Vane gas pump

Description

[0001] The invention relates to a vane cell gas pump.

[0002] Such vane-cell gas pumps are known from the prior art and are used in motor vehicles as so-called vacuum pumps, typically in combination with a brake booster. The vane-cell pump supplies the vacuum pressure required to operate the brake booster, which is usually 100 mbar or less absolute.

[0003] The vane gas pumps known from the prior art, for example from US 3,320,899 A or WO 2016 / 104 652 A1, are usually dry-running or oil-lubricated vane gas pumps, whereby in dry-running gas pumps no lubricant is fed into the pumping chamber. In oil-lubricated vane pumps, the air escaping from the pumping chamber is mixed with lubricant, and before this air-lubricant mixture can be disposed of, the air-lubricant mixture must be laboriously separated into its components. By omitting the lubricant, contamination of the air leaving the pumping chamber can be avoided. However, omitting the lubricant leads to increased wear on the components that move relative to one another, in particular the slide elements.Wear is usually reduced to a minimum by carefully selecting suitable material pairings for the components that are adjacent to one another and move relative to one another.

[0004] A dry-running vane cell gas pump is disclosed in EP 2 568 180 A1. The vane cell gas pump has a pump housing that forms a pump chamber. A pump rotor is arranged in the pump chamber and has five radially displaceable slide elements. The pump rotor is connected to an electric motor in a rotationally fixed manner and is driven by the latter. When the pump rotor rotates, the slide elements move due to the centrifugal force acting on the slide elements such that their heads each rest against a peripheral wall of the pump chamber. Two adjacent slide elements, together with the pump rotor and the pump housing, each delimit a circumferential pump compartment. Formed in the pump housing are one fluid inlet opening assigned to the pump chamber and two fluid outlet openings assigned to the pump chamber, wherein the fluid outlet openings have a circular opening cross-section.

[0005] A disadvantage of the design disclosed in EP 2 568 180 A1 is that the opening cross-sections of the circular fluid outlet openings must have a certain size to ensure low flow resistance. However, this results in a brief short circuit between two adjacent pump compartments when the respective slide element passes the fluid outlet opening. Such a short circuit leads to increased leakage at the individual slide elements, which reduces the pneumatic efficiency of the vane cell gas pump. Making the fluid outlet opening smaller increases the flow resistance, resulting in overpressure in the pump compartments in the outlet area at high speeds. This places additional mechanical stress on the slide elements and increases wear on the slide elements.

[0006] JP S62 247194 A discloses an air conditioning compressor with multiple fluid outlet openings in the outlet area, some of which are designed as elongated holes. Check valves are associated with all four fluid outlet openings.

[0007] The invention is therefore based on the object of creating a vane cell gas pump with low wear of the slide elements and a good pneumatic efficiency.

[0008] This task is solved by a vane cell gas pump with the features of the main claim.

[0009] The vane cell gas pump according to the invention comprises a pump housing defining a pump chamber. A pump rotor is arranged in the pump chamber, which is driven either electrically by an associated electric motor or mechanically by an internal combustion engine. The pump rotor is arranged eccentrically in the pump chamber and, together with the peripheral wall of the pump chamber, forms a sealing gap defining the sealing sector, thereby defining a crescent-shaped working space outside the sealing sector.

[0010] At least one displaceable slide element is mounted in the pump rotor. To support the at least one slide element, the pump rotor has a slide slot in which the at least one slide element is displaceably mounted and arranged. In a rotating pump rotor, the at least one slide element moves due to the centrifugal force acting on the slide element such that the slide element's head always rests against the peripheral wall of the pump chamber. In addition, the at least one slide element can be spring-loaded so that the head of the at least one slide element rests against the peripheral wall of the pump chamber due to the spring force, even at low speeds.

[0011] The pump chamber is functionally divided into an inlet, an outlet, and a sealing sector. At least one fluid inlet opening is arranged in the inlet sector, which, when the gas pump is installed, is fluidically connected, for example, to a vacuum chamber of a brake booster. At least one fluid outlet opening is arranged in the outlet sector, wherein the pump chamber is connected to the atmospheric environment via the fluid outlet opening. Viewed in the direction of rotation, the sealing sector is arranged between the fluid outlet opening and the fluid inlet opening, in which the pump rotor lies so tightly against the pump housing that no gas flow is possible between the fluid inlet opening and the fluid outlet opening.

[0012] The at least one fluid outlet opening is designed in the shape of a slot. The tangential width of the slide element corresponds at least to the tangential width of the slot-like fluid outlet opening, wherein the slot-like fluid outlet opening is oriented such that the entire fluid outlet opening is briefly covered and closed by the slide element. The tangential width of the slide element refers to the transverse direction to the linear movement path of the slide element. The tangential width of the slot-like fluid outlet opening is oriented perpendicular to the displacement direction of the slide element in the slide slot, specifically at the moment when the slide element centrally covers the fluid outlet opening.In the rotor position, in which the fluid outlet opening is temporarily and briefly completely closed by the slide element, the longitudinal axis of the slot-like fluid outlet opening and the longitudinal axis of the slide element have a common alignment or overlap.

[0013] During operation, air is sucked into the passing pump compartment via the fluid inlet opening and then expelled from the pump compartment via the at least one fluid outlet opening. Because the at least one fluid outlet opening is designed like an elongated hole, the flow cross-section of the fluid outlet opening is so large that the air can flow out of the pump compartment with virtually no resistance, even at high speeds, so that the slide element is not subjected to any additional mechanical stress. A fluid short circuit is also prevented because the at least one slide element briefly completely covers and fluidically closes the at least one fluid outlet opening. In this way, wear on the slide elements is reduced, while the pneumatic efficiency of the vane cell gas pump is good.

[0014] The pump chamber is provided with a first fluid outlet opening and a second fluid outlet opening in the direction of rotation, with at least the first fluid outlet opening being designed as an elongated hole. This allows a larger amount of gas to be expelled from the pump compartment without resistance.

[0015] Preferably, the tangential width of the at least one slide element is slightly larger, preferably at least a few tenths of a millimeter larger, than the tangential width of the at least one fluid outlet opening, wherein the fluid outlet opening is covered by the at least one slide element when overlapping. In this way, a short circuit between two adjacent pump compartments is reliably prevented and wear of the at least one slide element is reduced to a minimum.

[0016] In a preferred embodiment, the at least one slot-like fluid outlet opening has a constant tangential width in its central section along its length. The two end regions of the slot-like fluid outlet opening can be rounded or beveled. Alternatively, the fluid outlet opening can be designed, for example, such that the tangential width of the fluid outlet opening decreases in the radial direction toward the motor rotor.

[0017] The pump housing preferably has a valve cover, a cam ring, and a base cover. The cam ring forms the circumferential surface of the pumping chamber and rests with one end face against the valve cover and with its other end face against the base cover in a sealing manner. The valve cover closes off the pumping chamber on one side. Preferably, the valve cover has the at least one fluid outlet opening, and the base element has the fluid inlet opening. A check valve is preferably arranged on the valve cover, which closes the at least one fluid outlet opening and opens the fluid outlet opening when an opening pressure prevails in the pumping compartment.

[0018] Preferably, the length L of the at least one slot-like fluid outlet opening corresponds to the free working space width W in the longitudinal direction of the slide element, wherein the working space width W extends from the outer circumferential surface of the pump rotor to the inner circumference of the pump chamber defined by the cam ring.

[0019] The invention is explained in more detail with reference to the drawings, in which: the Figure 1 an exploded view of a vane cell gas pump, and the Figure 2 a top view of a pump rotor of the vane cell gas pump from Figure 1 .

[0020] The Figure 1 and 2show a vane gas pump 10 designed as a so-called vacuum pump, which is intended, for example, for use in a motor vehicle and can generate an absolute pressure of 100 mbar or less. The dry-running vane pump 10 has a metal pump housing 20 enclosing a pump chamber 22. The pump housing 20 is essentially composed of a cam ring 74, a base plate 76, and a valve cover 72.

[0021] A pump rotor 30 is rotatably arranged in the pump chamber 22, eccentrically to the center of gravity of the pump chamber 22. The pump rotor 30 has five slide slots 321, 341, 361, 381, 401, in each of which a slide element 32, 34, 36, 38, 40 is displaceably mounted. The five slide elements 32, 34, 36, 38, 40 divide the pump chamber 22 into five rotating pump compartments, each of which has the same pump compartment angle α of approximately 70°. The pump rotor 30 is driven by an associated electric motor 90.

[0022] The present vane gas pump 10 is a dry-running vane gas pump 10, whereby no lubricant, such as oil, is introduced into the pump chamber 22. Therefore, the gas pump 10 does not have a lubricant connection. To reduce friction and wear between the adjacent and relatively moving components of the vane gas pump 10, the slide elements 32, 34, 36, 38, and 40 contain graphite components. Alternatively, the components may have a different friction-reducing composition.

[0023] The pump chamber 22 can be divided into several sectors, namely an inlet sector 42 with a fluid inlet opening 60, an outlet sector 44 with a first fluid outlet opening 52 and a second fluid outlet opening 54, and a sealing sector 46, which is arranged between the outlet sector 44 and the inlet sector 42 as seen in the direction of rotation and in which a gas flow via the sealing gap between the pump rotor 30 and the cam ring 74 from the fluid outlet openings 52, 54 to the fluid inlet opening 60 is prevented.

[0024] The fluid inlet opening 60 is formed in the base plate 76. The two fluid outlet openings 52, 54 are formed in the opposite valve cover 72. The first fluid outlet opening 52 is arranged upstream of the second fluid outlet opening 54, as seen in the direction of rotation of the pump rotor 30. A check valve 70 is fluidically associated with the first fluid outlet opening 52. The check valve 70 is a reed valve and has a valve reed 80 and a travel limiter 82, both of which are fixedly arranged or screwed to the valve cover 72.

[0025] The first fluid outlet opening 52 is designed as an elongated hole. The tangential width B1 of the slide elements 32, 34, 36, 38, 40 corresponds at least to the tangential width B2 of the fluid outlet opening 52, wherein the elongated hole-like fluid outlet opening 52 is oriented such that the first fluid outlet opening 52 is completely covered by one of the slide elements 32, 34, 36, 38, 40 in predefined rotor positions and is thus briefly completely closed. In the rotor positions in which the fluid outlet opening 52 is briefly closed by a slide element 32, 34, 36, 38, 40, the longitudinal axis of the closed fluid outlet opening 52 and the longitudinal axis of the corresponding slide element 32, 34, 36, 38, 40 have a common, identical orientation.

[0026] During operation of the gas pump 10, the rotation of the pump rotor 30 draws air into the respective pump compartment through the fluid inlet opening 60 and expelled from the continuously rotating pump compartment through the two fluid outlet openings 52, 54. As long as a predefined overpressure prevails in the pump compartment, the first fluid outlet opening 52 is open, and the air is expelled through the first fluid outlet opening 52. Additionally, the air is expelled through the second fluid outlet opening 54 as soon as the respective pump compartment reaches it.

[0027] Because the first fluid outlet opening 52 is designed like an elongated hole, the flow area of the fluid outlet opening 52 is large enough to allow the air to flow out of the pump compartment with virtually no resistance, so that the slide elements 32, 34, 36, 38, 40 are not subjected to any additional mechanical stress in the tangential direction. A short circuit between two adjacent pump compartments is also prevented because the slide elements 32, 34, 36, 38, 40 temporarily completely cover and close the fluid outlet openings 52, 54. The backflow losses are therefore zero here. In this way, the wear on the slide elements 32, 34, 36, 38, 40 is reduced without reducing the pneumatic efficiency of the vane cell gas pump 10.

[0028] It should be clear that other structural embodiments of the dry-running gas pump are possible compared to the described embodiment without departing from the scope of the main claim. For example, the number of slide elements may vary, or the fluid inlet and / or outlet openings may be formed on other housing components.

Claims

1. Vane gas pump for a compressible fluid, comprising a pump housing (20) which forms a pump chamber (22) in which a pump rotor (30) having at least one displaceable slide element (32, 34, 36, 38, 40) is rotatably supported, wherein at least one fluid inlet opening (60) is associated with the pump chamber (22), a first elongated hole-like fluid outlet opening (52) and a second fluid outlet opening (54), which connect the pump chamber (22) to the atmospheric environment, are associated with the pump chamber (22) in an outlet sector in the direction of rotation, characterized in that the tangential width (B1) of the at least one slide element (32, 34, 36, 38, 40) corresponds at least to the tangential width (B2) of the first elongated hole-like fluid outlet opening (52) such that the at least one slide element (32, 34, 36, 38, 40) temporarily completely covers the first elongated hole-like fluid outlet opening (52), the longitudinal axis of the closed first elongated hole-like fluid outlet opening (52) and the longitudinal axis of the corresponding slide element (32, 34, 36, 38, 40) have a common identical orientation, a check valve (70) is fluidically associated with the first elongated hole-like fluid outlet opening (52), and no check valve is associated with the second fluid outlet opening (54).

2. Vane gas pump according to Claim 1, characterized in that the tangential width B1 of the at least one slide element (32, 34, 36, 38, 40) is slightly greater than the tangential width B2 of the first fluid outlet opening (52).

3. Vane gas pump according to claim 1 or 2, characterized in that the first elongated hole-like fluid outlet opening (52) has a constant tangential width B2 over its length.

4. Vane gas pump according to one of the preceding claims, characterized in that the pump housing (20) has a thrust washer (72), a lifting ring (74) and a base element (76) which define the pump chamber (22).

5. Vane gas pump according to claim 4, characterized in that the fluid inlet opening (60) is provided at the base element (76) and the first elongated hole-like fluid outlet opening (52) is provided at the thrust washer (72).

6. Vane gas pump according to one of the preceding claims, characterized in that the length L of the first elongated hole-like fluid outlet opening (52) corresponds to the free working space width W in the slide element longitudinal direction.