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Composite fluid machine

Composite fluid machine description/claims

The present invention relates to a composite fluid machine which has a first and a second fluid delivering mechanisms, and more specifically to a composite fluid machine in which suction flow rate of a first fluid delivering mechanism is displaced while a second fluid delivering mechanism includes helical roots rotors.

Japanese Unexamined Patent Application Publication No. 8-144977, whose corresponding U.S. Patent is also published as U.S. Pat. No. 5,549,463, discloses a dry vacuum pump including a pair of screw rotors in a housing. The pair of screw rotors is rotated while engaging with each other. The fluid is introduced from an inlet into a suction space formed in the housing so as to communicate with the inlet, and is discharged from the housing. Japanese Unexamined Patent Application Publication No. 2006-083783 discloses a screw type fluid machine in which the fluid is introduced into a housing, then compressed, and delivered from the suction side to the discharge side. In such screw type fluid machines, the flow rate of the suction fluid into the suction space is displaced, that is, the increased volume introduced into the suction space per unit time is displaced,. Similarly, the flow rate of the suction fluid is displaced in a scroll type compressor. Such a fluid machine as a screw type fluid machine, a scroll type fluid machine, or a piston type fluid machine and the like is called as a positive displacement fluid machine. When a positive displacement fluid machine is employed, pulsation of suction fluid may occur due to the displacement of the flow rate introduced into the suction space. When the fluid machine introduces air which externally exists, the suction pulsation may cause noise.

The vacuum pump of Japanese Unexamined Patent Application Publication No. 8-144977 also includes on the vacuum side a roots pump with straight-shaped roots rotors. The flow rate of the suction fluid into the suction space is also displaced in the roots pump with straight rotors, and causes suction pulsation.

When a muffler or a resonator is attached at the suction side, the suction noise may be suppressed. However, the muffler or the resonator is large-sized, and accordingly the whole size of the fluid machine is increased.

The present invention is directed to a composite fluid machine having a first and a second fluid delivering mechanisms, which prevents increase in size while suppressing the suction pulsation.

In accordance with an aspect of the present invention, a composite fluid machine has a first and a second fluid delivering mechanisms. The first fluid delivering mechanism includes an accommodation chamber, a movable body, and a suction space. The movable body is accommodated in the accommodation chamber. The suction space is defined by the accommodation chamber and the movable body. The suction space is connected to the inlet, and the flow rate of the fluid introduced into the suction space is displaced. The movable body performs a suction movement to introduce the fluid into the suction space, and performs a discharge movement to discharge the fluid out from the accommodation chamber. The second fluid delivering mechanism is combined with the first fluid delivering mechanism so as to be located upstream of the first fluid delivering mechanism to deliver the fluid to the suction space of the first fluid delivering mechanism. The second fluid delivering mechanism includes a roots rotor housing and a pair of helical roots rotors,. The helical roots rotors have a respective rotational axis and plural lobes around the rotational axis. The lobes are engaged with each other when the helical roots rotors rotate in the roots rotor housing. The lobes are in a helical shape in such a manner that the lobes are twisted in a respective direction around the rotational axis.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims.. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a plane sectional view showing a composite fluid machine having a first and a second fluid delivering mechanisms according to a first embodiment of the present invention;

FIG. 2A is a cross-sectional view taken in line I-I of FIG. 1;

FIG. 2B is a cross-sectional view taken in line II-II of FIG.. 2A;

FIG. 3 is an illustrative view in which helical roots rotors of a helical roots type fluid delivering mechanism as the second fluid delivering mechanism are viewed from the rear side;

FIG. 4A is a side view of one of a pair of helical roots rotors of a helical roots type fluid delivering mechanism as the second fluid delivering mechanism;

FIG. 4B is a side view of the other of the pair of the helical roots rotors;

FIG. 5 is a plan sectional view according to a second embodiment of the present invention;

FIG. 6A is a plan sectional view according to a third embodiment of the present invention; and

FIG. 6B is a cross-sectional view taken in line IV-IV of FIG. 6A.

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