DE102018121235A1 - Process for producing a torsion bar and torsion bar for an active roll stabilizer - Google Patents

Abstract

The invention relates to a method for producing a torsion bar (2) for an active roll stabilizer (1) of a motor vehicle, the torsion bar (2) comprising a torsion bar spring (3) and a flange (4), the flange (4) being two in one piece with one another Connected flange components (5, 6) made of different materials, namely a ring element (5) made of a first material and a tube element (6) made of a second material, at least one of the two flange components (5, 6) being initially produced by forging and immediately after forging is connected to the other of the two flange components (6, 5) by diffusion welding, the flange (4) then being subjected to at least one heat treatment for setting a material structure for magnetic coding, after which at least the tubular element (6) is magnetically coded, and finally the tubular element (6) is connected in a rotationally fixed manner to an end section of the torsion bar spring (3) which is to form the torsion bar (2). The invention also relates to a torsion bar (2) for an active roll stabilizer (1) and an active roll stabilizer (1).

Description

The invention relates to a method for producing a torsion bar for an active roll stabilizer of a motor vehicle. The invention further relates to a torsion bar produced in this way and to an active roll stabilizer with a torsion bar produced in this way.

Each wheel axle of a motor vehicle usually has a roll stabilizer that works according to the torsion bar principle. The roll stabilizer is arranged essentially parallel to the respective vehicle axle and is connected to the wheel suspension at both ends via a respective coupling rod. Furthermore, the roll stabilizer is provided to stabilize the body structure against undesired roll movements about the longitudinal axis of the motor vehicle. Such roll movements occur, for example, when the motor vehicle is cornering or off-road. The roll movement of the motor vehicle is influenced by the roll stabilizer.

With an active roll stabilizer, an actuator is effectively arranged between two torsion bars of the roll stabilizer. The actuator is intended to apply a torsional moment to the torsion bars. In other words, when the actuator is actuated, the two torsion bars are rotated relative to one another and thus subjected to torsion, so that a torsional moment is applied to the torsion bars.

For example, the DE 10 2011 078 819 A1 an active roll stabilizer of a motor vehicle, between whose two stabilizer parts an actuator for torsion of the stabilizer parts is effectively arranged. A sensor is provided for determining a torsional moment acting in the stabilizer parts. Furthermore, a primary sensor is formed by a section of the stabilizer part, which is formed from ferromagnetic material and is magnetically coded, the effective torsional moment being introduced into this section. The primary sensor is formed by a sleeve arranged on the stabilizer part in a rotationally fixed manner, the sleeve being connected in a rotationally fixed manner to a flange, and the flange being connected in a rotationally fixed manner to the actuator.

The object of the present invention is to provide an improved method for producing a torsion bar and a torsion bar for a roll stabilizer. The object is achieved by the subject matter of patent claim 1 and patent claim 7. Preferred embodiments can be found in the dependent claims, the description and the figures.

According to a method according to the invention for producing a torsion bar for an active roll stabilizer of a motor vehicle, the torsion bar comprising a torsion bar spring and a flange, the flange comprising two flange components made of different materials which are connected in one piece, namely a ring element made of a first material and a tube element made of a second Material, at least one of the two flange components is first produced by forging and is connected to the other of the two flange components by diffusion welding immediately after forging, the flange then being subjected to at least one heat treatment for setting a material structure for subsequent magnetic coding, after which at least the tubular element is magnetically coded, and finally the tubular element is rotatably connected to an end portion of the torsion bar to form the torsion bar.

In other words, for example, the ring element is produced by forging and, after forging, is connected to the tubular element by diffusion welding essentially without any significant cooling, that is to say directly from the forging heat. Alternatively, for example, the tubular element is produced by forging and, after forging, is connected to the ring element by diffusion welding essentially without any significant cooling, that is to say directly from the forging heat. Furthermore, alternatively both the tubular element and the ring element are produced by forging and, after forging, are connected to one another by diffusion welding essentially without any significant cooling, that is to say directly from the forging heat.

Diffusion welding enables the connection of the tubular element and the ring element without the use of additional materials and without the introduction of additional heating, for example as in friction welding due to friction. The grain growth between the tubular element and the ring element is stimulated solely by the contact between the two flange components and the high temperature, which stems from the direct removal of at least one of the two flange components from the forging heat, and thus creates a seamless connection between the two flange components. The flange is made in one piece from two different materials with different properties without a weld. The flange is therefore designed as a hybrid flange. The ring element can be formed from a comparatively inexpensive material without any special requirements, and the tube element can be formed from a special material with special requirements with regard to its function as a sensor component.

The flange created by connecting the tubular element and the ring element is subjected to a heat treatment, the heat treatment establishing a homogeneous material structure at least in the tubular element. The material structure set at least in the tube element by the heat treatment serves for magnetic coding of the tube element, the tube element being exposed to a magnetic flux in order to align the material structure and thereby form a hard magnet or permanent magnet which can be used as a sensor component, for example in connection with other sensor components to record a torsional moment on the flange. The tubular element is therefore magnetically encoded. Finally, the tubular element is rotatably connected to an end portion of the torsion bar to form the torsion bar. The flange therefore forms the end section of the torsion bar, the tubular element being provided for connection to the actuator, in particular to a rotatable shaft or a housing of the actuator.

In particular, the two flange components are pressed relative to one another during diffusion welding. As a result, both flange components or at least one flange component are moved axially toward one another during diffusion welding. It is advantageous that a welding process, such as friction welding or flash welding, can be dispensed with by diffusion welding and pressing. This reduces welding errors such as residual gaps, whereby diffusion welding is insensitive to dimensional fluctuations. During the forging and the subsequent diffusion welding of the tubular element with the ring element, a characteristic structure is formed in the flange or on the respective flange component and in the joining area between the two flange components.

The torsion bar is preferably made from a formed torsion bar spring, for example a tube material or solid material. The flange is arranged in a rotationally fixed manner on an end section of the torsion bar spring facing the actuator, the flange being connected in a rotationally fixed manner on the one hand to the actuator and on the other hand to the torsion bar spring. The flange can, for example, be screwed to the actuator with screws. Alternatively, the flange can also be integrally connected to the actuator. Furthermore, the flange can be connected to the torsion bar in a material, friction or non-positive manner. The ring element can have a shape adapted to the connection point of the actuator. The tubular element can have a shape adapted to the connection point of the torsion bar spring. The flange is intended to transmit a torsional moment between the actuator and the torsion bar spring. The torque is generated by the actuator and used to set roll stabilization of the motor vehicle.

A forging temperature during the forging of at least one of the two flange components is preferably 650 ° C. to 1350 ° C. The forging temperature during the forging of at least one of the two flange components is preferably 900 ° C. to 1350 ° C. At least one of the two flange components is removed from the forging heat immediately after forging and is connected to the other of the two flange components by diffusion welding, essentially without any significant cooling. As a result, both flange components are removed from the forging heat and connected to one another by diffusion welding, or only one of the two flange components is removed from the forging heat directly after forging and connected to the other of the two flange components, which has no forging heat, by diffusion welding. Thus, the flange component that has no forging heat can be produced independently of the flange component that is taken directly from the forging heat.

Preferably, at most one of the two flange components is inductively heated in a joining area during pressing. In particular, only the flange component, which has no forging heat, is inductively heated in the joining area in order to shorten the duration of the diffusion welding. If both flange components are removed from the forging heat and connected by diffusion welding, neither flange component is heated inductively.

According to a preferred embodiment, at least one of the two flange components is subjected to a mechanical surface treatment. In particular, the tubular element and / or the ring element are machined. For example, the tube element and / or the ring element are at least re-rotated or reground after the heat treatment.

The flange is preferably heat treated by vacuum hardening and quenching in oil. In other words, the flange, that is to say the tube and ring element connected to one another, is heated in a vacuum furnace and then quenched in oil in order to adjust the material structure, the setting of the material structure on the tube element being decisive. Consequently, at least the tubular element for realizing the sensor function is heat-treated.

The sensor function of the tubular element is preferably used to detect a torsional moment. A sensor placed inside or outside the tubular element can shift the magnetic field of the flange when the flange is subjected to torsion Detect pipe element. The recorded measurement data can then be evaluated by means of a control unit, for example in order to operate the actuator as a function of the torsional load on the flange.

A torsion bar according to the invention for an active roll stabilizer of a motor vehicle, which is manufactured according to a method according to the invention, has a torsion bar spring and a flange, the flange being two flange components made of different materials which are connected in one piece, namely a ring element made of a first material and a tube element made of one second material, wherein at least one of the two flange components is produced by forging and is connected to the other of the two flange components by diffusion welding, at least the tubular element having a magnetic coding.

The first material preferably has a carbon content of less than or equal to 0.2% by mass. The first material preferably has a carbon equivalent of less than 0.5%, in particular less than 0.3%. The carbon equivalent is a measure for assessing the weldability or weldability of steels. A carbon equivalent value of less than 0.45% implies good weldability. From a value greater than 0.65%, the workpiece is only suitable for welding with increased effort, since the formation of martensite in the structure can lead to cold or hard cracks. In particular, the first material can be welded. The first material is preferably not suitable as a sensor component.

The second material preferably has at least 0.3% by mass of carbon. The second material is preferably a hypoeutectoid steel alloy with a carbon content greater than or equal to 0.3% by mass. The carbon content of the second material is therefore 0.3 to 0.8 mass%. The second material is preferably not weldable. The second material is suitable as a sensor component.

For example, the alloy composition or chemical composition of a material can be determined with a scanning electron microscope.

• 1 eine vereinfachte schematische Ansicht eines erfindungsgemäßen aktiven Wankstabilisators, und
• 2 eine vereinfachte schematische Detailschnittdarstellung zur Veranschaulichung des Aufbaus eines Flansches des erfindungsgemäßen Wankstabilisators gemäß 1.

Further measures improving the invention are shown below together with the description of a preferred embodiment of the invention with reference to the figures, the same or similar elements being provided with the same reference numerals. Show it

• 1 a simplified schematic view of an active roll stabilizer according to the invention, and
• 2 a simplified schematic detailed sectional view to illustrate the structure of a flange of the roll stabilizer according to the invention 1 ,

To 1 includes an active roll stabilizer 1 for a motor vehicle - not shown here - a first and second torsion bar 2 , with the two torsion bars 2 by an actuator arranged between them 8th are interconnectable to transmit a torsional moment. The roll stabilizer 1 is arranged transversely to the longitudinal axis of the vehicle and connected at its free ends to wheels or wheel carriers (not shown here).

The respective torsion bar 2 includes a respective torsion bar spring 3 , which is designed as a tube, and a respective flange 4 , with the respective flange 4 two flange components connected in one piece 5 . 6 made of different materials. The first flange component 5 is a ring element 5 , which is formed from a first material, and the second flange component 6 is a pipe element 6 , which is formed from a second material. The respective ring element 5 is non-rotatable with the actuator 8th connected. In contrast, the respective pipe element 6 non-rotatable with the respective torsion bar spring 2 connected.

In 2 is an enlarged section of an end portion of one of the two torsion bars 2 out 1 shown, in the present case the flange 4 is in focus. The flange 4 consists of the two one-piece flange components 5 . 6 , namely the ring element 5 and the tubular element 6 , The ring element is present 5 made by forging and using the tubular element 6 connected by diffusion welding. The flange 4 is designed as a hybrid flange, with the two metallic materials of the flange components 5 . 6 have different material properties.

The ring element 5 is weldable, the ring element 5 consists of the first material, which in the present case has less than 0.2% by mass of carbon. The pipe element 6 consists of the second material, which in the present case has more than 0.3% by mass of carbon. Furthermore, the tubular element 6 magnetically coded. The pipe element 6 is formed into a permanent magnet, and serves as a sensor component to at least one state variable on the flange 4 , especially to sense a torsional moment.

The method according to the invention for producing the torsion bar described above is described below 2 for the roll stabilizer 1 explained. First, the ring element 5 made by forging and immediately after forging substantially without cooling with the tubular member 6 connected by diffusion welding. A forging temperature when forging the ring member 5 is 900 ° C in the present case. The temperature of the ring element is therefore 5 in diffusion welding, due to the direct removal from the forging heat, essentially 900 ° C. Temperature differences up to 10% of the forging temperature may be permissible. In diffusion welding, the contact between the two flange components 5 . 6 and the high temperature in the joining area 7 between the two flange components 5 . 6 the grain growth between the ring element 5 and pipe element 6 stimulated and thus creates a seamless connection.

In particular, the two flange components 5 . 6 pressed relative to each other during diffusion welding. The pipe element 6 that compared to the ring element 5 is not taken directly from the forging heat when pressing in the joining area 7 preferably inductively heated to diffusion welding the two flange components 5 . 6 to accelerate. When pressing, there is only an axial load on the flange components 5 . 6 towards each other, but no rotation as for example in friction welding.

After the two flange components 5 . 6 are interconnected and thus the flange 4 is formed, the flange 4 a heat treatment for setting a material structure for magnetic coding of the tubular element 6 subjected. In the present case the flange 4 heat treated by vacuum hardening and quenching in oil. The material structure of the tubular element 6 set such that during a subsequent magnetic coding by means of a magnetic field the material structure is aligned so that the tubular element 6 is formed to the permanent magnet.

Finally, the pipe element 6 with an end portion of the torsion bar spring 3 non-rotatably connected to the torsion bar 2 to train. In a further step, two torsion bars 2 with the actuator 8th connected to the active roll stabilizer 1 to train.

Reference list

1

Roll stabilizer

2

Torsion bar

3

Torsion bar spring

4

flange

5

Flange component, namely ring element

6

Flange component, namely tubular element

7

Joining area

8th

Actuator

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102011078819 A1 [0004]

Claims (10)

Method for producing a torsion bar (2) for an active roll stabilizer (1) of a motor vehicle, the torsion bar (2) comprising a torsion bar spring (3) and a flange (4), the flange (4) comprising two flange components (5) which are connected in one piece , 6) made of different materials, namely a ring element (5) made of a first material and a tube element (6) made of a second material, at least one of the two flange components (5, 6) being first produced by forging and immediately after Forging is connected to the other of the two flange components (6, 5) by diffusion welding, the flange (4) then being subjected to at least one heat treatment for setting a material structure for magnetic coding, wherein at least the tube element (6) is then magnetically coded, and finally the tubular element (6) is connected in a rotationally fixed manner to an end section of the torsion bar spring (3) in order to 2) train. Procedure according to Claim 1 , characterized in that a forging temperature during the forging of at least one of the two flange components (5, 6) is 650 ° C to 1350 ° C. Method according to one of the preceding claims, characterized in that at least one of the two flange components (5, 6) is subjected to a mechanical surface treatment. Method according to one of the preceding claims, characterized in that the two flange components (5, 6) are pressed relative to one another during diffusion welding. Procedure according to Claim 4 , characterized in that at most one of the two flange components (5, 6) is inductively heated in a joining area (7) during pressing. Method according to one of the preceding claims, characterized in that the flange (4) is heat-treated in oil by vacuum hardening and quenching. Torsion bar (2) for an active roll stabilizer (1) of a motor vehicle, the torsion bar (2) according to a method according to one of the Claims 1 to 6 is produced, the torsion bar (2) having a torsion bar spring (3) and a flange (4), the flange (4) being two integrally connected flange components (5, 6) made of different materials, namely a ring element (5) made of one first material and a tubular element (6) made of a second material, wherein at least one of the two flange components (5, 6) is produced by forging and is connected to the other of the two flange components (6, 5) by diffusion welding, at least that Pipe element (6) has a magnetic coding. Torsion bar (2) after Claim 7 , characterized in that the first material has a maximum of 0.2 mass% carbon. Torsion bar (2) according to one of the Claims 7 to 8th , characterized in that the second material has at least 0.3 mass% carbon. Active roll stabilizer (1) for a motor vehicle, comprising two torsion bars (2) and an actuator (8) arranged between them, the two torsion bars (2) being connectable to one another via the actuator (8) in order to transmit a torsional moment, characterized in that that at least one torsion bar (2) according to a method according to one of the Claims 1 to 6 is made.

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