JPH0332791Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piston sliding vacuum pump.

[Prior art]

In general, a piston-sliding type vacuum pump has a piston part of the operating piston fitted into a cylinder part provided inside the pump housing so as to be able to slide in the axial direction in an airtight manner, and a check valve for suction installed on one side of the piston part. A negative pressure chamber is formed with a discharge check valve, and the rod portion of the actuating piston is connected to a pump drive shaft, and rotation of the drive shaft causes the actuating piston to slide, thereby forming a negative pressure chamber. The device is configured to apply the negative pressure generated in the negative pressure actuator to a negative pressure actuator.
It is shown in Publication No. 206685.

In this type of piston-sliding vacuum pump, a discharge check valve can be assembled into the piston part of the working piston, as shown in the same publication, in order to be compact and increase the pumping capacity. In addition, the check valves generally use valves in which a flat plate-shaped valve body is elastically seated on the valve seat using the urging force of a compression spring, or valves made of a flexible mushroom-shaped valve body. It is.

[Problem that the invention attempts to solve]

By the way, in the former valve, when the sliding speed of the actuating piston becomes high and the variation in the differential pressure acting on the valve becomes extremely rapid, the expansion and contraction movement of the compression spring cannot follow the variation speed of the differential pressure. As a result, the opening/closing timing of the valve may deviate from the proper opening/closing timing, and the set pump performance may not be fully exhibited. In addition, in the latter type of valve, the outer periphery where the valve opens and closes is functionally formed to be thin, so it ages and becomes hard and easily cracks, and also becomes loose when the valve opens and closes quickly. There is a risk of impairing sealing performance.

[Means for solving problems]

In order to deal with these problems, the present invention has been developed in this type of piston sliding vacuum pump.
A second cylinder portion coaxial with the cylinder portion and having a different diameter from the second cylinder portion is provided inside the pump housing, and the working piston is slidable in the second cylinder portion in an airtight manner and in the axial direction. A second piston part is provided to be fitted, a pressure chamber is formed between these two piston parts, and the pressure chamber is connected to the second piston part.
The discharge check valve communicates with the atmosphere, while the piston part is provided with a communication passage for communicating the negative pressure chamber and the pressure chamber, and a flat valve is adopted as the discharge check valve. A valve is interposed in the communication path.

[Functions and effects of the idea]

As a result, in the present invention, during the compression and exhaust strokes of the negative pressure chamber, the second discharge check valve closes and negative pressure is generated in the pressure chamber, and the discharge check valve (first discharge check valve) is closed by the action of the negative pressure. Discharge check valve) opens. Further, during the expansion and suction stroke of the negative pressure chamber, the second discharge check valve opens when a predetermined pressure is reached, and the first discharge check valve closes as the differential pressure between the negative pressure chamber and the pressure chamber increases.

That is, in the present invention, when the working piston slides, positive pressure and negative pressure are actively generated in the pressure chamber to increase the differential pressure between the pressure chamber and the negative pressure chamber, and a spring such as a compression spring is used. The first discharge check valve is opened and closed only by the action of this differential pressure without any pressure difference. Therefore, according to the present invention, regardless of the sliding speed of the working piston, the first discharge check valve can be opened and closed at appropriate timing according to the state of the negative pressure chamber, and the setting can be made. It is possible to fully demonstrate the pump performance. Note that since the first discharge check valve employs a valve made of a flat plate-shaped valve body, it goes without saying that problems caused by a valve made of a mushroom-shaped valve body do not occur.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIGS. 1 and 2 show a vacuum pump according to the present invention. The vacuum pump is a piston sliding type vacuum pump that uses an electric motor as a driving source, and has an operating piston 20 and a suction check valve 31 inside the pump housing 10.
Discharge check valves 32 and 33 are provided, and an electric motor 40 is attached to the bottom of one side of the pump housing 10.

The pump housing 10 includes a housing body 11,
It consists of a housing head 12, an upper cover 13, and a lower cover 14.The housing main body 11 is formed into a stepped cylindrical shape consisting of a large diameter part 11a and a small diameter part 11b, and the housing head 12 and A top cover 13 is airtightly assembled. Further, a lower cover 14 is attached to the lower end opening of the small diameter portion 11b of the housing body 11 and the protruding wall portion 11c, and a motor housing 41 of the electric motor 40 is attached to the outside of the protruding wall portion 11c. On the other hand, the large diameter part 11a and the small diameter part 1 in the housing body 11
Cylinder liners 15a and 15b are fitted to 1b, and first and second cylinder portions 16a and 16b are formed in both portions 11a and 11b.

The working piston 20 includes a piston body 21 and a connecting rod 22, and the piston body 21 is formed by a large-diameter first piston part 21a and a cylindrical second piston part 21b that is integrally provided therewith and extends downward. ing. In the piston body 21, an annular leaf spring 2 is provided in an annular recess provided on the outer periphery of the first piston part 21a and the second piston part 21b.
Seal rings 24a, 24 via 3a, 23b
b are fitted, and each of these piston parts 21
a, 21b can be slid in the axial direction in an airtight manner with respect to each cylinder portion 16a, 16b. The piston body 21 is connected to a crankshaft 23 via a connecting rod 22, and via the crankshaft 23 to an output shaft 42 of an electric motor 40, which will be described later. As a result, the operating piston 20 creates a negative pressure chamber between the disk 25 fitted to the first piston part 21a on the upper side of the first piston part 21a and the plate 17 fitted to the housing head 12 on the lower side of the housing head 12. It forms R1. Further, the actuating piston 20 is connected to the first cylinder portion 1
A pressure chamber R2 is formed within 6a between the first piston portion 21a and the second piston portion 21b.

The suction check valve 31 is composed of a rubber mushroom-shaped valve body, and is attached to the housing head 1.
The umbrella part is fitted into the center part of the head 12.
The suction boat 12a provided in the head 12 facing the space R3 between the plate 17 is opened and closed. The suction boat 12a communicates with a suction passage 13a provided in the top cover 13 through an air filter 18 fitted to the top cover 13. In addition, the suction passage 13
A is in communication with a vacuum tank or the like that supplies negative pressure to the vacuum booster. In addition, the space R3
communicates with the negative pressure chamber R1 through a communication port provided in the plate 17.

The first discharge check valve 32 is constituted by an annular flat plate valve body made of rubber, and is interposed between a disk 25 and a plate 26 fitted on the upper surface side of the first piston portion 21a. As shown in FIG. 3, the disk 25 has an annular recess 25a formed in its lower surface that expands downward, and a through hole 25b that opens into the top of the recess 25a and into the negative pressure chamber R1.
is formed. Further, the plate 26 has a mountain-shaped top facing the recess 25a of the disk 25, and the plate 26 has a recess 25a and a first
Groove portion 21 shown in FIG. 4 provided in piston portion 21a
Through holes 26a and 26b are formed which open to c. The groove portion 21c is connected to the pressure chamber R through the through hole 21d.
2, the through hole 25b and recess 25a of the disk 25, and the through holes 26a and 2 of the plate 26.
6b, the groove 21c of the first piston portion 21a, and the through hole 21d form a communication path that communicates the negative pressure chamber R1 and the pressure chamber R2. The first discharge check valve 32 is fitted into the recess 25a of the disk 25 and faces the through hole 25b, and is attached to and removed from the top periphery of the recess 25a to open and close the through hole 25b.

As shown in FIG. 2, the second discharge check valve 33 is composed of a valve body 33a, a compression spring 33b, and a retainer 33c, and is interposed in a discharge passage 11d provided on the side of the housing body 11. , a through hole 1 provided in the discharge passage 11d
Open and close 1e. The discharge passage 11d communicates the pressure chamber R2 with the atmospheric chamber R4 below the piston body 21, and discharges the air in the pressure chamber R2 to the atmosphere through the atmospheric chamber R4 and the air filter 18b.

The electric motor 40 is a known micromotor, and its output shaft 42 is rotatably supported by the protruding wall portion 11c of the housing body 11.
It is coming within 4 days. The output shaft 42 is screwed onto the crankshaft 23 at its tip and connected to the conrod 22.
The actuating piston 20 is connected to and rotated by the drive of a motor to repeatedly slide the actuating piston 20 in the vertical direction.

In the vacuum pump configured in this way, when the working piston 20 slides upward, the suction check valve 31 and the second discharge check valve 33 close, and the first discharge check valve 32 opens, and the working piston On the contrary, when the pump 20 slides downward, the suction check valve 31 and the second discharge check valve 33 open, and the first discharge check valve 32 closes, and the P-V diagram in the negative pressure chamber R1 changes. The state shown in FIG. 5a is reached. That is, 1a in the figure is a state in which the working piston 20 is located at the top dead center, and as the working piston 20 descends, the negative pressure chamber R1 expands (expansion stroke 1a-2a). As the expansion stroke progresses and in state 2a, the pressure in the negative pressure chamber R1 becomes equal to the pressure on the suction passage 13a side, the suction check valve 31 opens, and air from the passage 13a side is sucked into the negative pressure chamber R1 (suction stroke 2a-3a). The suction stroke is the working piston 2
0 reaches the bottom dead center and the operating piston 20 moves upward from the state 3a to open the suction check valve 3.
1 closes and compression of the negative pressure chamber R1 begins (compression stroke
3a−4a). As the compression stroke progresses and in state 4a, the negative pressure chamber R
1 becomes equal to the pressure on the pressure chamber R2 side, and the pressure in the first
The discharge check valve 32 opens and the air in the negative pressure chamber R1 is exhausted (exhaust stroke 4a-1a). on the other hand,
In the pressure chamber R2, as shown in FIG. 5b, when the working piston 20 is located at the top dead center, the suction stroke (2b-3b) is in the end state 3b,
1 expansion stroke (1a-2a), suction stroke (2a-3a),
Compression stroke (3a-4a) and exhaust stroke (4a-1a)
Corresponding to the compression stroke (3b-4b) and exhaust stroke (4b-
1b), expansion stroke (1b−2b) and suction stroke (2b−
3b).

As is clear from this comparison, when the negative pressure chamber R1 is in the exhaust stroke (4a-1a), the pressure chamber R2 is in the suction stroke (2b-3b), and the discharge of the first discharge check valve 32 is Side pressure (pressure chamber R2
internal pressure) becomes negative pressure. Therefore, the pressure on the discharge side of the check valve 32 is extremely low compared to the conventional one, and the degree of vacuum achieved in the negative pressure chamber R1 and the evacuation speed are significantly improved. In addition, the check valve 31 for suction
The first discharge check valve 32 performs its original function without any loss in function.

In addition, in the vacuum pump, positive pressure and negative pressure are actively generated in the pressure chamber R2 to increase the differential pressure between the pressure chamber R2 and the negative pressure chamber R1, and only by the action of this differential pressure, the first Discharge check valve 32
is configured to open and close. For this reason,
Unlike the case where the first discharge check valve 32 uses the biasing force of a compression spring, it can be opened and closed at the appropriate timing according to the state of the negative pressure chamber regardless of the sliding speed of the working piston 20. This allows the set pump performance to be fully demonstrated. In addition, the same check valve 32
Since the valve does not use a mushroom-shaped valve body, it goes without saying that there are no problems caused by valves made of the mushroom-shaped valve body.

Furthermore, in this vacuum pump, the pressure in the pressure chamber R2 is applied to the center of the lower part of the check valve 32 through the hole 21d, the groove 21c, and the hole 26a when the working piston 20 is lowered. It acts from the lower center of the valve 32 to the outer periphery to ensure closure by the valve 32.

In addition, in the above embodiment, the first piston portion 21
The groove portion 21c provided in section a can be changed to an annular recess 21e as shown in FIGS. 6a and 6b.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a vacuum pump according to an embodiment of the present invention, FIG. 2 is a partially cutaway side view of the vacuum pump, and FIG. 3 is an enlarged longitudinal sectional view of a first piston part. Figure 4 is a plan view with the same parts omitted; Figures 5a and b are PV diagrams of the negative pressure chamber and pressure chamber;
FIGS. 6a and 6b are a partial vertical sectional view and a plan view showing a modification of the first piston portion. Explanation of symbols, 10... Pump housing, 16
a, 16b...Cylinder part, 20...Working piston, 21a, 21b...Piston part, 22...Conrod, 31...Inhalation check valve, 3
2, 33...Discharge check valve, 40...Electric motor, R1...Negative pressure chamber, R2...Pressure chamber.

Claims (1)

[Scope of utility model registration request] The piston part of the working piston is fitted airtightly and slidably in the axial direction into the cylinder part provided inside the pump housing, and a suction check valve and a discharge check valve are provided on one side of the piston part to generate negative pressure. The rod portion of the actuating piston is connected to a pump drive shaft, and the rotation of the drive shaft causes the actuating piston to slide, and the negative pressure generated in the negative pressure chamber is transferred to the negative pressure actuator. In the piston sliding type vacuum pump, a second cylinder is provided inside the pump housing and is coaxial with the cylinder part and has a diameter different from that of the cylinder part.
a second piston portion that is fitted into the second cylinder portion airtightly and slidably in the axial direction;
A pressure chamber is formed between these two piston parts, and the pressure chamber is communicated with the atmosphere via a second discharge check valve, while the piston part is provided with a connection which communicates the negative pressure chamber and the pressure chamber. A piston sliding vacuum pump characterized in that a passage is provided and a flat valve is used as the discharge check valve, and the valve is interposed in the communication passage.