DE102017221955B4 - Wheel suspension for a vehicle with a level adjustment - Google Patents

Abstract

Wheel suspension for a vehicle with level adjustment, with a support spring (7) designed as a helical compression spring, which is supported between a body-side spring support (11) and an axle-side spring support (9), and with an adjusting device (13) for height adjustment of a vehicle body (3) , characterized in that the actuating device (13) has a sliding guide (15) with a helical thread (17) on a first of the two spring supports (9, 11), which turns into an end turn (19) supported on the first spring support (11) the suspension spring (7) is screwed in, and that when performing a level adjustment, the adjusting device (13) actuates the suspension spring (7) in rotation, whereby either the end turn (19) is screwed out of the sliding guide (15) in a screwing movement, while increasing the between the spring supports (9, 11) effective suspension spring wire length, or the end turn (19) is screwed into the sliding guide (17), namely u nter reduction of the length of the suspension spring wire between the spring supports (9, 11).

Description

The invention relates to a wheel suspension for a vehicle with a level adjustment according to the preamble of claim 1.

The static and dynamic load of a vehicle body is typically mainly supported by the suspension springs on the vehicle axles during driving. The damper extension force of the shock absorber and the clamping forces of the axle bearings also have a slight effect. In the case of passenger cars, the suspension springs are commonly implemented as spiral springs or helical compression springs made from wound spring wire. The ends of the wire lie horizontally in the spring pads at the top and bottom of the vehicle. In conventional vehicles with a defined spring stiffness, the static vehicle stand height results from the weight of the load.

Depending on the conditions in which the vehicle is used, there are different requirements for the standing height of the vehicle: There is a requirement that the standing height of the vehicle be as low as possible at high vehicle speeds in order to reduce aerodynamic drag. On the other hand, at low vehicle speeds, for example on uneven terrain, there is a requirement for the greatest possible vehicle standing height in order to provide more ground clearance. Vehicles without a level adjustment system cannot meet these different requirements.

Against this background, a generic wheel suspension has a level control or level adjustment system, for example an air spring, an electric or a hydraulic level adjustment. As an alternative to this, the level adjustment can take place, for example, via an electric motor on a ball screw drive, as shown in FIG DE 10 2007 060 422 A1 is known. Further level adjustment systems are from the DE 101 57 713 A1 or from the DE 10 2008 060 477 A1 known.

Such level adjustment systems, however, work with a high expenditure of energy in order to raise or lower the vehicle body. Level control systems like the Niveaumat® from ZF Friedrichshafen do not require any energy. However, the Niveaumat® is only partially load-bearing. The direct application of force leads to high system pressures.

From the DE 199 16 017 B4 a spring device is known.

The object of the invention is to provide a wheel suspension for a vehicle with level adjustment, in which the energy expenditure for level adjustment can be reduced in a structurally simple manner compared to the prior art.

The object is achieved by the features of claim 1. Preferred developments of the invention are disclosed in the subclaims.

According to the characterizing part of claim 1, the level adjustment is implemented by an adjusting device which has a sliding guide with a helical thread on a first spring support. The sliding guide formed on the first spring support is screwed with the thread into an end turn of the suspension spring supported on the first spring support. In addition, the suspension spring can be rotatably mounted on the opposite second spring support about a suspension spring longitudinal axis. With such an arrangement, the level adjustment can be carried out as follows: The suspension spring is rotatably actuated in a first direction of rotation by means of the adjusting device, whereby the end turn of the suspension spring is screwed out of the sliding guide over a length of wire in a screwing movement. This increases the wire length of the suspension spring that is effective between the two spring supports, so that the vehicle body is raised.

Alternatively, when the suspension spring is rotated in the opposite direction, the suspension spring end turn is screwed into the sliding guide in a screwing movement over a length of wire. This reduces the length of the suspension spring wire effective between the two spring supports, so that the vehicle body is lowered.

According to the invention, the actuating force can thus be divided into two force components by turning off one side of the spiral spring or helical compression spring. A first force component is absorbed directly by the spring pad. The second force component can be used for level adjustment and / or an additional spring. It is relevant here that the suspension spring is rotatably mounted and can dip into the helical sliding guide of the first spring support over a defined area (that is to say over at least the above-mentioned wire length). The level adjustment according to the invention therefore results in a force translation in which the level adjustment only has to work against part of the weight of the vehicle body. As an alternative to the described upper spring support, an upper spring support with a conventional helical spring, which is mounted on a spindle (for example a recirculating ball screw), can be used. The forces of the spring support are to be passed on to the rest of the system by means of a lever or a pull / push element.

In a technical implementation of the invention, the first spring support assigned to the actuating device is the vehicle-upper, body-side spring support, while the second spring support, as the vehicle-lower, axle-side spring support, is rotatably mounted on a wheel guide element (for example a spring link of the wheel suspension).

The rotary actuation of the suspension spring required for level adjustment can be implemented in different ways. In a preferred embodiment variant, the actuating force required for the rotary actuation of the suspension spring can be introduced into the suspension spring via a tension / pressure element or a reversing lever. The tension / compression element can preferably be implemented as a push link chain by means of which the end turn located in the sliding guide, in particular its wire end, can be subjected to a tensile or compressive force. The line of action of the tensile or compressive force is preferably aligned in the direction of winding of the suspension spring.

With regard to the smoothest possible helical movement of the suspension spring, it is preferred if the pitch angle of the thread of the sliding guide corresponds essentially to the pitch angle of the suspension spring coils.

The drive unit interacting with the pull / push element can be implemented in different ways. The drive unit can preferably be integrated in an electronic chassis system and can be controlled automatically on the basis of current driving operating parameters. Automatic level regulation can preferably take place, in which an ideal vehicle height can always be automatically set in different operating situations, for example with different vehicle loads, different driving speeds, when towing a trailer or when cornering.

In a preferred embodiment variant, the drive unit has a hydraulic circuit that uses the energy that results from a relative movement between a vehicle wheel and the vehicle body during driving operation. For example, the hydraulic circuit can have a hydraulic cylinder that takes on both the function of a vibration damper and the function of a pump. From this, a piston rod can be connected to the push / pull element in a force-transmitting manner. Upward movements of the piston push hydraulic fluid out of the piston rod-side chamber into a pressure accumulator, which is also connected to the piston-bottom chamber via a valve. This allows the fluid to flow in and reduce the pressure difference in the chambers. The standing height of the vehicle increases until the piston reaches a stop or a control valve directly reduces the pressure difference between the chambers.

According to the invention, one of the two wire ends of the suspension spring is inserted into the sliding guide of the actuating device, which replaces a conventional spring pad. Due to the pitch angle of the thread of the sliding guide, the spring force is only partially introduced directly into the sliding guide. The remaining force is deflected by the push / pull element. One end of the pull / push element can also be positioned in the sliding guide. Its second end is coupled in a force-transmitting manner to the hydraulic circuit mentioned above or to another drive unit.

For example, the hydraulic circuit defined above can work as follows: If both control valves are closed, the portion of the weight of the vehicle body is supported by the piston of the hydraulic cylinder on the hydraulic fluid. If the vehicle is to be lowered, the first control valve must be opened. The hydraulic fluid thus flows from the chamber on the piston crown side into the chamber on the piston rod side until the piston has reached the lower stop or the first control valve is closed because the vehicle has been sufficiently lowered.

Dynamic wheel loads result from driving over uneven roads and from lateral and longitudinal accelerations. These superimpose positively and negatively fluctuating static weight and can be used to lift the vehicle.

In a technical implementation, a standing height sensor and a control unit are also required and must be installed at a suitable location. The realizable level of adjustment depends on the dimensions of the sliding guide and the hydraulic cylinders. Optionally, the total spring rate of the system can be adjusted using an elastic element between the suspension spring and the tension / compression element.

An exemplary embodiment of the invention is described below with reference to the accompanying figures.

• 1 in einer schematischen Darstellung die Radaufhängung für ein zweispuriges Fahrzeug mit Niveauverstellung, bei der der Fahrzeugaufbau abgesenkt ist;
• 2 eine Ansicht entsprechend der 1 mit angehobenem Fahrzeugaufbau; und
• 3 eine grob schematische Darstellung der Niveauverstellung mit zugeordneter hydraulischer Antriebseinheit.

Show it:

• 1 in a schematic representation the wheel suspension for a two-lane vehicle with level adjustment, in which the vehicle body is lowered;
• 2 a view corresponding to the 1 with raised vehicle body; and
• 3 a roughly schematic representation of the level adjustment with the associated hydraulic drive unit.

In the 1 the suspension for a two-lane vehicle is shown to the extent that it is necessary for an understanding of the invention. Accordingly, the wheel suspension has a wheel carrier that is external to the vehicle in the transverse direction of the vehicle 1 on which a vehicle wheel 2 ( 3 ) is worn. The wheel carrier 1 is on the vehicle body via a handlebar association 3 hinged, with only one spring link from the link association 5 is shown on the one the vehicle body 3 load bearing spring 7th is supported.

The suspension spring 7th is in the figures a helical compression spring or spiral spring, which with its lower spring base on a lower spring support 9 and with its upper spring base on an upper spring support on the body side 11 is supported. The lower spring pad 9 is realized as a rotary spring plate, freely rotatable about a suspension spring longitudinal axis A on the spring link 5 is pivoted. The upper spring pad 11 is part of an actuating device 13 for level adjustment of the vehicle body 3 .

As from the 1 shows, the control device 13 on the upper spring support on the body side 11 a sliding guide 15th with a helical thread 17th on. Its gradient angle α ( 3 ) corresponds essentially to the pitch angle α of the coil spring coils. The helical thread 17th the sliding guide 15th the spring support on the body side 11 is in an end turn formed at the upper spring base 19th the suspension spring 7th screwed in. At the end of the wire 21st the end turn 19th the suspension spring 7th is a push link chain 23 ( 3 ) coupled, the instinctual with one in the 3 indicated drive unit 25th connected is. Via the push link chain 23 can the drive unit 25th a force Fs (tensile or compressive force) on the wire end 21st the final winding 19th the suspension spring 7th exercise. The actuating force Fs is in the thread direction of the thread turn 17th or in the winding direction of the suspension spring 7th aligned. When such an actuating force Fs is exercised, the suspension spring 7th rotary actuated. Depending on the direction of rotation, there is a screwing movement in which the end turn 19th over a wire length ΔI from the sliding guide 15th is unscrewed, while increasing the between the two spring pads 9 , 11 effective suspension spring wire length, so that the vehicle body 3 raises. In contrast, when the force is applied in opposite directions, the end turn becomes 19th over the wire length ΔI in the sliding guide 15th screwed in, while reducing the between the two spring pads 9 , 11 effective suspension spring support length, so that the vehicle body 3 is lowered.

In the 1 is the vehicle body 3 lowered to a vehicle standing height h ₁ and the body-side end turn 19th the suspension spring 7th by the wire length ΔI in the thread 17th the sliding guide 15th the upper spring pad 11 screwed in or pushed in. By applying a pressure force Fs to the wire end 21st the screwed-in end turn 19th the suspension spring 7th there is a rotary actuation and thus a helical movement of the suspension spring 7th clockwise. This will make the end turn 19th over the wire length ΔI from the sliding guide 15th unscrewed, making the vehicle body 3 on those in the 2 The vehicle stand height shown h _{2 is raised} .

If the vehicle body 3 starting from the one in the 2 is to be lowered again, the wire end 21st the end turn 19th acted upon by a thrust actuating force Fs, whereby the end turn 19th back into the sliding guide over the wire length ΔI 15th the spring position on the body side 11 screwed in and thus the one in the 1 condition shown is restored.

By means of the helical sliding guide 17th a force transmission is provided in which only part of the weight of the vehicle body has to be worked against. In this way, the level can be adjusted with greatly reduced energy consumption compared to the prior art.

In the 3 is the drive unit 25th realized by way of example as a hydraulic circuit that has a hydraulic cylinder 29 having. Its piston rod 33 is force-transmitting on the push / pull element 23 tied up. The piston 31 of the hydraulic cylinder 29 separates a working chamber on the piston rod side 37 from a working chamber on the piston bottom 39 and is between a high level stop 53 and a low level stop 55 adjustable. The two working chambers 37 , 39 are via a first hydraulic line 41 and a second hydraulic line 43 connected to one another, which are arranged in parallel to one another. In the first hydraulic line 41 is one of a landing gear system 51 controllable first control valve 47 arranged while in the second hydraulic line 43 both one of the landing gear system 51 controllable second control valve 49 as well as an accumulator 45 including a pressure measuring point 52 is arranged. In addition, both are in the piston 31 as well as in the second hydraulic line 43 Damper valves provided to realize a shock absorber function.

When the piston moves upwards 31 One of these damper valves opens a piston damper valve 57 , so that hydraulic fluid from the working chamber on the piston rod side 37 into the working chamber on the piston bottom side 39 flows. At the same time, an upper damper valve opens when the piston moves upwards 59 in the second hydraulic line 43 . The two damper valves 57 , 59 are coordinated so that the piston damper valve 57 opens later when the piston moves upwards. This results in a pumping effect in which the piston is moved using dynamic wheel loads 31 (and thus the vehicle body 3 ) up to the stop with the high-level stop 53 adjusted. Such dynamic wheel loads result, for example, from driving over uneven roads and from lateral and longitudinal accelerations. The second control valve is also used to enable the piston to move upwards 49 opened, whereby hydraulic fluid in the bottom-side working chamber 39 can flow.

When the piston moves downwards 31 (i.e. compression process) is the weight of the vehicle body 3 utilized. The first control valve is used for this 47 opened up, whereby hydraulic fluid from the bottom-side working chamber 39 into the working chamber on the piston rod side 37 can flow.

As an alternative to the embodiment variant described above, the pressure accumulator 45 operated with a compressor.

Claims (9)

Wheel suspension for a vehicle with level adjustment, with a support spring (7) designed as a helical compression spring, which is supported between a body-side spring support (11) and an axle-side spring support (9), and with an adjusting device (13) for height adjustment of a vehicle body (3) , characterized in that the actuating device (13) has a sliding guide (15) with a helical thread (17) on a first of the two spring supports (9, 11), which turns into an end turn (19) supported on the first spring support (11) the suspension spring (7) is screwed in, and that when performing a level adjustment, the adjusting device (13) actuates the suspension spring (7) in rotation, whereby either the end turn (19) is screwed out of the sliding guide (15) in a screwing movement, while increasing the between the spring supports (9, 11) effective suspension spring wire length, or the end turn (19) is screwed into the sliding guide (17), namely while reducing the length of the suspension spring wire effective between the spring supports (9, 11). Suspension after Claim 1 , characterized in that the suspension spring (7) is rotatably mounted on the second spring support (9) about a suspension spring longitudinal axis (A). Suspension after Claim 1 or 2 , characterized in that the first spring support (11) is the vehicle-upper, body-side spring support. Suspension after Claim 1 , 2 or 3 , characterized in that the actuating device (13) has a tension / pressure element (23) for the rotary actuation of the suspension spring (7), by means of which the end turn (19) located in the sliding guide (17) with a winding direction of the suspension spring (7) aligned tensile or compressive force (Fs) can be applied, and that the tension / compression element (23) can be actuated by means of a drive unit (25). Wheel suspension according to one of the preceding claims, characterized in that the pitch angle (α) of the thread (17) of the sliding guide (15) corresponds to the pitch angle (α) of the coil spring coils. Suspension after Claim 4 or 5 , characterized in that the drive unit (25) is integrated in an electronic chassis system (51) and can be controlled on the basis of current driving operating parameters, and that automatic level control takes place in different operating situations, i.e. with different vehicle loads, trailer operation, cornering , etc. an ideal vehicle height (h ₁ , h ₂ ) is always automatically adjustable. Suspension according to one of the Claims 4 to 6th , characterized in that the drive unit (25) has a hydraulic circuit that uses the energy that results from a relative movement between a vehicle wheel (2) and the vehicle body (3) during driving. Suspension after Claim 7 , characterized in that the hydraulic circuit has a hydraulic cylinder (29), the piston rod (33) of which is connected to the push / pull element (23) in a force-transmitting manner and the piston (31) of which separates a working chamber (37) on the piston rod side from a working chamber (39) on the piston bottom side , and that the two working chambers (37, 39) are connected to one another via a first hydraulic line (41) in which a first control valve (47) controllable by the chassis system (51) is arranged, and connected to one another via a second hydraulic line (43) in which both a second control valve (49) controllable by the chassis system (51) and a pressure accumulator (45) are arranged. Wheel suspension according to one of the preceding claims, characterized in that the piston (31) of the hydraulic cylinder (29) is adjustable between a high-level stop (53) and a low-level stop (55).

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