JP2002098045A - Pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce pump vibration in a pump provided with a reciprocating piston. SOLUTION: An eccentric shaft 41 of a crank shaft 40 is inserted into a hole part 14 formed at a center part of the piston 13, and the piston 13 is reciprocated as the crank shaft 40 is rotated. Piston mass on one end side to the eccentric shaft 41 can thus be set to be equal to piston mass on the other end side to the eccentric shaft 41 to reduce vibration of the pump. By respectively forming pump chambers 17 and 18 on both end sides of the piston 13, motor load when the piston 13 is moved from a position at one end to a position at the other end becomes equal to motor load when the piston is moved inversely, thereby load fluctuation is reduced to reduce motor vibration, and thus pump vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump for sucking and discharging a fluid as a piston reciprocates.
Particularly, it is suitable for a vacuum pump for sucking and discharging gas.

[0002]

2. Description of the Related Art In a conventional vacuum pump, one piston is reciprocated by a connecting rod connected to an eccentric shaft of a crankshaft by using an electric motor (driving means) as a drive source to reduce the volume of one pump chamber. By changing it, the gas is sucked and discharged to the outside (for example, Japanese Utility Model Publication No. 61-61).
No. 34923).

In order to reduce the vibration of the pump due to the inertial force of the piston or the eccentric shaft of the crankshaft,
A balance weight set in consideration of the mass of the piston and the eccentric shaft is provided integrally with the crankshaft.

[0004]

However, in the above-mentioned conventional pump, the mass is balanced by the piston, the eccentric shaft and the balance weight, and when an imbalance occurs due to a manufacturing error of those parts, the vibration of the pump is caused. Has not been able to be sufficiently reduced.

When the piston top dead center position is
When the crank angle is between 0 ° and 180 ° (intake stroke), the motor load is maximized when the crank angle is 90 °, and when the crank angle is between 180 ° and 360 ° (discharge stroke), it is 270 °.
The motor load becomes maximum at the time of. In the case of a vacuum pump, the negative pressure in the pump chamber exerts a force to pull the piston toward the top dead center position, so that the piston is more loaded than the motor load when the piston is at a crank angle of 270 ° toward top dead center. The motor load at a crank angle of 90 ° toward the bottom dead center becomes larger, and the peak torque of the motor load and, consequently, the motor load fluctuation increase. for that reason,
There is a problem that the motor is likely to vibrate, and consequently the pump is likely to vibrate.

[0006] The present invention has been made in view of the above points, and has as its object to reduce the vibration of a pump having a reciprocating piston.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a driving means (50) for generating a driving force and a crankshaft (40) rotated by the driving means (50) are provided. ) And eccentrically arranged with respect to the rotation center (a) of the crankshaft (40), and the crankshaft (40)
An eccentric shaft (41) rotating together with the eccentric shaft (41), and a piston (13) reciprocated in a direction perpendicular to the rotation center (a) of the crankshaft (40) with the rotation of the eccentric shaft (41). At the center of the piston (13) in the piston reciprocating direction (b), a hole (14) into which the eccentric shaft (41) is inserted is formed, and the piston (13) reciprocates in the piston reciprocating direction (b). Are characterized in that two pump chambers (17, 18) whose volumes change with the reciprocation of the piston (13) are formed at both ends of the pump chamber.

According to this, the piston can be made symmetrical with respect to the position of the hole (= with reference to the eccentric axis) as in the invention according to claim 2, so that the piston is located on one end side of the eccentric axis. And the piston mass at the other end side of the eccentric shaft can be made equal. Therefore, there is no need to balance including the mass of the piston as in the prior art, and the number of parts for balancing the mass is reduced,
The unbalance amount due to a manufacturing error is reduced, and the vibration of the pump can be reduced.

Further, as described above, in a conventional vacuum pump having one piston and one pump chamber, a force is exerted to pull the piston toward the top dead center position due to the negative pressure of the pump chamber. The peak torque at the time of driving toward the point side became extremely large, and the load fluctuation became large.

On the other hand, according to the first aspect of the present invention, the two pump chambers are provided both when the piston moves from one end position to the other end position and when the piston moves in the opposite direction. The fluid is sucked in one of the pump chambers, and the fluid is discharged in the other pump chamber. Therefore, the load of the driving means when the piston moves from one end position to the other end position is equal to the load of the driving means when the piston moves in the opposite direction, and the load fluctuation becomes small, Vibration and, consequently, pump vibration are reduced.

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIGS. FIG. 1 is a sectional view of a pump,
2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a B view of the crankshaft portion of FIG.

This pump is used, for example, as a vacuum pump for supplying a negative pressure to a vacuum booster of a vehicle braking system.

1 to 3, a housing 10 is formed with a crank chamber 11 having a columnar hole shape extending in a vertical direction. At both ends of the crank chamber 11, a thin cylinder made of stainless steel on which a piston described later slides. A cylindrical liner 12 is mounted.

The outer surface on the right side of the housing 10 is formed as a flat surface, and an electric motor (driving means) 50 is attached to the flat surface by screws or the like (not shown). The inside of the motor 50 communicates with the crankcase 11, and the air in the crankcase 11 is discharged into the atmosphere from the drain pipe 51 through the inside of the motor 50.

One end of a rotary shaft 52 of the motor 50 extends to the crank chamber 11, and a crankshaft (drive shaft) 40 is coaxially coupled to one end of the rotary shaft 52. This crankshaft 40
Is provided with one eccentric shaft 41 eccentrically arranged with respect to the rotation center a of the crankshaft 40 and the rotating shaft 52, and a bearing 42 mounted on the outer peripheral side of the eccentric shaft 41. ing. Further, the crankshaft 40 has an eccentric shaft 41
And a balance weight 43 for balancing the mass of the bearing 42.

A piston 13 is provided in the crank chamber 11 so as to reciprocate in a direction perpendicular to the rotation center a. A hole 14 is formed in the piston 13 at the center in the piston reciprocating direction b, and an eccentric shaft 41 and a bearing 42 are inserted into the hole 14. And
With the rotation of the crankshaft 40, the eccentric shaft 41 and the bearing 42 reciprocate the piston 13 while being displaced in the width W direction (see FIG. 2) in the hole portion 14.

The upper part and the lower part of the piston 13 in FIG. 1 are symmetrical with respect to the position of the hole 14 (that is, with reference to the axis c of the eccentric shaft 41). Accordingly, the mass of the piston 13 in the upper part of FIG. 1 with respect to the axis c of the eccentric shaft 41 is equal to the mass of the lower part in FIG. 1 with respect to the axis c. For this reason, the balance weight 43 of the crankshaft 40 does not need to be balanced including the mass of the piston as in the prior art.
Only the mass of the bearing 42 needs to be balanced.

The dashed line indicated by the symbol d in FIG. 2 indicates the rotation locus of the bearing 42 at the point farthest from the rotation center a. The diameter of the rotation locus d (≒ stroke of the piston 13) is set to about 21 mm, and the hole 14 is perpendicular to the reciprocating direction b of the piston and perpendicular to the rotation center a. Is set to be about 4 mm larger than the diameter of the rotation locus d. The hole 1 in the piston reciprocating direction b
4 is set slightly larger (about 0.1 mm) than the outer shape (about 10 mm) of the bearing 42.

The first and second end plates 1 are provided at both ends of the crank chamber 11 so as to close the openings.
5 and 16 are mounted. The first pump chamber 17 is formed by the first end plate 15, the housing 10, and the piston 13, and the second pump chamber 18 is formed by the second end plate 16, the housing 10, and the piston 13.

At the upper end of the housing 10, a pipe 1
A first cover 19 having a first space 19 a is provided between the first cover 19 and the first end plate 15.
Are formed. A second cover 21 is attached to the lower end of the housing 10.
A second space 22 is formed between the second space 22 and the end plate 16. The first and second spaces 20 and 22 communicate with each other through a communication hole 23 formed near the outer periphery of the housing 10.

At the outer peripheral portion of the piston 13, a piston ring 24 made of four-hooker ethylene (PTFE) having a low friction coefficient is mounted on both ends in the piston reciprocating direction b.
When the piston 13 reciprocates, the piston ring 24 slides on the inner peripheral surface of the cylinder liner 12 while maintaining airtightness.

On the first pump chamber 17 side of the piston 13, a ring-shaped first discharge check valve 25 made of rubber having high heat resistance and a first valve plate 26 are mounted. The piston 13 and the first valve plate 26 are formed with communication holes 13a and 26a for communicating the first pump chamber 17 and the crank chamber 11. The communication hole 26a of the first valve plate 26 is connected to the first discharge check valve 25.
The first discharge check valve 25 is opened when the pressure in the first pump chamber 17 becomes higher than the pressure in the crank chamber 11.

A ring-shaped second discharge check valve 27 made of rubber having high heat resistance and a second valve plate 28 are mounted on the second pump chamber 18 side of the piston 13. The piston 13 and the second valve plate 28 are formed with communication holes 13b and 28a for communicating the second pump chamber 18 with the crank chamber 11. The communication hole 28 a of the second valve plate 28 is connected to the second discharge check valve 27.
The second discharge check valve 27 is opened when the pressure in the second pump chamber 18 becomes higher than the pressure in the crank chamber 11.

The first end plate 15 is formed with a communication hole 15a for communicating the first pump chamber 17 with the first space 20, and the first pump chamber 1 in the first end plate 15 is formed.
A mushroom-shaped first suction check valve 29 that opens and closes the communication hole 15a is mounted on the seventh side. This first suction check valve 29
Is made of rubber having high heat resistance, and when the pressure in the first pump chamber 17 becomes lower than the pressure in the first space 20, the umbrella portion is deformed and the valve is opened.

The second end plate 16 is formed with a communication hole 16 a for communicating the second pump chamber 18 with the second space 22.
A mushroom-shaped second suction check valve 30 that opens and closes the communication hole 16a is mounted on the 8 side. This second suction check valve 30
Is made of rubber having high heat resistance, and when the pressure in the second pump chamber 18 becomes lower than the pressure in the second space 22, the umbrella portion is deformed and the valve is opened.

The housing 10, the piston 13, the end plates 15, 16, the covers 19, 21, and the valve plates 26, 28 are made of heat-resistant polybutylene terephthalate (PBT).

The first space 20 is connected to a pressure chamber in a vacuum booster of a vehicle braking device (not shown).

The operation of the pump having the above configuration will be described with reference to FIGS.

When the pressure in the pressure chamber in the vacuum booster becomes a negative pressure (negative pressure close to the atmospheric pressure side) or an atmospheric pressure lower than the set negative pressure, the motor 50 is energized and starts operating. .

When the motor 50 is energized, the crankshaft 40 rotates. With the rotation of the crankshaft 40, the piston 13 is pushed by the eccentric shaft 41 and the bearing 42, and reciprocates vertically in FIG. .

While the eccentric shaft 41 and the piston 13 are in the upper end position in FIG. 1 while the crankshaft 40 is rotated by 180 degrees, the piston 13 moves downward in FIG. 1 to the lower end position. The first pump chamber 17 suctions air, and the second pump chamber 18 discharges air.

That is, when the piston 13 moves downward in FIG. 1, the volume of the first pump chamber 17 increases, the pressure in the first pump chamber 17 decreases, and the pressure in the first pump chamber 17 decreases to the first pressure. When the pressure becomes lower than the pressure in the space 20, the first
The suction check valve 29 is opened, and the air in the pressure chamber of the vacuum booster is released from the first space 20 and the first end plate 15.
Is sucked into the first pump chamber 17 through the communication hole 15a.

On the other hand, on the second pump chamber 18 side, the volume is reduced, the pressure in the second pump chamber 18 increases, and when the pressure in the second pump chamber 18 becomes higher than the pressure in the crank chamber 11, The second discharge check valve 27 opens, and the air in the second pump chamber 18 is discharged to the crank chamber 11 through the communication hole 13b of the second piston 14 and the communication hole 28a of the second valve plate 28. .

Next, while the piston 13 moves from the lower end position to the upper end position, the first pump chamber 17
The air is discharged on the side, and the air is suctioned on the second pump chamber 18 side.

That is, when the piston 13 moves upward, the volume of the first pump chamber 17 is reduced,
When the pressure in the pump chamber 17 increases and the pressure in the first pump chamber 17 becomes higher than the pressure in the crank chamber 11, the first discharge check valve 25 opens, and the air in the first pump chamber 17 is released. ,
The exhaust gas is discharged to the crank chamber 11 through the communication hole 13a of the first piston 13 and the communication hole 26a of the first valve plate 26.

On the other hand, on the second pump chamber 18 side, the volume increases and the pressure in the second pump chamber 18 decreases, and the pressure in the second pump chamber 18 becomes lower than the pressure in the second space 22. , The second suction check valve 30 is opened. Then, the air in the pressure chamber of the vacuum booster flows through the first space 20, the communication hole 23 of the housing 10, the second space 22, and the communication hole 16 a of the second end plate 16 to form the second pump chamber 1.
Inhaled in 8.

With the above operation, when the pressure in the pressure chamber of the vacuum booster becomes a negative pressure (negative pressure close to the vacuum side) higher than the set negative pressure, the power supply to the motor 50 is stopped, and the pump is stopped.

In this embodiment, the piston 13 has the hole 14
(= Based on the axis c of the eccentric shaft 41), the piston mass at one end side of the axis c of the eccentric shaft 41 and the other than the axis c The piston mass of the end portion can be equalized. Therefore, the balance weight 43 of the crankshaft 40 does not need to be balanced including the mass of the piston as in the related art, and need only be balanced by the mass of the eccentric shaft 41 and the bearing 42 as described above. As described above, since the number of parts for balancing the mass is reduced, the amount of unbalance due to a manufacturing error is reduced, and the vibration of the pump can be reduced.

As described above, in the conventional vacuum pump having one piston and one pump chamber, the negative pressure in the pump chamber exerts a force to pull the piston toward the top dead center position. The motor load when the piston moves toward the bottom dead center side becomes larger than the motor load when moving toward the point side, and the peak torque of the motor load and, consequently, the motor load fluctuation increase.

On the other hand, in this embodiment, the piston 1
Whenever 3 moves from one end position to the other end position and moves in the opposite direction, air is sucked in one of the two pump chambers 17 and 18, and Air is discharged in the other pump chamber. Therefore, the motor load when the piston 13 moves from one end position to the other end position is equal to the motor load when the piston moves in the opposite direction, the motor load fluctuation becomes small, and the vibration of the motor 50 becomes small. Thus, the vibration of the pump is reduced.

The air discharged into the crank chamber 11 passes through the inside of the motor 50 and is discharged from the drain pipe 51 to the atmosphere. Then, the discharged air is supplied to the crank chamber 11.
Since the exhaust air expands when the air flows into the motor 50 from above, the air exhaust noise can be reduced. Further, the inside of the motor 50 can be cooled by the discharged air.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a pump according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a B view of the crankshaft portion of FIG. 1;

[Explanation of symbols]

13 piston, 14 hole, 17, 18 pump chamber,
40 ... Crank shaft, 41 ... Eccentric shaft, 50 ... Electric motor as drive means.

Continuation of the front page (72) Inventor Shin Sasaki 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3H076 AA03 AA21 BB01 CC07 CC25 CC43

Claims (3)

[Claims] 1. A driving means (50) for generating a driving force, a crankshaft (40) rotated by the driving means (50), and a rotational center (a) of the crankshaft (40). An eccentric shaft (41) that is arranged in a center and rotates with the crankshaft (40); and a rotation center (a) of the crankshaft (40) with the rotation of the eccentric shaft (41). A piston (13) reciprocated vertically in a vertical direction, and a hole (14) in which the eccentric shaft (41) is inserted in a central portion of the piston (13) in a piston reciprocating direction (b). Are formed at both ends of the piston (13) in the piston reciprocating direction (b). Two pump chambers (17, 18) whose volumes change with the reciprocating motion of the piston (13) are formed. Pump. 2. The piston (13) is provided with the hole (1).
The pump according to claim 1, wherein the pump has a symmetric shape with respect to the position (4). 3. The apparatus according to claim 1, wherein gas is sucked and discharged to the outside as the piston reciprocates.
Or the pump according to 2.