Roots blower with improved clearance between rotors

• US 5,040,959 A
• Filed: 02/07/1990
• Issued: 08/20/1991
• Est. Priority Date: 02/17/1989
• Status: Expired due to Term

• Current Assignee: Fuji Jukogyo Kabushiki Kaisha 7-2
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Fukagawa, Tetsuo
• Primary Examiner(s): Vrablik, John J.
• Application Number:
  US07/476,313
• Time in Patent Office: 559 Days
• Field of Search: 418/150, 418/206
• US Class Current: 418/150
• CPC Class Codes: F04C 18/126 with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type

Abstract

A Roots blower has two rotors in which each of said rotors, as viewed in plan view thereof in the direction of the rotational axis thereof. The rotor has a center and orthogonal short and long axes and has a final shape of a contour offset from a basic profile curve by an offset distance at every point thereof in the normal line direction thereto. The offset distance is also determined in accordance with a function which assumes a maximum value when the angle between a line connecting the rotor center with the point and either of the short and long axes is 45 degrees, which assumes a minimum value when the line coincides with either of the short and long axes, and the function comprises an exponential power of a sine function.

Claims

1. A Roots blower having a plurality of rotors, each of said rotors having a center, an orthogonal short and a long axes and a contour shape offset from a basic profile curve, the improvement in said blower wherein:

said basic profile curve is a combination of epicycloidal curves and hypocycloidal curves, and

said contour shape offset is defined by an equation;

space="preserve" listing-type="equation">L=L1+L2 (sin 2θ

).sup.n

where;

L is a value of said contour offset;

θ

is an angle relative to a coordinate axes of a rolling circle of said cycloidal curve;

L1=S_min 0×

1/2, where S_min 0 is a clearance when said rolling circle angle θ

=0 degrees;

L2=(S_min 45-S_min

     0)×

1/2, where S_min 45 is the clearance when the rolling circle angle θ

=45 degrees; and

n is an exponent.

2. A Roots blower having a plurality of rotors, each of said rotors having a center, an orthogonal short and a long axes and a contour shape offset from a basic profile curve, the improvement in said blower wherein:

said basic profile curve is a combination of epicycloidal curves and hypocycloidal curves, and

said shape is defined by a contour curve expressed by equations

space="preserve" listing-type="equation">X2=x-{L1+L2(sin 2Θ

).sup.n }sin ω

space="preserve" listing-type="equation">Y2=y+{L1+L2(sin 2Θ

).sup.n }cos ω

where;

X2, Y2 are coordinate axes values at a point on the epicycloidal and hypocycloidal curves;

X, Y are coordinate axes values at a point on the epicycloidal and hypocycloidal curves;

Θ

is an angle relative to a coordinate axes of a rolling circle of said cycloidal curve;

L1=S_min 0×

1/2, where S_min 0 is a clearance when said rolling circle angle Θ

0 degrees;

L2=(S_min 45=S_min

     0)×

1/2, where S_min 45 is the clearance when the rolling circle angle Θ

=45 degrees;

n is an exponent; and

ω

=tan^-1 (dy/dx), a tangent angle at said point x, y of said coordinate axes.