Double-acting two-stage piston pump

Abstract

A double-acting two-stage piston pump comprises a pump housing having a piston arrangement connected to a drive shaft that, when driven, moves the piston arrangement, where the piston arrangement comprises at least two first primary pistons, and a second primary piston. The first primary pistons are slidably disposed in respective first primary cylinders formed in the pump housing. The piston arrangement also includes at least two secondary pistons slidably disposed in respective secondary cylinders formed in the primary piston. The primary piston and the second secondary piston are mounted on and directly driven by an eccentric, wherein the eccentric is mounted on the drive shaft.

Description

Technical Field

[0001] The present invention relates to a pump, in particular a vacuum pump, comprising a pump housing having a piston arrangement connected to a drive shaft, the drive shaft causing the piston arrangement to move when driven, wherein the piston arrangement comprises a first primary piston and a second primary piston, the first primary piston being slidably arranged in a first primary cylinder formed in the pump housing, the second primary piston being slidably arranged in a second primary cylinder formed in the pump housing. The piston arrangement further comprises a first secondary piston and a second secondary piston, the first secondary piston being slidably arranged in a first secondary cylinder formed in the first primary piston, the second secondary piston being slidably arranged in a second secondary cylinder formed in the second primary piston. Such a pump can be used to induce a vacuum at a pump inlet and / or to provide a pressurized fluid at a pump outlet. Background Art

[0002] Vacuum pumps are known, for example, from WO 2017 / 137144 A1 or WO 2017 / 137141 A1. Such vacuum pumps are usually called piston vacuum pumps, in contrast to so-called rotary vane vacuum pumps. Pumps of the aforementioned type comprise at least one piston which moves back and forth in a cylinder. The pump inlet is usually connected to a working chamber formed by the cylinder, so that when the piston moves in the cylinder to increase the working volume of the working chamber, a vacuum is induced at the inlet. In order to increase this vacuum, such piston vacuum pumps usually comprise a primary and a secondary, wherein the secondary further increases the vacuum generated by the primary.

[0003] Pumps of this type are used in passenger vehicles or trucks, in particular as vacuum pumps for supplying vacuum to specific modules of the vehicle. The vacuum is used, for example, for brake booster modules in trucks or for pneumatic brake systems. For common gasoline or diesel engine vehicles, the vacuum pump is usually installed in the engine area and connected to the crankshaft of the engine to be driven. However, modern vehicles include improved electrical systems, so that the vacuum pumps of modern vehicles are more often driven by electric motors. The present invention particularly relates to such vacuum pumps, which are driven by electric motors inside the vehicle.

[0004] Problems associated with piston pumps in the automotive sector are in particular noise and vibration generation. This applies in particular to single-piston, one-stage piston pumps. Two-stage piston pumps are more balanced from a torque point of view, since the two stages can be driven alternately. However, such common two-stage piston pumps usually suffer from higher unbalanced inertial loads, which in turn translates into higher noise and vibration levels.

[0005] A piston vacuum pump balanced in an improved manner is disclosed in US 2015 / 0078932 A1. However, this vacuum pump is rather complex and involves a plurality of different components. In addition, compared with a common vane vacuum pump, the vacuum pump disclosed in US 2015 / 0078932 A1 is relatively large.

[0006] WO 2019 / 114923 A1 shows a piston pump, which includes a pump housing having at least one pump inlet and one pump outlet, and a piston device connected to a drive shaft. When the drive shaft is driven, the piston device is caused to move. The piston device includes: a first primary piston slidably disposed in a first primary cylinder formed in the pump housing; a first secondary piston; wherein the first secondary piston is slidably disposed in a first secondary cylinder formed in the first primary piston. This piston pump is formed as a so-called double piston pump, and thus also includes a second primary piston and a second secondary piston, wherein the second primary piston is slidably disposed in a second primary cylinder formed in the pump housing, and the second secondary piston is slidably disposed in a second secondary cylinder formed in the second primary piston. In the piston pump of WO 2019 / 114923 A1, the piston device is caused to move due to a slider guide that connects the piston to a corresponding eccentric member mounted on the drive shaft. In other words, a so-called "Scotch yoke" mechanism is used to convert the rotational movement of the drive shaft into a sliding movement of the block guide, and then into a linear movement of the piston.

[0007] However, in the case of a piston pump, the "Scotch yoke" mechanism brings several problems. In particular, it does not represent a robust solution and causes wear and noise problems. Moreover, this arrangement results in high power consumption. In addition, the "Scotch yoke" design has a crank as part of the piston group: thus, the diameter operation holes tend to be a constraint, preventing the use of properly sized bearings. Summary of the Invention

[0008] Therefore, an object of the present invention is to provide a more robust piston pump that allows for better durability. Another object of the present invention is to provide a piston pump having lower noise and power consumption. Another object of the present invention is to provide a piston pump that allows for a more compact design and is easier to assemble and manufacture. Another object of the present invention is to provide a piston pump that avoids problems of linear sliding motion at the bearings and allows the use of larger rolling element bearings.

[0009] These and other objects are achieved by a piston pump, which includes a pump housing having piston means connected to a drive shaft, and the drive shaft, when driven, causes the piston means to move. Such piston means includes: a first primary piston slidably disposed in a first primary cylinder formed in the pump housing; a first secondary piston slidably disposed in a first secondary cylinder formed in the first primary piston; a second primary piston slidably disposed in a second primary cylinder formed in the pump housing; and a second secondary piston slidably disposed in a second secondary cylinder formed in the second primary piston.

[0010] The drive shaft of the piston pump of the present invention includes a first eccentric member and a second eccentric member, which are phase-shifted by 180°; further, the first secondary piston includes a first secondary piston rod, and the second secondary piston includes a second secondary piston rod.

[0011] The piston pump of the present invention is characterized in that the first primary piston and the second secondary piston rod are mounted on the second eccentric member and directly driven thereby, and the first secondary piston rod and the second primary piston are mounted on the first eccentric member and directly driven thereby.

[0012] Directly driving the primary piston and the secondary piston by the eccentric member allows the rotational motion of the drive shaft to be directly converted into the linear reciprocating motion of the piston, thereby eliminating any intermediate sliding mechanism. In the following case of referring to a pump or a vacuum pump, it should also be noted that the pump can also be used as a compressor. Whether it is used as a compressor or a vacuum pump mainly depends on how the consuming device is connected to the pump inlet and / or the pump outlet. Since the preferred use of the disclosed pump is to generate a vacuum, the embodiments will be mainly described with respect to the vacuum pump application.

[0013] The pump of the present invention is based on the concept that the space within the primary piston (which generally has a larger piston face than the secondary piston) is used to form a secondary cylinder in which the secondary piston can reciprocate. Due to this arrangement, the overall size of the pump can be reduced. The second stage is formed within the first stage and is not adjacent to it or at any other position. When the primary piston moves relative to the pump housing within the corresponding primary cylinder formed in the pump housing, the secondary piston moves within the primary piston. Therefore, in order to create a vacuum in the second stage, it is necessary that the secondary piston moves relative to the primary piston and preferably also relative to the pump housing.

[0014] Preferably, when the present invention relates to a vacuum pump, the secondary cylinder has a larger volume than the primary cylinder.

[0015] Even more preferably, the volume of the secondary cylinder of the vacuum pump of the present invention is approximately 10% larger than the volume of the respective primary cylinder of the vacuum pump.

[0016] According to one aspect, when the present invention relates to a vacuum pump, due to the fact that the stroke of the secondary piston is approximately twice as long as the stroke of the primary piston, the secondary cylinder has a larger volume than the primary cylinder.

[0017] Preferably, when the present invention relates to a compressor, the secondary cylinder has a smaller volume than the primary cylinder.

[0018] In a preferred embodiment of the pump, the drive shaft of the pump includes a first eccentric and a second eccentric, the first eccentric and the second eccentric being phase-shifted by 180°, wherein the first primary piston and the second secondary piston are driven by the second eccentric, and wherein the first secondary piston and the second primary piston are driven by the first eccentric. It should be understood that since the secondary pistons move within the primary pistons, they are connected to the eccentrics by rods which move with their respective secondary pistons. Further, it should be understood that depending on the overall design of the pump, other phase-shifts may also be preferred. For example, pumps using a 90-degree phase-shift or a 120-degree phase-shift are known. However, a 180° phase-shift has been shown to be the most effective and enables a very well-balanced pump.

[0019] In a preferred further development, the first eccentric includes a first eccentricity relative to the rotational axis of the drive shaft, and the second eccentric includes a second eccentricity relative to the rotational axis. The first eccentricity is preferably the same as the second eccentricity such that the corresponding piston strokes can be the same.

[0020] However, when different piston strokes are desired, the first eccentricity and the second eccentricity can be different from each other.

[0021] According to one aspect, the first eccentric and the second eccentric are integrally formed with the drive shaft. Thus, the drive shaft, the first eccentric, and the second eccentric are formed in a one-piece configuration, which enables a reduction in the components of the piston pump.

[0022] According to a preferred aspect, the first eccentric and the second eccentric are separate components, which allows for simple manufacture and installation. According to a preferred aspect, the pistons and / or piston rods are mounted on the eccentrics via respective bearings (such as needle bearings).

[0023] In a preferred embodiment, the drive shaft includes studs, and the first eccentric and the second eccentric are mounted on the studs. According to one aspect, the drive shaft and / or the studs, the first eccentric, and the second eccentric are separate components. According to one aspect, the drive shaft and / or the studs, the first eccentric, and the second eccentric are formed as a single component.

[0024] According to one aspect, at least the first eccentric and / or at least the second eccentric are fixedly mounted on the studs. According to one aspect, at least the first eccentric and / or at least the second eccentric are threadedly engaged with the studs.

[0025] In another preferred embodiment, the first eccentric member is provided with first torque transmission and alignment means which are configured to engage corresponding second torque transmission and alignment means provided on the second eccentric member in a predetermined angular manner. Preferably, the first torque transmission and alignment means includes a first form-locking element and the second torque transmission and alignment means includes a second form-locking element which engages the first form-locking element. According to a preferred aspect, the first torque transmission and alignment means provided on the first eccentric member includes at least a first projection and preferably a second projection. The second torque transmission and alignment means provided on the second eccentric member preferably includes at least one third projection which is configured to cooperate with the at least first projection and preferably the second projection provided on the first eccentric member.

[0026] According to one aspect, such first torque transmission and alignment means and second torque transmission and alignment means allow the first eccentric member and the second eccentric member to be rotationally positioned at a predetermined angle (e.g., 180°).

[0027] According to one aspect, such first torque transmission and alignment means and second torque transmission and alignment means allow the first eccentric member and the second eccentric member to transmit torque and co-rotate with the drive shaft and / or the stud. In addition, they allow for simple manufacture and installation. According to a preferred aspect, the first torque transmission and alignment means provided on the first eccentric member and the second torque transmission and alignment means provided on the second eccentric member are located near the stud so as to minimize inertial forces. According to one aspect, a nut is threadedly engaged with the stud and engages the second eccentric member for force transmission.

[0028] According to a second, alternative embodiment, the drive shaft includes a cap screw and the first eccentric member and the second eccentric member are mounted on such cap screw. According to one aspect, at least the first eccentric member and / or at least the second eccentric member is fixedly mounted on the cap screw. According to one aspect, at least the first eccentric member and / or at least the second eccentric member is threadedly engaged with the cap screw. According to one aspect, the second eccentric member is provided with a flange which is configured to cooperate with a recess provided on the first eccentric member.

[0029] According to one aspect, the piston pump of the present invention according to the second, alternative embodiment further includes a pin which is configured to fixedly couple the flange provided on the second eccentric member with the recess provided on the first eccentric member. Preferably, the pin is press-fitted into corresponding holes provided in both the flange and the recess.

[0030] According to one aspect of the present invention, the above object is solved by a method for installing a piston pump, preferably according to the first embodiment, the method comprising the steps of: mounting a first secondary piston rod and a second primary piston on a first eccentric member; press-fitting a drive shaft into the first eccentric member; inserting the first secondary piston rod, the second primary piston, the first eccentric member and the drive shaft into a piston housing; mounting a second eccentric member on the drive shaft and aligning it with the first eccentric member; and mounting a first primary piston and a second secondary piston rod on the second eccentric member.

[0031] According to one aspect, the first eccentric member is press-fitted onto a stud. According to another aspect, the first secondary piston rod, the second primary piston, the first eccentric member, the drive shaft and / or the stud represent a "piston group" or at least one intermediate "piston group", and thus conveniently slide down and / or are inserted together into the pump housing.

[0032] According to one option, the first secondary piston is mounted on the first secondary piston rod before the "piston group" is inserted into the pump housing: in other words, the first secondary piston belongs to the "piston group".

[0033] According to an alternative option, the first secondary piston is mounted on the first secondary piston rod only after the "piston group" has been inserted into the pump housing.

[0034] According to yet another aspect, the first secondary piston rod, the second primary piston, the first eccentric member, the drive shaft and / or the stud, the second eccentric member, the second secondary piston rod and the first primary piston represent a "piston group", and thus slide down and / or are inserted into the pump housing. The first secondary piston and / or the second secondary piston may or may not belong to the "piston group": in other words, the first secondary piston and / or the second secondary piston may be mounted on their respective secondary piston rods before or after the "piston group" is inserted into the pump housing.

[0035] Optionally, the "piston group" further includes a nut mounted on the stud, the nut being in contact force transfer engagement with the second eccentric member.

[0036] According to yet another alternative option, the nut is mounted on the "piston group" only after the "piston group" has been inserted into the pump housing.

[0037] Preferably, the nut is threadedly engaged with the stud.

[0038] According to one aspect of the present invention, the above object is solved by a vehicle (in particular a passenger car) which includes a piston pump according to any of the preferred embodiments of the above piston pump. However, it should also be understood that the pump according to the present invention can also be used in applications other than vehicles, and in particular in applications other than braking systems. Other uses of the pump for generating vacuum on a vehicle can include engine mounts, compressor wastegates, and by-pass valve actuation. This type of pump can also feasibly be used to evacuate, for example, the housing for a KERS (Kinetic Energy Recovery System).

[0039] To more fully understand the present invention, the present invention will now be described in detail with reference to the accompanying drawings. The detailed description will illustrate and describe embodiments that are considered to be the preferred embodiments of the present invention. Of course, it should be understood that various modifications and changes in form or detail can be easily made without departing from the spirit of the present invention. Therefore, the present invention may not be limited to the exact forms and details shown and described herein, nor to any content less than the entire invention disclosed herein and claimed below. In addition, the features described in the description, drawings, and claims of the present invention may be necessary for the present invention considered individually or in combination. In particular, any reference numerals in the claims should not be construed as limiting the scope of the present invention. The phrase "comprising" does not exclude other elements or steps. The words "a" or "an" do not exclude a plurality. The phrase "a plurality of" items also includes the number 1, i.e., a single item, as well as additional numbers such as 2, 3, 4, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the drawings:

[0041] Figure 1 A perspective view of a prior art piston pump including a "Scotch yoke" mechanism is shown;

[0042] Figure 2 A cross-sectional view of the piston pump of the present invention is shown;

[0043] Figure 3 A simplified cross-sectional view of the crank mechanism of the first embodiment of the piston pump of the present invention is shown;

[0044] Figure 4 Shows Figure 3 a perspective view of the crank mechanism;

[0045] Figure 5 Shows Figure 3 and Figure 4 a perspective view of a first eccentric and a second eccentric which form part of the crank mechanism;

[0046] Figure 6 A simplified cross-sectional view of the crank mechanism of the second embodiment of the piston pump of the present invention is shown;

[0047] Figure 7 shows Figure 6 a perspective view of the crank mechanism of

[0048] Figure 8 shows Figure 6 and Figure 7 a perspective view of a first eccentric member and a second eccentric member that form part of the crank mechanism of

[0049] Figure 9 a schematic view of a vehicle. DETAILED DESCRIPTION

[0050] The piston pump 1 according to the present disclosure is adapted to be installed within a vehicle 100 (see Figure 9 ) and serves as a vacuum pump to provide vacuum for a braking system or any other consuming device in the vehicle. The piston pump 1 is particularly suitable for being driven by an electric motor, which is not shown in the drawings for simplicity.

[0051] The following embodiments show the piston pump 1 ready to serve as a vacuum pump and creating a vacuum at the pump inlet (not shown). However, the same configuration can also be used as a compressor.

[0052] More specifically, the piston pump 1 includes a substantially cylindrical pump housing 2. The pump housing 2 has a pump inlet (not shown) that can be connected to a consuming device. In addition, the pump housing includes a pump outlet (not shown) leading to the environment. The pump outlet can be formed as a simple opening in the pump housing 2. When the piston pump 1 serves as a vacuum pump, the fluid, especially air, drawn from the pump inlet is not used and is only discharged to the environment rather than supplied to any consuming device.

[0053] A piston device 8 is disposed within the pump housing 2, which will be described in more detail below. The piston device 8 is connected to a drive shaft 10 that, when driven, causes the piston device 8 to move to create a vacuum at the pump inlet. The drive shaft 10 is rotatable about a rotational axis A and can be connected to an electric motor.

[0054] According to Figure 2 the embodiment shown, the piston device 8 includes a first primary piston 12 that is slidably disposed within a first primary cylinder 14 formed in the pump housing 2.

[0055] The piston pump 1 according to the illustrated embodiment is formed as a dual-type two-stage piston pump and thus also includes a first secondary piston 16 which is arranged within a first secondary cylinder 18 that is formed within a first primary piston 12. Thus, the first primary piston 12 is formed in a hollow manner to form the first secondary cylinder 18. The first primary piston 12 includes a first primary piston wall 13 that defines the first secondary cylinder 18. In particular, the first secondary cylinder 18 is formed by the inner peripheral surface of the first primary piston wall 13 within the first primary piston 12.

[0056] In order to move the first primary piston 12 and the first secondary piston 16, the first primary piston 12 is driven by a second eccentric 22 of the drive shaft 10, and the first secondary piston 16 is driven by a first eccentric 20 of the drive shaft 10. Both the first eccentric 20 and the second eccentric 22 are mounted on a stud 21. The first eccentric 20 and the second eccentric 22 are phase-shifted by 180°.

[0057] In a similar manner, the piston device 8 according to this embodiment also includes a second primary piston 40 which is slidably disposed within a second primary cylinder 42 that is likewise formed within the pump housing 2. The entire interior 3 of the pump housing 2 can be formed as a cylindrical hollow portion to form both the first primary cylinder 14 and the second primary cylinder 42.

[0058] A second secondary piston 44 is also provided which is slidably disposed within a second secondary cylinder 46 that is formed within the second primary piston 40. Similarly, the second primary piston 40 includes a second primary piston wall 41 which defines the second secondary cylinder 46 by restricting the inner peripheral surface of the second hollow space 47.

[0059] In order to drive the second primary piston 40 and the second secondary piston 44, the second primary piston 40 is connected to the first eccentric 20, and the second secondary piston 44 is connected to the second eccentric 22. Thus, the first eccentric 20 drives the second primary piston 40 as well as the first secondary piston 16, and in turn the second eccentric 22 drives the first primary piston 12 and the second secondary piston 44. Thus, the movement of the pistons is the same, yet phase-shifted by 180°.

[0060] In addition, in Figure 2As can be seen, the first primary cylinder 14 includes a first central axis B1, and the second primary cylinder 42 includes a second central axis B2, and the first central axis B1 and the second central axis B2 are coaxial. Therefore, the first central axis B1 and the second central axis B2 form a single axis on which the first primary piston 12 and the second primary piston 40 move. When the first secondary cylinder 18 and the second secondary cylinder 46 are concentrically formed within the corresponding first primary piston 12 and second primary piston 40, the first secondary piston 16 and the second secondary piston 44 also move coaxially with the first central axis B1 and the second central axis B2. Therefore, the overall design of the piston pump 1 is an opposed piston pump, in which a single piston moves in two opposite directions. This can result in a well-balanced design.

[0061] The first secondary piston 16 includes a first piston rod 54 that extends through a first assembly opening 60 in the first primary piston wall 13. A portion of the first hollow space 19 that is on the side of the piston rod 54 opposite the first secondary piston face 30 may be referred to as the first secondary working chamber. In the same manner, the second secondary piston 44 includes a second piston rod 56 that extends through a second assembly opening 58 formed in the second primary piston wall 41 of the second primary piston 40.

[0062] The first primary piston 12 and the second secondary piston rod 56 are mounted on the second eccentric member 22 and are directly driven thereby. Subsequently, the first secondary piston rod 54 and the second primary piston 40 are mounted on the first eccentric member 20 and are directly driven thereby.

[0063] The mounting of the first primary piston 12 and the second secondary piston rod 56 on the second eccentric member 22 may include a needle bearing 229. Subsequently, the mounting of the first secondary piston rod 54 and the second primary piston 40 on the first eccentric member 20 may also include a needle bearing 209.

[0064] The flow of fluid within the piston pump of the present invention is well known in the art and will not be described in detail. However, reference is made to the aforementioned prior art document WO 2019 / 114923 A1.

[0065] Figure 2 The crank mechanism of (which is in Figure 3 、 Figure 4 and Figure 5which is shown in detail in) relates to a first embodiment of the present invention and includes a stud 21 fixedly mounted on a drive shaft 10. The first eccentric member 20 is fixedly mounted on the drive shaft 10 and / or the stud 21, for example, by screws or other form-locking mechanisms. Preferably, the first eccentric member 20 is fixedly mounted on the drive shaft 10 and / or the stud 21 by press-fitting. The first eccentric member 10 includes a hole 213 to allow insertion and mounting on the stud 21 and / or the drive shaft 10.

[0066] Near the hole 213, a first protrusion 211 and a second protrusion 212 are provided, each protrusion having at least a flat coupling surface. The second eccentric member 22 also includes a hole 223 to allow insertion and mounting on the stud 21. Corresponding to the hole 223 (preferably coaxially with the hole 223), a third protrusion 222 is further provided, which has at least two flat coupling surfaces configured to engage the corresponding flat coupling surfaces of the first protrusion 211 and the second protrusion 212 provided on the first eccentric member 20 in a predetermined angular manner. In this way, the first eccentric member and the second eccentric member can be aligned in a predetermined angular manner. The protrusions 211, 212, 222 are designed to transmit torque between the first eccentric member 20 and the second eccentric member 22 so that they can rotate together about the axis of rotation A of the drive shaft 10 and the stud 21. It should be understood that in other embodiments, the first protrusion 211 and the second protrusion 212 are provided on the second eccentric member 22, while the third protrusion is provided on the first eccentric member 20. Any other means for at least partially form-locking torque transmission is also contemplated. It should also be understood that instead of the first protrusion 211 and the second protrusion 212, a groove may be provided on one of the eccentric members 20, 22, and the third protrusion 222 may engage in the groove.

[0067] A nut 23 is threadedly fixed to the stud 21 and further fixes the second eccentric member 22 in its axial position along the axis of rotation A of the stud 21 and its rotational position relative to the first eccentric member 20.

[0068] The assembly of the piston pump 1 according to the first embodiment of the present invention can be conveniently envisioned with at least part of the pistons assembled together before sliding down along the pump housing 2. As a first assembly step, the first secondary piston rod 54, together with the first secondary piston 16, and the second primary piston 40 are mounted on the first eccentric 20. Subsequently, the first eccentric 20 is fixedly mounted on the drive shaft 10 and / or the stud 21, for example, by press fitting. In this way, an intermediate "piston group" is formed, which includes the drive shaft 10 and / or the stud 21, the first eccentric 20, the secondary piston 16 and its first secondary piston rod 54, and the second primary piston 40. Such an intermediate "piston group" is then inserted into the pump housing 2. Thereafter, due to the torque transmission and alignment means, i.e., the protrusions provided on the first eccentric and the second eccentric, the second eccentric 22 is mounted on the drive shaft 10 and aligned with the first eccentric 20. Finally, the first primary piston 12 and the second secondary piston rod 56 and their corresponding second secondary pistons 44 are mounted on the second eccentric 22.

[0069] Figure 6 , Figure 7 and Figure 8 Fig. shows a crank mechanism according to a second, alternative embodiment of the present invention. According to such an alternative embodiment, the drive shaft 10, the first eccentric 20, and the second eccentric 22 are held together by a cap screw 300. The first eccentric 20 includes a recess 302 and a hole 213 to allow insertion and mounting on the cap screw 300. The first eccentric 20 further includes a second hole 304 to allow insertion and mounting of the pin 303. The second eccentric 22 includes a hole 223 to allow insertion and mounting on the cap screw 300, and a flange 301. The flange 301 is designed to fit into the recess 302 of the first eccentric 20 and includes a second hole 305 to allow insertion and mounting of the pin 303. In other words, the pin 303 ensures a fixed connection of the flange 301 of the second eccentric 22 with the recess 302 of the first eccentric 20, and thus, the first eccentric 20 and the second eccentric 22 are aligned at a predetermined rotational angle and they are able to rotate together. Preferably, the pin 303 is inserted into the second hole 304 on the first eccentric 20 and the second hole 305 on the flange 301 by press fitting.

[0070] Figure 9A schematic view of a vehicle 100 is now depicted. The vehicle 100 is preferably configured as a passenger car or a light truck and includes a pneumatic braking system 102. The braking system 102 is shown by a pipeline 104 that leads to wheels 106a, 106b, 106c, 106d to provide corresponding braking pressure for the wheels 106a, 106b, 106c, 106d. The pipeline 104 is connected to a central module 108. The vehicle 100 also includes an engine 110 and a piston pump 1 according to the present invention, which is used as a vacuum pump 1 herein. The piston pump 1 provides vacuum for the braking system 102, and this vacuum can be used, for example, by a brake booster of the braking system 102, which can be implemented in the central module 108.

[0071] List of reference numerals (part of the specification)

[0072] 1 Piston pump

[0073] 2 Pump housing

[0074] 3 Interior of the pump housing

[0075] 8 Piston device

[0076] 10 Drive shaft

[0077] 12 First primary piston

[0078] 13 First primary piston wall

[0079] 14 First primary cylinder

[0080] 16 First secondary piston

[0081] 18 First secondary cylinder

[0082] 19 First hollow space

[0083] 20 First eccentric

[0084] 21 Stud

[0085] 22 Second eccentric

[0086] 23 Nut

[0087] 30 First secondary piston face

[0088] 40 Second primary piston

[0089] 41 Second primary piston wall

[0090] 42 Second primary cylinder

[0091] 44 Second secondary piston

[0092] 46 Second secondary cylinder

[0093] 47 Second hollow space

[0094] 54 First secondary piston rod

[0095] 56 Second secondary piston rod

[0096] 58 Second component opening

[0097] 60 First component opening

[0098] 100 Vehicle

[0099] 102 Pneumatic braking system

[0100] 104 Pipeline leading to the wheel

[0101] 106a Wheel (right front)

[0102] 106b Wheel (right rear)

[0103] 106c Wheel (left front)

[0104] 106d Wheel (left rear)

[0105] 108 Central module

[0106] 110 Engine

[0107] 201 First torque transmission and alignment device

[0108] 209 Needle roller bearing (first eccentric)

[0109] 211 (First) protrusion on the first eccentric

[0110] 212 (Second) protrusion on the first eccentric

[0111] 213 Hole on the first eccentric

[0112] 221 Second torque transmission and alignment device

[0113] 222 (Third) protrusion on the second eccentric

[0114] 223 Hole on the second eccentric

[0115] 229 Needle roller bearing (second eccentric)

[0116] 300 Cap screw

[0117] 301 Flange

[0118] 302 Recess

[0119] 303 Pin

[0120] The second hole on the 304 first eccentric member

[0121] The second hole on the 305 second eccentric member

[0122] The rotation axis of the A drive shaft

[0123] B1 The first central axis

[0124] B2 The second central axis

Claims

1. A piston pump (1), comprising: A pump housing (2), the pump housing (2) having piston means (8) connected to a drive shaft (10), the drive shaft (10) causing the piston means (8) to move when driven, wherein the piston means (8) comprises: A first primary piston (12), the first primary piston (12) being slidably disposed in a first primary cylinder (14) formed in the pump housing (2); A first secondary piston (16), the first secondary piston (16) being slidably disposed in a first secondary cylinder (18) formed in the first primary piston (12); A second primary piston (40), the second primary piston (40) being slidably disposed in a second primary cylinder (42) formed in the pump housing (2); A second secondary piston (44), the second secondary piston (44) being slidably disposed in a second secondary cylinder (46) formed in the second primary piston (40); Wherein the drive shaft (10) comprises a first eccentric member (20) and a second eccentric member (22), the first eccentric member (20) and the second eccentric member (22) being phase-shifted by 180°, and Wherein the first secondary piston (16) comprises a first secondary piston rod (54), and the second secondary piston (44) comprises a second secondary piston rod (56), Characterized in that the first primary piston (12) and the second secondary piston rod (56) are mounted on the second eccentric member (22) and directly driven by the second eccentric member (22), and The first secondary piston rod (54) and the second primary piston (40) are mounted on the first eccentric member (20) and directly driven by the first eccentric member (20).

2. The piston pump (1) according to claim 1, wherein, The drive shaft (10) comprises a stud (21), the first eccentric member (20) and the second eccentric member (22) being mounted on the stud (21).

3. The piston pump (1) according to claim 2, wherein, At least one of the first eccentric member (20) and the second eccentric member (22) is fixedly mounted on the stud (21).

4. The piston pump (1) according to claim 2 or 3, wherein, At least one of the first eccentric member (20) and the second eccentric member (22) is threadedly engaged with the stud (21).

5. The piston pump (1) according to any one of claims 2 - 4, wherein, The first eccentric member (20) is provided with first torque transfer and alignment means (201), the first torque transfer and alignment means (201) being configured to engage corresponding second torque transfer and alignment means (221) provided on the second eccentric member (22) in a predetermined angular manner.

6. The piston pump (1) according to claim 5, wherein, The first torque transfer and alignment means (201) provided on the first eccentric member (20) comprises at least two protrusions (211, 212), and The second torque transfer and alignment means (221) provided on the second eccentric member (22) comprises at least a third protrusion (222), the at least third protrusion (222) being configured to cooperate with the at least first protrusion (211) and second protrusion (212) provided on the first eccentric member (20).

7. The piston pump (1) according to any one of claims 5 or 6, wherein, The first torque transmission and alignment device (201) provided on the first eccentric member (20) and the second torque transmission and alignment device (221) provided on the second eccentric member (22) are located near the stud (21).

8. The piston pump (1) according to any one of claims 2-7, wherein, A nut (23) is provided on the stud (21), and the nut (23) is threadedly engaged with the stud (21) and forms a contact force transmission engagement with the second eccentric member (22).

9. The piston pump (1) according to claim 1, wherein, The drive shaft (10) includes a cap screw (300), and the first eccentric member (20) and the second eccentric member (22) are mounted on the cap screw (300).

10. The piston pump (1) according to claim 9, wherein, At least one of the first eccentric member (20) and the second eccentric member (22) is fixedly mounted on the cap screw (300).

11. The piston pump (1) according to any one of claims 9 or 10, wherein, At least one of the first eccentric member (20) and the second eccentric member (22) is threadedly engaged with the cap screw (300).

12. The piston pump (1) according to any one of claims 9-11, wherein, The second eccentric member (22) is provided with a flange (301), and the flange (301) is configured to cooperate with a recess (302) provided on the first eccentric member (20).

13. The piston pump (1) according to claim 12, comprising a pin (303), the pin (303) being configured to fixedly couple the flange (301) provided on the second eccentric member (22) to the recess (302) provided on the first eccentric member (20).

14. A method for installing a piston pump (1) according to any one of claims 1 - 8, comprising the following steps: - Mounting the first secondary piston rod (54) and the second primary piston (40) on the first eccentric member (20); - Press - fitting the drive shaft (10) into the first eccentric member (20); - Inserting the first secondary piston rod (54), the second primary piston (40), the first eccentric member (20), and the drive shaft (10) into the pump housing (2); - Mounting the second eccentric member (22) on the drive shaft (10) and aligning the second eccentric member (22) with the first eccentric member (20); - Mounting the first primary piston (12) and the second secondary piston rod (56) on the second eccentric member (22).

15. A vehicle (100), in particular a passenger vehicle or a commercial vehicle, comprising a piston pump (1) according to any one of claims 1 - 13.

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