JP5554629B2 - Determination method of welding conditions - Google Patents

Description

  The present invention relates to a method for determining welding conditions.

  As a method for joining resin molded bodies made of thermoplastic resin to each other, in addition to a method of using fastening parts (bolts, screws, clips, etc.) and an adhesive, a hot plate welding method (for example, Patent Document 1). For example, a welding method such as a vibration welding method (see, for example, Patent Literature 2), an ultrasonic welding method (see, for example, Patent Literature 3), or a laser welding method (see, for example, Patent Literature 4) is known.

  The hot plate welding method is a method in which a joint portion between a pair of resin molded bodies is brought into contact with a high-temperature heat mold and melted, and the joint portion is pressed and joined before being cooled and solidified. The vibration welding method and the ultrasonic welding method are methods in which one resin molded body is fixed and the other resin molded body is pressurized and vibration or ultrasonic wave is applied to melt the joint by friction energy and join. is there. In the laser welding method, one of a pair of resin moldings to be joined is composed of a laser light-absorbing material, the other is composed of a laser light-transmitting material, and after laminating them, laser light is emitted from the side of the transparent material. A method in which a laser beam that has passed through a transparent material is heated to melt the material by heating the surface of the absorbent material, and at the same time, the transparent material is also melted by heat transfer to join a pair of resin molded bodies It is.

  The method of welding the pair of resin molded bodies as described above is common in that one or both of the pair of resin molded bodies are melted and joined. Since the strength of the joint varies depending on the conditions for melting and the like (welding conditions), it is required to join a pair of resin molded bodies under suitable welding conditions.

  However, suitable welding conditions for welding the pair of resin molded bodies are influenced by various factors such as the type of resin and heating conditions, and are currently determined empirically.

JP 2002-028977 A JP 2005-319613 A JP 2006-264699 A JP 2001-071384 A

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for determining suitable welding conditions.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it has been found that suitable welding conditions can be determined by considering the heat absorbed when the joint of the resin molded body melts, and the present invention has been completed. More specifically, the present invention provides the following.

前記光吸収性樹脂成形体の熱拡散係数をＤ、単位長さ当たりの前記光の走査時間をｔ、としたときに、前記重ね合わせ部の前記距離ｒの位置において前記光吸収性樹脂成形体側で吸収される吸収エネルギーＥａを下記数式（ＩＩ）から算出する第三工程と、

（数式（ＩＩ）中、ａは係数、Ｄは前記光吸収性樹脂成形体の熱拡散係数、ｔは単位長さ当たりの前記光の走査時間、Ｅ_ａは吸収エネルギー）
前記溶着体において、前記光透過性樹脂成形体と前記光吸収性樹脂成形体との溶着部の溶着強度を測定する第四工程と、前記所定の出力エネルギーを変更して、前記第一工程から前記第四工程を繰り返す工程を一回以上行う第五工程と、前記第一工程から前記第五工程の結果に基づいて、前記吸収エネルギーＥａと前記溶着強度との関係を導出する第六工程と、前記第六工程の結果に基づいて、前記光透過性樹脂成形体と前記光吸収性樹脂成形体とを溶着する際の前記光の照射条件を決定する第七工程と、を有する溶着条件の決定方法。 (1) A light-transmitting resin molded body having light permeability and a light-absorbing resin molded body having light-absorbing property are overlapped to form an overlapped portion, and the light-transmitting resin is formed. A process for producing a welded body of the light-transmitting resin molded body and the light-absorbing resin molded body by irradiating the light from the molded body side toward the overlapping portion with a predetermined scanning speed and a predetermined output energy. In one step, the light transmittance of the light-transmitting resin molding is T, the output energy flux at a distance r from the light irradiation center is a Gaussian function q (r), and the beam diameter of the light is d. , And the second step of calculating the supply energy Es of the light supplied to the position of the distance r in the overlapping portion from the following formula (I):

When the thermal diffusion coefficient of the light-absorbing resin molded body is D and the light scanning time per unit length is t, the light-absorbing resin molded body side at the position of the distance r of the overlapping portion. A third step of calculating the absorbed energy Ea absorbed by the following formula (II):

(In Formula (II), a is a coefficient, D is a thermal diffusion coefficient of the light-absorbing resin molding, t is a scanning time of the light per unit length, and E _a is absorption energy).
In the welded body, a fourth step of measuring the welding strength of the welded portion between the light-transmitting resin molded body and the light-absorbing resin molded body, and changing the predetermined output energy, from the first step A fifth step of performing the step of repeating the fourth step one or more times, and a sixth step of deriving a relationship between the absorbed energy Ea and the welding strength based on the result of the fifth step from the first step; A seventh step of determining the irradiation condition of the light when welding the light-transmitting resin molded body and the light-absorbing resin molded body based on the result of the sixth step. Decision method.

  (2) The sixth step is a step of deriving the relationship based on a graph plotting the absorbed energy Ea and the welding strength, and the relationship has a maximum value of the welding strength. Method for determining welding conditions.

(3) The welding condition determination method according to (1) or (2), wherein the output energy flow velocity is an averaged output energy flux q _a represented by the following formula (III).

（式（ＩＶ）中の、比熱、密度は樹脂成形体の比熱と密度である。）
Ｅ_ａＨの定数倍Ｅ_ａＨ×ａ”、前記光吸収性樹脂成形体を構成する樹脂材料の密度、比熱から上記式（ｃ）を用いて算出される昇温幅から導出される、溶融時の重ね合わせ部における前記樹脂材料の温度が熱分解点になるようなａ”を算出する工程と、導出されたａ’からａ”の範囲で任意の定数を選択工程より求められることを特徴とする、（１）から（３）のいずれかに記載の溶着条件決定方法。 (4) Based on the relationship between the absorbed energy Ea and the welding strength, a step of setting an absorption energy range (ΔE _a (a range from E _aL to E _aH )) in which the welding strength is increased, and a constant multiple of E _aL E _aL × a ′, the density of the resin material constituting the light-absorbing resin molding, and the temperature rise calculated from the specific heat using the following formula (c), the overlapping portion at the time of melting Calculating a ′ such that the temperature of the resin material becomes the melting point;

(The specific heat and density in the formula (IV) are specific heat and density of the resin molded body.)
E _aH constant times E _aH × a ″, the density of the resin material constituting the light-absorbing resin molded body, and the specific heat, derived from the temperature rise calculated using the above formula (c), A step of calculating a ″ such that the temperature of the resin material in the overlapping portion becomes a thermal decomposition point, and an arbitrary constant in the range of derived a ′ to a ″ is obtained by the selection step. (1) The welding condition determination method according to any one of (3).

  (5) The welding condition determination method according to any one of (1) to (4), wherein the coefficient a is 0.18 or more and 0.21 or less.

  (6) The welding condition determination method according to (5), wherein the light-absorbing resin molded body is a molded body formed by molding a polybutylene terephthalate-based resin composition.

  (7) A method of determining a welding condition for fusing at least one resin molded body by heat and welding a pair of resin molded bodies, wherein the resin molded body absorbs at the time of melting by the heat A method of deriving a relationship between energy and the welding strength of the welded body and determining welding conditions based on the relationship between the absorbed energy and the welding strength.

  According to the present invention, it is possible to easily determine suitable welding conditions by considering the heat absorbed when the joint portion of the resin molded body melts.

(A) is a figure which shows the relationship between absorbed energy and welding strength, (b) is a figure which shows the relationship between absorbed energy and welding strength, and shows the case where welding strength has a maximum value. In each condition of the scan speed _{V 1, V 2, V 3} , it is a diagram showing the relationship between the absorbed energy and the welding strength. E _aL, is a diagram showing the relationship between the output energy and the optical scanning speed of light in the E _aH. (A) is the perspective view which showed the welded body typically, (b) is the figure which represented typically the end surface of the light transmissive resin molding before welding and a light absorptive resin molding. It is a figure which shows the measuring method of the welding strength of an Example. (A) is a figure which shows the relationship between the welding intensity | strength of an Example and scanning speed change evaluation, and absorbed energy. (B) is a figure which shows the relationship between the welding intensity | strength and absorbed energy of an Example, scanning speed change evaluation, and thickness change evaluation. It is a figure which shows the relationship between the output energy of the light of an Example, scanning speed change evaluation, and thickness change evaluation, and the scanning speed of light. It is a schematic diagram which shows the welded body of shape change evaluation. It is a figure which shows the relationship between the welding intensity | strength and absorption energy of shape change evaluation. (A) is a figure which shows the relationship between the welding strength of evaluation 2-1, and output energy, (b) is a figure which shows the relationship between the welding strength of evaluation 2-2, and supply energy.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to the following embodiment.

  The method for determining the welding conditions of the present invention takes into account the heat absorbed when the joint of the resin molded body melts. Regardless of the welding method such as hot plate welding method, vibration welding method, ultrasonic welding method, laser welding method, etc., heat is applied to the joint part of the resin molded body, and the joint part absorbs heat and melts. To do. If the welding conditions are determined by paying attention to the heat absorbed by the joint, suitable welding conditions can be easily determined. Hereinafter, the method for determining welding conditions according to the present invention will be described with reference to a welding method using light such as a laser welding method.

The method for determining welding conditions according to this embodiment includes the first to seventh steps.
In the first step, a light-transmitting resin molded body that is transmissive to light and a light-absorbing resin molded body that is light-absorbing are prepared, and light having a predetermined scanning speed and a predetermined output energy is prepared. These resin molded bodies are joined by welding.
In the second step, the supply energy supplied from the light used in the first step to the position at a distance r from the irradiation center of the light is calculated.
In the third step, the absorbed energy absorbed by the light-absorbing resin molding is calculated at a position r from the light irradiation center used in the first step.
In the fourth step, the welding strength of the welded body joined in the first step is measured.
In the fifth step, the output energy of light to be used is changed, and the procedure of repeating the first step to the fourth step is performed at least once.
In the sixth step, the relationship between the absorbed energy and the welding strength is derived based on the results of the fourth and fifth steps.
In the seventh step, welding conditions such as output are determined so that the absorbed energy has a high welding strength.

  According to the present embodiment, the supply energy is calculated in consideration of the light beam diameter, the light transmittance, etc. in the second step, and the thermal diffusion coefficient D of the light-absorbing resin molded body, the light scanning is calculated in the third step. The absorbed energy is calculated in consideration of speed and the like. As a result, the absorbed energy that increases the welding strength does not depend on the shape of the resin molded body to be welded, the scanning speed of light, or the like. Therefore, the welding conditions determined by the method of the present invention can be adopted as suitable conditions even if the shape of the resin molded body to be joined is changed or the light scanning speed is changed. Hereinafter, each step will be described in detail.

[First step]
In the first step, a light-transmitting resin molded body having a light-transmitting property and a light-absorbing resin molded body having a light-absorbing property are overlapped to form an overlapping portion, and the light transmitting The light-transmitting resin molded body and the light-absorbing resin molded body are manufactured by irradiating light from the transparent resin molded body side toward the overlapping portion with a predetermined scanning speed and a predetermined output energy. .

  First, the light transmissive resin molded body will be described. The resin contained in the light-transmitting resin molded body only needs to give the molded body the property of transmitting desired light. For example, polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyethylene, polypropylene, polybutene, 6 nylon, 66 nylon , 11 nylon, 12 nylon, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride and other fluorine resins, polyurethane resin Etc.

  The light-transmitting resin molded body may contain a resin other than the resin having the above light-transmitting properties as long as the effects of the present invention are not impaired. Additives such as inhibitors, stabilizers, plasticizers, lubricants, mold release agents and flame retardants may be added.

  The light-transmitting resin molded body can be molded by a conventionally known method. Examples of conventionally known molding methods include various molding methods such as compression molding, transfer molding, injection molding, extrusion molding, and blow molding.

  The light-transmitting resin molded body molded by the molding method as described above has a joint portion to be bonded to the light-absorbing resin molded body.

  Next, the light absorbing resin molded body will be described. Examples of the resin contained in the light-absorbing resin molding include the same resins as the raw material of the light-transmitting resin molding, and carbon black and dyes are used to reduce the light transmittance. A light-absorbing resin molded body can be obtained by mixing a predetermined colorant such as a pigment or a pigment, or by containing a light-absorbing material such as carbon fiber or carbon black.

  Similarly to the light-transmitting resin molded body, the light-absorbing resin molded body can contain conventionally known resins and additives, and can be molded by a conventionally known molding method. Moreover, the light absorptive resin molded object shape | molded by the conventionally well-known method has a joining plan part for joining with a light transmissive resin molded object.

  Next, production of the welded body will be described. A welded body obtained by joining a light-transmitting resin molded body and a light-absorbing resin molded body by welding can be manufactured using a conventionally known laser welding apparatus, a welding apparatus equipped with a flash lamp, or the like. it can. For example, a welded body is manufactured as follows.

The joining portion of the light-transmitting resin molded body and the joining portion of the light-absorbing resin molded body are overlapped to form an overlapping portion. In the overlapping portion, at least a part of the planned joining portion of the light-transmitting resin molded body is in contact with at least a part of the planned joining portion of the light-absorbing resin molded body.
Light having a circular cross section in the direction perpendicular to the optical axis is irradiated from the light-transmitting resin molded body side toward the overlapping portion at a predetermined scanning speed and a predetermined output energy. Therefore, the irradiation area is circular.
The light transmitted through the light-transmitting resin molded body is absorbed by the light-absorbing resin molded body and converted into heat. This heat melts the vicinity of the overlapping portion of the light-absorbing resin molding. Further, this heat is transmitted to the light transmissive resin molded body through the overlapping portion. The transmitted heat melts the light-transmitting resin molded body.
The bonded portion of the melted light-absorbing resin molded body and the planned bonding portion of the melted light-transmitting resin molded body overlap so that the light-absorbing resin molded body and the light-transmitting resin molded body are bonded by welding. The welded body is manufactured.

[Second step]
In the second step, T is the transmittance for the light used in the first step of the light-transmitting resin molding, and the output energy flux at a distance r from the irradiation center of this light is the Gaussian function q (r), When the light beam diameter is d, the light supply energy Es supplied to the position of the distance r in the overlapping portion is calculated from the following formula (I).

  The supply energy Es is the supply energy of light supplied to the position of the distance r in the overlapping portion. That is, it is obtained by subtracting the energy that disappears when passing through the light-transmitting resin molding from the output energy of the light irradiated in the first step. Hereinafter, the transmittance T, the output energy flux q (r), and the beam diameter d will be described.

  The transmittance T represents the rate at which the light used in the first step actually transmits through the light transmissive resin molded body. Since the actual transmission rate is used, even if light is transmitted through a molded body made of the same material, the transmission rate used varies depending on the length of the transmission path. The formula (I) considering the transmittance T can take into account energy loss due to light passing through the light-transmitting resin molded body. The transmittance is the result of irradiating laser light from one side of a plate-like sample having a predetermined thickness and measuring the transmitted light intensity with a power meter from the opposite side.

（式（ａ）中のＰは光の出力、πは円周率である） The light output energy flux q (r) at a position r from the light irradiation center shows a Gaussian distribution as represented by the following equation (a). This step is a step of considering how much the output energy flow rate is reduced when light passes through the light-transmitting resin molded body. The position of r is not particularly limited, but the value of the supply energy Es varies depending on how the position of r is determined. In the present invention, by considering the transmittance and the beam diameter, a suitable welding condition can be determined no matter how r is set.
Also, focusing on the predetermined unit area of the overlapping portion, the distance between the position of the unit area and the irradiation center of the light changes as the light is scanned, and the energy supplied to the unit area is also However, since the transmittance and the beam diameter are taken into consideration in the present invention, suitable welding conditions can be determined even with such a change.

(P in the formula (a) is the output of light, and π is the circumference)

In the present invention, it is preferable to use an averaged output energy flow rate represented by the following formula (III) as the output energy flux. It is possible to determine suitable welding conditions in consideration of the entire joint with by using the output energy flow rate q _a averaged, more easy way.

  The light irradiation area is circular as described above, and the beam diameter d is the diameter of the cross section in the optical axis direction of the light at the overlapping portion. The wider the beam diameter, the longer the time for light to pass through the unit area. For this reason, in order to obtain | require the energy supplied to a superimposition part, it is necessary to consider a beam diameter. The method for measuring the beam diameter can be obtained, for example, by destroying the welded body from the joint as shown in the examples and actually measuring the weld width from the weld mark.

（数式（ＩＩ）中、ａは係数、Ｄは前記光吸収性樹脂成形体の熱拡散係数、ｔは単位長さ当たりの前記光の走査時間、Ｅ_ａは吸収エネルギー） [Third step]
In the third step, when the thermal diffusion coefficient of the light-absorbing resin molding is D and the light scanning time per unit length is t, the light-absorbing resin molding is performed at the position of the distance r of the overlapping portion. Absorption energy Ea absorbed on the body side is calculated from the following mathematical formula (II).

(In Formula (II), a is a coefficient, D is a thermal diffusion coefficient of the light-absorbing resin molding, t is a scanning time of the light per unit length, and E _a is absorption energy).

  Absorption energy Ea refers to the energy absorbed on the light-absorbing resin molded body side at the position of the distance r of the overlapping portion. This refers to energy obtained by removing energy that is not absorbed by reflection or the like from the supply energy Es supplied to the overlapping portion.

  The heat generated by the light absorbed by the light-absorbing resin molded body diffuses into the light-absorbing resin molded body. Therefore, in order to consider the energy absorbed by the light-absorbing resin molding, it is necessary to consider the diffusion of heat. By considering the diffusion coefficient as represented by the above formula (II), it is possible to appropriately evaluate the energy absorbed by the light-absorbing resin molding, and as a result, it is possible to easily determine suitable welding conditions. Can do. The thermal diffusion coefficient D can be measured by, for example, the hot disk method, but can be obtained by calculation (thermal diffusivity D = thermal conductivity κ / (density ρ × specific heat C)) using characteristic data of the resin material. Can do.

  If the scanning time of light per unit length is short, the time for which light is irradiated to the predetermined unit area in the overlapping portion is shortened, so that the energy absorbed by the light-absorbing resin molding is reduced. On the other hand, when the scanning time of light per unit length is long, the time for irradiating the predetermined unit area in the overlapped portion becomes long, so that the energy absorbed by the light-absorbing resin molded body becomes large. As mentioned above, in order to consider the energy absorbed by the light absorptive resin molding, it is necessary to consider the scanning time of light per unit length.

  The coefficient a is for taking into account the energy that is lost without being absorbed on the light-absorbing resin molding side in the generated heat. As will be described later, in the present invention, an approximate range of the coefficient a can be determined. As will be described later, the value of the coefficient a is not important when determining the welding conditions, and an arbitrary constant can be used when determining the welding conditions.

[Fourth process]
In the fourth step, the welding strength of the welded portion between the light-transmitting resin molded body and the light-absorbing resin molded body is measured in the welded body produced in the first step. The method for measuring the welding strength is not particularly limited, and examples thereof include a method for measuring the welding strength by applying a force in a direction perpendicular to the surface where the light-transmitting resin molded body and the light-absorbing resin molded body overlap. It is done.

[Fifth step]
In the fifth process, the predetermined output energy of the light used in the first process is changed, and the process of repeating the fourth process from the first process is performed once or more. The number of times is not particularly limited, but more suitable welding conditions can be determined by performing the number of times.

[Sixth step]
In the sixth step, the relationship between the absorbed energy Ea and the welding strength is derived based on the results from the first step to the fifth step. The method for deriving the relationship between the absorbed energy and the welding strength is not particularly limited. For example, a method for obtaining the relationship between the absorbed energy and the welding strength on a graph as shown in FIG. And as shown in FIG.1 (b), it is preferable to obtain the graph which has the maximum value of welding strength. More preferable welding conditions can be obtained by determining the welding conditions based on data in the vicinity of the maximum value in a seventh step, which will be described later. The position of the maximum value may be such that the approximate position can be understood as shown in FIG. Note that weld strength when the absorbed energy _{E a1} is _{F 1,} weld strength when _{E a2} is _{F 2,} weld strength when _{E a3} is assumed to be _{F 3.}

Here it will be further described relationship between the absorbed energy E _a and the welding strength obtained in the sixth step of the present invention. The graph of FIG. 1 is data of a predetermined scanning speed condition set in the first step. The scanning speed of the light in the first step as V _1, further in the case of changing the scanning speed (in the case of V _2, V ₃₎ shows the relationship between the absorbed energy E _a and the welding strength in FIG. 2 It was. In the case of the scanning speed _{V 2,} weld strength when the absorbed energy _{E a1} is' _a, weld strength when _{E a2} is _{F 2 'F 1 is,} the welding strength is _{F 3'} when _{E a3} And In the case of the scanning speed V ₃ , the welding strength is F ₁ ″ when the absorbed energy is E _a1 , the welding strength is F ₂ ″ when E _a2 , and the welding strength is F ₃ ″ when E _a3. .

  As shown in FIG. 2, by using the absorption energy as a reference, the position of the absorption energy at which the welding strength has a maximum value becomes very close regardless of the scanning speed of light. It will be further described below that such a result is obtained.

  As described above, the heat generated by light melts the part to be bonded of the light-absorbing resin molded body, and the heat is also transmitted to the part to be bonded of the light-transmitting resin molded body to melt the light-transmitting resin. Then, when the melted portions overlap, the light-transmitting resin molded body and the light-absorbing resin molded body are joined. The welding strength is considered to be determined by the degree of melting, and the degree of melting is considered to be determined by the heat generated by light. Since the heat generated by light is determined by the heat absorbed by the light-absorbing resin molding, if the heat absorbed by the light-absorbing resin molding can be properly evaluated, the welding strength does not depend on the light scanning speed. Is considered to be very close to the position of the absorbed energy showing the maximum value. According to the present invention, the absorbed energy can be appropriately evaluated as described above, and the result shown in FIG. 2 is obtained.

  Note that the deviation of the coefficient a means that all the graphs in FIG. 2 are translated in the + X direction or the −X direction in the same manner. Even if such parallel movement occurs, a relationship is obtained in which the position of the absorbed energy at which the welding strength has a maximum value is very close regardless of the scanning speed of light. Therefore, suitable welding conditions can be determined regardless of the value of a. Details will be described later.

（式（ｂ）中のｌは単位長さ、Ｖは光の走査速度とする。その他は上記の通りである。） [Seventh step]
In the seventh step, light irradiation conditions for welding the light-transmitting resin molded body and the light-absorbing resin molded body are determined based on the result of the sixth step. The light irradiation conditions are a condition of light output energy and a condition of light scanning speed. The relationship between the light output energy and the light scanning speed can be expressed by the following equation (b) from equations (I) and (II). Hereinafter, the procedure for determining the welding conditions will be described in more detail using the results shown in FIG.

(In the formula (b), l is a unit length, V is a light scanning speed, and others are as described above.)

First, the range of absorbed energy having a high welding strength is determined from FIG. Here, the range from E _aL to E _aH (the range of ΔE _a ) is a range with high welding strength.

E _aL is substituted for E _a , V ₁ is substituted for V, and the numbers used in the above-described steps are substituted for r, d, D, l, and T. As a result, the relationship shown by the broken line in FIG. 3 is obtained. When E _aH is substituted for E _a and the relationship between P and V is obtained by the same method as described above, the relationship shown by the solid line in FIG. 3 is obtained. As shown in FIG. 3, the welding strength of the welded body obtained by setting the light output energy and the light scanning speed included in the region between the solid line and the broken line (the hatched portion in FIG. 3) as the irradiation condition is growing.

When the value of a is an arbitrary constant and is different from the actual value of a, for example, when a is estimated to be twice as large, the value of E _a is twice as large as the value assigned to equation (b). Will be. However, since the expression (b) includes 1 / a, even if the arbitrarily determined constant a deviates from the actual value of the coefficient a, it can be corrected with 1 / a. Therefore, the arbitrarily determined constant a deviates from the actual value of a does not cause a problem in determining suitable welding conditions.

When the averaged output energy flow rate q _a represented by the above formula (III) is used as the output energy flow rate, P is introduced into the equation using a constant α represented by q _a / P. . That is, q _a = P × α is substituted into q (r) in the formula (I). When the averaged output energy flow rate is used, equation (b) is transformed into equation (b ′).

（式（ｃ）中の、比熱、密度は樹脂成形体の比熱と密度である。） [Confirmation and Derivation Method of Constant a]
A method for confirming and deriving the constant a will be described with reference to the result of FIG. In the range of larger Delta] E _a weld strength, when joining by welding, to the extent that the light-absorbing resin molded article is melt sufficiently increase the temperature of the resin, and the resin is increasing the temperature of the resin so as not to thermally decompose Conceivable. Here, the absorbed energy necessary for raising the temperature of the resin to a degree sufficient to melt is E _aL or more, and the absorbed energy necessary for applying heat to the resin molded body to such an extent that the resin is not thermally decomposed is E _aH The following is considered. In the case of a predetermined absorbed energy, the extent to which the temperature of the resin increases due to the influence of heat generated by light (temperature increase range) can be obtained from the following equation (c).

(The specific heat and density in the formula (c) are the specific heat and density of the resin molded body.)

_Substituting E _aL and the specific heat and density of the resin constituting the light-absorbing resin molding (hereinafter sometimes simply referred to as “resin”), the temperature rise width is derived from (c). _Let ΔT _aL . Similarly, the temperature rise width in the case of the absorbed energy E _aH can also be derived and is set to ΔT _aH . Assuming that the light-absorbing resin molded body and the light-transmitting resin molded body are welded at room temperature of 23 ° C., when the absorption energy is E _aL , the temperature of the resin material at the time of joining by welding is (23 ° C. + ΔT _aL ). It is considered to be. On the other hand, when the absorbed energy is E _aH , it is considered to be (23 ° C. + ΔT _aH ).

(23 ° C. + ΔT _aL ) must be a temperature at which the light-absorbing resin molding is sufficiently melted. The sufficient melting temperature is considered to be approximately equal to or higher than the melting point of the resin material constituting the light-absorbing resin molding. Further, (23 ° C. + ΔT _aH ) should be approximately a temperature at which the resin material is not thermally decomposed. Therefore, if (23 ° C. + ΔT _aL ) is equal to or higher than the melting point of the resin material and (23 ° C. + ΔT _aH ) is equal to or lower than the thermal decomposition point of the resin material, the coefficient a is appropriate.

If any of the above conditions is not satisfied, an appropriate a can be derived as follows. First, when E _aL × a ′ is taken as the absorbed energy, a ′ that (23 ° C. + ΔT _aL ) becomes a melting point is derived. Next, a ″ where (23 ° C. + ΔT _aH ) becomes the thermal decomposition point when E _aL × a ″ is taken as the absorbed energy is derived. Since the range of a ′ to a ″ is an appropriate range of a. By determining a in this range, an appropriate value of the coefficient a can be obtained. For example, the average of a ′ and a ″ is calculated to calculate the coefficient a. An appropriate value of a can be obtained by the value method. As for the melting point and the thermal decomposition point, an appropriate coefficient a can be determined by using the temperature near the melting point and the temperature near the thermal decomposition point. Note that the value of a is predicted to be about 0.18 to 0.21.

  As described above, the present invention has been described by taking the welding method using light such as the laser welding method as an example. However, when at least one of the resin molded bodies is melted by heat, the welding conditions for welding the pair of resin molded bodies are determined. In, the relationship between the absorbed energy absorbed by the resin molded body during melting by heat and the welding strength of the welded body is derived, and the appropriate welding conditions are determined based on the relationship between the absorbed energy and the welding strength. be able to.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to these Examples.

<Example 1>
In Example 1, suitable welding conditions for producing a pan-shaped (bottomless) welded body as shown in FIG. 4 were determined. FIG. 4A is a perspective view schematically showing the welded body, and FIG. 4B is a diagram schematically showing the end faces of the light-transmitting resin molded body and the light-absorbing resin molded body before welding. It is. The main body is a light-absorbing resin molded body, and the lid is a light-transmitting resin molded body. As shown in FIG. 4B, the main body has a cylindrical shape, and the welded body has a pan shape without a bottom. The light-absorbing resin molded product is a polybutylene terephthalate resin (trade name “Duranex (registered trademark) 711SA”, manufactured by Wintech Polymer Co., Ltd., specific heat 1.01 Jg ⁻¹ K ⁻¹ , density 1.43 g / cm ³ , thermal diffusion. Coefficient D = 0.222 × 10 ⁻⁶ mm ² / s), and the light-transmitting resin molded product is a polybutylene terephthalate resin (trade name “DURANEX (registered trademark) 730LW”, manufactured by Wintech Polymer Co., Ltd., specific heat 1 .14 Jg ⁻¹ K ⁻¹ , density 1.49 g / cm ³ , thermal diffusion coefficient D = 0.200 × 10 ⁻⁶ mm ² / s).

[First step]
A welded body of the light-absorbing resin molded body and the light-transmitting resin molded body shown in FIG. 4 was produced by laser welding. As the laser welding apparatus, a laser welding system manufactured by Leister (trade name “NOVOLAS C”) was used. The laser light conditions were an output of 8 W, a wavelength of 940 nm, and a focal diameter of 0.6 mm. A welded body was manufactured by making one round of the annular overlapping portion under the condition of a scanning speed of 5 mm / sec.

[Second step]
The averaged energy flow rate was calculated using the above formula (III). Since the average energy flux is 4.3 W · mm ⁻² and the output is 8 W, 0.54 times the output is the average energy flux (0.54 corresponds to α described above). Further, the transmittance of the resin material that is the raw material of the light-absorbing resin molded body was 0.27 (when the thickness of the molded body was transmitted through 1.5 mm), and the laser diameter was 1.43 mm (described later). Derived from the welding trace after measuring the welding strength in the four steps (the radial width of the ring-shaped welding trace). The average supply energy Es supplied to the overlapping portion from the formula (I) was 1.7 W · mm ⁻² .

[Third step]
Absorption energy was calculated using the above formula (II). The thermal diffusion coefficient D used for the calculation is an average value 0.211 of the thermal diffusion coefficient of the resin material that is the raw material of the light-absorbing resin molded body and the thermal diffusion coefficient of the resin material that is the raw material of the light-transmitting resin molded body. did. The unit length was 1 mm, and a was 1/2. The reason why a is ½ is that half of the supplied heat is considered to be absorbed by the light-absorbing resin molding, and the other half is absorbed by the light-transmitting resin molding by radiation. E _a was calculated as 0.83 J · mm ⁻³ .

[Fourth process]
The welding strength of the welded body was determined by using a universal testing machine (trade name “Tensilon UTA50KN”) manufactured by Orientec Co., as shown in FIG. The force F was applied to the center of the lid in the direction of the arrow to measure the welding strength. The welding strength was 126N.

[Fifth step]
The above absorption energy and welding strength at six different output energies were measured in the same manner as described above.

[Sixth step]
Seven sets of welding strength and absorbed energy were obtained from the results of the fourth step and the fifth step, and these were plotted on the graph (diamond plot). This graph is shown in FIG. The other curves shown in FIG. 6 are derived by the following evaluation. In this example, the graph was prepared using commercially available spreadsheet software.

[Seventh step]
From the graph of FIG. 6, the range where the absorbed energy is 0.95 to 1.35 J / mm ³ is set as the range where the welding strength is high. Using the above formula (b ′), when the absorbed energy is 0.95 J / mm ³ and 1.35 J / mm ³ respectively, P (light output energy), V (light scanning speed) and The relationship was derived. These relationships are represented by formulas (V) and (VI). Expression when absorbed energy of 0.95J / mm ³ (V), the absorption energy by the formula (VI) in the case of 1.35J / mm ³ in the graph shown in FIG. Welding with high welding strength can be achieved by setting welding conditions in the area between the straight line representing the formula (V) (straight line connecting the white squares) and the straight line representing the formula (VI) (straight line connecting the black squares). The body is obtained.

<Derivation of coefficient a>
First, the temperature increase width is derived using the above formula (c). Here, for the specific heat and density, the average of the polybutylene terephthalate resin contained in the light-absorbing resin molding and the polybutylene terephthalate resin contained in the light-transmitting resin molding was used.

When the absorbed energy was 0.95 J / mm ³ , the temperature rise range was 605 ° C., and at 1.35 J / mm ^{3 the} temperature rise range was 860 ° C. The coefficient a for which the temperature rise width when the absorbed energy is 0.95 J / mm ³ is 230 ° C. (melting point of polybutylene terephthalate) −the temperature of the resin at the measurement is 0.18. Moreover, the coefficient a that the temperature increase width at 1.35 J / mm ³ is 375 ° C. (pyrolysis point of polybutylene terephthalate resin) −the temperature of the resin at the measurement is 0.21. It was confirmed that the coefficient a should be determined in the range of 0.18 to 0.21.

<Evaluation 1>
The versatility of the welding conditions determined as in the above example was evaluated. Specifically, evaluation (scanning speed change evaluation) in which the scanning speed is changed, evaluation (thickness change evaluation) in which the thickness of the light-transmitting resin molded body on the lid side is changed, light-transmitting resin molded body, and light-transmitting resin Evaluation (shape change evaluation) was performed by changing the shape of the molded body.

[Scanning speed change evaluation]
The relationship between the welding strength and the absorption energy was derived in the same manner as in the above example except that the scanning speed condition was changed to 10 mm / s and seven sets of absorption energy and welding strength were derived in the fifth step. (Curve connecting the squares in FIG. 6 (dots inside)). Further, the relationship between the welding strength and the absorption energy was changed in the same manner as in the above example except that the scanning speed condition was changed to 20 mm / s and seven sets of absorption energy and welding strength were derived in the fifth step. Derived (curve connecting white triangles in FIG. 6). Regardless of the scanning speed condition, the absorbed energy at which the welding strength is maximized is almost the same value. Therefore, the welding conditions determined by the method of the embodiment can be employed even when the scanning speed is different.

[Thickness change evaluation]
The relationship between the welding strength and the absorbed energy was derived in the same manner as in the example except that the thickness of the light transmissive resin molding was changed from 1.5 mm to 1.0 mm and the scanning speed condition was changed to 20 mm / s. Further, the scanning speed conditions were changed to 30 mm / s and 50 mm / s, and the relationship between the absorbed energy and the welding strength was derived. The results are shown on FIG. 6B (see Table 1 for the relationship between plots and results). Here, when the thickness was 1.0 mm, the transmittance T was 0.41, the laser diameter was 0.77, and α was 1.86.

The relationship between the welding strength and the absorbed energy was derived in the same manner as in the example except that the thickness of the light transmissive resin molding was changed from 1.5 mm to 2.0 mm, and the scanning speed condition was 7.5 mm / s. By changing to 10 mm / s, the relationship between absorbed energy and welding strength was derived. The result is shown in FIG. (See Table 1 for the relationship between plots and conditions). Here, when the thickness was 2.0 mm, the transmittance T was 0.19, the laser diameter was 2.43, and α was 0.19.
In addition, in FIG.6 (b) which showed this evaluation result, the result of Fig.6 (a) was also shown together (refer Table 1 for the relationship between a plot and conditions).

  As confirmed from the result of the “scanning speed change evaluation”, the relationship between the absorbed energy and the welding strength can be expressed by substantially the same curve even if the scanning speed is different. Therefore, for each thickness, the relationship between the welding strength and the absorbed energy is shown by a curve in FIG. Regardless of the thickness, the absorbed energy at which the welding strength is maximized is substantially the same value. Therefore, even if the thickness conditions are different, the welding conditions determined by the method of the embodiment can be employed. In FIG. 7, the relationship between P (light output energy) and V (light scanning speed) is derived for each thickness, and a graph is shown (when the lid thickness is 1 mmt, white). When the circle, black circle, and lid thickness are 2 mmt, they are represented by white triangles and black triangles, and are represented by straight lines connecting each point).

[Shape change evaluation]
The shape of the light-transmitting resin molded body and the shape of the light-absorbing resin molded body are changed to a plate shape as shown in FIG. 8 and are overlapped as shown in FIG. 8 to the 5.5 mm portion shown in FIG. Laser welding was performed. Laser irradiation conditions were the same as in the example except that the focal diameter was changed to 1.2 mm.
In addition, the fourth step was changed to tensile shear strength evaluation under conditions of a distance between chucks of 50 mm and a test speed of 5 mm / min, and the relationship between welding strength and absorbed energy was derived in the same manner as in the examples. The derivation results were graphed in the same manner as in the above examples and evaluations. The graph is shown in FIG. 9, and the relationship between each plot and the conditions is shown in Table 2.

As confirmed from the results of FIG. 9, it was confirmed that even when the shape was changed, the range of absorbed energy 0.95 to 1.35 J / mm ³ could be said to be a range with high welding strength. Therefore, even if the shape of the light-transmitting resin molded body is changed to a different shape, the welding conditions determined by the method of the embodiment can be employed.

<Evaluation 2>
In Evaluation 2, instead of deriving the relationship between the welding strength and the absorbed energy, the evaluation for deriving the relationship between the welding strength and the output energy (Evaluation 2-1), the welding strength and the supply energy represented by the following formula (VII) An evaluation (Evaluation 2-2) for deriving the relationship was performed.

[Evaluation 2-1]
The result of the example was changed to the relationship between the welding strength and the output energy. The graph after the change is shown in FIG. 10A (relationship between conditions and plots is shown in Table 3).

[Evaluation 2-2]
The result of the example was changed to the relationship between the welding strength and the supplied energy. The graph after the change is shown in FIG. 10B (the relationship between the conditions and the plot is the same as in Table 3).

  As is apparent from the results of FIG. 10, unless the absorbed energy derived as in the present invention is taken into consideration, the position of the maximum value of the welding strength in the horizontal axis direction shifts, and a suitable welding as in the present invention. Conditions cannot be easily determined.

Claims (6)

A light-transmitting resin molded body having light permeability and a light-absorbing resin molded body having light-absorbing property are overlapped to form an overlapping portion, and from the light-transmitting resin molded body side A first step of manufacturing a welded body of the light-transmitting resin molded body and the light-absorbing resin molded body by irradiating the overlapping portion with the light at a predetermined scanning speed and a predetermined output energy; ,
When the light transmittance of the light-transmitting resin molding is T, the output energy flux at a distance r from the light irradiation center is a Gaussian function q (r), and the light beam diameter is d. And a second step of calculating a supply energy Es of the light supplied to the position of the distance r in the overlapping portion from the following formula (I):

When the thermal diffusion coefficient of the light-absorbing resin molded body is D and the light scanning time per unit length is t, the light-absorbing resin molded body side at the position of the distance r of the overlapping portion. A third step of calculating the absorbed energy Ea absorbed by the following formula (II):

(In Formula (II), a is a coefficient, D is a thermal diffusion coefficient of the light-absorbing resin molding, t is a scanning time of the light per unit length, and E _a is absorption energy).

In the welded body, a fourth step of measuring the welding strength of the welded portion between the light-transmitting resin molded body and the light-absorbing resin molded body,
A fifth step of changing the predetermined output energy and performing the step of repeating the fourth step from the first step one or more times;
A sixth step of deriving a relationship between the absorbed energy Ea and the welding strength based on the result of the fifth step from the first step;
Based on the result of the sixth step, the seventh step of determining the irradiation condition of the light when welding the light-transmitting resin molded body and the light-absorbing resin molded body is determined. Method.   6. The sixth step is a step of deriving the relationship based on a graph plotting the absorbed energy Ea and the welding strength, and the relationship has a maximum value of the welding strength. Method. The welding condition determination method according to claim 1 or 2, wherein the output energy flow velocity is an averaged output energy flux q _a expressed by the following mathematical formula (III).

Based on the relationship between the absorbed energy Ea and the welding strength, a step of setting an absorption energy range (ΔE _a (a range from E _aL to E _aH )) in which the welding strength increases;
E _aL constant times E _aL × a ′, derived from the temperature rise calculated from the density and specific heat of the resin material constituting the light-absorbing resin molded body using the following formula (c), at the time of melting Calculating a ′ such that the temperature of the resin material at the overlapping portion becomes a melting point;

(The specific heat and density in the formula (IV) are specific heat and density of the resin molded body.)

E _aH constant times E _aH × a ″, the density of the resin material constituting the light-absorbing resin molded body, and the specific heat, derived from the temperature rise calculated using the above formula (c), Calculating a ″ such that the temperature of the resin material in the overlapping portion becomes a thermal decomposition point;
The welding condition determination method according to any one of claims 1 to 3, wherein an arbitrary constant within a range of derived a 'to a "is obtained by the selection step.   The welding condition determination method according to claim 1, wherein the coefficient a is 0.18 or more and 0.21 or less.   The welding condition determination method according to claim 5, wherein the light-absorbing resin molded body is a molded body formed by molding a polybutylene terephthalate-based resin composition.

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