JPS58190599A - Centrifugal fan - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a type of centrifugal fan with an impeller consisting of a rear plate and a series of blades fixed to the periphery of the rear plate. The inner edges of the vanes are spaced equidistantly from the axis of rotation of the impeller and define a central inlet region, called the eye of the impeller, into which gas, such as air, is drawn as the impeller rotates. , so that it is emitted outward from between the blades towards the rear of the cow. In such centrifugal fans, the impeller typically has an inlet opening that communicates with the eye of the impeller and a space around the impeller;
It is housed in a volute-shaped casing with an outlet opening that allows gas to escape during operation of the fan.

The flow rate of a centrifugal fan can be changed by changing the rotational speed of the impeller, but this is not necessarily the preferred or practical method.

Alternatively, the bumper can be placed on the inlet side or outlet side of the fan, depending on the configuration and desired characteristics of the fan. Such methods tend to reduce the efficiency of the fan to some degree depending on its configuration, but they are simpler structures than most methods used to change the speed of the impeller. It has the advantage of low manufacturing cost.

Commonly used home-made dampers usually consist of a plurality of parallel pivotable blades mounted at the outlet of the fan and are adapted to increase or decrease the resistance to the gas rItK depending on the angle at which the blades are set. ing.

Another type of damper uses radial pivotable blades at the fan inlet. In the use of centrifugal 7a/, the maximum pressure is created only when the gas flows into the limit of impeller 2 without creating a vortex. The radial blade damper is configured to cause some pre-rotation of the gas in the direction of rotation of the inlet 2, so that the pressure created by the fan is reduced, thereby reducing the flow rate. ,
Absorption of power takes place.

Such a damper allows the fan to operate with higher efficiency than the parallel-blade damper described above, but the mechanics required to rotate each blade in synchrony are considerably more complex. become.

It is known that when the configuration of the impeller blades and their rotational speed are constant, the flow rate is a function of 1- of the blades. This can be used to construct other types of dampers, which have advantages over the two previously mentioned types, as will become clear from the following description. .

According to the present invention, the inner edges of the impeller blades are lengthened by a in parallel to the axis of the impeller, and the disc-shaped damper plate is placed inside the blade array with its edges close to the inner edges of the blades. The damper disk is coaxially supported by the damper disk, and the damper disk is movable in the axial direction by the weight of the blade arrangement.

Such a damper effectively changes the effective width of the impeller blades, allowing the fan to operate with efficiency comparable to one with a radial blade type damper;
Moreover, the structure is quite simple as it only requires one movable part of the fish tank, and stable control is possible down to almost zero flow rate, and the increase in flow resistance is almost negligible. It is.

The damper plate can be supported in a non-rotating manner and its axial movement can be effected by pneumatic, hydraulic or electric actuators. The actuator can, for example, be automatically controlled in response to a control signal extracted in a suitable manner depending indirectly on the fan output K; however, as an alternative, if necessary, Alternatively, as an additional means manual control means can be provided.

The fan impeller may be driven by an electric motor or other suitable drive means. A variable speed electric motor can be used in conjunction with the movable damper plate, thereby providing additional control.

The invention is particularly applicable to blower systems that use relatively wide impellers with high speeds, allowing a considerable range of control. With the damper plate of the invention acting on the effective width of the impeller blades, its operation is not influenced by the shape of the blades. Thus, the impeller blades can be of any shape commonly used in centrifugal fans. For example, the vanes may be sloped backwards, curved backwards or forwards, with their inner edges extending parallel to the axis of the impeller as described above. , may be airfoil-shaped.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

The illustrated centrifugal fan has an inlet opening 10 and an outlet opening 20.
It consists of a spiral outer casing 1 and an impeller 2 rotatably supported in the casing. Impeller 2Fi, rear plate 3 carried by a shaft 4 extending through a bearing 5 ft mounted on the rear wall 6 of the casing 1 for connection to a suitable drive wj device (not shown) such as an electric motor
and an array of nine plurality of blades 7 arranged and attached to the front surface of the rear plate 3 at equal intervals in the circumferential direction. The radially inner edges of these impeller blades 7 are parallel to the axis of the impeller and are each equidistantly spaced therefrom. An annular shroud plate a1 is attached to the front edge of each blade 7. The inner edge of the shroud plate 8 is curved forward and has a stationary entry. It is designed to surround the adjacent end of the . Penturi 9#'i, casing 1 in conventional manner
It communicates with an inlet opening 10 provided in the front wall of.

According to the invention, a damper consisting of a circular plate 11 is provided coaxially inside the array of impeller blades 7. circular plate 11
The diameter is such that its inner edge approaches the inner edge of the vane 7 with a slight clearance. The plate 11 is connected to an axial rod 13 projecting outwardly through the input rod 9 and supported on the casing 1 by a radial stay rod 14.
3, it is configured to be able to move in the axial direction.

Moving the actuating rod 12 from the impeller blades 7
The position of the damper plate 11 relative to the other is changed. As a result, by varying the effective width of the impeller blades, flow can be effectively controlled with little loss of fan efficiency and with a minimum of moving parts.

The flow rate varies from practically zero snow flow when the damper plate 11 is placed in a retracted position in close proximity to the inlet love plate 9 to a maximum flow rate value when the damper plate is placed in a position in close contact with the rear plate 3. It can be changed up to.

The actuator 15 can be actuated pneumatically, hydraulically or electrically, depending on the configuration of the fan, or by any other means such as manual or servo control.

For example, a temperature sensor 15 is placed at a position where the temperature changes according to fluctuations in the fan output (exhaust gas flow rate), and the actuator 1
3 can be actuated to control the position of the damper plate 11 so as to maintain the temperature substantially constant. Alternatively, temperature sensor 15 may be replaced by another type of sensor that responds to other conditions, such as humidity, which varies in response to variations in fan output. temperature,
Means may be provided for adjusting the output signal to alter other conditions obtained by adjusting the fan output.

Although the impeller blades 7 are shown as being planar (FIG. 2) and tilted rearward in the direction of rotation, they may be any of the types commonly used in centrifugal fans to which the present invention is directed. Model % formula %

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a centrifugal fan according to the present invention, and FIG. 2 is a #! FIG. 1 is a sectional view taken along line G in FIG. In the figure, 3 is a rear plate, 4 is a shaft, 7 is an impeller blade, 9 is a venturi, 12 is a rod, 13 is an actuator, and 15 is a sensor. ! Patent applicant agent Ii 1) Nobuyuki 15゛・、
7-8.5 I-

Claims (1)

[Claims] 1) In a type of centrifugal fan in which impeller blades are arranged such that their inner edges extend parallel to the axis of the impeller, a damper plate in the shape of a disc is provided in the blade array. The damper plate is coaxially supported on the inside, and the outer peripheral edge of the damper plate is arranged close to the inner edge of the blade, and the damper plate is movable in the axial direction inside the blade array. centrifugal fan. 2) The centrifugal fan according to claim 1, wherein the damper plate is supported non-rotatably. 3) The centrifugal fan according to claim 1 or 2, further comprising an actuator that is automatically controlled in response to a control signal to move the damper plate in the axial direction. 4) a sensor configured to emit a signal that varies in accordance with a prefecture condition that varies in accordance with changes in the output of the centrifugal fan;
Claim comprising means for applying said signal as a control signal to control said actuator and thereby control the position of said damper plate so as to maintain line conditions substantially constant. The centrifugal fan described in item 3, with a range of 1g. 5) The centrifugal fan of claim 4, wherein the sensor is responsive to temperature fluctuations. 6) The centrifugal fan according to any one of claims 2 to 5, wherein the actuator is electrically actuated. 7) The centrifugal fan according to any one of claims 2 to 5, wherein the actuator is operated by pneumatic pressure or hydraulic pressure. 8) The centrifugal fan according to claim 2, wherein the actuator is controlled in response to a control signal issued manually. 9) The centrifugal fan according to any one of claims 1 to 8, wherein the impeller is driven by a variable speed electric motor.