Laser cladding method and laser cladding apparatus

Abstract

To provide a laser clad processing technique that can suppress the occurrence of quality defects.SOLUTION: A laser clad processing method includes: a processing step of forming a bead in a valve seat part of a cylinder head according to a set processing condition; a measuring step of measuring the bead shape that has been formed in the processing step and contains at least a portion other than a start part of formation of the bead; a calculation step of calculating correction values for the laser output strength and the powder feed amount included in the processing condition according to the difference between the bead shape measured in the measurement step and the target bead shape; and a setting step of setting the processing condition in the next processing step according to the correction value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a laser cladding processing method and a laser cladding processing apparatus.

Background Art

[0002] As a means for increasing the design freedom of the ports of the cylinder head for an automobile engine, a laser cladding technique for directly building up a wear-resistant powder with a laser to form a valve seat is known. In Patent Document 1, a technique for measuring the wall thickness of the processing start portion of the valve seat groove and controlling the laser output and powder supply amount according to the wall thickness value is described. Thereby, it is possible to suppress the occurrence of an unwelded state or a dilution state and suppress the occurrence of defective quality.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even when controlling the laser output and powder supply amount according to the wall thickness value of the processing start portion, defective quality may occur. Therefore, another technique capable of suppressing the occurrence of defective quality has been demanded.

Means for Solving the Problems

[0005] The present disclosure has been made to solve the above-described problems and can be realized in the following forms. A laser cladding method is provided according to one embodiment of the present disclosure. This laser cladding method includes: a processing step of forming a bead on the valve seat portion of a cylinder head according to set processing conditions; a measurement step of measuring the bead shape of the bead formed in the processing step, including at least a portion other than the starting point of bead formation; a calculation step of calculating correction values ​​for the laser output intensity and powder supply amount included in the processing conditions according to the difference between the bead shape measured in the measurement step and a target bead shape; and a setting step of setting the processing conditions for the next processing step according to the correction values. The processing conditions further include the timing of the laser output and the timing of the powder supply.

[0006] (1) A laser cladding method is provided according to an embodiment of the present disclosure. This laser cladding method includes: a processing step of forming a bead on the valve seat portion of a cylinder head according to set processing conditions; a measurement step of measuring the bead shape of the bead formed in the processing step, which includes at least a portion other than the starting portion of the bead formation; a calculation step of calculating correction values ​​for the laser output intensity and powder supply amount included in the processing conditions according to the difference between the bead shape measured in the measurement step and the target bead shape; and a setting step of setting the processing conditions for the next processing step according to the correction values. The inventors discovered that not only the difference between the shape of the bead formation starting point and the target bead shape, but also the difference between the shape of the parts other than the starting point and the target bead shape, affects the quality of the processing. According to this processing method, the processing conditions for the next processing step are determined based on the bead shape other than the starting point. Therefore, the occurrence of quality defects can be suppressed. (2) In the laser cladding method of the above form, the measurement step may measure the entire circumference of the bead. This type of processing method allows for improved accuracy in the processing steps because the processing conditions for the next step are determined based on the entire circumference of the measured bead. (3) In the laser cladding method of the above form, the processing step and the measurement step may be performed simultaneously. This type of processing method allows the processing and measurement processes to be performed simultaneously, thus preventing long time intervals between processing steps. Therefore, it is possible to suppress changes in the processing environment caused by long time intervals between processing steps. (4) In the laser cladding method of the above embodiment, the processing conditions may further include the timing of the laser output and the timing of the powder supply. In this processing method, the laser output conditions, powder supply amount, and the timing between laser output and powder supply—all factors whose changes significantly affect bead quality—are set according to correction values. Therefore, the occurrence of quality defects can be suppressed.

[0007] Furthermore, this disclosure can be implemented in various forms, for example, in the form of a method for determining processing conditions for a laser cladding apparatus. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram showing the configuration of a laser cladding processing machine. [Figure 2] This is a flowchart showing an example of a processing procedure. [Figure 3] This is an explanatory diagram of the manufacturing process. [Figure 4] This is an explanatory diagram showing an example of processing conditions. [Figure 5] This figure shows an example of the measurement results for the bead shape. [Modes for carrying out the invention]

[0009] A. First Embodiment: Figure 1 is an explanatory diagram showing the configuration of the laser cladding apparatus 100 in this embodiment. The laser cladding apparatus 100 is a device that performs laser cladding on an object. In this embodiment, the laser cladding apparatus 100 performs laser cladding on the cylinder head 200, which is the object to be processed, and forms a bead on the valve seat portion 220. The laser cladding apparatus 100 has a processing unit 10, a measuring unit 20, and a control unit 30.

[0010] The processing unit 10 includes a laser irradiation unit (not shown), a powder supply unit, and an actuator. The processing unit 10 forms a bead on the object by supplying metal powder from the powder supply unit and irradiating it with laser light from the laser irradiation unit to melt the metal powder. The processing unit 10 forms the bead while moving the laser irradiation unit and the powder supply unit by the actuator. In this embodiment, the processing unit 10 is driven by the actuator to supply metal powder along a substantially circular cladding groove formed in the valve seat portion 220 of the cylinder head 200, and forms a bead by irradiating it with laser light to melt the metal powder. This bead is also called the cladding layer. The processing unit 10 forms the bead under the control of the control unit 30 according to the set processing conditions. In this embodiment, the processing conditions include the laser output intensity and the amount of metal powder supplied. The laser output intensity is the intensity of the laser light. Hereinafter, the amount of metal powder supplied will also simply be called the "powder supply amount".

[0011] The measuring unit 20 measures the bead shape, which is the shape of the bead formed by the processing unit 10. The measuring unit 20 measures the height of the bead relative to the combustion chamber surface 210, for example, using a touch probe 21. The measuring unit 20 is not limited to the touch probe 21; it may also use a non-contact three-dimensional measuring device or the like to measure the bead shape without contact. The touch probe 21 may be arranged coaxially with the processing unit 10 or on a different axis. When the touch probe 21 is arranged coaxially with the processing unit 10, it can follow the movement of the processing unit 10 during processing and measure the bead shape immediately after processing.

[0012] The control unit 30 consists of a computer comprising a central processing unit (CPU), RAM, and ROM. The CPU executes programs pre-installed in the RAM, ROM, and other memory areas of the control unit 30 to realize the functions of the calculation unit 31 and the setting unit 32. It also controls the operation of the machining unit 10 according to the machining conditions set by the setting unit 32. However, some or all of the functions of these units may be realized by hardware circuits.

[0013] The calculation unit 31 calculates correction values for the output intensity of the laser and the powder supply amount according to the difference between the bead shape measured using the measurement unit 20 and the target bead shape. Increasing the powder supply amount and raising the output intensity of the laser enlarges the bead shape. Also, decreasing the powder supply amount and lowering the output intensity of the laser shrinks the bead shape.

[0014] The setting unit 32 sets the processing conditions for the formation of the next bead according to the correction values calculated by the calculation unit 31. Here, "next" bead formation means forming a bead after finishing the formation of the bead whose shape was measured.

[0015] The cylinder head 200 has a combustion chamber surface 210 that is concave. The combustion chamber surface 210 forms a piston (not shown) and a fuel chamber. The combustion chamber surface 210 has a plurality of valve seat portions 220 for the intake valve and the exhaust valve. The valve seat portions 220 serve as seals in the combustion chamber. In FIG. 1, a part of the cylinder head 200 is shown in a cut-away state, and the overall shape of the cylinder head 200 and the shapes of the combustion chamber surface 210 and the valve seat portions 220 are depicted in a simplified manner.

[0016] FIG. 2 is a flowchart showing an example of the processing. This process is repeatedly executed by the laser cladding processing apparatus 100 when there is a valve seat portion 220 to be processed.

[0017] In step S100, the control unit 30 operates the processing unit 10 according to the set processing conditions to perform laser cladding processing on the Nth valve seat portion 220. N is a natural number. This step is also referred to as the "processing step". When step S100 is executed for the first time after starting the processing, N is 1, and the control unit 30 controls the processing unit 10 according to the predetermined processing conditions to perform laser cladding processing.

[0018] Figure 3 is an explanatory diagram of the processing step. As shown in Figure 3, for example, the processing unit 10 forms beads while moving along the trajectory A1 represented by a dashed line by an actuator driven by the control unit 30. More specifically, the processing unit 10 performs one full round of processing clockwise from the start position Ps to the start position Ps again, and further continues the processing clockwise to the end position Pe on the same circumference. In the present embodiment, the portion processed twice from the start position Ps to the end position Pe is also referred to as the overlap portion 221.

[0019] Figure 4 is an explanatory diagram showing an example of processing conditions. Figure 4 is a timing chart showing the relationship between the output intensity of the laser and the powder supply amount. The timing t1 is the timing when the processing step is started, and the timing t4 is the timing when the processing step is completed. That is, the processing unit 10 starts laser irradiation at the start position Ps at the timing t1 and ends laser irradiation at the end position Pe at the timing t4. During the period from the timing t1 to the timing t2 and the period from the timing t3 to the timing t4, the processing unit 10 processes the overlap portion 221.

[0020] As shown in the upper graph of Figure 4, from the timing t1 when the processing of the overlap portion 221 is first performed to the timing t2, the output intensity of the laser is increased from the intensity V0 to the intensity V1. During the period from the timing t2 to the timing t3, the output intensity of the laser is maintained at the intensity V1. From the timing t3 when the processing of the overlap portion 221 is performed again to the timing t4, the output intensity of the laser is decreased from the intensity V1 to the intensity V2. The intensity V2 is greater than the intensity V0. Also, as shown in the lower graph of Figure 4, from the timing t1 when the processing of the overlap portion 221 is first performed to the timing t2, the powder supply amount is increased from the amount Q0 to the amount Q1. During the period from the timing t2 to the timing t3, the powder supply amount is maintained at the amount Q1. From the timing t3 when the processing of the overlap portion 221 is performed again to the timing t4, the powder supply amount is decreased from the amount Q1 to the amount Q2. The amount Q2 is greater than the amount Q0.

[0021] In step S110 (see Figure 2), the measuring unit 20 measures the shape of the bead formed in step S100. This step is also called the "measurement step". In this embodiment, the measuring unit 20 measures the height of the entire circumference of the bead. Steps S100 and S110 may be performed in parallel.

[0022] Figure 5 shows an example of the measurement results for bead shape. In the graph shown in Figure 5, the vertical axis represents height, and the horizontal axis represents the position of the measured bead. Figure 5 shows the results of measuring five bead shapes. In this embodiment, the measuring unit 20 measures the height of the entire circumference of the bead at predetermined distance intervals. That is, the intervals between measurement points are equal. The graph shown in Figure 5 plots the bead height at each measurement point and connects them with straight lines.

[0023] In step S120 (see Figure 2), the calculation unit 31 calculates correction values ​​for the laser output intensity and powder supply amount included in the processing conditions, according to the difference between the bead shape measured in step S110 and the target bead shape. This process is also called the "calculation process". The calculation unit 31 calculates the correction values ​​based, for example, on a map or function that defines the relationship between the difference between the measured bead shape and the target bead shape and the correction value, which has been experimentally determined in advance.

[0024] In step S130, the setting unit 32 sets the processing conditions for the next processing step according to the correction value calculated in step S120. More specifically, the setting unit 32 sets the processing conditions for the N+ith laser cladding process, where i is a natural number. This step is also called the "setting step". In this embodiment, i is 1. Steps S120 and S130 are not limited to this order and may be performed in parallel.

[0025] In step S140, N is incremented by i.

[0026] In this embodiment, for example, if the measured bead shape is smaller than the target bead shape, the setting unit 32 sets the processing conditions to increase the laser output intensity and the powder supply amount according to the correction value calculated by the calculation unit 31.

[0027] After setting the processing conditions in step S140, the control unit 30 returns to the process in step S100. More specifically, the control unit 30 controls the processing unit 10 to perform laser cladding on the Nth valve seat portion 220, which was incremented in step S140, according to the processing conditions set in step S130.

[0028] The inventors discovered that not only the difference between the shape of the overlap portion 221, which is the starting point of bead formation, and the target bead shape, but also the difference between the shape of the parts other than the overlap portion 221 and the target bead shape, affects the quality of the processing. According to the laser cladding method of this embodiment described above, the processing conditions for the next processing step are determined according to the entire circumference of the bead measured, so that even if there is a quality defect in parts other than the overlap portion 221, feedback can be given to the processing conditions. Therefore, the occurrence of quality defects can be suppressed. In addition, the accuracy of the processing step can be further improved.

[0029] Furthermore, when the processing and measurement processes are performed simultaneously, the time interval between processing processes can be shortened. This suppresses changes in the processing environment that would occur if the time interval between processing processes were longer.

[0030] B. Other embodiments: (B1) In the embodiment described above, the measuring unit 20 measures the entire circumference of the bead. However, the measuring unit 20 only needs to measure a portion that includes at least the part other than the starting part of bead formation. In this application, if one or more measurement points measured by the measuring unit 20 are included in a portion, it is treated as if the measuring unit 20 has measured that portion. The portion to be measured is preferably a portion where changes in bead quality are likely to occur depending on the processing conditions, the material of the cylinder head 200, the shape of the valve seat portion 220 to be formed, and a portion where correction values ​​can be easily obtained.

[0031] (B2) In the embodiment described above, the measuring unit 20 measures the bead shape at predetermined fixed distance intervals. That is, the intervals between measurement points are equal. However, the intervals between measurement points may be variable. The number of measurement points can also be arbitrarily determined. The measuring unit 20 may also measure the bead shape so that the measurement points are continuous.

[0032] (B3) In the embodiment described above, the measuring unit 20 measures the height of the bead as the bead shape. However, the measuring unit 20 may also measure the width of the bead as the bead shape. Alternatively, the measuring unit 20 may measure multiple heights in a direction perpendicular to the circumferential direction of the bead. In this case, the measuring unit 20 may determine the bead shape using the average value of the multiple measured heights or a value obtained using other statistical methods.

[0033] (B4) In steps S130 and S140 of the processing in the above-described embodiment, i is 1. However, i may be 2 or greater. A smaller value of i is preferable.

[0034] (B5) In the embodiment described above, the measuring unit 20 may measure the shape of the combustion chamber surface 210 on which the bead is formed before step S100. In this case, the calculation unit 31 determines the target bead shape according to the shape of the combustion chamber surface 210 measured by the measuring unit 20. This improves the accuracy of the processing conditions set by the setting unit 32 and further improves the accuracy of the processing step.

[0035] (B6) In the embodiment described above, the processing conditions set by the setting unit 32 include the laser output intensity and the powder supply amount. However, the processing conditions may further include the timing of the laser output and the timing of the powder supply. In this case, the setting unit 32 sets the laser output condition, powder supply amount, laser output, and powder supply timing, which are elements whose changes have a large impact on the quality of the bead, according to the correction value. As a result, the occurrence of quality defects can be suppressed.

[0036] (B7) In the embodiment described above, the machining unit 10 performs machining clockwise around the circumference from the starting position Ps back to the starting position Ps, and then continues machining clockwise to the ending position Pe on the same circumference. However, the machining unit 10 may also perform machining counterclockwise around the circumference from the starting position Ps back to the starting position Ps, and then continue machining clockwise to the ending position Pe on the same circumference. Alternatively, the machining unit 10 may perform machining counterclockwise around the circumference and then continue machining counterclockwise to the ending position on the same circumference.

[0037] (B8) In the above embodiment, intensity V2 is greater than intensity V0. Also, quantity Q2 is greater than quantity Q0. However, it is not limited to this, and intensity V2 may be less than or equal to intensity V0. Also, quantity Q2 may be less than or equal to quantity Q0.

[0038] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve the problems described above or to achieve some or all of the effects described above. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0039] 10…Processing section, 20…Measurement section, 21…Touch probe, 30…Control unit, 31…Calculation unit, 32…Setting unit, 100…Laser cladding machine, 200…Cylinder head, 210…Combustion chamber surface, 220…Valve seat section, 221…Overlap section

Claims

1. A laser cladding method, A machining process that forms a bead on the valve seat portion of the cylinder head according to the set machining conditions, A measurement step for measuring the bead shape of the bead formed in the processing step, which includes at least a portion other than the starting point of bead formation; A calculation step to calculate correction values ​​for the laser output intensity and powder supply amount included in the processing conditions, according to the difference between the bead shape measured in the measurement step and the target bead shape, The process includes a setting step of setting the processing conditions for the next processing step according to the correction value, The aforementioned processing conditions further include the timing of the laser output and the timing of the powder supply in a laser cladding method.

2. A laser cladding method according to claim 1, The measurement step is a laser cladding method that measures the entire circumference of the bead.

3. A laser cladding method according to claim 1 or claim 2, A laser cladding method in which the processing step and the measurement step are performed simultaneously.

4. A laser cladding processing apparatus, A machining section for forming a bead on the valve seat portion of the cylinder head, A control unit that controls the machining unit according to the set machining conditions, A measuring unit for measuring the bead shape, which includes at least the portion other than the starting point of bead formation, A calculation unit calculates correction values ​​for the laser output intensity and powder supply amount included in the processing conditions, according to the difference between the bead shape measured by the measurement unit and the target bead shape. Includes a setting unit that sets the processing conditions for the next bead formation according to the correction value, The aforementioned processing conditions further include the timing of the laser output and the timing of the powder supply in a laser cladding apparatus.

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