Method and apparatus for quenching pipe material

Abstract

A first pipe material group in coaxial contact on the upstream side of a pipe material to be quenched and a second pipe material group in coaxial contact on the upstream side of a first upstream pipe material are brought into contact with each other in an eccentric state and conveyed. Speed information, which is information having correlation with the conveying speed of the first pipe material group and / or the second pipe material group, is detected by a speed detection means. A step part produced by the eccentric state between the first pipe material group and the second pipe material group is detected by a displacement detection means. The start time and duration of a heating treatment by a heating coil unit are calculated on the basis of the speed information obtained by the speed detection means, the timing at which the step part is obtained from the displacement detection means, and the distance between the heating coil unit and the displacement detection means. A heating treatment is applied to a prescribed region of the pipe material to be quenched. Consequently, when a plurality of pipe materials are continuously conveyed on a conveyance path in a state in which the pipe materials are in contact with each other, the arrival of the front end (downstream end) of the pipe materials is reliably detected, and heating treatment is precisely applied by the heating coil unit, on the basis of the detection information, on only the to-be-quenched portion of the pipe material to be quenched.

Description

Method and apparatus for quenching pipe materials

[0001] The present invention relates to a method and apparatus for quenching pipe materials, which involves continuously passing multiple pipe materials at a predetermined speed through a heating coil section and a cooling section installed on a transport path to perform a quenching treatment on the pipe materials.

[0002] Figure 6 is a schematic perspective view showing an example of the configuration of a door impact beam (DIB) in an automobile, where a predetermined area (see shaded area) of the tubing material constituting the DIB has been heat-treated. In the heat-treated area of ​​the tubing material, effects such as improved mechanical properties such as mechanical strength, durability, hardness, and / or wear resistance are achieved, and the function of the DIB in preventing deformation of the passenger compartment during a collision is enhanced. Note that while Figure 6 illustrates tubing material with heat treatment applied only to a predetermined area, heat treatment may also be applied to the entire tubing material.

[0003] On the other hand, the ends of the pipes that make up the DIB are often flattened into a plate shape (see the area enclosed by the thick dashed line) as illustrated in Figure 7, or flattened so that the corners become beveled, as disclosed in Patent Document 1, for purposes such as welding to brackets called "extensions" and / or preventing them from piercing the outer plate of the door during a collision. From the viewpoint of reducing the processing load when flattening the ends of the pipes and avoiding the occurrence of defects such as cracks, it is desirable that the ends of the pipes that make up the DIB are not hardened. Furthermore, pipes that are hardened only in a predetermined area and not in other areas are used not only in DIBs but also in various applications where high mechanical properties are required.

[0004] Therefore, in the relevant technical field, a quenching device for continuously quenching a pipe material is known. The device according to the prior art continuously conveys a plurality of pipe materials on a linear conveying path while abutting them by a conveying mechanism, and passes each pipe material through a heating coil section installed on the linear conveying path at a constant speed, so as to continuously perform a quenching process over the entire length of each pipe material or in a predetermined region. The quenching process is performed by a heat treatment and a rapid cooling treatment immediately after the heat treatment. In a continuous quenching device, control of the position (timing) and heating amount of the heat treatment is particularly important.

[0005] When it is desired to perform a quenching process only on a predetermined region (a certain range in the axial direction) of a pipe material by the above-described quenching device, it is necessary to energize the heating coil section only while the portion to be quenched (hereinafter sometimes referred to as the "quenched portion") of the pipe material to be quenched (hereinafter sometimes referred to as the "pipe material to be quenched") passes through the heating coil section after arriving at the heating coil section. Therefore, it is necessary to accurately grasp the conveying position of the pipe material to be quenched, predict the timing when the quenched portion arrives at the heating coil section from the position information and the conveying speed information, and start energization to the heating coil section at that timing and maintain the energization for a certain period.

[0006] For example, in the invention described in Patent Document 2, a plurality of pipe materials are conveyed on a conveying path composed of a conveying roller mechanism. The arrival of the front end (downstream end) of the upstream pipe material is detected by a proximity switch LS1, and based on the detection information, the time T1 when the front end of the upstream pipe material arrives at the heating coil section is calculated, and a timer is operated to perform energization to the heating coil section after the time T1.

[0007] Japanese Patent Application Laid-Open No. 5-213063 Japanese Patent No. 3643420

[0008] However, detecting the contact points between pipes that are coaxially abutting each other using proximity switches is extremely difficult, and false detections are frequent. The invention described in Patent Document 2 incorporates a control mechanism that individually controls the transport speed of the pipes before they reach the heating coil, creating a gap between the upstream and downstream pipes in the transport direction. As a result, there is a high possibility of errors occurring between the calculated energizing timing of the heating coil and the actual energizing timing of the heating coil (the timing when the part to be heated arrives at the heating coil). When errors occur in the energizing timing in this way, the part to be hardened shifts in the axial direction of the pipe, making it a challenge to set the energizing timing to accurately match the timing when the part to be hardened arrives at the heating coil.

[0009] In view of the above-mentioned problems, one objective of the present invention is to provide a method and apparatus for quenching pipes that can reliably detect the arrival of the front end (downstream end) of a pipe when a plurality of pipes are continuously transported on a transport path in a state where they are in contact with each other by a transport mechanism, and based on the detection information, accurately apply heat treatment to only the portion of the pipe to be quenched using a heating coil.

[0010] The method for quenching pipes to achieve the above objective involves transporting a plurality of pipes, with their ends in contact with each other, on a transport path at a predetermined speed, and applying current to a heating coil installed on the transport path for a predetermined period of time, starting from a predetermined time, when one of the plurality of pipes, which is the pipe to be quenched, passes over the heating coil, thereby applying heat treatment to a predetermined region, the first region, of the pipe to be quenched. In this quenching method, the upstream end of a first group of pipes, which is a group of pipes in contact with each other substantially coaxially upstream of the pipe to be quenched, and the downstream end of a second group of pipes, which is a group of pipes in contact with each other substantially coaxially upstream of the first group of pipes, are transported in an eccentric manner. Furthermore, speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes, is detected by a speed detection means. Furthermore, the step portion resulting from the eccentricity between the first and second pipe groups is detected by the displacement detection means. In addition, the first time point and the first period are calculated based on the velocity information obtained by the velocity detection means, the second time point which is the timing when the step portion is detected by the displacement detection means, and the first distance which is the distance between the heating coil and the displacement detection means in the direction of pipe transport, and the first region of the pipe to be hardened is subjected to the hardening treatment.

[0011] According to this method, the timing at which the front end of the pipe located at the downstream end of the second pipe group reaches the heating coil can be accurately calculated based on speed information, which is information correlated with the conveying speed of the pipe material detected by the speed detection means, a second time point, which is the timing at which a step (i.e., the downstream end of the second pipe material group) detected by the displacement detection means is detected, and a first distance, which is the distance between the heating coil and the displacement detection means in the conveying direction of the pipe material. Therefore, it is possible to eliminate detection errors in the timing at which the downstream end (step) of the second pipe material group reaches the displacement detection means, and to eliminate the discrepancy between the calculated start timing of the heating treatment (the timing at which the calculated power supply to the heating coil begins) and the timing at which the pipe material to be hardened should arrive at the heating coil and the heating treatment should begin (the timing at which power supply to the heating coil should begin), thereby enabling accurate heating treatment over a desired range (first region) of the pipe material to be hardened.

[0012] Furthermore, the transport path includes an upstream transport path and a downstream transport path that is offset vertically downward from the upstream transport path. The downstream pipe (hereinafter sometimes referred to as the "second upstream pipe") among the multiple pipes constituting the second group of pipes being transported on the upstream transport path falls onto the downstream transport path, causing it to separate from the second group of pipes and join the first group of pipes, becoming the upstream pipe (hereinafter sometimes referred to as the "first upstream pipe") among the multiple pipes constituting the first group of pipes. At the same time, a step may be formed at the contact point between the upstream end of the first group of pipes and the downstream end of the second group of pipes.

[0013] With the above-described transport path configuration, the difference in height between the surface of the first upstream pipe and the surface of the second upstream pipe creates a step at the contact point between the rear end (upstream end) of the first pipe group and the front end (downstream end) of the second pipe group. Therefore, the position of the front end (downstream end) of the second pipe group can be reliably detected by the displacement detection means.

[0014] Furthermore, a second period may be provided, during which the intensity of the heat treatment applied to the quenched pipe material by the heating coil is increased at a predetermined rate for a predetermined period immediately preceding the start of the first period, and / or a third period may be provided, during which the intensity of the heat treatment applied to the quenched pipe material by the heating coil is decreased at a predetermined rate for a predetermined period immediately following the end of the first period. For example, in the second period, the intensity of the heat treatment applied to the quenched pipe material by the heating coil can be increased at a predetermined rate by increasing the current applied to the heating coil (device output) at a predetermined rate. On the other hand, in the third period, the intensity of the heat treatment applied to the quenched pipe material by the heating coil can be decreased at a predetermined rate by decreasing the current applied to the heating coil at a predetermined rate.

[0015] By providing the second and / or third periods described above, a region can be created in the pipe material where the intensity of the heat treatment gradually changes between the heat-treated and untreated regions. As a result, for example, when excessive stress is applied to the pipe material, the risk of stress concentrating at the boundary between the hardened and unhardened regions of the pipe material, which could lead to problems such as crushing and / or fracture of the pipe material, can be reduced.

[0016] Alternatively, the heat-treated quenched pipe material may be cooled by a cooling section provided in the downstream transport path downstream of the heating coil.

[0017] By installing a cooling unit in this manner, the hardened portion (the area of ​​the hardened pipe material that has undergone heat treatment) can be cooled quickly and reliably immediately after the heat treatment, thereby achieving an effective hardening effect.

[0018] Alternatively, multiple cooling sections may be provided in the downstream transport path downstream of the heating coil section, and the heat-treated quenched pipe material may be transported or supported by a transport mechanism or support mechanism positioned between adjacent cooling sections.

[0019] As described above, by arranging a transport mechanism or support mechanism between adjacent cooling sections, even pipes with a shorter distance than the distance between adjacent cooling sections can be sufficiently cooled by multiple cooling sections without falling off the transport path.

[0020] The quenching apparatus that achieves the above objective transports a plurality of pipes with their ends in contact with each other on a transport path at a predetermined speed, and applies current to the heating coil section installed on the transport path only for a predetermined period from a predetermined timing, the first time point, when passing one of the plurality of pipes, which is the pipe to be quenched, to the heating coil section, thereby performing heat treatment on a predetermined area, the first region, of the pipe to be quenched. The quenching apparatus further comprises a transport path, speed detection means, displacement detection means, and calculation means. The transport path transports the pipes while bringing the upstream end of a first group of pipes, which is a group of plurality of pipes in contact with each other substantially coaxially upstream of the pipe to be quenched, and the downstream end of a second group of pipes, which is a group of plurality of pipes in contact with each other substantially coaxially upstream of the first group of pipes, in an eccentric state. The speed detection means detects speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes. The displacement detection means detects the step caused by the eccentricity between the first group of pipes and the second group of pipes. The calculation means calculates the first time point and the first period based on the velocity information obtained by the velocity detection means, the second time point which is the timing when the step is detected by the displacement detection means, and the first distance which is the distance between the heating coil and the displacement detection means in the direction of pipe transport.

[0021] With such a hardening apparatus, the timing at which the front end of the pipe located at the downstream end of the second group of pipes reaches the heating coil can be accurately calculated by a calculation means based on speed information, which is information correlated with the conveying speed of the pipe material detected by a speed detection means, a second time point, which is the timing at which a stepped portion (i.e., the downstream end of the second group of pipe materials) detected by a displacement detection means is detected, and a first distance, which is the distance between the heating coil and the displacement detection means in the conveying direction of the pipe material.Therefore, detection errors in the timing at which the downstream end (stepped portion) of the second group of pipe materials reaches the displacement detection means can be eliminated, and the discrepancy between the calculated start timing of the heat treatment (the timing at which the calculated power supply to the heating coil begins) and the timing at which the pipe material to be hardened should arrive at the heating coil and the heat treatment should begin (the timing at which power supply to the heating coil should begin) can be eliminated, and the heat treatment can be accurately applied over a desired range (first region) of the pipe material to be hardened.

[0022] Furthermore, the transport path includes an upstream transport path and a downstream transport path that is offset vertically downward from the upstream transport path. The downstream pipe (second upstream pipe) among the multiple pipes constituting the second group of pipes being transported on the upstream transport path falls onto the downstream transport path, thereby separating from the second group of pipes and joining the first group of pipes, becoming the upstream pipe (first upstream pipe) among the multiple pipes constituting the first group of pipes. At the same time, a step may be formed at the contact point between the upstream end of the first group of pipes and the downstream end of the second group of pipes.

[0023] With the above-described transport path configuration, the difference in height between the surface of the first upstream pipe and the surface of the second upstream pipe creates a step at the contact point between the rear end (upstream end) of the first pipe group and the front end (downstream end) of the second pipe group. Therefore, the position of the front end (downstream end) of the second pipe group can be reliably detected by the displacement detection means.

[0024] Furthermore, a second period may be provided, during which the intensity of the heat treatment applied to the quenched pipe material by the heating coil is increased at a predetermined rate for a predetermined period immediately preceding the start of the first period, and / or a third period may be provided, during which the intensity of the heat treatment applied to the quenched pipe material by the heating coil is decreased at a predetermined rate for a predetermined period immediately following the end of the first period. For example, in the second period, the intensity of the heat treatment applied to the quenched pipe material by the heating coil can be increased at a predetermined rate by increasing the current applied to the heating coil at a predetermined rate. On the other hand, in the third period, the intensity of the heat treatment applied to the quenched pipe material by the heating coil can be decreased at a predetermined rate by decreasing the current applied to the heating coil at a predetermined rate.

[0025] By providing the second and / or third periods described above, a region can be created in the pipe material where the intensity of the heat treatment gradually changes between the heat-treated and untreated regions. As a result, for example, when excessive stress is applied to the pipe material, the risk of stress concentrating at the boundary between the hardened and unhardened regions of the pipe material, which could lead to problems such as crushing and / or fracture of the pipe material, can be reduced.

[0026] Alternatively, the heat-treated quenched pipe material may be cooled by a cooling section provided in the downstream transport path downstream of the heating coil. By installing a cooling section in this way, the quenched portion (the part of the quenched pipe material that has undergone quenching treatment) can be cooled quickly and reliably immediately after the heat treatment, thereby achieving an effective quenching effect.

[0027] The present invention provides a method for quenching pipes that, when multiple pipes are continuously transported on a transport path in a state where they are in contact with each other by a transport mechanism, reliably detects the arrival of the leading end (downstream end) of the pipes, and based on this detection information, accurately applies heat treatment only to the portion of the pipe to be quenched using a heating coil.

[0028] The pipe hardening apparatus according to the present invention provides a pipe hardening apparatus that can reliably detect the arrival of the front end (downstream end) of a pipe when a plurality of pipes are continuously transported on a transport path in a state where they are in contact with each other by a transport mechanism, and based on the detection information, accurately apply heat treatment to only the portion of the pipe to be hardened by the heating coil.

[0029] This is a schematic side view illustrating the configuration of a pipe hardening apparatus according to the first embodiment of the present invention. This is a schematic side view illustrating the configuration of a pipe after hardening treatment according to the first embodiment of the present invention. This is a schematic side view and top view of the vicinity of the end of a pipe having a flattened end. This is a schematic diagram illustrating the vicinity of the cooling section of a pipe hardening apparatus according to a preferred third embodiment of the present invention. This is a schematic three-view diagram illustrating the configuration of a support mechanism disposed between a plurality of cooling sections of a pipe hardening apparatus according to a preferred third embodiment of the present invention. This is a schematic perspective view showing an example of the configuration of a door impact beam (DIB) of an automobile. This is a schematic perspective view showing an example of the configuration of the end of a pipe constituting a DIB.

[0030] Hereinafter, preferred embodiments of the present invention will be described with reference to Figure 1. In the first embodiment, in view of the orientation of the pipe hardening apparatus during installation and operation, the top of the figure is defined as the top of the apparatus, and the left and right directions of the figure are defined as the horizontal direction and conveying direction of the apparatus, with the pipe being conveyed from right to left. That is, the right side of the figure is the upstream direction in the conveying direction of the pipe.

[0031] (First Embodiment) Figure 1 is a schematic side view showing the configuration of a pipe hardening apparatus 1 according to the first embodiment of the present invention. The hardening apparatus 1 comprises a transport path 2, a heating coil section 9, a speed detection means 10, a displacement detection means 11, and a calculation means (not shown). The transport path 2, which is composed of a plurality of rollers 13, is arranged horizontally and mounted on the upper surface of an apparatus body (not shown), and the rollers 13 are driven and controlled by a drive device (not shown). The plurality of rollers 13 have rotation axes perpendicular to the transport direction, and by rotating, they transport the pipe material 5 placed on the transport path 2 downstream. Since such roller-type transport mechanisms are well known in continuous hardening apparatuses, a detailed explanation is omitted here. The transport path 2 is installed horizontally in the operating state, and a plurality of pipe materials 5 are transported on the transport path 2 from right to left in the figure (i.e., from upstream to downstream) at a predetermined constant speed with their end faces in contact with each other in the direction of the pipe axis. The number of pipes 5 continuously transported along the transport path 2 is not particularly limited, but in this embodiment, the minimum number is preferably four, as illustrated in Figure 1.

[0032] The transport path 2 comprises an upstream transport path 3 and a downstream transport path 4. The downstream transport path 4 is positioned vertically downward offset from the upstream transport path 3. That is, the downstream transport path 4 and the upstream transport path 3 are installed parallel and horizontally. The offset amount is determined based on the minimum pipe material eccentricity that allows the displacement detection means 11, described later, to reliably detect the step portion 14. The offset direction may be oblique to the vertical, but a vertical offset is preferred in order to maintain the accurate dropping of the pipe material 5. In Figure 1, the pipe material 5 located furthest downstream among the multiple pipe materials 5 (i.e., the second group of pipe materials) transported on the upstream transport path 3 is the second upstream pipe material 8, and the pipe material 5 located furthest upstream among the multiple pipe materials 5 (i.e., the first group of pipe materials) transported on the downstream transport path 4 is the first upstream pipe material 7. The first upstream pipe 7 and each of the pipes 5 downstream thereof are in contact with each other in a substantially coaxial manner, and the second upstream pipe 8 and each of the pipes 5 upstream thereof (not shown) are also in contact with each other in a substantially coaxial manner. When the second upstream pipe 8 is transported along the upstream transport path 3 and falls onto the downstream transport path 4, it becomes a new first upstream pipe 7, and a stepped portion 14 is formed between the upstream end (rear end) of the new first upstream pipe 7 and the downstream end (front end) of the new second upstream pipe 8. That is, the stepped portion 14 is sequentially formed at the contact point between the upstream end of the first pipe group and the downstream end of the second pipe group. The upstream end of the first upstream pipe 7 and the downstream end of the second upstream pipe 8 form a contact point where they are in contact with each other in an eccentric state.

[0033] In the quenching apparatus 1 illustrated in Figure 1, a speed detection means 10 is provided on the upstream transport path 3 to detect the actual speed (actual transport speed value) of the second upstream pipe material 8 as speed information, which is information correlated with the transport speed of multiple pipe materials 5 (second group of pipe materials) transported on the upstream transport path 3. In this embodiment, the speed detection means 10 is provided so as to be rotatable in contact with the upper surface of the second upstream pipe material 8, and detects the transport speed of the transported second upstream pipe material 8. Specifically, the speed detection means 10 is composed of a driven rotating part that contacts the surface of the second upstream pipe material 8 and an encoder part driven by the driven rotating part. The encoder outputs a signal corresponding to the angular velocity or angular acceleration correlated with the actual speed (actual transport speed value) detected by the encoder to a calculation means (not shown), and the calculation means calculates the transport speed of the second upstream pipe material 8 based on the signal. Furthermore, the speed detection means 10 is not limited to this method; for example, an encoder may be built into and / or linked to the roller 13, or a non-contact type magnetic and / or optical speed detection means may be used.

[0034] Furthermore, a displacement detection means 11 is provided in the upstream transport path 3, close to the upper surface of the second upstream pipe material 8, to detect the step portion 14 that occurs at the contact surface between the transported second upstream pipe material 8 and the first upstream pipe material 7. Specifically, using a proximity sensor or a laser displacement sensor as the displacement detection means 11, it detects when the second upstream pipe material 8 falls from the upstream transport path 3 to the downstream transport path 4 and becomes the first upstream pipe material 7, creating a space directly below the displacement detection means 11, or when the pipe material 5 that subsequently becomes the front end (downstream end) of the new second upstream pipe material 8 reaches directly below the displacement detection means and fills the space, and outputs a corresponding output signal to a calculation means (not shown). Upon receiving the output signal, the calculation means generates position information which includes the timing (second time point) when the front end of the second upstream pipe material 8 arrives directly below the displacement detection means 11.

[0035] Thus, the displacement detection means 11 in this embodiment can recognize the arrival of the front end of the second upstream pipe 8 not by the contact surface (line) between the pipes, but by the external shape of the stepped portion 14, thereby significantly reducing the possibility of false detection. It should be noted that the detection of the stepped portion 14 is not limited to the method described in this embodiment; for example, the stepped shape itself may be detected using an image recognition device or the like.

[0036] The calculation means (not shown) calculates the required time for the front end of the second upstream pipe material 8 to reach the heating coil section 9, using the transport speed of the second upstream pipe material 8 calculated from the speed information detected by the speed detection means 10, the second time point as position information detected by the displacement detection means 11, and the distance α between the stepped section 14 and the heating coil section 9. It then calculates the time when the required time has elapsed from the time when the stepped section 14 is detected by the displacement detection means 11 (second time point), i.e., the time when the front end (downstream end) of the second upstream pipe material 8 reaches the heating coil section 9 (first time point), and the period during which the part to be hardened 15 (the part of the pipe material 6 to be hardened that requires hardening) passes through the heating coil section 9 to obtain the desired hardening range (heating period = first period). Then, by applying current to the heating coil section 9 only from the first time point to the first period calculated in this way, the part to be hardened 15 of the pipe material 6 to be hardened is subjected to heat treatment.

[0037] Furthermore, for example, in order to improve the uniformity of the hardening treatment on the hardened portion 15 of the pipe material to be hardened 6, the hardening apparatus 1 may be configured to transport the pipe material 5 entering the hardening treatment section, which is composed of a heating coil section 9 and a cooling section 12, and the pipe material 6 exiting the hardening treatment section, while rotating them around an axis, as illustrated by the thick dashed arrows in Figure 1.

[0038] Figure 2 is a schematic diagram illustrating the configuration of the quenched pipe material 6 that has been heat-treated as described above. In the quenched pipe material 6 illustrated in Figure 2, the quenched portion 15, which is the region located on the downstream end (front end) side of the quenched pipe material 6, is heat-treated. The size of the dimension (length) β of this quenched portion 15 in the transport direction (longitudinal direction) is determined by the length of the first period, which is the period during which the heating coil 9 is energized, and the transport speed of the quenched pipe material 6 (i.e., the transport speed of the second upstream pipe material 8).

[0039] As mentioned above, the speed detection means detects speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes. Therefore, although in the above description the displacement detection means 11 was provided in the upstream transport path 3 so as to be close to the upper surface of the second upstream pipe 8 (included in the second group of pipes), the displacement detection means 11 may also be provided in the downstream transport path 4 so as to be close to the upper surface of the first upstream pipe 7 (included in the first group of pipes).

[0040] Furthermore, the above description described a case in which the actual speed (actual transport speed value) of the second upstream pipe material 8, calculated by the calculation means based on the output signal from the speed detection means 10, is used to identify the first time point, which is the timing for starting to energize the heating coil section 9, and the first period, which is the period during which the heating coil section 9 is energized. However, as mentioned above, the speed detection means detects speed information, which is information correlated with the transport speed of the first group of pipe materials and / or the second group of pipe materials. Therefore, as another calculation method in the calculation means, if the speed detection means 10 is an encoder, the first time point and the first period may be identified without converting the pulse signal output from the encoder to the transport speed.

[0041] For example, the system calculates how many pulse signals must be detected after the front end (downstream end) of the second upstream pipe 8 reaches the displacement detection means 11 for the transport distance of the pipe to match the distance α between the stepped section 14 and the heating coil section 9. By starting to supply power to the heating coil section 9 when that number of pulse signals is reached (= first time point), the heating process of the hardened section 15 (extending from the downstream end (front end) of the hardened pipe 6, as illustrated in Figure 2) can be started. If there is a certain distance between the downstream end (front end) of the hardened section 15 and the downstream end (front end) of the hardened pipe 6 (they are separated), the number of pulse signals corresponding to that distance should be added. Similarly, the power supply to the heating coil section 9 should be continued until the length β of the hardened section 15 reaches the corresponding number of pulse signals. In other words, in this case, the speed detection means detects the pulse signals as speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes. Furthermore, the speed information detected by the speed detection means is not limited to the above, and is not particularly limited as long as it is information that correlates with the transport speed of the first group of pipes and / or the second group of pipes.

[0042] The heating coil section 9 is installed in the downstream transport path 4, and as the pipe material to be hardened 6 passes through its interior at a constant speed, current is supplied at a predetermined timing (first time point) and continues for a predetermined period (first period). This makes it possible to obtain a hardened section 15 that has been heat-treated over a predetermined region β.

[0043] Thus, based on the speed information of the pipe material detected by the speed detection means, the position information including the second time point which is the timing when the step portion formed at the contact portion between the first pipe material group and the second pipe material group detected by the displacement detection means arrives, and the first distance which is the distance between the heating coil portion and the displacement detection means in the conveying direction of the pipe material, the calculation means can accurately calculate the first time point which is the timing when the quenched portion of the quenched pipe material reaches the heating coil portion. Therefore, it is possible to eliminate the detection error at the timing when the downstream end (step portion) of the second pipe material group reaches the displacement detection means, and to eliminate the deviation between the calculated start timing of the heat treatment (the timing to start energization to the calculated heating coil portion) and the timing when the quenched pipe material arrives at the heating coil portion and the heat treatment should be started (the timing to start energization to the heating coil portion), and it is possible to accurately perform the heat treatment over the desired range (first region) of the quenched pipe material.

[0044] (Second Embodiment) By the way, as described above while referring to FIG. 6, a quenching treatment is performed on a predetermined region of the pipe material constituting the door impact beam (DIB) of an automobile. In the region where the quenching treatment is performed on the pipe material, for example, effects such as improvement of mechanical properties such as mechanical strength, durability, hardness, and / or wear resistance are achieved, and for example, functions such as preventing deformation of the passenger compartment during a side collision as a DIB are enhanced. On the other hand, the ends of the pipe materials constituting the DIB are often crushed into a flat shape as illustrated in FIG. 7, or crushed so that the corners become beveled as disclosed in Patent Document 1. Therefore, for the purpose of reducing the processing load when crushing the ends of the pipe materials and avoiding the occurrence of defects such as cracks, the ends of the pipe materials constituting the DIB are not subjected to the quenching treatment. As a result, for example, when an excessive stress acts during a vehicle collision or the like, stress concentrates at the boundary portion between the region where the quenching treatment is performed on the pipe material and the region where the quenching treatment is not performed, and there is a risk of problems such as crushing and / or breaking of the pipe material.

[0045] The problem caused by stress concentration at the boundary between the area where the quenching treatment is applied to the pipe material and the area where the quenching treatment is not applied as described above is not limited to the pipe material constituting the DIB, but is a common problem for various pipe materials in which the area where the quenching treatment is applied and the area where the quenching treatment is not applied coexist. From the viewpoint of reducing such a problem, it is preferable to provide a region (gradual change region) where the intensity of the quenching treatment gradually changes between the region where the quenching treatment is applied to the pipe material and the region where the quenching treatment is not applied.

[0046] Therefore, in the quenching device for pipe materials according to the second embodiment of the present invention, a second period, which is a period in which the intensity of the heat treatment of the pipe material to be quenched by the heating coil unit is increased at a predetermined speed over a predetermined period immediately before the start of the first period, and / or a third period, which is a period in which the intensity of the heat treatment of the pipe material to be quenched by the heating coil unit is decreased at a predetermined speed over a predetermined period immediately after the end of the first period, is provided.

[0047] FIG. 3 is a schematic side view (a) and top view (b) of the vicinity of the end of a pipe material having an end crushed into a flat plate shape, like the pipe material described with reference to FIG. 7. In the pipe material illustrated in (a) of FIG. 3, a region R1 where the quenching treatment is applied is provided, and a region R2 where the quenching treatment is not applied is left in the vicinity of the end. Between the region R1 and the region R2, a region R3, which is a gradual change region where the intensity of the quenching treatment gradually decreases as it progresses from the region R1 side to the region R2 side, is provided.

[0048] Therefore, even if the region between the region R1 where the quenching treatment is applied and the end is crushed into a region R4 by pressing, as illustrated in (b) of FIG. 3, for example, the risk of problems such as crushing and / or breaking of the pipe material can be reduced.

[0049] The above-described gradual change region may be provided on the downstream side (front end side) of the hardened portion of the hardened pipe material by providing a second period, which is a period during which the intensity of the heat treatment applied to the hardened pipe material by the heating coil is increased at a predetermined rate for a predetermined period immediately before the start of the period (first period) during which the intended heat treatment is applied to a predetermined area (first region) of the pipe material. Alternatively, the gradual change region may be provided on the upstream side (rear end side) of the hardened portion of the hardened pipe material by providing a third period, which is a period during which the intensity of the heat treatment applied to the hardened pipe material by the heating coil is decreased at a predetermined rate for a predetermined period immediately after the end of the first period. Furthermore, the gradual change region may be provided on the downstream side (front end side) and the upstream side (rear end side) of the hardened portion of the hardened pipe material by providing the second and third periods before and after the first period, respectively.

[0050] Furthermore, the intensity of the heat treatment applied to the pipe material to be hardened by the heating coil can be changed by controlling the current applied to the heating coil (the voltage or current applied to the heating coil). For example, in the second period, the intensity of the heat treatment applied to the pipe material to be hardened by the heating coil can be increased at a predetermined rate by increasing the current applied to the heating coil at a predetermined rate. On the other hand, in the third period, the intensity of the heat treatment applied to the pipe material to be hardened by the heating coil can be decreased at a predetermined rate by decreasing the current applied to the heating coil at a predetermined rate. In addition, it is necessary to adjust the current applied to the heating coil and / or the length of the current application period by appropriately taking into account various conditions such as the oscillator output when the heating coil is energized, the rise time, and / or the length of the heating coil (the dimensions of the heating coil in the direction of pipe transport).

[0051] Furthermore, the rate at which the intensity of the heat treatment (the current applied to the heating coil) is increased during the second period can be appropriately set according to, for example, the length of the gradual change region to be provided on the pipe material to be hardened and the transport speed of the pipe material to be hardened. Also, even if the intensity of the heat treatment (the current applied to the heating coil) is changed from zero (0) to the maximum at a certain point in time, the temperature of the hardened portion of the pipe material to be hardened does not reach the maximum temperature instantaneously, but requires a certain period of heating, albeit a very short period. Therefore, the period until the temperature of the hardened portion of the pipe material to be hardened reaches the maximum temperature during such a short period may also correspond to the second period described above. Similarly, the rate at which the intensity of the heat treatment (the current applied to the heating coil) is decreased during the third period can also be appropriately set according to, for example, the length of the gradual change region to be provided on the pipe material to be hardened and the transport speed of the pipe material to be hardened. Furthermore, even if the intensity of the heat treatment (the current applied to the heating coil) is changed from maximum to zero at a given point in time, the temperature of the hardened portion of the hardened pipe material does not instantly reach the ambient temperature; rather, a certain cooling period is required, albeit for a very short time. Therefore, the period during which the temperature of the hardened portion of the hardened pipe material decreases from the maximum temperature to the ambient temperature may also correspond to the third period described above.

[0052] By providing the second and / or third periods described above, a region can be created in the pipe material where the intensity of the heat treatment gradually changes between the heat-treated and untreated regions. As a result, for example, when excessive stress is applied to the pipe material, the risk of stress concentrating at the boundary between the hardened and unhardened regions of the pipe material, which could lead to problems such as crushing and / or fracture of the pipe material, can be reduced.

[0053] (Third Embodiment) Incidentally, depending on the mechanical properties required for the hardened portion of the pipe material to be hardened, it may be preferable to perform the hardening treatment by rapidly cooling immediately after heating with the heating coil, for example, to increase the hardness of the hardened portion of the pipe material to be hardened.

[0054] Therefore, in the pipe hardening apparatus according to the third embodiment of the present invention, the pipe material to be hardened, which has been heat-treated by the heating coil, is cooled by a cooling unit provided in the downstream transport path downstream of the heating coil.

[0055] The configuration of the cooling unit is not particularly limited, as long as it is capable of cooling the quenched pipe material that has been heat-treated by the heating coil unit. For example, the cooling unit may be configured to spray a liquid such as water or oil, or a gas such as air, as a coolant onto the quenched pipe material that has been heat-treated by the heating coil unit.

[0056] The quenching apparatus 1 illustrated in Figure 1 includes a cooling section 12 that rapidly cools the part to be quenched 15 (surface quenched area) by water spray immediately after the heating coil section 9. That is, the quenching apparatus 1 illustrated in Figure 1 also satisfies the constituent requirements of the pipe quenching apparatus according to the third embodiment of the present invention. The cooling section 12 is provided in the downstream transport path 4 near the downstream side of the heating coil section 9. Since such heating coil section 9 and cooling section 12 are well known in continuous quenching apparatuses, a detailed explanation will be omitted.

[0057] Furthermore, for example, an additional cooling unit may be arranged downstream of the cooling unit 12 at a certain distance. By applying cooling, reheating, and recooling to the part to be hardened 15 using multiple cooling units arranged at predetermined distances, it becomes possible to perform hardening treatment with a desired cooling pattern or to increase the overall cooling capacity of the apparatus. Also, even if the distance between adjacent cooling units exceeds the length of each individual pipe 5, by arranging intermediate rollers between adjacent cooling units, it is possible to prevent the pipe 5 from falling off the transport path 2, thereby enabling smooth hardening and cooling treatment.

[0058] Accordingly, in the preferred third embodiment of the present invention, a plurality of cooling units are provided in the downstream transport path downstream of the heating coil. In addition, the quenching apparatus is configured to transport or support the heat-treated quenched tubing material by a transport mechanism or support mechanism arranged between adjacent cooling units.

[0059] Figure 4 is a schematic diagram illustrating the configuration near the cooling section of a pipe hardening apparatus according to a preferred third embodiment of the present invention. The hardening apparatus 1c illustrated in Figure 4 is equipped with a plurality (two) of cooling sections 12 and 16 downstream of the heating coil section 9 in the transport path 2, and is configured to transport the hardened pipe material 5 (pipe material to be hardened 6) by an intermediate roller 17a, which constitutes a transport mechanism (not shown) arranged between the cooling section 12 and the cooling section 16. As a result, even though the distance between the two adjacent cooling sections 12 and 16 is longer than the length of the pipe material 5, the pipe material 5 can be prevented from falling off the transport path 2 and the hardening and cooling processes can be performed. In the example shown in Figure 4, the rotation axis of the intermediate roller 17a is perpendicular to the transport direction of the pipe material 5. However, the configuration of the intermediate roller provided in the transport mechanism or support mechanism arranged between adjacent cooling sections is not limited to the above. Also, in Figure 4, the spacing between the roller 13 and the intermediate roller 17a is depicted as wide for the purpose of simplifying the drawing. However, in the actual conveying mechanism, the rollers 13 and intermediate rollers 17a are arranged at intervals that allow the pipe material 5 (hardened pipe material 6) to be conveyed in a predetermined position without falling off.

[0060] Figure 5 is a schematic three-view drawing illustrating the configuration of a support mechanism disposed between a plurality of cooling sections in a pipe hardening apparatus according to a preferred third embodiment of the present invention. More specifically, Figure 5(a) is a plan view (top view) of the support mechanism 17, Figure 5(b) is a side view of the support mechanism 17, and Figure 5(c) is a front view of the support mechanism 17. The axis of rotation of the intermediate roller 17b constituting the support mechanism 17 illustrated in Figure 5 is parallel to the conveying direction of the pipe material 5. As a result, the pipe material 5 supported by the support mechanism 17 can rotate around its central axis while being conveyed on the conveying path. However, the configuration of the conveying mechanism or support mechanism disposed between a plurality of cooling sections in a pipe hardening apparatus according to a preferred third embodiment of the present invention is not particularly limited, as long as it is possible to perform the hardening and cooling processes by the hardening apparatus according to the present invention while preventing the pipe material from falling off the conveying path by the intermediate roller placed between adjacent cooling sections.

[0061] In order to explain the present invention, several embodiments having specific configurations have been described, sometimes with reference to the accompanying drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments, and it goes without saying that modifications can be made as appropriate within the scope of the claims and the specification.

[0062] 1, 1c Hardening apparatus 2 Conveyor path 3 Upstream conveyor path 4 Downstream conveyor path 5 Pipe material 6 Pipe material to be hardened 7 First upstream pipe material 8 Second upstream pipe material 9 Heating coil section 10 Speed ​​detection means 11 Displacement detection means 12 Cooling section 13 Roller 14 Step section 15 Hardened portion 16 Further cooling section 17 Support mechanism 17a, 17b Intermediate roller α Distance β Length of hardened area R1 Area that has been hardened R2 Area that has not been hardened R3 Slow change area R4 Area between area R1 and the end (area that is crushed)

Claims

1. A method for quenching pipes, comprising: transporting a plurality of pipes with their ends in contact with each other on a transport path at a predetermined speed; and applying current to a heating coil installed on the transport path for a predetermined period of time, starting from a predetermined time, when one of the plurality of pipes, which is the pipe to be quenched, passes over the heating coil, thereby applying heat treatment to a predetermined region, the first region, of the pipe to be quenched, wherein the upstream end of a first group of pipes, which is a group of a plurality of pipes in contact with each other substantially coaxially upstream of the pipe to be quenched, and the downstream end of a second group of pipes, which is a group of a plurality of pipes in contact with each other substantially coaxially upstream of the first group of pipes, are transported in an eccentric manner; and speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes, is detected by a speed detection means. A method for quenching pipes, characterized by detecting a step portion resulting from the eccentric state between the first group of pipes and the second group of pipes using a displacement detection means, calculating the first time point and the first period based on the velocity information obtained by the velocity detection means, a second time point which is the timing at which the step portion was detected by the displacement detection means, and a first distance which is the distance between the heating coil portion and the displacement detection means in the conveying direction of the pipes, and applying heat treatment to the first region of the pipes to be quenched.

2. A method for quenching a pipe according to claim 1, wherein the transport path includes an upstream transport path and a downstream transport path offset vertically downward with respect to the upstream transport path, and the pipe located furthest downstream of a plurality of pipes constituting the second group of pipes being transported on the upstream transport path falls onto the downstream transport path, thereby separating the pipe from the second group of pipes and joining the first group of pipes, and the stepped portion is formed at the contact point between the upstream end of the first group of pipes and the downstream end of the second group of pipes.

3. A method for quenching a pipe according to claim 1 or claim 2, characterized in that a second period is provided, which is a period over a predetermined time immediately before the start of the first period during which the intensity of the heat treatment applied to the pipe to be quenched by the heating coil is increased at a predetermined rate, and / or a third period is provided, which is a period over a predetermined time immediately after the end of the first period during which the intensity of the heat treatment applied to the pipe to be quenched by the heating coil is decreased at a predetermined rate.

4. A method for quenching a pipe material according to claim 3, characterized in that, during the second period, the current intensity supplied to the heating coil portion is increased at a predetermined rate, and during the third period, the current intensity supplied to the heating coil portion is decreased at a predetermined rate.

5. A method for quenching a pipe material according to claim 1 or claim 2, characterized in that the pipe material to be quenched, which has been subjected to the heat treatment, is cooled by a cooling unit provided in the transport path downstream of the heating coil.

6. A method for quenching a pipe material according to claim 5, characterized in that a plurality of cooling units are provided in the transport path downstream of the heating coil, and the heat-treated pipe material to be quenched is transported or supported by a transport mechanism or support mechanism arranged between adjacent cooling units.

7. A pipe hardening apparatus that transports a plurality of pipes with their ends in contact with each other on a transport path at a predetermined speed, and applies a heat treatment to a predetermined region of the pipe to be hardened by energizing a heating coil installed on the transport path for a predetermined period of time, starting from a predetermined time, when one of the plurality of pipes, which is the pipe to be hardened, passes over the heating coil, the apparatus comprising: a transport path that transports the pipes while bringing the upstream end of a first group of pipes, which is a group of a plurality of pipes in contact with each other substantially coaxially upstream of the pipe to be hardened, and the downstream end of a second group of pipes, which is a group of a plurality of pipes in contact with each other substantially coaxially upstream of the first group of pipes, in an eccentric contact state; and a speed detection means for detecting speed information, which is information correlated with the transport speed of the first group of pipes and / or the second group of pipes. A pipe hardening apparatus comprising: a displacement detection means for detecting a step portion resulting from the eccentric state of the first pipe group and the second pipe group; and a calculation means for calculating the first time point and the first period based on the velocity information obtained by the velocity detection means, a second time point which is the timing at which the step portion is detected by the displacement detection means, and a first distance which is the distance between the heating coil portion and the displacement detection means in the conveying direction of the pipe material.

8. A pipe quenching apparatus according to claim 7, wherein the transport path includes an upstream transport path and a downstream transport path offset vertically downward with respect to the upstream transport path, and the apparatus is configured such that the second group of pipes is transported on the upstream transport path, and the pipe to be quenched and the first group of pipes in contact with the upstream side of the pipe to be quenched are transported on the downstream transport path, so that the pipe located furthest downstream of the plurality of pipes constituting the second group of pipes falls onto the downstream transport path, thereby separating the pipe from the second group of pipes and joining the first group of pipes, and forming the stepped portion at the contact point between the upstream end of the first group of pipes and the downstream end of the second group of pipes.

9. A pipe quenching apparatus according to claim 7 or claim 8, characterized in that it is configured to include a second period, which is a period during which the intensity of the heat treatment applied to the pipe to be quenched by the heating coil is increased at a predetermined rate over a predetermined period immediately before the start of the first period, and / or a third period, which is a period during which the intensity of the heat treatment applied to the pipe to be quenched by the heating coil is decreased at a predetermined rate over a predetermined period immediately after the end of the first period.

10. A pipe quenching apparatus according to claim 9, characterized in that, during the second period, the current supply intensity to the heating coil is increased at a predetermined rate, and during the third period, the current supply intensity to the heating coil is decreased at a predetermined rate.

11. A pipe quenching apparatus according to claim 7 or claim 8, further comprising a cooling section provided in the transport path downstream of the heating coil section, wherein the pipe quenching apparatus that has undergone the heat treatment is cooled by the cooling section.

12. A pipe hardening apparatus according to claim 11, characterized in that a plurality of cooling units are provided in the transport path downstream of the heating coil, and the pipe to be hardened that has been subjected to the heat treatment is transported or supported by a transport mechanism or support mechanism arranged between adjacent cooling units.

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