Pulsation-damped ball nut steering and steering system

Abstract

Ball nut steering of a cab-over-engine vehicle, including: a first and a second cylinder chamber (1, 8) for receiving a fluid and a first supply line (19) for conveying fluid from a pump (17) to the first cylinder chamber (1), a device (10, 13) for damping and / or calming pulsations of the fluid, wherein the device (10, 13) is arranged within the first cylinder chamber (1) and / or within the first supply line (19), wherein the first cylinder chamber (1) has a smaller volume for receiving the fluid compared to the second cylinder chamber (8), characterized by that the device (10, 13) has a bypass, wherein the bypass allows a fluid flow (5) from the ball nut steering bypassing the device (10, 13).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a ball nut steering system of a cab-over vehicle according to the preamble of claim 1 and a steering system for a vehicle with such a ball nut steering system. BACKGROUND OF THE INVENTION

[0002] Ball-nut steering systems are known in the art. These ball-nut steering systems have two cylinder chambers with different fluid holding volumes. Typically, there is a cylinder chamber with a small holding volume and a cylinder chamber with a large holding volume. The fluid is forced into these cylinder chambers by a pump, for example, a positive-displacement pump.

[0003] Ball-nut steering systems can be used for cab-over trucks, a truck where the steering mechanism is positioned in front of the steering axle, and cab-over trucks, a truck where the steering gear is located behind the front axle. Front-end trucks are typically used in Europe, while cab-over trucks are preferred in the USA. SUMMARY OF THE INVENTION

[0004] The operation of the pump always results in pulsation of the fluid. A large cylinder chamber has a higher level of pulsation dampening than a small cylinder chamber. The large mass within the large cylinder chamber results in greater inertia, which leads to better damping properties. Furthermore, the fluid, for example hydraulic oil, contains a certain amount of air. Air is characterized by high elasticity and compressibility and therefore improves the damping properties of the fluid. The large cylinder chamber contains a larger amount of air than the smaller cylinder chamber. This is also why the smaller cylinder chamber has a comparatively significant pulsation. Pulsation of the fluid can propagate via the mechanical connections to the steering wheel as oscillation or vibration, which the driver finds annoying.

[0005] DE 10 2014 119 039 A1 discloses a ball-and-nut steering system for a vehicle with two cylinder chambers for accommodating a fluid. Fluid is conveyed from a pump to the first cylinder chamber via a first supply line, and fluid is conveyed from the pump to the second cylinder chamber via a second supply line. The ball-and-nut steering system includes a device for dampening fluid pulsations, which can be arranged in a cylinder chamber or within a supply line.

[0006] DE 10 2005 023 315 A1 discloses a power steering device with a piston that separates two hydraulic chambers. The device includes two damper valves arranged in valve receptacles of a housing.

[0007] One task is therefore to largely dampen or suppress a pulsation of a fluid in a ball nut steering system, in particular the pulsation of the fluid in the smaller of the two cylinder chambers.

[0008] The object is achieved by a ball nut steering according to claim 1 and a steering system for a vehicle according to claim 11.

[0009] According to the invention, a ball nut steering system of a hood vehicle is provided, comprising: a first and a second cylinder chamber for receiving a fluid and a first supply line for conducting fluid from a pump to the first cylinder chamber, wherein the ball nut steering system comprises a device for damping and / or calming pulsations of the fluid, wherein the device is arranged within the first cylinder chamber and / or within the first supply line, wherein the first cylinder chamber has a smaller volume for receiving the fluid compared to the second cylinder chamber.

[0010] According to the invention, the device has a bypass, wherein the bypass enables a fluid flow from the ball nut steering bypassing the device.

[0011] The spiral, serpentine, or meandering shape of the fluid flow in the device increases the flow resistance between the steering valve and the cylinder chamber. With small channel cross-sections or long channel lengths in the device, a "hard point" can occur during deflection, particularly at low temperatures, depending on the increasing viscosity. Such a "hard point" should be avoided. By installing a bypass, the damping device can be bypassed in the event of fluid backflow from the ball-nut steering. This shortens the fluid path and avoids the "hard point."

[0012] A cab-over vehicle is a vehicle, particularly a truck, whose steering gear is located behind the front axle in the direction of travel. This means that the cylinder chambers of a cab-over vehicle ball nut steering system are swapped compared to a front-mounted vehicle ball nut steering system. This means that the smaller cylinder chamber of the cab-over vehicle is located where the larger cylinder chamber of the front-mounted vehicle is. Small cylinder chambers in particular cause problems due to pulsations emanating from the positive displacement pump, since the small fluid volume only dampens the pulsations to a limited extent. A damping device is therefore necessary to prevent vibrations in the steering wheel of the vehicle in question.The device according to the invention can be arranged in or near the smaller cylinder chamber and ensures such a long channel for the fluid in question that sufficient damping of the pulsations is possible.

[0013] According to the invention, a steering system for a vehicle is also provided, comprising a ball nut steering according to one of claims 1 to 10.

[0014] Exemplary embodiments are described in the dependent claims.

[0015] According to an exemplary embodiment of the invention, a ball nut steering system is provided, wherein the device is designed as a spiral, serpentine or meandering channel for the fluid flow to the first cylinder chamber and / or wherein the device is designed in a plane.

[0016] By designing a fluid flow in a spiral, serpentine, or meandering shape, it is possible to create a long path for the fluid to reach the cylinder chamber. By designing the device in a single plane, a space-saving design can be achieved.

[0017] In a further embodiment of the invention, a ball nut steering system is provided, wherein the device is designed as an insert for retrofitting and / or has webs for forming an intermediate space, wherein the intermediate space is provided for receiving a seal.

[0018] The tightness of the oil guide is a prerequisite for its damping function. Designing it as an insert allows for retrofitting.

[0019] According to an exemplary embodiment of the invention, a ball nut steering is provided, wherein the device is integrally connected to the ball nut steering.

[0020] An integral connection of the damping device with the ball nut steering enables cost-effective production.

[0021] According to a further embodiment of the present invention, a ball nut steering is provided, wherein the bypass is a sealing lip.

[0022] A sealing lip can be designed in such a way that when fluid flows into the ball nut steering, the sealing lip closes and when fluid flows out of the ball nut steering, the sealing lip opens and thus acts as a bypass to the damping device.

[0023] According to an exemplary embodiment of the invention, a ball nut steering assembly is provided, the assembly comprising a plate that is placed against walls of the ball nut steering assembly to provide a channel for the fluid.

[0024] If the device comprises a plate that can be placed on corresponding walls, the device can be manufactured cost-effectively because the walls of the device can be manufactured at the same time as the ball nut steering by a casting process.

[0025] In a further embodiment of the invention, a ball nut steering system is provided, wherein the device is designed as 1, 2, 3, 4, 5, 6, 7 or any number of obstacles, resulting in a spiral, a serpentine and / or a meandering formation of the fluid flow.

[0026] A channel cross-section in the device that is approximately constant over a defined distance can calm the fluid flow and thus dampen it.

[0027] According to a further embodiment of the present invention, a ball nut steering system is provided, wherein the device is designed to form a change in the direction of fluid flow, in particular a 180° turn.

[0028] According to an exemplary embodiment of the invention, a ball nut steering assembly is provided, wherein the fluid is an oil.

[0029] According to an exemplary embodiment of the invention, a ball nut steering is provided, wherein the device has a path length of 150 mm to 700 mm for the fluid and / or wherein the device has a cross section of 16 mm 2 up to 38 mm 2 for the fluid.

[0030] Through a distance of 150 mm to 700 mm and / or a cross section of 16 mm 2 up to 38 mm 2 For the fluid, optimal damping of the fluid can be achieved.

[0031] One idea of ​​the invention can be seen as providing a device which, in a ball-and-nut steering system for a cab-over vehicle, is suitable for extending the fluid supply, wherein the fluid is in particular oil, to the smaller of the two cylinder chambers in such a way that pulsation of the oil due to the positive displacement pump can be dampened or prevented. In addition, a "hard spot" should be prevented during rapid changes in steering direction (pressure changes). For this purpose, the device has a check valve or a bypass which allows the oil flow out of the ball-and-nut steering system without passing through the damping device. When the oil flow flows into the ball-and-nut steering system, the check valve is closed. The check valve can, for example, be designed as a sealing lip.

[0032] The individual features can of course also be combined with each other, which can sometimes result in beneficial effects that go beyond the sum of the individual effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further details and advantages of the invention will become clear from the exemplary embodiments shown in the drawings. Fig. 1 a ball nut steering with a small cylinder chamber 1 and a large cylinder chamber 8, Fig. 2 a schematic representation of a displacement pump 17 with a steering valve 21 and a throttle 20, Fig. 3 a device 10 according to the invention for damping the pulsations resulting from the positive displacement pump, Fig. 4 shows an embodiment of the damping device 10 according to the invention in a cross-sectional view, wherein the device 10 is designed as an insert, wherein the wall 16 is permanently sealed to the housing by form-fitting (welding, soldering, gluing, forming), Fig. 5 shows an embodiment of the damping device 13 according to the invention in a cross-sectional view, wherein the device 13 is designed as an insert, in particular for retrofitting, wherein the wall 16 is sealed to the housing by a seal 11, Fig. 6 shows an embodiment of the damping device according to the invention in a cross-sectional view, wherein the wall 16 of the device is designed as an integral part of the ball nut steering, and the wall 16 is separated from the first cylinder chamber 1 by a plate 12, Fig. 7 a device for damping in snake form or meander shape and Fig. 8 obstacles 15 for diverting a fluid flow 5. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0034] Fig. 1 shows a ball-and-nut steering system with a smaller first cylinder chamber 1 on the steering spindle side and a large second cylinder chamber 8 opposite the steering spindle side. This type of ball-and-nut steering system is used in cab-over vehicles in which the steering gear is located behind the front axle. A fluid is pressed into the cylinder chambers 1, 8 by a pump. The pump causes pulsations in the fluid, which can ultimately lead to vibrations / oscillations in the steering wheel. Such pulsations are to be reduced or avoided. According to the invention, obstacles can be placed in the path of the fluid to achieve this, resulting in a calming / damping of the fluid. Such calming or damping devices 10 are preferably arranged in the area of ​​the smaller first cylinder chamber 1.The first cylinder chamber 1 can primarily be considered the starting point for fluid pulsations that lead to vibrations / oscillations in the steering wheel. Due to the smaller mass of the fluid in the first cylinder chamber 1 compared to the second cylinder chamber 8, the lower mass in the first cylinder chamber 1 tends to dampen the pulsations less. The fluid can consist of air or, for example, be an oil that contains a small amount of air. Air is highly compressible and elastic and therefore has good damping properties. Due to the smaller amount of air in the first cylinder chamber 1 compared to the second cylinder chamber 8, the first cylinder chamber 1 is more likely to be a source of pulsations that can lead to vibrations in the steering wheel.

[0035] Fig. Figure 2 shows a schematic representation of the positive displacement pump 17, which ensures the supply of fluid to a ball-nut steering system. A steering valve 21 and a throttle 20 are also shown. By throttling the line 19, the pulsations of the positive displacement pump 17 can be reduced. However, this results in a permanent increase in the pressure of the fluid in the positive displacement pump 17, and the fluid, for example, hydraulic oil, can be heated by the throttling to such an extent that cooling becomes necessary. Alternatively, expansion hoses and / or volumes can be arranged, which have similar disadvantages. According to the invention, a reduction in the pulsations should therefore only be carried out where it is most effective and where there are few or no disadvantages. This area is, in particular, the first cylinder chamber 1 (see Fig. 1). Damping only this section is also advantageous because flow through the first cylinder chamber 1 only occurs during steering, and therefore damping of the pulsations is only necessary then. Since trucks are usually driven in a straight line, damping, particularly of the fluid to the first cylinder chamber 1, can also provide effective damping with only minimal disadvantages.

[0036] Fig. Figure 3 shows a damping device 10, which can be arranged in particular in the small first cylinder chamber 1. A fluid flow 5 is introduced into the damping device 10 through inlet bores 2. Initially, the fluid flow 5 enters an annular channel 9. In a further step, the fluid flow 5 flows through a spiral-disk-shaped channel 6 and exits the damping device 10 through an opening 7. This damping device 10 can dampen the pulsations of the fluid flow 5.

[0037] Fig. 4 shows a device 10 for pulsation damping in a cross-sectional view, wherein the device 10 is designed as an insert and is permanently connected to the ball nut steering. The device 10 results in a defined extension of the supply path of the fluid flow 5 to the smaller first cylinder chamber 1 of the ball nut steering. The fluid flow 5 first passes through the inlet bores 2 into the annular channel 9 and from there into the spiral channel 6. In particular, the spiral channel 6 results in a long extension of the path of the fluid flow 5 to the small first cylinder chamber 1. This long path to the first cylinder chamber 1 results in a dampening of the pulsations of the positive displacement pump 17. The risk of a "hard spot" can be prevented by a "bypass". For this purpose, the device 10 has a sealing lip 14 that acts as a "valve".If the fluid flow 5 is pressed into the ball nut steering, the device 10 represents an obstacle, resulting in a higher pressure level in the annular channel 9 than in the first cylinder chamber 1, whereby the sealing lip 14 is pressed against the ball nut steering and ensures that the fluid flow 5 is guided through the device 10. If a fluid flow 5 is pressed out of the first cylinder chamber 1 of the ball nut steering, the device 10 represents an obstacle, resulting in a higher pressure level in the first cylinder chamber 1 than in the annular channel, whereby the sealing lip 14 is pressed away from the ball nut steering, whereby the fluid flow 5 can leave the ball nut steering, bypassing the device 10. The sealing lip 14 therefore acts as a bypass of the device 10, whereby a fluid flow 5 flowing in the direction of the first cylinder chamber 1 ensures that the sealing lip 14 rests against the ball nut steering.If an opposite fluid flow 5 is present, an overpressure results in the first cylinder chamber 1, whereby the sealing lip 14 opens, so that a fluid flow 5 from the ball nut steering is possible, bypassing the damping device.

[0038] Fig. Figure 5 shows the device 13 for pulsation damping, wherein the device 13 is designed as an insert. The device 13 has seals 11, so that retrofitting a ball-nut steering system is possible using the device 13 as an insert.

[0039] Fig. Figure 6 shows a further alternative embodiment of the invention, wherein the walls 16 of the pulsation damping device are integrally connected to the ball-nut steering. A plate 12 is provided to create a channel-like configuration for guiding the fluid flow 5.

[0040] Fig. Figure 7 shows a serpentine or meandering configuration of the damping device according to the invention, designed to create an elongated path for the fluid in question. This elongated path results in the damping of the fluid.

[0041] Fig. 8 shows an arrangement of obstacles 15 which cause the fluid flow 5 to become serpentine and thus allow the fluid to settle.

[0042] It should be noted that the term “comprising” does not exclude further elements or process steps, just as the terms “a” and “an” do not exclude multiple elements and steps.

[0043] The reference symbols used are for the sole purpose of increasing comprehensibility and are in no way to be considered as limiting, the scope of the invention being reflected in the claims. LIST OF REFERENCE SYMBOLS 1 first cylinder chamber 2 inlet holes 5 Fluid flow 6 spiral disc-shaped channel 7 Opening 8 second cylinder chamber 9 Ring Canal 10 Device according to the invention for pulsation damping as an integral part of the ball nut steering 11 Seal 12 Plate of the damping device according to the invention 13 damping device according to the invention, wherein the device is designed as an insert for retrofitting the ball nut steering 14 Sealing lip 15 Obstacle to fluid flow 16 Wall of the damping device 17 Pump, especially positive displacement pump 18 Engine 19 Fluid line 20 Throttle 21 Steering valve 22 Fluid tank 23 jetty 24 space

Claims

[1] Ball nut steering of a bonnet vehicle, comprising: a first and a second cylinder chamber (1, 8) for receiving a fluid and a first supply line (19) for conducting fluid from a pump (17) to the first cylinder chamber (1), a device (10, 13) for damping and / or calming pulsations of the fluid, wherein the device (10, 13) is arranged within the first cylinder chamber (1) and / or within the first supply line (19), wherein the first cylinder chamber (1) has a smaller volume for receiving the fluid compared to the second cylinder chamber (8), characterized by , that the device (10, 13) has a bypass, wherein the bypass enables a fluid flow (5) from the ball nut steering bypassing the device (10, 13). [2] Ball nut steering according to claim 1, characterized bythat the device (10, 13) is designed as a spiral, serpentine or meandering channel (6) for the fluid flow (5) to the first cylinder chamber (1) and / or wherein the device (10, 13) is designed in a plane. [3] Ball nut steering according to one of claims 1 or 2, characterized by that the device (10, 13) is designed as an insert for retrofitting and / or has webs (23) for forming an intermediate space (24), wherein the intermediate space (24) is provided for receiving a seal (11). [4] Ball nut steering according to one of the preceding claims, characterized by that the device (10, 13) is integrally connected to the ball nut steering. [5] Ball nut steering according to one of the preceding claims, characterized by that the bypass is a sealing lip (14). [6] Ball nut steering according to one of the preceding claims, characterized bythat the device (10, 13) comprises a plate (12) which is placed on walls (16) of the ball nut steering to provide a channel (6) for the fluid. [7] Ball nut steering according to one of the preceding claims, characterized by that the device (10, 13) is designed as 1, 2, 3, 4, 5, 6, 7 or any number of obstacles (15), resulting in a spiral, a serpentine and / or a meandering formation of the fluid flow (5). [8] Ball nut steering according to one of the preceding claims, characterized by that the device (10, 13) is designed to produce a change in the direction of fluid flow, in particular a 180° turn. [9] Ball nut steering according to one of the preceding claims, characterized by that the fluid is an oil. [10] Ball nut steering according to one of the preceding claims, characterized bythat the device (10, 13) has a path length of 150 mm to 700 mm for the fluid and / or wherein the device (10, 13) has a cross section of 16 mm 2 up to 38 mm 2 for the fluid. [11] Steering system for a vehicle comprising a ball nut steering according to one of the preceding claims.

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