Method for producing working cylinder with position sensor

Abstract

The invention relates to a method for producing a working cylinder having a cylinder (10), a piston unit (20) and a position sensor (30), the piston unit (20) being designed as a hollow piston unit and having an axial bore (21) which is open on the bottom side, the position sensor (30) having a main body (31) which is arranged in an axial receiving bore (17) on the interior side of a bottom closure (13), the invention relates to a method for measuring the thickness of a base closure (13), comprising an axially extending measuring sensor rod (32) which is arranged in an axial bore (21), which is connected to the base body (31) and which is arranged in a fixed positional relationship with respect to the base closure (13), and comprising an evaluation electronics (33), characterized by the following method steps, in which the measuring sensor rod (32) is arranged in the axial bore (21) and is connected to the base body (31) and is arranged in a fixed positional relationship with respect to the base closure (13). The method steps are carried out in the sequence of a), b), c), d) or in the sequence of a), b), d), c): a) the position sensor (30) is joined with its base body (31) in the receiving bore (17) of the bottom closure (13) to form a pre-assembled component (40), b) the base body (31) is fixed in the receiving bore (17), c) the cylinder barrel (11) is joined and connected to the pre-assembled component (40) at the bottom closure (13) with the measuring sensor rod (32) arranged in the cylinder interior (16), d) engaging the piston unit (20), the guide closure (12) and the cylinder barrel (11) with the piston unit (20) and the measuring sensor rod (32) arranged in the axial bore (21).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a working cylinder with a position sensor, the position sensor having a measuring sensor rod arranged in a hollow piston unit. Background Art

[0002] It is known from the prior art that a hydraulic working cylinder is provided with a stroke measuring system which can detect the working position of the piston unit and thus indirectly detect the operating state of the unit to be actuated. Important application areas are, for example, agricultural machinery or refuse collection vehicles or other municipal vehicles.

[0003] Such a stroke measuring system can be based in particular on the detection of a magnetic field which changes due to the position of the piston unit. Here, a solution for integrating the stroke measuring system into the pressure chamber of the working cylinder is also known. For example, a solution is known in which the piston rod is constructed hollow so that a position-fixed measuring rod can be arranged therein. Relative to this measuring rod, the piston rod performs a linear reciprocating movement which can thus preferably be detected non-contact by the measuring rod and then evaluated.

[0004] Complex assembly is disadvantageous. According to the prior art, first the cylinder barrel is welded to the bottom closure, which is achieved as a high-current MAG welding. After cleaning the inner cavity thus formed, the stroke measuring system with the measuring rod has to be axially introduced through the cylinder barrel and arranged at the inner wall of the bottom closure. The difficult and time-consuming threading of the connecting wires is particularly disadvantageous. Likewise, ensuring and fixing the precise axial alignment of the measuring rod is difficult and time-consuming. Summary of the Invention

[0005] The object of the present invention is to provide a reliable, time-saving and cost-saving manufacturing method for a working cylinder with a position sensor, which enables high automation and provides high quality.

[0006] This object is solved by a manufacturing method having the features listed in claim 1. Preferred refinements follow from the dependent claims.

[0007] The method according to the invention is configured for manufacturing a working cylinder with a position sensor, the working cylinder having the structure described below.

[0008] The working cylinder according to the manufacturing method according to the invention has, as a basic element, a cylinder, a piston unit and a position sensor.

[0009] The cylinder of the working cylinder has, in a known manner, a cylinder barrel, a guide closure and a bottom closure.

[0010] The cylinder barrel has two oppositely arranged cylinder barrel ends. Here, it is the cylinder barrel end on the guiding side and the cylinder barrel end on the bottom side. A guiding closure is arranged at the cylinder barrel end on the guiding side, and a bottom closure is arranged at the cylinder barrel end on the bottom side. Below, the cylinder barrel end on the guiding side and the cylinder barrel end on the bottom side are also collectively referred to as the cylinder barrel ends, and the guiding closure and the bottom closure are also collectively referred to as closures. The cylinder inner cavity is constructed by the cylinder barrel and the closures arranged at its cylinder barrel ends.

[0011] The piston unit is arranged in the cylinder inner cavity. The piston unit is preferably constructed as an assembly consisting of a piston and a piston rod, wherein, in this configuration, the piston rod slides through the guiding closure. However, the piston unit can also be constructed in one piece, for example, and can also exist as a plunger piston. In the case of the proper use of the working cylinder, the piston unit performs a linear reciprocating motion.

[0012] The piston unit has an axially open hole on the bottom side and is thus constructed as a hollow piston unit. This axially open hole delimits a substantially cylindrical cavity, which provides space for arranging the measuring sensor rod.

[0013] In addition, the working cylinder has a position sensor, wherein the method according to the invention is based on the structure of the position sensor described below.

[0014] The position sensor has a base body, an axially extending measuring sensor rod, and an evaluation electronics. Here, it is not only an analog system but also a digital system.

[0015] The base body (also referred to as the sensor housing) preferably has a cylindrical basic shape and is arranged in the axially receiving hole of the bottom closure. This axially receiving hole is located on the inner side of the bottom closure. By the inner side is understood the side of the bottom closure that is axially directed towards the piston unit, which is part of the inner surface of the cylinder inner cavity.

[0016] The measuring sensor rod is arranged at the base body and, in the case of the prescribed arrangement of the base body in the cylinder bottom, is arranged axially and concentrically with respect to the cylindrical cylinder inner cavity and is oriented towards the guide closure. Indirectly via the base body, the positional relationship of the measuring sensor rod with respect to the bottom closure is thus also determined. Depending on the reciprocating movement, the measuring sensor rod penetrates into the axial bore of the hollow cylinder unit, where, however, in this variable positional relationship, the measuring sensor rod is the fixed element and the axial bore is the movable element. The penetration depth of the measuring sensor rod into the axial bore is detected inductively, where preferably an annular magnet is arranged at the hollow piston, which surrounds the measuring sensor rod and moves linearly with respect to the measuring sensor rod in the case of the reciprocating movement. In the case of the prescribed use, the assembly consisting of the base body and the measuring sensor rod is located in the pressure chamber of the working cylinder. Furthermore, preferably, an evaluation electronics is connected via connecting leads led out from the base body, which further evaluates the raw signal of the measuring sensor rod and provides it as a measuring signal for further position evaluation.

[0017] The method according to the invention for manufacturing the described working cylinder with a position sensor is characterized by the following method steps:

[0018] a) Engaging the base body of the position sensor into the receiving bore of the bottom closure to form a pre-assembled assembly,

[0019] b) Fixing the base body in the receiving bore,

[0020] c) Joining and connecting the cylinder barrel and the bottom closure in the case of arranging the measuring sensor rod in the cylinder inner cavity,

[0021] d) Joining the piston unit, the guide closure, and the cylinder barrel in the case of arranging the piston unit and the measuring sensor rod in the axial bore.

[0022] The method steps according to the invention are described in further detail below.

[0023] a) Engaging the base body of the position sensor into the receiving bore of the bottom closure to form a pre-assembled assembly

[0024] In this method step, the base body of the position sensor is axially inserted into the receiving bore of the bottom closure. Advantageously and different from the prior art, in this method step, the bottom closure is present without the joined cylinder barrel, so that there is free accessibility to the inner side of the bottom closure, and in particular, possible connecting leads can be introduced into the through-hole of the bottom closure without problems. Furthermore, advantageously, there is a free lateral passage for possible operating techniques in order to be able to guide the base body with a gripper in automated production or by an assembler in manual production and insert it into the receiving bore and fix it there.

[0025] b) Fix the base body in the receiving hole

[0026] After the base body is inserted into the receiving hole, the base body is fixed there in method step b). Here, the fixation is particularly understood as axial position fixation relative to the bottom closure. For example, the base body introduced into the interior of the hole is held in position by the pressure present in the piston chamber, or it can be fixed via a groove in the base body and radially arranged screws inserted into the groove.

[0027] It is considered important for the method according to the invention that a pre-assembled assembly is provided at this time, which consists of a bottom closure, a base body, and a measuring sensor rod.

[0028] c) Engage and connect the cylinder barrel and the bottom closure with the measuring sensor rod arranged in the cylinder inner cavity

[0029] In method step c), the engagement and connection of the pre-assembled assembly with the cylinder barrel are achieved. For this purpose, the cylinder barrel is axially guided towards the bottom closure, wherein the measuring sensor rod is positioned in the formed cylinder inner cavity. Preferably, the bottom closure has an annular joint with a boss, which forms an axial annular surface. Here, the cylinder barrel is pushed onto the annular joint such that its cylinder barrel annular surface abuts against the axial annular surface of the bottom closure. The connection is preferably realized in a form-fitting manner as laser welding in the case of constructing a radially arranged laser circumferential weld. It has surprisingly been found that by means of laser welding, a sufficiently low line energy can be introduced such that the heat-sensitive components of the position sensor, in particular the base body housing, are not damaged.

[0030] d) Engage the piston unit, the guide closure, and the cylinder barrel with the piston unit and the measuring sensor rod arranged in the axial hole

[0031] In method step d), the piston unit is first introduced into the guide closure. Subsequently, the assembly consisting of the guide closure and the piston unit is assembled, wherein the piston unit is introduced into the cylinder barrel such that the measuring sensor rod penetrates into the axial hole of the piston unit and is preferably arranged there without contact relative to the piston unit. The guide closure is engaged at the guiding-side end of the cylinder barrel and is preferably also fixed there in a form-fitting manner by laser welding.

[0032] According to the invention, method steps c) and d) can be carried out not only in the sequence c), d) but also in the sequence d), c).

[0033] In particular for the method according to the invention, it has surprisingly been found that by means of laser welding, the heat-affected zone can be limited in such a way that the position sensor already inserted is not thermally damaged either. Only through this idea contrary to the prior art are these special advantages made possible. By means of the free passage to the inside of the bottom closure according to the method of the invention in the case of using a position sensor, the connecting wires led out of the base body can be guided in a simple manner through the opening provided in the bottom closure for this purpose. In addition, there are laterally free passages, so that the base body can be grasped directly without problems. Preferably, this can also be achieved automatically by means of a gripper. Advantageously, the load on the measuring sensor rod is thus avoided and it is protected against possible damage. Furthermore, advantageously, the positioning of the base body relative to the bottom closure and its fixation are simplified. Advantageously, a working cylinder with a position sensor can thus be produced inexpensively and with high quality in large quantities for applications, for example in agriculture, where electronically evaluable position measurements at the working cylinder are also becoming increasingly important for satellite-assisted control.

[0034] According to a particularly advantageous variant of the method, it is characterized in that the bottom closure is connected in a material-locking manner to the cylinder barrel by means of a circumferential laser circumferential weld, and the laser circumferential weld is configured as a fluid-tight sealing plane, and method step c) is implemented by means of the execution of the laser welding of the bottom closure to the cylinder barrel in the case of producing the laser circumferential weld.

[0035] Another advantageous variant of the method is characterized in that the working cylinder is configured as a differential working cylinder, the piston unit has a piston and a piston rod, and an axial bore is arranged in the piston rod.

[0036] According to this advantageous variant, a differential working cylinder with a wide spread and high economic significance can be produced in a simple and reliable manner with a stroke measuring system.

[0037] According to another advantageous variant, the method is characterized in that method step d) is implemented before method step c). Thus, according to this improvement, first an assembly consisting of a cylinder barrel, a guide closure and a piston unit is assembled. Advantageously, thus, differently from the prior art, an assembly consisting of a cylinder barrel, a guide closure and a piston unit can be completed and then used for further assembly. Particularly advantageously, a sensitive position sensor is not included in this assembly, so that no precautions against damage need to be taken and there is also no obstruction due to the position sensor. Possible contaminants at the connection position between the guide closure and the end on the guide side can be removed unhindered before the final assembly with the pre-assembled assembly.

[0038] To produce the working cylinder, it is then only necessary to join this assembly to the preassembled assembly according to the invention. The measuring sensor rod can be introduced into the axial bore of the piston unit in a particularly simple manner. In the preferred connection of the preassembled assembly at the bottom closure with the bottom-side end of the cylinder barrel by means of laser welding, neither rust nor other contamination occurs.

[0039] According to another aspect of the invention, the method is characterized in that the bottom closure is connected to the cylinder by means of a threaded fit, and method step c) is performed by screwing the bottom closure to the cylinder.

[0040] The particular advantages described are also provided in this variant of the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described with reference to the following figures as an embodiment:

[0042] Figure 1 Cross-sectional illustration of a laser-coupled working cylinder with position sensor;

[0043] Figure 2 Cross-sectional illustration of pre-assembled components;

[0044] Figure 3 Cross-sectional illustration of pre-assembled components;

[0045] Figure 4 Cross-section of the working cylinder after the threaded connection is completed. DETAILED DESCRIPTION

[0046] Here, the same reference numerals in different figures refer to corresponding same features or components. These reference numerals are used in the description even if they are not shown in the relevant figure.

[0047] Figure 1 The structure of an exemplary embodiment of a differential cylinder is shown, which is connected according to the method by means of a laser annular weld.

[0048] The working cylinder has a cylinder 10 , a piston unit 20 and a position sensor 30 as basic components.

[0049] In this embodiment, the cylinder 10 is composed of a cylinder barrel 11 and closures 12, 13, wherein the guide closure 12 is arranged at the guide end 14 and the bottom closure 13 is arranged at the bottom end and the cylinder interior 16 is configured. The piston unit 20 is composed of a piston 22 and a piston rod 23 which is hollow by means of an axial hole 21. The piston rod 23 is guided through the guide closure 12 in a sliding manner.

[0050] The position sensor 30 consists of a base body 31, a measuring sensor rod 32 arranged thereon, and an evaluation electronic device 33.

[0051] The base body 31 is arranged in its receiving hole 17 in the bottom closure 13, and the bottom closure 13 is welded to the cylinder barrel 11 by means of a laser circumferential weld.

[0052] In the case of the reciprocating movement of the piston unit 20, its relative positional relationship with respect to the measuring sensor rod 32 received in the axial hole 21 changes linearly. The associated change in the magnetic field surrounding the measuring sensor rod 32 is detected by the measuring sensor rod, evaluated by the evaluation electronic device, and output by it as a measurement signal.

[0053] The method is further illustrated by means of Figure 2 the pre-assembled component 40 shown in

[0054] In method step a), the component consisting of the base body 31 and the measuring sensor rod 32 is axially inserted with the base body 31 into the cylindrical receiving hole 17 of the bottom closure 13. Advantageously, a spatially free passage to the two joining parts 31, 32, and 13 is provided here.

[0055] In method step b), the fixing of the base body 31 in the receiving hole 17 is achieved, wherein this is at this time carried out by an accurately matched axial pressing-in parallel to the joining process in method step a).

[0056] In the subsequent method steps c) and d), the piston unit 20 is inserted into the guide closure 12, the guide closure 12 is assembled at the cylinder barrel 11, and in addition, the piston unit 20 is introduced into the cylinder barrel 11. The connection between the bottom closure 13 of the pre-assembled component 40 and the cylinder barrel 11 is achieved by means of laser welding, thereby obtaining a laser circumferential weld 50 and at the same time forming a fluid-tight sealing plane.

[0057] Figure 3 and Figure 4 shows a modified embodiment, and the above description for Figure 1 and Figure 2 applies to this embodiment in the same way, provided that there are no subsequent special cases.

[0058] According to Figure 3 the pre-assembled component 40 is manufactured in method steps a) and b) and has an external thread (not shown) at the bottom closure 13. Correspondingly, the cylinder barrel 11 has an internal thread (not shown).

[0059] In method step d), first, a component consisting of the cylinder barrel 11, the guide closure 12, and the piston unit 20 with a piston 22 and a hollow-structured piston rod 23 is assembled.

[0060] Finally, in method step c), the assembly consisting of the cylinder barrel 11, the guide closure 12 and the piston unit 20 and the pre-assembly are axially joined to one another, where the measuring sensor rod 32 is introduced into the axial bore 21 here. Finally, the bottom closure 13 and the cylinder barrel 11 are screwed together by means of a mating formed by an external thread and an internal thread and are thus form-locked and connected to one another.

[0061] List of reference numerals

[0062] 10 Cylinder

[0063] 11 Cylinder barrel

[0064] 12 Guide closure

[0065] 13 Bottom closure

[0066] 14 Cylinder barrel end on the guide side

[0067] 15 Cylinder barrel end on the bottom side

[0068] 16 Cylinder inner cavity

[0069] 17 Axial receiving bore

[0070] 20 Piston unit

[0071] 21 Axial bore

[0072] 22 Piston

[0073] 23 Piston rod

[0074] 30 Position sensor

[0075] 31 Base body

[0076] 32 Measuring sensor rod

[0077] 33 Evaluation electronics

[0078] 40 Pre-assembly

[0079] 50 Laser circumferential weld

Claims

1. A method for manufacturing a working cylinder with a position sensor, wherein, The working cylinder has a cylinder (10), a piston unit (20) and a position sensor (30), wherein the cylinder (10) has a cylinder barrel (11), a guide closure (12) and a bottom closure (13), wherein the cylinder barrel has a cylinder barrel end (14) on the guide side and a cylinder barrel end (15) on the bottom side, the guide closure (12) is arranged at the cylinder barrel end on the guide side, and the bottom closure (13) is arranged at the cylinder barrel end on the bottom side, wherein the cylinder barrel (11) and the closures (12, 13) form a cylinder inner cavity (16), wherein the piston unit (20) is arranged in the cylinder inner cavity (16) and is configured as a hollow piston unit, has an axially open hole (21) on the bottom side and slides through the guide closure (12), wherein the position sensor (30) has a base body (31), the base body is arranged in an axially receiving hole (17) on the inner cavity side of the bottom closure (13), and has an axially extending measuring sensor rod (32), the measuring sensor rod is arranged in the axial hole (21), is connected to the base body (31) and is arranged relative to the bottom closure (13) in a fixed positional relationship, and has an evaluation electronic device (33), characterized by the following method steps, wherein the execution of the method steps is achieved in the order of a), b), c), d) or in the order of a), b), d), c): a) Engage the position sensor (30) with its base body (31) into the receiving hole (17) of the bottom closure (13) to form a pre-assembled assembly (40), b) Fix the base body (31) in the receiving hole (17), c) Join and connect the cylinder barrel (11) and the pre-assembled assembly (40) at the bottom closure (13) with the measuring sensor rod (32) arranged in the cylinder inner cavity (16), d) Join the piston unit (20), the guide closure (12) and the cylinder barrel (11) with the piston unit (20) and the measuring sensor rod (32) arranged in the axial hole (21).

2. The method according to claim 1, characterized in that, the bottom closure (13) is materially connected to the cylinder barrel (11) by means of a circumferential laser circumferential weld (50) and the laser circumferential weld (50) is configured as a fluid-tight sealing plane, and the method step c) is achieved in the case of making the laser circumferential weld (50) by performing a laser weld of the bottom closure (13) and the cylinder barrel (11).

3. The method according to any one of the preceding claims, characterized in that, the working cylinder is configured as a differential working cylinder, the piston unit (20) has a piston (22) and a piston rod (23) and the axial hole (21) is arranged in the piston rod (23).

4. The method according to any one of the preceding claims, characterized in that, the method step d) is achieved before the method step c).

5. The method according to any one of the preceding claims, characterized in that, the bottom closure (13) is connected to the cylinder barrel (11) by means of a threaded fit, and step c) of the method is achieved by performing the threaded tightening of the bottom closure (13) with the cylinder barrel (11).

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