Patent Publication Number: US-2007123158-A1

Title: Louver driver for swing register

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a louver driver used in a swing register for swinging louvers that are pivotally supported at an outlet of a duct for conducting air from an air conditioner, thereby changing the course of the airflow.  
      A swing register is typically used is vehicle air conditioners. A swing register has vertical louvers and lateral louvers at the outlet of the airflow passage of an air conditioner. The swing register swings vertical louvers by means of an actuator to change the direction of the airflow. Conventionally, as disclosed in Japanese Patent No. 3187719, Japanese Patent No. 332409, Japanese Laid-Open Patent Publication No. 2002-2211232, and Japanese Laid-Open Utility Model Publication No. 7-10188, a motor is typically used as the actuator for driving the louvers of such a swing register.  
       FIG. 7  shows one example of the louver driver of a conventional swing register that uses a DC motor as the actuator for driving the louvers. As shown in  FIG. 7 , an output shaft  50   a  of the DC motor  50 , which generates axial force, is coupled to a reduction mechanism  51  constructed by gears. A final gear  51   a  of the reduction mechanism  51  is coupled to a crank mechanism  52  that converts rotation into swinging motion. A wire rod  54  is coupled to the crank mechanism  52 . A rack  53  is fixed to the distal end of the wire rod  54  such that the wire rod  54 , together with the rack  53 , reciprocates. A first pinion  55   a  is connected to the crank mechanism  52  through the rack  53 . A second pinion  55   b  is rotatably supported to be coaxial with the rotary shaft of the first pinion  55   a . The second pinion  55   b  is meshed with a gear  56 , to which a swing shaft  57   a  of a louver  57  is fixed. The swing shaft  57   a  integrally pivots with the gear  56 . The first and second pinions  55   a ,  55   b  are pressed against each other by a spring, so that rotational force can be transmitted therebetween by means of frictional force. Also, the first and second pinions  55   a ,  55   b  are configured as a clutch mechanism that, when an occupant of the vehicle manually swings the louver  57 , permits relative rotation between the pinions  55   a ,  55   b.    
      In a conventional swing register as described above, which uses a motor as a louver driving actuator, noises from the motor and the reduction mechanism leak into the passenger compartment. It is therefore necessary to take measures for insulating noises. For example, a sound insulation member made of, for example, rubber, is put around the motor. Alternatively, the motor and the reduction mechanism are contained in a case. These configurations increase the number of components. As a result, the manufacturing costs and the size of the device are increased.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an objective of the present invention to provide a swing register that readily and reliably reduces noises generated when louvers are operated.  
      In accordance with one aspect of the present invention, a louver driver used in a swing register that swings louvers that are pivotally supported at an airflow passage of an air conditioner, thereby changing the course of the airflow, is provided. The louver driver includes a shape-memory alloy member that is extended and contracted when electrically heated. The shape-memory alloy member and the louver are coupled to each other such that the louver is swung in accordance with extension and contraction of the shape-memory alloy.  
      Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:  
       FIG. 1  is a plan view illustrating the overall structure of a louver driver in a swing register according to one embodiment of the present invention;  
       FIG. 2  is a diagrammatic view showing the electrical circuit of the louver driver of the swing register according to the embodiment of  FIG. 1 ;  
       FIG. 3  is a graph of the temperature versus strain of the shape-memory alloy used in the embodiment of  FIG. 1 ;  
       FIGS. 4A and 4B  are plan views schematically showing operation of the louver driver of the swing register according to the embodiment of  FIG. 1 ;  
       FIGS. 5A and 5B  are plan views showing operation of a current shutoff mechanism used in the embodiment of  FIG. 1 ;  
       FIG. 6  is a plan view illustrating the overall structure of a louver driver in a swing register according to another embodiment of the present invention; and  
       FIG. 7  is a plan view illustrating the overall structure of a prior art louver driver. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A louver driver of a swing register according to one embodiment of the present invention will be described with reference to FIGS.  1  to  5 B.  
      The louver driver of the swing register according to this embodiment is located at the outlet of airflow passage (duct) of a vehicle air conditioner. Vertical and lateral louvers are provided at the outlet. The louver driver laterally swings the vertical louvers to change the direction of airflow into the passenger compartment.  
      In this embodiment, the swinging motion of the vertical louvers in the swing register is achieved by means of contraction of a shape-memory alloy (SMA) caused by electrically heating the alloy. As the shape-memory alloy, thin wires of a titanium-nickel based alloy are used. In this louver driver, when the vertical louvers are moved by using contraction of the shape-memory alloy caused by electrically heating the alloy, the alloy produces no noise. Therefore, without any special noise reduction measures, the noise of the operation of the vertical louvers is reduced. As a result, no sound insulating member is required. This reduces the weight, the occupied space, and the number of components of the louver driver.  
       FIG. 1  shows the entire construction of the louver driver of the swing register according to the present embodiment. In the following, a side of the louver driver facing the outlet of an airflow passage (duct) of a vehicle air conditioner is referred to as a front side, and the opposite side is referred to as a rear side.  
      At the outlet of an air flow passage (duct) of a vehicle air conditioner, lateral louvers (not shown) are provided. The lateral louvers are supported to be vertically swingable. Also, at the outlet, vertical louvers  10   a  to  10   e , the number of which is five in this embodiment, are provided. Each vertical louver  10   a  to  10   e  is laterally swingable about a swing shaft  11 . The slat-like vertical louvers  10   a  to  10   e  include a main louver  10   c  provided at the center and follower louvers  10   a ,  10   b ,  10   d , and  10   e  provided at both sides of the main louver  10   c . Each of the louvers  10   a  to  10   e  has a swing shaft  11 . The main louver  10   c  and the follower louvers  10   a ,  10   b ,  10   d ,  10   e  are mechanically coupled to one another by means of a link mechanism  12 , so that the vertical louvers  10   a  to  10   e  are synchronously swingable.  
      The swing shaft  11  of the main vertical louver  10   c  is fixed to a rotor  13  such that the swing shaft  11  and the rotor  13  rotate integrally. Ends of two wires made of titanium-nickel based shape-memory alloy, that is, a left SMA wire  14 L and a right SMA wire  14 R, are fixed to a circumferential surface of the substantially cylindrical rotor  13 . The left SMA wire  14 L is wound about the circumferential surface of the rotor  13  counterclockwise as viewed in  FIG. 1  from the fixed end, and is then drawn rearward and leftward from the rotor  13 . On the other hand, the right SMA wire  14 R is wound about the circumferential surface of the rotor  13  clockwise as viewed in  FIG. 1  from the fixed end, and is then drawn rearward and rightward from the rotor  13 . The rotation range of the rotor  13  is properly limited by a stopper (not shown).  
      The left and right SMA wires  14 L,  14 R drawn from the rotor  13  are wound about fixed pulleys  15 L,  15 R, which are located rearward and leftward and rightward of the rotor  13 , respectively. The left and right SMA wires  14 L,  14 R are drawn rearward from the fixed pulleys  15 L,  15 R are wound about movable pulleys  16 L,  16 R for preventing looseness, respectively. The movable pulleys  16 L,  16 R are rotatably supported at ends of swing arms  18 L,  18 R, and located rearward of the fixed pulleys  15 L,  15 R. The swing arms  18 L,  18 R are swingably supported substantially at the center. Coil springs  19 L,  19 R in an extended state are fixed to ends of the swing arms  18 L,  18 R opposite to the ends to which the movable pulleys  16 L,  16 R are supported. The coil springs  19 L,  19 R constantly urge the swing arms  18 L,  18 R in directions to pull the movable pulleys  16 L,  16 R backward. When the SMA wires  14 L,  14 R are extended, the coil springs  19 L,  19 R swing the swing arms  18 L,  18 R to pull the movable pulleys  16 L,  16 R backward. As a result, the total length of each of the SMA wires  14 L,  14 R is extended, which prevents the looseness of the SMA wires  14 L,  14 R. Stoppers  17 L,  17 R are located forward of the swing arms  18 L,  18 R, respectively. Contact between the stoppers  17 L,  17 R and the swing arms  18 L,  18 R limits the range of swinging of the swing arms  18 L,  18 R in a direction pushing the movable pulleys  16 L,  16 R forward.  
      The ends of the SMA wires  14 L,  14 R, which are drawn forward from the looseness prevention movable-pulleys  16 L,  16 R, are fixed to a swing arms  21 L,  21 R of current shutoff mechanisms  20 L,  20 R. The current shutoff mechanisms  20 L,  20 R are used for forcibly shutting off the supply of current when the SMA wires  14 L,  14 R are excessively heated. The swing arms  21 L,  21 R of the current shutoff mechanisms  20 L,  20 R are swingably supported substantially at the center. The ends of the SMA wires  14 L,  14 R are fixed to ends of the swing arms  21 L,  21 R. Coil springs  23 L,  23 R are fixed to the other ends of the swing arms  21 L,  21 R in an extended state. Movable electrodes  24 L,  24 R project from the front side of the ends of the swing arms  21 L,  21 R to which the ends of the SMA wires  14 L,  14 R are fixed. The swing arms  21 L,  21 R are constantly urged to push the fixed ends of the SMA wires forward by the coil springs  23 L,  23 R. Accordingly, the movable electrodes  24 L,  24 R are pressed against plate-like fixed electrodes  25 L,  25 R, which are fixed at positions forward of the swing arms  21 L,  21 R.  
       FIG. 2  shows the electrical configuration of the louver driver of the swing register according to the present embodiment. Currents to the SMA wires  14 L,  14 R are controlled by a central processing unit (CPU)  30 , or an electricity supply control unit, shown in  FIG. 2 . The CPU  30  is electrically connected to a swing register switch located in the passenger compartment, and receives command signals from an air conditioner controller that controls the entire vehicle air conditioner. Automatic swinging of the vertical louvers  10   a  to  10   e  (see  FIG. 1 ) by the louver driver is permitted when the swing register switch is closed (turned on), and is inhibited when the swing register switch is opened (turned off). The air conditioner controller determines the temperature and the flow rate of airflow in accordance with detection results of the outside temperature and the temperature in the passenger compartment and with manipulation by an occupant. The air conditioner controller also determines the mode of swinging of the vertical louvers  10   a  to  10   e  (see  FIG. 1 ) and commands the CPU  30 , accordingly.  
      The CPU  30  is also connected to drive circuits  33 L,  33 R of the SMA wires  14 L,  14 R. The drive circuit  33 L,  33 R supply current to the SMA wires  14 L,  14 R based on commands from the CPU  30 , respectively. The SMA wires  14 L,  14 R are each electrically connected to the drive circuits  33 L,  33 R through contact points of the movable electrodes  24 L,  24 R and the fixed electrodes  25 L,  25 R of the current shutoff mechanisms  20 L,  20 R, respectively. The SMA wires  14 L,  14 R are grounded at the ends fixed to the rotor  13  (see  FIG. 1 ).  
      The louver driver of the swing register as described above uses contraction of the SMA wires  14 L,  14 R made of titanium-nickel based alloy caused by electrical heating, thereby swings the vertical louvers  10   a  to  10   e . The configuration of the material used for the SMA wires  14 L,  14 R is anisotropic such that the deformation when regaining the original geometry is limited in the lengthwise direction, that is, the direction of extension and contraction. When cooled, the SMA wires  14 L,  14 R are relaxed and can be extended by external pulling force. When heated, the SMA wires  14 L,  14 R contract to regain the original geometry and hardened.  FIG. 3  shows one example of a graph of temperature versus strain of the SMA wires  14 L,  14 R. As shown in  FIG. 3 , the SMA wires  14 L,  14 R start contracting approximately at 80° C. when heated, and start being relaxed and extending approximately at 75° C. when cooled. The temperature at which the SMA wires  14 L,  14 R start contracting and the temperature at which the SMA wires  14 L,  14 R start being relaxed and extending are adjustable to a certain degree by quality governing of the alloy. The SMA wires  14 L,  14 R have a relatively great electrical resistance, and are readily heated by application of a current. The SMA wires  14 L,  14 R, which are made of a titanium-nickel based shape-memory alloy, have been developed as wires that are capable of repeatedly and stably generating maximum dynamic strains of 5% or greater with respect to the entire lengths when regaining the original geometry through electrical heating.  
      Next, the principle of operation of the swing register will be described. The louver driver of the swing register swings the vertical louvers  10   a  to  10   e  using contraction of the SMA wires  14 L,  14 R caused by electrical heating. When only the left SMA wire  14 L is electrically heated, the left SMA wire  14 L contracts accordingly as shown in  FIG. 4A . At this time, the right SMA wire  14 R, which is in a non-heated state, or cooled state, is relaxed and elastically extendible by pulling. The rotor  13  is thus rotated counterclockwise. As a result, the vertical louver  10   c , which is fixed to the swing shaft  11  so as to be integrally movable with the rotor  13 , is swung counterclockwise as viewed in the drawing. In contrast, when only the right SMA wire  14 R is electrically heated, the right SMA wire  14 R contracts accordingly as shown in  FIG. 4B . At this time, the left SMA wire  14 L, which is in a cooled state, is relaxed and elastically extendible by pulling. The rotor  13  is thus rotated clockwise. As a result, the vertical louver  10   c , which is fixed to the swing shaft  11  so as to be integrally movable with the rotor  13 , is swung clockwise as viewed in the drawing. In this manner, by alternately supplying current to the left and right SMA wires  14 L,  14 R, the vertical louver  10   c  is swung alternately leftward and rightward periodically. By continuously supplying the current to either of the SMA wires  14 L,  14 R such that the contraction strain rate is maintained at an appropriate value, the swing angle of the vertical louver  10   c  is maintained. Accordingly, the direction of the airflow from the duct outlet is fixed.  
      In the manner described above, the louver driver of the swing register uses the SMA wires  14 L,  14 R as a driving source. When the SMA wires  14 L,  14 R are supplied with excessive current, the temperature of the SMA wires  14 L,  14 R can surpass an upper limit of a proper temperature range. If such an excessive heated state continues, permanent strain is caused in the SMA wires  14 L,  14 R by their own contraction force, which degrades the geometry regaining property. As a result, the vertical louvers  10   a  to  10   e  will be unable to swing properly. Therefore, in this embodiment, when the SMA wires  14 L,  14 R excessively contract due to excessive heating, the current shutoff mechanisms  20 L,  20 R forcibly shut off the current so that the excessively heated state does not continue.  
      An example of the operation of the current shutoff mechanism  20 L,  20 R will now be described with reference to  FIGS. 5A and 5B . Although  FIGS. 5A and 5B  show the operation of only the left current shutoff mechanism  20 L, the operation of the current shutoff mechanism  20 R operates in the same manner.  
      In the non-heated state, the movable electrode  24 R provided at one end of the swing arm  21 R of the current shutoff mechanisms  20 R is pressed against the plate-like fixed electrode  25 R by the force of the coil spring  23 R fixed to the other end of the swing arm  21 R ( 21 L) in the extended state. The current path of the SMA wire  14 R is maintained by the contact between the movable electrode  24 R and the fixed electrode  25 R. The moment applied to the swing arm  21 R by the force of the coil spring  23 R is set slightly less than the moment applied to swing arm  21 R by the tension of the SMA wire  14 R when the tension is at the upper limit in the allowable range (maximum allowable tension). Therefore, in the non-heated state, the contraction of the SMA wire  14 R by the electrical heating is not totally cancelled by contraction of the coil spring  23 R and the accompanying swinging motion of the swing arms  21 R.  
      On the other hand, when the SMA wire  14 R excessively contracts due to excessive heating, rotation of the rotor  13  (refer to  FIG. 1 ) is restricted by the stopper so that further contraction of the SMA wire  14 R is limited. Accordingly, the tension Ft of the SMA wire  14 R is increased. When the tension Ft is increased to reach a value near the maximum allowable tension, the swing arm  21 R is swung against the force of the coil spring  23 R as shown in  FIG. 5B , so that the movable electrode  24 R separates from the fixed electrode  25 R. As a result, the current path to the SMA wire  14 R is cut, and the supply of current is forcibly shut off.  
      The louver driver of the swing register according to the above described embodiment has the following advantages.  
      (1) In the above embodiment, the vertical louvers  10   a  to  10   e  are driven by using the contraction of the shape-memory alloy (the SMA wires  14 L,  14 R), which generates no sound when operating, through electrical heating. Therefore, noise generated during the operation of the vertical louvers  10   a  to  10   e  is readily and reliably reduced. As a result, no sound insulating member is required. This reduces the weight and the occupied space the louver driver.  
      (2) When the SMA wires  14 L,  14 R are excessively heated and contract excessively, the contraction force separates the movable electrodes  24 L,  24 R from the fixed electrodes  25 L,  25 R, so that the supply of current to the SMA wires  14 L,  14 R is forcibly cut off. Thus, the geometry regaining property of the SMA wires  14 L,  14 R is prevented from deteriorating due to excessive heating. Accordingly, the operation property of the louver driver of the swing register is prevented from being degraded.  
      (3) The SMA wires  14 L,  14 R are wound about the circumferential surface of the rotor  13 , which is coupled to and rotates integrally with the swing shaft  11  of the vertical louver  10   c , and the ends of the SMA wires  14 L,  14 R are fixed to the circumferential surface of the rotor  13 . This permits contraction of the SMA wires  14 L,  14 R to be directly converted into rotation of the swing shaft  11 . Therefore, the vertical louvers  10   a  to  10   e  can be readily swung without providing a linear-to-rotary conversion mechanism such as a rack-and-pinion.  
      (4) When the vertical louver  10   c  is forcibly and manually swung by an occupant of the vehicle, such movement is absorbed by the elastic deformation of the SMA wires  14 L,  14 R. Thus, a clutch mechanism that is required for a conventional louver driver using a DC motor can be omitted.  
      (5) The swinging motion of the vertical louvers  10   a  to  10   e  are easily and accurately adjusted by controlling the current supplied to the left-and right two SMA wires  14 L,  14 R.  
      The above embodiment may be modified as follows.  
      In the illustrated embodiment, leftward and rightward swinging motion of the vertical louvers  10   a  to  10   e  are achieved by contraction of the left and right SMA wires  14 L,  14 R due to electrical heating. However, it may be configured that either one of the leftward and rightward swinging motions of the vertical louvers  10   a  to  10   e  is achieved by contraction of an SMA wire, and the swinging motion in the other direction is achieved by the force of a spring.  FIG. 6  illustrates one example of such a configuration. In this louver driver, the right SMA wire  14 R is replaced by a wire  40 . The wire  40  is made of a normal metal that is not shape-memory alloy. One end of the wire  40  is wound about and fixed to the circumferential surface of the rotor  13 . The other end of the wire  40 , which extends from the rotor  13 , is coupled to a coil spring  41 . The other end of the coil spring  41  is fixed to the vehicle body. The force of the coil spring  41  is sufficiently smaller than the contraction force generated by the SMA wire  14 L by electrical heating. In this louver driver of the swing register, when the SMA wire  14 L contracts through electrical heating, the rotor  13 , together with the louver  10   c , is rotated counterclockwise against to the force of the coil spring  41 . When the supply of current is shut off to cool the SMA wire  14 L, the SMA wire  14 L is relaxed and extended by the force of the coil spring  41 , which causes the rotor  13 , together with vertical louver  10   c , to rotate clockwise. This configuration permits the vertical louvers  10   a  to  10   e  to be swung in the similar manner as in the above illustrated embodiment. In the. configuration of  FIG. 6 , the vertical louvers  10   a  to  10   e  are swung leftward by contraction of the SMA wire  14 L and swung rightward by the extension of the SMA wire  14 L by the force of the coil spring  41  when the SMA wire  14 L is cooled, and the SMA wire  14 L generates no sound during operation. Therefore, noise generated during the operation of the vertical louver  10   c  is readily and reliably reduced as in the above illustrated embodiment.  
      In the embodiment of FIGS.  1  to  5 B, the current shutoff mechanisms  20 L,  20 R are provided for forcibly shutting off the supply of current to prevent the SMA wires  14 L,  14 R from being excessively heated. However, the current shutoff mechanisms  20 L,  20 R may be omitted in the case where prevention circuits are provided for preventing excessive current to the SMA wires  14 L,  14 R.  
      In the embodiment of FIGS.  1  to  5 B, the rotor  13  is integrated with the swing shaft  11  of the vertical louver  10   c . However, the rotor  13  may be coupled to the swing shaft  11  of the rotor  13  by means of a power transmission mechanism such as gears in such a manner that the rotor  13  rotates synchronously with the swing shaft  11 .  
      In the embodiment of FIGS.  1  to  5 B, the SMA wires  14 L,  14 R are wound about and fixed to the circumferential surface of the rotor  13 , so that linear motion caused by contraction of the SMA wires  14 L,  14 R is directly converted into rotation of the rotor  13  and to swinging motion of the vertical louver  10   c . However, the linear-to-swing conversion may be achieved by another mechanism such as a rack-and-pinion. In such a case, the rack is caused to reciprocate by contraction of the SMA wires  14 L,  14 R, and is meshed with a pinion that is coupled to the swing shaft  11  of the vertical louver  10   c  to synchronously rotate with the swing shaft  11 , so that the vertical louver  10   c  is swung.  
      In the embodiment of FIGS.  1  to  5 B, the vertical louver  10   c  is swung by means of the SMA wires  14 L,  14 R made of a shape-memory alloy. However, the vertical louver  10   c  may be swung by a shape-memory alloy formed into another shape such as a coil spring. That is, as long as a shape-memory alloy that contracts due to electrical heating is used, and the metal and louvers are coupled to each other such that the louvers are swung due to contraction of the metal, the present invention may be embodied as any type of louver driver in a swing register that generates significantly reduced noise.  
      As long as the shape-memory alloy used in the embodiments has a sufficiently great amount of geometry regaining and contraction force, any shape-memory alloy other than titanium-nickel based shape-memory alloy may be used as the driving source of the louvers.  
      The louver driver of the swing register according to the present invention may be applied as a mechanism for vertically swinging the lateral louvers.