Abstract:
A heat exchange device includes a thermoactuator usable over a long period of time is disclosed. The thermoactuator includes a case. In the case, there is formed a stopper providing an advancement limit of a rod to limit an opening degree of a valve of the thermoactuator.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a heat exchange device having a thermoactuator mounted thereon. 
       BACKGROUND OF THE INVENTION 
       [0002]    A thermoactuator is a driving part for advancing or retreating a rod on the basis of a temperature change. Such a thermoactuator is mounted on, e.g., a heat exchange device. The heat exchange device is known as, e.g., a waste heat recovery device. The thermoactuator mounted on the heat exchange device advances the rod when a temperature of a medium is high. The rod is forced to be retreated by an urging force of a return spring incorporated in the thermoactuator when the medium temperature decreases. 
         [0003]    The waste heat recovery device has a heat recovery passage for recovery of heat of an exhaust gas, and a bypass passageway bypassing the heat recovery passage. A flow path for an exhaust gas is switched by a valve provided in the waste heat recovery device. To this valve is connected a thermoactuator. The valve is activated by activation of a rod of the thermoactuator. The thermoactuator is connected to a heat exchanger disposed in a heat recovery passage and activated by a temperature of a medium flowing through the heat exchanger. 
         [0004]    The thermoactuator used in the manner discussed above is known from, for example, JP-A-2010-71454. The thermoactuator disclosed in JP-A-2010-71454 is shown in  FIG. 20  hereof. 
         [0005]    As shown in  FIG. 20 , a thermoactuator  200  includes a case  201  and a temperature-sensitive portion  210  attached to one end of the case  201  for sensing a temperature of surroundings of the case  201  (e.g., a medium temperature). The thermoactuator  200  also includes an actuator rod  203  received in a sleeve  212  of the temperature-sensitive portion  210  for advancing depending upon the temperature sensed by the temperature-sensitive portion  210 . The thermoactuator  200  further includes a rod  204  disposed at a distal end of the actuator rod  203  for moving together with the rod in a left-rear direction of this figure. The thermoactuator  200  further includes a bearing  205  disposed on an outer circumference of a distal end of the rod  204  for guiding the rod  204 , and a return spring  206  for urging the rod  204  in a direction to retreat the rod  204 . 
         [0006]    In the thermoactuator  200 , a metal such as a steel material is used for the case  201 . A resin such as polyimide is used for the bearing  205 . 
         [0007]    A wax  211  is accommodated in the temperature sensitive portion  210 . When a temperature of the wax increases due to a high temperature of the surroundings of the temperature sensitive portion  210 , the wax  211  expands. The expansion of the wax  211  forces the sleeve  211  to be compressed to advance the actuator rod  203 . 
         [0008]    When the temperature of the wax  211  decreases due to a low temperature of the surroundings of the temperature sensitive portion  210 , the wax  211  shrinks. In this case, the rod  204  and the actuator rod  203  are forced to retreat under a force of the return spring  206 . 
         [0009]    The rod  204  is guided by the bearing  205  to move back and forth. As the rod  24  advances and retreats, the bearing  205  slightly wears away. The same goes for the sleeve  212  which the actuator rod  203  contacts. When an amount by which the bearing  205  or the sleeve  212  wears away reaches a predetermined amount, it is necessary to replace the bearing  205  or the sleeve  212 . 
         [0010]    It is necessary to reduce frequency of replacement of the bearing  205  or the sleeve  212  for use of the thermoactuator over a long period of time. 
       SUMMARY OF THE INVENTION 
       [0011]    In view of the foregoing prior art problems, it is an object of the present invention to provide a heat exchange device having a thermoactuator usable over a long period of time. 
         [0012]    According to one aspect of the present invention, there is provided a heat exchange device comprising: a branching portion for introducing an exhaust gas thereinto and dividing the introduced exhaust gas to flow to two fluid passageways; a first fluid passageway extending from the branching portion; a second fluid passageway extending from the branching portion along the first fluid passageway; a heat exchanger attached to the second fluid passageway for recovery of energy from heat of the exhaust gas; a thermoactuator comprising a tubular case, a temperature sensitive portion attached to one end of the case for sensing a temperature of a medium, a piston received in a sleeve in the temperature sensitive portion for advancing by the temperature sensed by the temperature sensitive portion, a rod disposed on a distal end of the piston for advancing by the advancement of the piston, and a return spring accommodated in the case and urging the rod in a direction to retreat the rod; a valve actuated by the thermoactuator for opening and closing the first fluid passageway or the second fluid passageway; and a stopper formed in the case and providing an advancement limit of the rod to limit an opening degree of the valve. 
         [0013]    In the present invention, the stopper providing the advancement limit of the rod is formed within the case. When the rod advances to a predetermined position, the rod abuts on the stopper. The abutment prevents further advancement of the rod. Thus, it is possible to prevent the rod from advancing more than necessary. This prevents unnecessary movement of the rod. It becomes possible to inhibit a bearing from wearing due to the rod contacting the bearing. Further, it becomes possible to prevent unnecessary movement of the piston configured to move together with the rod. This makes it possible to inhibit the sleeve from wearing due to the piston contacting the sleeve. The inhibition of the wear reduces frequency of replacement of components of the thermoactuator, thereby enabling use of the thermoactuator over a long period of time. 
         [0014]    Where the thermoactuator does not have the stopper, the rod can advance in excess of a predetermined amount, in which case the valve can be activated by the thermoactuator to operate in excess of a predetermined amount. Thus, a valve chamber accommodating the valve is required to have a larger size taking the excess movement of the rod into account. In the thermoactuator of the present invention, the excess movement is prevented by the stopper. Thus, it is not necessary to set a large size of the valve chamber, thereby reducing a size of the heat exchange device. 
         [0015]    According to another aspect of the present invention, there is provided A heat exchange device comprising: a branching portion for introducing an exhaust gas thereinto and dividing the introduced exhaust gas to flow to two fluid passageways; a first fluid passageway extending from the branching portion; a second fluid passageway extending from the branching portion along the first fluid passageway; a heat exchanger attached to the second fluid passageway for recovery of energy from heat of the exhaust gas; a thermoactuator comprising a tubular case, a temperature sensitive portion attached to one end of the case for sensing a temperature of a medium, a piston received in a sleeve in the temperature sensitive portion for advancing by the temperature sensed by the temperature sensitive portion, a rod disposed on a distal end of the piston for advancing by the advancement of the piston, and a return spring accommodated in the case and urging the rod in a direction to retreat the rod; a valve actuated by the thermoactuator for opening and closing the first fluid passageway or the second fluid passageway; and a stopper disposed on a center axis of the rod of the thermoactuator, the rod having an advancement limit provided by abutting on the stopper to limit an opening degree of the valve. 
         [0016]    In the heat exchange device according to another aspect of the present invention, the stopper is disposed on the center axis of the rod of the thermoactuator. When the rod advances to a predetermined position, the rod abuts on the stopper. The abutment prevents further advancement of the rod. Thus, it is possible to prevent the rod from advancing more than necessary. This prevents unnecessary movement of the rod. It becomes possible to inhibit a bearing from wearing due to the rod contacting the bearing. Further, it becomes possible to prevent unnecessary movement of the piston configured to move together with the rod. This makes it possible to inhibit the sleeve from wearing due to the piston contacting the sleeve. The inhibition of the wear reduces frequency of replacement of components of the thermoactuator, thereby enabling use of the thermoactuator over a long period of time. 
         [0017]    Where the thermoactuator does not have the stopper, the rod can advance in excess of a predetermined amount, in which case the valve can be activated by the thermoactuator to operate in excess of a predetermined amount. Thus, a valve chamber accommodating the valve is required to have a larger size taking the excess movement of the rod into account. In the thermoactuator of the present invention, the excess movement is prevented by the stopper. Thus, it is not necessary to set a large size of the valve chamber, thereby reducing a size of the heat exchange device. 
         [0018]    According to another aspect of the present invention, there is provided a heat exchange device comprising: a branching portion for introducing an exhaust gas thereinto and dividing the introduced exhaust gas to flow to two fluid passageways; a first fluid passageway extending from the branching portion; a second fluid passageway extending from the branching portion along the first fluid passageway; a heat exchanger attached to the second fluid passageway for recovery of energy from heat of the exhaust gas; a thermoactuator comprising a tubular case, a temperature sensitive portion attached to one end of the case for sensing a temperature of a medium, a piston received in a sleeve in the temperature sensitive portion for advancing by the temperature sensed by the temperature sensitive portion, a rod disposed on a distal end of the piston for advancing by the advancement of the piston, and a return spring accommodated in the case and urging the rod in a direction to retreat the rod; a valve actuated by the thermoactuator for opening and closing the first fluid passageway or the second fluid passageway, the valve being swingable on a valve shaft of the valve; an abutment piece disposed at an end portion of the valve shaft and offset relative to a shaft center of the valve shaft; and a stopper disposed on an orbit of the abutment piece, the rod having an advancement limit provided by abutment of the abutment piece on the stopper to limit an opening degree of the valve. 
         [0019]    In the heat exchange device according to another aspect of the present invention, a pin is disposed at the end portion of the valve shaft and offset relative to the shaft center of the valve shaft, and the stopper is disposed on the orbit of the pin. Advancement of the rod rotates the valve shaft to open the valve. When the valve shaft rotates to a predetermined position, the pin disposed at the end portion of the valve shaft abuts on the stopper. The abutment stops swinging of the valve shaft, preventing further advancement of the rod. Thus, it is possible to prevent the rod from advancing more than necessary. This prevents unnecessary movement of the rod. It becomes possible to inhibit a bearing from wearing due to the rod contacting the bearing. Further, it becomes possible to prevent unnecessary movement of the piston configured to move together with the rod. This makes it possible to inhibit the sleeve from wearing due to the piston contacting the sleeve. The inhibition of the wear reduces frequency of replacement of components of the thermoactuator, thereby enabling use of the thermoactuator over a long period of time. 
         [0020]    Where no stopper is formed, the rod can advance in excess of a predetermined amount, in which case the valve can be activated by the thermoactuator to operate in excess of a predetermined amount. Thus, where no stopper is formed, a valve chamber accommodating the valve is required to have a larger size taking the excess movement of the rod into account. In the present invention, the excess movement of the rod of the thermoactuator is prevented. Thus, it is not necessary to set a large size of the valve chamber, thereby reducing a size of the heat exchange device. 
         [0021]    According to another aspect of the present invention, there is provided a heat exchange device comprising: a branching portion for introducing an exhaust gas thereinto and dividing the introduced exhaust gas to flow to two fluid passageways; a first fluid passageway extending from the branching portion; a second fluid passageway extending from the branching portion along the first fluid passageway; a heat exchanger attached to the second fluid passageway for recovery of energy from heat of the exhaust gas; a valve chamber connected to downstream ends of the first and second fluid passageways, the first and second fluid passageways meeting together at the valve chamber; a thermoactuator comprising a tubular case, a temperature sensitive portion attached to one end of the case for sensing a temperature of a medium, a piston received in a sleeve in the temperature sensitive portion for advancing by the temperature sensed by the temperature sensitive portion, a rod disposed on a distal end of the piston for advancing by the advancement of the piston, and a return spring accommodated in the case and urging the rod in a direction to retreat the rod; a valve accommodated in the valve chamber and actuated by the thermoactuator for opening and closing the first fluid passageway or the second fluid passageway, the valve being swingable on a valve shaft of the valve; and a stopper attached to the valve, the stopper being configured to abut on an inner wall of the valve chamber by a predetermined amount of swinging of the valve, and the rod having an advancement limit provided by the abutment of the stopper on the inner wall of the valve chamber to limit an opening degree of the valve. 
         [0022]    In the heat exchange device according to another aspect of the present invention, the stopper is attached to the valve. Advancement of the rod rotates the valve shaft to swing the valve. When the valve swings to a predetermined position, the stopper abuts on the inner wall of the valve chamber. The abutment stops swinging of the valve, preventing further advancement of the rod. Thus, it is possible to prevent the rod from advancing more than necessary. This prevents unnecessary movement of the rod. It becomes possible to inhibit a bearing from wearing due to the rod contacting the bearing. Further, it becomes possible to prevent unnecessary movement of the piston configured to move together with the rod. This makes it possible to inhibit the sleeve from wearing due to the piston contacting the sleeve. The inhibition of the wear reduces frequency of replacement of components of the thermoactuator, thereby enabling use of the thermoactuator over a long period of time. 
         [0023]    According to another aspect of the present invention, there is provided a heat exchange device comprising: a branching portion for introducing an exhaust gas thereinto and dividing the introduced exhaust gas to flow to two fluid passageways; a first fluid passageway extending from the branching portion; a second fluid passageway extending from the branching portion along the first fluid passageway; a heat exchanger attached to the second fluid passageway for recovery of energy from heat of the exhaust gas; a valve chamber connected to downstream ends of the first and second fluid passageways, the first and second fluid passageways meeting together at the valve chamber; a thermoactuator comprising a tubular case, a temperature sensitive portion attached to one end of the case for sensing a temperature of a medium, a piston received in a sleeve in the temperature sensitive portion for advancing by the temperature sensed by the temperature sensitive portion, a rod disposed on a distal end of the piston for advancing by the advancement of the piston, and a return spring accommodated in the case and urging the rod in a direction to retreat the rod; a valve accommodated in the valve chamber and actuated by the thermoactuator for opening and closing the first fluid passageway or the second fluid passageway, the valve being swingable on a valve shaft of the valve; and a stopper disposed in the valve chamber and on an orbit of the valve, the rod having an advancement limit provided by abutment of the valve on the stopper to limit an opening degree of the valve. 
         [0024]    In the heat exchange device according to another aspect of the present invention, the stopper is attached to the valve chamber. Advancement of the rod rotates the valve shaft to swing the valve. When the valve swings to a predetermined position, the valve abuts on the stopper. The abutment stops swinging of the valve, preventing further advancement of the rod. Thus, it is possible to prevent the rod from advancing more than necessary. This prevents unnecessary movement of the rod. It becomes possible to inhibit a bearing from wearing due to the rod contacting the bearing. Further, it becomes possible to prevent unnecessary movement of the piston configured to move together with the rod. This makes it possible to inhibit the sleeve from wearing due to the piston contacting the sleeve. The inhibition of the wear reduces frequency of replacement of components of the thermoactuator, thereby enabling use of the thermoactuator over a long period of time. 
         [0025]    Preferably, the rod comprises a rod base portion abutting on the distal end of the piston, and a rod body portion formed integrally with the rod base portion, the rod base portion has a diameter larger than a diameter of the rod body portion such that the rod base portion has a stepped portion extending toward the rod body portion, the heat exchange device further comprises a bearing disposed along an outer circumferential surface of the rod body portion, the bearing and the stepped portion circumferentially overlapping, and the stopper is formed by an end of the bearing. When the rod advances to bring the stepped portion into contact with the end of the bearing, further advancement of the rod is prevented. Since the end of the bearing is used as the stopper for the rod, it is possible to provide the advancement limit without increasing the number of the components. 
         [0026]    Preferably, the rod has a rod flange portion projecting from a lateral surface thereof to an outer circumference of the return spring, the case has a projecting portion projecting from an inner circumferential surface thereof toward a center axis of the case, the projecting portion projects to a location circumferentially overlapping the rod flange portion, and the stopper is formed by the projecting portion. When the rod advances to bring the rod flange portion into contact with the projecting portion, further advancement of the rod is prevented. Since the projecting portion is formed along the inner circumferential surface of the case, the projecting portion has a larger circumferential cross-sectional area than the other portions of the case. The larger circumferential cross-sectional area ensures a large area to contact the rod flange portion. Due to the projecting portion having the large area contacting the rod flange portion, a load applied per unit area of the projecting portion is reduced to achieve a prolonged life of the thermoactuator. 
         [0027]    Preferably, the rod comprises a rod base portion abutting on the distal end of the piston, and a rod body portion formed integrally with the rod base portion, the rod base portion has a diameter larger than a diameter of the rod body portion such that the rod base portion has a stepped portion extending toward the rod body portion, the heat exchange device further comprises a guide member extends from an opposite end of the case toward the one end of the case along an inner circumference of the return spring for limiting circumference displacement of the return spring, the guide member and the stepped portion circumferentially overlap, and the stopper is formed by an end of the guide member. When the rod advances to bring the stepped portion into contact with the end of the guide member, further advancement of the rod is prevented. Since the end of the guide member is used as the stopper for the rod, it is possible to provide the advancement limit without increasing the number of the components. 
         [0028]    Preferably, the case has an opposite end defining a bend portion folded over to a location circumferentially overlapping the rod, and the stopper is formed by the bend portion. When the rod advances to bring the distal end of the rod into contact with the bend portion, further advancement of the rod is prevented. Since the end of the case is used as the stopper for the rod, it is possible to provide the advancement limit without increasing the number of the components. 
         [0029]    Preferably, the thermoactuator further comprises a bearing extending from an opposite end of the case toward the one end of the case along an outer circumferential surface of the rod, and a guide member disposed along an outer circumference of the bearing and receives the return spring for limiting circumferential displacement of the return spring. The bearing is made of a resin material, the case is made of a metal material, the guide member comprises a case contact portion contacting an inner circumferential surface of the case, a receiving portion extending from the case contact portion toward a center axis of the rod and receiving the return spring, and a guide portion extending from a distal end of the receiving portion toward the temperature sensitive portion for limiting circumferential displacement of the return spring, and the heat exchange device further comprises a ring-shaped rubber member disposed between the bearing and the guide member and having an urging force to limit displacement of the bearing. That is, a portion of a gap between the bearing and the case is filled with the rubber member through the guide member. Filling the gap between the bearing and the case prevents the bearing from shaking under a low temperature. On the other hand, the resin-made bearing expands more than the metal case under a high temperature. In this case, the rubber member elastically deforms under the expanding force of the bearing. As a result, a load applied to the case can be made smaller than if the bearing makes close contact under a low temperature. 
         [0030]    Preferably, one of the bearing and the guide member has a tapering portion slanting relative to a center axis of the case, and the tapering portion and the rubber member are in contact with each other. Since the tapering portion slants relative to the center axis of the case, an urging force of the rubber member acts in a direction inclined relative to the center axis of the case. That is, the urging force of the rubber member acts in both a direction along the center axis of the case and a circumferential direction of the case. Thus, the gap between the bearing and the case is filled in the axial and circumferential directions, thereby reliably preventing the shaking of the bearing. 
         [0031]    Preferably, the thermoactuator further comprises a bearing extending from an opposite end of the case toward the one end of the case along an outer circumferential surface of the rod. The bearing is made of a resin material, the case is made of a metal material, and the heat exchange device further comprises a ring-shaped rubber member disposed between the bearing and the case and having an urging force to limit displacement of the bearing. Filling a portion of a gap between the bearing and the case with the rubber member prevents the bearing from shaking under a low temperature. On the other hand, the resin-made bearing expands more than the metal case under a high temperature. In this case, the rubber member elastically deforms under the expanding force of the bearing. As a result, a load applied to the case can be made smaller than if the bearing makes close contact under a low temperature. 
         [0032]    Preferably, one of the bearing and the case has a tapering portion slanting relative to a center axis of the case, and the tapering portion and the rubber member are in contact with each other. Since the tapering portion slants relative to the center axis of the case, an urging force of the rubber member acts in a direction inclined relative to the center axis of the case. That is, the urging force of the rubber member acts in both a direction along the center axis of the case and a circumferential direction of the case. Thus, the gap between the bearing and the case is filled in the axial and circumferential directions, thereby reliably preventing the shaking of the bearing. 
         [0033]    Preferably, the rubber member is an O-ring. The O-ring is cheap. That is, measures against the shaking of the bearing can be taken cheaply. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
           [0035]      FIG. 1  is a plan view of a heat exchange device in a first embodiment of the present invention; 
           [0036]      FIG. 2  is a cross-sectional view of a thermoactuator shown in  FIG. 1 ; 
           [0037]      FIG. 3  is an enlarged view of a region  3  of  FIG. 2 ; 
           [0038]      FIGS. 4A and 4B  are views showing operation of the heat exchange device shown in  FIG. 1   
           [0039]      FIGS. 5A and 5B  are views showing operation of the heat exchange device when a rod shown in  FIG. 2  moves to an advancement limit; 
           [0040]      FIGS. 6A and 6   b  are views showing operation of an O-ring shown in  FIG. 3 ; 
           [0041]      FIG. 7  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a second embodiment of the present invention; 
           [0042]      FIG. 8  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a third embodiment of the present invention; 
           [0043]      FIG. 9  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a fourth embodiment of the present invention; 
           [0044]      FIGS. 10A to 10C  are cross-sectional views of a thermoactuator mounted on a heat exchange device in a fifth embodiment of the present invention; 
           [0045]      FIG. 11  is a cross-sectional view of a heat exchange device in a sixth embodiment of the present invention; 
           [0046]      FIG. 12  is a cross-sectional view of a heat exchange device in a seventh embodiment of the present invention; 
           [0047]      FIG. 13  is a cross-sectional view of a heat exchange device in an eighth embodiment of the present invention; 
           [0048]      FIG. 14  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a ninth embodiment of the present invention; 
           [0049]      FIGS. 15A and 15B  are cross-sectional views of a thermoactuator mounted on a heat exchange device in a tenth embodiment of the present invention; 
           [0050]      FIG. 16  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in an eleventh embodiment of the present invention; 
           [0051]      FIG. 17  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a twelfth embodiment of the present invention; 
           [0052]      FIG. 18  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a thirteenth embodiment of the present invention; 
           [0053]      FIG. 19  is a cross-sectional view of a thermoactuator mounted on a heat exchange device in a fourteenth embodiment of the present invention; and 
           [0054]      FIG. 20  is a cross-sectional view of a conventional heat exchange device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0055]      FIG. 1  shows a heat exchange device in a first embodiment of the present invention. The heat exchange device is, for example, a waste heat recovery device. 
         [0056]    As shown in  FIG. 1 , a waste heat recovery device (heat exchange device)  10  includes an introduction port  11  for introducing an exhaust gas (first heat medium) generated in an internal combustion engine, and a branching portion  12  connected to the introduction port  11 . The device  10  also includes a first fluid passageway  13  connected to the branching portion and extending downstream of the introduction port  11 , and a second fluid passageway  14  extending from the branching portion  12  along the first fluid passageway  13 . The device  10  further includes a heat exchanger  15  forming one part of the second fluid passageway  14  for transferring heat of an exhaust gas to a (second) medium, and a thermoactuator  40  connected to the heat exchanger  15 . The device  10  further includes a valve chamber  17  connected to respective downstream ends of the first and second fluid passageways  13 ,  14 , and a discharge port  18  connected to the valve chamber  17  for discharging the exhaust gas. The valve chamber  17  provides a junction to receive an exhaust gas having passed through either of the first and second fluid passageways  13 ,  14 . 
         [0057]    The valve chamber  17  houses a valve  28  ( FIG. 4B ). The valve is provided to pivot on a valve shaft  21 . The thermoactuator  40  is connected through a link mechanism  22  to the valve shaft  21 . 
         [0058]    The link mechanism  22  includes a plate  24  integrally attached to the valve shaft  21 , a pin  25  extending from the plate  24  along the valve shaft  21 , a hook portion  26  engaged with the pin  25  and attached to a distal end of the thermoactuator  40 , and a link return spring  27 . 
         [0059]    The heat exchanger  15  has an upper surface to which are attached a medium introducing pipe  31  for introducing a medium into the heat exchanger  15  and an actuator support member  32  supporting the thermoactuator  40 . To the actuator support member  32  is connected a medium discharging pipe  33  for discharging a medium out of the heat exchanger  15 . 
         [0060]    That is, a medium is introduced from the medium introducing pipe  31 . The introduced medium picks up heat of an exhaust gas and is discharged from the medium discharging pipe  33 . The thermoactuator  40  is discussed below in detail with reference to  FIG. 2 . 
         [0061]    As shown in  FIG. 2 , the thermoactuator  40  includes a metal case  50 , and a temperature sensitive portion  60  connected to one end of the case  50  for sensing a temperature of a medium. The thermoactuator  40  also includes a bar-shaped actuator rod (piston)  43  received in the case  50  for advancing depending upon the medium temperature sensed by the temperature sensitive portion  60 . The thermoactuator  40  further includes a rod  70  provided on a distal end of the actuator rod  43  for moving together with the actuator rod  43  in a left-right direction of  FIG. 2 . The thermoactuator  40  further includes a resin-made bearing  80  provided on an outer circumference of a distal end of the rod  70  for guiding the rod  70 , and a return spring  46  urging the rod  70  in a direction to retreat the rod  70 . The temperature sensitive portion  60  extends into the actuator support member  32  ( FIG. 1 ) for sensing a temperature of a medium flowing in the actuator support member. 
         [0062]    The metal for the case  50  may be a steel, a stainless steel, or aluminum etc. The resin for the bearing  80  may be polyimide, poly phenylene sulfide resin, or polytetrafluoroethylene etc. 
         [0063]    The case  50  includes a tubular case base portion  51  and a case stepped portion  52  extending from a distal end of the case base portion  51  toward a center axis CL of the rod to decrease in diameter. The case  50  further includes a reduced diameter portion  53  extending from a distal end of the case stepped portion  52  along the bearing  80 . The case base portion  51 , the case stepped portion  52  and the reduced diameter portion  53  are integral with one another. 
         [0064]    The temperature sensitive portion  60  includes a connection flange  61  lockingly engaging the one end of the case  50 , an element case  62  coupled to an inside of the connection flange  61 , and a cover  63  lockingly engaging a distal end of the element case  62 . The temperature sensitive portion  60  also includes a wax  64  filling a space defined by the cover  63  and the element case  64 . The temperature sensitive portion  60  further includes a flexible sleeve  65  disposed in the wax  64 . The sleeve  65  has an inner space filled with a grease  66 . 
         [0065]    Where the thermoactuator  40  is used in the waste heat recovery device  10  ( FIG. 1 ), the temperature sensitive portion  60  is inserted into the actuator support member  32  ( FIG. 1 ) to allow a medium to flow around the temperature sensitive portion  60  for sensing a temperature around the temperature sensitive portion  60 . More specifically, the temperature sensitive portion  60  senses a temperature of a medium flowing around the temperature sensitive portion  60 . 
         [0066]    The rod  70  includes a rod base portion  71  abutting on the distal end of the actuator rod  43 , and a rod body portion  72  formed integrally with the rod base portion  71  and attached at its distal end to the hook portion  26 . The rod  70  further includes a rod flange portion  73  projecting outwardly from the rod base portion  71  and extending circumferentially of the rod base portion  71 . The rod flange portion  73  bears against a rear end of the return spring  46 . 
         [0067]    The rod base portion  71  is larger in diameter than the rod body portion  72  such that the rod base portion  71  has a stepped portion  71   a  extending to the rod body portion  72 . 
         [0068]    The bearing  80  includes a tubular portion  81  having an inner circumferential surface which the rod body portion  72  slidably contacts. The bearing  80  also includes a stopper portion  82  projecting outwardly from the tubular portion  81  and extending circumferentially of the tubular portion  81 . The stopper portion  82  abuts on the case stepped portion  52 . The bearing  80  has a rear end  81   a  providing a stopper limiting advancement of the rod  70 . The stopper portion  82  has a front surface contacting the case stepped portion  52 . 
         [0069]    A guide member  48  is disposed along an outer circumference of the bearing  80 . The guide member  48  limits circumferential displacement of the return spring  46  and bears against a front end of the return spring  46 . The guide member  48  has a portion along the stopper portion  82  of the bearing  80 . A relationship between the guide member  48  and the stopper portion  82  is discussed in detail with reference to  FIG. 3 . 
         [0070]    As shown in  FIG. 3 , the stopper portion  82  has its outer circumference having a rear end defining a tapering portion  82   a  slanting relative to the center axis CL of the rod  70 . 
         [0071]    The guide member  48  includes a case contact portion  96  contacting and adhering to an inner circumferential surface of the case  50 . The guide member  48  also includes a receiving portion  97  extending from the case contact portion  96  toward the center axis CL of the rod  70  and bearing against the return spring  46 . The receiving portion  97  has a distal end on a side of the center axis CL. The guide member  48  further includes a guide portion  98  extending rearwardly from this distal end of the receiving portion  97  for limiting the circumferential displacement of the return spring  46 . 
         [0072]    A rubber-made O-ring  49  (rubber-made member) fits between the guide member  48  and the tapering portion  82   a . The bearing  80  has an outer diameter set to be slightly smaller than an inner diameter of the case  50  at a low temperature. 
         [0073]    Reference to  FIGS. 1 to 3  reveals that the thermoactuator  40  is formed as follows. 
         [0074]    The thermoactuator  40  includes the tubular case  50 , the temperature sensitive portion  60  attached to the one end of the case for sensing a temperature of the outside, the piston  43  received in the case  50  for advancing depending upon the temperature sensed by the temperature sensitive portion  60 , the rod  70  disposed on the distal end of the piston  43  for advancement caused by the advancement of the piston  43 , the return spring  46  accommodated in the case  50  for urging the rod in the direction to retreat the rod  70 , the bearing  80  extending along an outer circumferential surface of the rod  70  from the opposite end of the case  50  toward the one end of the case  50 , and the guide member  48  disposed on the outer circumference of the bearing  80  and bearing against the return spring  46  for limiting the circumferential displacement of the return spring  46 . The material for the bearing  80  is resin, and the material for the case is metal. The guide member  48  includes the case contact portion  96  contacting the inner circumferential surface of the case  50 , the receiving portion  97  extending from the case contact portion  96  toward the center axis CL of the rod  70  and bearing against the return spring  46 , and the guide portion  98  extending from the distal end of the receiving portion  97  toward the temperature sensitive portion  60  for limiting the circumferential displacement of the return spring  46 . The O-ring (ring-shaped rubber member)  49  fits between the bearing  80  and the guide member  48  for providing an urging force to limit a displacement of the bearing  80 . Operation of the thermoactuator  40  is discussed with reference to other figures than  FIGS. 1 to 3  along with operation of the waste heat recovery device  10  ( FIG. 1 ). 
         [0075]    As shown in  FIG. 4A , a medium flows from the heat exchanger  15  ( FIG. 1 ) to a circumferential edge of the temperature sensitive portion  60 . When a temperature T1 of the medium is low, the wax  64  remains shrunk. With the wax  64  shrunk, the rod  70  is held at a retreating limit under an urging force of the return spring  46 . That is, the temperature sensitive portion  60  senses a temperature in a vicinity of the temperature sensitive portion  60 , allowing the rod  70  to be held at the retreating limit. 
         [0076]    As shown in  FIG. 4B , where the temperature of the medium is low, the first fluid passageway  13  is closed by the valve  28  attached to the valve shaft  21 . 
         [0077]    Referring back to  FIG. 1 , when the first fluid passageway  13  is closed, an exhaust gas introduced from the introduction port  11  flows to the second fluid passageway  14  where the exhaust gas performs thermal exchange with the medium flowing within the heat exchanger  15  to heat the medium. 
         [0078]    As shown in  FIG. 5A , heating the medium expands the wax  64 . The expansion of the wax  64  compresses the sleeve  65  to cause the actuator rod  43  to advance against the urging force of the return spring  46 . That is, the temperature sensed by the temperature sensitive portion  60  causes the advancement of the actuator rod  43 . Together with the actuator rod  43 , the rod  70  advances. 
         [0079]    When the temperature of the medium reaches a temperature T2, the stepped portion  71   a  of the rod  70  abuts on the end  81   a  of the bearing  80 . This prevents further advancement of the rod  70 . 
         [0080]    As shown in  FIG. 5B , when the temperature of the medium is T2, the valve  28  opens the first fluid passageway  13  in an amount sufficient to allow an exhaust gas to pass through the first fluid passageway  13 . 
         [0081]    Referring back to  FIG. 1 , when the first fluid passageway  13  is opened, an exhaust gas flows within the first fluid passageway  13  located downstream of and attached to the introduction port  11  in alignment therewith. In this case, since the exhaust gas does not flow into the second fluid passageway  14 , thermal exchange does not occur between the exhaust gas and the medium. 
         [0082]    Referring back to  FIG. 5A , the stopper (the end  81   a  of the bearing  80 ) providing an advancement limit of the rod  70  is formed within the case  50 . When the rod  70  advances to a predetermined position, the rod  70  abuts on the end  81   a  of the bearing  80 . The abutment prevents further advancement of the rod  70 . Thus, it is possible to prevent the rod  70  from advancing more than necessary. The prevention of the unnecessary movement inhibits the bearing  80  from wearing due to the rod  70  contacting the bearing  80 . As discussed above, the actuator rod  43  moves together with the rod  70 . By preventing the unnecessary movement of the rod  70 , it is possible to inhibit the sleeve  65  from wearing due to the actuator rod (piston)  43  contacting the sleeve  65 . The inhibition of the wear reduces frequency of replacement of components of the thermoactuator  40 , thereby enabling use of the thermoactuator  40  over a long period of time. 
         [0083]    As discussed above, the rod  70  has the stepped portion  71   a  formed thereon and the stopper is formed by the end  81   a  of the bearing  80 . When the rod  70  advances to bring the stepped portion  71   a  into contact with the end  81   a  of the bearing  80 , further advancement of the rod  70  is prevented. Since the end  81   a  of the bearing  80  is used as the stopper for the rod  70 , it is possible to provide an advancement limit without increasing the number of the components. 
         [0084]    As discussed above, the bearing  80  has the stopper portion  82  extending along the outer circumference, and the front surface of the stopper portion  82  abuts on the case  50  (the case stepped portion  52 ). When the rod  70  comes into contact with the bearing  80 , the stopper portion  82  bears a force applied in a direction from the rear side to the front side. As a result, displacement of the bearing  80  along the center axis CL is prevented to reliably prevent movement of the rod  70 . 
         [0085]    Referring also to  FIG. 5B , an amount of advancement of the rod  70  is set in correspondence to an amount of turning of the valve  28 . That is, when the valve  28  turns to a sufficiently open position, advancement of the rod  70  is stopped. As a result, the valve  28  stops turning at a predetermined location. Where the thermoactuator  40  does not have the stopper, the rod  70  can advance in excess of a predetermined amount, in which case the valve  28  can be activated by the thermoactuator  40  to turn in excess of a predetermined amount. Thus, where the thermoactuator  40  does not have the stopper, the valve chamber  17  accommodating the valve  28  is required to have a larger size taking the excess movement of the rod  70  into account. In the thermoactuator  40  discussed above, the excess movement is prevented. Thus, it is not necessary to set a large size of the valve chamber  17 , thereby reducing a size of the waste heat recovery device  10 . A further discussion as to operation of the thermoactuator is made below. 
         [0086]    Referring to  FIG. 20 , generally speaking, resin (bearing  205 ) is larger in coefficient of expansion than metal (case  201 ). It is believed that a size of the bearing is set to allow for appropriate contact between the bearing and the case under a high temperature, taking account of use of the bearing in a device like a waste heat recovery device which becomes high in temperature. However, a gap can occur between the case  201  and the bearing  205  under a low temperature because the bearing  205  shrinks more than the case  201 . As the rod  204  moves through the bearing  205  with such a gap between the case and the bearing, thus, the bearing  205  shakes. 
         [0087]    On the other hand, where the size of the bearing  205  is set to allow for appropriate contact between the bearing  205  and the case  201  under a low temperature, the case  201  bears a large load due to the bearing  205  greatly expanding under a high temperature. 
         [0088]    It is desirable to provide a technique for preventing the shake of the bearing  205 . 
         [0089]    As shown in  FIG. 6A , slight gaps are formed between the bearing  80  and the case  50  and between the bearing  80  and the guide member  48  under a low temperature. An urging force F1 of the O-ring  49  contacting the tapering portion  82   a  acts in a direction normal to the tapering portion  82   a . Since the tapering portion  82   a  slants relative to the center axis CL of the rod  70 , a component F2 of the urging force F1 acts in a direction toward the center axis CL of the rod  70  and a component F3 of the urging force F1 acts in a direction along the center axis CL of the rod  70 . 
         [0090]    The component F2 acting in the direction toward the center axis CL of the rod  70  is applied to the tapering portion  82   a  throughout the entire circumference of the tapering portion  82   a . That is, the bearing  80  is urged toward the center axis CL of the rod  70  throughout the entire circumference of the bearing  80 . 
         [0091]    The component F3 acting in the direction along the center axis CL of the rod  70  is applied to the tapering portion  82   a  throughout the entire circumference of the tapering portion  82   a . That is, the bearing  80  is pressed against the case stepped portion  52  throughout the entire circumference of the bearing  80 . 
         [0092]    A portion of the gap between the bearing  80  and the case  50  is filled with the O-ring  49  through the guide member  48 . Filling the gap between the bearing  80  and the case  50  prevents the bearing from shaking under a low temperature. 
         [0093]    Since the urging force F1 of the O-ring  49  acts both in a central axial direction of the case  50  and in a circumferential direction of the case  50 , the gap between the bearing  80  and the case  50  is filled in the axial and circumferential directions, thereby reliably preventing the shaking of the bearing  80 . 
         [0094]    The O-ring  49  is used as the rubber member. The O-ring  49  is cheap. That is, measures against the shaking of the bearing  80  can be taken cheaply. 
         [0095]    As shown in  FIG. 6B , the resin-made bearing  80  of large coefficient of expansion expands more than the metal case  50  under a high temperature. Due to the relatively great expansion of the bearing  80 , the bearing  80  comes into contact with the inner circumferential surface of the case  50 , in which case the O-ring  49  elastically deforms under the expanding force of the bearing  80 . That is, by deforming, the O-ring  49  escapes a gap left between the guide member  49  and the bearing  80 . As a result, a load applied to the case  50  can be made smaller than if the bearing  80  closely contacts the case  50  under a low temperature. That is, it is possible to prevent the shaking of the bearing  80  under the low temperature and reduce a load applied to the case  50  under the high temperature. 
       Second Embodiment 
       [0096]    Next, a second embodiment of the present invention is discussed with reference to  FIG. 7 .  FIG. 7  shows a cross-section of a thermoactuator mounted on a heat exchange device in correspondence to  FIG. 2 . It is noted that elements common to those in  FIG. 2  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0097]    As shown in  FIG. 2 , a thermoactuator  40 A differs from the thermoactuator in the first embodiment in that the stopper and the rod flange portion are modified. 
         [0098]    More specifically, a rod  70 A has a rod flange portion  73 A projecting from a lateral surface of a rod base portion  71 A thereof to an outer circumference of the return spring  46 . 
         [0099]    A case  50 A has a projecting portion  55 A projecting from an inner circumferential surface thereof toward a center axis CL of the case  50 A. The projecting portion  55 A projects to a location circumferentially overlapping the rod flange portion  73 A. That is, the projecting portion  55 A projects to a location where the rod flange portion  73 A can abut on the projecting portion  55 A. This projecting portion  55 A forms a stopper. When the rod  70 A advances a predetermined amount, the rod flange portion  73 A contacts the projecting portion  55 A. The projecting portion  55 A prevents further advancement of the rod  70 A. 
         [0100]    The projecting portion  55 A may be formed integrally with the case  50 A or separate from the case  50 A. In the thermoactuator  40 A, the unnecessary movement of the rod  70 A is prevented to thereby inhibit the bearing  80  from wearing due to the rod  70 A contacting the bearing  80 . In addition, it is possible to inhibit the sleeve  65  from wearing due to the actuator rod (piston)  43  contacting the sleeve  65 . 
         [0101]    Since the projecting portion  55 A is formed along the inner circumferential surface of the case  50 A, the projecting portion  55 A has a larger circumferential cross-sectional area than the other portions of the case  50 A. The larger circumferential cross-sectional area ensures a large area to contact the rod flange portion  73 A. Due to the projecting portion  55 A having the large area contacting the rod flange portion  73 A, a load applied per unit area of the projecting portion  55 A is reduced to achieve a prolonged life of the thermoactuator  40 A. 
         [0102]    As for the first embodiment, it is required to ensure a minimum necessary length of the bearing. In this respect, a stopper can be formed at a limited location. In contrast, since the projecting portion  55 A can be disposed regardless of the length of the bearing, a freedom to dispose the projecting portion  55 A in the axial direction is enhanced. 
       Third Embodiment 
       [0103]    Next, a third embodiment of the present invention is discussed with reference to  FIG. 8 .  FIG. 8  shows a cross-section of a thermoactuator mounted on a heat exchange device in correspondence to  FIG. 2 . It is noted that elements common to those in  FIG. 2  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0104]    As shown in  FIG. 8 , a thermoactuator  40 B differs from the thermoactuator in the first embodiment in that the guide member is modified. 
         [0105]    More specifically, a guide member  48 B for limiting circumference displacement of the return spring  46  extends from the opposite end of the case  50  toward the one end of the case  50  along an inner circumference of the return spring  46 . The guide member  48 B and the stepped portion  71   a  circumferentially overlap. The guide member  48 B has a rear end  48   a  forming a stopper. When the rod  70  advances a predetermined amount, the stepped portion  71   a  contacts the end (stopper)  48   a  of the guide member  48 B to prevent further advancement of the rod  70 . 
         [0106]    The rear end  48   a  of the guide member  48  is desirably bent toward the center axis CL along a rear end of the bearing  80 . This is because the stopper portion  82  can bear a force acting in a direction from the front side to the rear side when the rod  70  comes into contact with the end  48   a  of the guide member  48 B. As a result, axial displacement of the bearing  80  and the guide member  48   b  is prevented to reliably prevent further movement of the rod  70 . The bearing  80  has a length reaching the end  48   a  of the guide member  48 B. That is, both the guide member  48 B and the bearing  80  extend to substantially the same location forming the stopper. 
         [0107]    In the thermoactuator  40 B, the unnecessary movement of the rod  70  is prevented to thereby inhibit the bearing  80  from wearing due to the rod  70  contacting the bearing  80 . In addition, it is possible to inhibit the sleeve  65  from wearing due to the actuator rod (piston)  43  contacting the sleeve  65 . 
         [0108]    Since the end  48   a  of the guide member  48 B is used as the stopper for the rod  70 , it is possible to provide an advancement limit of the rod  70  without increasing the number of the components. 
       Fourth Embodiment 
       [0109]    Next, a fourth embodiment of the present invention is discussed with reference to  FIG. 9 .  FIG. 9  shows a cross-section of a thermoactuator mounted on a heat exchange device in correspondence to  FIG. 2 . It is noted that elements common to those in  FIG. 2  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0110]    As shown in  FIG. 9 , a thermoactuator  40 C differs from the thermoactuator in the first embodiment in that the shape of the case is modified. 
         [0111]    More specifically, a case  50 C has one end and an opposite end defining a bend portion  56 C folded over to a location circumferentially overlapping the rod  70 . This bend portion  56 C forms a stopper. Abutment of the distal end of the rod  70  on the bend portion  56 C prevents advancement of the rod  70 . 
         [0112]    In the thermoactuator  40 C, the unnecessary movement of the rod  70  is prevented to thereby inhibit the bearing  80  from wearing due to the rod  70  contacting the bearing  80 . In addition, it is possible to inhibit the sleeve  65  from wearing due to the actuator rod (piston)  43  contacting the sleeve  65 . 
         [0113]    Since the end of the case  50 C is used as the stopper for the rod  70 , it is possible to provide an advancement limit of the rod  70  without increasing the number of the components. Since, the rod  70  is covered by the case  50 C along the length to the distal end thereof, the rod  70  can be protected. 
       Fifth Embodiment 
       [0114]    Next, a fifth embodiment of the present invention is discussed with reference to  FIGS. 10A to 10C .  FIGS. 10A to 10C  are cross-sections of a thermoactuator mounted on a heat exchange device in correspondence to  FIG. 2 . It is noted that elements common to those in  FIG. 2  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0115]    As shown in  FIG. 10A , a thermoactuator  40 D is the thermoactuator in the first embodiment with a wax escape portion added. 
         [0116]    More specifically, an escape portion  90  is attached to the temperature sensitive portion  60  for allowing the wax  64  further expanding to escape into the escape portion  90  with the rod  70  positioned at the advancement limit. 
         [0117]    The escape portion  90  includes a plate  91  connected to the temperature sensitive portion  60  (element case  62 ) and having a hole  91   a  formed through the plate  91 . The escape portion  90  also includes an escape case  92  connected to the plate  91 , and a closure member  100  accommodated in the escape case  92  for closing the hole  91   a . The escape portion  90  further includes a spring  94  urging the closure member  100  toward the plate  91 . In other words, the plate  91  provides a valve seat, and the escape case  92  provides a valve body. 
         [0118]    The closure member  100  includes a disc-shaped base portion  102  having an outer circumference to which a seal  101  is attached. The closure member  100  further includes a guide portion  104  formed integrally with the base portion  102  and along an inner circumference of the spring  49 . 
         [0119]    The spring  94  of the escape portion  90  has a spring constant larger than that of the return spring  46  and the hole  91   a  has a small diameter, such that the rod  70  shifts prior to the closure member  100 . 
         [0120]    As shown in  FIG. 10B , as a temperature rises to expand the wax  64 , the rod  70  starts to advance. After advancing a predetermined amount, the rod  70  is prevented by the end  81   a  of the bearing  80  from further advancing. 
         [0121]    As shown in  FIG. 10C , the wax  64  further expands to force the closure member  100  to be depressed. The depression of the closure member  100  allows the wax  64  to escape into the escape portion  92 . This results in a load applied to the temperature sensitive portion  60  being reduced. 
         [0122]    In the thermoactuator  40 D, the unnecessary movement of the rod  70  is prevented to thereby inhibit the bearing  80  from wearing due to the rod  70  contacting the bearing  80 . In addition, it is possible to inhibit the sleeve  65  from wearing due to the actuator rod (piston)  43  contacting the sleeve  65 . 
       Sixth Embodiment 
       [0123]    Next, a discussion is made as to a waste heat recovery device providing a heat exchange device with reference to  FIG. 11 .  FIG. 11  shows a cross-section of the waste heat recovery device in the sixth embodiment. It is noted that elements common to those in  FIG. 1  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0124]    As shown in  FIG. 11 , a waste heat recovery device  110  includes a second pin (stopper)  111  extending from a lateral side of the valve chamber  17  onto the center axis CL of the rod  70 . 
         [0125]    Advancement of the rod  70  is prevented by abutment of the hook portion  26  on the second pin  111 . The waste heat recovery device  110  produces predetermined advantageous results of the present invention. 
         [0126]    In particular, since the second pin  111  is disposed on the center axis CL of the rod  70 , it is possible to limit advancement of the rod  70  without producing a bending moment on the rod  70 . 
       Seventh Embodiment 
       [0127]    Next, a discussion is made as to a waste heat recovery device providing a heat exchange device with reference to  FIG. 12 .  FIG. 12  shows a cross-section of the waste heat recovery device in the seventh embodiment in correspondence to  FIG. 11 . It is noted that elements common to those in  FIG. 11  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0128]    As shown in  FIG. 12 , a waste heat recovery device  120  includes a third pin (abutment piece)  121  rising from the plate  24 . The waste heat recovery device  120  further includes a bar (stopper)  122  extending from the lateral side of the valve chamber  17  onto an orbit of the third pin  121 . 
         [0129]    Advancement of the rod  70  rotates the plate  24 . The third pin  121  revolves concurrently with the rotation of the plate  24 . When the rod  70  advances a predetermined amount to thereby revolve the third pin  121  by a predetermined amount, the third pin  121  abuts on the bar  122 . The abutment of the third pin  121  on the bar  122  prevents further revolution of the third pin  121  as well as further advancement of the rod  70 . The waste heat recovery device  120  produces the predetermined advantageous results of the present invention. 
       Eighth Embodiment 
       [0130]    Next, a discussion is made as to a waste heat recovery device providing a heat exchange device with reference to  FIG. 13 .  FIG. 13  shows a cross-section of the waste heat recovery device in the eighth embodiment in correspondence to  FIG. 4B . It is noted that elements common to those in  FIG. 4B  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0131]    As shown in  FIG. 13 , a waste heat recovery device  130  includes a stopper  131  attached to the valve  28 . The stopper  131  abuts on an inner wall  17   a  of the valve chamber  17  by the valve  28  swinging a predetermined amount. The abutment of the stopper  131  on the inner wall  17   a  prevents further swinging of the valve  28 . The waste heat recovery device  130  produces the predetermined advantageous results of the present invention. 
       Ninth Embodiment 
       [0132]    Next, a discussion is made as to a waste heat recovery device providing a heat exchange device with reference to  FIG. 14 .  FIG. 14  shows a cross-section of the waste heat recovery device in the ninth embodiment in correspondence to  FIG. 13 . It is noted that elements common to those in  FIG. 13  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0133]    As shown in  FIG. 14 , a waste heat recovery device  140  includes a stopper  141  disposed on the inner wall  17   a  of the valve chamber  17  as well as on an orbit of the valve  28 . By swinging a predetermined amount, the valve  28  abuts on the stopper  141 . By abutting on the stopper  141 , the valve  28  is prevented from further swinging. The waste heat recovery device  140  produces the predetermined advantageous results of the present invention. 
       Tenth Embodiment 
       [0134]    Next, the tenth embodiment is discussed with reference to  FIGS. 15A and 15B . 
         [0135]      FIG. 15A  shows a cross-section of a thermoactuator used in a heat waste recovery device in the tenth embodiment in correspondence to  FIG. 2 . It is noted that elements common to those in  FIG. 2  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0136]    As shown in  FIG. 15A , a thermoactuator  40 E differs from the thermoactuator shown in  FIG. 2  in that the stopper portion has a distal end of modified shape. 
         [0137]    As shown in  FIG. 15B , a stopper portion  82 E of the thermoactuator  40 E has an L-shaped groove  82   b  of generally L-shaped cross-section formed at an end portion of an outer circumference thereof. The L-shaped groove  82   b  is located in an opposed relationship with a generally L-shaped cross-sectional corner portion Co defined by the case contact portion  96  and the case stepped portion  52 . The corner portion Co and the L-shaped groove  82   b  define a space of generally rectangular cross-section. The O-ring  49  is disposed in contact with all of sides of the generally rectangular cross-section. 
         [0138]    Although the corner portion Co is defined by the two members, i.e., the guide member  48  and the case  50 , the corner portion Co may be defined only by either the guide member  48  or the case  50 . 
         [0139]    That is, the L-shaped groove  82   b  of generally L-shaped cross-section is formed at the end of the outer circumference of the stopper portion  82 E, the corner portion Co of generally L-shaped cross-section defined by the case  50  or the guide member  48  is located in an opposed relationship with the L-shaped groove  82   b , and the O-ring  49  (rubber-made member  49 ) is disposed in contact with respective sides of a space of generally rectangular cross-section defined by the L-shaped groove  82   b  and the corner portion Co. 
         [0140]    Thus, the O-ring  49  can urge a bearing  80 E both in a direction toward the center axis CL of the rod  70  and in a direction along the center axis CL of the rod  70 . Such an arrangement produces the predetermined advantageous results of the present invention. 
         [0141]    Further, the work of assembling the thermoactuator  40 E is facilitated because the work can be done with the O-ring  49  fitting in the L-shaped groove  82   b.    
       Eleventh Embodiment 
       [0142]    Next, the eleventh embodiment is discussed with reference to  FIG. 16 . 
         [0143]      FIG. 16  shows a cross-section of a thermoactuator used in a heat waste recovery device in the eleventh embodiment in correspondence to  FIG. 15A . It is noted that elements common to those in  FIG. 15A  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0144]    As shown in  FIG. 16 , a thermoactuator  40 F differs from the thermoactuator shown in  FIG. 15A  in that the stopper portion has a distal end of modified shape. 
         [0145]    That is, a stopper portion  82 F of the thermoactuator  40 F has the L-shaped groove  82   b  of generally L-shaped cross-section formed at a rear end portion of an outer circumference thereof. The thermoactuator  40 F employing a bearing  80 F having such a stopper portion  82 F produces the predetermined advantageous results of the present invention. 
       Twelfth Embodiment 
       [0146]    Next, the twelfth embodiment is discussed with reference to  FIG. 17 .  FIG. 17  shows a cross-section of a thermoactuator used in a heat waste recovery device in the twelfth embodiment in correspondence to  FIG. 15A . It is noted that elements common to those in  FIG. 15A  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0147]    As shown in  FIG. 17 , a thermoactuator  40 G differs from the thermoactuator shown in  FIG. 15A  in that modifications are made to the shapes of the bearing, the guide member and the case. 
         [0148]    A bearing  80 G includes a tubular portion  81 G and tapering portions  81   b ,  81   b  formed at front and rear ends of the tubular portion  81 G. A guide member  48 G includes a guide portion  98 G and a bend portion  99 G folded over from a rear end of the guide portion  98 G toward the center axis CL of the rod  70 . A case  50 G has a bend portion  56 G folded over from a distal end of the reduced diameter portion  53  toward the center axis CL of the rod  70 . 
         [0149]    In the thermoactuator  40 G, the O-rings  49  are disposed in contact with the respective front and rear tapering portions  81   b ,  81   b . The thermoactuator  40 G produces the predetermined advantageous results of the present invention. 
         [0150]    In the thermoactuator  40 G shown in  FIG. 17 , the O-ring  49  on a right side of  FIG. 17  is disposed between the bearing  80  and the case  50 G. That is, the thermoactuator  40 G includes the tubular case  50 G, and the temperature sensitive portion  60  attached to one end of the case  50 G for sensing a temperature of the outside. The thermoactuator  40 G also includes the piston  43  received in the case  50 G for advancing depending on the temperature sensed by the temperature sensitive portion  60 , and the rod  70  disposed on the distal end of the piston  43  for advancing by advancement of the piston  43 . The thermoactuator  40 G further includes the return spring  46  accommodated in the case  50 G for urging the rod  70  in the direction to retreat the rod  70 . The thermoactuator  40 G further includes the bearing  80 G extending from the opposite end of the case  50 G toward the one end of the case  50 G along an outer circumferential surface of the rod  70 . The thermoactuator  40 G further includes the guide member  48 G disposed on the outer circumference of the bearing  80 G and receiving the return spring  46  for limiting circumferential displacement of the spring  46 . A resin is used as material for the bearing  80 G. A metal is used as material for the case  50 G. The O-ring  49  (ring-shaped rubber member) is disposed between the bearing  80 G and the case  50 G for exerting an urging force on the bearing  80 G to limit displacement of the bearing  80 G. 
       Thirteenth Embodiment 
       [0151]    Next, the thirteenth embodiment is discussed with reference to  FIG. 18 .  FIG. 18  shows a cross-section of a thermoactuator used in a heat waste recovery device in the thirteenth embodiment in correspondence to  FIG. 15A . It is noted that elements common to those in  FIG. 15A  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0152]    As shown in  FIG. 18 , a thermoactuator  40 H differs from the thermoactuator shown in  FIG. 15A  in that modifications are made to the shapes of the bearing, the guide member and the case. 
         [0153]    More specifically, a bearing  80 H has no tapering portion. A guide member  48  and a case  50 H have respective tapering portions  48   a ,  50   a  formed thereon. The O-rings  49 ,  49  are disposed in contact with these tapering portions  48   a ,  50   a . The O-rings  49 ,  49  are also disposed at boundaries between a tubular portion  81 H of the bearing  80 H and a stopper portion  82 H of the bearing  80 H. The thermoactuator  4011  produces the predetermined advantageous results of the present invention. 
       Fourteenth Embodiment 
       [0154]    Next, the fourteenth embodiment is discussed with reference to  FIG. 19 .  FIG. 19  shows a cross-section of a thermoactuator used in a heat waste recovery device in the fourteenth embodiment in correspondence to  FIG. 15A . It is noted that elements common to those in  FIG. 15A  are designated by the same reference numerals and their detailed discussions are omitted. 
         [0155]    As shown in  FIG. 19 , a thermoactuator  40 J differs from the thermoactuator shown in  FIG. 15A  in that modifications are made to the shape of the bearing and the rubber member. 
         [0156]    More specifically, a bearing  80 J includes a tubular portion  81 J and a triangular cross-sectional edge portion  81   c  formed integrally with the tubular portion  81 J along an outer circumference of the tubular portion  81 J. A rubber member  49 J of quadrangular cross-section is mounted on the tubular portion  81 J and covers the edge portion  81   c . The thermoactuator  40 H produces the predetermined advantageous results of the present invention. 
         [0157]    It is understood that the present invention is not limited to the respective embodiments. That is, the arrangements or structures shown in the respective embodiments may be appropriately combined as long as the combined arrangements or structures have functions and advantageous results of the present invention. For example, the escape portion may be provided in the embodiment wherein the end of the guide member provides the stopper. Other examples of combinations are possible without being limited to such an example. 
         [0158]    Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.