EP2922649B1

EP2922649B1 - Rolling of spring carrier arms

Info

Publication number: EP2922649B1
Application number: EP13802457.5A
Authority: EP
Inventors: Derk Geert Aalderink; Pieter Arie VAN WILGEN
Original assignee: VDL Weweler BV
Current assignee: VDL Weweler BV
Priority date: 2012-11-23
Filing date: 2013-11-18
Publication date: 2017-01-11
Anticipated expiration: 2033-11-18
Also published as: ES2613940T3; WO2014081288A1; EP2922649A1

Description

The present invention relates to a method for manufacturing spring carrier arms for wheel axle suspensions of a vehicle, in particular trucks trailers and semi-trailers. Such spring carrier arms comprise in general at least one flexible portion (spring portion), which has a free end that in use is attached to a vehicle chassis and an axle mounting portion adjoining the flexible portion, against which in use a wheel axle is mounted.
In some applications the flexible portion is a leading portion of the arm which has a free end which is pivotably attached to the vehicle chassis. Often said free end of the leading portion is formed as an attachment eye. In many applications the spring carrier arm may also comprise a trailing portion which adjoins the axle mounting portion, which in use is attached to an air spring or bellows supported by the chassis. Spring carrier arms of this type are in the specific field also referred to as "flexible arms" or "flexible trailing arms".
Another type of spring carrier arms are so called "parabolic springs" or leaf springs. These leaf springs may be attached to the chassis by means of a sliding part.
One of the common ways to form spring carrier arms is by means of a rolling process in a rolling machine. In such a rolling process a rectangular steel blank having an overall size which is an approximation to the finished spring carrier arm is passed between two rotating rolls. In particular, each portion of the blank is passed between two rotating rolls of a rolling device, wherein a roll profile is followed, in order to form a desired thickness profile of the different portions of the spring carrier arm. Thus for example for trailing arms the leading portion, the axle mounting portion and, possibly, the trailing portion of the arm are formed according to a roll profile.
The manufacturing process is automated by the use of handling devices, in particular manipulators and industrial robots, for handling the workpieces. These handling devices take the unmachined workpiece, and position the workpiece between the rolls of the rolling device. The handling devices hold on to the workpiece while it is rolled. After the workpiece is rolled, the handling devices deposit it in a finished parts storage location.
The process reliability of the shaping process is principally a function of the precision with which the unmachined workpiece to be machined is inserted into the rolling machine, specifically, into the working region thereof. In order to meet these demanding requirements, in the setup of the rolling machine it is necessary to adjust the handling devices precisely to the position of the working region of the tool. This is rather laborious and time-consuming, and the setup process is consequently expensive.
In one known rolling arrangement, an industrial robot (articulated robot) takes the workpiece and places it on a dedicated manipulator which has a stationary base and a carriage with a gripping means for gripping the workpiece. The carriage is linearly guided on the stationary base. The gripping means grips the workpiece and introduces it between the rolls of the rolling device. It holds on to the workpiece during rolling. After rolling the gripping means releases the workpiece and an industrial robot takes the workpiece from the carriage and deposits it on another location.
In another known arrangement for a forging process known from the firm Lasco, a base is mounted to the robot head of an industrial robot (articulated robot) and a carriage with a gripper is linearly guided on said base. During the forging of the workpiece the robot holds the base of the slider manipulator in a fixed position, while the linearly guided carriage and the gripper of the manipulator move with the workpiece.
GB 2 213 753 A , on which the preamble of claims 1 and 5 is based, shows another arrangement for taper rolling leaf springs for vehicle suspensions. This arrangement has a linearly movable carriage in which the deformable blank is clamped while it is rolled by a pair of rolls.
These type of manipulators with a linearly guided carriage are prone to wear due to the movement forced upon the workpiece by the rolls.
The present invention has for an object to provide an alternative method for manufacturing a spring carrier arm for a wheel axle suspension of a vehicle.
This object is achieved by a method for manufacturing a spring carrier arm for a wheel axle suspension of a vehicle, wherein the spring carrier arm comprises at least one flexible portion, which in use is attached to a vehicle chassis, and an axle mounting portion adjoining the at least one flexible portion, against which in use a wheel axle is mounted. The method comprises the steps of:

taking a workpiece, which initially is a rectangular steel blank having an overall size which is an approximation to the finished spring carrier arm;
passing each portion of the workpiece between two rotating rolls of a rolling device, wherein a roll profile is followed, in order to form a desired thickness profile of the at least one flexible portion and the axle mounting portion of the spring carrier arm to be formed.

According to the invention the workpiece that is to be rolled is held during rolling by the gripper of the robot, which gripper is directly at the head of the robot. This is unlike the known manipulator by for example Lasco which has a gripping means that is arranged on a linearly guided carriage. According to the invention the robot is "free floating" in one direction, i.e. the longitudinal direction of the spring carrier arm and has normal behaviour in other directions. In this way it can be prevented that the spring carrier arm sags or curves.
Preferably, the position of the robot gripper that holds the spring carrier arm to be formed is captured and is used to control the roll gap between the rolls of the rolling device while the profile of the different portions of the arm is rolled. In this way the robot is used as a measurement tool which "measures" the displacement and the velocity of the workpiece. These "measured" parameter values are compared by a control system for the roll gap control to theoretical parameter values corresponding to the rolling profile for the spring carrier arm. The gap between the rolls of the rolling device can be adjusted based on deviations between the theoretical values (reference values) and the measured values of these parameters. Also the rotational velocity of the rolls can be adjusted in this manner.
Preferably, the location on the workpiece where the robot holds the workpiece in the first rolling run is used as a reference point for the rolling profile of the entire spring carrier arm. In this way the robot can release the workpiece in a defined position and pick it up again at another location on the workpiece, while the initial reference point remains. In this way different portions of the spring carrier arm can be rolled while the gripper holds the arm at different locations.
Preferably, the robot gripper holds the blank at a position in the mounting portion to be when the other portions of the spring carrier arm, e.g. the leading portion and/or trailing portion is rolled.
The invention also relates to a manufacturing arrangement for manufacturing of a spring carrier arm for a wheel axle suspension of a vehicle, wherein the spring carrier arm comprises at least one flexible portion, which in use is attached to a vehicle chassis, and an axle mounting portion adjoining the at least one flexible portion, against which in use a wheel axle is mounted. The arrangement comprises a rolling device for rolling different portions of the spring carrier arm, which rolling device comprises rotating rolls between which in use the workpiece is passed to apply a rolling profile on said spring carrier arm portions. The arrangement furthermore comprises a robot having a head and a gripper mounted directly to said head, which robot gripper in use holds the spring carrier arm to be formed while it is passed between the rolls of the rolling device. The robot is programmed such that it allows a free movement of the spring carrier arm to be formed in a longitudinal direction of the arm.
The robot used in the manufacturing arrangement is an articulated robot.
The invention will be elucidated in the following detailed description with reference to the drawing, in which:

Fig. 1 illustrates rolling of a spring carrier arm with use of an articulated robot,
Fig. 2 illustrates a robot gripper holding an end of the spring carrier arm,
Fig. 3 shows how a robot holds a spring carrier arm which is 3D formed, and
Fig. 4 shows schematically the control of the rolls.

In Fig. 1 is shown a spring carrier arm 1 which is held by a robot 2. The robot 2 is an articulated robot also referred to as an "industrial robot", which typically has rotary joints, which interact with each other. The robot 2 has a head 3 on which a gripper 4 is mounted. The gripper 4 holds the spring carrier arm 1 while a portion of the arm 1 is passed between rolls 5 of a rolling machine. The rolls 5 are rotating rolls and have between them a gap indicated by reference numeral 6, a so called roll gap, which determines the thickness of the portion of the arm 1 that is rolled. The roll gap 6 is variable and is varied over the length of the arm 1, whereby the arm 1 is given a thickness profile.
In a typical embodiment of the spring carrier arm 1 there is formed a leading portion 1 a, which has a defined thickness profile. The leading portion 1 a has a free end on which an attachment eye may be formed such that in use it can be pivotably attached to a vehicle chassis. Adjoining the leading portion 1 a an axle mounting portion 1 b is formed, against which in use a wheel axle is mounted.
The movement of the workpiece 1 is determined by the rolling movement of the rolls 5. The robot 2 allows a free movement of the workpiece 1 in the longitudinal direction indicated by double arrow 7. The position of the gripper 4 in the longitudinal direction 7 of the arm 1 is captured during rolling. This position of the gripper is a reference for the rolling profile that the rolling machine is applying on the workpiece. The robot 2 is thus used as a measurement device which is part of the control system that controls the speed and position of the rolls 5.
In Fig. 2 is shown a spring carrier arm 1 with three different sections 1a - 1c with each a different profile. In particular the arm shown in Fig. 2 comprises a leading portion 1 a, which has a defined thickness profile. Furthermore it has a trailing portion 1 c against which an air spring can be mounted and an axle mounting portion 1 b that is located between the trailing portion 1 c and the leading portion 1 a. The leading portion 1 a has a free end on which an attachment eye may be formed such that it in use can be pivotably attached to a vehicle chassis. In Fig. 2 the robot gripper 4 holds the arm 1 at the end of the trailing portion. The robot 2 will generally hold he workpiece in the first rolling run at the location where the axle mounting portion 1 b of the arm is to be formed. This location is used as a reference point for the rolling profile of the entire spring carrier arm 1. After for example the leading part 1 a and the trailing portion 1 c have been rolled, the robot 2 can release the workpiece 1 in a defined position and pick it up again at another location on the workpiece, in the case of Fig. 2 at the end of trailing portion 1 c, in order to roll the portion 1 b. The initial reference point (at the part 1 b) remains. In this way different portions of the spring carrier arm 1 can be rolled while the gripper 4 holds the arm 1 at different locations.
In Fig. 4 is shown schematically the control system of the rolls 5. The product 1 is rolled according to a predefined profile with two rolls 5. First the roll gap opens, such that the product 1 can be inserted. When the robot 2 has positioned the product 1 between the rolls 5, the roll gap 6 closes to its starting position. The rolls 5 are driven with a predefined speed profile [a] (e.g. trapezoid). Together with the planned elongation, the resulting robot gripper position and speed are calculated [b]. This data is used for the planned robot gripper motion [c]. Differences between the planned and actual elongation of the arm portions 1a - 1 c result in a difference between planned and actual robot gripper position. The actual linear speed and position [d] of the robot gripper 4 are used for the product profile generator [e]. This results in a theoretical roll gap, which is controlled by the roll gap control [f].
In Fig. 3 an example is shown of how a spring carrier arm may be formed which has a thickness profile and a width profile. It can be seen that the arm is first passed between a first set of rolls 5. Then the robot gripper turns the workpiece 1 over 90° and moves it to another rolling machine and passes it through a second pair of rolls 8, which is visible in Fig. 3. It is also possible that the workpiece is passed through the same pair of rolls, but that the rolls have different portions A and B as is indicated as well in Fig. 3, one to form the thickness profile of the arm portions 1 a-1 c and one to form the width profile of the arm portions 1a-1c.
It is also possible that two pairs of rolls are placed behind each other, wherein the rolls of one pair are oriented with their central axes under an angle of 90° with respect to the central axes of the rolls of the other pair. One pair is used for rolling the thickness profile and the other pair for rolling the width profile of the arm 1. In such an arrangement the robot does not have to move the workpiece from one rolling device to the other. It is also conceivable that the pairs of rolls are not located behind each other. In that case the robot moves the workpiece from one rolling machine to another rolling machine (cf. Fig. 3), but does not have to turn the workpiece as is described above in relation to Fig. 3.
It is also conceivable to use rolls with a protrusion or a recess provided on or in it, which is then rolled into the outer surface of the spring carrier arm.
It must be noted that in the above description with reference to the drawings the typical trailing arms are used as an example. It is however to be understood that also other flexible arms like leaf springs that are commonly used in vehicle suspenions are part of the invention.

Claims

Method for manufacturing a spring carrier arm (1) for a wheel axle suspension of a vehicle,
wherein the spring carrier arm (1) comprises at least one flexible portion (1 a), which in use is attached to a vehicle chassis, and an axle mounting portion (1 b) adjoining the at least one flexible portion, against which in use a wheel axle is mounted,
which method comprises the steps of:
- taking a workpiece (1), which initially is a rectangular steel blank having an overall size which is an approximation to the finished spring carrier arm;

- passing each portion (1 a-1 c) of the workpiece between two rotating rolls (5) of a rolling device, wherein a roll profile is followed, in order to form a desired thickness profile of the at least one flexible portion (1 a) and the axle mounting portion (1 b) of the spring carrier arm (1) to be formed;
characterized in that the work piece is picked up by an articulated robot (2) with a head (3) and a gripper (4) directly mounted at the head, which robot gripper (4) holds the workpiece while it is passed between the rolls (5) of the rolling device, wherein it allows a free movement of the workpiece in a longitudinal direction of the spring carrier arm (1) to be formed.
Method according to claim 1, wherein the position of the robot gripper (4) that holds the workpiece is captured and is used to control the roll gap (6) between the rolls (5) of the rolling device while the profile of the different portions (1 a -1 c) of the spring carrier arm (1) is rolled.
Method according to any one of the preceding claims, wherein the position where the robot gripper (4) holds the workpiece in the first rolling run is used as a reference point for the rolling profile for the entire spring carrier arm (1).
Method according to any one of the preceding claims, wherein the robot gripper (4) holds the workpiece at a position in the axle mounting portion (1 b) to be when the other portions (1a, 1c) of the spring carrier arm (1) are rolled.
Manufacturing arrangement for manufacturing of a spring carrier arm (1) for a wheel axle suspension of a vehicle,
wherein the spring carrier arm (1) comprises at least one flexible portion (1 a), which in use is attached to a vehicle chassis, and an axle mounting portion (1 b) adjoining the at least one flexible portion (1 a), against which in use a wheel axle is mounted,
which arrangement comprises a rolling device for rolling different portions of the spring carrier arm (1), which rolling device comprises rotating rolls (5) between which in use the workpiece is passed to apply a rolling profile on said spring carrier arm portions (1a - 1 c), said arrangement furthermore comprising a gripper (4), which gripper (4) in use holds the spring carrier arm (1) to be formed while it is passed between the rolls (5) of the rolling device, characterized in that the gripper (4) is mounted directly to a head (3) of an articulated robot (2), wherein the robot (2) is programmed such that it allows a free movement of the spring carrier arm (1) to be formed in a longitudinal direction of the spring carrier arm (1).