阅读说明：本技术 具有v型双活塞布置的用于乘用车上的制动器系统的电动真空泵 (Electric vacuum pump for a brake system on a passenger vehicle with a V-shaped double piston arrangement ) 是由 格林·戴奇 大卫·希普斯 于 2019-03-15 设计创作，主要内容包括：本发明涉及一种真空泵(1),包括：本体(2)；第一气缸(4),该第一气缸(4)至少部分地位于所述本体(2)内部,并且具有第一气缸轴线(A1)、第一活塞(8)和第一活塞杆(12),该第一活塞(8)在第一气缸(4)中往复运动,该第一活塞杆(12)附接到第一活塞(8)；第二气缸(6),该第二气缸(6)至少部分地位于所述本体(2)内部,并且具有第二气缸轴线(A2)、第二活塞(10)和第二活塞杆(14),该第二活塞(10)在第二气缸(6)中往复运动,该第二活塞杆(14)附接到第二活塞(10)。根据本发明,第一和第二气缸轴线(A1、A2)成90°布置；并且附接到所述本体(2)的电驱动马达(20)驱动公共曲柄销(30),其中,第一和第二活塞杆(12、14)接合所述公共曲柄销(30),以用于被所述公共曲柄销(30)共同驱动。(The invention relates to a vacuum pump (1) comprising: a body (2); a first cylinder (4), the first cylinder (4) being located at least partially inside the body (2) and having a first cylinder axis (A1), a first piston (8) and a first piston rod (12), the first piston (8) reciprocating in the first cylinder (4), the first piston rod (12) being attached to the first piston (8); a second cylinder (6), the second cylinder (6) being located at least partially inside the body (2) and having a second cylinder axis (A2), a second piston (10), the second piston (10) reciprocating in the second cylinder (6), and a second piston rod (14), the second piston rod (14) being attached to the second piston (10). According to the invention, the first and second cylinder axes (A1, A2) are arranged at 90 °; and an electric drive motor (20) attached to the body (2) drives a common crank pin (30), wherein the first and second piston rods (12, 14) engage the common crank pin (30) for being commonly driven by the common crank pin (30).)

1. A vacuum pump (1) comprising:

a body (2) of the utility model,

a first cylinder (4), the first cylinder (4) being located at least partially inside the body (2) and having a first cylinder axis (A1), a first piston (8) reciprocating in the first cylinder (4), and a first piston rod (12) attached to the first piston (8),

a second cylinder (6), said second cylinder (6) being located at least partially inside said body (2) and having a second cylinder axis (A2), a second piston (10) reciprocating in said second cylinder (6), and a second piston rod (14) attached to said second piston (10), wherein said first cylinder axis (A1) and said second cylinder axis (A2) are arranged at 90 ° to each other; and

an electric drive motor (20), the electric drive motor (20) being attached to the body (2) driving a common crank pin (30), wherein the first and second piston rods (12, 14) engage the common crank pin (30) for being commonly driven by the common crank pin (30).

2. Vacuum pump (1) according to claim 1, wherein the first piston (8) is rigidly attached to the first piston rod (12) and the second piston (10) is rigidly attached to the second piston rod (14).

3. Vacuum pump (1) according to claim 1 or 2, wherein the first cylinder axis (a1) and the second cylinder axis (a2) are in a common plane; and is

Wherein the first piston rod (12) is offset by a first piston offset distance (p1) from the first cylinder axis (A1) and from a center (C1) of the first piston (8), and

wherein the second piston rod (14) is offset by a second piston offset distance (p2) from the second cylinder axis (A2) and from a center (C2) of the second piston (10).

4. Vacuum pump (1) according to any of the preceding claims, comprising a first cylinder head (16) for enclosing the first cylinder (4) and a second cylinder head (18) for enclosing the second cylinder (6), wherein the first cylinder head (16) and the second cylinder head (18) are attached to the body (2).

5. Vacuum pump (1) according to claim 4, wherein the body (2) comprises a central inlet (22) for connecting the vacuum pump (1) to a consumer, and a first body duct (24) and a second body duct (26) in fluid communication with the central inlet (22), and

wherein the first cylinder head (16) comprises a first head conduit (25), the first head conduit (25) being in fluid communication with the first body conduit (24) and terminating in the first cylinder (4), and the second cylinder head (18) comprises a second head conduit (27), the second head conduit (27) being in fluid communication with the second body conduit (26) and terminating in the second cylinder (6).

6. Vacuum pump (1) according to claim 4 or 5, wherein the first cylinder head (16) comprises a first inlet valve (32) and the second cylinder head (18) comprises a second inlet valve (34).

7. Vacuum pump (1) according to any of the preceding claims, wherein the first piston (8) comprises a first piston seal (36), the first piston seal (36) being at the periphery (9) of the first piston (8) for sealing and guiding the first piston (8) within the first cylinder (4), and

wherein the second piston (10) comprises a second piston seal (38), the second piston seal (38) being at the periphery (11) of the second piston (10) for sealing and guiding the second piston (10) within the second cylinder (6).

8. Vacuum pump (1) according to any of the preceding claims, wherein the first piston (8) comprises a first outlet valve (40) and the second piston (10) comprises a second outlet valve (42).

9. Vacuum pump (1) according to claims 3 and 8, wherein the first outlet valve (40) is offset from the first cylinder axis (A1) by a first valve offset distance (v1) and the second outlet valve (42) is offset from the second cylinder axis (A2) by a second valve offset distance (v 2).

10. Vacuum pump (1) according to any of the preceding claims, wherein the body (2) comprises a central outlet (44) for discharging air.

11. Vacuum pump (1) according to any of the preceding claims, wherein the body (2) comprises a crankcase (3), the common crank pin (30) being cranked in the crankcase (3), wherein the crankcase (3) comprises a resonator volume (70), the resonator volume (70) being shaped to function as a Helmholtz resonator (72).

12. Vacuum pump (1) according to claim 12, wherein the crankcase (3) comprises an inlet (74), the inlet (74) opening into the resonator volume (70) such that the crankcase (3) acts as a helmholtz resonator (72).

13. Vacuum pump (1) according to claim 12 or 13, wherein the body (2) comprises a resonator insert (76) for at least partially confining the resonator volume (70).

14. Vacuum pump (1) according to any of the preceding claims, further comprising a first cylinder pipe (46) and a second cylinder pipe (48), the first cylinder pipe (46) defining the first cylinder (4) and the second cylinder pipe (48) defining the second cylinder (6).

15. Vacuum pump (1) according to claim 15, wherein the first cylinder tube (46) and the second cylinder tube (48) are located at least partially in the body (2) and/or in the first cylinder head (16) and the second cylinder head (18), respectively.

16. Vacuum pump (1) according to claim 15 or 16, wherein the body (2) and the first and second cylinder heads (16, 18) are formed of a plastic composite and the first and second cylinder pipes (46, 48) are formed of an aluminium material.

17. Vehicle, in particular passenger car, comprising a vacuum pump (1) according to any of the preceding claims.

Technical Field

The invention relates to a vacuum pump comprising: a body; a first cylinder located at least partially inside the body and having a first cylinder axis, a first piston reciprocating in the first cylinder, and a first piston rod attached to the first piston; a second cylinder located at least partially inside the body and having a second cylinder axis, a second piston reciprocating in the second cylinder, and a second piston rod attached to the second piston.

Background

Such vacuum pumps are used in particular for supplying pressure to brake actuators of motor vehicles having pneumatic brake booster systems. To provide vacuum for the pneumatic brake booster, a vacuum pump is used to draw residual air from the vacuum chamber and out to the atmosphere. For this reason, in the automotive industry, vane pumps or oscillating vane pumps are commonly used. A similar vane pump is disclosed, for example, in WO2007/141511a 1. Such vane pumps are also referred to as single vane pumps because they comprise a single vane which is slidable in the radial direction of the rotor. Such single vane pumps have inherent friction and must be lubricated to achieve an acceptable service life. These types of pumps are typically driven by the internal combustion engine of the motor vehicle and are connected to the oil circuit of the engine. These pumps draw some of the generated power from the engine when driving the vacuum pump and are typically rigidly connected and therefore continue to operate while the engine is running. They are independent of the vacuum requirements of the brake system, so it is useful to operate the vacuum pump using electrical energy independent of the internal combustion engine to run and generate vacuum only when the brake booster system is required, which has the advantage of saving emissions and fuel consumption of a vehicle having an internal combustion engine.

Furthermore, in motor vehicles with electric or hybrid drive trains, the vacuum pump cannot be driven continuously by the internal combustion engine; therefore, electric vacuum pumps are used for these vehicles. Another alternative is a fully integrated non-vacuum brake system, however, the cost penalty (cost penalty) of such a system is such that the market space for low cost vacuum systems is still associated with these types of motor vehicles. In addition to this, other vacuum operated systems are still possible to use on board the vehicle and to connect directly into (plumbed intro) electrically operated vacuum sources (pumps).

The electric pump, which is operated independently of the internal combustion engine, therefore has no lubricating oil circuit to which it is connected. Therefore, an electric pump for a brake system requires a dry pump or a dry pump. To equip such pumps, there are various versions. The use of self-lubricating graphite materials in the form of multi-vane dry pumps requires great precision and expense. Examples of multi-vane dry pumps for automotive applications are known from WO2017/067819a 1.

Other dry pumps exist that are either diaphragm pumps or piston pumps without lubrication. A diaphragm pump for automotive applications, a motor pump unit for providing pressure to a brake actuation device, is known from WO2010/069963a 1. The diaphragm pump generates pressure, pressurizes the fluid with a reciprocating flexible diaphragm, and due to this flexibility, it is still difficult to control the tolerances and dead volume of the working space above the piston in the pump. The volume above the working surface that retains uncompressed fluid becomes dead volume, resulting in reduced vacuum system performance.

Other dry piston pumps available are typically of the multi-piston 180 degree opposed type, either the linear articulated piston type or the oscillating non-articulated type. A double opposed piston pump is known from WO2011/054189a 1. Disadvantages of this pump arrangement are the cost and complexity of the crank arrangement and the difficulty of assembly and offset forces from the opposing crank pins.

Multiple piston type linear reciprocating piston pumps are suitable for this application but are expensive because the separate pistons and connecting rods must be provided with journal bearings at the large and small ends of the connecting rods.

Automotive vacuum pumps require multiple pistons to provide working fluid volume to meet the performance requirements of the individual vacuum systems on the vehicle. A single piston pump may not achieve the desired performance unless the pump is sufficiently capable of operation, resulting in unacceptable Noise Vibration and Harshness (NVH) from the pump. To reduce NVH of a single piston pump requires an unacceptable cost element of additional balance components. GB2263139 describes a single piston vacuum pump.

Therefore, efforts are being made to utilize multiple piston pumps that provide the benefits of NVH, providing an independent electrically powered vacuum source for the brake system as a low cost system.

The automotive industry places high demands on the acoustic comfort of motor vehicle components and requires their suppliers to provide robust and low noise pumps. Also as an automotive application area, there is always an effort to reduce manufacturing and assembly costs. It is therefore an object of the present invention to provide a low-noise, cost-effective electric pump unit which requires less installation effort than known universal units. Furthermore, the number of components should be reduced to keep costs low.

One problem with prior art vacuum pumps, particularly reciprocating piston pumps, is that they can generate excessive noise and vibration through their dynamic balance. One reason why this is common is that it is difficult to achieve good dynamic balance without using additional balancing mechanisms and costs if they are single reciprocating pistons. This is also common for dual opposed reciprocating piston pumps. Their pistons must be coupled to the drive mechanism through opposing crank halves. Due to the axial spacing between the pistons, a moment or vibration couple is created.

Another problem with conventional pumps is reducing the generated pumping noise; the exhaust gas sometimes enters the non-vacuum side of the piston. In this case, if the pistons are opposed, the pressure pulsations generated are equal to the full stroke of the reciprocating piston, as the two pistons co-act to compress the crankcase volume. The air is then typically exhausted to the atmosphere through a silencer element.

Another problem with single cylinder reciprocating piston pumps is balancing the main forces of the reciprocating piston mass; a rotating counterweight is used on the crank. However, when the piston mass is balanced by the counterweight at TDC, at a crank angle through TDC or BDC of the piston, the counterweight force acts in a different direction than the reciprocating mass force. This "imbalance force" varies in magnitude and direction throughout the crank rotation, thereby increasing the NVH of the pump.

Disclosure of Invention

The present invention solves this problem by means of a vacuum pump of the above-mentioned type, wherein the first and second cylinder axes are arranged at 90 degrees to each other and the electric drive motor is attached to the body driving a common crank pin, wherein the first and second piston rods engage said common crank pin so as to be commonly driven by said common crank pin. Due to the 90 degree arrangement of the cylinders, the present vacuum pump can be regarded as a so-called V-type vacuum pump, which is improved in terms of sound damping. In particular, this allows both pistons to be driven by a common crank pin, thereby reducing the number of components and keeping the overall design of the vacuum pump small. Furthermore, this results in a simple construction of the vacuum pump with improved balance and low noise for a double reciprocating piston vacuum pump. Preferably, the body comprises a crankcase in which the common crank pin is cranked (cranks). The electric drive motor is attached to the body, for example by a screw connection. The first and second cylinders are formed at least partially inside the body, but may also be formed mainly outside the body.

According to a first preferred embodiment, the first piston is rigidly attached to the first piston rod and the second piston is rigidly attached to the second piston rod. Preferably, the piston and the piston rod are formed as an integral part, i.e. as a one-piece construction. It will be appreciated that articulated pistons are also contemplated, but that a piston rigidly attached to the piston rod is simpler to manufacture. With this type of piston and piston rod, a so-called wobble or wobble piston compressor is provided. As the common crankpin rotates, the piston will rock within the cylinder. This again results in a reduced number of parts and a reduced manufacturing cost.

Furthermore, it is preferred that the first cylinder axis and the second cylinder axis lie in a common plane, wherein the first piston rod is offset from the first cylinder axis and from a center of the first piston by a first piston offset distance, and the second piston rod is offset from the second cylinder axis and from a center of the second piston by a second piston offset distance. The piston rods are thus respectively offset from a common plane formed by the two cylinder axes and from each other for the piston rods to be driven by a common crank pin. The piston rods may be designed to be close to each other but preferably not to touch each other to reduce friction. Preferably, the two piston and piston rod combinations are formed identical to each other, so that the number of components can be further reduced. Therefore, the piston and the piston rod are preferably symmetrical.

In another preferred embodiment, the vacuum pump comprises a first cylinder head for enclosing said first cylinder and a second cylinder head for enclosing said second cylinder, wherein said first cylinder head and said second cylinder head are attached to said body. The first and second cylinder heads are preferably attached to the body by screws. A seal ring may be disposed between the cylinder head and the body. Preferably, the first cylinder head and the second cylinder head are identical to each other, so that the number of parts can be reduced and maintenance can be simplified. The first and second cylinders are formed at least partially inside the cylinder head.

According to another preferred embodiment, the body comprises: a central inlet for connecting a vacuum pump to a consumer; a first body conduit and a second body conduit in fluid communication with the central inlet, wherein the first cylinder head includes a first head conduit in fluid communication with the first body conduit and terminating in the first cylinder, and wherein the second cylinder head includes a second head conduit in fluid communication with the second body conduit and terminating in the second cylinder. With this arrangement, the central inlet is connected to the first and second cylinders via the first and second body conduits and the first and second head conduits, respectively. These conduits are respectively formed such that they are connected to each other when the cylinder head is mounted to the body. In particular, it is contemplated that the cylinder heads are identical to each other, such that the first body conduit and the second body conduit are preferably provided in a manner enabling simple connection with the first head conduit and the second head conduit. Additional sealing means, such as O-rings, may be provided between the first and second cap conduits and the first and second body conduits, respectively.

The first cylinder head preferably includes a first inlet valve and the second cylinder head preferably includes a second inlet valve. The first and second inlet valves are preferably located at the terminal ends of the first and second lid conduits. The first and second inlet valves are preferably formed as one-way valves and more preferably as umbrella valves. In the case where a vacuum pump is used to induce a vacuum at the common inlet, the first and second inlet valves are preferably open in the direction of the cylinder and prevent fluid flow out of the cylinder and in the direction of the first and second head conduits. It should be understood that a vacuum pump may also be used as a compressor. In this case, the opening directions of the first and second inlet valves are preferably opposite, i.e., the first and second inlet valves open in a direction from the first and second cylinders to the first and second head conduits and prevent fluid from flowing from the first and second head conduits into the first and second cylinders. Preferably, the first and second inlet valves are positioned coaxially with the first and second cylinder axes such that the first and second inlet valves are located substantially in the center of the first and second cylinders.

Furthermore, it is preferred that the first piston comprises a first piston seal at the periphery of said first piston for sealing and guiding the first piston within the first cylinder, and wherein the second piston comprises a second piston seal at the periphery of said second piston for sealing and guiding the second piston within the second cylinder. Preferably, the first and second piston seals are formed as sealing rings or cup seals. In the case where they are formed as cup seals, when a vacuum is generated at the common inlet using a vacuum pump, the opening direction of the cup is a direction toward the piston rod. In the case of a vacuum pump used as a compressor, the opening direction of the cup-shaped cup seal is preferably directed away from the piston rod, i.e. in the direction of the first and second inlet valves. The first and second piston seals are used to guide the first and second pistons in the respective cylinders and allow the rocking motion of the first and second pistons as described above. Accordingly, the first and second piston seals are preferably formed of a low friction material (such as a dry PTFE compound).

To discharge air, preferably, the first piston comprises a first outlet valve and the second piston comprises a second outlet valve. First and second outlet valves are formed inside the first and second pistons and allow air drawn into the cylinder by the movement of the piston through the first and second inlet valves to escape through the first and second pistons, particularly into a crankcase formed inside the housing. Also, the first and second outlet valves are preferably formed as one-way valves and more preferably as umbrella valves. Preferably, they open in the direction of the piston rod and prevent fluid flow from the piston rod side of the piston to the cylinder side of the piston. When the vacuum pump is used as a compressor, the opening directions of the first and second outlet valves are preferably arranged oppositely, i.e. in this case the first and second outlet valves are open in the direction of the first and second cylinders and closed in the direction of the first and second piston rods.

Further, preferably, the first outlet valve is offset from the first cylinder axis by a first valve offset distance and the second outlet valve is offset from the second cylinder axis by a second valve offset distance. Preferably, the first and second outlet valves are offset opposite to the offset of the first and second piston rods, which allows for an enlarged outlet valve and greater stability of the piston. In particular, the piston rod does not need to be reshaped or adapted to the first and second outlet valves when the first and second outlet valves are respectively deflected.

According to another preferred embodiment, the body comprises a central outlet for discharging air. The central outlet is preferably in fluid communication with a crankcase, which in turn is in fluid communication with the discharge sides of the first and second outlet valves of the first and second pistons, respectively. The central outlet may be provided with a silencer or filter to reduce the acoustic emission of the vacuum pump.

Furthermore, it is preferred that the body comprises a crankcase in which the common crank pin is cranked, wherein said crankcase comprises a resonator volume shaped to act as a Helmholtz resonator (Helmholtz resonator). The helmholtz resonator generates sound waves by resonance, which allow cancellation of the sound waves entering the helmholtz resonator. When the first and second pistons are driven, they will each generate sound or pressure waves into the crankcase through their respective motions. In the crankcase, these sound or pressure waves are reflected and returned to the first and second pistons. By forming the crank case as a helmholtz resonator, the acoustic emission of the vacuum pump can be greatly reduced.

Preferably, the crankcase comprises an inlet into said resonator volume, such that the crankcase acts as a helmholtz resonator. In particular, sound waves exiting from the inlet of the crankcase cancel sound waves from the first and second piston heads and traveling toward the inlet.

To form a helmholtz resonator, preferably the body comprises a resonator insert for at least partially limiting the resonator volume. The insert may be formed from a plastics material and may be shaped to effectively form a resonator volume. However, the insert should comprise an inlet or recess for the respective first and second piston rods extending from the interior of the crankcase towards the first and second cylinders.

According to another preferred embodiment, the vacuum pump comprises a first cylinder tube defining said first cylinder and a second cylinder tube defining said second cylinder. Preferably, the first and second cylinder pipes are at least partially in the body and/or in the first and second cylinder heads, respectively. For example, the cylinder tubes may be made of a low friction material (such as aluminum) and attached within the first and second cylinder heads and held in place on the body by the first and second cylinder heads being screwed onto the body. Furthermore, it is conceivable that the first and second cylinder pipes are seated in the body and are simply closed or covered by the first and second cylinder heads.

Furthermore, it is proposed that the body and the first and second cylinder heads are formed from a plastic composite, while the first and second cylinder pipes are formed from an aluminum material. Thanks to such an embodiment, the production costs of the vacuum pump can be reduced while still reducing maintenance costs due to the low friction contact between the aluminium cylinder tube and the respective first and second piston seals.

According to a second aspect of the present invention, the above object is solved by a vehicle, in particular a passenger car, comprising a vacuum pump according to any of the preceding preferred embodiments of the vacuum pump according to the first aspect of the present invention.

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing. Detailed description the contents of what are considered to be preferred embodiments of the invention will be illustrated and described. It will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the present invention not be limited to the exact forms and details shown and described herein, nor to the entirety of the present invention disclosed and claimed herein. Furthermore, the features described in the specification, drawings and claims disclosing the invention may be essential to the invention considered alone or in combination. In particular, any reference signs in the claims shall not be construed as limiting the scope of the invention. The word "comprising" does not exclude other elements or steps. The word "a" or "an" does not exclude a plurality. The term "plurality" of items also includes the number 1, i.e. a single item, as well as other numbers, such as 2, 3, 4, etc.

Drawings

In the drawings:

figure 1 shows a perspective view of a vacuum pump according to the present invention;

figure 2 shows a top view of the vacuum pump according to figure 1;

figure 3 shows a complete cross-section through the vacuum pump along the line a-a according to figure 2;

figure 4 shows an enlarged view of the cylindrical part of the vacuum pump according to figure 3;

FIG. 5 shows a cross-sectional view of the barrel portion according to FIG. 4 taken along a plane perpendicular to the view of FIG. 4;

figure 6 shows an exploded view of the vacuum pump according to figure 1;

fig. 7 shows a complete sectional view along the line B-B according to fig. 2;

FIG. 8 shows a complete cross-sectional view similar to FIG. 7, but through the cylinder;

figure 9 shows a perspective view of a resonator insert;

FIG. 10 shows a first graph of the change in volume in the crankcase; and is

FIG. 11 shows a second chart showing piston pump torque calculations versus crank angle.

Detailed Description

The vacuum pump 1 (fig. 1) comprises a body 2, which body 2 defines a crankcase 3 (fig. 3). The body 2 also defines, at least in part, a first cylinder 4 and a second cylinder 6, in which first and second cylinders 4, 6 respective first and second pistons 8, 10 are reciprocally positioned.

The first cylinder 4 includes a first cylinder axis a1 (see fig. 3), and the second cylinder 6 includes a second cylinder axis a 2. The first and second cylinder axes a1, a2 are formed in a common plane E (see fig. 2) and include an angle a, which in this case is 90 degrees. It should be understood that small deviations of the angle alpha are also considered to be within the scope of the invention.

For driving the first and second pistons 8, 10, the vacuum pump 1 comprises an electric drive motor 20 attached to the body 2. In particular, the electric drive motor 20 is attached to the body 2 via screws 21 (see fig. 2). The electric drive motor includes a drive shaft 50 (see fig. 7 and 8) that rotates about a rotation axis R. The drive shaft 50 is coupled to a crank plate 52 which in turn carries a common crank pin 30. The common crank pin 30 is eccentrically attached to the crank plate 52 with an eccentricity e1 (see fig. 3). The value of the eccentricity e1 depends on the actual dimensions of the vacuum pump 1, in particular on the dimensions of the cylinders 4, 6. The crank plate 52 is non-rotationally symmetrical and comprises a weight portion 54, which weight portion 54 is used for weight compensation when driving the first and second pistons 8, 10.

The common crank pin 30 drives both the first and second pistons 8, 10 by carrying both the first and second piston rods 14, 16. In particular, the first and second piston rods 12, 14 are seated on the common crank pin 30 by first and second roller bearings 56, 58 (see fig. 7). This is done in order to reduce friction in the vacuum pump 1. Since the first and second cylinder axes a1, a2 are arranged at 90 degrees to each other, the first and second pistons 8, 10 will reach TDC and BDC, respectively, at different angles of the drive shaft 50. This arrangement should reduce noise and vibration compared to the first and second cylinders in the row. Also when compared to a box arrangement (where the angle alpha is 180 degrees), the volume of the whole system, in particular the crankcase 3, can be reduced. The volume of air moved is reduced, which results in reduced sound and noise generation.

The first and second cylinders 4, 6 are formed partially in the body 12 and partially in first and second cylinder heads 16, 18, respectively, attached to the body 2. The first and second cylinder heads 16, 18 are identically formed, thereby reducing the number of parts.

To connect the consumers to the vacuum pump 1, the vacuum pump 1 comprises a central inlet 22 formed in the body 2. The central inlet 22 in the embodiment shown in fig. 1 is provided with an inlet fitting 23, which may for example be formed as a hose connector or the like. First and second body conduits 24, 26 branch from the central inlet 22 in the body 2, which in turn are in fluid communication with the central inlet 22 (see fig. 3 and 6).

To connect those first and second body conduits 24, 26 with the respective first and second cylinders 4, 6, the first cylinder head 16 includes a first head conduit 25, while the second cylinder head 18 includes a second head conduit 27. According to the shown embodiment, the first and second lid conduits 25, 27 comprise first and second side inlets 28, 29, however, said first and second side inlets 28, 29 are regularly closed.

The first head conduit 25 terminates at the first cylinder 24 concentrically with the first cylinder axis a1 and is provided with a first inlet valve 32. Correspondingly, the second head conduit 27 terminates concentrically with the second cylinder axis a2 at the second cylinder 6 and is provided with a second inlet valve 34. The first and second inlet valves are formed as so-called umbrella valves and comprise first and second inlet valve members 33, 35, which first and second inlet valve members 33, 35 are formed of an elastic material and can be opened in a direction towards the first and second cylinders 4, 6, respectively, so that air can flow through the first and second cover conduits 25, 27 into the first and second cylinders 4, 6 when the respective first and second pistons 8, 10 are moved towards the crankcase.

In order to generate a vacuum between the first piston 8 and the first inlet valve 32 and between the second piston 10 and the second inlet valve 34, respectively, the first and second pistons 8, 10 comprise first and second piston seals 36, 38. A first piston seal 36 is provided at the first periphery 9 of the first piston 8. The first and second piston seals 36, 38 may generally be formed in any suitable manner, for example as sealing rings or other sealing means that allow the wobble piston to be guided within the cylinders 4, 6. In the embodiment shown, the first and second piston seals 36, 38 are formed as so-called cup seals 37, 39. The first and second cup seals 37, 39 are arranged such that the cup-shaped openings of the first and second cup seals 37, 39 open in a direction towards the first and second piston rods 12, 14. Thus, the first and second cup seals 37, 39 can withstand relatively high pressures.

In order to guide the first and second pistons 8, 10 by using the first and second piston seals 36, 38 in the first and second cylinders 4, 6, the first and second cylinders 4, 6 are provided with first and second cylinder tubes 46, 48. Preferably, the first and second cylinder tubes 46, 48 are fixedly retained within the first and second cylinder heads 16, 18, respectively, and are also preferably seated on first and second body abutments 60, 62 (see FIG. 3) formed in the body 2. Due to this arrangement, no additional positioning means are required for fixing the first and second cylinder tubes 46, 48, which again reduces the number of components. The first and second cylinder tubes 46, 48 are preferably formed of an aluminum material that provides a low-weight vacuum pump and low-friction surfaces for contacting the first and second piston seals 36, 38.

In order to expel the air compressed between the first and second pistons 8, 10 and the first and second inlet valves 32, 34, respectively, when the first and second pistons 8, 10 are moved upwards towards the first and second inlet valves 32, 34, the first and second pistons 8, 10 comprise respective first and second outlet valves 40, 42. The first and second outlet valves 40, 42 are again formed as umbrella valves and comprise first and second outlet valve elements 41, 43, which first and second outlet valve elements 41, 43 open in a direction towards the first and second piston rods 12, 14.

As can be seen in particular in fig. 5 and 8, the respective first and second outlet valves 40, 42 are offset from the respective centers C1, C2 of the first and second pistons 8, 10. That is, the central axis V of the first and second outlet valves 41, 43 is not coaxial with the central axes a1, a2 of the first and second cylinders 4, 6, but is offset from the central axes a1, a2 when the first and second pistons 8, 10 are in the following positions: the common crankpin 30 is centered relative to the respective first and second piston axes a1, a 2. The first and second valve offset distances V1, V2 of the first and second outlet valves 40, 42 are measured from the central exit points of the first and second outlet valves 40, 42 and the central axes a1, a2 of the first and second cylinders 4, 6. Furthermore, the central axes of the first and second outlet valves 40, 42 are angled relative to the first and second cylinder axes a1, a2, which allows for an enlarged outlet valve 40, 42 and thus more efficient use of the vacuum pump 1.

Furthermore, it can be concluded that the first and second piston rods 12, 14 are also offset with respect to the first and second cylinder axes a1, a2 and with respect to the common plane E of the first and second cylinder axes a1, a 2. In particular, both the first and second piston rods 12, 14 are offset by respective first and second piston offset distances P1, P2, said first and second piston offset distances P1, P2 preferably being of the same size. By offsetting the first and second piston rods 12, 14 from the respective first and second cylinder axes a1, a2, there is sufficient space for the first and second piston rods to be driven by the common crank pin 30.

After the air has been discharged through the first and second outlet valves 40, 42, respectively, the air passes through the crankcase 3 and then through the central outlet 44. The central outlet 44 is provided with a discharge valve 45, which is again formed as an umbrella valve.

The crankcase 3 comprises a resonator volume 70 shaped to act as a helmholtz resonator 72. To achieve this, the crankcase 3 contains an inlet 74 (depicted by the horizontal dashed line in fig. 8), which inlet 74 separates the resonator volume 70 from the volume inside the body 2 and inside the first and second cylinder heads 16, 18. As the respective first and second pistons 8, 10 move towards the axis of rotation R, and thus towards the crankcase 3, the first and second pistons 8, 10 push some air towards the crankcase 3, causing pressure or sound waves to travel through the inlet 74 into the resonator volume 70 in the crankcase 3. To define the resonator volume 70, the vacuum pump 1 comprises a resonator insert 76, the resonator insert 76 also being shown in perspective view in fig. 9. The resonator insert 76 partially confines the resonator volume by providing a rim 78. The rim portion 78 substantially includes a cavity portion 80 that substantially defines the resonator volume 70. The rim 78 includes a first recess 82 and a second recess 84 formed to allow movement of the first and second piston rods 12, 14.

In the body portion of the resonator insert 76, the resonator insert 76 comprises a plurality of openings 86 allowing access to a space 88 between a valve wall 90 and a cover 92, both of said valve wall 90 and cover 92 being attached to the body 2. The valve wall 90 carries the discharge valve 45 and does not include any other openings than the discharge valve 45. In the space 88, a damping filter or the like may be provided. This in turn may reduce the generation of noise. The cover 92 includes a slot 94 at its lower end to ultimately allow air to reach the environment.

Fig. 10 shows a first graph comparing the air volumes moving inside the body 2 and in particular inside the crankcase 3 due to the movement of the first and second pistons 8, 10 in a V-Twin EVP, which is the vacuum pump 1 of the invention, and a Boxer Twin EVP, which is a vacuum pump with an angle α of 180 degrees. As can be seen from fig. 10, the displaced air volume is reduced by 17% for the point of maximum rotation of the first and second pistons 8, 10, which results in a higher efficiency and a reduced noise level of the vacuum pump 1 according to the invention. Fig. 11 shows the torque (motor torque V-Twin) necessary to drive the vacuum pump 1 according to the invention compared to a Boxer type vacuum pump (motor torque box) of the vacuum pump 1 with an angle alpha of 180 degrees. As can be seen from fig. 11, the motor torque required by the vacuum pump according to the invention is considerably reduced compared to the prior art vacuum pump, resulting in a higher efficiency and less energy consumption of the vacuum pump 1 according to the invention.

List of reference signs (part of the description):

1 vacuum pump

2 main body

3 crank case

4 first cylinder

6 second cylinder

8 first piston

9 first periphery

10 second piston

11 second peripheral edge

12 first piston rod

14 second piston rod

16 first cylinder cover

18 second cylinder head

20 electric drive motor

21 screw

22 central inlet

23 Inlet fitting

24 first body conduit

25 first cover conduit

26 second body conduit

27 second cover conduit

28 first side inlet

29 second side inlet

30 common crank pin

32 first inlet valve

33 first inlet valve member

34 second inlet valve

35 second inlet valve member

36 first piston seal

37 first cup seal

38 second piston seal

39 second cup seal

40 first outlet valve

41 first outlet valve element

42 second outlet valve

43 second outlet valve element

44 central outlet

45 injection valve

46 first cylinder pipe

48 second cylinder pipe

50 drive shaft

52 crank plate

54 parts by weight

56 first roller bearing

58 second roller bearing

60 first body mount

62 second body mount

70 resonator volume

72 Helmholtz resonator

74 inlet of crankcase

76 resonator insert

78 edge part

80 chamber

82 first recess

84 second recess

86 holes

88 space

90 valve wall

92 cover

94 slots in the closure

A1 first cylinder axis

A2 second Cylinder axis

e1 eccentricity

E common plane

Angle alpha

R axis of rotation

C1 first piston center

C2 second piston center

Central axis of V outlet valve

V1 first valve offset distance

V2 second valve offset

P1 first piston offset

P2 second piston offset.