Patent Publication Number: US-2007095098-A1

Title: Expansion valve for rear seat air conditioner

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an expansion valve for a rear seat air conditioner of an automotive vehicle, and more particularly, to an expansion valve for a rear seat air conditioner of an automotive vehicle, which can circulate a flow of refrigerant stagnated between a compressor and the rear seat air conditioner through a bleeding channel of the expansion valve when only a front seat air conditioner is operated stopping operation of the rear seat air conditioner, thereby supplying oil contained in refrigerant between the compressor and the rear seat air conditioner to the compressor.  
      2. Background Art  
      In general, a rear seat air conditioner for a vehicle is applied to automotive vehicles of a large capacity, for instance, vans, RVs (Recreational Vehicles), or deluxe vehicles, as large as only a front seat air conditioner cannot agreeably cool or heat the inside of the vehicle. The rear seat air conditioner is installed in a sealed space of the rear of the vehicle in link with the front seat air conditioner, and so, constitutes a dual air conditioner together with the front seat air conditioner.  
      A dual air conditioner shown in  FIG. 1  includes a front seat air conditioner  10  and a rear seat air conditioner  30 .  
      The front seat air conditioner  10  includes: a compressor  12  for compressing and discharging refrigerant; a condenser  14  for condensing refrigerant discharged from the compressor  12 ; a receiver dryer  16  for separating gas from the condensed refrigerant; a front expansion valve  18  for expanding refrigerant discharged from the receiver dryer  16 ; a front evaporator  22  embedded in a front air conditioning case  20  for converting the air into cold air by thermally exchanging refrigerant supplied from the front expansion valve  18  and air blown from a front air blast  26  and sending refrigerant to the compressor  12 ; and a front heater core  24  embedded in the front air conditioning case  20  for converting the air into hot air by thermally exchanging cooling water flowing therein and air blown from the front air blast  26 .  
      In addition, the rear seat air conditioner  30  includes: a rear expansion valve  34  for expanding refrigerant discharged from the receiver dryer  16  of the front seat air conditioner  10 ; a rear evaporator  36  embedded in a rear air conditioning case  32  for converting the air into cold air by thermally exchanging refrigerant supplied from the rear expansion valve  34  and air blown from a rear seat air blast  40  and sending refrigerant to the compressor  12 ; and a rear heater core  38  embedded in the rear air conditioning case  32  for converting the air into hot air by thermally exchanging cooling water flowing therein and air blown from the front air blast  40 .  
      Meanwhile, the front expansion valve  18  or the rear expansion valve  34  is mounted on an inlet of the front evaporator  22  or the rear evaporator  36  and expands refrigerant of high temperature and high pressure discharged from the receiver dryer  16  to convert it into a low pressure state of a dew form and supply it to the evaporator, thereby increasing evaporation efficiency.  
      Since a thermal load of the air conditioner is changed by the outdoor temperature, humidity, the number of passengers, rotational frequency of the compressor  12 , and so on, there is a need to adjust a flow rate of refrigerant circulating inside a cycle to show the best capability of each units coping with the change, and so, the expansion valves  18  and  34  serves to adjust the flow rate of refrigerant.  
      Moreover, if the thermal load is large in a state where the refrigerant amount is uniform, when refrigerant arrives at an outlet of the evaporator  22  or  36 , since refrigerant is completely evaporated and absorbs heat more, temperature of refrigerant gas reaches an overheated state where it is higher than evaporation temperature. There is no problem if the overheated level is small, but if the overheated level is large, discharge temperature of the compressor  12  rises, and so, a cylinder (not shown) of the compressor  12  is heated. On the contrary, if the thermal load is small, refrigerant is not completely evaporated event at an outlet of the evaporator  22  or  36  and refrigerant of a liquid state is sucked into the compressor  12  to cause liquid compression, and thereby, a valve unit (not shown) of the compressor  12  is damaged. The expansion valves  18  and  34  serve to supply refrigerant of a proper amount to the evaporators  22  and  36  and to keep the overheated level in a fixed state even though there is a change in thermal load.  
       FIG. 2  shows an example of the rear expansion valve  34  of the expansion valves  18  and  34 . The rear expansion valve  34  includes: a valve block  50 ; a low-pressure refrigerant channel  52  horizontally mounted on the upper end part of the valve block  50  for connecting the compressor  12  with the outlet of the rear evaporator  36 ; a high-pressure refrigerant channel  54  horizontally mounted on the lower end part of the valve block  50  and having an entrance portion  55  connected to the receiver dryer  16 , a discharge portion  56  connected to the inlet of the rear evaporator  36 , and an orifice  57  for connecting the entrance portion  55  and the discharge portion  56  with each other; a temperature sensing bulb  60  mounted on the upper end of the valve block  50 ; a pressure delivery bar  64  liftably mounted across the low-pressure refrigerant channel  52  and the orifice  57  of the high-pressure refrigerant channel  54  from the temperature sensing bulb  60 ; and a ball valve  68  mounted on a communication path  66  fluidically communicating with the orifice  57  and the entrance portion  55  to adjust an opening degree of the orifice  57  in link with the pressure delivery bar  64 .  
      Operation of the rear expansion valve  34  will be described. When refrigerant is introduced from the receiver dryer  16  to the entrance portion  55  of the high-pressure refrigerant channel  54 , the opening degree of the orifice  57  is adjusted according to ascent and descent of a ball  69  of the ball valve  68  due to a vertical movement of the pressure delivery bar  64 . Therefore, refrigerant introduced into the entrance portion  55  can be supplied to the rear evaporator  36  through the communication path  66 , the orifice  57  and the discharge portion  56  in order while adjusting its flow rate. That is, when temperature of refrigerant discharged from the rear evaporator  36  to the low-pressure refrigerant channel  52  is lowered, temperature of refrigerant is transferred to the temperature sensing bulb  60  through the pressure delivery bar  64 . Therefore, temperature of a gas chamber  62  inside the temperature sensing bulb  60  is lowered, a diaphragm  61  mounted inside the temperature sensing bulb  60  is displaced upwardly, whereby the pressure delivery bar  64  is moved upwardly and the opening degree of the orifice  57  is reduced, so that the flow rate of refrigerant is reduced. On the contrary, when temperature of refrigerant flowing inside the low-pressure refrigerant channel  52  rises, the flow rate of refrigerant is increased.  
      However, in case of an automotive vehicle to which the dual air conditioner shown in  FIG. 1  is applied, when there is no passenger on the rear seat, generally, only the front seat air conditioner  10  is operated stopping the operation of the rear seat air conditioner. In this instance, in the state where the prior art rear expansion valve  34  is applied, since the orifice  57  is intercepted, refrigerant circulation between the compressor  12  and the rear seat air conditioner  30  is stagnated. An oil content of refrigerant introduced into the compressor  12  may be indicated as an oil circulation rate. Since refrigerant circulation between the compressor  12  and the rear seat air conditioner  30  is stagnated, oil contained in refrigerant in the stagnated area cannot be supplied to the compressor  12 . Therefore, as shown in  FIG. 3 , the oil circulation rate is reduced from the time when operation of the rear seat air conditioner  30  is stopped, and so, it may have a bad influence on durability of the compressor  12 , for instance, sticking of the compressor  12 , due to a lack of lubrication and cause a serious operational noise of the compressor  12  as operational time of the compressor  12  passes.  
     SUMMARY OF THE INVENTION  
      Accordingly, the present invention has been made to solve the above problems occurring in the prior arts, and it is an object of the present invention to provide an expansion valve for a rear seat air conditioner of an automotive vehicle, which can circulate a flow of refrigerant stagnated between a compressor and the rear seat air conditioner through a bleeding channel of the expansion valve for the rear seat air conditioner when a front seat air conditioner is operated stopping the operation of the rear seat air conditioner, thereby supplying oil contained in refrigerant between the compressor and the rear seat air conditioner to the compressor.  
      To accomplish the above object, according to the present invention, there is provided an expansion valve for a rear seat air conditioner of an automotive vehicle including: a low-pressure refrigerant channel for connecting an outlet of a rear evaporator with a compressor; a high-pressure refrigerant channel having an entrance portion for introducing condensed refrigerant into the high-pressure refrigerant channel, a discharge portion connected to an inlet of the rear evaporator, and an orifice for connecting the entrance portion and the discharge portion with each other; a pressure delivery bar liftably mounted across the low-pressure refrigerant channel and the orifice of the high-pressure refrigerant channel; a temperature sensing bulb connected with the pressure delivery bar; and a ball valve mounted on a communication path fluidically communicating with the orifice and the entrance portion for adjusting an opening degree of the orifice in link with the pressure delivery bar, wherein the orifice includes a slant enlarged portion formed on the communication path side so that a ball of the ball valve is seated on the slant enlarged portion, and wherein the orifice has a bleeding channel formed on an inner circumferential surface thereof so as to fluidically communicate the communication path and the discharge portion with each other even when the ball of the ball valve is seated on the slant enlarged portion.  
      It is preferable that the bleeding channel includes a groove formed on the slant enlarged portion.  
      Moreover, it is preferable that the bleeding channel includes a groove or a concave formed on the ball side, which is in contact with the slant enlarged portion.  
      Furthermore, it is preferable that the orifice includes a straight portion formed on the discharge portion side, a diameter of the straight portion is within the range of 2.6 mm to 3.1 mm, and a diameter of the ball of the ball valve is within the range of 3.1 mm to 3.5 mm.  
      In addition, it is preferable that the bleeding channel has two to twelve grooves.  
      Additionally, it is preferable that a sectional area of the entire passageway of the grooves is corresponded to a sectional area of a circle, which has a diameter ranging 0.3 mm to 0.8 mm. The diameter is an equivalent diameter of the circle when a sectional area of the entire passageway of the grooves is converted into a circle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a structural view showing an automotive vehicle to which a dual air conditioner is applied;  
       FIG. 2  is a sectional view of a prior art expansion valve for a prior art rear seat air conditioner;  
       FIG. 3  is a graph showing a change in an oil circulation rate by time when operation of the prior art rear seat air conditioner is stopped;  
       FIG. 4  is a sectional view of an expansion valve for a rear seat air conditioner according to the present invention;  
       FIG. 5  is a bottom enlarged view showing an example of an orifice of the expansion valve of  FIG. 4 ;  
       FIG. 6  is a bottom enlarged view showing another example of the orifice of the expansion valve of  FIG. 4 ;  
       FIG. 7  is a perspective view of a ball of a ball valve of the expansion valve according to the present invention; and  
       FIGS. 8 and 9  are graphs showing changes in an oil circulation rate by time when operation of the rear seat air conditioner to which the expansion valve of the present invention is applied is stopped. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Reference will be now made in detail to the preferred embodiment of the present invention with reference to the attached drawings. Terms and words used in this specification and claims should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the inventor can properly define the concept of words to explain the inventor&#39;s invention in the best way.  
       FIG. 4  shows an expansion valve for a rear seat air conditioner of an automotive vehicle according to the present invention.  
      The expansion valve  100  for the rear seat air conditioner according to the present invention includes a valve block  110 , a low-pressure refrigerant channel  120 , a high-pressure refrigerant channel  130 , a temperature sensing bulb  180 , a pressure delivery bar  170 , and a ball valve  160 .  
      The low-pressure refrigerant channel  120  is horizontally mounted on the upper end part of the valve block  110  to connect an outlet of a rear evaporator  36  (see  FIG. 1 ) constituting the rear seat air conditioner  30  (see  FIG. 1 ) with a compressor  12  (see  FIG. 1 ).  
      In addition, the high-pressure refrigerant channel  130  is horizontally mounted on the lower end part of the valve block  110  to connect an inlet of the rear evaporator  36  with a condenser  14  or a receiver dryer  16  (see  FIG. 1 ). The high-pressure refrigerant channel  130  includes an entrance portion  132  connected with the condenser  14  or the receiver dryer  16  for introducing condensed refrigerant, a discharge portion  134  connected to the inlet of the rear evaporator  36 , and an orifice  136  for connecting the entrance portion  132  and the discharge portion  134  with each other.  
      Moreover, the temperature sensing bulb  180  is mounted on the top of the valve block  110  and connected with the pressure delivery bar  170  liftably mounted across the low-pressure refrigerant channel  120  and the orifice  136  of the high-pressure refrigerant channel  130 . In this instance, a diaphragm  182  mounted below a gas chamber  184  inside the temperature sensing bulb  180  is connected with the pressure delivery bar  170 . Therefore, temperature of refrigerant flowing in the low-pressure refrigerant channel  120  is transferred to the gas chamber  184  through the pressure delivery bar  170 , and so, the pressure delivery bar  170  is liftable while the diaphragm  182  is vertically moved according to a pressure change of the gas chamber  184 .  
      The ball valve  160  is to adjust an opening degree of the orifice  136  in link with the pressure delivery bar  170 , and mounted on a communication path  150  passing through the orifice  136  and the entrance portion  132 . The ball valve  160  is arranged in close with the bottom of the lower end of the pressure delivery bar  170 , and includes a ball  162  for adjusting the opening degree of the orifice  136  and a spring  164  for elastically supporting the ball  162  by interposing a support plate  166  between the ball  162  and the spring  164 .  
      The expansion valve  100  for the rear seat air conditioner according to the present invention can circulate refrigerant between the rear seat air conditioner  30  and the compressor  12  even though the ball  162  of the ball valve  160  is seated on the orifice  136  in a state where only a front seat air conditioner  10  (see  FIG. 1 ) is operated stopping the operation of the rear seat air conditioner  30  (see  FIG. 1 ), whereby oil contained in refrigerant of the rear seat air conditioner  30  can be returned to the compressor  12  smoothly. To this end, a bleeding channel  140  is provided on the inner circumferential surface of the orifice  136  for fluidically communicating the communication path  150  and the discharge portion  134  with each other.  
      As shown in FIGS.  4  to  6 , the bleeding channel  140  includes a number of grooves  142  formed on the inner peripheral surface of the orifice  136  to fluidically communicate the communication path  150  and the discharge portion  134  with each other.  
      In more concrete, the orifice  136  includes a straight portion  136   b  of the discharge portion  134  side, and a slant enlarged portion  136   a  of the communication path  150  side on which the ball  162  of the ball valve  160  is seated. In this instance, it is preferable that three or twelve grooves  142  are formed on the slant enlarged portion  136   a  at predetermined intervals to fluidically communicate the communication path  150  with the straight portion  136   b  even though the ball  162  of the ball valve  160  is seated on the slant enlarged portion  136   a . Therefore, even though the ball  162  of the ball valve  160  is seated on the slant enlarged portion  136   a , the communication path  150  can be fluidically communicated with the discharge portion  134  through the grooves  142  and the straight portion  136   b.    
       FIG. 5  shows an example that three grooves  142  are formed, and  FIG. 6  shows another example that six grooves  142  are formed, but it is preferable that six grooves  142  are formed in consideration of flow-ability and process-ability of refrigerant. The grooves  142  can be formed, for example, by a notching method.  
      Furthermore, it is preferable that a diameter of the straight portion  136   b  of the orifice is within the range of 2.6 mm to 3.1 mm and a diameter of the ball  162  of the ball valve  160  is within the range of 3.1 mm to 3.5 mm.  
      Additionally, it is preferable that a sectional area of the bleeding channel  140 , namely, a sectional area of the entire passageway of the grooves  142  corresponds to a sectional area of a circle, which has a diameter of 0.3 mm to 0.8 mm.  
      Meanwhile, in this embodiment, the grooves  142  of the bleeding channel  140  are formed on the inner peripheral surface of the slant enlarged portion  136   a , but may be formed on the outer peripheral surface of the ball  162 , which is in contact with the slant enlarged portion  136   a  as shown in  FIG. 7 . In  FIG. 7 , the grooves  162   a  are formed on the outer peripheral surface of the ball  162  in a lattice form, but may be formed in one of various shapes. In addition, not shown in the drawings, but the bleeding channel  140  may have a concave (not shown) formed on the outer peripheral surface of the ball  162 .  
      Moreover, the ball  162  of the ball valve  160  may be formed in a spherical or conical shape or one of other shapes.  
      Next, the operation of the expansion valve for the rear seat air conditioner of the automotive vehicle according to the present invention will be described.  
      In case that the front and rear seat air conditioners  10  and  30  (see  FIG. 1 ) constituting a dual air conditioner are all operated, when refrigerant is introduced from the receiver dryer  16  into the entrance portion  132  of the high-pressure refrigerant channel  130 , the opening degree of the orifice  136  is adjusted according to rise and fall of the ball  162  of the ball valve  160  due to the vertical movement of the pressure delivery bar  170 . Therefore, refrigerant introduced into the entrance portion  132  can be supplied to the rear evaporator  36  while controlling its flow rate after passing through the communication path  150 , the orifice  136  and the discharge portion  134  in order.  
      A structure for adjusting the opening degree of the orifice  136  will be described in more detail. When temperature of refrigerant discharged from the rear evaporator  36  to the low-pressure refrigerant channel  120  drops, temperature of refrigerant is transferred to the temperature sensing bulb  180  through the pressure deliver bar  170 . Therefore, temperature of the gas chamber  184  inside the temperature sensing bulb  180  drops and gas contained inside the gas chamber  184  is condensed, so that pressure of the gas chamber  184  is lowered and volume of the gas chamber  184  is reduced, whereby the diaphragm  182  mounted inside the temperature sensing bulb  180  is displaced upwardly. The pressure delivery bar  170  is moved upwardly in link with the displacement of the diaphragm  182  and the ball  162  of the ball valve  160  is moved upwardly by elasticity of the spring  164 , whereby the opening degree of the orifice  136  is reduced and the flow rate of refrigerant is reduced. Contrariwise, when temperature of refrigerant flowing inside the low-pressure refrigerant channel  120  rises, the pressure delivery bar  170  moves downwardly and the opening degree of the orifice  136  is increased, whereby the flow rate of refrigerant is increased.  
      As described above, after the front and rear seat air conditioners  10  and  30  of the dual air conditioner are all operated, when only the front seat air conditioner  10  is operated stopping the operation of the rear seat air conditioner  30  in case that there is no passenger on the rear seat of the automotive vehicle, generally, the orifice  136  is intercepted and refrigerant cannot be circulated between the compressor  12  and the rear seat air conditioner  30  and is stagnated. Therefore, oil contained in refrigerant located in the stagnated area is not supplied to the compressor  12 . However, in the present invention, refrigerant of a predetermined flow rate can be circulated between the compressor  12  and the rear seat air conditioner  30  through the bleeding channel  140  having the grooves  142  formed on the slant enlarged portion  136   a  of the orifice  136 .  
      That is, refrigerant of the entrance portion  132  can be flown to the discharge portion  134  after passing through the straight portion  136   b  of the orifice  136  through the communication path  150  and the bleeding channel  140 , whereby refrigerant of the predetermined flow rate can be circulated between the rear seat air conditioner  30  and the compressor  12  smoothly.  
      As described above, when refrigerant of the predetermined flow rate can be circulated between the rear seat air conditioner  30  and the compressor  12 , oil contained in refrigerant in the area can be supplied to the compressor  12  smoothly so as to prevent a lack of lubrication of the compressor  12 .  
       FIGS. 8 and 9  are graphs showing changes in an oil circulation rate by time when operation of the rear seat air conditioner to which the expansion valve of the present invention is applied is stopped.  FIG. 8  shows a case that the diameter of the bleeding channel  140  is 0.3 mm, and  FIG. 9  shows a case that the diameter of the bleeding channel  140  is 0.4 mm. As you can see from  FIGS. 8 and 9 , even though operation of the rear seat air conditioner  30  is stopped, oil is circulated through the bleeding channel  140 , so that oil can be supplied to the compressor  12  smoothly and uniformly without reduction of the oil circulation rate as time goes.  
      The following Table 1 is to compare the oil circulation rate between the expansion valve according to the present invention and the prior art expansion valve to which the bleeding channel is not applied in case of a dual mode that the front and rear seat air conditioners are all operated and in case of a single mode that only the front seat air conditioner is operated stopping the operation of the rear seat air conditioner. For your reference, in Table 1, a dimension of the bleeding channel is indicated by converting a dimension corresponding to a sectional area of the entire passageway of the grooves  142  into a diameter of a circle.  
                               TABLE 1                                      Bleeding   Operation   Oil circulation rate (%)                                 Division   channel (mm)   period (HR)   Dual   Single               Prior art   None   1   8.0   3.4               2       2.2               4       1.8       Present   0.6   1   8.2   8.8       invention 1       2       8.9       Present   0.5   1   8.0   7.8       invention 2       2       7.9       Present   0.4   1   8.4   7.7       invention 3       2       7.7       Present   0.3   1   8.3   6.7       invention 4       2       6.7                  
 
      As indicated in the above Table 1, in the single mode, the oil circulation rate of the present invention was still higher than the prior art expansion valve, and did not drop even though time passed. In addition, not shown in Table 1, but even when refrigerant of the predetermined flow rate is circulated between the compressor and the rear seat air conditioner, cooling performance did not drop even though time passed.  
      As described above, the expansion valve for the rear seat air conditioner of the automotive vehicle according to the present invention can circulate refrigerant between the compressor and the rear seat air conditioner since refrigerant of the predetermined flow rate introduced into the entrance portion  132  from the receiver dryer can flow to the discharge portion  134 , which is connected to the rear evaporator, through the bleeding channel  140  formed in the expansion valve even when operation of the rear seat air conditioner is stopped but only the front seat air conditioner is operated. Therefore, the present invention can smoothly supply oil contained in refrigerant between the compressor and the rear seat air conditioner to the compressor, thereby preventing bad influences on durability of the compressor, for example, sticking of the compressor due to a lack of lubrication as operation time of the compressor passes, and extending a lifespan of the compressor by protecting the compressor. In addition, the present invention can reduce operational noise of the compressor by raising a lubricating effect.  
      While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.