JP4172005B2 - Low noise and high efficiency vacuum pump - Google Patents

Description

[0001]
The present invention includes first and second cylinders of the same diameter, in which first and second pistons respectively moved by eccentric rings define first and second volume chambers, respectively. Each cylinder has an inlet to which a check suction valve is attached and an outlet to which a check discharge valve is attached.
[0002]
This type of vacuum pump, which was widely used in the industry before the spread of rotary pumps, has the advantage of being able to form dry pumps that do not require lubrication.
[0003]
On the other hand, these pumps are conventionally designed such that the pistons operate in antiphase, i.e. the instantaneous sum of the volume chambers defined by the pistons in both cylinders is kept substantially constant.
[0004]
This method of operation not only produces undesirable vibrations due to the reciprocating mass that is difficult to balance, but also prevents the use of optimized eccentrics and increases the difficulty of balancing.
[0005]
The present invention is related to this, and its object is to provide a vacuum pump that generates less vibration than known pumps but nevertheless has high efficiency.
[0006]
For this reason, the vacuum pump of the present invention according to the above introduction essentially has cylinders aligned with each other and arranged symmetrically with respect to the main axis, the piston being symmetrical with respect to the main axis and the first and The first and second suction chambers are simultaneously driven by a suction motion in which the second volume chamber increases and a discharge motion that is symmetric with respect to the main axis and the first and second volume chambers decrease, respectively. It has two durations, and the first duration is longer than the second duration.
[0007]
These features of optimizing the suction process without imbalance the moving load make it possible to improve the efficiency of the pump without increasing the troublesome vibrations.
[0008]
According to an advantageous embodiment of the invention, each eccentric is formed in the form of a guide on one and the same cam that is driven in an isorotational movement about the main axis, which cam is symmetrical about the main axis. The piston suction movement occurs from the cam rotation over the first angular width, the piston discharge movement occurs from the cam rotation over the second angular width, and the first angular width is greater than the second angular width. It can be provided.
[0009]
For example, the cam may be shaped as a closed secondary axisymmetric curve with a minimum radial dimension and a maximum radial dimension between which an angle other than 90 degrees is formed. It's okay.
[0010]
In this case, the angle formed between the minimum length and the maximum length radial dimension of the cam may have a minimum value equal to at least 70 degrees and a maximum value equal to at most 110 degrees. preferable.
[0011]
The cam may have a shape derived from an ellipse from the distorted image, or on the other hand, parallel to the minimum length radial dimension and greater than the minimum length radial dimension and the maximum length. It may have an intermediate length smaller than the radial dimension.
[0012]
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings as a non-limiting example.
[0013]
The vacuum pump of the present invention includes, in a well-known manner, first and second cylinders 1 and 2 having the same diameter D, in which the first and second pistons 3 and 4 slide in a sealed manner. Move.
[0014]
Each cylinder 1 and 2 is provided with inlets 11 and 21 where check suction valves 13 and 23 are installed, and outlets 12 and 22 where check discharge valves 14 and 24 are installed.
[0015]
The inlets 11 and 21 are connected to the chamber 6, and the pump empties the gas therein. The outlets 12 and 22 are discharged into the atmosphere, for example.
[0016]
The first and second pistons 3 and 4 are moved by eccentric rings 51 and 52, respectively, and define first and second volume chambers V1 and V2 in the cylinders 1 and 2, respectively.
[0017]
According to the invention, the cylinders 1, 2 are aligned with each other and are symmetric with respect to the main axis X, which is perpendicular to the plane of the drawing.
[0018]
Each of the pistons 3 and 4 has a suction movement such as MA1 and MA2 in which the first and second volume chambers V1 and V2 increase, and MR1 and MR2 in which the first and second volume chambers V1 and V2 decrease. It is driven alternately with the discharge motion.
[0019]
However, the respective suction movements MA1, MA2 of the first and second pistons 3, 4 occur simultaneously and symmetrically with respect to the main axis X with respect to these two pistons 3, 4.
[0020]
Similarly, the respective discharge movements MR1, MR2 of the first and second pistons 3, 4 occur simultaneously and symmetrically with respect to the main axis X with respect to these two pistons 3, 4.
[0021]
Furthermore, the suction and discharge movements MA1, MA2 and MR1, MR2 have different first and second durations t1, t2, respectively, and each suction movement MA1, MA2 has a duration t2 of each discharge movement MR1, MR2. Longer duration t1.
In the preferred embodiment shown in FIG. 1, each of the eccentric wheels 51 and 52 is formed in the shape of a guide on one and the same cam 5 that is driven around the main axis X by an equal rotational motion.
[0022]
The guides of the pistons 3 and 4 are fixed to the translational pistons using springs such as 7 and 8 acting in a compressed or tensile state as in the embodiment shown in FIG. It is obtained by pressing rollers 31 and 41 against the contour of the cam 5.
[0023]
The cam 5 that rotates about the main axis X may have this axis as a symmetric primary axis, that is, the cam contour may be invariant with respect to rotation of 2 × PI / N radians about the axis X. Acceptable, N is an even number.
[0024]
More specifically, in the illustrated embodiment, the suction movements MA1, MA2 of the pistons 3, 4 result from the rotation of the cam 5 over the first angular width A1, whereas the discharge movements MR1, MR2 of the pistons 3, 4 are the first. It arises from the rotation of the cam 5 over two angular widths A2, and the first angular width A1 is larger than the second angular width A2.
[0025]
In order to achieve this, as shown in FIGS. 2 and 3, the cam 5, which in this case is shaped as a closed curve symmetrical to the secondary axis, has a radial dimension with a minimum length L1 and a radial dimension with a maximum length L2. And angles A1 and A2 other than 90 degrees are formed between them.
[0026]
In other words, the cam 5 is entirely covered by a circle with a diameter L2 centered on the axis X, and also covers a circle with a diameter L1 centered on the axis X, and is tangential to the cam. The tangents T1, T2 or T′1, T′2 for these circles forming a complementary angle A1 and A2 between them, the first angle A1 being larger than the second angle A2.
[0027]
Preferably, angle A1 is at most 110 degrees, so angle A2 is at least equal to 70 degrees.
[0028]
As shown in FIG. 3, the cam 5 may have a shape obtained from an elliptical shape by a distorted image.
[0029]
However, in order to reduce the acceleration transmitted to the pistons 3 and 4, parallel to the radial dimension of the minimum length L1, larger than the radial dimension of the minimum length L1 and smaller than the radial dimension of the maximum length L2. It is preferable to use a cam similar to the cam shown in FIG. 2 having an intermediate width L3.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vacuum pump according to the present invention.
FIG. 2 is a schematic view of a first cam that can be used in a vacuum pump according to the present invention.
FIG. 3 is a schematic view of a second cam that can be used in a vacuum pump according to the present invention.

Claims (5)

First and second cylinders (1, 2) having the same diameter (D) are included, and in these cylinders, first and second pistons (3,4) respectively moved by eccentric rings (51, 52). ) Define first and second volume chambers (V1, V2), respectively, and each cylinder has an inlet (11, 21) to which a check suction valve (13, 23) is attached and a check discharge valve (14). , 24), the cylinders (1, 2) are aligned with each other and arranged symmetrically with respect to the main axis (X), and the piston (3, 22) 4) is symmetric with respect to the main axis (X) and symmetric with respect to the main axis (X) and the suction movement (MA1, MA2) in which the first and second volume chambers (V1, V2) increase. And a discharge motion (MR1, MR2) in which the first and second volume chambers (V1, V2) are reduced, and Each of the suction and discharge motions (MA1, MA2, MR1, MR2) is driven simultaneously and has different first and second durations (t1, t2), and the first duration (t1) is the second duration ( A vacuum pump characterized by being longer than t2). 2. The vacuum pump according to claim 1, wherein each eccentric ring (51, 52) is formed in the shape of a guide on one same cam (5) driven by equal rotational movement about the main axis (X). The cam can accept this main axis as a symmetric primary axis, and the suction movement (MA1, MA2) of the piston (3, 4) arises from the rotation of the cam (5) over the first angular width (A1) and the piston ( 3 and 4) that the discharge motion (MR1, MR2) results from the rotation of the cam (5) over the second angular width (A2) and that the first angular width (A1) is greater than the second angular width (A2). A featured vacuum pump. 3. The vacuum pump according to claim 2, wherein the cam (5) is shaped as a closed curve symmetrical about the secondary axis and has a radial dimension with a minimum length (L1) and a radial dimension with a maximum length (L2). The vacuum pump is characterized in that an angle (A1, A2) other than 90 degrees is formed between them. 4. The vacuum pump according to claim 3, wherein the angle (A1, A2) formed between the radial lengths of the minimum length and the maximum length (L1, L2) of the cam (5) is at least equal to 70 degrees. Vacuum pump characterized in that it has a value and a maximum value equal to at most 110 degrees. The vacuum pump according to claim 2 or 3, wherein the cam (5) is parallel to the radial dimension of the minimum length (L1) and is larger than the radial dimension of the minimum length (L1) and has a maximum length (L2). A vacuum pump characterized by having an intermediate length (L3) smaller than the radial dimension of

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