Patent Description:
A typical laser welding apparatus joins two resin members arranged one upon the other by laser welding. There are various types of laser welding apparatuses that perform laser welding while applying pressure with a jig, such as a clamp, to press the surfaces of the two resin members against each other so that the resin members can be welded sufficiently.

<CIT> describes an example of a laser welding apparatus that clamps two resin members by a clamp claw and detects the reactive force acting on the clamp claw. Then, the clamping force applied by the clamp claw is adjusted in accordance with the detected reactive force so that the two resin members are appropriately pressed against each other. Subsequently, the laser welding apparatus performs laser welding in a state in which the adjusted clamping force is applied to the two resin members by the clamp claw.

<CIT> discloses a technique that presses two resin members against each other with a clamp mechanism and detects changes in the temperature of the contact surfaces where the resin members contact each other when irradiating the contact surfaces with a laser beam to adjust the clamping force of the clamp mechanism.

<CIT> describes a laser welding apparatus that gradually increases the clamping force of a jig applied to press two resin members against each other and detects a reactive force acting on the jig to obtain a change in the gradient of the detected reactive force relative to displacement of the jig. When the angle of the gradient changes in a direction in which the reactive force increases greatly, the laser welding apparatus stops gradually increasing the clamping force applied to the two resin members by the jig. Subsequently, the laser welding apparatus laser-welds the two resin members in a state in which the clamping force applied to the two resin members by the jig is the clamping force that was obtained when stopping the gradual increase.

One of two resin members that are laser-welded is formed of a laser beam-transmissive resin that transmits laser beams. The other one of the two resin members is formed of a laser beam-absorbing resin that absorbs laser beams. The laser beam-absorbing resin member is thermally expanded when absorbing a laser beam during laser welding. Further, laser welding has various effects on the two resin members, which are arranged one upon the other, in the vicinity of the contact surfaces, such as hardening. Thus, it is preferred that an appropriate clamping force be applied to the two resin members in accordance with the state of the two resin members during laser welding. Also, it is preferred that the laser beam be appropriately emitted in accordance with the state of the two resin members during laser welding.

The application of excessive clamping force to the two resin members during laser welding may result in, for example, the formation of excessive burrs or the formation of cracks in the welded resin members caused by residual stress. The application of clamping force that is too small to the two resin members during laser welding may result in insufficient pressing of the resin members against each other. When the resin members are pressed against each other insufficiently, fine gaps will form between the contact surfaces of the two resin members, which are arranged one upon the other. When laser welding is performed in this state, the fine gaps will hinder the transfer of heat from the laser beam-absorbing resin member to the laser beam-transmissive resin member. As a result, the laser beam-absorbing resin member, which continues absorbing the laser beam without sufficiently transferring heat, will be carbonized. Further, the laser beam-transmissive resin member may not be melted adequately due to the insufficient transfer of heat from the laser beam-absorbing resin member.

<CIT> describes a method and apparatus for welding, wherein for joining two faces of thermoplastics the covered face is scanned and incremently heated by a laser beam. The laser welding apparatus described in <CIT> and <CIT> applies clamping force to two resin members to press the two resin members against each other prior to performing laser welding. However, in <CIT> and <CIT>, the clamping force applied to the two resin members is not adjusted during laser welding. Thus, depending on the adjustment of the clamping force applied to the two resin members prior to laser welding, the formation of excessive burrs or the formation of cracks may occur in the welded resin members.

As described in <CIT>, when the temperature at the contact surfaces of the two resin members is detected and the clamping force applied to the two resin members is adjusted in accordance with the detected temperature during laser welding, adjustment of the clamping force will be difficult if the detected temperature change is subtle. Moreover, when the clamping force is controlled in accordance with the temperature change at the contact surfaces of the two resin members in real-time, the control for adjusting the clamping force may be delayed with respect to the speed of the temperature change. Thus, the clamping force applied to the two resin members may not appropriately be in accordance with the state of the resin members during laser welding.

An objective of the present disclosure is to provide a laser welding apparatus and a laser processing device that limit formation of burrs and cracks in the resin members. In further detail, the objective of the present disclosure is to provide a laser welding apparatus that avoids insufficient pressing of the resin members so that carbonizing or inadequate melting of the resin members does not occur.

In one general aspect, a laser welding apparatus joins a first resin member, which is formed of a laser beam-transmissive resin and includes a first contact surface, and a second resin member, which is formed of a laser beam-absorbing resin and includes a second contact surface, by melting the first contact surface and the second contact surface with a laser beam in a state in which the first resin member and the second resin member are arranged one upon another with the first contact surface contacting the second contact surface. The laser welding apparatus includes a clamping unit, a laser emitter, a laser controller, a displacement sensor, and a control unit. The clamping unit abuts at least one of the first resin member or the second resin member, which are arranged one upon the other, to apply clamping force to the at least one of the first resin member or the second resin member. The laser emitter emits a laser beam transmitted through the first resin member. The laser controller controls a laser output of the laser beam emitted from the laser emitter. The displacement sensor measures displacement of at least one of the first contact surface or the second contact surface in a direction in which the first resin member and the second resin member are arranged one upon the other. The control unit continuously or intermittently obtains a displacement amount of the at least one of the first contact surface or the second contact surface from the displacement sensor and controls the clamping unit to increase or decrease the clamping force in accordance with the obtained displacement amount of the at least one of the first contact surface or the second contact surface.

With this configuration, the clamping force applied to the first resin member and the second resin member is increased or decreased in accordance with the displacement amount of the at least one of the first contact surface or the second contact surface displaced in the stacking direction in which the first resin member and the second resin member are arranged one upon the other. The first contact surface and the second contact surface are displaced in the stacking direction in correspondence with the state of the first resin member and the state of the second resin member during laser welding. In other words, the displacement of the first contact surface and the second contact surface in the stacking direction is changed in correspondence with the state of the first resin member and the second resin member during laser welding. The clamping force applied to the first resin member and the second resin member is increased or decreased in accordance with the displacement amount of the at least one of the first contact surface or the second contact surface. Thus, an appropriate clamping force can be applied to the first resin member and the second resin member in accordance with the state of the first resin member and the second resin member during laser welding. As a result, the formation of burrs and cracks is limited in the first resin member and the second resin member. This also limits carbonizing or inadequate melting of the resin members that would be caused by insufficient pressing of the resin members against each other.

In the laser welding apparatus, it is it preferred that when the control unit detects a change in the displacement of the at least one of the first contact surface or the second contact surface resulting from thermal expansion of the second resin member based on the displacement amount of the at least one of the first contact surface or the second contact surface obtained from the displacement sensor, the control unit controls the clamping unit to increase the clamping force over a predetermined period. Further, it is preferred that when the control unit subsequently detects reversal of a direction of the displacement of the at least one of the first contact surface or the second contact surface based on the displacement amount of the at least one of the first contact surface or the second contact surface obtained from the displacement sensor, the control unit controls the clamping unit to decrease the clamping force in a stepped manner.

With this configuration, the clamping force applied to the first resin member and the second resin member is increased over the predetermined period from when a change in the displacement of the contact surface resulting from the thermal expansion of the second resin member is detected. This restricts separation of the first resin member from the second contact surface caused by the thermal expansion of the second resin member. In this manner, the first contact surface and the second contact surface remain sufficiently pressed against each other even while the second resin member is thermally expanded.

Further, when reversal of the displacement direction of the contact surface is detected, the clamping force applied to the first resin member and the second resin member is decreased in a stepped manner. The displacement direction of the contact surface measured by the displacement sensor is reversed when the second resin member starts softening. Accordingly, the clamping force applied to the first resin member and the second resin member is decreased in a stepped manner as the second resin member starts to soften. This decreases the amount of softened resin pushed out from the periphery of the first contact surface and the second contact surface.

In the laser welding apparatus, it is preferred that when the displacement direction measured by the displacement sensor is reversed, the laser controller controls the laser emitter to increase the laser output in a stepped manner over a preset period.

With this configuration, the laser output of the laser beam emitted to the second contact surface can be increased in a stepped manner from when the second resin member starts softening. This allows the laser beam to be emitted in accordance with the state of the second resin member.

In the laser welding apparatus, it is preferred that when the preset period elapses, the laser controller control the laser emitter to gradually decrease the laser output.

With this configuration, the laser output is gradually decreased to gradually cool the first contact surface and the second contact surface that are in a state melted and joined with each other. Also, the first contact surface and the second contact surface are gradually cooled when the clamping force applied to the first resin member and the second resin member is being decreased in a stepped manner. This reduces the residual stress that occurs in the first resin member and the second resin member subsequent to cooling. As a result, the formation of cracks is further limited in the first resin member and the second resin member.

In the laser welding apparatus, it is preferred that the displacement sensor be a contact type displacement sensor.

With this configuration, the contact type displacement sensor directly detects displacement of the contact surface so that the displacement can be detected more accurately than, for example, an optical displacement sensor. In addition, the contact type displacement sensor can detect a displacement of the contact surface at a relatively lower cost than an optical displacement sensor that has the same measurement accuracy.

It is preferred that the laser welding apparatus further include a reactive force measuring sensor. The reactive force measuring sensor measures a reactive force added to the clamping unit by the at least one of the first resin member or the second resin member, which the clamping unit is abut against. Further, it is preferred that the control unit obtain the reactive force measured by the reactive force measuring sensor and control the clamping unit to increase or decrease the clamping force in accordance with the displacement amount of the at least one of the first contact surface or second contact surface obtained from the displacement sensor and the reactive force obtained from the reactive force measuring sensor.

With this configuration, the clamping force applied to the first resin member and the second resin member is increased or decreased in accordance with the reactive force added to the clamping unit by the at least one of the first resin member or the second resin member in addition to the displacement amount of the contact surface. The reactive force added to the clamping unit by the at least one of the first resin member or the second resin member, which is in contact with the clamping unit, changes in accordance with the state of the first resin member and the second resin member during laser welding. Therefore, clamping force can be applied in a further suitable manner to the first resin member and the second resin member during laser welding in accordance with the state of the first resin member and the second resin member by further increasing or decreasing the clamping force applied to the first resin member and the second resin member in accordance with the reactive force. As a result, the formation of burrs and cracks is further limited in the first resin member and the second resin member.

In one general aspect, a laser processing device is used to laser-weld and join a first resin member, which is formed of a laser beam-transmissive resin and includes a first contact surface, and a second resin member, which is formed of a laser beam-absorbing resin and includes a second contact surface, by melting the first contact surface and the second contact surface with a laser beam in a state in which the first resin member and the second resin member are arranged one upon another with the first contact surface contacting the second contact surface. The laser processing device includes a laser emitter, a laser controller, and an input unit. The laser emitter emits a laser beam transmitted through the first resin member. The laser controller controls a laser output of the laser beam emitted from the laser emitter. The input unit receives a measurement signal corresponding to a displacement amount of at least one of the first contact surface or the second contact surface measured by a displacement sensor that measures displacement of the at least one of the first contact surface or the second contact surface in a direction in which the first resin member and the second resin member are arranged one upon the other. The laser controller controls the laser emitter to change the laser output in a stepped manner based on the measurement signal provided to the input unit.

With this configuration, the laser output of the laser beam emitted to the second contact surface can be changed in accordance with the displacement amount of the at least one of the first contact surface or the second contact surface displaced in the stacking direction in which the first resin member and the second resin member are arranged one upon the other. The first contact surface and the second contact surface are displaced in the stacking direction in correspondence with the state of the first resin member and the state of the second resin member during laser welding. In other words, the displacement of the first contact surface and the second contact surface in the stacking direction is changed in correspondence with the state of the first resin member and the second resin member during laser welding. The laser output of the laser beam emitted to the second contact surface is changed in a stepped manner in accordance with the displacement amount of the at least one of the first contact surface or the second contact surface. Thus, the first resin member and the second resin member are irradiated with the laser beam that is suitable for the state of the first resin member and the second resin member during the laser welding. This limits the formation of excessive burrs and the occurrence of cracking in the first resin member and the second resin member.

In the laser processing device, it is preferred that after the laser controller detects a change in the displacement of the at least one of the first contact surface or the second contact surface resulting from thermal expansion of the second resin member from the measurement signal provided to the input unit, when the laser controller detects reversal of a direction of the displacement of the at least one of the first contact surface or the second surface from the measurement signal, the laser controller controls the laser emitter to increase the laser output in a stepped manner over a preset period.

With this configuration, the laser output of the laser beam emitted to the second contact surface can be increased in a stepped manner from when the second resin member starts softening. This allows the laser beam to be emitted in accordance with the state of the second resin member. As a result, the first resin member and the second resin member are joined with improved quality.

In the laser processing device, it is preferred that the input unit be further provided with a clamp control signal corresponding to a clamping force applied by a clamping unit to at least one of the first resin member or the second resin member, which are arranged one upon the other, the clamping unit being abut against the one of the first resin member and the second resin member. Further, it is preferred that the laser controller control the laser emitter to increase the laser output in a stepped manner over a preset period from either one of when a change in the displacement of the at least one of the first contact surface or the second contact surface resulting from thermal expansion of the second resin member is detected based on the measurement signal provided to the input unit and when an increase in the clamping force is detected based on the clamp control signal provided to the input unit.

With this configuration, the laser output is increased in a stepped manner from when a change in the displacement of the contact surface resulting from the thermal expansion of the second resin member is detected so that the laser output of the laser beam emitted to the second contact surface can be increased in a stepped manner from when the second contact surface starts thermal expansion. Further, in a case where the clamping force is increased in accordance with the changes in the displacement of the contact surface resulting from the thermal expansion of the second resin member, the laser output is increased in a stepped manner from when an increase in the clamping force is detected based on the clamp control signal so that the laser output of the laser beam emitted to the second contact surface can be increased in a stepped manner from when the second resin member starts thermal expansion. This allows for the laser beam to be emitted in a manner suitable for the state of the second resin member. As a result, the first resin member and the second resin member are joined with improved quality.

In the laser processing device, it is preferred that when the preset period elapses, the laser controller control the laser emitter to gradually decrease the laser output.

With this configuration, the laser output is gradually decreased to gradually cool the first contact surface and the second contact surface that are in a state melted and joined with each other. This reduces the residual stress that occurs in the first resin member and the second resin member subsequent to cooling. As a result, the formation of cracks is further limited in the first resin member and the second resin member.

In the laser processing device, it is preferred that the input unit be further provided with a clamp control signal corresponding to a clamping force applied by a clamping unit to at least one of the first resin member or the second resin member, which are arranged one upon the other, the clamping unit being abut against the one of the first resin member and the second resin member. Further, it is preferred that the laser controller control the laser emitter to gradually decrease the laser output when detecting that the clamping force is being decreased in a stepped manner from the clamp control signal provided to the input unit and that a change amount of the displacement of the at least one of the first contact surface or the second contact surface is constant over a predetermined period based on the measurement signal provided to the input unit.

With this configuration, the laser output is gradually decreased to gradually cool the first contact surface and the second contact surface that are in a state melted and joined with each other. Also, the first contact surface and the second contact surface are gradually cooled when the clamping force applied to the first resin member and the second resin member is decreased in a stepped manner. This reduces the residual stress that occurs in the first resin member and the second resin member subsequent to cooling. As a result, the formation of cracks is further limited in the first resin member and the second resin member.

The laser welding apparatus and the laser welding apparatus of the present disclosure limit formation of burrs and cracks in the resin members. Further, the laser welding apparatus of the present disclosure limits carbonizing or inadequate melting of the resin members that would be caused by insufficient pressing of the resin members against each other.

An embodiment of a laser welding apparatus will now be described with reference to the drawings.

A laser welding apparatus <NUM> in the present embodiment shown in <FIG> is for laser welding a first resin member <NUM> and a second resin member <NUM> in a state in which the first resin member <NUM> and the second resin member <NUM> are arranged one upon the other. The laser welding apparatus <NUM> includes a clamping unit <NUM>, a laser emitter <NUM>, a laser controller <NUM>, a displacement sensor <NUM>, and a control unit <NUM>. The laser welding apparatus <NUM> in the present embodiment includes a laser processing device <NUM>. The laser processing device <NUM> includes the laser emitter <NUM> and the laser controller <NUM>. The laser emitter <NUM> and the laser controller <NUM> do not have to be included in the laser welding apparatus <NUM> as part of the laser processing device <NUM>.

The clamping unit <NUM> contacts and applies clamping force to at least one of the first resin member <NUM> or the second resin member <NUM>, which are arranged one upon the other. The clamping unit <NUM> includes, for example, a movable stage <NUM> and a top panel <NUM> arranged opposing the movable stage <NUM>. Further, the clamping unit <NUM> includes a pressure adjustment unit <NUM> and a pressure controller <NUM>. The pressure adjustment unit <NUM> applies pressure to the movable stage <NUM>. The pressure controller <NUM> controls the pressure adjustment unit <NUM>.

The movable stage <NUM> includes a setting surface on which the first resin member <NUM> and the second resin member <NUM> are set. The setting surface <NUM> is flat.

The first resin member <NUM> is formed of a laser beam-transmissive resin that transmits laser beams and includes a first contact surface <NUM>. Further, the first resin member <NUM> includes a first abutment surface <NUM> at the side opposite to the first contact surface <NUM>. The second resin member <NUM> is formed of a laser beam-absorbing resin that absorbs laser beams and includes a second contact surface <NUM>. Further, the second resin member <NUM> includes a second abutment surface <NUM> at the side opposite to the second contact surface <NUM>. The first resin member <NUM> and the second resin member <NUM> are arranged one upon the other on the setting surface <NUM> in a state in which the first contact surface <NUM> is in contact with the second contact surface <NUM>. Also, the first resin member <NUM> and the second resin member <NUM> are arranged one upon the other on the setting surface <NUM> in a state in which the second abutment surface <NUM> abuts the setting surface <NUM>.

In the present embodiment, a stacking direction X1 in which the first resin member <NUM> and the second resin member <NUM> are arranged one upon the other is orthogonal to the second contact surface <NUM>. In a state in which the first resin member <NUM> and the second resin member <NUM> are set on the setting surface <NUM>, the stacking direction X1 is orthogonal to the setting surface <NUM>.

The top panel <NUM> and the movable stage <NUM> sandwich the first resin member <NUM> and the second resin member <NUM>. The top panel <NUM> is arranged opposing the setting surface <NUM>. The top panel <NUM> may be formed of a material that does not transmit laser beams or a transparent body, such as glass, that transmits laser beams. When the top panel <NUM> is formed of a material that does not transmit laser beams, the top panel <NUM> includes a through hole for passage of a laser beam. The through hole may be a physical space through which a laser beam passes. Alternatively, a member that allows for transmission of a laser beam, such as an optical glass, may be arranged in the through hole. In other words, the through hole may be an optical window. In this manner, when the top panel <NUM> is formed of a material that does not transmit laser beams, the top panel <NUM> includes a portion that allows for optical transmission of a laser beam regardless of whether there is a physical space.

In the present embodiment, the top panel <NUM> is formed of a metal material. Further, the top panel <NUM> includes a through hole <NUM> from which the first resin member <NUM> is exposed. In the present embodiment, the through hole <NUM> includes a physical space through which a laser beam passes. The top panel <NUM> can be arranged to contact the first abutment surface <NUM> of the first resin member <NUM> set on the setting surface <NUM>.

The pressure adjustment unit <NUM> is a mechanism that applies pressure to the movable stage <NUM> in a direction orthogonal to the setting surface <NUM> in order to apply clamping force to the second resin member <NUM> and press the first contact surface <NUM> and the second contact surface <NUM> against each other. The pressure adjustment unit <NUM> applies pressure to the movable stage <NUM> toward the top panel <NUM> using, for example, one or more of a motor, air pressure, hydraulic pressure, or spring pressure. In the present embodiment, the pressure adjustment unit <NUM> uses, for example, a servomotor.

The pressure controller <NUM> controls the pressure adjustment unit <NUM> to adjust the clamping force applied to the movable stage <NUM> by the pressure adjustment unit <NUM>. Further, the pressure controller <NUM> controls the pressure adjustment unit <NUM> to adjust a moving speed of the movable stage <NUM>.

The laser emitter <NUM> emits a laser beam Lw that is transmitted through the first resin member <NUM>. The laser controller <NUM> controls a laser output of the laser beam Lw emitted from the laser emitter <NUM>.

The laser controller <NUM> includes a laser oscillator (not shown) that emits the laser beam Lw. The laser oscillator is a laser light source, such as a YAG laser, a CO<NUM> laser, or a fiber laser. The laser beam Lw emitted from the laser oscillator is supplied through an optical fiber and the like to the laser emitter <NUM>. The laser controller <NUM> may include an input unit <NUM> that receives at least one of a measurement signal S1 or a clamp control signal S2, which are electric signals that will be described later. The laser oscillator may be included in the laser emitter <NUM> instead of the laser controller <NUM>.

The laser emitter <NUM> emits the laser beam Lw supplied from the laser controller <NUM> toward the first resin member <NUM> and the second resin member <NUM>, which are set on the setting surface <NUM>. The laser beam Lw emitted from the laser emitter <NUM> and transmitted through the first resin member <NUM> irradiates the second contact surface <NUM> of the second resin member <NUM>. In the present embodiment, the laser beam Lw emitted from the laser emitter <NUM> passes through the through hole <NUM> and is transmitted through the first resin member <NUM>.

The laser controller <NUM> controls the laser oscillator to control when to emit the laser beam Lw. Further, the laser controller <NUM> controls the laser emitter <NUM> to control scanning of the second resin member <NUM> with the laser beam Lw. Specifically, the laser controller <NUM> controls the laser emitter <NUM> to control, for example, a scanning passage and a scanning speed of the laser beam Lw. Also, the laser controller <NUM> controls the laser emitter <NUM> to adjust a focal spot diameter of the laser beam Lw on the second contact surface <NUM>.

The displacement sensor <NUM> measures a displacement of at least one of the first contact surface <NUM> or the second contact surface <NUM> in the stacking direction X1. The displacement sensor <NUM> in the present embodiment measures, for example, the displacement of the second contact surface <NUM> in the stacking direction X1. Specifically, the displacement sensor <NUM> in the present embodiment measures the displacement of the setting surface <NUM> in a direction orthogonal to the setting surface <NUM> to measure the displacement of the second contact surface <NUM> of the second resin member <NUM> on the setting surface <NUM>.

The displacement sensor <NUM> can be of a contact type displacement sensor or a non-contact type displacement sensor such as of a laser focus type, an ultrasonic type, an optical type, and an eddy-current type. A known displacement sensor can be used as the displacement sensor <NUM>. The displacement sensor <NUM> in the present embodiment is, for example, a contact type displacement sensor. The displacement sensor <NUM> includes, for example, a measurement head <NUM> and a displacement sensor controller <NUM>.

The measurement head <NUM> includes a contact element <NUM>. In the present embodiment, the measurement head <NUM> is arranged so that the contact element <NUM> contacts the setting surface <NUM>. The contact element <NUM> is moved in a direction orthogonal to the setting surface <NUM> as the setting surface <NUM> moves in a direction orthogonal to the setting surface <NUM>. In this manner, the measurement head <NUM> measures the displacement of the setting surface <NUM> in a direction orthogonal to the setting surface <NUM>.

The displacement sensor controller <NUM> calculates a displacement amount of the contact element <NUM>. Specifically, the displacement sensor controller <NUM> calculates a displacement amount of the contact element <NUM> to obtain the displacement amount of the setting surface <NUM> in a direction orthogonal to the setting surface <NUM>. In the present embodiment, the displacement sensor controller <NUM> outputs the calculated displacement amount of the contact element <NUM>, or the displacement amount of the second contact surface <NUM> in the stacking direction X1.

The control unit <NUM> is, for example, a programmable logic controller (PLC) or a personal computer. The control unit <NUM> may include a memory, a timer, and the like.

The control unit <NUM> obtains the displacement amount of the second contact surface <NUM> from the displacement sensor <NUM> continuously or intermittently and controls the clamping unit <NUM> in accordance with the obtained displacement amount of the second contact surface <NUM> to increase or decrease the clamping force applied to the first resin member <NUM> and the second resin member <NUM>. The control unit <NUM> calculates the clamping force applied to the second resin member <NUM> based on the obtained displacement amount of the second contact surface <NUM>. The control unit <NUM> outputs the calculated clamping force to the clamping unit <NUM>. In an example, the control unit <NUM> outputs data that indicates the calculated clamping force to the clamping unit <NUM>. Further, the control unit <NUM> may control the clamping unit <NUM> to control the moving speed of the movable stage <NUM>.

The control unit <NUM> outputs the measurement signal S1 that corresponds to the displacement amount obtained from the displacement sensor <NUM> to the input unit <NUM>. In the present embodiment, the measurement signal S1 is an electric signal corresponding to the displacement amount of the second contact surface <NUM> measured by the displacement sensor <NUM>. The measurement signal S1 is provided to the input unit <NUM> continuously or intermittently.

The control unit <NUM> may output the clamp control signal S2 that corresponds to the clamping force applied to at least one of the first resin member <NUM> or the second resin member <NUM> by the clamping unit <NUM> to the input unit <NUM>. In the present embodiment, the clamp control signal S2 is an electric signal corresponding to the clamping force applied to the second resin member <NUM> by the clamping unit <NUM>. The clamp control signal S2 may be provided to the input unit <NUM> continuously or intermittently. Alternatively, the clamp control signal S2 may be provided to the input unit <NUM> when the clamping force applied to the second resin member <NUM> by the clamping unit <NUM> is changed.

The operation of the laser welding apparatus <NUM> will now be described.

<FIG> shows the relationship of time and the hardness of a work when the laser welding apparatus <NUM> performs laser welding in an upper row (a). In the present embodiment, the hardness of a work corresponds to the hardness of the welded portions of the first resin member <NUM> and the second resin member <NUM>. <FIG> shows the relationship of time and the intensity of the laser beam Lw emitted from the laser emitter <NUM> when the laser welding apparatus <NUM> performs laser welding in a middle row (b). <FIG> shows the relationship of time and the clamping force applied by the clamping unit <NUM> when the laser welding apparatus <NUM> performs laser welding in a bottom row (c). <FIG> shows the stages of changes in the state of the first resin member <NUM> and the second resin member <NUM>, namely, laser absorption/heat generation, expansion, softening, melting, cooling, and welding completion. The time for each stage is exemplary and may differ from the actual time.

<FIG> is a graph showing the relationship of time and the displacement amount measured by the displacement sensor <NUM> during laser welding. The solid line in <FIG> shows the relationship of time and the displacement amount measured by the displacement sensor <NUM> when the clamping force applied to the second resin member <NUM> for laser welding is increased or decreased in accordance with the displacement amount measured by the displacement sensor <NUM>. Further, the double-dashed line shows the relationship of time and the displacement amount measured by a displacement sensor when a constant clamping force is applied to the resin member for laser welding.

As shown in <FIG>, the first resin member <NUM> and the second resin member <NUM> are first set on the setting surface <NUM> of the movable stage <NUM> in a state in which the first resin member <NUM> and the second resin member <NUM> are arranged one upon the other and the first contact surface <NUM> is in contact with the second contact surface <NUM>. In this case, the first resin member <NUM> and the second resin member <NUM> are arranged on the setting surface <NUM> so that the second abutment surface <NUM> of the second resin member <NUM> is in contact with the setting surface <NUM>. In a state in which the first resin member <NUM> and the second resin member <NUM> are arranged on the setting surface <NUM>, the stacking direction X1 substantially coincides with a direction orthogonal to the setting surface <NUM>.

The first resin member <NUM> and the second resin member <NUM> are sandwiched by the movable stage <NUM> and the top panel <NUM>, which is in contact with the first abutment surface <NUM> of the first resin member <NUM>. In a state in which the top panel <NUM> is in contact with the first resin member <NUM>, the top panel <NUM> will not be displaced in a direction orthogonal to the setting surface <NUM>, or the stacking direction X1.

The control unit <NUM> controls the clamping unit <NUM> to apply a clamping force to the second resin member <NUM>. In this manner, a clamping force is applied to the second resin member <NUM> from the clamping unit <NUM> to press the first resin member <NUM> and the second resin member <NUM> against each other in the stacking direction X1. The displacement sensor <NUM> measures the displacement of the setting surface <NUM> in a direction orthogonal to the setting surface <NUM>. The control unit <NUM> obtains the displacement amount of the second contact surface <NUM> from the displacement sensor <NUM> continuously or intermittently. Further, the control unit <NUM> continuously or intermittently provides the input unit <NUM> with the measurement signal S1 corresponding to the displacement amount of the second contact surface <NUM> obtained from the displacement sensor <NUM>. Also, the control unit <NUM> may provide the input unit <NUM> with the clamp control signal S2. In the present embodiment, the control unit <NUM> provides the input unit <NUM> with the clamp control signal S2.

A target displacement amount Td is preset for the displacement amount measured by the displacement sensor <NUM> so that the first resin member <NUM> and the second resin member <NUM> will have the desired thickness in the stacking direction X1 subsequent to the laser welding. In other words, the laser welding is performed on the first resin member <NUM> and the second resin member <NUM> so that the displacement amount measured by the displacement sensor <NUM> becomes the target displacement amount Td when completing the joining of the first resin member <NUM> and the second resin member <NUM>. For example, in the present embodiment, the target displacement amount Td is set to <NUM>.

After completing the pressure application for pressing the first resin member <NUM> and the second resin member <NUM> against each other in the stacking direction X1, the laser controller <NUM> controls the laser emitter <NUM> to start emission of the laser beam Lw. In the present embodiment, the displacement sensor <NUM> uses the position of the second contact surface <NUM> in the stacking direction X1 when emission of the laser beam Lw is started as a reference position and measures the displacement amount of the second contact surface <NUM> from the reference position. That is, in the present embodiment, the displacement sensor <NUM> uses a reference position of the position of the setting surface <NUM> in the stacking direction X1 when emission of the laser beam Lw is started and measures the displacement amount of the setting surface <NUM> from the reference position. Thus, in the present embodiment, the displacement amount measured by the displacement sensor <NUM> is zero when the second contact surface <NUM> is at the reference position, or when the setting surface <NUM> is at the reference position. The laser beam Lw emitted from the laser emitter <NUM> and transmitted through the first resin member <NUM> irradiates the second contact surface <NUM> of the second resin member <NUM>. The second resin member <NUM> absorbs the laser beam Lw and starts generating heat.

As shown in <FIG>, at the stage in which the second resin member <NUM> absorbs the laser beam Lw and generates heat, the hardness of the first resin member <NUM> and the hardness of the second resin member <NUM> remain constant and do not change. Thus, there is no change in the displacement amount measured by the displacement sensor <NUM>. Also, at this stage, the intensity of the laser beam Lw is set to be constant. Furthermore, at this stage, the clamping force applied by the clamping unit <NUM> remains constant.

As time T1 elapses from when emission of the laser beam Lw was started, the second resin member <NUM> starts thermal expansion. At the stage in which the second resin member <NUM> thermally expands, the hardness of the first resin member <NUM> and the hardness of the second resin member <NUM> remain the same and do not change from the stage in which the second resin member <NUM> absorbed the laser beam Lw and generated heat. Also, at the stage in which the second resin member <NUM> thermally expands, the intensity of the laser beam Lw is set to be constant and equal to that at the stage in which the second resin member <NUM> absorbed the laser beam Lw and generated heat.

When the second resin member <NUM> is thermally expanded without the hardness of the first resin member <NUM> and the hardness of the second resin member <NUM> being changed, the movable stage <NUM> is pushed back by the volume change of the second resin member <NUM> in a direction opposite to the force-applying direction of the clamping unit <NUM>. This changes the displacement of the setting surface <NUM> measured by the displacement sensor <NUM>. In regards to the direction in which the setting surface <NUM> is displaced, displacement in the direction that is the same as the direction in which the clamping force is applied by the clamping unit <NUM> will be referred to as displacement in the positive direction, and displacement in the direction opposite to the direction in which the clamping force is applied will be referred to as displacement in the negative direction. Specifically, displacement in the positive direction is displacement in a direction that decreases the thickness of the first resin member <NUM> and the thickness of second resin member <NUM> in the stacking direction X1, and displacement in the negative direction is displacement in a direction that increases the thickness of the first resin member <NUM> and the second resin member <NUM> in the stacking direction X1.

When the setting surface <NUM> is displaced toward the negative side by thermal expansion of the second resin member <NUM>, the displacement sensor <NUM> measures the direction and amount of the displacement. The control unit <NUM> detects changes in the displacement of the second contact surface <NUM> resulting from the thermal expansion of the second resin member <NUM> based on the displacement amount obtained from the displacement sensor <NUM>. Specifically, the control unit <NUM> detects changes in the displacement of the second contact surface <NUM> resulting from the thermal expansion of the second resin member <NUM> when displacement of the setting surface <NUM> in the negative direction is detected based on the displacement amount obtained from the displacement sensor <NUM>. The control unit <NUM> determines that the setting surface <NUM> is displaced in the negative direction, for example, when detecting that the gradient of the displacement amount relative to time is directed in the negative direction. Alternatively, the control unit <NUM> may determine that the setting surface <NUM> is displaced in the negative direction when detecting that the displacement amount of the setting surface <NUM> is changed from zero toward the negative side, instead of when detecting a change in the gradient of the displacement amount relative to time.

In this case, the laser controller <NUM> detects the changes in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> from the measurement signal S1 provided to the input unit <NUM> from the control unit <NUM>. The laser controller <NUM> detects the changes in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> from the measurement signal S1 in the same manner as the control unit <NUM>.

Subsequently, when detecting the changes in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM>, the control unit <NUM> controls the clamping unit <NUM> to increase the clamping force over a predetermined period. In the present embodiment, the clamping force applied to the second resin member <NUM> is increased by one step over period t1 from when the changes in the displacement of the second resin member <NUM> resulting from thermal expansion of the second contact surface <NUM> is detected. This minimizes separation of the second resin member <NUM> from the setting surface <NUM> when the second resin member <NUM> thermally expands. This also minimizes separation of the first resin member <NUM> from the second contact surface <NUM> when the second resin member <NUM> thermally expands. In this manner, the first contact surface <NUM> and the second contact surface <NUM> are pressed against each other in a satisfactory manner even when the second resin member <NUM> thermally expands.

Period t1 may be freely set taking into consideration the physical properties of the first resin member <NUM> and the second resin member <NUM>, the intensity of the laser beam Lw, the clamping force applied by the clamping unit <NUM>, and the like. For example, in the present embodiment, period t1 corresponds to the period from when the control unit <NUM> detects the changes in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> to when the control unit <NUM> detects reversal of the displacement direction of the second contact surface <NUM>. In other words, in the present embodiment, period t1 corresponds to the period from when the second resin member <NUM> starts expanding to when the second resin member <NUM> starts softening.

The second resin member <NUM> starts softening when time T2 elapses from when emission of the laser beam Lw was started. When the second resin member <NUM> starts softening, a portion of the second resin member <NUM> near the second contact surface <NUM> gradually softens as time elapses. The softened portion of the second resin member <NUM> near the second contact surface <NUM> is compressed by the clamping force applied by the clamping unit <NUM>. This displaces the second contact surface <NUM> toward the setting surface <NUM>. Thus, the setting surface <NUM> is displaced in the same direction as the force-applying direction of the clamping unit <NUM>. Accordingly, the displacement amount of the setting surface <NUM> measured by the displacement sensor <NUM> is shifted in the positive direction.

When the setting surface <NUM> is displaced in the positive direction by the softening of the second resin member <NUM>, the displacement sensor <NUM> measures the direction and amount of the displacement. The control unit <NUM> detects that the displacement direction of the second contact surface <NUM> is reversed based on the displacement amount obtained from the displacement sensor <NUM>. Specifically, the control unit <NUM> detects that the displacement direction of the second contact surface <NUM> is reversed when detecting that the displacement direction of the setting surface <NUM> is reversed from the negative direction to the positive direction based on the displacement amount obtained from the displacement sensor <NUM>. The control unit <NUM> determines that the displacement direction of the setting surface <NUM> is reversed from the negative direction to the positive direction, for example, when detecting that the gradient of the displacement amount relative to time is shifted from the negative direction to the positive direction. There is no limitation to how the control unit <NUM> determines reversal of the displacement direction of the setting surface <NUM> from the negative direction to the positive direction. The control unit <NUM> may determine that the displacement direction of the setting surface <NUM> is reversed from the negative direction to the positive direction, for example, when detecting that the gradient of the displacement amount relative to time is shifted from the negative direction to zero. Alternatively, the control unit <NUM> may determine that the displacement direction of the setting surface <NUM> is reversed when detecting that the setting surface <NUM> that was being displaced in the negative direction starts being displaced in the positive direction, instead of detecting a change in the gradient of the displacement amount relative to time. In other words, the control unit <NUM> may determine that the displacement direction of the setting surface <NUM> is reversed from the negative direction to the positive direction when detecting that the displacement amount of the setting surface <NUM> stopped increasing in the negative direction and started increasing in the positive direction.

Subsequently, when detecting reversal of the displacement direction of the second contact surface <NUM>, the control unit <NUM> controls the clamping unit <NUM> to decrease the clamping force in a stepped manner. In the present embodiment, the clamping force applied to the second contact surface <NUM> is decreased by one step over period t2 from when the reversal of the displacement direction of the second contact surface <NUM> is detected. This decreases the amount of softened resin pushed out from the periphery of the first contact surface <NUM> and the second contact surface <NUM>.

Period t2 may be freely set taking into consideration the physical properties of the first resin member <NUM> and the second resin member <NUM>, the intensity of the laser beam Lw, the clamping force applied by the clamping unit <NUM>, and the like. For example, in the present embodiment, period t2 is set to the period from when the control unit <NUM> detects the reversal of the displacement direction of the second contact surface <NUM>, that is, when the second resin member <NUM> starts softening, to approximately when the second resin member <NUM> starts melting.

Then, when period t2 elapses, the control unit <NUM> controls the clamping unit <NUM> to further decrease the clamping force applied to the second contact surface <NUM> by one step over period t3. When period t3 elapses, the control unit <NUM> controls the clamping unit <NUM> to further decrease the clamping force applied to the second contact surface <NUM> by one step over period t4. In this manner, after detecting the reversal of the displacement direction of the second contact surface <NUM>, the control unit <NUM> controls the clamping unit <NUM> to decrease the clamping force in a stepped manner until the first resin member <NUM> and the second resin member <NUM> are released (unclamped) from the top panel <NUM> and the movable stage <NUM>.

Period t3 and period t4 may be freely set taking into consideration the physical properties of the first resin member <NUM> and the second resin member <NUM>, the intensity of the laser beam Lw, the clamping force applied by the clamping unit <NUM>, and the like. For example, in the present embodiment, period t3 is set to the period from approximately when the second resin member <NUM> starts melting to approximately when the first resin member <NUM> and the second resin member <NUM> start cooling. Further, in the present embodiment, period t4 is set to, for example, the period from approximately when the first resin member <NUM> and the second resin member <NUM> start cooling to approximately when the cooling of the first resin member <NUM> and the second resin member <NUM> ends.

When the displacement direction measured by the displacement sensor <NUM> is reversed, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period. For example, after a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> is detected based on the measurement signal S1 and when reversal of the displacement direction of the second contact surface <NUM> is detected based on the measurement signal S1, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period. In the present embodiment, as described above, the laser controller <NUM> detects that the displacement direction of the second contact surface <NUM> is reversed from the measurement signal S1 at time T2. When detecting the reversal of the displacement direction of the second contact surface <NUM> from the measurement signal S1 at time T2, the laser controller <NUM> first increases the laser output by one step. In the present embodiment, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output by one step over period t12 from when the reversal of displacement direction of the second contact surface <NUM> is detected. Then, the laser controller <NUM> controls the laser emitter <NUM> to further increase the laser output by one step over period t13 from when period t12 elapses.

The laser output is increased or decreased by increasing or decreasing the energy intensity per unit area at the portion irradiated by the laser beam Lw. The laser output is, for example, increased or decreased by adjusting at least one of the intensity of the laser beam Lw (i.e., laser power), the number of times the laser beam Lw is emitted (i.e., on-off of laser beam Lw), or the scanning speed of the laser beam Lw.

Period t12 and period t13 may be freely set taking into consideration the physical properties of the first resin member <NUM> and the second resin member <NUM>, the intensity of the laser beam Lw, the clamping force applied by the clamping unit <NUM>, and the like. For example, in the present embodiment, period t12 is set as the period from when the laser controller <NUM> detects the reversal of displacement direction of the second contact surface <NUM>, that is, when the second resin member <NUM> starts softening, to approximately when the second resin member <NUM> starts melting. Further, in the present embodiment, period t13 is set as, for example, the period from approximately when the second resin member <NUM> starts melting to approximately when the first resin member <NUM> and the second resin member <NUM> start cooling. In the present embodiment, period t12 and period t13, or the period from time T2 to time T4, corresponds to a set period.

As time T3 elapses from when emission of the laser beam Lw was started, the second resin member <NUM> starts melting. Also, the heat transferred from the second resin member <NUM> to the first resin member <NUM> starts melting the first resin member <NUM>. A portion of the first resin member <NUM> near the first contact surface <NUM> and a portion of the second resin member <NUM> near the second contact surface <NUM> further soften as time elapses. This joins the first contact surface <NUM> and the second contact surface <NUM>. Further, the portion of the first resin member <NUM> near the first contact surface <NUM> and the portion of the second resin member <NUM> near the second contact surface <NUM> are compressed by the clamping force applied by the clamping unit <NUM>. This further displaces the second contact surface <NUM> toward the setting surface <NUM>, which, in turn, further displaces the setting surface <NUM> in the same direction as the force-applying direction of the clamping unit <NUM>. In this manner, the displacement amount of the setting surface <NUM> measured by the displacement sensor <NUM> is further shifted in the positive direction.

As described above, when detecting the reversal of the displacement direction of the second contact surface <NUM>, the control unit <NUM> controls the clamping unit <NUM> to decrease the clamping force in a stepped manner. Thus, when the portion of the first resin member <NUM> near the first contact surface <NUM> and the portion of the second resin member <NUM> near the second contact surface <NUM> are in a molten state, the clamping force applied to the second resin member <NUM> is decreased in a stepped manner. The molten resin is softer than resin that is in a softened state. Therefore, when the portion of the first resin member <NUM> near the first contact surface <NUM> and the portion of the second resin member <NUM> near the second contact surface <NUM> are molten, it is preferred that the clamping force applied to the second resin member <NUM> be further decreased from that when the portion of the second resin member <NUM> near the second contact surface <NUM> is softened. In the present embodiment, when the portion of the first resin member <NUM> near the first contact surface <NUM> and the portion of the second resin member <NUM> near the second contact surface <NUM> are molten, the clamping force applied to the second resin member <NUM> is further decreased by one step from the step when the portion of the second resin member <NUM> near the second contact surface <NUM> is softened. This decreases the amount of molten resin pushed out from the periphery of the first contact surface <NUM> and the second contact surface <NUM>. Thus, the formation of burrs is limited.

The laser controller <NUM> controls the laser emitter <NUM> to decrease the laser output or stop emission of the laser beam Lw when period t13 elapses (that is, when above-described preset period elapses). Accordingly, the first resin member <NUM> and the second resin member <NUM> start cooling. In the present embodiment, when period t13 elapses, time T4 has elapsed from when emission of the laser beam Lw was started. In the present embodiment, the laser controller <NUM> controls the laser emitter <NUM> to gradually decrease the laser output when period t13 elapses. Then, the laser controller <NUM> controls the laser emitter <NUM> to stop emission of the laser beam Lw when the laser output becomes equal to a preset output. In the present embodiment, when the emission of the laser beam Lw is stopped, time T5 has elapsed from when emission of the laser beam Lw was started. When the emission of the laser beam Lw is stopped, the joining of the first resin member <NUM> and the second resin member <NUM> is completed.

When the emission of the laser beam Lw is stopped, the control unit <NUM> controls the clamping unit <NUM> to release the first resin member <NUM> and the second resin member <NUM> from the top panel <NUM> and the movable stage <NUM>. Consequently, the first resin member <NUM> and the second resin member <NUM> of which the first contact surface <NUM> and second contact surface <NUM> are joined, are removed from the setting surface <NUM>.

Laser welding of the resin members performed by the laser welding apparatus <NUM> will now be compared with conventional laser welding of the resin members performed under a constant clamping force. In <FIG>, the solid lines show the relationship of time and the displacement amount of the contact surfaces of the resin members when the laser welding is performed by the laser welding apparatus <NUM>. Further, in <FIG>, the double-dashed lines show the relationship of time and the displacement amount of the contact surfaces of the resin members when the laser welding of the resin members is performed under a constant clamping force. The displacement amount of the contact surfaces of the resin members corresponds to the displacement amount of the contact surface of one of the two resin members in a direction in which the laser-welded resin members are arranged one upon the other.

As shown in <FIG>, for example, when the target displacement amount Td is reached during the same processing period, the quality of the joined resin members is better when undergoing laser welding performed by the laser welding apparatus <NUM> than when undergoing conventional laser welding under a constant clamping force. This is because the laser welding performed by the laser welding apparatus <NUM> does not apply excessive force to the first resin member <NUM> and the second resin member <NUM> from when the second resin member <NUM> starts softening until when the joining of the first resin member <NUM> and the second resin member <NUM> is completed. Therefore, with the laser welding performed by the laser welding apparatus <NUM>, the displacement amount of the second contact surface <NUM> reaches the target displacement amount Td without applying excessive force to the first resin member <NUM> and the second resin member <NUM>. When performing laser welding with the laser welding apparatus <NUM>, a longer time is required from when the resin member starts softening until when the joining of the resin members is completed compared to the conventional laser welding performed under a constant clamping force. However, the laser welding performed by the laser welding apparatus <NUM> reduces the displacement amount of the second contact surface <NUM> while the second resin member <NUM> is thermally expanding. Accordingly, the displacement amount of the second contact surface <NUM> is limited from when the displacement direction of the second contact surface <NUM> is reversed until when the displacement amount of the second contact surface <NUM> reaches the target displacement amount Td. This allows the first resin member <NUM> and the second resin member <NUM> to be joined during the same processing time as the conventional laser welding performed under a constant clamping force.

Further, for example, as shown in <FIG>, the laser welding performed by the laser welding apparatus <NUM> can shorten the processing time from that of the conventional laser welding performed under a constant clamping force. This is because the laser welding performed by the laser welding apparatus <NUM> limits the displacement amount of the second contact surface <NUM> while the second resin member <NUM> is thermally expanding. Accordingly, the displacement amount of the second contact surface <NUM> is limited from when the displacement direction of the second contact surface <NUM> is reversed to when the displacement amount of the second contact surface <NUM> reaches the target displacement amount Td. This shortens the period from when the displacement direction of the second contact surface <NUM> is reversed to when the displacement amount of the second contact surface <NUM> reaches the target displacement amount Td. As a result, the laser welding performed by the laser welding apparatus <NUM> shortens the processing time and reduces the manufacturing cost related with the laser welding of the first resin member <NUM> and the second resin member <NUM>.

Moreover, for example, as shown in <FIG>, the laser welding performed by the laser welding apparatus <NUM> limits excessive pressing of the resin members compared to the conventional laser welding performed under a constant clamping force. With the conventional laser welding performed under a constant clamping force, the resin members may be excessively pressed from when the resin member starts softening until when the joining of the resin members is completed. In such a case, the displacement amount of the contact surface of the resin members will be greater than the target displacement amount Td. Accordingly, burrs may be formed excessively and cracks may be formed in the resin member by increased residual stress. In contrast, the laser welding performed by the laser welding apparatus <NUM> increases or decreases the clamping force applied to the first resin member <NUM> and the second resin member <NUM> in accordance with the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. Therefore, the first resin member <NUM> and the second resin member <NUM> are not excessively pressed. As a result, the displacement amount of the second contact surface <NUM> easily reaches the target displacement amount Td.

The present embodiment has the following effects and advantages.

In the present embodiment, the clamping unit <NUM> contacts the second resin member <NUM> and applies clamping force to the second resin member <NUM>. Further, in the present embodiment, the displacement sensor <NUM> measures displacement of the second contact surface <NUM> in the stacking direction X1.

With this configuration, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is increased or decreased in accordance with the displacement amount of the second contact surface <NUM> in the stacking direction X1. The second contact surface <NUM> is displaced in the stacking direction X1 in correspondence with the state of the first resin member <NUM> and the state of the second resin member <NUM> during laser welding. In other words, the displacement of the second contact surface <NUM> in the stacking direction X1 is changed in correspondence with the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. The clamping force applied to the first resin member <NUM> and the second resin member <NUM> is increased or decreased in accordance with the displacement amount of the second contact surface <NUM>. Thus, an appropriate clamping force can be applied to the first resin member <NUM> and the second resin member <NUM> in accordance with the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. As a result, the formation of burrs and cracks is limited in the first resin member <NUM> and the second resin member <NUM>. This also limits carbonizing or inadequate melting of the second resin member <NUM> that would be caused by insufficient pressing of the first resin member <NUM> and the second resin member <NUM> against each other.

In the present embodiment, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> during laser welding does not become excessive. This limits the formation of burrs and cracks in the welded first resin member <NUM> and second resin member <NUM> that would be caused by the residual stress. Further, in the present embodiment, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> during laser welding does not become insufficient. This avoids insufficient pressing of the first resin member <NUM> and the second resin member <NUM> against each other. Therefore, the laser welding can be performed while restricting the formation of fine gaps between the first contact surface <NUM> and the second contact surface <NUM> and facilitating the transfer of heat from the second resin member <NUM> to the first resin member <NUM>. As a result, carbonizing of the second resin member <NUM> and inadequate melting of the first resin member <NUM> are avoided.

(<NUM>) When a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> is detected based on the displacement amount of the second contact surface <NUM> obtained from the displacement sensor <NUM>, the control unit <NUM> controls the clamping unit <NUM> to increase the clamping force over a predetermined period. Subsequently, when reversal of the displacement direction of the second contact surface <NUM> is detected based on the displacement amount of the second contact surface <NUM> obtained from the displacement sensor <NUM>, the control unit <NUM> controls the clamping unit <NUM> to decrease the clamping force in a stepped manner.

With this configuration, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is increased over a predetermined period from when a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> is detected. This restricts separation of the second resin member <NUM> from the setting surface <NUM> caused by the thermal expansion of the second resin member <NUM>. This also restricts separation of the first resin member <NUM> from the second contact surface <NUM> caused by the thermal expansion of the second resin member <NUM>. In this manner, the first contact surface <NUM> and the second contact surface <NUM> remain sufficiently pressed against each other even while the second resin member <NUM> is thermally expanded.

Further, when reversal of the displacement direction of the second contact surface <NUM> is detected, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is decreased in a stepped manner. The displacement direction of the second contact surface <NUM> measured by the displacement sensor <NUM> is reversed when the second resin member <NUM> starts softening. Thus, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is decreased in a stepped manner as the second resin member <NUM> starts to soften. This decreases the amount of softened resin pushed out from the periphery of the first contact surface <NUM> and the second contact surface <NUM> and reduces burrs.

(<NUM>) When the displacement direction measured by the displacement sensor <NUM> is reversed, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period.

With this configuration, the output of the laser beam Lw emitted to the second contact surface <NUM> can be increased in a stepped manner from when the second resin member <NUM> starts softening. This allows the laser beam Lw to be emitted in accordance with the state of the second resin member <NUM>.

(<NUM>) When the preset period elapses, the laser controller <NUM> controls the laser emitter <NUM> to gradually decrease the laser output.

With this configuration, the laser output is gradually decreased to gradually cool the first contact surface <NUM> and the second contact surface <NUM> that are in a state melted and joined with each other. Also, the first contact surface <NUM> and the second contact surface <NUM> are gradually cooled when the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is being decreased in a stepped manner. This reduces the residual stress that occurs in the first resin member <NUM> and the second resin member <NUM> subsequent to cooling. As a result, the formation of cracks is further limited in the first resin member <NUM> and the second resin member <NUM>.

(<NUM>) The displacement sensor <NUM> is a contact type displacement sensor.

With this configuration, the contact type displacement sensor <NUM> directly measures displacement of the setting surface <NUM>. Accordingly, the measurement result of the displacement sensor <NUM> is subtly affected by microscopic scratches on the setting surface <NUM> or microscopic matter on the setting surface <NUM>. Therefore, the contact type displacement sensor can detect displacement of the setting surface <NUM> (second contact surface <NUM> in present embodiment) more accurately than, for example, an optical displacement sensor. In addition, the contact type displacement sensor can detect displacement of the setting surface <NUM> at a relatively lower cost than an optical displacement sensor that has the same measurement accuracy.

(<NUM>) In a state in which the first resin member <NUM> and the second resin member <NUM> are arranged one upon the other so that the first contact surface <NUM> contacts the second contact surface <NUM>, the laser processing device <NUM> is used to laser-weld and join the first contact surface <NUM> and the second contact surface <NUM> with the laser beam Lw. The laser processing device <NUM> includes the laser emitter <NUM> that emits the laser beam Lw, which is transmitted through the first resin member <NUM>. The laser processing device <NUM> includes the laser controller <NUM> that controls the laser output of the laser beam Lw emitted from the laser emitter <NUM>. The laser processing device <NUM> includes the input unit <NUM> that receives the measurement signal S1 corresponding to the displacement amount of the second contact surface <NUM> measured by the displacement sensor <NUM>, which measures displacement of the second contact surface <NUM> in the stacking direction X1 of the first resin member <NUM> and the second resin member <NUM>. The laser controller <NUM> controls the laser emitter <NUM> to change the laser output in a stepped manner based on the measurement signal S1 provided to the input unit <NUM>.

With this configuration, the laser output of the laser beam Lw emitted to the second contact surface <NUM> is changed in a stepped manner in accordance with the displacement amount of the second contact surface <NUM> displaced in the stacking direction X1 of the first resin member <NUM> and the second resin member <NUM>. The second contact surface <NUM> is displaced in the stacking direction X1 in correspondence with the state of the first resin member <NUM> and the state of the second resin member <NUM> during laser welding. In other words, the displacement of the second contact surface <NUM> in the stacking direction X1 is changed in correspondence with the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. The laser output of the laser beam Lw emitted to the second contact surface <NUM> is changed in a stepped manner in accordance with the displacement amount of the second contact surface <NUM>. Thus, the first resin member <NUM> and the second resin member <NUM> are irradiated with the laser beam Lw that is suitable for the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. This limits the formation of excessive burrs and the occurrence of cracking in the first resin member <NUM> and the second resin member <NUM>.

(<NUM>) Subsequent to a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> that is detected based on the measurement signal S1 provided to the input unit <NUM>, when reversal of displacement direction of the second contact surface <NUM> is detected based on the measurement signal S1, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period.

With this configuration, the output of the laser beam Lw emitted to the second contact surface <NUM> can be increased in a stepped manner from when the second resin member <NUM> starts softening. This allows the laser beam Lw to be emitted in accordance with the state of the second resin member <NUM>. As a result, the first resin member <NUM> and second resin member <NUM> are joined with improved quality.

The present embodiment may be modified as follows. The present embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other.

In the above embodiment, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over the preset period from when reversal of the displacement direction of the second contact surface <NUM> is detected (that is, during period t12 and period t13 in above embodiment). Subsequently, the laser controller <NUM> gradually decreases the laser output when the preset period elapses. Instead, the laser controller <NUM> may, for example, decrease the laser output in a stepped manner when the predetermined period elapses. Alternatively, the laser controller <NUM> may, for example, control the laser emitter <NUM> to stop emission of the laser beam Lw when the predetermined period elapses.

The cooling of the first resin member <NUM> and the second resin member <NUM> may be started at a time point differing from that in the above embodiment.

For example, the laser controller <NUM> may be configured to control the laser emitter <NUM> to gradually decrease the laser output when detecting from the clamp control signal S2 provided to the input unit <NUM> that the clamping force is being decreased in a stepped manner and from the measurement signal S1 provided to the input unit <NUM> that a change amount of the displacement of the second contact surface <NUM> has been the same over a predetermined period.

By gradually decreasing the laser output in this manner, the first contact surface <NUM> and the second contact surface <NUM>, which are in a state molten and joined with each other, are gradually cooled. Also, the first contact surface <NUM> and the second contact surface <NUM> are gradually cooled as the clamping force applied to the first resin member <NUM> and the second resin member <NUM> decreases in a stepped manner. This reduces residual stress that occurs in the first resin member <NUM> and the second resin member <NUM> subsequent to cooling. As a result, the formation of cracks is further limited in the first resin member <NUM> and the second resin member <NUM>.

In a state in which, for example, the first contact surface <NUM> and the second contact surface <NUM> are both molten, when the clamping force applied by the clamping unit <NUM> to the first resin member <NUM> and the second resin member <NUM> is constant, there will be a period during which the change amount of the displacement of the second contact surface <NUM> becomes constant. Therefore, the cooling of the first resin member <NUM> and the second resin member <NUM> can be started at a time point suitable for the state of the first resin member <NUM> and the second resin member <NUM> during laser welding by gradually decreasing the laser output when detecting that the change amount of the displacement of the second contact surface <NUM> has been constant over a predetermined period. The change amount of the displacement of the second contact surface <NUM> being constant over the predetermined period can be detected, for example, when the change amount of the displacement measured by the displacement sensor <NUM> has been a value included in a range between preset threshold values over the predetermined period.

Alternatively, for example, the laser controller <NUM> may control the laser emitter <NUM> to gradually decrease the laser output or stop emission of the laser beam Lw when detecting that the displacement amount of the second contact surface <NUM> is equal to a preset displacement amount from the measurement signal S1 provided to the input unit <NUM>.

In the above embodiment, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period after a change in the displacement of the second contact surface <NUM> resulting thermal expansion of the second resin member <NUM> is detected based on the measurement signal S1 and when reversal of displacement direction of the second contact surface <NUM> is detected based on the measurement signal S1. Alternatively, the laser output may be increased in a stepped manner at a time point differing from that in the above embodiment after a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> is detected based on the measurement signal S1.

The laser controller <NUM> may be configured to control the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period, for example, from when a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> is detected based on the measurement signal S1 provided to the input unit <NUM>. In this manner, the laser output of the laser beam Lw emitted to the second contact surface <NUM> can be increased in a stepped manner from when the second resin member <NUM> starts thermal expansion. This allows the laser beam Lw to be emitted in accordance with the state of the second resin member <NUM>. As a result, the first resin member <NUM> and second resin member <NUM> are joined with improved quality.

Alternatively, the laser controller <NUM> may be configured to control the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period, for example, from when an increase in the clamping force is detected based on the clamp control signal S2 provided to the input unit <NUM>. In this manner, the laser output of the laser beam Lw emitted to the second contact surface <NUM> can be increased in a stepped manner from when the second resin member <NUM> starts thermal expansion in a case where the clamping force is increased in accordance with the change in the displacement of the second contact surface <NUM> resulting from the thermal expansion of the second resin member <NUM>. This allows the laser beam Lw to be emitted in accordance with the state of the second resin member <NUM>. As a result, the first resin member <NUM> and second resin member <NUM> are joined with improved quality.

In the above embodiment, the laser output is increased in a stepped manner by one step whenever a predetermined period elapses. Instead, the laser controller <NUM> may control the laser emitter <NUM> to increase the laser output in a stepped manner based on the measurement signal S1. For example, the laser controller <NUM> may control the laser emitter <NUM> to increase the laser output by one step whenever displacement (that is, position of contact surface in stacking direction X1) measured by the displacement sensor <NUM> based on the measurement signal S1 becomes equal to a preset displacement. Alternatively, the laser controller <NUM> may control the laser emitter <NUM> to increase the laser output by one step, for example, whenever detecting that the displacement amount of the second contact surface <NUM> in the positive direction based on the measurement signal S1 becomes equal to a preset displacement amount.

As shown in <FIG>, the laser welding apparatus <NUM> may further include a reactive force measuring sensor <NUM> that measures the reactive force added to the clamping unit <NUM> by at least one of the first resin member <NUM> or the second resin member <NUM> that is in contact with the clamping unit <NUM>. The control unit <NUM> may obtain the reactive force measured by the reactive force measuring sensor <NUM> and control the clamping unit <NUM> to increase or decrease the clamping force in accordance with the displacement amount of the second contact surface <NUM> obtained from the displacement sensor <NUM> and the reactive force obtained from the reactive force measuring sensor <NUM>.

As shown in <FIG>, in a laser welding apparatus 1A, the reactive force measuring sensor <NUM> is arranged on the movable stage <NUM> and exposed from the setting surface <NUM>. In <FIG>, same reference numerals are given to those components that are the same as the corresponding components of the above embodiment. The reactive force measuring sensor <NUM> contacts the second abutment surface <NUM> of the second resin member <NUM> arranged on the setting surface <NUM> and measures the reactive force added to the movable stage <NUM> by the second resin member <NUM>. An example of the reactive force measuring sensor <NUM> is a load cell.

The control unit <NUM> obtains the reactive force measured by the reactive force measuring sensor <NUM>. For example, the control unit <NUM> obtains the reactive force measured by the reactive force measuring sensor <NUM> continuously or intermittently.

When performing laser welding on the first resin member <NUM> and the second resin member <NUM>, the reactive force measured by the reactive force measuring sensor <NUM> is increased in correspondence with thermal expansion of the second resin member <NUM> at the stage in which the second resin member <NUM> is thermally expanded. Further, when the second resin member <NUM> starts softening, the reactive force measured by the reactive force measuring sensor <NUM> is decreased.

The control unit <NUM> controls the clamping unit <NUM> to increase the clamping force over a predetermined period, for example, when detecting that the reactive force obtained from the reactive force measuring sensor <NUM> is greater than a preset threshold value and that the second contact surface <NUM> is displaced by thermal expansion of the second resin member <NUM> based on the change in the displacement amount obtained from the displacement sensor <NUM>.

Subsequently, the control unit <NUM> controls the clamping unit <NUM> to decrease the clamping force in a stepped manner, for example, when detecting that the displacement direction of the second contact surface <NUM> is reversed based on the displacement amount obtained from the displacement sensor <NUM> and that the reactive force obtained from the reactive force measuring sensor <NUM> is less than the preset threshold value.

In this manner, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is increased or decreased in accordance with the reactive force, which is added to the clamping unit <NUM> by the second resin member <NUM>, in addition to the displacement amount of the second contact surface <NUM>. The reactive force added to the clamping unit <NUM> by the second resin member <NUM>, which is in contact with the clamping unit <NUM>, changes in accordance with the state of the first resin member <NUM> and the second resin member <NUM> during laser welding. Therefore, clamping force can be applied in a further suitable manner to the first resin member <NUM> and the second resin member <NUM> during laser welding in accordance with the state of the first resin member <NUM> and the second resin member <NUM> by further increasing or decreasing the clamping force applied to the first resin member <NUM> and the second resin member <NUM> in accordance with the reactive force. As a result, the formation of burrs and cracks is further limited in the first resin member <NUM> and the second resin member <NUM>.

The reactive force measuring sensor <NUM> may be arranged on the top panel <NUM> to contact the first abutment surface <NUM>.

In the above embodiment, the measurement signal S1 corresponding to the displacement amount measured by the displacement sensor <NUM> is provided to the input unit <NUM>. However, the measurement signal S1 does not have to be provided to the input unit <NUM>. In this case, the control unit <NUM> may provide the input unit <NUM> with, for example, a first detection signal indicating that a change in the displacement of the second contact surface <NUM> resulting from thermal expansion of the second resin member <NUM> has been detected based on the displacement amount obtained from the displacement sensor <NUM>. Further, the control unit <NUM> may provide the input unit <NUM> with a second detection signal indicating that reversal of the displacement direction of the second contact surface <NUM> has been detected based on the displacement amount obtained from the displacement sensor <NUM> when the reversal of the displacement direction of the second contact surface <NUM> is detected. In this case, the laser controller <NUM> controls the laser emitter <NUM> to increase the laser output in a stepped manner over a preset period, for example, after detecting that the first detection signal is provided to the input unit <NUM> and when detecting that the second detection signal is provided to the input unit <NUM>.

In the above embodiment, the displacement sensor <NUM> measures displacement of the setting surface <NUM> to measure displacement of the second contact surface <NUM>. Instead, the displacement sensor <NUM> may measure displacement of the setting surface <NUM> to measure displacement of the first contact surface <NUM>. Alternatively, instead of the setting surface <NUM>, the displacement sensor <NUM> may measure displacement of a surface that is displaced in the same manner as at least one of the first contact surface <NUM> or the second contact surface <NUM>. For example, the displacement sensor <NUM> may measure displacement of the surface of the movable stage <NUM> located at the side opposite to the setting surface <NUM> to measure displacement of at least one of the first contact surface <NUM> or the second contact surface <NUM>. Further, for example, when the displacement sensor <NUM> is an optical displacement sensor, the displacement sensor <NUM> may measure displacement of at least one of the first contact surface <NUM> or the second contact surface <NUM>.

In the above embodiment, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> is decreased in a stepped manner by one step whenever a predetermined period elapses. Instead, the control unit <NUM> may control the clamping unit <NUM> to decrease the clamping force applied to the first resin member <NUM> and the second resin member <NUM> in a stepped manner in accordance with the displacement amount measured by the displacement sensor <NUM>. For example, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> may be decreased by one step whenever displacement (that is, position of contact surface in stacking direction X1) measured by the displacement sensor <NUM> becomes equal to a preset displacement. Alternatively, the clamping force applied to the first resin member <NUM> and the second resin member <NUM> may be decreased by one step, for example, whenever a displacement amount in the positive direction becomes equal to a preset displacement amount.

The clamping unit <NUM> may contact and apply clamping force to the first resin member <NUM> in the stacking direction X1. Alternatively, the clamping unit <NUM> may contact and apply a clamping force to both of the first resin member <NUM> and the second resin member <NUM> in the stacking direction X1. In the clamping unit <NUM> of the above embodiment, for example, the movable stage <NUM> may be replaced by a fixed stage that is not moved in the stacking direction X1 during laser welding, and the top panel <NUM> may be a movable panel. In this case, the pressure adjustment unit <NUM> applies pressure to the top panel <NUM>, which is a movable panel, in the stacking direction X1 in order to apply clamping force to the first resin member <NUM> and ensure that the first contact surface <NUM> and the second contact surface <NUM> are pressed against each other. In this case, the displacement sensor <NUM> is configured to measure displacement of, for example, the surface of the top panel <NUM> that is in contact with the first abutment surface <NUM>. Instead of the surface of the top panel <NUM> contacting the first abutment surface <NUM>, the displacement sensor <NUM> may measure displacement of a surface that is displaced in the same manner as at least one of the first contact surface <NUM> or the second contact surface <NUM>.

Claim 1:
A laser welding apparatus that joins a first resin member (<NUM>), which is formed of a laser beam-transmissive resin and includes a first contact surface (<NUM>), and a second resin member (<NUM>), which is formed of a laser beam-absorbing resin and includes a second contact surface (<NUM>), by melting the first contact surface (<NUM>) and the second contact surface (<NUM>) with a laser beam in a state in which the first resin member (<NUM>) and the second resin member (<NUM>) are arranged one upon another with the first contact surface (<NUM>) contacting the second contact surface (<NUM>), the laser welding apparatus comprising:
a clamping unit (<NUM>) that abuts at least one of the first resin member (<NUM>) or the second resin member (<NUM>), which are arranged one upon the other, to apply clamping force to the at least one of the first resin member (<NUM>) or the second resin member (<NUM>);
a laser emitter (<NUM>) that emits a laser beam transmitted through the first resin member (<NUM>);
a laser controller (<NUM>) that controls a laser output of the laser beam emitted from the laser emitter (<NUM>);
a displacement sensor (<NUM>) that measures displacement of at least one of the first contact surface (<NUM>) or the second contact surface (<NUM>) in a direction in which the first resin member (<NUM>) and the second resin member (<NUM>) are arranged one upon the other; and
a control unit (<NUM>) that continuously or intermittently obtains a displacement amount of the at least one of the first contact surface (<NUM>) or the second contact surface (<NUM>) from the displacement sensor (<NUM>) and controls the clamping unit (<NUM>) to increase or decrease the clamping force in accordance with the obtained displacement amount of the at least one of the first contact surface (<NUM>) or the second contact surface (<NUM>).