Hydraulic steering system

Abstract

Hydraulic steering arrangement (1) comprising a supply connection arrangement with a supply connection (2) and a return connection (3), a working connection arrangement with two working connections (4, 5), a supply flow path (7) between the supply connection (2) and one of the working connections (4, 5), a return flow path (9) between the other of the working connections (5, 4) and the return connection (3), and a valve arrangement with a control piston / sleeve set, wherein the supply flow path (7) has a feed orifice (A4) and the return flow path (9) has a return orifice (A5), wherein a variable damping orifice (Adp) is arranged downstream of the feed orifice (A4) and upstream of the return orifice (A5), characterized in that the variable damping orifice (Adp) is formed by the control piston / sleeve set.

Description

[0001] The present invention relates to a hydraulic steering arrangement according to the preamble of claim 1.

[0002] US 2006 / 0248883 A1 describes a generic anti-jerk valve for hydraulically controlled systems. EP 2786915 A1 describes a hydraulic steering device. DE 3635162 A1 describes a control unit for a hydrostatic steering system. DE 10246882 A1 describes a leakage compensation arrangement in a control unit for a fully hydraulic steering system. DE 102017100190 A1 and DE 102018125051 A1 describe hydraulic steering arrangements.

[0003] When such a hydraulic steering system is used to steer a vehicle, hydraulic fluid is routed from the supply port via the main flow path to one of the working ports and from there to a steering motor. The hydraulic fluid displaced by the steering motor is returned to the return port via the other working port and the return line. The direction of steering is determined by the valve assembly. The valve assembly, in turn, can be controlled, for example, by the movement of a steering handwheel.

[0004] When such a steering system is used on an articulated vehicle, not only are the steered wheels moved, but also the angle between parts of the vehicle is changed. This means that large masses must be moved. This presents a problem because these large masses must be accelerated at the beginning of the steering movement and decelerated at the end.

[0005] In an articulated vehicle, oscillations can be observed during steering. These oscillations are particularly pronounced at the beginning and end of the steering process. Each change of direction causes a jerk, which is repeated with progressively less intensity until no potential energy remains. Such a jerk is unpleasant for a driver.

[0006] The invention is based on the objective of making the steering of an articulated vehicle more comfortable.

[0007] This problem is solved with a hydraulic steering arrangement according to claim 1.

[0008] The terms "downstream" and "upstream" refer to the flow of hydraulic fluid during steering. In other words, the hydraulic fluid flows through the supply orifice before reaching one of the two working ports and is returned to the other of the two working ports before reaching the return orifice. The damping orifice is therefore located after the supply orifice and before the return orifice. To simplify, the variable damping orifice is positioned between the two working ports, although other configurations are possible.

[0009] The variable damping orifice can reduce the intensity of the hydraulic fluid flow supplied to the steering motor via the working port during a sudden steering start. This is because a portion of the hydraulic fluid flow is diverted to the opposite side of the steering motor, upstream, or just before the return orifice. This reduces the impulse and inertial forces acting on the steering motor. Furthermore, because a portion of the forward flow is diverted to the opposite side of the steering motor or just before the return orifice, the pressure on the return side of the steering motor increases, counteracting the inertial forces on that side. A similar effect can be observed when the steering stops. When the steering stops, the steering motor continues to move in the previously set direction due to inertial forces.If the damping orifice is positioned between the two working ports, or downstream of the supply orifice and upstream of the return orifice, the pressure on the front side of the steering motor is reduced and on the return side is increased when the steering is stopped and the control piston / sleeve assembly returns to its neutral position. This also reduces the intensity of the jerk. Furthermore, it ensures that the same flow of hydraulic fluid passing through the supply orifice also passes through the return orifice, regardless of whether this return flow consists of fluid displaced by the steering motor or fluid that has passed through the damping orifice. Therefore, the parameters for the pressure drop across the return orifice do not change compared to a situation without a damping orifice. The back pressure, i.e., the pressure at the return orifice, can be maintained at a suitable level.

[0010] In one embodiment of the invention, the variable damping orifice is closed in the neutral position of the control piston / sleeve assembly. In the neutral position of the control piston / sleeve assembly, no movement of the steering motor should occur. When the variable damping orifice is closed, the hydraulic fluid cannot flow from one port of the steering motor to the other. The steering motor is jammed or held captive when the control piston / sleeve assembly is in the neutral position.

[0011] In one embodiment of the invention, the variable damping orifice is closed at maximum deflection of the control piston / sleeve assembly. At maximum deflection of the control piston / sleeve assembly, the flow of hydraulic fluid to one of the working ports is greatest, and the steering motor should be operating at its highest possible operating speed. In this situation, it is advantageous that no fluid can flow to the other side of the steering motor, which would reduce the steering speed. The purpose of the damping orifice being closed at maximum deflection is to prevent slippage in the "end position" (when the cylinder is in the end position, it should not be possible to turn the vehicle's steering wheel any further).

[0012] In one embodiment of the invention, the variable damping orifice opens when the deflection of the control piston / sleeve assembly is greater than the deflection at which the supply orifice and / or the return orifice open. In this way, hydraulic fluid is supplied to the steering motor before the variable damping orifice opens.

[0013] According to the invention, the variable damping orifice is formed by the control piston / sleeve assembly. The control piston / sleeve assembly already forms several orifices that serve to control the quantity and direction of the hydraulic fluid flow from the supply port to one of the working ports. It is possible to modify the control piston / sleeve assembly so that the variable damping orifice can also be arranged within it. This has the additional advantage that no further measures are required to open and close the variable damping orifice depending on the deflection of the control piston / sleeve assembly.

[0014] In one embodiment of the invention, a booster flow path is arranged parallel to the main flow path, with the booster flow path opening into the main flow path upstream of the damping orifice. This means that the hydraulic fluid supplied via the booster flow path is treated in the same way as the hydraulic fluid flowing through the main flow path.

[0015] In one embodiment of the invention, the amplifying flow path opens into the main flow path upstream of the inlet orifice. This means that the inlet orifice also controls the flow of hydraulic fluid from the amplifying flow path.

[0016] One embodiment of the invention will now be described with reference to the drawing, in which: Fig. Figure 1 schematically shows a hydraulic steering arrangement and Fig. 2 schematically the opening degrees of several in Fig. 1 of the depicted apertures shows.

[0017] Fig. Figure 1 schematically shows a hydraulic steering arrangement 1 with a supply connection arrangement, as known, for example, from DE10 2018 125 053. The supply connection arrangement has a supply connection 2 and a return connection 3. Furthermore, two working connections 4, 5 are provided, with the working connections 4, 5 forming a working connection arrangement. A steering motor 6 is connected to the working connections 4, 5.

[0018] The control arrangement 1 has a main flow path 7, which includes a main orifice plate A1 and a measuring motor 8. A first measuring motor orifice plate A2 is located upstream of the measuring motor 8, and a second measuring motor orifice plate A3 is located downstream of the measuring motor 8. The terms "upstream" and "downstream" refer to the flow direction through the main flow path 7 and the measuring motor 8. The main flow path 7 is connected to one of the working terminals 4 via a supply orifice plate A4. The other working terminal 5 is connected to a return path 9 via a return orifice plate A5.

[0019] The orifices A1, A2, A3, A4 and A5 are part of a valve arrangement formed by a control piston / sleeve set known in the prior art. The valve arrangement determines which of the two working ports 4, 5 is connected to the main flow path 7 and which of the working ports 5, 4 is connected to the return path 9.

[0020] The hydraulic steering assembly 1 can also have a booster flow path 10, which is connected to the supply port 2 and opens into the main flow path 7 between the supply orifice A4 and the second measuring motor orifice A3. The booster flow path 10 has a booster orifice AU, which is also formed in the control piston / sleeve assembly of the valve assembly and is controlled in a similar, but not necessarily identical, manner to the control of the main orifice A1.

[0021] In the present steering arrangement 1, a drain orifice Adr. is arranged between the main flow path 7 and the return path 9, more precisely between a point between the main orifice A1 and the first measuring motor orifice A2 and the return path 9.

[0022] A check valve 11 is arranged in front of the main orifice A1, which opens in the direction of the main orifice A1.

[0023] The main flow path 7 is connected to a relief valve 12, which branches off from a line 13 that connects the main flow path 7 downstream of the main orifice A1 to a load-sensing port 14 of a priority valve 15. The priority valve 15 controls the supply of hydraulic fluid from a tank 16 to the supply port 2. The hydraulic fluid is pumped by means of a pump 17.

[0024] Since the arrangement and construction of priority valve 15 are known from practical experience, it will not be described further. The same applies to valve 12 and the pressure relief valves, which are normally arranged in conjunction with working ports 4 and 5.

[0025] A variable damping orifice Adp is arranged downstream of the supply orifice A4 and upstream of the return orifice A5. The terms "downstream" and "upstream" refer to the flow of hydraulic fluid to and from the steering motor 6. In this case, the damping orifice Adp connects the main flow path 7 and the return path 9 between the supply orifice A4 and one of the working ports 4 on the one hand, and between the other working port 5 and the return orifice A5 on the other.

[0026] The damping orifice Adp is a variable orifice that is closed in the neutral position of the control piston / sleeve assembly. Furthermore, the variable damping orifice Adp is closed at maximum deflection of the control piston / sleeve assembly. This is in Fig. 2 schematically represented.

[0027] The control piston / sleeve assembly has an inner slide and an outer slide, the outer slide surrounding the inner slide and located in a bore of a housing. The inner and outer slides are rotatable relative to each other. Part of the inner and outer slides is connected to a steering control device, such as a steering wheel. The other part of the inner and outer slides is connected to part of the measuring motor. When the steering wheel (or other steering control device) is turned, the deflection between the inner and outer slides changes. This change causes certain apertures, as shown in Fig. Two are shown, one open and the other closed.

[0028] In Fig. Figure 2 shows the deflection on the horizontal axis and the degree of opening of the orifices on the vertical axis. In the present embodiment, the outlet orifice Adr is closed at the beginning of the deflection, while the main orifice A1, the amplification orifice AU, the supply orifice A4, the return orifice A5, and the two measuring motor orifices A2 and A3 are open. Hydraulic fluid flowing through the supply orifice A4 to a working port passes through the measuring motor 8 and drives it. The measuring motor 8 returns the angular position or deflection between the inner and outer slides to neutral, so that the outlet orifice Adr opens and the other orifices close.

[0029] As in Fig.As shown in Figure 2, the attenuating orifice Adp opens at a deflection greater than the deflection at which the main orifice A1 and the amplifying orifice AU open. Furthermore, the opening degree of the attenuating orifice Adp remains nearly constant over a large range of the deflection angle. The attenuating orifice Adp also acts as a choke, meaning its opening area is always smaller than the combined opening area of ​​the main orifice A1 and the amplifying orifice AU.

Claims

[1] Hydraulic steering arrangement (1) comprising a supply connection arrangement with a supply port (2) and a return port (3), a working port arrangement with two working ports (4, 5), a supply flow path (7) between the supply port (2) and one of the working ports (4, 5), a return flow path (9) between the other of the working ports (5, 4) and the return port (3), and a valve arrangement with a control piston / sleeve set, wherein the supply flow path (7) has a supply orifice (A4) and the return flow path (9) has a return orifice (A5), wherein a variable damping orifice (Adp) is arranged downstream of the supply orifice (A4) and upstream of the return orifice (A5), characterized by , that the variable damping orifice (Adp) is formed by the control piston / sleeve set. [2] Hydraulic steering device according to claim 1, characterized by, that the variable damping orifice (Adp) is closed in the neutral position of the control piston / sleeve set. [3] Hydraulic steering device according to claim 1 or 2, characterized by that the variable damping orifice (Adp) is closed at maximum deflection of the control piston / sleeve set. [4] Hydraulic steering device according to any one of claims 1 to 3, characterized by , that the variable damping orifice (Adp) opens when the deflection of the control piston / sleeve set is greater than a deflection of the control piston / sleeve set at which the feed orifice (A4) and / or the return orifice (A5) open. [5] Hydraulic steering device according to any one of claims 1 to 4, characterized by , that a gaining current path (10) is arranged parallel to the main current path (7), wherein the gaining current path (10) leads into the main current path (7) upstream of the attenuation orifice (Adp). [6] Hydraulic steering device according to claim 5, characterized by , that the amplification current path (10) leads upstream of the supply aperture (A4) into the main current path (7).

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