Belt drive mechanism for cooling tower supply fan

Abstract

The present invention provides a belt drive mechanism for a cooling tower blower, which is a drive mechanism for a blower using a flat belt. A tension adjustment part for suppressing the bending travel of the belt is adopted, and a belt guide part is additionally provided near the driven-side pulley. Even if the reverse travel state of the belt continues for a long time, deterioration and damage of the belt can be prevented. For the belt (13) which is a flat belt, the tension adjustment part (14) prevents the belt (13) from flexing, suppresses the bending travel of the belt (13) during travel, and positions the belt guide part (15) near the driven-side pulley (12), aligning the uppermost position of the guide surface with the lower limit position of the belt travel possible range on the outer peripheral surface of the driven-side pulley. Thus, even if the state where the bending travel suppression control of the tension adjustment part (14) is ineffective continues under the impeller reverse rotation state, the position of the belt (13) in contact with each of the drive-side and driven-side pulleys can be appropriately restricted from excessively dropping by the belt guide part (15), and the burden involved in maintenance can be reliably reduced, such as reducing the replacement frequency of the belt (13).

Description

Technical Field

[0001] The present invention relates to a cooling tower in which a heat medium of a recycled liquid phase exchanges heat with air in a heat exchange section, and more particularly to a belt drive mechanism for driving a blower for ventilation in the cooling tower by an electric motor. Background Art

[0002] Generally, in a cooling tower installed outdoors for the purpose of cooling a heat medium of a liquid phase such as water that is recycled in a factory or an air conditioning equipment, etc., in a heat exchange section inside the cooling tower, a structure is provided in which air (external gas) taken in from the outside directly or indirectly exchanges heat with the heat medium as the fan (blower) operates for cooling.

[0003] The blower used in such a cooling tower is usually a blower that rotationally drives an impeller by an electric motor. Conventionally, a blower in which the electric motor and the impeller are separately arranged by interposing a driving force transmission mechanism such as a belt drive mechanism between the impeller and the electric motor is mainly used. And, as such a driving force transmission mechanism, a belt drive mechanism in which pulleys are respectively arranged on the electric motor side and the impeller side and a belt is wound between these pulleys is mostly used.

[0004] In such a conventional belt drive mechanism for a cooling tower blower, a V-belt is generally used as the belt for transmitting the driving force. When a V-belt is used in the belt drive mechanism, due to the characteristic that the V-belt is fitted into the V-shaped grooves on the outer circumferences of the respective pulleys on the electric motor side or the blower side to transmit the driving force, it is difficult for the belt to bend and travel or fall off from the pulley during the travel of the belt. However, due to the structure of the V-belt whose size in the thickness direction becomes large, the bending rigidity of the belt is large. Therefore, along with this, there is a problem that the loss involved in driving force transmission becomes large.

[0005] In addition, if the belt elongates and deflects due to the aging of the belt, a part of the belt easily floats from the surfaces of the respective pulleys on the electric motor side and the fan side to become a sliding state, and the transmission efficiency of the belt decreases. Therefore, it is necessary to periodically adjust the axial distance between the electric motor and the fan, etc. to maintain the tension state of the belt constant, and there is also a problem that maintenance effort is required.

[0006] The present applicant has proposed a belt drive mechanism that, in response to the problems of the mechanism using such a V-belt, uses a flat belt as the drive belt for the blower, realizes high efficiency of impeller drive, and can achieve maintenance-free. As an example of such a belt drive mechanism for a cooling tower blower, there is the belt drive mechanism disclosed in Japanese Patent Application Laid-Open No. 2019-94940.

[0007]

Prior Art Documents

[0008]

Patent Documents

[0009]

Patent Document 1

[0010]

Problems to be Solved by the Invention

[0011] As shown in the above patent document, in a conventional belt drive mechanism for a cooling tower blower, a flat belt is used as a drive belt for the blower, and a tension adjustment portion that suppresses belt deflection and bending travel when the belt travels is disposed at an appropriate position. Thus, in addition to improving drive efficiency based on the use of a flat belt and enabling long-term maintenance-free operation, even when the impeller of the blower rotates in the reverse direction and the travel direction of the belt changes, belt deviation can be suppressed.

[0012] That is, in a situation where the blower of the cooling tower stops due to the motor stopping, due to the wind pressure applied to the impeller from strong winds from the outside, exhaust gas from an adjacent cooling tower, etc., the impeller rotates in a direction opposite to the normal operation when driven by the motor. Even if the belt of the belt drive mechanism travels in the opposite direction, as long as it stays for a short time, the relationship between each pulley and the belt hardly changes, and it is a structure that can shift to an appropriate normal blowing state when the operation of the motor starts again.

[0013] However, in the relationship between the operating state of the main equipment that uses the heat medium for heat exchange in the cooling tower and the heat exchange capacity of the cooling tower, if the period during which the blower of the cooling tower is stopped and controlled becomes long, along with this, the impeller rotates in the opposite direction due to other influences, and the state where the belt also travels in the opposite direction continues for a long time. With respect to the operation in the direction opposite to the normal direction of the belt, the tension adjustment portion does not effectively function to suppress bending travel control in terms of its structure. Accordingly, the deviation caused by the self-weight of the belt gradually decreases. Soon, the belt contacts the flange of the pulley on the impeller side and warps, and there is a problem that the belt side end portion (ear portion) may be worn, chipped, or broken, resulting in a reduction in the ability to transmit the driving force of the belt and a decrease in the product life of the belt.

[0014] The present invention has been completed to solve the above problems, and an object thereof is to provide a belt drive mechanism for a cooling tower blower. In a drive mechanism for a blower that uses a flat belt, a tension adjustment portion that suppresses bending travel of the belt is adopted, and a belt guide portion is additionally provided near the driven-side pulley. Even if the state of traveling in the opposite direction of the belt continues for a long time, deterioration and damage caused by belt deviation can be prevented, and maintenance-free operation can be reliably achieved.

[0015]

Means for Solving the Problems

[0016] The belt drive mechanism for a cooling tower blower involved in the present invention is a belt drive mechanism for a cooling tower blower, which is a belt drive mechanism for transmitting the rotational driving force from a motor to the impeller of a blower in a cooling tower where heat exchange is performed between the air inhaled from the outside by induced ventilation of the blower and the hot medium of the object to be cooled. It is characterized by comprising: a driving-side pulley integrally disposed with the output shaft of the motor; a driven-side pulley integrally disposed with the rotating shaft in the impeller of the blower; a belt, which is an annular flat belt stretched between the driving-side pulley and the driven-side pulley; a tension adjustment portion, which contacts the outer peripheral surface of a specified portion in the slack-side section of the belt traveling in a specified forward direction in the forward rotation state of each pulley when the blower performs induced ventilation, prevents the belt from flexing, and controls the movement of the belt to suppress bending travel; and a belt guiding portion, which restricts the downward movement of the belt near the driven-side pulley. The tension adjustment portion has a tension pulley pressed against the outer peripheral surface of the specified portion of the belt and capable of rotating, and is disposed such that the tension pulley is located within a specified area close to the driven-side pulley. The belt guiding portion has a guiding surface, which is disposed on the lower side of a specified portion in the tension-side section of the belt traveling in the forward direction, and the guiding surface is disposed such that at a specified position closer to the driven-side pulley than the tension pulley of the tension adjustment portion, the uppermost position of the guiding surface is at the same height as the lower limit position of the belt traveling possible range on the outer peripheral surface of the driven-side pulley.

[0017] As described above, according to the present invention, for the flat belt that transmits the rotational driving force from the driving-side pulley integrally connected to the motor output shaft to the driven-side pulley integrally connected to the impeller, the tension pulley of the tension adjustment portion prevents the belt from flexing, suppresses the bending travel of the traveling belt, and the belt guiding portion is located near the driven-side pulley, and the uppermost position of the guiding surface is aligned with the lower limit position of the belt traveling possible range on the outer peripheral surface of the driven-side pulley. Thus, even when the effective state of the bending travel suppression control of the tension adjustment portion continues for a long time in the reverse rotation state of the impeller due to external influences and the like when the blower operation stops, the belt guiding portion can appropriately restrict the excessive downward movement of the position of the belt in contact with the driving-side and driven-side pulleys, can maintain the belt position within the traveling possible range on the outer peripheral surface of each pulley, can prevent wear and damage to the side end of the belt caused by contact and warping between the belt end and the pulley flange portion, and the belt will not deteriorate even in the cooling tower operation state where it is assumed that the reverse rotation of the blower impeller is frequent, and can reliably reduce the burden involved in maintenance, such as reducing the replacement frequency of the belt.

[0018] In addition, in the belt drive mechanism for a cooling tower blower according to the present invention, as needed, for the belt that travels in the positive direction in the forward rotation state of the blower, the tension adjustment unit controls to suppress the bending travel of the belt, so that the belt travels at a substantially central portion in the vertical direction on the outer peripheral surface of the driven pulley, and the lower end portion of the belt is separated from the lower limit position of the possible travel range of the belt. The belt guide portion is configured such that the uppermost position of the guide surface is restricted to a configuration state that does not reach a position above the lower limit position of the possible travel range of the belt of the driven pulley side, and the guide surface is separated from the belt traveling in the positive direction.

[0019] Thus, according to the present invention, in the forward rotation state of the blower impeller, when the belt travels in the positive direction, the tension adjustment unit suppresses the bending travel of the belt, so that the belt does not reach the lower limit position of the possible travel range of the driven pulley. The guide surface of the guide portion at the same height as the lower limit position does not contact the belt. On the other hand, when the impeller rotates in the reverse direction and the state where the belt travels in the reverse direction continues, when the belt that has shifted and lowered reaches the lower limit position of the possible travel range, it becomes a state of being guided in contact with the guide surface of the guide portion, and becomes a state where the belt does not further descend. Therefore, in the case of reverse rotation of the impeller, it is possible to prevent contact and lifting of the belt with the flange of the pulley, suppress deterioration of the belt, and also prevent the guide surface from contacting the belt in the forward rotation state of the impeller, and it is possible to prevent minute wear of the guide surface and the side end portion of the belt caused by the contact between the guide surface and the belt, achieve long life of the guide portion and the belt, and further suppress dust generation caused by wear.

[0020] In addition, in the belt drive mechanism for a cooling tower blower according to the present invention, as needed, the belt guide portion has a guide roller that is rotatably supported, and the cylindrical surface portion on the outer periphery of the guide roller is set as the guide surface. The guide roller sets the roller rotation axis direction to a direction perpendicular to the rotation axis direction of the driven pulley side, and arranges the tangential direction of the uppermost position of the guide surface to be parallel to the belt travel direction at the specified position.

[0021] Thus, according to the present invention, a rotatable guide roller is provided in the belt guide portion. The cylindrical surface portion on the outer periphery of the guide roller constitutes the guide surface and can contact the belt. The tangential direction of the uppermost portion of the guide surface is parallel to the belt travel direction, etc., and is appropriately configured with respect to the belt. The guide roller that rotates along with the travel of the belt rolls and contacts the lower end portion of the belt that travels in the direction opposite to the normal direction as the impeller rotates in the reverse direction, and guides the moving belt to the driven pulley side at an appropriate height, suppressing the downward offset of the belt in the pulley. Therefore, it is possible to easily guide the belt and prevent the belt from descending and the accompanying contact between the belt and the flange portion of the pulley, etc., and suppress the deterioration of the belt by minimizing the friction between the guide surface and the belt.

[0022] In addition, in the belt drive mechanism for a cooling tower blower according to the present invention, if necessary, the guide roller is arranged so that its vertical position can be adjusted, so that regardless of the change in the outer diameter of the guide surface, the uppermost position of the portion of the guide surface that can contact the belt end is made to coincide with the lower limit position of the belt travel possible range on the outer peripheral surface of the driven pulley.

[0023] Thus, according to the present invention, the vertical position of the guide roller is adjusted so that the portion of the guide surface of the guide roller that can contact the belt coincides with the lower limit position of the belt travel possible range on the outer peripheral surface of the driven pulley. In the reverse rotation state of the impeller, when the belt travels in the opposite direction, the guide surface of the guide roller can contact the belt that has dropped to the lower limit position. Therefore, even when the outer diameter of the guide surface of the guide roller decreases due to wear caused by contact with the belt, it can still contact the belt in an appropriate position adjustment and continue to guide it. When the belt travel direction becomes the opposite direction, the belt can be appropriately guided by the guide portion to suppress the descent, and the state of not deteriorating the belt can be maintained for a long time.

[0024] In addition, in the belt drive mechanism for a cooling tower blower according to the present invention, if necessary, it includes a pedestal portion. The pedestal portion is installed on the support frame that supports the blower on the cooling tower and is located between the output shaft of the motor and the rotation shaft of the blower impeller. The tension adjustment portion is installed at a first specified position of the pedestal portion and is arranged between the drive pulley and the driven pulley. The belt guide portion is installed at a second specified position of the pedestal portion and is arranged near the driven pulley.

[0025] Thus, according to the present invention, the pedestal portion is installed on the support frame that supports the blower. The tension adjustment portion is installed on this pedestal portion to adjust the tension of the belt and suppress the bending travel. In addition, the belt guide portion is also installed on the same pedestal portion. When the belt travel direction becomes the opposite direction in the reverse rotation state of the impeller, the belt guide portion guides the belt toward the driven pulley at an appropriate height. Therefore, the pedestal portion installed on the support frame can support the tension adjustment portion and the belt guide portion, reliably fix the tension adjustment portion and the belt guide portion that receive the force from the belt. In the tension adjustment portion, the parallelism deviation of the tension pulley relative to other pulleys can be prevented, and in the belt guide portion, displacement caused by the force applied by the belt from the guide surface is difficult to occur, and the adverse effect of the belt on the guiding accuracy and the accompanying deterioration caused by the contact between the belt and the flange portion of the pulley can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a top view of a cooling tower with a belt drive mechanism according to an embodiment of the present invention applied.

[0027] Figure 2Explanation diagram of the open state of the upper part of the cover of the belt drive mechanism according to an embodiment of the present invention.

[0028] Figure 3 Explanation diagram of the support state of the motor in the belt drive mechanism according to an embodiment of the present invention.

[0029] Figure 4 Explanation diagram of the forward travel state of the belt in the belt drive mechanism according to an embodiment of the present invention.

[0030] Figure 5 Explanation diagram of the reverse travel state of the belt in the belt drive mechanism according to an embodiment of the present invention.

[0031] Figure 6 Explanation diagram of the belt guiding state when the guide roller in the belt drive mechanism according to another embodiment of the present invention is not worn.

[0032] Figure 7 Explanation diagram of the belt guiding state when the guide roller in the belt drive mechanism according to another embodiment of the present invention is being worn. Detailed implementation mode

[0033] Hereinafter, based on the above Figures 1 to 5 A belt drive mechanism according to an embodiment of the present invention will be described. In this embodiment, an example of a cooling tower in which two heat exchange units are arranged opposite each other across a central part of a direct / alternating current type (cross-flow type) induced draft fan will be described.

[0034] As shown in the above respective figures, the belt drive mechanism 10 according to this embodiment is used to transmit the driving force from the motor 70 to the blower 60 of the cooling tower 50. Specifically, it includes: a driving-side pulley 11 that is integrally provided with the output shaft 71 of the motor 70; a driven-side pulley 12 that is integrally provided with the rotating shaft of the impeller 61 of the blower 60; a belt 13 that is stretched between the driving-side pulley 11 and the driven-side pulley 12; a tension adjustment unit 14 that contacts the belt 13 to prevent the belt 13 from flexing and controls the movement of the belt 13 to suppress bending travel; a belt guiding unit 15 that restricts the downward movement of the belt 13 near the driven-side pulley 12; a support device 16 that supports the motor 70 so that it can be position-adjusted to the side of the blower 60; and a cover 17 that covers the driving-side pulley 11, the driven-side pulley 12, the belt 13, the tension adjustment unit 14, and the belt guiding unit 15.

[0035] The cooling tower 50 applying the belt drive mechanism 10 according to the present embodiment is a direct / alternating current type (cross-flow type), in which two heat exchange parts (not shown) are arranged opposite to each other across the central ventilation space, and the induced ventilation of the blower 60 disposed at the exhaust side opening in the upper part of the center is utilized to suck external air into each heat exchange part from the side, and heat exchange is performed between the air and the heat medium to be cooled. For the parts of the cooling tower 50 other than the belt drive mechanism 10, such as the heat exchange part that performs heat exchange between the circulating water and the external air, the upper water tank and the lower water tank disposed above and below the heat exchange part, and the control system that controls the driving of the motor 70, etc., are well-known structures, and detailed descriptions are omitted.

[0036] On the side of the blower 60 in the cooling tower 50, a motor 70 is disposed via a support device 16. Moreover, the rotation of the output shaft 71 of the motor 70 is transmitted to the impeller 61 of the blower 60 through the belt drive mechanism 10, and the impeller 61 rotates to perform induced ventilation.

[0037] In addition, a support frame 63 for supporting the blower 60 on the cooling tower 50 and a pedestal part 62 that is mounted on the support frame 63 and supports the tension adjustment part 14 and the belt guide part 15 are provided in the cooling tower 50. Among them, the pedestal part 62 is disposed between the output shaft 71 of the motor 70 and the rotation shaft 61a of the blower impeller, and by connecting the tension adjustment part 14 and the belt guide part 15 to the support frame 63, reliable fixation can be achieved.

[0038] The driving side pulley 11 is fixedly provided on the output shaft 71 of the motor 70, can rotate integrally with the output shaft 71, rotates along with the rotation of the output shaft 71 of the motor 70, and makes the wound belt 13 travel between the driven side pulley 12.

[0039] The driven side pulley 12 is fixedly provided on the rotation shaft 61a of the impeller 61 in the blower 60, and can rotate integrally with the impeller 61. The outer diameter of the driven side pulley 12 is formed to be larger than the outer diameter of the driving side pulley 11, and it is a structure in which the impeller 61 rotates at a speed reduced to a lower speed relative to the output shaft 71 of the motor 70.

[0040] The belt 13 is formed as an endless flat belt, which is installed between the driving-side pulley 11 and the driven-side pulley 12, travels along with the rotation of the driving-side pulley 11, and causes the driven-side pulley 12 to rotate. The traveling direction of the belt 13 is the positive direction in which the drive belt 13 moves in a manner of transmitting the rotation of the driving-side pulley 11 to the driven-side pulley 12 in the normal rotation state of each pulley when the induced draft fan 60 performs induced ventilation. On the other hand, when the motor 70 stops, due to the wind pressure applied to the impeller 61 in the inner direction of the cooling tower 50, the impeller 61 rotates in the direction opposite to that in the normal operation driven by the motor. In the reverse rotation state where the driven-side pulley 12 rotates in the direction opposite to the normal rotation state, the direction in which the belt moves in a manner of transmitting the reverse rotation of the driven-side pulley 12 to the driving-side pulley 11 is the opposite direction.

[0041] The tension adjustment unit 14 is disposed between the driving-side pulley 11 and the driven-side pulley 12 at the upper part of the cooling tower 50, contacts the outer peripheral surface of the belt at a specified position in the slack side section of the belt 13 traveling in the positive direction in the normal rotation state of each pulley when the induced draft fan 60 performs induced ventilation, prevents the belt 13 from deflecting, and controls the movement of the belt 13 to suppress bending travel.

[0042] More specifically, the tension adjustment unit 14 includes: a base portion 14a fixedly provided on the gantry portion 62 at the upper part of the cooling tower 50; an arm portion 14b mounted at one end of the base portion 14a so as to be tiltable about an axis parallel to the rotation center axis of the driven-side pulley 12; a spring 14c as a biasing unit, with both ends respectively mounted on the other end of the base portion 14a and the front end of the arm portion 14b, biasing the front end of the arm portion 14b in the direction approaching the other end of the base portion 14a; and a tension pulley 14d rotatable about a central axis parallel to the rotation center axis of the driven-side pulley 12 at the front end of the arm portion 14b, and mounted such that the position in the central axis direction matches the position of the driven-side pulley 12.

[0043] The tension adjustment unit 14 is disposed so as to press the tension pulley 14d against the outer peripheral surface of the belt at a specified position in the slack side section between the driving-side pulley 11 and the driven-side pulley 12 of the belt 13 traveling in the positive direction.

[0044] In particular, the arm portion 14b of the tension adjustment portion 14 is biased by a spring 14c in a direction approaching the driven-side pulley 12 and tilts. In such a manner that the tension pulley 14d on the arm portion 14b presses the belt 13, the base portion 14a is mounted on the first specified position of the pedestal portion 62. A mechanism that moves the tension pulley 14d by tilting the arm portion 14b relative to the base portion 14a in a specified direction can compactly and centrally arrange the main part of the tension adjustment portion 14 other than the tension pulley 14d on the lower side of the portion where the belt 13 travels, and can suppress the air supply resistance of the air blower 60 caused by the arrangement of the tension adjustment portion 14 to the minimum necessary level.

[0045] In addition, the tension adjustment portion 14 is arranged such that the tension pulley 14d is located within a specified region close to the driven-side pulley 12.

[0046] Specifically, the tension adjustment portion 14 is arranged such that the rotation center of the tension pulley 14d is located within a region where the distance from the rotation center position of the driven-side pulley 12 is 35% or less, more preferably 24 - 31%, of the axial distance between the driving-side pulley 11 and the driven-side pulley 12.

[0047] The tension pulley 14d is in contact with the flat belt that travels between the pulleys and has a known mechanism for preventing bending travel, such as that described in Japanese Patent Publication No. 3680083 and Japanese Patent Publication No. 4365713, for preventing the flat belt from bending and traveling or shifting in the belt width direction.

[0048] The tension pulley 14d and the arm portion 14b are biased and tilted in a direction approaching the driven-side pulley 12, and come into contact with the belt 13 to apply tension. As a result, regardless of the traveling direction of the belt 13, the belt 13 can be maintained in a tensioned state without being deflected. In addition, with respect to the belt 13 that travels in the positive direction in the normal rotation state of each pulley, the tension pulley 14d controls the movement of the belt 13 in the width direction to suppress bending travel, etc., and can guide the belt 13 with respect to the driven pulley 12 in front of the belt traveling direction so that the belt 13 travels at approximately the center portion in the vertical direction of its outer peripheral surface. As a result, including the driving-side pulley 11, the vibration of the belt 13 in its width direction is minimized and the belt travels stably.

[0049] Moreover, by arranging the rotation center of the tension pulley 14d in the tension adjustment portion 14 in a specified region close to the driven-side pulley 12, even when the traveling direction of the belt 13 changes to the opposite direction, the movement of the belt 13 in the width direction that is not subject to the control related to the suppression of bending travel by the tension pulley 14d can be limited to the minimum, and the deviation of the belt 13 with respect to each pulley can be suppressed to a normal level.

[0050] The air supply fan of the cooling tower has the following characteristics: when the motor stops, the impeller can rotate in a direction opposite to that in normal operation driven by the motor against the wind pressure generated by the flow of external gas such as strong wind or the intake and exhaust of other cooling towers arranged in close proximity, acting on the impeller from the outside to the inside of the cooling tower.

[0051] The applicant has found that in such an air supply fan of a cooling tower, when a flat belt and a tension pulley with a corresponding mechanism for preventing bending travel are used in the same way as in a general air supply fan where the impeller does not reverse, when the impeller rotates in a direction opposite to that in normal operation, with the change in the relationship between the force applied from the tension pulley to the belt and the traveling direction of the belt, the function of preventing bending travel of the tension pulley cannot be exerted properly, and the disadvantages of the flat belt that is prone to deviation in the width direction are directly manifested. The possible range of belt travel on the outer peripheral surfaces of the respective pulleys on the driving side or the driven side deviates significantly, and it is easy to fall into a situation where the belt comes off.

[0052] In contrast, the applicant has confirmed that by setting the position of the tension pulley 14d of the tension adjustment unit 14 in the specified area closer to the driven side pulley 12 as described above, even if the impeller 61 reverses and the belt travels in the reverse direction due to the reverse rotation of the impeller 61, as long as the duration is short, the deviation of the belt 13 with respect to the respective pulleys on the driving side and the driven side can be suppressed to a minimum, and the mutual relationship between the belt 13 and the tension pulley 14d hardly changes. The function of preventing bending travel of the tension pulley 14d can be normally maintained when the induced ventilation of the air supply fan 60 based on the operation of the motor 70 resumes.

[0053] The belt guiding portion 15 has a guide roller 15a and a roller support portion 15b. The guide roller is arranged below a specified position near the driven side pulley in the section on the tension side of the belt 13 traveling in the positive direction. The roller support portion is installed at a second specified position on the frame portion 62 away from the tension adjustment portion 14, rotatably supports the guide roller 15a, and restricts the downward movement of the belt 13 near the driven side pulley 12.

[0054] The belt guiding portion 15 is a guiding surface configured such that the cylindrical surface portion of the outer periphery of the guide roller 15a can contact the side end portion of the belt 13 to guide the travel of the belt 13. Further, the belt guiding portion 15 is arranged such that the guiding surface of the guide roller 15a is located at a specified position closer to the driven side pulley 12 than the tension pulley 14d of the tension adjustment portion 14, and the uppermost position of the guiding surface is at the same height as the lower limit position of the possible range of belt travel on the outer peripheral surface of the driven side pulley.

[0055] In addition, the roller support portion 15b with the guide portion 15 supports the guide roller 15a on the gantry portion 62 so that the direction of the roller rotation axis of the guide roller 15a is perpendicular to the direction of the rotation axis of the driven-side pulley 12, and the tangential direction of the guide surface on the outer periphery of the roller is parallel to the belt traveling direction at the position of the guide surface.

[0056] By arranging the uppermost position of the guide surface of the guide roller 15a in the belt guide portion 15 to be consistent with the height of the lower limit position of the belt traveling possible range in the driven-side pulley 12 and not reaching a position above the lower limit position, when the impeller 61 is in the forward rotation state and the belt 13 traveling in the positive direction passes through the tension adjustment portion 14 and is suppressed from bending and traveling and does not deviate significantly from the central portion of the outer peripheral surface of the driven-side pulley 12, the guide surface of the guide roller 15a is separated from the belt 13 (refer to Figure 4 ).

[0057] In this way, in the normal forward traveling state of the belt 13, by not bringing the guide surface of the guide roller 15a into contact with the belt 13, it is also possible to prevent minute wear of the guide surface and the side end portion of the belt accompanying the contact between the guide surface and the belt 13, and long life of the belt guide portion 15 and the belt 13 can be achieved.

[0058] On the other hand, when the motor 70 stops and the impeller 61 rotates in the reverse direction and the traveling direction of the belt 13 becomes the opposite direction, the bending traveling suppression control based on the tension adjustment portion 14 is not performed, and thus the belt 13 easily shifts downward. If the belt 13 that has shifted downward reaches the lower limit position of the feasible traveling range, the belt 13 comes into contact with the guide surface of the guide roller 15a and is guided (refer to Figure 5 ), and it is a structure that prevents the belt 13 from further descending and prevents the belt 13 from contacting and lifting the flange portions of the respective pulleys 11 and 12.

[0059] The support device 16 supports the motor 70 in an adjustable position on the side of the blower 60. Specifically, the support device 16 is configured to include: a base portion 16a that is integrated with the blower 60; and an adjustment frame portion 16b that is mounted on the base portion 16a in a manner that enables fine adjustment of the position and orientation relative to the base portion 16a and fixes the motor 70.

[0060] This support device 16 has the following structure: at the stage of tilting due to elastic deformation of each part of the blower accompanying the dynamic load during the operation of the blower on the motor output shaft 71, by adjusting the position of the adjustment frame portion 16b relative to the base portion 16a, a support state of the motor 70 is obtained such that the rotation center axis of the drive-side pulley 11 is parallel to the rotation center axis of the driven-side pulley 12.

[0061] In a cooling tower, combinations of the sizes of a plurality of air blowers and the outputs of electric motors that drive the air blowers are set according to required performance. For a plurality of combinations of the air blowers and electric motors corresponding to the necessary performance of the cooling tower, while the electric motor 70 on the support device 16 is fixed in a state where its output shaft 71 is parallel to the air blower rotation shaft, the degree of inclination of the output shaft 71 when the respective parts of the air blower are elastically deformed by applying a force equivalent to the dynamic load during the operation of the air blower is grasped and can be used as adjustment data.

[0062] When actually fixing the electric motor 70 to the cooling tower 50, through the position adjustment of the electric motor 70 using the support device 16, a predetermined motor support state is achieved in which the output shaft 71 of the electric motor is inclined by a predetermined angle corresponding to a known inclination amount on the side opposite to the side where it is inclined during the operation of the air blower. Thus, during the operation of the air blower, the rotation center axis of the driving-side pulley 11 is parallel to the rotation center axis of the driven-side pulley 12, and the position in the center axis direction of the driving-side pulley 11 matches the position in the center axis direction of the driven-side pulley 12, and the electric motor 70 can be fixed in such a way that the direction of the belt stretched between these two pulleys is perpendicular to the center axis direction of each pulley.

[0063] In this way, during the operation of the air blower that makes the belt 13 travel, the parallelism of the respective center axes of the driving-side pulley 11, the driven-side pulley 12, and the tension pulley 14d can be ensured. Thus, no excessive force that causes the belt 13 to shift in the width direction is applied to the traveling belt 13, and the function of the tension pulley 14d of the tension adjustment unit 14 to prevent the belt from bending and traveling can be appropriately exerted.

[0064] In addition, by using the adjustment data in which the amount of shaft inclination has been previously grasped, the air blower is test-run for each installation site of the cooling tower, and the position offset between the respective pulleys caused by the deformation of the respective parts of the operating air blower is grasped. Based on this, the trouble of the operation of finely adjusting the position of the electric motor to make the positional relationship of the respective pulleys into an appropriate state can be saved.

[0065] The cover 17 is formed in a substantially box shape and is disposed above the air blower 60 to cover the driving-side pulley 11, the driven-side pulley 12, the belt 13, the tension adjustment unit 14, and the belt guide unit 15. Through this cover 17, water from the outside such as rainwater and water droplets contained in the air that reaches the air blower 60 from the inside of the cooling tower through induced ventilation are prevented from reaching the respective parts of the transmission mechanism and causing adverse effects.

[0066] Around the tension adjustment part 14 and the belt guide part 15 of the cover 17, there are provided openings for passing the tension adjustment part 14 and the belt guide part 15 on the gantry part 62 through the inside of the cover under the cover, but at the periphery of the opening, the gap between the cover 17 and the gantry part 62 is blocked by an elastic material or the like, so that there is no opening for communicating the inside and outside of the cover. By eliminating the openings around the tension adjustment part 14 and the belt guide part 15, the water and the humid air inside the cooling tower do not come into contact with the tension adjustment part 14 and the belt guide part 15, thereby preventing the deterioration of the tension adjustment part 14 and the belt guide part 15.

[0067] On the other hand, there are openings for water to flow out of the cover inside at least one or both of the parts around the motor output shaft under the driving side pulley 11 of the cover 17 and the parts around the impeller rotation shaft under the driven side pulley 12. These parts in the cover 17 are provided with through holes of at least a size for passing the motor output shaft and the impeller rotation shaft through in order to connect the motor output shaft and the impeller rotation shaft to the driving side pulley 11 and the driven side pulley 12 accommodated in the cover respectively. The openings can be generated as part of such through holes, that is, the gap parts remaining after the shafts and other components that do not communicate with the through holes are blocked. However, it is not limited thereto, and through holes serving as openings can also be additionally provided in the parts around the motor output shaft and the impeller rotation shaft of the cover 17.

[0068] Through the openings of the cover 17 like this, the external air enters and exits the inside of the cover 17, thereby preventing the generation of condensation caused by the temperature difference between the inside and outside of the cover, ensuring that the water generated by condensation does not accumulate inside the cover, and preventing the main parts of the blower 60 and the motor 70 from coming into contact with water in addition to the tension adjustment part 14 and the belt guide part 15.

[0069] In addition, the openings in the parts around the motor output shaft and the impeller rotation shaft of the cover 17 face downward and deviate from the flow path of the air blown by the blower 60, so water does not enter the cover from the openings.

[0070] Next, the working state of the belt drive mechanism for the cooling tower blower based on the above structure will be described.

[0071] Similar to a well-known cooling tower, in the normal operating state of the cooling tower, the following process is repeated: The heat medium of the cooling object such as the circulating water heated by absorbing heat by the refrigerator or air conditioner is sucked out from a specified circulation path and flows inside the heat exchange part of the cooling tower 50, and returns to the circulation path again after heat exchange. And, the external air is introduced into the heat exchange part by the induced ventilation of the blower 60, and the heat medium exchanges heat with the air in the heat exchange part and is cooled. On the other hand, the air after heat exchange is discharged from the heat exchange part to the upper part of the cooling tower 50 via the blower 60.

[0072] In this operating state, the motor 70 operates under specified control such as on / off corresponding to the conditions of the load (such as the circulating water temperature, the amount of circulating water, etc.). The output shaft 71 of the motor 70 and the driving pulley 11 integrated therewith rotate in a preset rotational direction. Along with the rotation of the driving pulley 11, the belt 13 wound around the driving pulley 11 travels in the positive direction, transmits the driving force, and causes the driven pulley 12 to rotate in the same rotational direction as the driving pulley 11, entering the forward rotation state.

[0073] Before the traveling belt 13 reaches the driven pulley 12 from the driving pulley 11 side, it contacts the tension pulley 14d of the tension adjusting unit 14 and is pressed by the tension pulley 14d tilted by the spring 14c. The belt 13 extends toward the inner peripheral side, achieving an appropriate tension state.

[0074] In addition, in the state of contacting the traveling belt 13, the tension pulley 14d exhibits a known function of preventing the bending travel or the deviation in the belt width direction of the belt 13. By controlling the movement of the belt 13 in its width direction, the bending travel or the deviation can be suppressed.

[0075] In this way, under the control of the tension pulley 14d in the state where the belt 13 travels in the positive direction, the belt 13 travels at approximately the central part of the outer peripheral surface of the driven pulley 12 and moves away from the lower limit position of the feasible travel range. Then, when the belt 13 travels from the driven pulley 12 toward the driving pulley 11 in the belt tension side section during forward travel, it passes through the position where the guide roller 15a of the belt guide portion 15 exists near the driven pulley 12. Even when the belt 13 leaves the driven pulley 12, it maintains the height position when contacting the driven pulley 12. Thus, the guide roller 15a of the belt guide portion 15 whose uppermost position of the guide surface coincides with the lower limit position of the feasible travel range does not contact the belt 13, and no wear occurs between the guide roller 15 and the belt 13 (see Figure 4 ).

[0076] In this way, the driven pulley 12 that rotates by the driving force obtained from the belt 13 in the forward travel state continues to rotate, causing the integrated impeller 61 to rotate in the same way and enter the forward rotation state. The rotation of these driven pulley 12 and impeller 61 is decelerated at a reduction ratio calculated based on the outer diameter of the driving pulley 11 and the outer diameter of the driven pulley 12 with respect to the rotation of the motor output shaft 71. By the driven pulley 12 and the impeller 61 integrated therewith entering the forward rotation state and rotating, the air supply is performed, and induced ventilation to the cooling tower is carried out based on this air supply.

[0077] In the belt transmission mechanism 10, the driving side pulley 11 and the belt 13, as well as the belt 13 and the driven side pulley 12 are always in contact, and the driving force is transmitted by the friction between them, so that less noise is generated during the operation of the blower, and the belt 13 is a flat belt with excellent bending properties, which can further reduce noise compared to the case of using a V-belt or the like for transmission. In addition, as an advantage of the flat belt, it is thin and has little influence of deformation caused by bending, and has excellent durability, and suppresses bending resistance, improves transmission efficiency, and reduces energy consumption involved in driving the blower.

[0078] Furthermore, in a cooling tower, the air supply of the blower is temporarily stopped depending on the load and the surrounding environment. That is, the electric motor is stopped without operating the blower. However, when the electric motor is stopped in this way, the impeller is sometimes rotated in the opposite direction to that of a normal blower driven by an electric motor due to wind pressure applied to the impeller from outside the cooling tower to inside due to strong winds or exhaust gas from adjacent cooling towers.

[0079] In such a case, the belt 13 wound around the driven side pulley 12 rotating integrally with the impeller 61 also travels in the opposite direction to the normal operation of the impeller 61, and the bending travel suppression control of the tension pulley 14d with respect to the belt 13 cannot be correctly performed. However, by arranging the tension pulley 14d of the tension adjustment unit 14 at a position close to the driven side pulley 12, even if the traveling direction of the belt 13 becomes the opposite direction, the relationship between the belt 13 and the tension pulley 14d is almost unchanged, and the degree of progress of the deviation of the belt 13 with respect to each pulley on the driving side and the driven side can be reduced. Therefore, if the reverse state ends in a short time, the action of the motor for air supply is restored, and the belt is restored to the state of moving in the positive direction, the offset of the belt 13 relative to each pulley is restored to a normal level. As a result, the impeller 61 can be easily returned to the forward rotation state and the induced ventilation of the blower 60 can be started again, and the tensioning pulley 14d can be re-controlled to suppress the bending of the belt 13, so that the position of the belt 13 in each pulley returns to the target position.

[0080] On the other hand, when the reverse state of the impeller 61 continues for a long time, the offset of the belt 13 traveling in the reverse direction becomes larger, and the belt side end reaches the lower limit of the travelable range of the outer peripheral surface of each pulley. In contrast, the guide roller 15a of the belt guide portion 15 located near the driven side pulley 12 and in the state where the belt 13 travels in the reverse direction rolls in contact with the belt side end (ear) and guides it toward the driven side pulley 12, keeping the belt side end of the driven side pulley 12 at the uppermost position of the guide surface of the guide roller 15a, that is, at the lower limit of the travelable range of the outer peripheral surface of the pulley, and preventing the belt side end from contacting the pulley flange and lifting up (refer to Figure 5 ).

[0081] Through such guidance with the guide portion 15, it is possible to maintain the belt position of each of the driving and driven pulleys within the travelable range of the outer peripheral surface of each pulley, and the position of the belt in contact with each pulley can be maintained within the travelable range of the outer peripheral surface of each pulley. By appropriately restricting excessive descent, it is possible to prevent wear or damage to the side end portion of the belt and prevent deterioration of the belt.

[0082] In this case, if the operation of the motor 70 for air supply is restored, the reverse rotation state of the impeller 61 is ended, and the driving belt 13 is restored to the state of traveling in the positive direction, there is no problem with the contact between each pulley 11, 12 and the belt 13. Therefore, the driving force can be appropriately transmitted through the belt 13, the impeller 61 is brought into the forward rotation state, and the induced ventilation of the air blower 60 is restarted. Moreover, the bending travel suppression control of the tension pulley 14d is re-executed to return the position of the belt 13 in each of the pulleys 11, 12 to the target position.

[0083] Thus, in the belt drive mechanism for a cooling tower air blower according to the present embodiment, with respect to the belt 13 that transmits the rotational driving force from the driving pulley 11 integrated with the motor output shaft 71 to the driven pulley 12 integrated with the impeller 61, the tension pulley 14d of the tension adjustment portion 14 prevents the belt 13 from deflecting, and suppresses the bending travel of the traveling belt 13. The belt guide portion 15 is located near the driven pulley 12, and the uppermost position of this guide surface is aligned with the lower limit position of the belt travelable range of the outer peripheral surface of the driven pulley. Even in a situation where the bending travel suppression control of the tension adjustment portion 14 is ineffective for a long time in the reverse rotation state of the impeller due to external influences or the like when the operation of the air blower stops, it is possible to appropriately restrict the excessive descent of the position of the belt 13 in contact with each of the driving and driven pulleys 11, 12 through the belt guide portion 15, and the position of the belt 13 can be maintained within the travelable range of the outer peripheral surface of each pulley. It is possible to prevent wear and damage to the side end portion of the belt caused by contact and lifting of the belt with the pulley flange portion. Even in the operating state of the cooling tower where it is assumed that the impeller 61 of the air blower reverses frequently, the belt will not deteriorate, and it is possible to reliably reduce the burden involved in maintenance, such as reducing the replacement frequency of the belt.

[0084] Furthermore, in the belt drive mechanism for a cooling tower air blower according to the above-described embodiment, the cooling tower to which the belt drive mechanism is applied has a direct AC type structure, but is not limited thereto. As long as a blower is disposed above the cooling tower, it can also be applied to other types of cooling towers such as a convection type.

[0085] Further, in the belt drive mechanism for a cooling tower blower according to the above-described embodiment, the tension adjustment unit 14 tilts the arm portion 14b relative to the fixed base portion 14a, and presses the tension pulley 14d mounted on the arm portion 14b against the belt 13. However, it is not limited thereto, and for example, it may be configured such that the tension pulley linearly moves to press the belt in a certain direction, applies tension to the belt, etc., and causes the tension pulley to contact the belt by an action other than tilting.

[0086] Further, in the belt drive mechanism for a cooling tower blower according to the above-described embodiment, a structure is adopted in which a mounting portion 62 is mounted on the support frame 63 of the blower 60, and the tension adjustment unit 14 and the belt guide unit 15 are mounted and fixed on the mounting portion 62. However, it is not limited thereto. For example, in the case where the cover is a split structure composed of an upper cover that covers the drive-side pulley, the driven-side pulley, the belt, the tension adjustment unit, and the belt guide unit from above and a lower cover that covers from below, a structure in which the tension adjustment unit or the belt guide unit is mounted and fixed on the lower cover may also be adopted. In this case, when the cover 17 is provided, if a gap serving as an opening portion is generated between the cover and other adjacent components around the tension adjustment unit or the belt guide unit, a state in which there is no opening during the insertion or filling of an elastic member or the like is achieved.

[0087] Further, in the belt drive mechanism for a cooling tower blower according to the above-described embodiment, the belt guide unit 15 that restricts the downward movement of the belt 13 is provided with a rotatable guide roller 15a. The uppermost position of the cylindrical guide surface that is the outer peripheral surface portion of the guide roller 15a coincides with the lower limit position of the belt travelable range on the outer peripheral surface of the driven-side pulley 12. In a state where the impeller 61 rotates in the reverse direction, the guide roller 15a is brought into rolling contact with the belt-side end portion (ear portion) that reaches the lower limit position of the travelable range on the outer peripheral surface of each pulley. However, it is not limited thereto, and as long as the structure is such that the uppermost position of the guide surface coincides with the lower limit position, the following structure may also be adopted: the guide surface is set as a flat surface and / or a curved surface, the guide surface is set in a stationary state, and the belt 13 is guided by sliding contact with the belt-side end portion that reaches the lower limit position, and the position of the belt-side end portion is maintained at the lower limit position.

[0088] Further, in the belt drive mechanism for a cooling tower blower according to the above-described embodiment, the uppermost position of the guide surface that is the outer peripheral surface portion of the guide roller 15a in the belt guide unit 15 coincides with the lower limit position of the belt travelable range on the outer peripheral surface of the driven-side pulley 12. However, in addition to this, as shown in Figure 6 and Figure 7 , the guide roller 15a may be arranged such that the uppermost position of the portion of the guide surface that can contact the belt end portion is independent of the outer diameter change of the outer peripheral guide surface and coincides with the lower limit position of the belt travelable range on the outer peripheral surface of the driven-side pulley 12.

[0089] In this case, the vertical position of the guide roller 15a is adjusted such that the position of the uppermost part of the central portion of the guide surface of the outer periphery of the guide roller 15a of the belt guide portion 15, which can contact the belt 13, is the same as the height of the lower limit position of the belt travelable range on the outer peripheral surface of the driven pulley 12. Thus, for the belt 13 that descends to the lower limit position when the belt 13 travels in the reverse direction in the reverse rotation state of the impeller 61, even when the outer diameter of the guide surface of the guide roller 15a is reduced due to wear caused by contact with the previous belt 13, it can contact the belt 13 with appropriate position adjustment and continue to guide it, can appropriately guide the belt 13 using the belt guide portion 15 to suppress its descent, can maintain the state where the belt 13 does not deteriorate for a long time, and can reduce the replacement frequency of the belt 13.

[0090] In addition, since the vertical position of the guide roller 15a can be adjusted, assuming that the guide roller 15a is made of a material that is more easily worn than the belt 13, even if the wear of the guide roller 15a progresses due to contact with the belt 13 traveling in the opposite direction, it can be normally guided. Thus, when the guide roller 15a is made of a material that is easily worn, the wear of the belt 13 can be significantly reduced, and thus deterioration caused by wear of the belt 13 can be prevented.

[0091] In the Figure 6 and Figure 7 shown specific example, if the central portion of the guide roller 15a in contact with the belt 13 is worn and its outer diameter is reduced, the detection roller 15d pressed against the central portion by the biasing force of the spring 15g and the roller support piece 15e rotatably supporting the detection roller 15d are laterally displaced, and the position of the central axis 15c of the guide roller 15a engaged with the groove 15f of the roller support piece 15e is displaced upward. Thus, the guide roller 15a moves upward relative to the roller support portion 15b on the mounting portion 62 corresponding to the wear amount, and it is a structure in which the central portion of the guide roller 15a contacts the belt 13 and can maintain the state of guiding the belt 13 from below.

[0092] In addition, in the state where the belt 13 travels in the positive direction, the belt 13 travels in the substantially central portion of the outer peripheral surface of the driven pulley 12 and is in a state of being away from the lower limit position of the travelable range. Therefore, regardless of the presence or absence of position adjustment, the guide roller 15a of the belt guide portion 15 does not contact the belt 13, and the guide roller 15 does not wear, as in the above-described embodiment.

[0093]

Reference Signs

[0094] 10 Belt drive mechanism

[0095] 11 Driving pulley

[0096] 12 Driven pulley

[0097] 13 Belt

[0098] 14 Tension Adjusting Section

[0099] 14a Base Section

[0100] 14b Arm Section

[0101] 14c Spring

[0102] 14d Tension Pulley

[0103] 15 Belt Guide Section

[0104] 15a Guide Roller

[0105] 15b Roller Support Section

[0106] 15c Central Axis

[0107] 15d Detection Roller

[0108] 15e Roller Support Plate

[0109] 15f Groove

[0110] 15g Spring

[0111] 16 Support Device

[0112] 16a Base

[0113] 16b Adjustment Frame Section

[0114] 17 Cover

[0115] 50 Cooling Tower

[0116] 60 Blower

[0117] 61 Impeller

[0118] 61a Rotating Shaft

[0119] 62 Stand Section

[0120] 63 Support Frame

[0121] 70 Motor

[0122] 71 Output Shaft

Claims

1. A belt drive mechanism for a cooling tower blower is a belt drive mechanism that transmits the rotational driving force from a motor to the impeller of the blower in a cooling tower where heat exchange is performed between the air drawn in from the outside by induced ventilation of the blower and the hot medium of the object to be cooled. It is characterized in that it includes: a driving-side pulley integrally arranged with the output shaft of the motor; a driven-side pulley integrally arranged with the rotating shaft in the impeller of the blower; a belt, which is an annular flat belt stretched between the driving-side pulley and the driven-side pulley; a tension adjustment part, which, in the forward rotation state of each pulley when the blower performs induced ventilation, contacts the outer peripheral surface of the belt at a specified part in the section of the belt that becomes the slack side when traveling in the specified forward direction, prevents the belt from flexing, and controls the movement of the belt to suppress bending travel; and a belt guiding part, which restricts the downward movement of the belt near the driven-side pulley, the tension adjustment part has a tension pulley that is pressed against the outer peripheral surface of the specified part of the belt and can rotate, and is arranged so that the tension pulley is located in a specified area close to the driven-side pulley, the belt guiding part has a guiding surface, and this guiding surface is arranged below the specified part in the section of the belt that becomes the tension side when traveling in the positive direction, this guiding surface is arranged such that at a specified position closer to the driven-side pulley than the tension pulley of the tension adjustment part, the uppermost position of the guiding surface is made to coincide with the lower limit position of the belt traveling possible range on the outer peripheral surface of the driven-side pulley.

2. The belt drive mechanism for a cooling tower blower according to claim 1, characterized in that for the belt traveling in the positive direction in the forward rotation state of the blower, the tension adjustment part, through the control of suppressing the bending travel of the belt, makes the belt travel at approximately the central part in the vertical direction on the outer peripheral surface of the driven pulley, and makes the lower end part of the belt leave from the lower limit position of the belt traveling possible range, the belt guiding part is configured such that the uppermost position of the guiding surface is restricted to a configuration state where it does not reach above the lower limit position of the belt traveling possible range of the driven-side pulley, and the guiding surface is separated from the belt traveling in the positive direction.

3. The belt drive mechanism for a cooling tower blower according to claim 1 or 2, characterized in that the belt guiding part has a guiding roller rotatably supported, and the cylindrical surface part on the outer periphery of the guiding roller is set as the guiding surface, the guiding roller sets the roller rotation axis direction to be perpendicular to the rotation axis direction of the driven-side pulley, and arranges the tangential direction of the uppermost position of the guiding surface to be parallel to the belt traveling direction at the specified position.

4. The belt drive mechanism for a cooling tower blower according to claim 3, characterized in that the guiding roller is arranged to be capable of vertical position adjustment so that, regardless of the change in the outer diameter of the guiding surface, the uppermost position of the part of the guiding surface that can contact the belt end coincides with the lower limit position of the belt traveling possible range on the outer peripheral surface of the driven-side pulley.

5. The belt drive mechanism for a cooling tower blower according to any one of claims 1-4, characterized in that It has a pedestal part which is installed on the support frame that supports the blower on the cooling tower and is located between the output shaft of the motor and the rotating shaft of the blower impeller. The tension adjustment part is installed at a first specified position of the pedestal part and is arranged between the driving pulley and the driven pulley. The belt guiding part is installed at a second specified position of the pedestal part and is arranged near the driven pulley.

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