JP3458426B2 - Centrifugal multi-blade fan - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower, and more particularly to a centrifugal blower in which a modal value of a resonance section is changed to shift a resonance frequency. 2. Description of the Related Art As a conventional blower, Japanese Utility Model Laid-Open No.
As shown in Japanese Patent No. 64499, a sirocco fan type multi-blade fan is known. These are formed on the outer peripheral portion of the support formed around the boss portion on the one side and the other side in the fan axial direction, respectively, at the root of the wing piece on one side and at the root of the wing piece on the other side. Are arranged alternately in a staggered manner. [0003] The joint portion between the drive shaft of such a fan and a rotating body fixed to the drive shaft is, for example, shown in FIG.
As shown in FIG. 3, the end surface of the drive shaft 1 has a D shape, and the rotating body boss 2 on the driven side is fitted and fixed integrally with the outer peripheral portion of the D shape drive shaft 1. . A structure in which such a conventional drive shaft and a driven-side rotating body boss fixed to the drive shaft are integrally connected by a D-shaped fitting or the like, Most of the fluctuations in the rotational torque of the drive shaft are transmitted to the driven rotator boss, so that the occurrence of resonance due to the oscillating excitation force and the driven natural frequency becomes a problem. As a method of solving this resonance problem, for example, a method of changing a modal mass m, a spring constant k, and a viscous damping coefficient c of a resonance part of a vibration system as shown in FIG.
In order to make it difficult to transmit the exciting force, there is a method of inserting a separate component such as rubber between the driving portion and the driven portion to attenuate the exciting force. However, in general, according to the above-described method of changing the modal value, a drastic change in the shape of the driven side is required, and the cost is likely to increase, and according to the method of inserting the separate component, the use of the separate component is required. There are problems such as an increase in cost. The present invention has been made in order to solve such a problem. By slightly changing the shape of a part of the fan, the resonance frequency is mainly changed by changing the spring constant k of the modal value of the resonance section. It is an object of the present invention to provide a centrifugal multi-blade fan that reduces vibration noise while preventing excessive increase in flow resistance. A centrifugal multi-blade blower according to a first aspect of the present invention for solving the above-mentioned problems is provided with a boss cylindrical portion which receives a driving force, and is arranged in a circumferential direction. A plurality of blades, a boss plate connecting the boss cylinder and the plurality of blades, and a centrifugal blower fan having an annular shroud connecting an upper portion of the plurality of blades, wherein the boss plate is arranged in a fan axial direction. An inner peripheral end is connected to the boss portion, an outer peripheral end is connected to a lower portion of the plurality of blades, and a plate thickness near an outer peripheral portion of the boss plate so as to change the air flow to a fan radial direction. The above
It is characterized in that the boss plate is made thicker than other common parts . According to the structure of the present invention, the thickness of the boss plate near the outer peripheral portion is made larger than the thickness of other general portions of the boss plate, so that the internal friction of rubber or the like is increased. The resonance frequency can be shifted without using a separate member having a large size and without causing the resonance frequency to jump by inverter control or the like. Hereinafter, a reference example and an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a first reference example in which the present invention is applied to a centrifugal blower that takes in air from a vehicle air conditioner. As shown in FIG. 1, a centrifugal blower 10 includes a drive motor 12, a centrifugal multi-blade fan 14, and a fan case 1
6 The fan case 16 is formed by molding a resin into a known scroll shape, and has an air outlet portion extending in a radially outward direction in a part (not shown). A drive motor 12 that rotationally drives the centrifugal multi-blade fan 14 is supported and fixed to the center bottom of the fan case 16. The drive motor 12 has a motor body 20 fixed inside a resin-made cylindrical motor case 18. Motor case 1
A flange portion 22 extending in the centrifugal direction is formed on the outer peripheral portion of the fan case 16.
a. Drive shaft 24 of motor body 20
, A centrifugal multi-blade fan 14 is fixedly connected thereto. The centrifugal multi-blade fan 14 includes a boss portion 26, a blade 28, and a shroud 30, which are integrally formed of a resin such as polypropylene. The boss portion 26 is connected to the drive shaft 24 by a cylindrical support portion 32 formed at the center thereof, and the driving force of the motor body 20 is transmitted via the drive shaft 24. The boss plate 29 of the boss portion 26 is formed in a curved shape that is convex as viewed from the air suction side and smoothly curves radially outward from the central portion.
The boss plate outer peripheral end 29a is connected to the blade 28. The blade 28 is provided at the outer edge 2 of the boss plate.
It extends vertically upward from 9a. A large number of the blades 28 are annularly arranged in the vicinity of the outer peripheral end of the boss plate 29 at a predetermined arc interval in the circumferential direction. Shroud 30
Are joined to the air suction side end of the blade 28, and are formed in a substantially arc-shaped cross-sectional shape so as to change the air flow taken in from the air intake 36 from the fan axial direction to the fan radial outside direction. An annular projection 30b projecting upward is formed on the inner peripheral end 30a of the shroud 30. The fan case 16 has a bell mouth 40 forming an air inlet 36. The bell mouth 40 is formed in a semicircular arc shape so as to surround the projection 30b of the shroud 30. The bell mouth inner wall 40a and the projection 30
A small interval is set between b. Boss plate 29
Annular projection 5 formed near the outer peripheral end 29a on the lower surface side of the
0 has a role of mainly improving the bending rigidity of the boss plate 29 in the circumferential direction. The provision of the annular projection 50 has a function of minimizing the maximum displacement of the fan. This makes it possible to remove the resonance range from the main frequency range of the oscillation system. The motor body 2 is provided on the lower surface side of the boss plate 29.
Although the air for cooling 0 flows in the centrifugal direction, the annular projection 50 is desirably formed at such a height that the air resistance of this flow is not extremely increased. Next, the relationship between the peak of the twelfth-order component of the magnetic vibration serving as the excitation source and the fan rotation speed is shown by the following equation. That is, 12th order component of rotation = rotational speed (rpm) × 12/60 (sec) (Hz) FIG. 4 is a tracking data diagram showing the relationship between the oscillation frequency on the horizontal axis and the rotational speed on the vertical axis, showing the relationship between the peak levels. . It can be seen from FIG. 4 that the peak level is increased in the twelfth-order component, and it is considered that resonance has occurred in the low-frequency abnormal sound generation unit. FIG. 7 shows the frequency on the horizontal axis and the sound pressure level on the vertical axis for the twelfth-order component. FIG. 5 shows the rotational speed on the horizontal axis and the sound pressure level on the vertical axis for the twelfth-order component. Things. FIG. 6 is a graph in which a large inclination (trend) is removed from FIG. 5 and the amount of peak value protrusion from the trend line is rewritten on the vertical axis. As shown in FIG.
In the reference example, resonance mainly occurs at 200 to 400 Hz. However, in this reference example, it has been found that effective noise reduction can be achieved particularly for mode A that occurs near 350 Hz. Book
Due to the shape of the boss plate 29 of the reference example, as shown in FIG. 3, when the annular projection 50 is present (this reference example) as compared to the case where there is no annular projection in the frequency range of 300 to 400 Hz (comparative example), It has been found that the pressure level can be reduced considerably. For example, if the frequency range that poses a practical problem is 20
Assuming that the resonance frequency exists in this range, f: natural frequency, k: rigidity (spring constant),
m: mass, and assuming that there is a relationship of f∝√k / m,
The value of k / m may be changed so as to be out of the resonance frequency range. Here, the provision of the above-mentioned annular projection is such that the change in the increase in the mass m can be almost neglected. Therefore, by changing the rigidity k by changing the shape of the boss plate, it can be removed from the resonance region. As a result of conducting an experiment using a vibration analysis FEM,
The resonance mode of the fan alone was determined. In the experiment, as shown in FIG. 8, the motor 12 is vibrated by the impulse hammer, the vibration frequency is detected by the pickup 61, and the resonance frequency of the motor alone is determined from the transfer function shown in FIG. did. For the resonance modes of the motor and the fan, a modal analysis was performed, and the modes and frequencies were identified from computer analysis. In the modal analysis using impulse response, the transfer functions of the fan itself, the fan and the motor were measured to confirm the accuracy of the numerical calculation, and the modal analysis was performed on the fan and the motor, and the vibration pattern was experimentally grasped. As an experimental analysis procedure, a transfer function was measured from a vibration experiment on a test fan, and a modal parameter of the structure was obtained by using a curve fitting method. [0019] In the reference example, as described above, for increasing the rigidity of the boss plate 29 has formed the annular projection 50 in the vicinity of the outer peripheral edge 29a of the lower surface side of the boss plate 29, as a rigid improving an alternative to this Fig. 10, Fig. 1
The second, third reference examples and the first actual shown in 1 and 12
Examples are given. The second reference example shown in FIG. 10 is an example in which the outer peripheral end of the boss plate 29 is bent downward at the bent portion 29b, and the lower end 29c faces downward. The lower end 29c is formed in an annular shape in the circumferential direction of the boss plate 29. The third reference example shown in FIG. 11 is an example in which a plurality of, in this case, two annular projections 29d and 29e are formed concentrically in the vicinity of the outer peripheral end of the boss plate 29. Shown in FIG.
The first embodiment is an example in which the boss plate near the outer peripheral end of the boss plate 29 is formed with a thick portion 29f thicker than the center portion. The rigidity of the boss plate 29 is increased by forming the thick portion 29f. In each of the above reference examples and embodiments, in order to increase the rigidity of the boss plate, an annular projection or a thick portion as a circumferential reinforcing rib is provided near the outer peripheral end of the boss plate as described above. The rigidity is improved as understood from its cross-sectional shape. In the present invention, such a shape changing means for improving the rigidity includes:
Other shapes may be used and are not particularly limited.
However, it is preferable that the resistance of the air flow on the lower surface side of the boss plate 29 is not significantly increased by such a shape change of the outer peripheral end of the boss plate for improving the rigidity. Further, since the value of the spring constant k is greatly increased by a slight shape deformation as in the case of the annular projection as described above, the modal value can be changed by changing the shape of the boss plate. Therefore, while preventing the flow rate resistance from excessively increasing on the lower surface side of the boss plate, there is an effect that the resonance frequency range due to the modal value change is removed by a slight shape change of the boss plate and vibration noise can be reduced. As described above, according to the centrifugal multi-blade fan of the present invention, by changing the shape of a part of the fan slightly, mainly the spring constant k of the modal value of the resonance part is changed. This has the effect of reducing the vibration noise while shifting the resonance frequency and preventing an excessive increase in the flow resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view showing a centrifugal blower according to a first reference example of the present invention. FIG. 2 is a bottom view of the centrifugal fan. FIG. 3 is a diagram comparing the relationship between frequency and sound pressure in a first reference example of the present invention and a comparative example having no annular protrusion provided in the first reference example. FIG. 4 is a data diagram showing a relationship between frequency and rotation speed. FIG. 5 is a data diagram showing a relationship between a rotational speed and a sound pressure. FIG. 6 is a data diagram showing a relationship between a frequency and a sound pressure peak level. FIG. 7 is a data diagram showing a relationship between a frequency and a sound pressure level. FIG. 8 is an explanatory diagram of a method for obtaining a resonance frequency of a single motor by an impulse response analysis. FIG. 9 is a data diagram showing the relationship between the frequency of a single motor and the vibration transmissibility. FIG. 10 is a sectional view showing a main part of a second reference example of the present invention. FIG. 11 is a sectional view showing a main part of a third reference example of the present invention. FIG. 12 is a sectional view showing a main part of the first embodiment of the present invention. FIG. 13 is an end view showing a joint portion between a drive shaft and a boss in a conventional example. FIG. 14 is a schematic diagram showing a general vibration system. [Description of Signs] 10 Case 12 Motor 14 Centrifugal multi-blade fan 24 Drive shaft 26 Boss 28 Blade 29 Boss plate 29a Boss plate outer peripheral end 30 Shroud 32 Cylindrical support (boss cylinder) 50 Annular protrusion (annular rib)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Kondo 1-1-1, Showa-cho, Kariya-shi, Aichi, Japan Inside Denso Corporation (72) Inventor Akiaki Watanabe 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Denso Corporation (72) Inventor Sugi Hikari 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References Japanese Utility Model Sho 55-92100 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F04D 29/28 F04D 17/08

Claims (1)

(57) [Claim 1] A boss tube portion receiving a driving force, a plurality of blades arranged in a circumferential direction, a boss plate connecting the boss tube portion and the plurality of blades, and A centrifugal blower fan having an annular shroud for connecting upper portions of the plurality of blades, wherein the boss plate has an inner peripheral end formed with the boss so as to change an air flow from a fan axial direction to a fan radial direction. The outer peripheral end is connected to a lower portion of the plurality of blades, and a plate thickness in the vicinity of an outer peripheral portion of the boss plate is larger than a plate thickness of another general portion of the boss plate. Centrifugal multi-blade fan.