JPH1133757A - Welding metal powder feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to feed a fixed quantity of welding metal powder quickly to the welding part by calculating an instruction to a nozzle driving means so as to make a detected powder flow rate matches a given target. The calculation is made with a use of the best control parameter chosen in accordance with the detected value of the upper, bottom positions of the nozzle pin installed on a gravity dropping type device. SOLUTION: A controller 50 inputs an output signal of the flow rate sensor 15, collects a nozzle pin position X to be detected by an encoder 14a and a data on a detected value Q then detected by the flow rate sensor 15 and compiles a Q-X instruction map while moving a nozzle pin from the bottom position to the upper position by a servo motor 14. In order to make this non- linear map suitable to a PI control, a parameter gain for control is set by making a line approximation of each Q-X section respectively. From the control parameters, a set of the best control parameter is chosen in correspond to the output of the encoder 14a. By using this, the instruction value to the servo motor 14 is so calculated that an actual value of the flow rate Q matches the previously set target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding metal powder supply apparatus for overlay welding by laser welding, and more particularly to a flow rate control during powder supply.

[0002]

2. Description of the Related Art When a surface of a valve seat of an engine cylinder head or the like is coated with a copper alloy or the like in order to impart wear resistance or corrosion resistance, or when repairing a worn-out portion during transportation of parts. Is performed by laser welding. This build-up welding method using laser welding is a method in which a powder of a wear metal having wear resistance or the like is supplied from the tip of a powder supply nozzle to a weld portion on the surface of a base material, and a laser beam focused on the supplied weld metal powder is supplied. By irradiating the beam, the weld metal powder is melted, and the weld metal is raised on the surface of the base material.

As a powder supply nozzle for supplying welding metal powder to the surface of a base material, for example, as shown in FIG. 9, there is a powder supply nozzle 11 of a gravity drop type provided with a vertically movable nozzle pin 12. The powder supply nozzle 11 has a structure in which when the nozzle pin 12 is raised, the powder falls by gravity and is supplied to the base material surface from the nozzle tip (discharge port). The vertical movement of the nozzle pin 12 is performed by a pneumatic cylinder, an electric servomotor, or the like.

[0004]

However, since the tip of the nozzle pin 12 is usually curved, if the nozzle pin 12 is raised singly, a constant flow rate of powder (for example,
4 g / sec). In addition, clogging may occur during the supply process. Therefore, as a result, the supply amount of the powder to the surface of the base material becomes non-uniform, and there is a possibility that the buildup (quality) NG may occur.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a welding metal powder supply apparatus capable of rapidly supplying a constant amount of welding metal powder to a weld portion. Aim.

[0006]

In order to achieve the above-mentioned object, the invention according to the first aspect of the present invention is directed to a method of forming a surface of a base metal by gravity dropping a weld metal powder through a powder supply nozzle having a vertically movable nozzle pin. In the welding metal powder supply device for supplying to the nozzle, powder flow rate detection means for detecting the flow rate of the powder discharged from the powder supply nozzle, nozzle pin drive means for driving the nozzle pin up and down, and nozzle pin for detecting the position of the nozzle pin Position detecting means, selecting a set of optimal control parameters according to the output of the nozzle pin position detecting means from a plurality of preset control parameters, and using the selected control parameters, A finger pointing to the nozzle pin driving means such that an actual value of the flow rate detected by the flow rate detecting means matches a preset target value. Calculating a value, and having a control means for outputting.

According to the structure of the present invention, the nozzle pins are driven up and down by the nozzle pin driving means, but the flow rate of the powder discharged from the powder supply nozzle increases as the nozzle pins rise, and decreases as the nozzle pins drop. The control means selects one set of optimal control parameters according to the output (nozzle pin position) of the nozzle pin position detection means from a plurality of preset control parameters, and uses the selected control parameters to A command value to the nozzle pin driving means is calculated such that the actual value of the flow rate detected by the powder flow rate detecting means matches a preset target value, and the obtained command value is output to the nozzle pin driving means. This allows
The nozzle pin moves up and down by an amount corresponding to a command value obtained by an optimal control parameter corresponding to the nozzle pin position, and the followability of the actual flow rate to the target flow rate is improved.

According to a second aspect of the present invention, in the welding metal powder supply apparatus according to the first aspect, the plurality of sets of control parameters include a method for converting characteristic data indicating a relationship between a nozzle pin position and a powder flow rate into a predetermined method. Is obtained by performing linear approximation for each section divided by.

According to the configuration of the present invention, the plurality of sets of control parameters are obtained by linearly approximating characteristic data indicating the relationship between the nozzle pin position and the powder flow for each section divided by a predetermined method. In general, since the characteristic data is non-linear, the characteristic data is divided into several sections for the nozzle pin position, and a linear approximation is performed for each section to obtain control parameters for each section reflecting the characteristic data. be able to. By linearizing such non-linear characteristics, it becomes easy to control the flow rate with respect to the target value.

According to a third aspect of the present invention, in the welding metal powder supply device according to the first or second aspect, the command value is calculated based on a deviation between the target value and the actual value. It is characterized by.

According to the configuration of the present invention, the command value to the nozzle pin driving means is calculated based on the deviation between the target value and the actual value of the flow rate. The amount of becomes large. Therefore, the response is improved.

According to a fourth aspect of the present invention, in the welding metal powder supply device according to the third aspect, the command value is:
It is obtained by a proportional + integral operation.

According to the structure of the present invention, the amount of vertical movement of the nozzle pin is controlled by the proportional + integral operation. Therefore, by setting the degree of the integral operation appropriately, it is possible to obtain a stable and quick response without offset. It is possible to perform compatible control.

[0014]

According to the first aspect of the present invention, since the actuator moves up and down by an amount corresponding to a command value obtained by an optimum control parameter corresponding to the nozzle pin position, the followability of the actual flow rate to the target flow rate is improved. In addition, it is possible to speed up the quantitative supply of the welding metal powder to the welded portion, and to quickly supply a target flow rate.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the nonlinear characteristic is linearized, so that the flow rate control with respect to the target value can be easily performed. .

According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, the amount of vertical movement of the nozzle pin is controlled based on the deviation.
And the speed of the quantitative supply of the weld metal powder to the welded portion is improved.

According to the fourth aspect of the invention, in addition to the effect of the third aspect of the invention, the amount of vertical movement of the nozzle pin is controlled by the proportional + integral operation. Can be performed, and the ability to follow the target flow rate is improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Here, an example is given in which build-up welding by laser welding is performed on the surface of the valve seat of the cylinder head of the engine.

FIG. 1 is a schematic configuration diagram showing a welding metal powder supply apparatus and a laser welding apparatus main body according to an embodiment of the present invention. As shown in the figure, a cylinder 1 filled with a carrier gas composed of an inert gas such as helium gas or argon gas is connected to a gas inlet of a powder mixing device 2 via a valve, and a copper alloy (Ni , Al, Fe)
The tank 3 containing welding metal powder having an average particle size of 60 μm is connected to the powder input port of the powder mixing device 2 via a valve.

One end of a supply hose 4 is connected to an outlet of the powder mixing device 2. The other end of the supply hose 4 is connected to a welding metal powder supply device (hereinafter simply referred to as “powder supply device”) 10. It is connected to the main body, that is, the powder inlet 11 a of the powder supply nozzle 11. Also, the powder supply nozzle 11
The powder discharge nozzle 11 is connected to the powder outlet 11b.

This powder supply device 10 is of a gravity drop type having a vertically movable nozzle pin 12 inside a powder supply nozzle 11, and when the nozzle pin 12 rises, a powder outlet 11b is opened to open the powder outlet 11b. Is dropped by gravity and supplied from the tip end (discharge port) of the powder discharge nozzle 13 to the surface of the base material. Nozzle pin 12
Are driven up and down by a nozzle pin up / down servomotor 14 as nozzle pin driving means. Further, a flow rate sensor 15 as a powder flow rate detecting means is attached to the tip of the powder supply nozzle 12.

FIG. 2 is a sectional view showing an example of the powder supply apparatus 10. As a mechanism for moving the nozzle pin 12 up and down by the servomotor 14, a ball spline 40 is used here. That is, the nozzle pin 12 is connected to the ball spline bush 41, and the output shaft of the nozzle pin vertical servomotor 14 is connected to the ball spline shaft 42 via the coupling (coupling) 43. Thus, the nozzle pin 12 moves up and down while turning. Specifically, for example, 2
Move up and down 20 mm while rotating 70 °. In the figure,
44 is a locking pin, 45 is a dust seal for preventing powder, 46 is a wiper for preventing lock, and P is a powder mixing device 2.
Respectively show the welding metal powders supplied from the Company.

In FIG. 1, reference numeral 20 denotes a laser welding apparatus main body. A laser beam 22 output from a laser oscillator 21 is transmitted to a predetermined position by a mirror 23, and the laser beam 22 is The beam is focused on the welded portion 31 on the surface 30. The build-up by laser welding using the powder supply device having the above configuration is shown in FIG.
As shown in the figure, the tip of the powder discharge nozzle 13 is pointed in advance to the welded portion 31 on the surface of the base material 30, and the mirror 23 and the condenser lens 24 are adjusted so that the laser beam 22 can be focused at the welded portion 31. Set to.

Then, the welding metal powder is mixed with the carrier gas in the powder mixing device 2, and the carrier gas and the powder are passed through the supply hose 4 by the gas pressure of the carrier gas so that the powder supply nozzle 11 of the powder supply device 10 ( ). From the carrier gas and the powder supplied into the powder supply device 10 (the powder supply nozzle 11 thereof), the weld metal powder is separated from the carrier gas by an appropriate method. The separated powder is temporarily stored in the powder supply nozzle 11.

When the nozzle pin 12 is raised in this state, the powder outlet 11b is opened, and the powder drops by gravity and is discharged from the tip of the powder discharge nozzle 13 toward the welding portion 31. Further, the laser welding device main body 20 is operated in synchronization with the supply of the welding metal powder, and the laser beam 22 focused by the condenser lens 24 is irradiated on the supplied welding metal powder, and the powder is applied to the mother metal. It is built up on the surface of the material 30. 32
Indicates a weld metal that has been overlaid.

In the present invention, in order to provide a powder supply apparatus 10 capable of supplying a fixed amount with good tracking ability to the target flow rate, the nozzle pin vertical servomotor 14 is controlled so that the actual flow rate quickly matches the target value. . By controlling the nozzle pin vertical servomotor 14, the nozzle pin 12 moves up and down. The flow rate Q of the powder discharged from the powder supply nozzle 11 is controlled by such vertical movement of the nozzle pin 12.

FIG. 3 is a configuration diagram of a control system of the powder supply device 10. The controller 50 functions as a control unit, and is configured by, for example, a microcomputer. The flow sensor 15 for detecting the flow rate of the powder supplied from the powder supply nozzle 11 is connected to the controller 50. In addition, a servo amplifier 51 that drives the nozzle pin vertical servomotor 14 is connected to the controller 50. The controller 50 receives a flow signal from the flow sensor 15 and issues a command signal (vertical amount command value) to the nozzle pin vertical servomotor 14 such that the detected value Q (actual flow rate) matches the target value R. Xm is generated and output to the servo amplifier 51.

FIG. 4 is a block diagram of the control system shown in FIG. The controller 50 controls the nozzle pin vertical servomotor 14 by a proportional-integral operation (PI
Control function), the proportional gain P and the integral gain I
Has multiple sets of control parameters by combining
The control unit includes a PI control unit 52 that performs a control operation and a gain scheduler 53 that selects a control parameter to be used.
Reference numeral 14a denotes an encoder for detecting the rotational position of the nozzle pin vertical servomotor 14. The output signal of the encoder 14a is supplied to the servo amplifier 51 as a position feedback signal on the one hand, and the gain is output as information on the nozzle pin position X on the other hand. This is given to the scheduler 53.

The basic principle of the flow control in the present invention is based on a QX command map (see FIG. 6) which is characteristic data indicating a relationship between the position X of the nozzle pin and the flow rate Q of the powder to be discharged. The flow rate Q of the powder supplied from the nozzle 11 is set to P
It is controlled by I control.
Since the X command map generally has non-linear characteristics, the flow rate Q cannot be controlled by ordinary PI control. Therefore, the nozzle pin position X is divided into several sections, and a control parameter (PI parameter) for each section is set by linearly approximating the curve of the QX command map for each section. , The scheduling (selection) of the optimum PI gain is performed.

The controller 50 receives the signals from the encoder 14a and the flow rate sensor 15 to create a QX command map, and sets the control parameter gain by linear approximation for each section, or sets the control parameter gain. The powder supply control is performed using the parameter gain.

FIG. 5 is a flowchart of a process for creating a QX command map and setting a gain.

First, the controller 50 inputs the output signal of the flow rate sensor 17 while driving the nozzle pin vertical servomotor 14 to move the nozzle pin 12 from the lower limit position (0), which is the origin, to the upper limit position (Xmax). Then, data of the position X of the nozzle pin 12 (corresponding to the rotational position of the servomotor 14) detected by the encoder 14a and data of the detection value Q of the flow sensor 17 at that time are collected (step S1). As described above, the position X of the nozzle pin 12 is set to the origin when the nozzle pin 12 is at the lower limit position (that is, the powder outlet 11b is closed).
In addition, in order to ensure the accuracy of the data, it is preferable that the data collection process of step S1 be performed a plurality of times at a time.

In the next step S2, regarding the collected nozzle pin position X and the flow rate Q, the horizontal axis represents the nozzle pin position X,
Taking the flow rate Q on the vertical axis and plotting the values, a QX command map as shown in FIG. 6 is created. When data sampling is performed a plurality of times in step S1, an appropriate process such as averaging of data is performed, and a QX command map is created based on the processed data. Therefore, this QX command map reflects the characteristics of the actual device.

In the next step S3, a control parameter gain is set by performing linear approximation for each QX section in order to make the QX command map, which is a non-linear characteristic, suitable for PI control.

The details of this processing are as follows, for example. In the description, FIG. 7 is referred to as appropriate.

First, with respect to the points on the curve of the QX command map, the points where the differential value (dQ / dX), that is, the slope of the tangent line changes abruptly, are examined. Then, the values of the nozzle pin positions X corresponding to these points are set in the order of x1, x2,.
And In the example of FIG. 7, n = 4. Then, after connecting the points on the curve with straight lines, the inclination of each straight line is obtained, and they are set as a1, a2, ..., an in order. However, when the nozzle pin position X is larger than the final point xn, X
Is constant (maximum) regardless of the value of (Q = Q
max). That is, in the example of FIG. 7, the straight line approximated in each section is as follows: 0 ≦ X <x1, Q = a1Xx1 ≦ X <x2, Q = a2X + b2 x2 ≦ X <x3, Q = a3X + b3 When x3 ≦ X <x4, Q = a4X + b4x4 ≦ X, and Q = Qmax. Thereafter, control parameter gains corresponding to the slopes a1, a2,..., An are determined from a table in which an adjusted PI gain corresponding to an arbitrary slope is determined in advance.
The control parameter gains are proportional gain P and integral gain I
, And a plurality of sets are set corresponding to each section, and are sequentially set as (P1, I1), (P2, I2),..., (Pn, In). That is, in the example of FIG. 7, four sets of control parameter gains (P1, I1), (P2, I2), (P3, I3), (P
4, I4) are set. And, based on this result,
A controller 50 having a configuration as shown in FIG. 4, specifically, a PI control unit 52 and a gain scheduler 53 as shown in FIG. 4 are automatically created. However, when x4 ≦ X, Q
= Qmax, the gain is not set, and the command value is uniformly set to Xm = Xmax.

FIG. 8 is a flowchart of the powder supply control realized by the configuration of the block diagram of FIG. 4 created in this way.

Upon input of the start signal, the controller 50 first sets a target flow rate (flow rate target value) R (step S11). The setting of the target flow rate R is performed by inputting a flow rate setting signal by a predetermined switch operation by the operator.

When the target flow rate R is set, the flow rate sensor 1
5 (actual value) Q is input (step S12),
A deviation (flow rate deviation) e between the target value R and the detection value Q is calculated (step S13). The flow deviation e is obtained by subtracting the detection value Q from the target value R (e = RQ).

When the flow rate deviation e is obtained, a pulse signal from the encoder 14a of the nozzle pin vertical servomotor 14 is input to recognize the nozzle pin position X (step S14). Specifically, a gain is selected (scheduled) according to the section where the detected current nozzle pin position is (step S15), and a command signal (a vertical amount command) to the nozzle pin vertical servomotor 14 is made using the selected gain. Value) Xm is calculated (step S16). Here, the nozzle pin up / down servomotor 14 is controlled by a proportional + integral operation except in the case of x4 ≦ X, so that the up / down amount command value Xm to the nozzle pin up / down servomotor 14 is
For example, in the example of FIG. 7, according to the value of the nozzle pin position X, the following expressions are respectively provided: 0 ≦ X <x1, Xm = P1 (1 + I1 / s) ex1 ≦ X <x2, Xm = P2 When (1 + I2 / s) ex2≤X <x3, Xm = P3 (1 + I3 / s) ex3≤X <x4, when Xm = P4 (1 + I4 / s) ex4≤X, Xm = Xmax Given.

The vertical command value X obtained in step S16
m is output to the servo amplifier 51 (step S1).
7). As a result, the servo amplifier 51
The nozzle pin vertical servomotor 14 is rotated by the command value Xm while receiving the position feedback signal from a, and the nozzle pin 12 is moved up and down by a distance corresponding to the command value Xm. When the command value Xm is plus (+), that is, when the actual value Q is smaller than the target value R, the movement direction of the nozzle pin 12 rises to increase the flow rate, and when the command value Xm is minus (-). That is, when the actual value Q is larger than the target value R, the flow is lowered to reduce the flow rate. Thus, the actual flow rate Q approaches the target value R.

Thereafter, in step S18, it is determined whether or not the supply has been completed based on the presence or absence of the input of the stop signal. If NO, that is, if the supply has not been completed, the process returns to step S12, and a series of operations is performed. Repeat the process.

Therefore, according to the present embodiment, the control PI gain is set by linearly approximating the nonlinear QX command map for each section, and the optimum PI gain is set according to the section of the nozzle pin position. And PI control of the amount of vertical movement of the nozzle pin based on the flow rate deviation improves the followability of the actual flow rate to the target flow rate, and speeds up the quantitative supply of the welding metal powder to the weld. , The target flow rate can be quickly supplied.

Further, even if there is a change in the valve or a change in the condition (temperature, humidity, etc.), it can be dealt with only by creating the QX command map.

The structure of the powder supply device 10 is not limited to that shown in FIG. 2, and the present invention is applicable to all gravity-falling powder supply devices.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a welding metal powder supply device and a laser welding device main body according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a powder supply device.

FIG. 3 is a configuration diagram of a control system of the powder supply device.

FIG. 4 is a block diagram of a control system shown in FIG. 3;

FIG. 5 is a flowchart of a process for creating a QX command map and setting a gain.

FIG. 6 is a characteristic diagram showing an example of a QX command map.

FIG. 7 is a diagram provided for explanation of linear approximation for each QX section.

8 is a flowchart of powder supply control realized by the configuration of the block diagram of FIG.

FIG. 9 is a schematic diagram showing a tip of a powder supply nozzle of a gravity drop method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Welding metal powder supply apparatus 11 ... Powder supply nozzle 12 ... Nozzle pin 14 ... Servo motor for nozzle pin up / down (nozzle pin drive means) 14a ... Encoder (nozzle pin position detection means) 15 ... Flow rate sensor (powder flow rate detection means) 30 ... Base material 50 ... Controller (control means)

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI // B23K 10/02 501 B23K 10/02 501A

Claims (4)

[Claims] 1. A welding metal powder supply device for supplying a powder of a welding metal to a surface of a base material by gravity drop through a powder supply nozzle having a nozzle pin capable of moving up and down. A powder flow rate detecting means for detecting a flow rate, a nozzle pin driving means for driving the nozzle pin up and down, a nozzle pin position detecting means for detecting the position of the nozzle pin, and the nozzle pin position from a plurality of preset control parameters. A set of optimal control parameters is selected according to the output of the detecting means, and using the selected control parameters, the actual value of the flow rate detected by the powder flow rate detecting means matches the preset target value. Control means for calculating and outputting a command value to the nozzle pin driving means as described above. Metal powder feeder. 2. The method according to claim 1, wherein the plurality of sets of control parameters are obtained by linearly approximating characteristic data indicating a relationship between a nozzle pin position and a powder flow for each section divided by a predetermined method. 2. The welding metal powder supply device according to 1. 3. The welding metal powder supply device according to claim 1, wherein the command value is calculated based on a deviation between the target value and the actual value. 4. The apparatus according to claim 3, wherein the command value is obtained by a proportional + integral operation.