GB2067665A

GB2067665A - Radial fan

Info

Publication number: GB2067665A
Application number: GB8039795A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1979-12-13
Filing date: 1980-12-12
Publication date: 1981-07-30
Also published as: IT8026491A0; JPS5698596A; DE2950060C2; DE2950060A1; FR2471503B1; FR2471503A1; IT1134618B; GB2067665B; JPH01125892U

Abstract

A radial fan which serves for spatial ventilation, e.g. the ventilation of passenger compartments of motor vehicles comprises a volute casing (14) in which there is provided a housing recess (16) for a drive motor (12), preferably an electric motor. The shaft (20) of the motor (12) extends inside the volute casing and carries an impeller (18). An air supply passage (46) leads from the air gap (40) between the impeller (18) and a planar radial wall (26) of the casing (14) which is disposed opposite an air inlet orifice (22) of the volute casing (14) to a region of the housing recess (16) remote from the volute casing (14). The pressure differential between the air gap and the housing recess causes a flow of cooling air, which flows through the drive motor. <IMAGE>

Description

SPECIFICATION Radial fan The invention relates to a radial fan and in particular to a radial fan comprising a volute casing having a housing recess therein to accommodate a drive motor, preferably an electric motor. A rotary impeller located in the volute casing is operatively connected to a shaft of the motor. Such a fan is already known in which a strea'm of cooling air is collected by means of a scoop, which extends inside the volute casing in the vicinity of the outlet orifice thereof, and is conducted via a flexible hose to the driving motor.

The rate of delivery and the efficiency of the fan are thereby reduced and operating noise is increased.

The radial fan according to the present invention, includes a passage for cooling air, which passage communicates with the volute casing via an orifice in the region of the air gap between the impeller and a planar wall of the casing disposed opposite an air inlet orifice for the casing. This arrangement has the advantage that, purely as a result of the pressure differentiai between the air gap and the housing recess, an air flow to the driving motor is created in the cooling air supply passage to ensure the supply of cooling air to the electric motor. A component extending into the cooling air stream in accordance with the prior art and having the resultant disadvantages described, is unnecessary.

It is particularly advantageous if the cooling air supply passage comprises an enlargement preferably formed on the housing recess, since, in that case, the known flexible hose and associated costs of mounting can be eliminated. Such enlargement is preferably in the form of a channel having a cross-section which taper inwardly (i.e.

because progressively smaller) in a direction away from the casing.

The cooling air supply passage is preferably arranged on the side of the housing remote from an outlet orifice of the volute casing, and is preferably offset, in the direction of rotation of the impeller by at least about 1350 from the narrowest point between the impeller and the curved wall of the volute casing. A transition surface is preferably formed between the surface of the supply passage and the volute casing in the region of the impeller.

The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a plan view of a radial fan according to the present invention, and Figure 2 is a cross-sectional view of the radial fan along the line Il-Il in Figure 1.

Referring now to the drawings a radial fan 10 comprises an electric motor 12, a two-part fan housing 14 (one part of which includes a housing recess 1 6 to accommodate the electric motor 12) and an impeller 18, which is mounted on a shaft 20 of the electric motor 12 which extends inside the fan housing 14. The fan housing 14 has an axial air inlet orifice 22 (Figure 1) and an outlet orifice 24 (Fig. 2) arranged radially with respect to the impeller 1 8. The fan housing 14 has two planar parallel-disposed opposite walls 26, 28.

The housing recess 1 6 for housing the electric motor 12 is formed in the wall 26, and the inlet orifice 22 is formed in the wall 28. The two walls 26 and 28 are connected one to the other by a curved wall 30, which has a spiral configuration relative to the impeller 1 8. The narrowest point 34 in the direction of rotation (indicated by arrow 32) of the impeller 1 8 is situated between the curved wall 30 and the radial path of the impeller, just to the rear of the outlet orifice 24 in the fan housing 14. A fan housing of this type of construction is also designated as a 'voiute casing'.The size of the gap between the surface 36 of the planar wall 26 facing inwardly into the volute casing 14 and the end face 38 of the impeller 18 disposed opposite this surface 36 is selected so as to provide a relatively narrow air gap 40, of between 2 mm and 8 mm according to the size of fan. A cylindrical wall 42 of the housing recess 1 6 is provided with a channel-shaped enlargement 44, which forms a passage, one of whose ends communicates with the fan housing 14 and whose other end communicates with the housing recess 1 6 for the electric motor 12. When the electric motor 12 is mounted in the housing recess 16, the motor housing covers the longitudinal opening of the enlargement 44, so that a passage 46 having two orifices 48 and 50 is created.Thus, the passage 46 communicates with the volute casing 14 in the region of the air gap 40, and the other orifice 50 of the passage 46 is disposed in the region of the end of the housing recess 1 6 remote from the volute casing 14. The cross-section of the passage 46 is inwardly tapered in the manner of a flue between its orifice 48 and its orifice 50.

In the region of the orifice 50 the electric motor 12 is provided with a shoulder, so that the passage 46 communicates with an annular chamber 52. The depth of the channel-shaped enlargement 44 is so selected that, in the region of the radial path of the impeller or even radially externally thereof, a transition surface is formed between the bottom 54 of the passage 46 and the volute casing 14. The width 56 of the passage 46 amounts to between 10% and 1 5% of the impeller diameter 58. The cooling air passage 46 is offset at an angle a of about 1350 in the direction of rotation 32 of the impeller 1 8 relative to the narrowest point 34 between the curved wall 30 and the impeller 1 8 (cf. Fig. 1).

When the radial fan is in operation, the impeller rotates in the direction of the arrow 32. A flow of air is drawn into the volute casing through the axial inlet orifice 22 (arrows 60) and is discharged through the outlet orifice 24 in the form of a useful airstream 62 for a predetermined purpose. When the radial fan is in operation, a pressure above atmospheric pressure is created in the volute casing 14, in particular in the region of the air gap 40, and causes a cooling air stream 64 to flow through the passage 46.Thus, the cooling air 64 flows via the orifice 48 adjacent to the volute casing, through the passage 46, and, at the orifice 50, enters the annular chamber 52 of the housing recess 1 6. On the side remote from the impeller the electric motor 12 is provided with cooling orifices (not shown) through which the cooling air stream enters into the interior of the electric motor 12, flowing through the latter axially of the shaft 20 and re-entering the volute casing in the form of hot air 66 in the region of the impeller 18, where it mixes with the induced air stream 60 and is discharged together with the useful air stream 62.

It is evident, therefore, that, without special auxiliary means, there is provided a supply passage for cooling air for the electric motor 1 2, through which air flows in dependence on the pressure differential between the gap 40 and the annular chamber 52.

Claims

1. A radial fan comprising a volute casing having a housing recess arranged therein for accommodating a drive motor, to whose shaft a rotary impeller, located in the volute casing, is operatively connected, and a supply passage for cooling air for the driving motor, one end of which passage communicates with the volute casing in the region of the air gap formed between the impeller and a planar wall of the volute casing disposed opposite an air inlet orifice for the casing, and the other end of which passage communicates with the housing recess, the orifice of the passage adjacent to the housing recess being arranged in the region of the end of the housing recess remote from the volute casing.

2. A radial fan as claimed in claim 1, in which the cooling air supply passage is formed by an enlargement formed on the housing recess.

3. A radial fan as claimed in claim 2, in which the enlargement is constructed in the form of a channel having a cross-section which becomes progressively smaller in a direction away from the volute casing.

4. A radial fan as claimed in any one of claims 1 to 3, in which the orifices of the cooling air supply passage are arranged on the side of the housing remote from an outlet orifice of the volute casing.

5. A radial fan as claimed in any one of the preceding claims, in which the supply passage is offset, in the direction of rotation of the impeller, at least approximately 1350 from the narrowest point between the impeller and the curved wall of the volute casing, and communicates with the radially outer region of the impeller.

6. A radial fan as claimed in any one of the preceding claims, in which a transition surface is formed between the bottom of the cooling air supply passage and the volute casing in the region of the radial path of the impeller.

7. A radial fan as claimed in any one of the preceding claims, in which the width of the cooling air supply passage is from 10% to 1 5% of the impeller diameter.

8. A radial fan substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.