Method for manufacturing an actuating cylinder with a position sensor - Patents.com

Abstract

The present invention relates to a method for manufacturing an actuating cylinder comprising a cylinder (10), a piston unit (20) and a position sensor (30), characterized by the following method steps: a) fitting the position sensor (30) together with its body (31) into the receiving bore (17) of the bottom closure part (13) to form a pre-assembly (40); b) fastening the body (31) in the receiving bore (17); c) joining and connecting the cylinder tube (11) to the pre-assembly (40) on the bottom closure part (33), with the measurement sensor rod (32) located in the cylinder interior (16); d) joining the piston unit (20), the guide closure part (12) and the cylinder tube (11), with the piston unit (20) together with the measurement sensor rod (32) located in the axial bore (21), said method steps being performed either in the order a), b), c) and d) or in the order a), b), d) and c).

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an actuating cylinder having a position sensor with a measuring sensor rod arranged in a hollow piston unit. [Background technology]

[0002] It is known from the prior art to provide hydraulic actuating cylinders with position measurement systems that allow the actuation position of the piston unit to be detected and thus the operating state of the actuated unit to be indirectly detected. Important areas of application are, for example, agricultural machinery or refuse collection and other municipal vehicles.

[0003] Such a position measuring system can be based in particular on the acquisition of a magnetic field that changes due to the position of the piston unit. Solutions are also known in which the position measuring system is integrated into the pressure chamber of the operating cylinder (hereinafter referred to as the working cylinder). For example, solutions are known in which the piston rod is designed as a hollow component so that a fixed measuring rod can be placed therein. The piston rod performs a linear stroke movement relative to the measuring rod, which can be detected by the measuring rod, preferably in a contactless manner, and then evaluated.

[0004] A disadvantage is the complex assembly. According to the prior art, the cylinder tube is first welded to the bottom closure, performed as a solid MAG weld. After cleaning the interior thus formed, the position measuring system with the measuring rod must be inserted axially through the cylinder tube and positioned on the inner wall of the bottom closure. The difficult and time-consuming threading of the connecting wires is a particular disadvantage. Fastening the measuring rod and ensuring its correct axial alignment are also difficult and time-consuming. Summary of the Invention

[0005] It is an object of the present invention to provide a reliable, time-saving and cost-saving method for manufacturing actuation cylinders with position sensors that allows a high degree of automation and ensures high quality.

[0006] This object is solved by a manufacturing method with the features of claim 1. Preferred further developments result from the dependent claims.

[0007] The method according to the invention is designed to manufacture an actuation cylinder equipped with a position sensor having the structure described below.

[0008] The actuating cylinder manufactured by the manufacturing method according to the present invention comprises, as its basic elements, a cylinder, a piston unit and a position sensor.

[0009] The cylinder of the working cylinder comprises, in a manner known per se, a cylinder tube, a guide closure and a bottom closure.

[0010] The cylinder tube has two opposing cylinder tube ends. These are the guide cylinder tube end and the bottom cylinder tube end. The guide closure is located at the guide cylinder tube end, and the bottom closure is located at the bottom cylinder tube end. Hereinafter, the guide cylinder tube end and the bottom cylinder tube end are collectively referred to as the cylinder tube ends, and the guide closure and the bottom closure are collectively referred to as the closure. The cylinder tube and the closures located at its ends form the cylinder interior.

[0011] The piston unit is arranged inside the cylinder. The piston unit is preferably designed as an assembly consisting of a piston and a piston rod, in which the piston rod slides through a guide closure. However, the piston unit may also be designed as a single part and may be a plunger-piston. When the actuating cylinder is used as intended, the piston unit performs a linear stroke movement.

[0012] The piston unit has an axial borehole opening at the bottom side and is therefore designed as a hollow piston unit, which extends into a substantially cylindrical cavity that provides space for the placement of a measurement sensor rod.

[0013] Furthermore, the actuating cylinder is provided with a position sensor, and the method according to the invention is based on the position sensor arrangement described below.

[0014] The position sensor comprises a body, an axially extending measuring sensor rod and an evaluation electronic system, which may be either an analog or digital system.

[0015] The body, also referred to as the sensor housing, is preferably cylindrical in basic shape and is arranged in the axial receiving borehole of the bottom closure, which is located on the inside of the bottom closure, where the inside is understood to be the side of the bottom closure facing axially towards the piston unit and which forms part of the inner surface of the cylinder interior.

[0016] The measurement sensor rod is disposed in the body and, when the body is positioned as intended in the cylinder bottom, is axially and concentrically disposed relative to the cylindrical interior and aligned with the guide closure. The positional relationship of the measurement sensor rod relative to the bottom closure is therefore indirectly determined by the body. During the stroke, the measurement sensor rod immerses in the axial borehole of the hollow cylinder unit; in this changing positional relationship, the measurement sensor rod is a fixed element and the borehole is a movable element. The immersion depth of the measurement sensor rod in the axial borehole is detected inductively. Preferably, a ring magnet is disposed in the hollow piston, which surrounds the measurement sensor rod and moves linearly relative to it during the stroke. When used as intended, the assembly consisting of the body and the measurement sensor rod is located in the pressure chamber of the working cylinder. Furthermore, an evaluation electronic system which further evaluates the primary signal of the measuring sensor rod and provides the primary signal as a measurement signal for further position evaluation is preferably connected via a connecting line leading out from the main body.

[0017] The method according to the invention for manufacturing the described actuating cylinder with a position sensor comprises the following process steps: a) fitting a position sensor together with its body into a receiving borehole in a bottom closure to form a pre-assembly; b) fastening the body within the receiving borehole; c) joining and connecting the cylinder tube to the bottom closure with the measurement sensor rod located inside the cylinder; d) joining the piston unit, the guide closure and the cylinder tube together, with the piston unit being positioned in the axial borehole together with the measurement sensor rod; It is characterized by:

[0018] The process steps of the present invention are described in more detail below.

[0019] a) fitting the position sensor together with its body into a receiving borehole in the bottom closure to form a pre-assembly; In this process step, the body of the position sensor is inserted axially into the receiving borehole of the bottom closure. Advantageously, unlike the prior art, the bottom closure is provided without an associated cylinder tube in this process step, so that there is a free passage into the interior of the bottom closure; in particular, any connecting wires can be inserted into the conduits of the bottom closure without any problems. A further advantage is the free lateral passage for any handling technique capable of guiding the body and inserting it into the receiving borehole and fastening the body therein, either by a gripper in automated production or by an assembly worker in manual production.

[0020] b) fastening the body into the receiving borehole After the body has been inserted into the receiving borehole, it is fastened to the receiving borehole in process step b). Fastening here is understood to mean, in particular, axial positioning relative to the bottom closure. For example, the body inserted inside the borehole can be held in place by the pressure present in the piston chamber or by a groove in the body and a radially disposed screw engaging in this groove. Here, it is essential for the method according to the invention that a pre-assembly is provided, consisting of the bottom closure, the body and the measurement sensor rod.

[0021] c) joining and connecting the cylinder tube to the bottom closure with the measuring sensor rod located inside the cylinder; In process step c), the pre-assembly is joined and connected to the cylinder tube. For this purpose, the cylinder tube is guided axially toward the bottom closure, and the measurement sensor rod is positioned inside the forming cylinder. The bottom closure preferably has a ring connecting piece with a shoulder forming an axial ring surface. The cylinder tube is pressed onto the ring connecting piece so that the cylinder tube rests against the axial ring surface of the bottom closure together with the cylinder tube ring surface. The connection is preferably made snugly by laser welding, which produces a radially arranged laser ring weld seam. Surprisingly, it has been found that laser welding allows for a sufficiently low energy input per unit length so that the heat-sensitive components of the position sensor, particularly the base housing, are not damaged.

[0022] d) joining the piston unit, the guide closure and the cylinder tube together, with the piston unit being positioned in the axial borehole together with the measurement sensor rod; In process step d), the piston unit is first inserted into the guide closure. The assembly consisting of the guide closure and the piston unit is then mounted, and the piston unit is inserted into the cylinder tube in such a way that the measurement sensor rod is immersed in the axial borehole of the piston unit, preferably without contacting the piston unit. The guide closure is joined to the guide end of the cylinder tube and fixed there, preferably by laser welding, so as to provide a snug fit.

[0023] According to the present invention, process steps c) and d) can be performed both in the order c) then d) and in the order d) then c).

[0024] The method according to the present invention is based, inter alia, on the surprising discovery that the heat-affected zone can be limited by laser welding so that even an already inserted position sensor is not thermally damaged. It is only through this consideration, which is fundamentally opposite to the prior art, that a special advantage becomes possible. The free passage into the interior of the bottom closure provided by the method according to the present invention during insertion of the position sensor allows the connecting wire leading from the body to be easily routed within the bottom closure through an opening provided for this purpose. Furthermore, a free lateral passage also exists so that the body can be gripped directly without any problems. Preferably, this can also be performed automatically using a gripper. This technique has the advantage that stress on the measuring sensor rod is avoided and the measuring sensor rod is protected against possible damage. Furthermore, the operations of positioning and fastening the body relative to the bottom closure are advantageously simplified. Therefore, it is possible to mass-produce low-cost, high-quality position sensors for applications such as agriculture, and electronically assessable position measurement for working cylinders is also becoming increasingly important for satellite-based control purposes.

[0025] According to a particularly advantageous variant of the method, the bottom closure part is connected to the cylinder tube in the manner of a material connection by means of a circumferential laser ring weld seam, which forms a liquid-tight sealing plane, and process step c) is performed by laser welding the bottom closure part to the cylinder tube by producing the laser ring weld seam.

[0026] A further advantageous variant of the method is characterized in that the working cylinder is designed as a differential working cylinder, the piston unit comprises a piston and a piston rod, and the axial borehole is arranged in the piston rod.

[0027] According to this advantageous variant, differential actuating cylinders, which are widely used and have high economic importance, are manufactured with a position measuring system in a simple and reliable manner.

[0028] According to another advantageous variant, the method is characterized in that process step d) is carried out before process step c).

[0029] Therefore, an assembly consisting of a cylinder tube, a guide closure, and a piston unit is first manufactured according to this further development. Deviating from the prior art, the assembly consisting of a cylinder tube, a guide closure, and a piston unit can advantageously be completed in this way and then used for further assembly. It is particularly advantageous that no sensitive position sensor is integrated into this assembly, so that no precautions need to be taken against damage and no interference caused by the position sensor is present. Any foreign matter at the connection point between the guide closure and the guide end can be removed unhindered before carrying out the final installation together with the pre-assembly.

[0030] To complete the working cylinder, this assembly only needs to be joined to the pre-assembly according to the invention. For this purpose, the measuring sensor rod can be inserted in a particularly simple manner into the axial borehole of the piston unit. The favorable connection between the pre-assembly at the bottom closure and the bottom end of the cylinder tube by laser welding prevents any scaling or other foreign matter from occurring.

[0031] According to a further aspect of the invention, the method is characterized in that the bottom closure is connected to the cylinder tube by a mating thread, and process step c) is performed by screwing the bottom closure onto the cylinder tube.

[0032] This variant of the method also offers the special advantages mentioned above.

[0033] The invention is explained in more detail by way of an exemplary embodiment with the aid of the following figures, in which: [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a cross-sectional view of a laser-coupled actuation cylinder with a position sensor. [Figure 2] FIG. 10 is a cross-sectional view of a pre-assembly. [Figure 3] FIG. 10 is a cross-sectional view of a pre-assembly. [Figure 4] FIG. 10 is a cross-sectional view of the actuation cylinder after threaded coupling. DETAILED DESCRIPTION OF THE INVENTION

[0035] In this description, the same reference numbers in the various drawings always refer to the same features or components. Reference numbers are also used in the description even if they are not shown in the associated drawings.

[0036] FIG. 1 shows the structure of an exemplary embodiment of an actuation cylinder in a differential actuation cylinder design joined according to the present method by a laser ring weld seam.

[0037] The actuating cylinder comprises, as basic components, a cylinder 10, a piston unit 20 and a position sensor 30.

[0038] In this embodiment, the cylinder 10 comprises a cylinder tube 11 and closure parts 12, 13, with the guide closure part 12 arranged at the guide cylinder tube end 14 and the bottom closure part 13 arranged at the bottom cylinder tube end, forming a cylinder interior 16. The piston unit 20 comprises a piston 22 and a piston rod 23 formed as a hollow element by an axial borehole 21. The piston rod 23 slidably passes through the guide closure part 12.

[0039] The position sensor 30 comprises a body 31, a measuring sensor rod 32 arranged on the body 31, and an evaluation electronic system 33.

[0040] The body 31 is placed in its receiving borehole 17 with a bottom closure 13 which is welded to the cylinder tube 11 by a laser ring weld seam.

[0041] During the stroke movement of the piston unit 20, the position of the piston unit 20 changes linearly relative to the measurement sensor rod 32 housed in the axial borehole 21. The associated change in the magnetic field surrounding the measurement sensor rod 32 is detected by a sensor, evaluated by an evaluation electronic system and output by this system as a measurement signal.

[0042] This method is explained in more detail using the pre-assembly 40 shown in FIG.

[0043] In process step a), the assembly consisting of the body 31 and the measuring sensor rod 32 is inserted axially with the body 31 into the cylindrical receiving borehole 17 of the bottom closure 13. Advantageously, a spatially free passage to the two joining components 31, 32 and 13 is provided here.

[0044] In process step b), the body 31 is fastened in the receiving borehole 17, in this case the fastening being carried out in parallel to the joining process in step a) by means of a precise axial press fit.

[0045] In the next process steps c) and d), the piston unit 20 is inserted into the guide closure part 12, which is attached to the cylinder tube 11, and the piston unit 20 is further inserted into the cylinder tube 11. The connection between the bottom closure part 13 of the pre-assembly 40 and the cylinder tube 11 is realized by laser welding, so that a laser ring weld seam 50 is obtained and at the same time forms a liquid-tight sealing plane.

[0046] 3 and 4 show modified exemplary embodiments, and the above description given for FIGS. 1 and 2 applies in the same way, unless the following special features apply.

[0047] 3 is produced in process steps a) and b) and has an external thread (not numbered) on the bottom closure 13. The cylinder tube 11 has an internal thread (not numbered) that corresponds to this external thread.

[0048] In process step d), the assembly consisting of the cylinder tube 11, the guide closure 12 and the piston unit 20 with the piston 22 and hollow piston rod 23 is first mounted.

[0049] Finally, in process step c), the assembly consisting of the cylinder tube 11, the guide closure 12 and the piston unit 20, and the pre-assembly 40 are axially joined to one another and the measurement sensor rod 32 is inserted into the axial borehole 21. Finally, the bottom closure 13 and the cylinder tube 11 are screwed to one another by means of the pairing of the male and female threads, so that they are joined with a snug fit. [Explanation of symbols]

[0050] 10 cylinders 11 Cylinder tube 12 Guide Closure 13 Bottom closure 14 Guide side cylinder tube end 15 Bottom cylinder tube end 16 Inside the cylinder 17 Axial receiving borehole 20 Piston Unit 21 Axial borehole 22 Piston 23 Piston rod 30 Position Sensor 31 Main Unit 32 Measuring sensor rod 33 Electronic Evaluation System 40 Pre-assembly 50 Laser Ring Welded Seams

Claims

1. 1. A method for manufacturing an actuation cylinder with a position sensor, comprising the steps of: The actuating cylinder comprises a cylinder (10), a piston unit (20), and a position sensor (30); The cylinder (10) comprises a cylinder tube (11), a guide closure (12) and a bottom closure (13); The cylinder tube (11) has a guide cylinder tube end (14) where the guide closure part (12) is arranged, and a bottom cylinder tube end (15) where the bottom closure part (13) is arranged, The cylinder tube (11) and the closure parts (12, 13) form a cylinder interior (16); the piston unit (20) is arranged inside the cylinder (16), is designed as a hollow piston unit, has an axial borehole (21) opening on the bottom side and slidably passes through the guide closure (12), the position sensor (30) comprises a body (31) arranged in the inner axial receiving borehole (17) of the bottom closure part (13), an axially extending measurement sensor rod (32) arranged in the axial borehole (21), connected to the body (31) and arranged in a fixed relationship to the bottom closure part (13), and an evaluation electronic system (33), The following process steps: a) fitting said position sensor (30) together with its body (31) into said receiving borehole (17) of said bottom closure part (13) to form a pre-assembly (40); b) fastening said body (31) in said receiving borehole (17); c) joining and connecting the cylinder tube (11) to the pre-assembly (40) at the bottom closure (13) with the measurement sensor rod (32) located inside the cylinder (16); d) joining the piston unit (20), the guide closure (12) and the cylinder tube (11) together, with the piston unit (20) placed in the axial borehole (21) together with the measurement sensor rod (32); wherein the process steps can be performed in either the order a), b), c), and d), or the order a), b), d), and c).

2. the bottom closure (13) is connected to the cylinder tube (11) in a material-joint manner by a circumferential laser ring weld seam (50), the laser ring weld seam (50) forming a liquid-tight sealing plane; 2. The method according to claim 1, characterized in that process step c) is carried out by laser welding the bottom closure (13) to the cylinder tube (11) by producing the laser ring weld seam (50).

3. the actuating cylinder is designed as a differential actuating cylinder, 3. The method according to claim 1, wherein the piston unit (20) comprises a piston (22) and a piston rod (23), and wherein the axial borehole (21) is arranged in the piston rod (23).

4. 4. The method according to claim 1, wherein process step d) is carried out before process step c).

5. said bottom closure (13) being connected to said cylinder tube (11) by means of a mating thread; and 5. Method according to any one of claims 1 to 4, characterized in that process step c) is carried out by screwing the bottom closure (13) onto the cylinder tube (11).

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