time N 1 . Thus, the computer controller  24  proceeds to step S 47 .  
         [0085]     In step S 47 , the computer controller  24  determines if the elapsed time OFFTMR counted by the compressor OFF timer has reached or exceeded a prescribed amount of time, i.e., if a prescribed amount of time F 1  has elapsed since the compressor  16  has been turned OFF. If the elapsed time OFFTMR is set to “0” by step S 33  of the initialization control logic before the compressor  16  is first started, then the computer controller  24  proceeds to step S 48 .  
         [0086]     In step S 48 , the computer controller  24  increments the elapsed time OFFTMR by a prescribed amount of time. Similar to the incrementing of the elapsed time ONTMR, the prescribed amount of time for incrementing the elapsed time OFFTMR counted by the OFF timer is preferably based on the execution time of the computer controller  24  to complete a complete loop from the prior comparison between the elapsed time OFFTMR counted by the elapsed time OFFTMR and the prescribed amount of time F I in step S 18 .  
         [0087]     Once the elapsed time OFFTMR has been incremented in step S 48 , the computer controller  24  proceeds to step S 43  to deactivate the compressor  16  if it has not already been deactivated. Accordingly, the computer controller  24  continuously executes steps S 41 , S 42 , S 44 , S 47 , S 48  and S 49 , until the elapsed time OFFTMR exceeds the prescribed amount of time F 1 . If the elapsed time OFFTMR exceeds the prescribed amount of time F 1 , then the computer controller  24  proceeds to step S 46 , where the computer controller  24  activates the compressor  16 .  
         [0088]     Once both the elapsed time ONTMR exceeds the prescribed amount of N 1  and the elapsed time OFFTMR exceeds the prescribed amount of F 1 , then the compressor  16  runs continuously until the evaporator temperature Te of the evaporator  14  exceeds a predetermined threshold for cooling the vehicle cabin. More particularly, the control logic shown in  FIG. 4  is continuously executed so long as the air conditioner remains ON.  
         [0089]     The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.  
         [0090]     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.