Scroll type fluid apparatus

This invention relates to a scroll type fluid apparatus, and more particularly, to a scroll type supercharger for use in an automotive engine.

A scroll type fluid apparatus can be used in a compressor or a supercharger. When a high compression ratio is required rather than a high discharge flow rate, the scroll type fluid apparatus may be used in a compressor as disclosed in US-A-4477238. On the other hand, when a high discharge flow rate is required rather than a high compression ratio, the scroll type fluid apparatus may be applied to a supercharger as disclosed in Japanese Patent Application Publication No. 58-62301. However, the mentioned scroll type supercharger cannot obtain a sufficiently high discharge flow rate in comparison with other types of supercharger, such as a roots displacement compressor as disclosed in Japanese Utility Model Application Publication No. 62-183,092, assuming that the outer dimensions of the two apparatus are generally the same.

To eliminate this defect DE-A-3141525 discloses a scroll type supercharger including an orbiting scroll having a plate member from which first and second spiral elements project in opposite directions. A third spiral element interfitting with the first spiral element to define at least one pair of fluid pockets projects from an inner surface of one end of a housing. A fourth spiral element interfitting with the second spiral element to define at least one pair of fluid pockets projects from an inner surface of the other end of the housing. A driving mechanism including a crank shaft is operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll. Rotational motion of the orbiting scroll is prevented by a rotational preventing device during orbital motion of the orbiting scroll. A pair of balance weights are attached to both axial ends of a crank pin of the crank shaft.

In the above-mentioned scroll type supercharger, pressure in the fluid pockets is gradually increased with decreasing volume of the fluid pockets during orbital motion of the orbiting scroll. Therefore, the plate member receives a force the direction of which is in parallel with the axis of the crank shaft (referred to as axial force hereinafter) by virtue of pressure in the fluid pockets. But, the above-mentioned axial force is generated by virtue of pressure in the fluid pockets which are defined both by the first and third spiral elements and by the second and fourth spiral elements. Therefore, the axial forces received by the plate member are offset against each other whereby the plate member is not bent by axial forces. This gives the above-mentioned scroll type supercharger an advantage.

However, in the above-mentioned scroll type supercharger, both the first and second spiral elements are formed on the single plate member, and it is difficult to manufacture the orbiting scroll with the necessary accuracy of relative location of the first and second spiral elements, and this causes poor productivity and high manufacturing cost.

It is a primary object of this invention to provide a scroll type supercharger having an orbiting scroll which is easily manufactured but which has substantially balanced axial forces.

According to the invention, a scroll type fluid apparatus comprising an orbiting scroll having a plate member from opposite faces of which which a first spiral element and a second spiral element respectively extend; a first concave shell including a first fixed scroll having a first end plate from which a third spiral element extends; a second concave shell including a second fixed scroll having a second end plate from which a fourth spiral element extends; the first and second concave shells cooperating to define a chamber in which the first, second, third and fourth spiral elements are located, the orbiting scroll and the first fixed scroll being maintained angularly and radially offset from each other so that the first and third spiral elements interfit to form at least one pair of fluid pockets, and the orbiting scroll and the second fixed scroll also being maintained angularly and radially offset from each other so that the second and fourth spiral elements interfit to form at least one pair of fluid pockets; a driving mechanism operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll, the driving mechanism including a drive shaft having a balance weight; and rotation preventing means for preventing rotational motion of the orbiting scroll during orbital motion of the orbiting scroll, is characterised in that the plate member of the orbiting scroll is divided into a first plate member having the first spiral element and a second plate member having the second spiral element, the plate members being spaced to define a hollow portion in which the balance weight is disposed, the hollow portion being connected to the fluid pockets.

In the accompanying drawings:- <ul id="ul0001" list-style="none"><li>Figure 1 is a vertical longitudinal sectional view of one example of a scroll type supercharger in accordance with the present invention; and,</li><li>Figure 2 is a perspective view of the scroll type supercharger shown in Figure 1.</li></ul>

The illustrated scroll type supercharger 10 includes an orbiting scroll 20 having first and second plate members 21, 22. First and second spiral elements 211, 221 extend in opposite directions from the first and second plate members 21, 22 respectively. First and second bosses 212, 222 are formed on the surfaces of respective ones of the first and second plate members 21, 22 and face each other. First and second annular projections 213, 223, of which the length is greater than that of the bosses 212, 222 respectively project from the surfaces of the first and second plate members 21, 22 and contact each other at their projecting ends and surround the first and second bosses 212, 222. An inner portion of the projecting end of the first projection 213 and an outer portion of the projecting end of the second projection 223 are cut-out respectively to accept an O-ring 30 for sealing the mating surfaces between the projecting ends of the first and second projections 213, 223. A plurality of bolts 31 are screwed into the first and second projections 213 and 223.

A front casing 40 (to the left in Figure 1) includes a first end plate portion 411 from which a third spiral element 412 extends. The first end plate 411 and the third spiral element 412 substantially form a fixed scroll 41. The first plate member portion of the orbiting scroll 20 and the first fixed scroll 41 are maintained angularly and radially offset from each other so that the first and third spiral elements 211, 412 interfit to form at least one pair of fluid pockets 23. A third boss 413 is formed at an outer surface of the first end plate 411, that is, remote from the third spiral element 412.

A rear casing 50 (to the right in Figure 1) includes a second end plate 511 from which a fourth spiral element 512 extends. The second end plate 511 and fourth spiral element 512 substantially form a second fixed scroll 51. The second plate member portion of the orbiting scroll 20 and the second fixed scroll 51 are maintained angularly and radially offset from each other so that second and fourth spiral elements 221 and 512 interfit to form at least one pair of fluid pockets 24. A fourth boss 513 is formed at an outer surface, that is, remote from the fourth spiral element 512. An adapter 514 having an annular flange portion 514a which extends outwardly from an outer peripheral surface of the adapter 514 is provided with a plurality of outlet ports 514b. The adapter 514 is fitted into an inner peripheral wall of the fourth boss 513 to allow contact of the flange portion 514a with the fourth boss 513. A plurality of bolts 515 are screwed into the flange portion 514a and fourth boss 513 to secure the adapter 514 firmly to the rear casing 50.

Each first, second, third and fourth spiral element 211, 221, 412 and 512 is provided with a seal element 33 at its axial end surface. The front and rear casings 40, 50 are firmly joined by a plurality of bolts 42a and nuts 42b through a gasket 43 to define an operational chamber 25.

A driving mechanism 600 includes a drive shaft 60. Holes 414, 515 are centrally formed in the first and second end plates 411 and 511 respectively for penetration by the drive shaft 60. The drive shaft 60 is rotatably supported by the third boss 413 and adapter 514 through bearings 44 and 52 forcibly inserted in an inner peripheral wall of the third boss 413 and the adapter 514 respectively. The bearing 52 is firmly secured to the adapter 514 by a snap ring 521 and nut 522. A pulley 61 is mounted onto a front end (to the left in Figure 1) of the drive shaft 60 beyond a toothed wheel 62. The toothed wheel 62 is firmly secured onto the drive shaft 60 by a nut 63 and key mechanism 64. The pulley 61 is also firmly secured onto the drive shaft 60 by a nut 65 and key mechanism 66. A spacer 67 is disposed between the nut 63 and the pulley 61. A shaft seal mechanism 68 is disposed at a rear of the bearing 44.

A crank pin 69 is penetrates through the drive shaft 60 and is firmly secured to a central portion of the drive shaft 60 by a nut 691. An axis of the crank pin 69 is radially offset from an axis of the drive shaft 60 by a predetermined distance. A cavity 692 is longitudinally bored through the crank pin 69 to link the central fluid pockets 23a, 24a. The crank pin 69 is rotatably supported by bosses 212, 222 through bearings 45, 46 forcibly inserted in inner peripheral walls of the bosses 212, 222. Accordingly, the first and second plate members 21, 22 orbit synchronously in virtue of the driving mechanism 600.

A balance weight 693 is disposed on the crank pin 69 opposite the offest of the axis of the crank pin 69 with respect to the axis of the drive shaft 60 and is fixedly secured thereto by a key mechanism 694. A port 695 is formed in the crank pin 69 to link the cavity 692 to the hollow portion 32. The port 695 and cavity 692 forms a conduit.

A rotation preventing mechanism 70 includes a crank shaft 71 having a pin member 72 extending from a rear end of the crank shaft 71. The crank shaft 71 penetrates through a cylindrical portion 73 formed at a top of the front casing 40 and is in parallel with the drive shaft 60. A pair of bearings 47, 48 are disposed at an inner peripheral wall of both ends of the cylindrical portion 73 to support rotatably the crank shaft 71. An axis of the pin member 72 is radially offset from an axis of the crank shaft 71 by a predetermined distance which is similar to the distance between the axis of the crank pin 69 and the axis of the drive shaft 60. Between the bearings 47 and 48, a balance weight 74 is disposed on the crank shaft 71 offset from the axis of the pin member 72 with respect to the axis of the crank shaft 71 and is fixedly secured to the crank shaft 71 by a key mechanism 75.

A toothed wheel 711 is mounted onto a front end (to the left in Figure 1) of the crank shaft 71 and is firmly secured to the crank shaft 71 by a nut 712 and key mechanism 713. The toothed wheel 711 is similar to the toothed wheel 62, that is, both toothed wheels 62 and 711 have the same diameter and number of teeth. The toothed wheels 711 and 62 are engaged by a timing belt 80 so as to rotate synchronously.

An open end box 75 provided with a bearing 49 and a shaft seal 81 therewithin is diposed between the first and second plate members 21 and 22. The open end of the box 75 faces the first plate member 21 and is provided with an annular flange 751 radially extending therefrom. The pin member 72 penetrates through the first plate member 21 and into the inside of the box 75. The box 75 rotatably supports the pin member 72 through a bearing 49. A shaft seal 81 is mounted onto the pin member 72 in front (to the left in Figure 1) of the bearing 49. An annular flange 751 is fixed to the first plate member 21 by a plurality of bolts 82. The closed end of the box 75 is fixed to the second plate member 22 by a plurality of bolts 83.

Accordingly, rotational motion of the first and second plate members 21, 22 is prevented by the rotation preventing mechanism 70 during orbital motion of the first and second plate members 21, 22, thereby only synchronous orbital motion is permitted.

Semicircular holes 91, 92 are respectively formed in the front and rear casing 40, 50 to form an inlet port 90 as shown in Figure 2.

Operation of the above-mentioned scroll type supercharger structure is as follows.

Driving force is transferred to the pulley 61 from an outer power source, such as an engine of vehicle through a belt, whereby the drive shaft 60 rotates. This rotation is converted to orbital motion of the orbiting scroll 20 through the crank pin 69, rotational motion being prevented by the rotation preventing mechanism 70. Air introduced into the operational chamber 25 through the inlet port 90 is taken into the outer fluid pockets 23b, 24b between the first plate member 21 portion of the orbiting scroll 20 and the first fixed scroll 41, and the second plate member 22 portion of orbiting scroll 20 and the second fixed scroll 51, and then moves inwardly towards the centre of the spiral elements 211, 412 and 221, 512 owing to the orbital motion of orbiting scroll 20. As the air moves towards the central pockets 23a, 24a, it undergoes a resultant volume reduction and compression, for example, 0.1 - 0.8 kg/cm G. This compressed air is discharged to an outlet pipe (not shown) linking the supercharger 10 to the engine of the vehicle through outlet ports 514b. Particularly, compressed air in the fluid pocket 23a is discharged to the outlet pipe after flowing through the cavity 692 and joining compressed air in the fluid pocket 24a. A part of the compressed air flows into the hollow portion 32 through the cavity 692 and port 695 so that the hollow portion 32 is filled with compressed air. As a result, the first and second plate members 21, 22 can avoid becoming bent by unbalanced axial forces generated by virtue of the pressure in the fluid pockets.

Furthermore, a radial dimension of the casing of the supercharger can be reduced by the location of the balance weight 693 within the hollow portion 32.