Patent Description:
In centrifugal blowers, the air drawn into the blower by the rotation of the impeller enters the inlet opening formed in one of the end walls of the housing of the blower with a direction parallel to the axis of rotation of the impeller and is subsequently expelled through the outlet opening formed in the side wall of the housing with a direction perpendicular to the inlet direction.

The use of a sound absorption structure makes it possible to reduce the noise generated by the air inside the housing of the blower. The resonant cavity/cavities and the communication openings thereof with the impeller chamber and air outlet duct are sized to create a Helm-holtz resonance with the air being pushed by the impeller acting as a dynamic damper for sound waves. To increase the sound absorption effect, it may be envisaged for the resonant cavity to be at least partially filled with a porous sound absorption material.

An embodiment of a housing equipped with a sound absorption structure is described at the general concept level in the Applicant's <CIT>.

One object of the present invention is to provide a solution to make the concept described in the <CIT> producible on an industrial scale.

<CIT>and <CIT> are additional documents representing the background art of the present invention.

For this object, the subject matter of the invention is a housing for centrifugal blowers of the type defined above, comprising.

The housing according to the invention may be made from three, or at most four, pieces of plastics material which are assembled together, and have relatively simple shapes and are thus easily made through conventional injection molding techniques. It therefore lends itself to economic implementation on an industrial scale.

Preferred embodiments of the invention are defined in the dependent claims, which are to be understood as an integral part of the present description.

Further features and advantages of the housing according to the invention will become clearer from the following detailed description of an embodiment of the invention, made in reference to the accompanying drawings, provided purely for illustrative and non-limiting purposes, wherein:.

<FIG> shows a housing or volute made of plastics material for a centrifugal blower, denoted as a whole with <NUM>.

The housing <NUM> is configured to accommodate an impeller I of the centrifugal blower, lightly depicted with dashed lines in <FIG>. The housing <NUM> is also configured to be coupled to an electric motor (not shown) to drive the impeller I, which electric motor is arranged outside of the housing <NUM>.

From the point of view of its overall shape/geometry, the housing or volute <NUM> comprises a pair of end walls <NUM> and <NUM>, which hereinafter will be called "base end wall" and "cover end wall", respectively, and a side wall <NUM> extending between the end walls <NUM>, <NUM>. An air inlet opening <NUM> is formed on the cover end wall <NUM>, and a passage opening <NUM> is formed on the base end wall <NUM>, through which opening the shaft (not shown) passes, connecting the electric motor to the impeller I of the blower. An air outlet opening <NUM> is formed on the side wall <NUM> of the housing <NUM>.

The end walls <NUM>, <NUM> and the side wall <NUM> of the housing <NUM> cooperate to define an impeller chamber 3a, within which the impeller I is housed, and an air outlet duct 3b, which connects the impeller chamber 3a to the air outlet opening <NUM> and is configured to convey the air flow pushed in a centrifugal direction from the impeller I to the air outlet opening <NUM>.

A sound absorption structure is arranged on the side wall <NUM>, which will be described hereinafter.

In terms of its construction, the housing <NUM> comprises four pieces of plastics material assembled together. More specifically, the housing <NUM> comprises a base half shell <NUM>, a cover half shell <NUM>, a chamber side panel <NUM>, and an outlet side panel <NUM>.

The base half shell <NUM> is shown separately in <FIG> and <FIG>. The base half shell <NUM> is essentially formed by the base end wall <NUM> and by a first portion <NUM> of the side wall <NUM>, which protrudes from the base end wall <NUM>. The first portion <NUM> of the side wall <NUM>, which will also be referred to as the first wall portion <NUM> hereinafter, extends along part of the perimeter of the base end wall <NUM>. More specifically, the first portion <NUM> extends so as to surround the impeller chamber 3a and delimit on a radially outer side the air outlet duct 3b. In this description, the radial positions are defined with respect to the central axis x of the impeller chamber 3b (shown in <FIG>; the central axis x here defined corresponds to the position of the axis of rotation of the impeller I). Therefore, the radially outer side of the outlet duct 3b is the side of the outlet duct 3b furthest from the axis x.

In particular, the first portion <NUM> of the side wall <NUM> extends between an end area 21a thereof at the air outlet opening <NUM> and a rostrum-shaped end area 21b thereof at the junction of the impeller chamber 3a and the radially inner side of the air outlet duct 3b.

The base half shell <NUM> therefore comprises a peripheral edge <NUM> that partly extends along the entire first portion <NUM> of the side wall <NUM> and partly extends along the radially inner side of a portion 6a of the base end wall <NUM> that delimits the outlet duct 3b.

The cover half shell <NUM> is shown separately in <FIG>, <FIG> and <FIG>. The cover half shell <NUM> is essentially formed by the cover end wall <NUM> and by a second portion <NUM> of the side wall <NUM> that protrudes from the cover end wall <NUM>. The second portion <NUM> of the side wall <NUM>, which will also be referred to as the second wall portion <NUM> hereinafter, extends along part of the perimeter of the cover end wall <NUM>. More specifically, the second portion <NUM> extends so as to delimit on a radially inner side the air outlet duct 3b.

In particular, the second portion <NUM> of the side wall <NUM> extends between an end area 31a thereof at the air outlet opening <NUM> and an end area 31b thereof adjacent to the junction between the impeller chamber 3a and the radially inner side of the air outlet duct 3b.

The cover half shell <NUM> therefore comprises a peripheral edge <NUM> that extends partly along the perimeter of the cover end wall <NUM> and partly along the second portion <NUM> of the side wall <NUM>.

The base half shell <NUM> and the cover half shell <NUM> are joined to each other. More specifically, the peripheral edge <NUM> of the base half shell <NUM> and the peripheral edge <NUM> of the cover half shell <NUM> are joined to each other in a relationship of abutment against each other in a manner known per se in the industry, such as by screws or snap fasteners arranged along these peripheral edges, or by means of adhesives or welding.

When the base half shell <NUM> and the cover half shell <NUM> are joined to each other to make the housing <NUM>, the side wall <NUM> of the housing <NUM> is formed by the union between the first portion <NUM> and the second portion <NUM>. In particular, near the junction between the impeller chamber 3a and the radially inner side of the air outlet duct 3b there is a coupling between an edge of the end area 21b of the first wall portion <NUM> and the end area 31b of the second wall portion <NUM>. In the assembled housing <NUM>, the impeller chamber 3a is enclosed between the base end wall <NUM> and the first wall portion <NUM> of the cover half shell <NUM> on one side, and the cover end wall <NUM> of the cover half shell <NUM> on the other side, as may be seen in <FIG>. In contrast, the air outlet duct 3b, for most of its length, and the air outlet opening <NUM> are enclosed between the base end wall <NUM> and the first wall portion <NUM> (radially outer side of the duct) of the cover half shell <NUM> on the one side, and the cover end wall <NUM> and the wall portion <NUM> (radially inner side of the duct) of the cover half shell <NUM> on the other, as may be seen in <FIG> and <FIG>. At the junction between the impeller chamber 3a and the air outlet duct 3b, the air outlet duct 3b is initially enclosed between the base end wall <NUM> (radially outer side and radially inner side of the duct) and the first wall portion <NUM> of the cover half shell <NUM> on one side, and the cover end wall <NUM>. Moving toward the air outlet opening <NUM>, the height of the first wall portion <NUM> of the base half shell <NUM> on the radially inner side of the duct decreases, giving way to the second wall portion <NUM> of the cover half shell <NUM>, the height of which increases accordingly. However, this transition is limited in a short segment of the air outlet duct 3b near the junction with the impeller chamber 3a.

The sound absorption structure of the blower is obtained by the chamber side panel <NUM> and the outlet side panel <NUM>.

The chamber side panel <NUM> is shown in <FIG>, <FIG> and <FIG>. The chamber side panel <NUM> is fitted into a seat <NUM> formed in the base half shell <NUM>, whereby it faces the impeller chamber 3a at a given distance from the first wall portion <NUM>. This creates at least one resonant cavity <NUM> between the chamber side panel <NUM> and the first wall portion <NUM>, which cavity is fluidically connected with the impeller chamber 3a. This fluidic connection is made through a plurality of slits <NUM> formed on (or rather, through) the chamber side panel <NUM>. In the example shown, these slits <NUM> are formed as an array of parallel slits extending approximately along the main direction of the airflow in the impeller chamber 3a. However, the shape and arrangement of the slits may be designed differently from those depicted in the figures, depending on the conditions under which the blower is expected to operate.

A porous sound absorption material (not shown) may be placed inside the resonant chamber <NUM>.

The chamber side panel <NUM> is arch-shaped (see in particular <FIG>). The seat <NUM> that receives the chamber side panel <NUM> is formed as a recess in the first wall portion <NUM>, facing the impeller chamber 3a (see in particular <FIG>). When fitted into the relative seat <NUM>, the chamber side panel <NUM> has a surface <NUM> facing the impeller chamber 3a that is flush with a surface 21c, facing the impeller chamber 3a, of an area of the first wall portion <NUM> adjacent to the seat <NUM>.

The chamber side panel <NUM> and the relative seat <NUM> have an angular extension α, with respect to the central axis x of the impeller chamber 3a, of less than <NUM>°. The chamber side panel <NUM> and the seat <NUM> extend along a segment of the perimeter of the impeller chamber 3a from the end area 21b of the first portion of the wall at the junction between the impeller chamber 3a and the radially inner side of the air outlet duct 3b. This arrangement makes it possible to limit the sound absorption structure where the effects of the turbulence created by the airflow in the impeller chamber are most significant.

As may be seen in <FIG>, the chamber side panel <NUM> has side ends 40a, 40b that are coupled to respective side ends 23a, 23b of the relative seat <NUM>. In particular, the insertion of the chamber side panel <NUM> into the seat <NUM> is done through ribs <NUM> fitted onto the side ends 40a, 40b of the chamber side panel <NUM>, which are fitted into respective guide grooves <NUM> formed in the ends 23a, 23b of the seat (the arrangement of ribs and grooves may be reversed from that described above, if necessary). Thus, the insertion of the chamber side panel <NUM> occurs substantially in the direction of the height of the first wall portion <NUM>.

The chamber side panel <NUM> also has terminal ends 40c, 40d coupled to the base end wall <NUM> and to the cover end wall <NUM>, respectively. This coupling is achieved by means of alignment pins <NUM> fitted onto the terminal ends 40c, 40d of the chamber side panel <NUM>, which are fitted into respective holes 6b, 7b formed in the base end wall <NUM> and in the cover end wall <NUM> (the arrangement of pins and holes may be reversed from that described above, if necessary).

The chamber side panel <NUM> has rearwardly at least one ledge protrusion <NUM> that extends within the seat <NUM> up to the lowered part 21d of the first wall portion <NUM> surrounding the seat <NUM>. This achieves a complete closure of the seat <NUM> by the chamber side panel <NUM>.

The outlet side panel <NUM> is shown in <FIG>, and <FIG>. The outlet side panel <NUM> is fitted into a seat <NUM> formed in the cover half shell <NUM> so that it faces the air outlet duct 3b, at a given distance from the second wall portion <NUM>. This creates at least one resonant cavity <NUM> between the outlet side panel <NUM> and the second wall portion <NUM>, which cavity is fluidically connected with the air outlet duct 3b. This fluidic connection is made by means of a plurality of slits <NUM> formed on (or rather, through) the outlet side panel <NUM>. In the example shown, these slits <NUM> are formed as an array of parallel slits extending approximately along the main direction of the airflow in the air outlet duct 3b. However, the shape and arrangement of the slits may be designed differently from those shown in the figures, according to the conditions under which the blower is expected to operate.

The seat <NUM> that receives the outlet side panel <NUM> is formed as a recess in the second wall portion <NUM>, facing the air outlet duct 3b (see in particular <FIG>). When fitted into the relative seat <NUM>, the outlet side panel <NUM> has a surface <NUM> facing the air outlet duct 3b that is flush with a surface 31c, facing the air outlet duct 3b, of an area of the second wall portion <NUM> adjacent to the seat <NUM>.

The outlet side panel <NUM> and the seat <NUM> extend for a partial segment of the length of the air outlet duct 3b from the end area 31b of the second wall portion <NUM> adjacent to the junction between the impeller chamber 3a and the radially inner side of the air outlet duct 3b. This arrangement makes it possible to limit the sound absorption structure where the effects of the turbulence created by the airflow in the impeller chamber are most significant.

As may be seen in <FIG>, the outlet side panel <NUM> has side ends 50a, 50b that are coupled to respective side ends 33a, 33b of the relative seat <NUM>. In particular, the insertion of the outlet side panel <NUM> into the seat <NUM> is done through ribs <NUM> fitted onto the side ends 50a, 50b of the outlet side panel <NUM>, which are fitted into respective guide grooves <NUM> formed in the ends 33a, 33b of the seat (the arrangement of ribs and grooves may be different from that described above, e.g., reversed therefrom). Thus, the insertion of the outlet side panel <NUM> occurs substantially in the direction of the height of the second wall portion <NUM>.

The outlet side panel <NUM> also has terminal ends 50c, 50d coupled to the cover end wall <NUM> and to the base end wall <NUM>, respectively. This coupling is done by means of alignment holes/pins <NUM> formed on the terminal ends 50c, 50d of the outlet side panel <NUM>, which are coupled to respective alignment pins/holes 7c, 6c formed in the cover end wall <NUM> and in the base end wall <NUM> (the arrangement of pins and holes may be different from that described above, e.g. reversed therefrom).

The outlet side panel <NUM> has rearwardly at least one ledge projection <NUM> that extends within the seat <NUM> to the lowered part 31d of the first wall portion <NUM> surrounding the seat <NUM>. In this way, a complete closure of the seat <NUM> by the outlet side panel <NUM> is obtained.

Claim 1:
A housing of plastics material for a centrifugal blower for automotive HVAC systems, having a base end wall (<NUM>), a cover end wall (<NUM>) and a side wall (<NUM>) extending between the base end wall (<NUM>) and the cover end wall (<NUM>), in said housing there being defined an impeller chamber (3a) and an air outlet duct (3b), wherein on the cover end wall (<NUM>) there is formed an air inlet opening (<NUM>) facing the impeller chamber (3a), and on the side wall (<NUM>) there is formed an air outlet opening (<NUM>) facing the air outlet duct (3b),
wherein a sound absorption structure is arranged on said side wall, said sound absorption structure comprising at least one resonant cavity (<NUM>, <NUM>) fluidically connected to the impeller chamber (3a) and the air outlet duct (3b) through a plurality of slits (<NUM>, <NUM>) arranged on the side wall (<NUM>) and facing at least one of said impeller chamber and air outlet duct,
characterized by comprising
a base half shell (<NUM>) formed by the base end wall (<NUM>) and by a first portion (<NUM>) of the side wall (<NUM>), protruding from the base end wall (<NUM>), said first portion of the side wall surrounding the impeller chamber (3a) and delimiting on a radially outer side the air outlet duct (3b),
a cover half shell (<NUM>) formed by the cover end wall (<NUM>) and by a second portion (<NUM>) of the side wall (<NUM>), protruding from the cover end wall (<NUM>), said second portion of the side wall delimiting on a radially inner side the air outlet duct (3b), and
at least one of:
- a chamber side panel (<NUM>) fitted in a seat (<NUM>) formed in the base half shell (<NUM>) and facing said impeller chamber (3a), wherein said at least one resonant cavity (<NUM>) is formed between the chamber side panel (<NUM>) and said first portion (<NUM>) of the side wall (<NUM>), and wherein said slits (<NUM>) are formed on the chamber side panel (<NUM>), and
- an outlet side panel (<NUM>) fitted in a seat (<NUM>) formed in the cover half shell (<NUM>) and facing said air outlet duct (3b), wherein said at least one resonant cavity (<NUM>) is formed between the outlet side panel (<NUM>) and said second portion (<NUM>) of the side wall (<NUM>), and wherein said slits (<NUM>) are formed on the outlet side panel (<NUM>),
wherein the base half shell (<NUM>) and the cover half shell (<NUM>) are joined to each other.