Vibration damper with pump assembly

Abstract

A vibration damper with a working cylinder which is subdivided by an axially movable piston on a piston rod into a first working chamber and a second working chamber which are filled with a damping medium, wherein the vibration damper has at least one compensation reservoir for receiving damping medium which is expelled by the piston rod, wherein there is a flow connection between the two working chambers in which a pump assembly is incorporated, the pump assembly having fluctuations in the delivery volume at a constant power supply, wherein, in addition to the at least one compensation reservoir, at least one pulsation accumulator is arranged in the flow connection, the volume and spring stiffness of the pulsation accumulator being matched to the frequency of the fluctuations in the delivery volume of the pump assembly.

Description

Technical Field

[0001] This invention relates to a vibration damper. Background Technology

[0002] DE 10 2011 101 746 A1 discloses a vibration damper having a pump assembly within a flow connection between two working chambers. The pump assembly has two delivery directions. According to... Figure 3 In one embodiment, a hydraulic clearance is implemented within the piston fastened to the piston rod 7. This hydraulic clearance is used to dampen the excitation below a defined amplitude. The hydraulic clearance includes a damping medium compensation chamber with an axially movable partition piston. Such a damping medium compensation chamber is also commonly used in conventional vibration dampers. The volume of this damping medium compensation chamber is approximately 1360 mm². 3 Up to 2270mm 3 This depends on the vehicle type. Even under low pressure loads, the separator piston can perform a displacement motion. The displacement motion of the separator piston begins at a pressure level much lower than the opening motion of the damping valve. This operational behavior is typical of amplitude-dependent damping force characteristics.

[0003] DE 10 2015 2218 490 A1 discloses a vibration damper having a pump assembly in which an accumulator device is connected to a flow connection between two working chambers. This flow connection incorporates a pump assembly having two delivery directions. The accumulator device has a pressure preload designed to assist the delivery operation of the pumping device. The accumulator has a correspondingly large volume. If the vibration damper does not require pumping, the pumping device can fill the accumulator device and pressurize it.

[0004] A fundamental problem with vibration dampers incorporating pump assemblies is that the pulsating delivery of the pump assembly generates noise. Although gear pumps are used in many cases, pump operating noise can still be heard, especially during relatively long turns when there is low excitation in some road sections.

[0005] One solution is to spatially separate the pumping unit from the vibration damper and introduce noise isolation. For example, noise isolation can be achieved through very soft support elements for the vibration damper. However, this also results in a loss of response behavior from the vibration damper. This characteristic is particularly noticeable in situations where the vehicle is attempting to evade control.

[0006] The purpose of this invention is to optimize the impact of pumping device pulsation on vehicle interior noise emissions. Summary of the Invention

[0007] In addition to at least one compensating reservoir, this is achieved by arranging at least one pulsating accumulator within the flow connector, the volume and spring stiffness of which are matched to the fluctuation frequency of the conveying volume.

[0008] Because of the limited elasticity and the fact that the cylinder of the vibration damper is not pulsated by the pump assembly, the pulsating accumulator reduces noise. The pulsating accumulator is significantly smaller than the compensating reservoir or hydraulic backlash in the cited prior art. For example, assuming a piston rod diameter of 17 mm and a stroke of 100 mm, the compensating reservoir must have approximately 22690 mm. 3 The minimum working volume. With a piston rod diameter of 17mm and a piston stroke of 6mm, the hydraulic clearance is calculated to be approximately 1360mm. 3 The working volume of the pulsating accumulator is approximately 5 mm². 3 Up to 15mm 3 Therefore, the pulsation damper is a very compact component, and moreover, it hardly creates any idle elements or backlash in the hydraulic system.

[0009] According to the advantageous dependent claim, the vibration damper has a separate pulsation accumulator for each working chamber. This allows the impact of pulsation on both delivery directions of the pump assembly to be minimized.

[0010] As a further improvement of the invention, the pulsating accumulator has two accumulator chambers separated from each other by a separating piston, and in each case, one accumulator chamber is connected to a working chamber of the working cylinder. In principle, two separate pulsating accumulators could also be provided, but combining them simplifies the flow path and reduces construction complexity.

[0011] To simplify the generation of the piston return force, the accumulator chamber is connected to the delivery side of the pump assembly and the suction side working chamber of the vibration damper. Even in the suction side working chamber, there is always overpressure relative to atmospheric pressure. Therefore, based on the working pressure in the suction side working chamber, the force of the return spring and the hydraulic return force are combined. As a result, the return spring can be made weaker.

[0012] To optimize the response behavior of the pulsating accumulator, the pulsating accumulator's separator piston has a gap seal between the accumulator chamber and the rear chamber. To minimize static friction on the separator piston, a leakage rate is intentionally allowed at the separator piston.

[0013] To simplify the determination of the size of the return spring used for the separating piston, the separating piston of the pulsating accumulator has a stop portion that determines the maximum working volume of the accumulator chamber. The working volume is not the total volume of the pulsating accumulator, but rather the product of the top side area of ​​the separating piston and the working stroke of the separating piston.

[0014] Another measure to minimize noise emissions is to implement at least one pulsating accumulator in the housing of the pump assembly. This achieves the shortest possible connection for the pulsating accumulator, ensuring that structurally transmitted noise is not transmitted from the pump assembly to other components, and therefore, transmission components (such as hose connections) do not perform any expansion movement.

[0015] To achieve a compact arrangement and simple flow path within the pump assembly, the pump assembly has an outlet chamber for each delivery direction, and these outlet chambers are arranged adjacent to each other in the housing, wherein the pulsating accumulator is arranged within the housing in a lateral region shared with the outlet chambers.

[0016] Preferably, the pulsating accumulator is aligned in a radially offset manner relative to the main axis of the housing in order to keep the total length of the housing as small as possible.

[0017] As a further measure in this regard, the pump assembly has a pump chamber, the bottom region of which extends perpendicularly to the main axis of the pump assembly, wherein the pulsating accumulator is arranged in a plane parallel to the bottom region.

[0018] Optionally, at least one flow connection between the pulsation accumulator and the pump assembly can be configured such that its cross-section is adjustable by a valve. In cases where the pump assembly's delivery capacity is particularly low or very high, the pulsation effect does not affect noise emissions because the noise frequency does not appear in an interfering manner within the vehicle. To achieve optimal system dynamics, for example, the pulsation accumulator can be deactivated. However, a limit can also be set such that the pulsation accumulator only cuts off the peak value of the pulsation, and therefore can be designed to be smaller than when there is no valve. Attached Figure Description

[0019] The invention will be explained in more detail with reference to the following accompanying drawings.

[0020] In the attached diagram:

[0021] Figure 1 An equivalent diagram of a vibration damper with a pump assembly is shown.

[0022] Figure 2 It shows Figure 1 Alternative variants

[0023] Figure 3 It shows according to Figure 1 pulsating accumulator as a separate component

[0024] Figures 4 to 7 The pulsating accumulator within the pump assembly is shown.

[0025] Figure 8 It shows the basis Figure 7 Alternative variants

[0026] List of reference numerals

[0027] 1 Vibration damper 61 end surface

[0028] 3. Working cylinder body 63 bottom

[0029] 5 Pistons 65 Bottom

[0030] 7 Piston rod 67 Flange

[0031] 9 First Compensation Chamber 69 Connecting Part

[0032] 11 Second compensation chamber 71 Shell

[0033] 13 Compensation reservoir 73 Shell section

[0034] 15 Adjustable damping valve 75 Pump chamber

[0035] 17 Adjustable damping valve 77 Support and positioning component

[0036] 19 Flow connectors 79 Support and positioning components

[0037] 21 Check valve 83 Lateral axis

[0038] 23 Check valve 85 Second transverse axis

[0039] 25 Additional flow connectors 87 Exit chamber

[0040] 27 Pump assembly 89 Outlet chamber

[0041] 29 Pump 91 Main shaft

[0042] 31 Pump driver 93 Valve

[0043] 33 Pulsating Accumulator

[0044] 35 Pulsating Accumulator

[0045] 37 Delivery Chamber

[0046] 39 Delivery Chamber

[0047] 41 Third flow connector

[0048] 43 Accumulator chamber

[0049] 45 Accumulator chamber

[0050] 47. Divider Piston

[0051] 49. Shell

[0052] 51. Return spring

[0053] 53. Return spring

[0054] 55 Gap sealing part

[0055] 57. Rear Chamber

[0056] 59 End surface Detailed Implementation

[0057] Figure 1 An equivalent diagram of a vibration damper 1 with a working cylinder 3 is shown, which is subdivided by an axially movable piston 5 on a piston rod 7 into a first working chamber 9 and a second working chamber 11 filled with damping medium. Whether this is a single-tube or double-tube vibration damper, both known per se, is irrelevant here. The vibration damper 1 has at least one compensation reservoir 13 for receiving the damping medium discharged from the piston rod 7. In this exemplary embodiment, the compensation reservoir 13 is functionally arranged between two adjustable damping valves 15, 17, wherein, in the outflow direction from the adjustable damping valves 15, 17, the compensation reservoir 13 is connected to a flow connection 19 between the two working chambers 9, 11. By way of example, check valves 21, 23 are hydraulically connected in parallel with each adjustable damping valve 15, 17 such that the adjustable damping valves 15, 17 generate damping force only in one operating direction of the vibration damper 1. There is absolutely no need to arrange the adjustable damping valves 15 and 17 in a way that separates them from the working cylinder 3.

[0058] Between the two working chambers 9 and 11, there is an additional flow connection 25, incorporating a pump assembly 27 including a pump 29 and a pump driver 31. This additional flow connection 25 is not necessarily spatially separated from the first flow connection 19, which has adjustable damping valves 15 and 17.

[0059] Pump assembly 27 includes an alternating delivery pump 29, particularly a gear pump. In many types of pumps, despite a constant power supply, there are fluctuations in the delivery volume. These fluctuations cause noise that can be transmitted to the vehicle body (not shown). To minimize this noise, in addition to the at least one compensating reservoir 13, at least one pulsating accumulator 33 is arranged in an additional flow connection 25, the volume and spring stiffness of which are matched to the frequency of the fluctuations in the delivery volume of pump assembly 27.

[0060] As can be seen from the equivalent diagram, pump assembly 27 has two delivery directions to selectively fill additional damping medium volumes into the two working chambers 9, 11 or simply maintain the operating pressure. For this purpose, vibration damper 1 has separate pulsation accumulators 33, 35 for each working chamber 9, 11. Pulsation accumulators 33, 35 are hydraulically connected in parallel with the delivery chambers 37, 39 of pump 29 in a third flow connection 41. In this equivalent diagram, pulsation accumulators 33, 35 have two accumulator chambers 43, 45, which are separated from each other by a separating piston 47. Therefore, the two pulsation accumulators 33, 35 are arranged in a common housing 49. Accumulator chambers 43, 45 are each connected to the working chambers 9, 11 of the working cylinder 3. Return springs 51, 53 are clamped on both sides of the separating piston 47. Therefore, starting from the pump's delivery chamber, hydraulic pressure acts on the separating piston 47, where this pressure is based on the pressure level in the connected working chambers 9, 11. However, the pulsating accumulators 33, 35 also have connections via flow connections to the suction chamber within the vibration damper 1 (that is, the suction chamber from which the pump assembly 27 delivers during transient operation). Therefore, in addition to the return springs 51, 53, the separating piston 47 is subjected to pressure based on the pressure level of the suction chamber. Consequently, the dimensions of the return springs 51, 53 can be determined to be significantly weaker than when there is no pressure contribution from the suction chamber. The return springs 51, 53 are designed such that the pressure differential established by the pump 29 is supported.

[0061] To optimize the response behavior of the pulsating accumulators 33 and 35, the separating piston 47 of the pulsating accumulators 33 and 35 preferably has a gap seal 55 between the accumulator chamber 43 and the rear chamber 57 in which return springs 51 and 53 are arranged. In the case of a combination of two pulsating accumulators 33 and 35, each of the two chambers is either an accumulator chamber or a rear chamber, depending on the direction of operation. Furthermore, the separating piston 47 is made of plastic. As the mass decreases accordingly, the natural frequency of the pulsating accumulators 33 and 35 will increase to a speed or delivery range that the pump cannot reach or is selectively unable to reach during normal operation.

[0062] Figure 2 The two pulsating accumulators 33 and 35 are shown to be completely independent of each other in terms of spatial connection. The choice between the two variants depends on the installation space conditions in a particular application. An advantage of this variant is that the return springs 51 and 53 are not interdependent in their spring forces.

[0063] Figure 3 It shows according to Figure 1The pulsating accumulator is a separate component. A separating piston 47 is mounted axially movable within the housing 49. The separating piston 47 has a T-shaped cross-section, where end faces 59 and 61 each define a stop for the maximum displacement stroke of the separating piston 47 within the pulsating accumulators 33 and 35, thus also defining the maximum working volume of the accumulator chamber. The working volume is calculated by multiplying the outer annular space by the maximum displacement stroke of the separating piston 47 from its initial position without movement of the pump assembly 27. Therefore, the total storage volume of the housing 49 can be significantly larger to also provide mounting space for the return springs 51 and 53. The return springs 51 and 53 are clamped in their respective working directions between the bottom 63 and 65 of the housing 47 and the circumferential flange 67 forming the separating piston 47.

[0064] Advantageously, the return spring is designed so that in the center position, i.e., when the pump has not established any pressure differential, the return spring does not apply any preload force to the separator piston. As a result, only the stiffness of the return spring is related to each pressure direction. The lowest possible stiffness improves the isolation behavior of the device. In the case of mutually preloaded return springs, the total stiffness is related, and the isolation effect is weakened.

[0065] At least two connecting portions 69 are provided in the housing 47 for the flow connection 41 to the pump 29.

[0066] Will Figures 4 to 7 Together, a design example of pump assembly 27 is shown, wherein at least one pulsating accumulator 33, 35 is implemented in the housing 71 of pump assembly 27. Figure 4 and Figure 5 For simplicity, the pump driver 31 is omitted from the diagram. The pump chamber 75 of the pump 29 is located in the end section 73 of the housing. Figure 5 The support positioning elements 77 and 79 for one of the gears (not shown) of this pump, which is designed as a gear pump, can be seen. The suction chamber and the delivery chamber are considered as pump chamber 75.

[0067] According to Figure 7 In the plan view, the support positioning element 77 of one of the gears used can be seen. The outer surface of the pump chamber 75 forms support positioning elements for the other gears of the pump. A first transverse axis of the housing 71 extends vertically through the support positioning element 77 in the plane of section. A second transverse axis 85 extends through the support positioning element 77 at a right angle to the first transverse axis. The two transverse axes 83 and 85 are in... Figure 7The cross-sectional plane is divided into four quadrants. Pump assembly 27 has one outlet chamber 87, 89 for each delivery direction. The first outlet chamber 87 extends within the first quadrant Q1 and the fourth quadrant Q4. The second outlet chamber is arranged as a mirror image of the second transverse axis 85 and extends within the second quadrant Q2 and the third quadrant Q3. Thus, the two outlet chambers 87, 89 are arranged adjacent to each other within the housing 71. The housing area for the pulsating accumulators, formed by the housing of the pump assembly, is arranged in the lateral regions shared with the outlet chambers, namely the first quadrant Q1 and the second quadrant Q2. Thus, the pulsating accumulators 33, 35 are aligned in a radially offset manner relative to the main axis 91 of the housing 71. The main axis is formed by the longitudinal axis of pump assembly 27, which in turn has the same alignment with the support positioning members 77, 79 of the pump gears. As can be clearly seen, the flow connection 41 between the pulsating accumulators 33, 35 and the outlet chambers 87, 89 is formed by a very short straight channel that can be manufactured very easily. Furthermore, the pulsation accumulators 33 and 35 are placed in a very stable cover area of ​​the pump assembly 27, thereby ensuring that the housing wall does not experience related vibrations. Figure 4 and Figure 7 Upon closer inspection, it is evident that the pump chamber 75, which also includes two outlet chambers 87 and 89, extends at right angles to the drive axis or main axis 91 of the pump assembly 27 with its bottom surface, wherein the pulsating accumulators 33 and 35 are arranged in a plane parallel to the bottom surface of the pump chamber 75.

[0068] Figure 8 Based on Figure 7 The diagram illustrates this. Furthermore, the pump assembly 27 has a valve 93 for setting the cross-section of the flow connection 41 between the pulsating accumulator 33 and the outlet chamber 87. In the case of a combined embodiment with two pulsating accumulators 33, 35, a single valve 23 is sufficient. This allows control of the inflow to the pulsating accumulator in one delivery direction of the pump assembly 27 and control of the outflow from the pulsating accumulator in the other delivery direction. The controller can optionally be configured as an on / off valve or a continuously adjustable valve. This allows the pulsating accumulators 33, 35 to be deactivated or their impact reduced when not needed.

Claims

1. A vibration damper (1) having a working cylinder (3), said working cylinder being subdivided by an axially movable piston (5) on a piston rod (7) into a first working chamber (9) and a second working chamber (11) filled with a damping medium, wherein, The vibration damper (1) has at least one compensation reservoir (13) for receiving the damping medium discharged by the piston rod (7), wherein an additional flow connection (25) is between the two working chambers (9; 11), in which a pump assembly (27) is incorporated, the pump assembly exhibiting fluctuations in delivery volume under constant power supply, characterized in that, in addition to the at least one compensation reservoir (13), at least one pulsating accumulator (33; 35) is arranged within the additional flow connection (25). The volume and spring stiffness of the pulsating accumulator (33; 35) are matched to the fluctuation frequency of the delivery volume of the pump assembly (27). The vibration damper (1) has a separate pulsating accumulator (33; 35) for each working chamber (9; 11), the pulsating accumulator having two accumulator chambers (43; 45) separated from each other by a separating piston (47), and in each case, one accumulator chamber (43; 45) is connected to one working chamber (9; 11) of the working cylinder (3).

2. The vibration damper according to claim 1, characterized in that, The accumulator chambers (43; 45) are connected to the delivery side of the pump assembly (27) and the suction side working chamber of the vibration damper (1).

3. The vibration damper according to claim 1, characterized in that, The pulsating accumulator (33; 35) has a gap seal (55) between the accumulator chamber (43; 45) and the rear chamber (57).

4. The vibration damper according to claim 1, characterized in that, The pulsating accumulator (33; 35) has a separating piston (47) with a stop (59; 61; 63; 65) which determines the maximum working volume of the accumulator chamber.

5. The vibration damper according to claim 1, characterized in that, The at least one pulsating accumulator (33; 35) is implemented in the housing (71) of the pump assembly (27).

6. The vibration damper according to claim 5, characterized in that, The pump assembly (27) has an outlet chamber (87; 89) for each delivery direction, the outlet chambers being arranged adjacent to each other in the housing (71), wherein the pulsating accumulator (33; 35) is arranged in the housing (71) in a lateral region shared with the outlet chambers.

7. The vibration damper according to claim 6, characterized in that, The pulsating accumulators (33; 35) are aligned in a manner that is radially offset relative to the main axis (91) of the housing (71).

8. The vibration damper according to claim 7, characterized in that, The pump assembly (27) has a pump chamber (75) with the bottom region of the pump chamber extending at a right angle to the main axis of the pump assembly (27), wherein the pulsating accumulator (33; 35) is arranged in a plane parallel to the bottom region.

9. The vibration damper according to any one of claims 2 to 8, characterized in that, The cross section of at least one third flow connection (41) between the pulsating accumulator (33; 35) and the pump assembly (27) can be adjusted by a valve (93).

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