Thermoactuator

Abstract

[Problem] To provide a thermoactuator capable of maintaining the open state of a driven member such as a louver even when the surrounding temperature is lowered after removal of failure in operation of the driven member. [Solution] The present invention is provided with: a thermoelement 2 having a piston rod 3 that protrudes in association with rise in surrounding temperature; a first rod 5 that is mounted so as to freely protrude and retract relative to a case (first case 4) and that performs the operation of protruding and retracting in conjunction with the piston rod 3; and a main spring (first spring 6) that biases the first rod in the retraction direction as well as an auxiliary spring (second spring 9) that is locked in a compressed state by means of a locking mechanism (retaining ring 10). The locking mechanism is configured such that the locking is released when an axial force of at least a prescribed level has acted on the first rod due to reaction of pressing the piston rod at the thermoelement, resulting from the failure in operation of a driven member (louver) which is driven in conjunction with the first rod, and that the first rod, which has been biased by the auxiliary spring (second spring) and has protruded, does not retract and move back.

Description

Thermoactuator

[0001] The present invention relates to a thermoactuator, and more particularly to a thermoactuator equipped with an auxiliary spring that maintains the protruding length of the rod even when the ambient temperature of the thermoelement drops in order to prevent overheating when an abnormal axial force is generated.

[0002] Conventionally, it has been known to adjust the amount of outside air sent to a heat exchanger or engine by opening and closing (driving) a driven member, such as a louver (shielding plate), which is driven in conjunction with the extension and retraction of a rod by an actuator that operates in response to engine coolant temperature or oil temperature. However, due to environmental changes or rough road conditions, foreign objects can become caught in the driven member, such as a louver, causing the driven member to stick or become difficult to move, resulting in malfunction. If the driven member, such as a louver, is closed at that time, the air flow to the engine is cut off, causing the oil temperature to rise and, in the worst case, leading to overheating. For this reason, some means is needed to open the driven member and maintain its open state even when the ambient temperature drops.

[0003] Even with conventional thermoactuator structures, the force of pushing out the piston rod of the thermoelement can generate enough force to release malfunctions such as sticking caused by foreign matter, but the thermoactuator then operates normally, making it difficult to alert the user to the abnormality. Furthermore, once a thermoactuator has been released from a stuck state, it may experience internal deformation due to abnormal stress, preventing it from achieving the required lift (rod extension length). If a thermoactuator subjected to abnormal stress continues to operate normally, the inability to achieve the required lift can lead to engine overheating.

[0004] For example, Patent Document 1 discloses a thermoactuator having a locking function that can smoothly lock the retainer 15 when the retainer 15 is in a lifted state, in which the guide body 11 that supports the retainer 15 is provided with a cylindrical portion 11a that rises from the base end, a tapered portion 11c whose outer diameter increases toward the tip of the cylindrical portion, and an engagement groove 11d for a locking member that is recessed in the axial direction following the tapered portion (see claim 1 in the claims of Patent Document 1, paragraphs

[0025] to

[0036] of the specification, and Figures 1 to 5 of the drawings, etc.).

[0005] However, the thermoactuator with a locking function described in Patent Document 1 is designed to lock open when a certain high lift is reached during an abnormally high temperature, and is not designed to deal with the occurrence of abnormal loads such as when a foreign object is caught in the device. Therefore, if the specific lift is not reached during the occurrence of an expected abnormal load, the thermoactuator may not be able to lock open and may return to normal operation.

[0006] Japanese Patent Application Laid-Open No. 2017-223332

[0007] The present invention has been devised to solve the above problems, and its object is to provide a thermoactuator equipped with an auxiliary spring that applies force to maintain the protruding length of the rod, so that the driven member, such as a louver, can remain in the open state even when the ambient temperature drops after the malfunction of the driven member is corrected.

[0008] The thermoactuator according to the first invention is a thermoactuator that is a temperature-sensitive control device, and comprises a thermoelement having a piston rod that protrudes as the ambient temperature rises, a case attached to the thermoelement, a first rod that is attached to the case so that it can be freely protruded and retracted and that protrudes and retracts in conjunction with the piston rod, a main spring that urges the first rod in the retracting direction, and further comprises an auxiliary spring that is locked in a compressed state by a locking mechanism, wherein the locking mechanism is configured to release the lock when an axial force of a predetermined level or more acts on the first rod due to a reaction force from the thermoelement pushing out the piston rod caused by a malfunction of a driven member that is driven in conjunction with the first rod, and the first rod that has been urged by the released auxiliary spring retracts and does not retract.

[0009] A thermoactuator according to a second aspect of the present invention is the same as that of the first aspect, wherein the locking mechanism is a mechanism in which the locking is released when a load equal to or greater than a predetermined value is applied to the locking member, causing it to deform or break.

[0010] The thermoactuator according to the third invention is characterized in that, in the second invention, the locking member is hooked onto a tapered section whose diameter gradually increases, and a slit is formed in the locking member, and when an axial force greater than a predetermined value is applied to the first rod, the locking member moves along the tapered section, widening the slit, and the lock is released when the locking member falls off.

[0011] The thermoactuator according to the fourth invention is characterized in that, in the second invention, the locking member is hooked onto a locking portion, and when an axial force greater than a predetermined value acts on the first rod, the locking member comes off the locking portion and falls off, thereby releasing the lock.

[0012] The thermoactuator according to the fifth invention is characterized in that, in the first invention, the locking mechanism is locked by directly hooking the auxiliary spring onto a locking portion, and when an axial force greater than a predetermined value acts on the first rod, the auxiliary spring disengages from the locking portion, thereby releasing the lock.

[0013] A thermoactuator according to a sixth aspect of the present invention is any of the first to fifth aspects of the present invention, further comprising a second rod interposed between the piston rod and the first rod and adapted to move forward and backward in conjunction with the piston rod, wherein when no axial force of a predetermined level or greater is acting on the first rod, there is a gap between the first rod and the second rod, and the movement of the second rod is transmitted to the first rod via the auxiliary spring, and when an axial force of a predetermined level or greater is acting on the first rod, the locking mechanism is released, the gap disappears, and the first rod and the second rod come into contact, thereby transmitting the movement of the second rod to the first rod.

[0014] The thermoactuator according to the seventh invention is characterized in that, in the sixth invention, when an axial force greater than a predetermined value is applied to the first rod, the locking mechanism is released and the protruding length of the first rod is maintained by the force of the auxiliary spring, and then the protruding movement of the piston rod due to an increase in ambient temperature is transmitted to the first rod via the second rod, causing the first rod to protrude further.

[0015] According to the first to seventh inventions, the auxiliary spring is provided, and the locking mechanism is configured to release the lock when a predetermined axial force or more is applied to the first rod due to a reaction force caused by the thermo-element pushing the piston rod due to a malfunction of the driven member driven in conjunction with the first rod, and the first rod, which is pushed out by the piston rod due to the force of the released auxiliary spring, once protrudes, retracts and does not retract even if the temperature around the thermo-element drops. Therefore, even if the temperature around the thermo-element drops after the malfunction of the driven member is corrected, the driven member can be maintained in an open state, preventing the worst-case scenario of overheating. Furthermore, according to the first to seventh inventions, the driven member, such as a louver, will always be open after a malfunction occurs, i.e., the driven member will remain open even at low temperatures, alerting the user to the abnormality.

[0016] In particular, according to the second and third inventions, the locking is released when the locking member is deformed or broken, so that the locking mechanism can be achieved with a simple and inexpensive configuration, and the driven member can be reliably biased by the auxiliary spring to hold it in the open state.

[0017] In particular, according to the fourth invention, the lock is released when the locking member disengages from the locking portion and falls off, which makes it possible to further simplify and reduce the cost of the locking mechanism and reliably maintain the driven member in the open state by applying force from the auxiliary spring.

[0018] In particular, according to the fifth invention, the locking mechanism is locked by the auxiliary spring being directly hooked onto the locking portion, and when an axial force greater than a predetermined value is applied to the first rod, the auxiliary spring is disengaged from the locking portion, thereby releasing the lock. This eliminates the need for a locking member, allows the locking mechanism to have a simple and inexpensive configuration, and there is no risk of the locking member getting caught along the way, so the auxiliary spring can reliably bias the driven member to hold it in the open state.

[0019] In particular, according to the sixth invention, when an axial force greater than a predetermined value is not acting on the first rod, the movement of the second rod is transmitted to the first rod via the auxiliary spring, and when an axial force greater than a predetermined value is acting on the first rod, the first rod and the second rod come into contact, thereby transmitting the movement of the second rod to the first rod.Therefore, it is possible to effectively achieve both the ability to sense an axial force greater than a predetermined value on the first rod and maintain the driven member in an open state, and the ability to reliably transmit the movement of the piston rod, which protrudes as the ambient temperature rises, to the first rod.

[0020] In particular, according to the seventh invention, when the temperature becomes high, the thermoelement (pellet) is activated and can open the driven member. Even when some adhesion force remains after the adhesion is released and a certain protrusion length cannot be obtained with the load of the auxiliary spring, the thermoelement (pellet) can be activated to open the driven member, preventing engine overheating.

[0021] FIG. 1 is a cross-sectional view showing the configuration of a thermoactuator according to an embodiment of the present invention. FIG. 2(a) is an enlarged view of portion A in FIG. 1 under normal conditions, and FIG. 2(b) is an enlarged view of portion A in FIG. 1 under abnormal load conditions. Also, FIG. 2(c) is a plan view showing a retaining ring under normal conditions, and FIG. 2(d) is a plan view showing a retaining ring under abnormal axial force conditions. FIG. 3(a) is a view corresponding to the enlarged view of portion A in FIG. 1 showing a retaining ring according to another embodiment under normal conditions, and FIG. 3(b) is a view corresponding to the enlarged view of portion A in FIG. 1 showing a retaining ring according to another embodiment under abnormal axial force conditions. Also, FIG. 3(c) is a plan view showing a retaining ring according to another embodiment under normal conditions, and FIG. 3(d) is a plan view showing a retaining ring according to another embodiment under abnormal axial force conditions. FIG. 4(a) is a view corresponding to the enlarged view of portion A in FIG. 1 showing a locking mechanism according to another embodiment, and FIG. 4(b) is a view corresponding to the enlarged view of portion A in FIG. 1 showing a locking mechanism according to another embodiment under abnormal axial force conditions. Fig. 5 is a diagram showing normal operation of the thermoactuator of the same, where (a) shows before the temperature rise and (b) shows after the temperature rise. Fig. 6 is a diagram showing operation of the thermoactuator after a malfunction occurs, where (a) shows operation when the malfunction occurs, (b) shows operation when the malfunction is resolved, and (c) shows operation when the louver is open. Fig. 7 is a diagram showing operation of the thermoactuator of the same when fully open, where (a) shows an open-lock state in which the first rod is held in a predetermined lift state by the auxiliary spring the same as Fig. 6(c) and the louver is held in an open state, and (b) shows the fully open state.

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermoactuator according to an embodiment of the present invention will now be described in detail with reference to the drawings.

[0023] <Configuration of Thermoactuator> The configuration of a thermoactuator 1 according to an embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a cross-sectional view showing the configuration of a thermoactuator 1 according to an embodiment of the present invention.

[0024] As shown in Figure 1, a thermoactuator 1 according to an embodiment of the present invention is a temperature-sensitive control device that includes a thermoelement 2 and functions both as a temperature sensor and as an actuator that performs a control operation (driving operation). The thermoactuator 1 according to this embodiment will be described by taking as an example a thermoactuator that senses engine oil temperature and opens and closes a louver (shield), which is a driven member, to adjust the amount of air blown.

[0025] (Thermo-element) This thermo-element 2 comprises a housing 20, which is a container made of metal such as brass in which wax such as paraffin wax is sealed, and a stainless steel piston rod 3 that can be freely protruded and retracted into this housing 20, so that the piston rod 3 protrudes due to the expansion of the wax inside the housing 20 as the temperature around the thermo-element 2 rises. Of course, the wax sealed in the housing 20 is not limited to paraffin wax, and any substance that has predetermined thermal expansion characteristics with a relatively large change in volume, such as microwax, can be applied to the present invention.

[0026] The thermoactuator 1 according to this embodiment also includes a first case 4 in which the thermoelement 2 is mounted, a first rod 5 mounted so as to be able to freely protrude and retract relative to the first case 4, and a first spring 6 which is the main spring that biases the first rod 5 in the retracting direction.

[0027] A second case 8 is connected to the first rod 5, and a second spring 9, which is an auxiliary spring that biases the second case 8 and the first rod 5 in the protruding direction, is interposed in the second case 8. The second spring 9 is hooked and locked to the second rod 11 by a retaining ring 10, which is a locking member, in a compressed state.

[0028] This second rod 11 is inserted between the piston rod 3 and the second case 8, and when the piston rod 3 protrudes due to the expansion of the wax, the second rod 11 is pushed out by the piston rod 3, pushing out the second case 8 and the first rod 5 connected to the second case 8 in a domino effect. However, as shown in Figure 1, under normal circumstances, the piston rod 3 and the second rod 11 are in contact with each other, and the second case 8, which is integrated with the first rod 5, and the second rod 11 are spaced apart.

[0029] An O-ring 12 made of acrylic rubber (ACM) is interposed between the thermo-element 2 and the first case 4 to seal the portion that fits with the engine. The first case 4, together with the thermo-element 2, is attached by crimping to a support plate 13, which serves as a support member, and the entire thermo-actuator 1 is fixed and supported.

[0030] (First Case) The first case 4 is made of stainless steel (SUS430) and is a cylindrical case with one open end 4a and the other end formed with a tapered portion 4b where the diameter is reduced midway. The open end 4a of this first case 4 is attached to the thermo-element 2 and the support plate 13. A bearing 41 made of polyphenylene sulfide (PPS resin) is attached to the tapered portion 4b of the first case 4, and the first rod 5 (described below) is configured to be able to freely protrude and retract through this bearing 41. An O-ring 42 made of EPDM (ethylene propylene diene monomer), a synthetic rubber, is attached and sealed to the outside of the bearing 41 of the tapered portion 4b (the side toward which the first rod 5 protrudes) to prevent external liquid and dust from entering the thermoactuator 1.

[0031] (First Rod) The first rod 5 is made of a bar material of stainless steel (SUS430), and has a push rod 51 connected to the louver fitted to the tip thereof.

[0032] (Main Spring) The first spring 6, which serves as the main spring, is a coil spring made of stainless steel wire (SUS304), with one end abutting against the inner wall of the first case 4 on the reduced diameter portion 4b side, and the other end hooked onto the second case 8, which is connected to the first rod 5. As described above, the first spring 6 therefore biases the first rod 5 in the retracting direction, that is, in the direction of drawing the first rod 5 into the first case 4 when the temperature drops. The biasing force of the first spring 6, which serves as the main spring, is set to 48 to 55 N.

[0033] (Second Case) The second case 8 is made of the same stainless steel (SUS430) as the first rod 5, and is an integrally connected member to the first rod 5. The second case 8 is a cylindrical member with one end closed, and has a recess 81 formed in the center for inserting the second rod 11, with the outside of the recess 81 providing a space for inserting the second spring 9. The open end of the second case 8 is also formed with a flange-shaped latch portion 82 folded outward, onto which the aforementioned first spring 6 is latched.

[0034] (Auxiliary Spring) The second spring 9, which serves as an auxiliary spring, is a coil spring made of stainless steel wire (SUS304) like the first spring 6, and when compressed, one end abuts against the inner wall of the closed end of the second case 8, and the other end abuts against a retaining ring 10 hooked onto the second rod 11. The retaining ring 10 will be described later. The biasing force of the second spring 9, which serves as an auxiliary spring, is set to 55 to 93 N, which is greater than the biasing force of the first spring 6, in order to counteract the biasing force of the first spring 6 and hold the louvers in the open state.

[0035] (Second rod) The second rod 11 has an end 111 that expands in diameter in a mushroom shape on the side that is inserted into the recess 81, and is hooked with a stainless steel wire ring 14 to prevent the second rod 11 from coming off the recess 81. In addition, the other end of the second rod 11 on the piston rod 3 side is formed with a tapered portion 112 whose diameter gradually expands as it approaches the piston rod 3 side, and a retaining ring 10 is hooked on this tapered portion 112.

[0036] <Lock mechanism> Next, a retaining ring 10, which is a locking mechanism (locking member) according to an embodiment of the present invention, will be described with reference to Fig. 2. Fig. 2(a) is an enlarged view of part A in Fig. 1 under normal conditions, and Fig. 2(b) is an enlarged view of part A in Fig. 1 under abnormal load conditions. Fig. 2(c) is a plan view showing the retaining ring 10 under normal conditions, and Fig. 2(d) is a plan view showing the retaining ring 10 under abnormal load conditions.

[0037] As shown in Figure 2, the retaining ring 10, which is a locking mechanism (locking member) according to an embodiment of the present invention, is C-shaped with a slit 10a. If the louvers, which open and close in conjunction with the extension and retraction of the first rod 5 via the push rod 51, become stuck or difficult to move due to the intrusion of foreign matter or other factors, a malfunction occurs. The thermo-element 2 pushes out the piston rod 3, causing a reaction via the push rod 51 connected to the louvers, resulting in an abnormal axial force of a predetermined magnitude (100 N or greater, as described below) acting on the first rod 5. Since the second case 8 and the second rod 11 are spaced apart, the abnormal axial force acting on the first rod 5 acts on the retaining ring 10 via the second spring 9, which is compressed so that the steel wires come into contact with each other.

[0038] When an abnormal axial force acts on the retaining ring 10, the retaining ring 10 is hooked onto the tapered portion 112 of the second rod 11, so the retaining ring 10 moves in the direction of the arrow in Figure 2(b) of the tapered portion 112. As a result, the slit 10a deforms and widens, causing the retaining ring 10 to fall off the tapered portion 112 of the second rod 11, thereby releasing the locking mechanism. The load at which the slit 10a of the retaining ring 10 begins to widen is set to 100 N, as described below. Of course, it goes without saying that the retaining member according to the present invention may be designed to release the locking by breaking rather than by deformation.

[0039] Next, a retaining ring 10', which is a locking mechanism (locking member) according to another embodiment of the present invention, will be described using Figure 3. Figure 3(a) is a view corresponding to the enlarged view of part A in Figure 1, showing the retaining ring 10' according to another embodiment under normal conditions, and Figure 3(b) is a view corresponding to the enlarged view of part A in Figure 1, showing the retaining ring 10' under abnormal axial force. Figure 3(c) is a plan view showing the retaining ring 10' under normal conditions, and Figure 3(d) is a plan view showing the retaining ring 10' under abnormal axial force.

[0040] The retaining ring 10' according to another embodiment differs from the aforementioned retaining ring 10 in that the thickness of the retaining ring 10' is thinner than the thickness of the aforementioned retaining ring 10, and that the retaining ring 10', which is a locking member, is not hooked on the tapered portion 112 but on the first locking portion 113 (locking portion) of the second rod 11. Therefore, only these points will be described, and the same components as those described above will be denoted by the same reference numerals and description thereof will be omitted.

[0041] The thickness of the retaining ring 10' is thinner than the thickness of the retaining ring 10, and it is hooked onto a first locking portion 113 formed on the lower end of the second rod 11 on the thermo-element 2 side. Therefore, when an abnormal axial force acts on the retaining ring 10', as shown by the arrow direction in Figure 3(b), the retaining ring 10' does not shift along the tapered portion 112 and move, but rather the ring-shaped retaining ring 10' falls outward while hooked onto the first locking portion 113 and deforms into a truncated cone shape, which results in the retaining ring 10' falling off the first locking portion 113 of the second rod 11, and the locking mechanism is released.

[0042] As described above, the locking mechanism has been described as an example in which the lock is released when the locking member, namely, the retaining ring 10 or the retaining ring 10', deforms or breaks when an axial force greater than a predetermined value is applied to the first rod 5. However, the locking mechanism of the present invention is not limited to a mechanism in which the lock is released when the retaining member deforms or breaks, as long as the lock is released when an axial force greater than a predetermined value is applied to the first rod 5.

[0043] Next, referring to FIG. 4, a locking mechanism according to another embodiment in which the lock is not released by deformation or fracture of the locking member will be described. FIG. 4(a) is a view corresponding to the enlarged view of portion A in FIG. 1, showing the locking mechanism according to another embodiment, and FIG. 4(b) is a view corresponding to the enlarged view of portion A in FIG. 1, showing the locking mechanism according to another embodiment when an abnormal axial force is generated. The locking mechanism according to this embodiment differs from the previously described locking mechanism (the locking members, i.e., the retaining ring 10 and the retaining ring 10') in that there is no locking member itself, and the second spring 9' according to a modified auxiliary spring is directly hooked onto the second locking portion 114 of the second rod 11. Therefore, this point will be described, and the same components will be designated by the same reference numerals and will not be described again.

[0044] The locking mechanism according to this embodiment shown in Figure 4 is a modified second spring 9' in which the diameter of the spring steel wire at the lower end of the second spring 9 on the thermo-element 2 side is reduced, and a second locking portion 114 is formed at the lower end of the second rod 11 on the thermo-element 2 side, and the spring steel wire of the second spring 9' is directly hooked onto this second locking portion 114.

[0045] For this reason, when an abnormal axial force acting on the first rod 5 is transmitted to the second spring 9', the lower end of the second spring 9', whose spring steel wire has a reduced diameter, is pressed and spreads out over the second locking portion 114, as shown by the arrow in Figure 4(b), and falls off the second locking portion 114 of the second rod 11, thereby releasing the lock of the locking mechanism. Therefore, a locking member is not required, the locking mechanism can be configured simply and inexpensively, and there is no risk of the locking member getting caught midway, so the louver can be reliably biased by the auxiliary spring 9' to hold it in the open state.

[0046] <Operation of Thermoactuator> Next, the operation of the thermoactuator 1 will be described using Figures 5 and 6. Figure 5 is a diagram showing normal operation of the thermoactuator 1, where (a) shows the state before the temperature rises and (b) shows the state after the temperature rises. Figure 6 is a diagram showing operation of the thermoactuator 1 after a malfunction occurs, where (a) shows the operation when the malfunction occurs, (b) shows the operation when the malfunction is resolved, and (c) shows the operation when the louver is open.

[0047] 5(a) and 5(b), in normal operation of the thermoactuator 1, the piston rod 3 protrudes due to the expansion of wax in the housing 20 as the temperature around the thermoelement 2 rises. This causes the piston rod 3 to push out the second rod 11.

[0048] At this time, as described above, the second case 8, which is integral with the first rod 5, and the second rod 11 are separated by a separation distance D1. However, as described above, the second spring 9 is housed in the second case 8 in a compressed state. Therefore, the protruding force (lift force) of the piston rod 3 is transmitted to the second rod 11, and then transmitted to the second spring 9 via the retaining ring 10 hooked to the tapered portion 112, and then transmitted from the closed end of the second case 8 to the first rod 5 integral therewith, lifting it up by a lift distance L1 (the increase in the protruding length of the first rod 5), operating in the direction of opening the louver. In the illustrated embodiment, it is assumed that the lift distance L1 is 8.0 mm and the separation distance D1 is 1.0 mm.

[0049] When the temperature drops, the wax inside the housing 20 shrinks as the temperature around the thermo-element 2 drops, causing the piston rod 3 to retract into the housing 20. Then, the biasing force of the first spring 6, which is the main spring, lifts the first rod 5 and second case 8 down toward the piston rod 3, and the second rod 11 is also lifted down in a domino effect via the second spring 9.

[0050] In this way, during normal operation when no malfunction occurs, the thermo-element 2 senses a change in oil temperature and repeats the operations shown in Figures 5(a) and 5(b), opening and closing the louver connected to the push rod 51. As mentioned above, the biasing force of the first spring 6, which is the main spring, is set to 48 to 55 N < the biasing force of the second spring 9, which is the auxiliary spring, is set to 55 to 93 N, so the second spring does not flex.

[0051] On the other hand, if the louvers become stuck due to foreign matter getting caught in them, causing a malfunction, the push rod 51 and first rod 5 connected to the louvers will also be locked. If the temperature rises in this state, the wax in the thermo-element 2 will expand, causing the piston rod 3 to protrude. However, if the louvers are stuck, the first rod 5 will also protrude and will not be able to lift up, and an abnormal axial force will be transmitted to the first rod 5 and thermo-element 2 as a reaction to the lift force (ejection force) generated by the piston rod 3. If this abnormal axial force transmitted to the thermo-element 2 becomes higher than the biasing force of the second spring 9 (55 to 93 N) and exceeds 100 N, there is a risk that the housing 20 will deform, making continued use impossible.

[0052] Therefore, as described above, the slit 10a is designed to deform and widen when an abnormal axial force exceeding 100 N acts on the retaining ring 10. That is, as shown in Fig. 6(a), if a malfunction such as sticking of the louvers occurs, the distance between the second case 8 and the second rod 11 decreases, the second spring 9 compresses, and the steel wires of the second spring 9 come into contact with each other, causing the slit 10a in the retaining ring 10 to deform and widen (see also Fig. 2). As shown in Fig. 6(b), the retaining ring 10 falls off the tapered portion 112 of the second rod 11, releasing the locking mechanism. As shown in Fig. 6(c), the biasing force of the second spring 9 prevents the first rod 5 from retracting and sinking, maintaining the open state of the louvers even when the ambient temperature of the thermo-element 2 drops. Of course, the biasing force of the second spring 9 may indirectly bias the first rod 5, and the second spring 9 need not directly press the first rod 5. Furthermore, the release of the locking mechanism of the present invention can be achieved by appropriately selecting the spring constant of the second spring 9 and the strength of the retaining ring 10 so that the retaining ring 10 falls off when an abnormal axial force acts on it, regardless of whether the steel wires of the second spring 9 are in contact with each other.

[0053] In this way, with the thermoactuator 1 according to this embodiment, when an axial force of a predetermined magnitude or greater is applied to the first rod 5, the retaining ring 10, which is a locking member, is released from its locking position, causing the louvers to malfunction due to the entrapment of foreign matter, etc., and even after the temperature around the thermoelement 2 drops, the force of the second spring 9 can be used to maintain the predetermined protrusion length of the first rod 5, which allows the louvers to be kept in a minimum open state, thereby preventing overheating.

[0054] As mentioned above, the locking member may be a retaining ring 10', and when an abnormal axial force acts on the retaining ring 10', the ring-shaped retaining ring 10' may fall outward while hooked on the first locking portion 113, deform into a truncated cone shape, and eventually expand, as shown by the arrow direction in Figure 3(b), and the retaining ring 10' may fall off the first locking portion 113 of the second rod 11, thereby releasing the lock of the locking mechanism.

[0055] Furthermore, as mentioned above, when the abnormal axial force acting on the first rod 5 is transmitted to the second spring 9', the lower end of the second spring 9', whose diameter has been reduced, is pressed, as shown by the arrow direction in Figure 4 (b), and expands beyond the second locking portion 114, and falls off from the second locking portion 114 of the second rod 11, thereby releasing the lock of the locking mechanism.

[0056] On the other hand, according to the thermoactuator 1, in normal operation as shown in Figure 5, the movement of the second rod 11 is transmitted to the first rod 5 via the second spring 9, and when a malfunction of the louver occurs, the first rod 5 and the second rod 11 come into contact with each other, thereby transmitting the movement of the second rod 11 to the first rod 5. As a result, it is possible to successfully achieve both the ability to sense an axial force of a predetermined level or more on the first rod 5 to hold the louver in an open state, and the ability to reliably transmit the movement of the piston rod 3, which protrudes as the ambient temperature rises, to the first rod 5.

[0057] Furthermore, as shown in FIG. 6( c), the louvers are kept open at all times after an abnormal axial force occurs, i.e., the louvers remain open even at low temperatures, making it possible for the user to become aware of an abnormality and providing an incentive to take the vehicle to a repair shop or the like while the engine is running.

[0058] Figure 7 shows the operation of the thermoactuator 1 when it is fully open, where (a) shows the open lock state in which the second spring 9, the same as in Figure 6(c), holds the first rod 5 in a predetermined lift state and holds the louver in an open state, and (b) shows the fully open state.

[0059] As shown in Fig. 7(a), the second spring 9 holds the first rod 5 in a lifted state at a predetermined projection length, and the louvers are held in an open-locked state, as shown in Fig. 7(b), so that when the oil temperature rises, the projection of the piston rod 3 is transmitted to the first rod 5 via the second rod 11, causing the first rod 5 to project further from the open-locked state shown in Fig. 7(a) and the louvers to enter a fully open state. This is because, even in a state where some sticking force remains after the thermo-element 2 has released a malfunction such as sticking, and a certain amount of lift cannot be obtained with the biasing force of the second spring 9, the thermo-element 2 (pellet) operates to open the louvers, thereby preventing engine overheating.

[0060] The thermoactuator 1 according to the embodiment of the present invention has been described in detail above, but the above-described and illustrated embodiments are merely specific examples of the present invention. Therefore, the technical scope of the present invention should not be interpreted as being limited by these embodiments. In particular, the materials of each component are merely examples, and it goes without saying that they can be appropriately changed to other materials having equivalent strength.

[0061] 1: Thermoactuator 2: Thermoelement 20: Housing 3: Piston rod 4: First case 4a: Open end 4b: Reduced diameter portion 41: Bearing 42: O-ring 5: First rod 51: Push rod 6: First spring (main spring) 8: Second case (first rod) 81: Recess 82: Latch portion 9, 9': Second spring (auxiliary spring) 10, 10': Retaining ring (locking member, locking mechanism) 10a, 10a': Slit 11: Second rod 111: End 112: Tapered portion 113: First locking portion (locking portion) 114: Second locking portion (locking portion) 12: O-ring 13: Support plate 14: Wiring

Claims

1. A thermoactuator which is a temperature sensing control device comprising: a thermoelement having a piston rod which protrudes as the surrounding temperature rises; a case attached to the thermoelement; a first rod which is attached to the case so as to be able to protrude and retract freely and which protrudes and retracts in conjunction with the piston rod; a main spring which urges the first rod in the retracting direction, and further an auxiliary spring which is locked in a compressed state by a locking mechanism, wherein the locking mechanism is configured to be released when a predetermined or greater axial force is applied to the first rod due to a reaction force from the thermoelement pushing out the piston rod caused by a malfunction of a driven member which is driven in conjunction with the first rod, and wherein the first rod which has been urged to protrude by the released auxiliary spring is retracted and does not retract.

2. A thermoactuator as claimed in claim 1, characterized in that the locking mechanism is a mechanism in which the locking is released when the locking member deforms or breaks when a load equal to or greater than a predetermined level is applied.

3. A thermoactuator as described in claim 2, characterized in that the locking member is hooked onto a tapered section whose diameter gradually increases, a slit is formed in the locking member, and when a predetermined or greater axial force is applied to the first rod, the locking member moves along the tapered section, widening the slit and causing the locking member to fall off, thereby releasing the lock.

4. The thermoactuator according to claim 2, wherein the locking member is hooked onto a locking portion, and when a predetermined axial force or more is applied to the first rod, the locking member comes off the locking portion and falls off, thereby releasing the lock.

5. A thermoactuator as described in claim 1, characterized in that the locking mechanism is such that the auxiliary spring is directly hooked onto a locking portion, and when a predetermined or greater axial force is applied to the first rod, the auxiliary spring is disengaged from the locking portion, thereby releasing the lock.

6. A thermoactuator as claimed in any one of claims 1 to 5, further comprising a second rod interposed between said piston rod and said first rod and adapted to move in a protruding and retracting manner in conjunction with said piston rod, wherein when no axial force of a predetermined level or more is acting on said first rod, there is a gap between said first rod and said second rod, and the motion of said second rod is transmitted to said first rod via said auxiliary spring, and when an axial force of a predetermined level or more is acting on said first rod, the locking mechanism is released, there is no longer said gap, and said first rod and said second rod come into contact with each other, thereby transmitting the motion of said second rod to said first rod.

7. A thermoactuator as described in claim 6, characterized in that when a predetermined axial force or more is applied to the first rod, the locking mechanism is released and the protruding length of the first rod is maintained by the force of the auxiliary spring, and then the protruding motion of the piston rod caused by an increase in the surrounding temperature is transmitted to the first rod via the second rod, causing the first rod to protrude further.

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