Vacuum pump

Abstract

To provide a vacuum pump capable of preventing malfunction of a check valve after low-temperature soaking.SOLUTION: A vacuum pump (1) includes: a pump chamber (10) in which a negative pressure is generated; an intake passage (28) configured to guide intake air to the pump chamber (10) through an intake port (30) which is open in the pump chamber (10); and a check valve (32) which prevents reverse flow of the intake air in the intake passage (28). The check valve (32) includes: a valve chamber (34) provided at the intake passage (28); a valve seat (36) formed at a peripheral edge of an inlet opening (34a) of intake air in the valve chamber (34); a valve body (38) which separates from and contacts with the valve seat (36) in the valve chamber (34) to open or close the check valve (32); and a coil spring (40) which presses and biases the valve body (38) to the valve seat (36) in the valve chamber (34). An inner peripheral surface (34c) of the valve chamber (34) and the valve seat (36) are covered with a water repellent coat (50).SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a vacuum pump, and more particularly to a vacuum pump used for evacuating a negative pressure chamber such as a brake booster provided in a vehicle such as an automobile.

Background Art

[0002] Conventionally, a vacuum pump has been used to evacuate the negative pressure chamber of a brake booster provided in a vehicle such as an automobile. The vacuum pump described in Patent Document 1 includes a pump chamber that generates a negative pressure, an intake passage that guides intake air into the pump chamber through an intake port opened in the pump chamber, and a check valve that prevents backflow of the intake air in the intake passage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, moisture contained in the intake air may condense into water droplets in the check valve of the vacuum pump and adhere to the valve body or the periphery of the valve seat of the check valve. The water droplets adhering to the periphery of the valve body or the valve seat freeze after the engine of the vehicle stops and a cold soak (being exposed to a low-temperature environment for a long time) occurs. Freezing of the water droplets may cause the valve body to stick to the valve seat, leading to malfunction (such as slow operation or inability to operate) of the check valve.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a vacuum pump capable of preventing malfunction of the check valve after a cold soak.

Means for Solving the Problems

[0006] To achieve the above object, the vacuum pump of the present invention includes a pump chamber that generates a negative pressure, an intake passage that guides intake air into the pump chamber through an intake port opened in the pump chamber, and a check valve that prevents the backflow of intake air in the intake passage. The check valve has a valve chamber provided in the intake passage, a valve seat formed at the periphery of the intake opening in the valve chamber, a valve body that opens and closes the check valve by coming into contact with and separating from the valve seat in the valve chamber, and a coil spring that presses and biases the valve body toward the valve seat in the valve chamber. The inner peripheral surface of the valve chamber and the valve seat are covered with a water-repellent film.

Advantages of the Invention

[0007] Therefore, according to the vacuum pump of the present invention, it is possible to prevent the malfunction of the check valve after the low-temperature soak.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the vacuum pump 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a perspective view of the vacuum pump 1 as viewed from the front side, and FIG. 2 shows a perspective view of the vacuum pump 1 as viewed from the back side. The vacuum pump 1 includes a bottomed cylindrical housing 2 and a disk-shaped cover 4 that closes the housing 2. An inflated portion 4a with a bulging outer surface is formed on the cover 4. A protruding portion 4b that protrudes to the outer peripheral side of the cover 4 is formed on the inflated portion 4a, and an intake connection member 6 is connected to the protruding portion 4b. The intake connection member 6 is connected to a brake booster (not shown) provided in a vehicle such as an automobile. The housing 2 and the cover 4 are hermetically joined by bolts 8 via an O-ring (not shown).

[0010] FIG. 3 shows a front view of the vacuum pump 1 with the cover 4 transparent and the intake connection member 6 in cross section. A pump chamber 10 having a substantially circular shape in plan view is formed inside the housing 2, and a cylindrical rotor 12 is disposed at a position eccentric with respect to the center of the circle of the pump chamber 10. The rotor 12 is arranged such that its outer peripheral surface 12a is in contact with the inner peripheral surface 2a of the housing 2.

[0011] The rotor 12 is rotationally driven in the direction of the arrow by a drive shaft 14 (also shown in FIG. 2). The drive shaft 14 is connected to a rotating body of a drive source provided outside the vacuum pump 1 via a coupling 16 (see FIG. 2) and is rotationally driven by the rotating body. The rotating body is, for example, an engine shaft or a motor shaft. Further, a plate-shaped vane 18 is attached to the rotor 12 so as to cross along its diameter direction.

[0012] The vane 18 is movable in the diametrical direction of the rotor 12, and tip portions 18a that are in sliding contact with the inner peripheral surface 2a of the housing 2 are attached to both ends of the vane 18. Further, the drive shaft 14 is pivotally supported by a cylindrical bearing portion 20 formed in the housing 2, and an exhaust passage 22 opens into the pump chamber 10. An approximately arc-shaped discharge port (not shown) that communicates with the exhaust passage 22 is covered in an openable and closable manner by a reed valve 26 (see FIG. 2) on the end surface of the bearing portion 20. When the reed valve 26 is opened, the exhaust gas in the pump chamber 10 is discharged from the discharge port through the exhaust passage 22.

[0013] FIG. 4 shows a front view of the vacuum pump 1 with the bulging portion 4a, the protruding portion 4b of the cover 4, and the intake connection member 6 in cross section. An intake passage 28 is formed in the bulging portion 4a of the cover 4 and the intake connection member 6. Intake air flows in the direction of the arrow shown in FIG. 4 through the intake passage 28. An intake port 30 that communicates the intake passage 28 with the pump chamber 10 is provided near the downstream end of the intake passage 28 formed in the bulging portion 4a of the cover 4. The inner diameter of the intake passage 28 in the bulging portion 4a gradually decreases from the protruding portion 4b side toward the intake port 30 side.

[0014] The housing 2 is provided with an oil supply hole (not shown), and this oil supply hole opens to the inner peripheral surface of the bearing portion 20 and the outer peripheral surface of the housing 2. A predetermined gap is provided between the bearing portion 20 and the drive shaft 14, and lubricating oil is supplied from the oil supply hole to this gap, and further, lubricating oil is supplied from this gap into the pump chamber 10. A check valve 32 is disposed inside the intake connection member 6, and the check valve 32 mainly prevents the backflow of lubricating oil from the pump chamber 10 to the brake booster in the intake passage 28, and also prevents the backflow of intake air.

[0015] Figures 5(a) to (h) show the operation of the vacuum pump 1 step by step. In each of these figures, the cover 4 and the intake connection member 6 are not shown. In the vacuum pump 1 configured as described above, as the rotor 12 rotates in the direction of the arrow shown in Fig. 5(a), the vane 18 also rotates, and the tip portions 18a of the vane 18 are in sliding contact with the inner peripheral surface 2a of the housing 2. As a result, the inside of the pump chamber 10 is partitioned by the vane 18 into a space on the intake port 30 side and a space on the exhaust passage 22 side.

[0016] Also, as the rotor 12 rotates at an eccentric position in the pump chamber 10, the vane 18 rotates while moving in the diametrical direction of the rotor 12. Then, as shown in Figs. 5(a) to (d), the space (shown in gray scale) on the intake port 30 side in the pump chamber 10 is expanded in volume due to the movement and rotation of the vane 18, so that the air in the negative pressure chamber of the brake booster is sucked, and is introduced as intake air into the pump chamber 10 through the intake port 30 of the intake passage 28.

[0017] Next, as the vane 18 further moves and rotates, the vane 18 temporarily closes the intake port 30 in the process of transitioning from Fig. 5(d) to (e). As a result, the suction of the negative pressure chamber of the brake booster is temporarily stopped. Next, as the vane 18 further moves and rotates, as shown in Fig. 5(e), the space on the intake port 30 side in the pump chamber 10 moves to the exhaust passage 22 side.

[0018] Then, as shown in Figs. 5(f) to (h), as the vane 18 further moves and rotates, the intake air sucked from the negative pressure chamber of the brake booster into the pump chamber 10 is discharged as exhaust through the discharge port through the exhaust passage 22. By repeatedly executing the above process as the rotor 12 rotates, the negative pressure chamber of the brake booster is depressurized to a desired negative pressure.

[0019] FIG. 6 shows an enlarged view of the check valve 32. The check valve 32 shown in FIG. 6 is in an open valve state and is built into the intake connection member 6 at the protruding portion 4b of the bulging portion 4a. The check valve 32 includes a valve chamber 34, a valve seat 36, a valve body 38, a coil spring 40, and a cap 42. The valve chamber 34 is formed in a cylindrical shape with an axis in the extending direction of the intake passage 28 and has a larger diameter than the intake passage 28. The valve seat 36 is formed at the periphery of the inlet opening 34a that serves as the intake inlet in the valve chamber 34. Specifically, it is formed on an annular stepped surface formed between the intake passage 28 and the valve chamber 34.

[0020] The valve body 38 opens and closes the check valve 32 by separating from and contacting the valve seat 36 in the valve chamber 34. Specifically, the valve body 38 is composed of a seat portion 44 that separates from and contacts the valve seat 36 and a spring locking portion 46 to which the upper end (one end) of the coil spring 40 is locked. The seat portion 44 has a larger diameter than the intake passage 28 and a smaller diameter than the valve chamber 34. The spring locking portion 46 has a smaller diameter than the seat portion 44 and protrudes toward the outlet opening 34b that is the intake outlet in the valve chamber 34.

[0021] The coil spring 40 presses and biases the valve body 38 toward the valve seat 36 in the valve chamber 34. Specifically, the coil spring 40 is formed in a conical shape with a gradually decreasing diameter from the outlet opening 34b toward the inlet opening 34a. The cap 42 is fixed by caulking or the like over the entire circumference of the opening edge of the outlet opening 34b, the lower end (the other end) of the coil spring 40 is locked, it has a shape that protrudes toward the inlet opening 34a, and has a plurality of ventilation holes 48 through which the intake air passes.

[0022] In the check valve 32 configured as described above, when the volume of the space on the intake port 30 side in the pump chamber 10 is expanded, the negative pressure in the space separates the valve body 38 from the valve seat 36 against the pressing force of the coil spring 40. As a result, as shown by the arrow in FIG. 6, the intake air passes through the space between the valve body 38 and the valve seat 36, between the valve body 38 and the inner peripheral surface 34c of the valve chamber 34, and the ventilation holes 48 of the cap 42 in the valve chamber 34 in sequence, and is guided to the pump chamber 10 through the intake port 30 of the intake passage 28.

[0023] FIG. 7 shows a view clarifying the formation location of the water-repellent film 50 on the check valve 32 in FIG. 6. In the vacuum pump 1 of the present embodiment, the inner peripheral surface 34c of the valve chamber 34 and the valve seat 36 of the check valve 32 are covered with the water-repellent film 50. Further, more preferably, the inlet region 28a of the intake passage 28 close to the inlet opening 34a of the valve chamber 34 is also covered with the water-repellent film 50 over a predetermined range from the inlet opening 34a.

[0024] The water-repellent film 50 is formed of, for example, a fluororesin, and more specifically, is formed of fluorine-containing nickel plating or the like. When the water-repellent film 50 is fluorine-containing nickel plating, a base material in which a fluororesin is dispersed in nickel is coated on the inner peripheral surface 34c of the valve chamber 34, the valve seat 36, and the inlet region 28a. The water-repellent property of the water-repellent film 50 is not limited to the above-described fluororesin or fluorine-containing nickel plating as long as it can make the adhering water droplets 52 into spherical shapes with a small diameter and can reduce the fixing force of the valve body 38 to the valve seat 36 when frozen, and various configurations can be applied.

[0025] As described above, the vacuum pump 1 of the present embodiment can enhance the drainage (water flowability) of these locations by forming the water-repellent film 50 on the inner peripheral surface 34c of the valve chamber 34, the valve seat 36, and the inlet region 28a, and thus can reduce the amount of moisture adhering to these locations. As shown in FIG. 7, the water droplets 52 adhering to the corresponding locations and the vicinity of the corresponding locations become spherical with a small diameter.

[0026] On the other hand, FIG. 8 shows an enlarged view of a conventional check valve 32 without the water-repellent film 50 formed. In this case, since the moisture adhering to the inner peripheral surface 34c of the valve chamber 34, the valve seat 36, and the inlet region 28a is more than that in the case shown in FIG. 7, as shown in FIG. 8, the volume and surface area of each water droplet 52 become larger. When such water droplets 52 freeze after low-temperature soaking, the fixing force of the valve body 38 to the valve seat 36 increases, and it becomes difficult to operate the valve body against the fixing force, increasing the possibility of malfunction of the check valve 32.

[0027] Thus, in this embodiment, the water-repellent film 50 is formed on the inner peripheral surface 34c of the valve chamber 34, the valve seat 36, and the inlet region 28a. By enhancing the drainage properties of these locations, the water droplets 52 adhering to these locations can be made into spherical shapes with a small diameter, and the adhesion force of the valve body 38 to the valve seat 36 when frozen can be significantly reduced. Therefore, since the valve body 38 can easily operate against the adhesion force, it is possible to prevent malfunction of the check valve 32 after low-temperature soak.

[0028] Further, the valve body 38 is composed of a seat portion 44 that contacts and separates from the valve seat 36, and a spring locking portion 46 to which one end of the coil spring 40 is locked. Thereby, when the check valve 32 is closed, the valve body 38 only contacts the valve seat 36, and a part of the valve body 38 does not reach the inlet region 28a of the intake passage 28 beyond the inlet opening 34a as in the prior art. Therefore, since the contact area between the valve body 38 and the intake passage 28 can be reduced compared to the prior art, the risk of the valve body 38 sticking due to freezing of the water droplets 52 can be further reduced.

[0029] Further, the check valve 32 is fixed to the outlet opening 34b of the valve chamber 34 and has a cap 42 to which the lower end of the coil spring 40 is locked. The cap 42 has a shape that protrudes toward the inlet opening 34a and has a plurality of ventilation holes 48 through which intake air passes. By forming each ventilation hole 48 in a mesh shape in the cap 42 in this way, the water droplets 52 that have avoided adhesion in the water-repellent film 50 are efficiently discharged to the lower side of the check valve 32 together with the intake air passing through each ventilation hole 48 and are sucked out from each ventilation hole 48. Therefore, the drainage property of the check valve 32 can be further enhanced, and thus malfunction of the check valve 32 can be more reliably prevented.

[0030] With the above description, the explanation of one embodiment of the present invention is completed. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the water-repellent film 50 formed in the inlet region 28a of the intake passage 28 is formed in a predetermined range that is extremely narrow, for example, a width of about 0.3 mm. Therefore, the water-repellent film 50 may be formed at least on the inner peripheral surface 34c of the valve chamber 34 and the valve seat 36.

Explanation of Reference Numerals

[0031] 1 Vacuum pump 10 Pump chamber 28 Intake passage 28a Inlet region 30 Intake port 32 Check valve 34 Valve chamber 34a Inlet opening 34b Outlet opening 34c Inner peripheral surface 36 Valve seat 38 Valve body 40 Coil spring 42 Cap 44 Sheet portion 46 Spring locking portion 48 Vent hole 50 Water-repellent film

Claims

1. a pump chamber that generates negative pressure, an intake passage that guides intake air into the pump chamber through an intake port opened to the pump chamber, a check valve that prevents backflow of the intake air in the intake passage and comprising, the check valve, a valve chamber provided in the intake passage, a valve seat formed at the periphery of the inlet opening of the intake air in the valve chamber, a valve body that opens and closes the check valve by contacting and separating from the valve seat in the valve chamber, and a coil spring that presses and biases the valve body toward the valve seat in the valve chamber and having, a vacuum pump in which the inner peripheral surface of the valve chamber and the valve seat are covered with a water-repellent film.

2. The inlet region of the intake passage close to the inlet opening of the intake air in the valve chamber is covered with the water-repellent film over a predetermined range. The vacuum pump according to claim 1.

3. The valve chamber is formed in a cylindrical shape having an axis in the extending direction of the intake passage, the valve body, has a diameter larger than that of the intake passage and a diameter smaller than that of the valve chamber, and has a seat portion that contacts and separates from the valve seat, has a diameter smaller than that of the seat portion and protrudes toward the outlet opening of the intake air in the valve chamber, and a spring locking portion to which one end of the coil spring is locked The vacuum pump according to claim 2, which is composed of.

4. The check valve has a cap that is fixed to the outlet opening and to which the other end of the coil spring is locked, The cap has a shape that protrudes toward the inlet opening and has a plurality of ventilation holes through which the intake air passes. The vacuum pump according to claim 3.

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