WO2012059300A2

WO2012059300A2 - Coating device and method for the galvanic coating of an object in a controlled manner

Info

Publication number: WO2012059300A2
Application number: PCT/EP2011/067723
Authority: WO
Inventors: Milan Pilaski; Thorsten Czernotzky
Original assignee: Robert Bosch Gmbh
Priority date: 2010-11-02
Filing date: 2011-10-11
Publication date: 2012-05-10
Also published as: EP2635725A2; EP2635725B1; DE102010043206A1; WO2012059300A3

Abstract

The invention relates to a coating device for the galvanic coating of at least one object. The coating device has at least one vessel, in particular an electroplating reactor for receiving an electrolyte and at least one object. The vessel is connected to a current source, said current source being designed to be electrically connected to the object and to transfer a current through the object via the electrolyte and thus to apply a coating, in particular chrome, onto the object. According to the invention, the current source has an input for a control signal, said current source being designed to change a current strength of the current dependent on the control signal. The coating device also has a layer thickness detecting device, said layer thickness detecting device being designed to detect a layer thickness of the coating and to generate a layer thickness signal that represents the layer thickness. The coating device also has a processing unit which is connected to the at least one current source and the layer thickness detecting device and is designed to generate the control signal by means of a controller at least dependent on the layer thickness signal.

Description

description

title

Coating apparatus and method for controlled galvanic coating of an object

State of the art

The invention relates to a coating device for electroplating at least one object. The coating device has at least one vessel, in particular Galvano reactor for receiving an electrolyte and at least one object. The vessel is connected to a power source, wherein the power source is adapted to be electrically connected to the object and to send a current through the object via the electrolyte and thus to apply a coating, in particular chromium, to the object.

In coating devices known from the prior art, there is the problem that a coating thickness depends on the coating generating current and the coating time. As a rule, the current for producing the galvanic layer is set manually, so that layer thicknesses of the coating of a series of coated objects have different values relative to one another and a high layer thickness dispersion.

Disclosure of the invention

According to the invention, the current source has an input for a control signal, wherein the current source is designed to change a current intensity of the current as a function of the control signal. The coating device also has a layer thickness detection device, wherein the layer thickness detection device is designed to detect a layer thickness of the coating and to produce a layer thickness signal representing the layer thickness. The coating device also has a processing unit, which is connected to the at least one current source and the layer thickness detection device and designed to generate the control signal by means of a controller, preferably in accordance with a predetermined control function, at least in dependence on the layer thickness signal.

Thus, it can advantageously be achieved that layer thicknesses of a series of objects have a slight deviation from one another. The object is for example a valve piece, in particular a valve seat of the valve piece, the coating is for example chrome. Non-coated surfaces of the object can be covered, for example, by means of a mask, in particular plastic. As a result, the area of the object to be coated is advantageously limited, so that stray currents to other object locations of the object with a lower current density are avoided. The mask can thus advantageously achieve a precisely reproducible coating result.

In a preferred embodiment, the coating device has a plurality of vessels, in particular galvano-Raktoren. Preferably, the processing unit is designed to regulate the layer thickness, in particular the current and / or the coating time individually for each vessel, in particular independently of the other vessels as a function of the layer thickness signal. For this purpose, the processing unit may preferably form a control loop associated with the vessel for each vessel.

In a preferred embodiment, the processing unit has at least one controller, which is designed to generate the control signal as a function of the film thickness signal. The controller is preferably a proportional integral controller. By means of the proportional-integral controller, the coating time and / or current intensity of a current for coating the object can advantageously be regulated such that directly or closely successive detection results, in particular layer thickness values, of a series of detection results whose layer thicknesses differ greatly from one another are controlled by the proportional controller and, in a series of acquisition results, more widely spaced differences that gradually arise will be governed by the integral part of the regulator. Preferably, the layer thickness signal forms a control input of the regulator. The layer thickness For example, signal represents a sequence of layer thickness values, each layer thickness value representing a detection result of the layer thickness detection device from an object coated by the coating device at a time, in particular after completion of a coating process. Also conceivable is an average of layer thicknesses of several objects coated simultaneously by the coating device, as a layer thickness value to be evaluated by the controller. Thus, the layer thickness signal advantageously represents a temporal sequence of layer thickness values, wherein the layer thickness values for signal processing of the layer thickness signal can, for example, be evaluated to be equidistant from one another in terms of time. Thus, the controller can advantageously consider the film thickness signal as a time-dependent signal and perform the control frequency-dependent. Advantageously, the layer thickness signal for this purpose represents a multiplicity of layer thicknesses, wherein the processing unit is designed to use a predetermined number of layer thickness values registered in chronological succession for the regulation of the layer thickness. Each layer thickness value can represent a layer thickness after completion of a coating process.

In a preferred embodiment, the output of the regulator is a current and / or a coating time. Preferably, a simultaneous or during the coating process changing control of the

Amperage and coating time. For example, during the coating of the object, a current regulation can first take place, and then a time regulation until completion of the coating. Each layer thickness value of the layer thickness signal advantageously represents an average value, which is formed from a predetermined interval of layer thickness values of objects successively coated in a vessel, in particular galvano-reactor. Further advantageously, a maximum number of layer thickness values, which are averaged with one another, and a minimum number of layer thickness values, which are averaged with one another, can be predefined. For this purpose, the processing unit can be connected to a user interface, wherein the processing unit is designed to set a limit for the maximum number and a limit for the minimum number depending on a user interaction signal received from the user interface.

The following example describes a control of the layer thickness by means of a proportional-integral control of the coating time: The control parameters predetermined by means of a user interface are, for example, as follows:

Predetermined proportional factor kp: 4

Prescribed integral factor ki: 2

Actual time factor: 100%

Number of layer thickness values for averaging: 5

Layer thickness set point: 5 microns

The last 5 layer thickness values of coatings of a vessel detected by the layer thickness detection device are as follows:

Layer thickness value 1: 4.5 microns

Layer thickness value 2: 4.5 microns

Layer thickness value 3: 4.7 microns

Layer thickness value 4: 5.1 microns

Layer thickness value 5: 6.0 microns

The final layer thickness value is the layer thickness value 5, namely 6.0 microns.

The processing unit is configured to form an average of a predetermined number of the last layer thicknesses, in this example the average of the aforementioned five layer thickness values is 4.96 micrometers.

The processing unit is designed to calculate a change in the current and the coating time as follows:

change_t = - (last_value 6.0 - target_value 5.0) ^* kp 4 - (average 4.96 - target value 5.0) ^* ki 2

changej = - 4% + 0.08% = -3.92%

NewJ = OldJ + changej = 100% - 3.92% = 96.08%

What the variables mean:

change_t = change of coating time

last_value = last layer thickness value

target_value = layer thickness setpoint average = average

New_t = New coating time

Old_t = previous coating time

ki = given integral factor

kp = predefined proportional factor

The values of the variables of the example are each readjusted to the variables for clarification.

In a preferred embodiment, the controller is designed to regulate the coating time and / or the current intensity as a function of a predetermined characteristic curve, which is formed for example by a polynomial, wherein the characteristic curve represents a layer thickness as a function of the current intensity for coating.

In a preferred embodiment, the layer thickness detection device is an X-ray fluorescence spectrometer. By means of the X-ray fluorescence

Spectrometer can advantageously determine the layer thickness quickly and sufficiently accurately.

In a preferred embodiment, the layer thickness detection device is an eddy current layer thickness detection device, which is designed to detect the layer thickness as a function of an eddy current in the object.

For this purpose, the layer thickness detection device may for example comprise a measuring coil as a sensor, a frequency generator for generating an alternating magnetic field, a high-frequency measuring bridge, which is connected to the frequency generator and designed to detect the current consumed by the frequency generator and more preferably a multiplexer, which with several as Measuring coils formed sensors is connected so that advantageously the layer thicknesses of several objects for averaging the respectively detected layer thickness values can be performed. Advantageously, the Schick thickness can be detected by means of the eddy current when the object is in the electrolyte. Further advantageously, each layer thickness value can thus be detected in situ

Layer thickness, so that it is not necessary to wait for the layer thickness to be regulated until a new layer thickness value has been obtained after completion of the coating. tion and detection by the film thickness detection device is present as a control input.

The layer thickness measurement by means of an eddy current is based on the finding that in the case of a coated object which has a ferromagnetic base material, the magnetic permeability decreases with increasing layer thickness of a non-ferromagnetic coating, for example a chromium layer, so that an eddy current intensity of the eddy current increases.

In another embodiment, the layer thickness detection device is designed to detect a weight of the layer and, depending on the weight - with knowledge of the layer thickness and the assumption of a uniform layer thickness - to determine the layer thickness and to generate the corresponding layer thickness signal. The layer thickness can advantageously be determined inexpensively and quickly by means of the layer thickness detection device formed in this way.

The invention also relates to a method for electroplating a

Object.

In the method, the object is coated in an electrolyte by means of a current, wherein the current is regulated by means of a regulator and at least one layer thickness of the coating is detected as a control input variable. The layer thickness is detected, for example, if the object is outside the

Electrolyte is located.

The layer thickness is preferably detected by means of X-ray fluorescence spectrometry.

In another embodiment, an eddy current is generated in the object and the layer thickness is detected as a function of the eddy current generated in the object.

In another embodiment of the method, the layer thickness-in particular outside the electrolyte-is detected by weighing the object or a test object coated together with the object. The test object can advantageously have a standardized shape and size, so that a scale for detecting the weight only needs to be designed to receive the test object. The current for coating by means of a mask is preferably limited to a partial area of the object to be coated. As a result, stray currents to other object areas are advantageously avoided, which causes an exact control of the layer thickness. The invention will now be described below with reference to figures and further embodiments. Further advantageous embodiments will become apparent from the features described in the figures and from the features described in the dependent claims.

FIG. 1 shows an exemplary embodiment of a coating apparatus for galvanic coating with three coating units operating independently of one another, each of which has a vessel and a controllably designed current source connected to a regulator, the regulator being designed to regulate the coating individually for each vessel;

FIG. 2 shows two distribution functions of detected layer thicknesses of a sequence of detection results, one distribution function representing a scattering of the layer thickness with controlled coating time and / or coating current by means of a proportional integral regulator and another distribution representing a variation of the layer thickness with manual setting of coating time and / or coating current.

FIG. 1 shows an exemplary embodiment of a coating device for electroplating, at least one object. The coating apparatus

1 comprises at least one vessel, in this embodiment a vessel 5, a vessel 6 and a vessel 7. The vessels 5, 6 and 7 are each designed to receive an electrolyte and at least one object to be coated.

The coating apparatus 1 also has a processing unit 10, which in this embodiment is designed as a microcontroller or microprocessor. The coating apparatus 1 also has a layer thickness detection device 50. The layer thickness detection device 50 in this exemplary embodiment is an X-ray fluorescence spectrometer with an X-ray transmitter 52 and an X-ray receiver 54 for X-ray fluorescence radiation 57 emitted by an object.

The X-ray fluorescence spectrometer is designed to detect the layer thickness as a function of at least one angle of the reflected fluorescence beams. sen. The at least one angle is, for example, a glancing angle of a Bragg reflection.

The X-ray receiver 54 is connected on the output side via a connecting line 37 to the processing unit 10. The processing unit 10 has a proportional-integral controller 18. The processing unit 10 is connected on the output side via a connecting line 30 to a current source 20. The current source 20 is connected on the output side via a connecting line 36 to the vessel 5, and there with a - not shown -Verbindungsleitung for connecting to the object and at least one anode, such as a platinum or lead anode. The vessel 5 holds in this embodiment an electrolyte 12, for example, an aqueous chromium trioxide solution in stock. Shown is also an object 60, which is provided for at least partial coating by means of a layer, for example a chromium layer.

The vessel 5 is connected to the layer thickness detection device 50 by means of a transport path 42. The transport path 42 may include, for example, a transport device.

The processing unit 10 is also connected on the output side via a connecting line 32 to a power source 22. The current source 22 is connected on the output side via a connecting line 38 to the vessel 6. The vessel 6 holds in this embodiment an electrolyte 14 in stock. An object 62 is exemplarily immersed in the electrolyte. The vessel 6 is connected on the output side by means of a transport path 44 with the layer thickness detection device 50. The processing unit 10 is further connected on the output side via a connecting line 34 to a current source 24. The current source 24 is connected on the output side via a connecting line 40 to the vessel 7. The vessels 5, 6 and 7 each have a lid and are formed from a material resistant to the electrolyte, for example polyfluoroethylene. The current sources 20, 22 and 24 are each designed to generate a current for the galvanic coating of an object and to send this to the output side of the respective vessel. The current sources 20, 22 and 24 are each designed to generate the current intensity as a function of a control signal received on the input side from the processing unit 10.

By means of the controllably formed current sources 20, 22 and 24, the vessels 5, 6 and 7 respectively connected to the current sources, further by means of the transponder Ports 42, 44 and 46, with the film thickness detection device 50 and by means of the film thickness signal generated by the film thickness detection device 50, which is fed back to the processing unit 10, a control loop is formed. The processing unit 10 is formed, by means of the proportional-integral controller 18 or by means of a characteristic controller 19, the

Layer thickness for each vessel to regulate individually and to specify as a control output the current, in particular the current intensity and / or a coating time for coating the object. The processing unit 22 is also connected on the input side via a connecting line 72 to a user interface 70 and can receive a user interaction signal from there. The user interaction signal, for example, represents a control parameter, in particular a limit for averaging of layer thickness values. Furthermore, a predetermined control function or a regulator for regulating the layer thickness can be selected via the user interface as a function of the user interaction signal. Shown is also a user's hand 74, which can generate the user interaction signal, for example, by touching the user interface. In this exemplary embodiment, the user interface is designed as a touch-sensitive screen which, depending on a touch, can generate a user interaction signal representing the location of the touch.

It is also conceivable to control and / or regulate a temperature of the electrolyte, an electrolyte flow of an electrolyte circuit or a pulse duration of a pulse-width-modulated coating current, generated by the current sources connected to the vessels.

The vessel 7 is connected by way of example with a fluid circuit. Starting from the

Vessel 7 connects a fluid line 92, the vessel 7 with a particular heatable storage vessel 100, which is connected via a fluid line 96 with a pump 90. The pump 90 is connected on the output side via a fluid line 94 to the vessel 94. By means of the fluid circuit, a uniform electrolyte concentration distribution and temperature distribution can be achieved.

The pump 90 is connected to the processing unit 10 via a control line 102 and can receive from the processing unit 10 a control signal representing a flow rate and generate the fluid circuit in response to the control signal. The vessels 12 and 14 can each be integrated into a fluid circuit like the vessel 7.

The coating apparatus 1 has in this embodiment, three vessels, in particular the vessel 5, 6 and 7. Also conceivable is a coating device with a plurality of vessels, in particular more than the three vessels shown, which are each designed to coat at least one object independently of one another. Shown is the object 60 in the vessel 5, which is transported after the coating over the transport path 42 to the layer thickness detection device 50 and is shown there as an object 60 'to be measured.

Shown is also an object 62, which is coated in the vessel 6 and an object 64, which is coated in the vessel 7.

FIG. 2 shows two distribution functions, namely a distribution function 80 and a distribution function 82. FIG. 2 also shows a setpoint value for a layer thickness 84, which is included by the distribution function 80 and the distribution function 82. The distribution functions 80 and 82 each represent a layer thickness distribution which has been determined on the basis of a multiplicity of coatings of mutually different objects. The distribution function 80 represents a normally-distributed, in particular a Gauss-distributed

Layer thickness distribution for layer thicknesses of objects which have been coated by means of the coating device 1 shown in FIG. The layer thickness distribution 82 represents a layer thickness distribution of layer thicknesses of objects which have been produced by means of a coating device which has a manual adjustment for the coating flow and the coating time. Visible is a large dispersion of

Layer thicknesses of the layer thickness distribution 82 and a small dispersion of the layer thicknesses of the layer thickness distribution 80th

Claims

claims

1. Coating device (1) for electroplating at least one object (60, 62, 64),

wherein the coating device (1) comprises at least one vessel (5, 6, 7) for receiving an electrolyte (12, 14, 16) and at least one object (60, 62, 64), the vessel (5, 6, 7) is connected to a power source (20, 22, 24), wherein the power source (20, 22, 24) is adapted to be electrically connected to the object (60, 62, 64) and through the object (60, 62, 64 ) to send a current across the electrolyte (12, 14, 16) to apply a coating to the object (60, 63, 64),

characterized in that

the current source (20, 22, 24) has an input for a control signal and is designed to change a current intensity as a function of the control signal, and the coating device (1) has a layer thickness detection device (50) which is designed to detect a layer thickness (80, 82) of the coating and a layer thickness (80, 82) representing

To produce a layer thickness signal, and the coating device (1) has a processing unit (10) which is connected to the at least one current source (20, 22, 24) and the layer thickness detection device (50) and configured to generate the control signal by means of a regulator (18, 19 ) at least in response to the film thickness signal.

2. Coating device (1) according to claim 1,

characterized in that

the controller (18) is a proportional-integral controller.

3. Coating device (1) according to claim 1 or 2,

characterized in that the controller is designed to regulate the coating time and / or the current intensity as a function of a predetermined characteristic curve, the characteristic curve representing a layer thickness as a function of the current intensity for coating.

4. Coating device (1) according to one of the preceding claims, characterized in that

the layer thickness detection device (50) is an X-ray fluorescence spectrometer.

5. Coating device (1) according to one of the preceding claims, characterized in that

the layer thickness detection device (50) is designed to detect a weight of the coating and to determine the layer thickness as a function of the weight.

6. Coating device (1) according to one of the preceding claims, characterized in that

the film thickness detecting device (50) is an eddy current film thickness detecting device configured to detect the film thickness depending on an eddy current in the object (60 ').

7. Method for electroplating an object,

in which the object (60, 62, 64) is coated in an electrolyte by means of a current,

characterized in that

the current is regulated by means of a regulator (18) and a layer thickness of the coating is detected as a control input variable when the object is outside or inside the electrolyte.

8. The method according to claim 7,

characterized in that

the layer thickness is detected by X-ray fluorescence spectrometry.

9. The method according to any one of the preceding claims 7 or 8,

characterized in that the layer thickness - in particular outside the electrolyte - is detected by weighing the object or a test object coated together with the object.

10. The method according to any one of the preceding claims 7 to 9,

characterized in that

an eddy current is generated in the object and the layer thickness is detected as a function of the eddy current generated in the object.

1 1. The method according to any one of the preceding claims 7 to 9,

characterized in that

the current for coating by means of a mask is limited to a partial area of the object to be coated.