JP2013176797A - Coil spring forming device and spring length measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil spring forming device with which a coil spring having a set spring length can be surely formed and a spring length measuring device which constitutes a part of the coil spring forming device.SOLUTION: A spring length is measured as an intermediate actually measured spring length in the middle of forming a coil spring 91 and also the feed rate of a wire rod 90 from the start of formation of the coil spring 91 to the measuring time of the intermediate actually measured spring length is measured as the intermediate feed rate of the wire rod. A portion of a difference between an intermediate reference spring length as a target spring length to the intermediate feed rate of the wire rod and the intermediate actually measured spring length is canceled during a period after the measuring time of the intermediate actually measured spring length until the feed rate of the wire rod 90 reaches a set feed rate and a pitch is changed in the middle of the formation by performing the position change of a pitch tool 14 so that the actual spring length of the whole coil spring 91 approaches the set spring length.

Description

  The present invention relates to a coil spring forming apparatus that forms a coil spring from a wire, and a spring length measuring apparatus for measuring the spring length of the coil spring.

  As this type of conventional coil spring forming apparatus, the wire rod fed from the wire rod feeding device is brought into contact with the molding tool and slidably contacted with the pitch tool to set a preset spring length, a preset coil diameter, What forms the coil spring of a setting pitch is known. In this coil spring forming apparatus, the actual spring length of the entire coil spring that has been formed (immediately before cutting) is measured, and the pitch is determined according to the error between the measured actual spring length and a preset spring length that is set in advance. It was possible to change the position of the tool and correct the pitch (see, for example, Patent Document 1).

JP-A-8-110208 (paragraph [0009])

  However, in the above-described conventional coil spring forming apparatus, the corrected pitch is applied to the coil spring that is formed next, and the error is not solved for the coil spring that is formed first. there were.

  The present invention has been made in view of the above circumstances, and includes a coil spring forming apparatus that can reliably form a coil spring having a set spring length, and a spring length measuring apparatus that constitutes a part of the coil spring forming apparatus. For the purpose of provision.

  In order to achieve the above object, a coil spring forming apparatus according to the invention of claim 1 is configured to feed a wire having a preset set feed amount from a wire feeding apparatus to collide with a forming tool and pitch. In a coil spring forming apparatus that forms a coil spring having a preset set spring length, set coil diameter, and set pitch by sliding in contact with a tool, the rotational power of the servo motor is converted into the direct acting power in the winding axis direction of the coil spring. A linear motion actuator that translates the contact to linearly and a distance between the origin position in the linear motion range of the contact and the contact position that contacts the tip of the coil spring. A rotational position sensor, a spring length measuring means for measuring a spring length in the middle of forming the coil spring based on a distance detected by the rotational position sensor as an intermediate measured spring length, The feed amount measuring means that measures the feed amount of the wire from the measurement of the intermediate measured spring length to the intermediate wire feed amount, and the target spring length for the intermediate wire feed amount are stored as the intermediate reference spring length. Intermediate reference spring length determining means for determining the target spring length for the intermediate wire supply amount from a theoretical formula as an intermediate reference spring length; The error with the intermediate actual measured spring length is canceled after the measurement of the intermediate actual measured spring length and before the wire feed amount reaches the set feed amount, and the actual spring length of the entire coil spring becomes the set spring length. And a pitch changing means for changing the position of the pitch tool so as to change the pitch of the coil spring in the middle of molding.

  The invention of claim 2 is the coil spring forming apparatus according to claim 1, wherein the intermediate wire feed amount is set to a constant value, and the wire feed amount measured by the feed amount measuring means is a constant value. The present invention is characterized in that when a certain amount of intermediate wire is fed, the feeding of the wire is stopped and the intermediate measured spring length is measured by the spring length measuring means.

  According to a third aspect of the present invention, in the coil spring forming apparatus according to the first aspect, the intermediate reference spring length determining means stores an intermediate reference in which a plurality of intermediate wire feed amounts and a plurality of intermediate reference spring lengths are stored in association with each other. A value data table is provided, and the intermediate reference spring length corresponding to the intermediate wire feed amount measured by the feed amount measuring means is selected from the intermediate reference value data table and determined. .

According to a fourth aspect of the present invention, in the coil spring forming apparatus according to the first aspect, the intermediate reference spring length determining means sets the intermediate wire rod feeding amount to L and the wire rod feeding required for the end winding portion on the tip side of the coil spring. When the amount is La, the set pitch is P, the set coil diameter is D, the wire diameter is d, the number of turns of the end winding portion is Na, and the intermediate reference spring length is H,
s = L-La
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
It is characterized in that the intermediate reference spring length H is calculated and determined from the following theoretical formula and the intermediate wire feed amount L measured by the feed amount measuring means.

A fifth aspect of the present invention is the coil spring forming apparatus according to any one of the first to fourth aspects, further comprising a pitch data table that stores the pitch of the coil spring in correspondence with the position of the pitch tool. The pitch changing means is such that the set value of the effective number of turns of the coil spring is N, the set pitch is P, the corrected pitch that is the changed pitch is p, the set coil diameter is D, the wire diameter is d, and the intermediate When the wire feed amount is L, the wire feed amount required for the end winding portion of the coil spring is La, and the value obtained by subtracting the intermediate reference spring length from the intermediate measured spring length is δ,
s = L-La
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
K = [(π · D) ² + P ² ] ^1/2
The pitch tool is moved to the position of the pitch tool determined from the corrected pitch p calculated from the following formula and the pitch data table.

  The spring length measuring device according to the invention of claim 6 is configured such that a wire rod is fed from a wire rod feeding device, abuts against a forming tool and is brought into sliding contact with a pitch tool, and a preset spring length and a preset coil diameter set in advance. In addition, the coil spring having a set pitch is formed and the spring length in the middle of forming the coil spring is measured as an intermediate actually measured spring length, and an error between the intermediate actually measured spring length and a preset target spring length is the intermediate actually measured spring length. Part of the coil spring forming device that changes the pitch of the coil spring in the middle of molding by changing the position of the pitch tool so that the actual spring length of the entire coil spring approaches the set spring length after cancellation of the length. Is a linear motion actuator that measures the intermediate measured spring length and converts the rotational power of the servo motor to the linear motion power in the winding axis direction of the coil spring to linearly move the contact The The distance between the origin position in the linear movement range of the contact and the contact position that contacts the tip of the coil spring is detected by the rotational position sensor provided in the servo motor, and an intermediate measurement is performed based on the detected distance. It is characterized in that it is configured to measure the spring length.

[Invention of claims 1, 3-6]
According to the coil spring forming apparatus according to the first aspect of the present invention and the coil spring forming apparatus including the spring length measuring apparatus according to the sixth aspect of the invention as a part, the spring length is measured in the middle during the forming of the coil spring. Measured as the spring length, and measured the wire feed amount from the start of coil spring molding to the measurement of the intermediate measured spring length as the intermediate wire feed amount, and is the target spring length for the intermediate wire feed amount The error between the reference spring length and the intermediate measured spring length is canceled after the measurement of the intermediate measured spring length and before the wire feed amount reaches the set feed amount. The position of the pitch tool is changed so that the length approaches the set spring length, and the pitch is changed during molding.

  Specifically, if the actual pitch of the molded part until the measurement of the intermediate measured spring length is larger than the design pitch, and the intermediate measured spring length exceeds the intermediate reference spring length, it continues to the molded part. By narrowing the pitch of the subsequent portion, the error generated in the molded portion is canceled, and the actual spring length of the entire coil spring approaches the set spring length. Conversely, if the actual pitch of the molded part until the measurement of the intermediate measured spring length is smaller than the design pitch, and the intermediate measured spring length has not reached the intermediate reference spring length, the succeeding part that is continuous with the molded part By expanding the pitch of the portion, the error generated in the molded portion is canceled so that the actual spring length of the entire coil spring approaches the set spring length.

  That is, according to the present invention, the pitch is changed by detecting an error of the spring length generated during the molding of the coil spring, and the subsequent pitch is formed by continuing the changed pitch to the molded part of the coil spring during the molding. Since it is sometimes applied, the error of the spring length generated during the molding can be eliminated until the molding of the coil spring is completed. This makes it possible to reliably form a coil spring having a set spring length.

  Further, according to the present invention, the contact is brought into contact with the tip of the coil spring and the intermediate measured spring length of the coil spring is measured. For example, the capacitance sensor is arranged away from the tip of the coil spring, The degree of freedom of the installation location of the coil spring forming apparatus can be increased as compared with the case where the spring length is measured based on the capacitance between them. In detail, it is said that the capacitance is easily affected by temperature, an object close to the capacitance sensor, etc., and it is difficult to install the coil spring forming apparatus in a place where these disturbances cannot be excluded. It is. On the other hand, according to this invention, since it is not influenced by these disturbances, the freedom degree of the installation place of a coil spring shaping | molding apparatus can be raised.

  Here, the intermediate reference spring length determining means for determining the intermediate reference spring length may be determined from the intermediate wire feed amount by storing the target spring length for the intermediate wire feed amount as the intermediate reference spring length, The target spring length with respect to the intermediate wire feed amount may be determined by calculating from the theoretical formula as the intermediate reference spring length.

  Specifically, for example, as in the invention of claim 3, the intermediate reference spring length determining means stores an intermediate reference value data table in which a plurality of intermediate wire feed amounts and a plurality of intermediate reference spring lengths are stored in association with each other. The intermediate reference spring length may be determined from the intermediate wire feed amount measured by the feed amount measuring means.

Alternatively, for example, as in the invention of claim 4, the intermediate reference spring length determining means sets the intermediate wire rod feed amount as L and the wire rod feed amount required for the end winding portion of the coil spring as La. When the pitch is P, the set coil diameter is D, the wire diameter is d, the number of turns of the end winding part is Na, and the intermediate reference spring length is H,
s = L-La
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
The intermediate reference spring length H may be calculated and determined from the following theoretical formula and the intermediate wire feed amount L measured by the feed amount measuring means.

Further, as in the invention of claim 5, a pitch data table in which the pitch of the coil spring is associated with the position of the pitch tool is provided, and the pitch changing means sets the effective winding number of the coil spring to N The set pitch is P, the corrected pitch that is the changed pitch is p, the set coil diameter is D, the wire diameter is d, the intermediate wire feed amount is L, and the end winding of the coil spring When the wire feed amount required for the part is La and the value obtained by subtracting the intermediate reference spring length from the intermediate measured spring length is δ,
s = L-La
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
K = [(π · D) ² + P ² ] ^1/2
The pitch tool may be moved to the position of the pitch tool determined from the corrected pitch p calculated from the following formula and the pitch data table.

[Invention of claim 2]
According to the invention of claim 2, when the wire feed amount measured by the feed amount measuring means coincides with the intermediate wire feed amount which is a preset constant value, the wire feed is stopped. Since the spring length of the coil spring is measured as the intermediate measured spring length when the coil spring molding is temporarily suspended, the intermediate measured spring length can be measured while the coil spring is stationary. Thus, the intermediate measured spring length can be measured more accurately.

Front view of coil spring forming device Side view of coil spring forming device The perspective view which expanded the forming field of the coil spring forming device Side sectional view of coil spring forming device Conceptual diagram showing the control configuration of the coil spring forming device Conceptual diagram showing the process of forming a coil spring Spring forming program flowchart Conceptual diagram of pitch data table (A) Side view of coil spring having theoretical spring length, (B) Side view of coil spring in the middle of molding having theoretical intermediate spring length Side view showing the target coil spring compared to the actual coil spring in the middle of molding Conceptual diagram of intermediate reference value data table The perspective view which expanded the forming field of the coil spring forming device concerning a modification

[First Embodiment]
Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. A coil spring forming apparatus 10 shown in FIG. 1 includes a wire rod feeding device 50, a pair of vertical linear motion mechanisms 30, 36, a pair of inclined linear motion mechanisms 40, 40, etc. Assembled. The wire rod feeding device 50 includes a pair of feed rollers 51 and 52 arranged on the front surface of the base 11 and arranged vertically. A wire guide 12 (generally referred to as “quill”) is extended to one side in the horizontal direction (the right side in FIG. 1) from the joint between the feed rollers 51 and 52 in the wire feeding device 50, In the wire guide 12, a wire insertion hole (not shown) is formed through the tangent line common to both the feed rollers 51 and 52. Then, the wire rod 90 is sandwiched between the feed rollers 51 and 52, and the feed roller 51 and 52 are rotated symmetrically by using the feeding servo motor 54 (see FIG. 4) as a drive source. Is fed to the right side and is fed from the tip of the wire guide 12.

  In order to pivotally support the feed rollers 51 and 52, a pair of opposed support walls 11A and 11B constituting the base 11 as shown in FIG. Roller support shafts 51S and 52S are passed. Of the roller support shafts 51S and 52S, feed rollers 51 and 52 are respectively attached to the front end portions of the roller support shafts 51S and 52S that pass through the front support wall 11A so as to be integrally rotatable, and are sandwiched between the counter support walls 11A and 11B. Gears 51G and 52G are attached to the portions so as to be integrally rotatable. And the feed rollers 51 and 52 rotate symmetrically by mesh | engagement of these gears 51G and 52G.

  Below the gear 52G, an idle gear 53 is rotatably supported on the rear opposing support wall 11B, and the gear 52G meshes with the idle gear 53. A feeding servo motor 54 is provided below the idle gear 53. A drive gear 56 is attached to a rotation output shaft of the feeding servo motor 54 via a speed reducer 55. The drive gear 56 is engaged with the idle gear 53. Thus, the feed rollers 51 and 52 can be rotationally driven symmetrically by the feeding servo motor 54. Here, the feeding servo motor 54 is provided with an encoder 54E that detects the current rotational position, and the feeding amount of the wire 90 can be controlled based on the output of the encoder 54E. The feeding servo motor 54 may include a resolver instead of the encoder 54E.

  As shown in FIG. 1, a mandrel 13 protrudes from the front surface (opposing support wall 11A) of the base 11 in front of the wire guide 12 in the wire feeding direction. As shown in FIG. 3, the mandrel 13 has a bar shape with a semicircular cross section, and the flat side surface 13 </ b> A faces the wire guide 12 side.

  As shown in FIG. 1, the pair of inclined linear motion mechanisms 40, 40 are attached to extension plates 41, 41 fixed to the front surface of the base 11 (opposing support wall 11 </ b> A). Then, one inclined linear motion mechanism 40 extends from the mandrel 13 toward the diagonally upward vertical side opposite to the wire feeding device 50, and the other inclined linear motion mechanism 40 is below the one inclined linear motion mechanism 40. It is arrange | positioned and it extends in the diagonally upward horizontal direction as it leaves | separates from the mandrel 13. Each inclined linear motion mechanism 40 is provided with a slider 43 that linearly moves in the direction in which they extend. One end portion of the link member 42 is rotatably connected to the end portion of the slider 43 away from the mandrel 13, and the other end portion of the link member 42 rotates around the eccentric shaft 45 </ b> J of the rotating disk 45. It is linked movably. The rotating disk 45 is pivotally supported with respect to the additional plate 41, and an eccentric shaft 45J is disposed at a position eccentric from the center of rotation. Then, the rotary disk 45 is rotationally driven by the vertical movement servomotor 46 attached to the back surface side of the additional plate 41, and thereby the slider 43 moves linearly.

  A tool attachment 43A is attached to the mandrel 13 side of the slider 43 of each inclined linear motion mechanism 40, and a coiling tool 16 (corresponding to the “forming tool” of the present invention) is respectively attached to the tool attachment 43A. It is fixed. As shown in FIG. 3, the coiling tool 16 provided in one inclined linear motion mechanism 40 is abutted against the mandrel 13 from obliquely above, and the coiling tool 16 provided in the other inclined linear motion mechanism 40 is It is abutted against the gold 13 obliquely from below. Further, a round groove 16 </ b> M is formed on the tip surface of the coiling tool 16. Then, the wire rod 90 fed from the wire rod feeding device 50 is guided to the circular groove 16M of each coiling tool 16, and the wire rod 90 is formed into an arc shape so as to surround the mandrel 13 to become a coil spring 91. As shown in FIG. 2, the coil spring 91 grows away from the base 11.

  As shown in FIGS. 1 and 2, the vertical movement mechanisms 30 and 36 are arranged symmetrically vertically with the mandrel 13 interposed therebetween. The upper vertical translation mechanism 30 includes a slider 31 similar to the slider 43 of the tilt translation mechanism 40, and the slider 31 is connected to the eccentric shaft 34 </ b> J of the rotating disk 34 via the link member 32. Yes. Then, the rotary disk 34 is rotationally driven by the servo motor 35 so that the slider 31 moves directly.

  A tool mounting bracket 31A is fixed to the slider 31 in the upper vertical translation mechanism 30, and a cutting tool 15 is fixed to the tool mounting bracket 31A. The cutting tool 15 has a prismatic shape and extends vertically downward from the tool mounting bracket 31A. When the cutting tool 15 is lowered, it rubs adjacent to the flat side surface 13 </ b> A of the mandrel 13, and the wire 90 is cut between the edge of the cutting tool 15 and the edge of the mandrel 13.

  The lower vertical linear motion mechanism 36 is formed by connecting an output shaft of a servo motor 39 to a shaft of a ball screw mechanism 37 via a shaft coupling 39J. A tool mounting bracket 38A is fixed to the slider 38 of the ball screw mechanism 37, and the pitch tool 14 is fixed to the tool mounting bracket 38A. The pitch tool 14 has a prismatic shape and extends vertically upward from the tool mounting bracket 38A. As shown in FIG. 3, the tip of the pitch tool 14 has a wedge shape, and an inclined surface 14A inclined with respect to the vertical direction is provided on the opposite side of the base 11 from the tip, and this inclined surface 14A. Is in contact with the wire 90 constituting the coil spring 91 from the base 11 side in the winding axis direction. Then, by moving the pitch tool 14 upward, the wire 90 constituting the coil spring 91 can be pushed away from the base 11 to increase the pitch and the spring length of the coil spring 91.

  As shown in FIG. 2, a spring length detection unit 20 is provided at a position offset downward from the coaxial extension line of the mandrel 13. The spring length detection unit 20 is attached to the tip of a cantilevered support arm 17 protruding from the front surface of the base 11. The spring length detection unit 20 includes a linear actuator 25 formed by connecting an output shaft of a contact servomotor 21 to a shaft of a ball screw mechanism 22 via a shaft coupling 21J. A contact 24 is attached to the tip of the extension shaft 23S extending in the linear motion direction. The contactor 24 has a disk shape having substantially the same diameter as the coil diameter of the coil spring 91. The slider 23 can be moved linearly in the winding axis direction (growth direction) of the coil spring 91 by the power of the contact servomotor 21, and the contactor 24 can be brought into contact with and separated from the tip of the coil spring 91. It has become. The contact servomotor 21 is provided with, for example, an encoder 21E (corresponding to the “rotational position sensor” of the present invention), and the origin position of the linear movement range of the contact 24 based on the output of the encoder 21E. The moving distance from can be detected. The encoder 21E corresponds to the “rotational position sensor” of the present invention, but the “rotational position sensor” may be a resolver.

  The coil spring 91 being molded is body-grounded by the coil spring molding apparatus 10, and when the contact 24 comes into contact with the coil spring 91, the contact 24 is grounded via the coil spring 91. At this time, the spring length detection unit 20 outputs a detection signal. The detection signal is taken into the CPU 61 of the control device 60 described below via the interface circuit 20A as shown in FIG. 5, and the CPU 61 outputs the output value of the encoder 21E when the detection signal is input, that is, the contact 24. The spring length of the coil spring 91 is calculated based on the moving distance until the tip contacts the tip of the coil spring 91. The control circuit 60C corresponds to the “spring length measuring means” of the present invention, and the control device 60 and the spring length detector 20 constitute the “spring length measuring device” of the present invention.

  FIG. 5 shows a control device 60 for controlling the coil spring forming device 10. The control circuit 60C of the control device 60 includes a CPU 61, a ROM 62, a RAM 63, and a flash memory 64. An NC program is stored in the flash memory 64, and the CPU 61 executes the NC program based on the specifications of the coil spring 91 input in advance (setting values such as pitch, coil diameter, number of turns, spring length, wire diameter, etc.). As a result, the wire rod feeding device 50, the vertical linear motion mechanisms 30, 36, the inclined linear motion mechanisms 40, 40, and the like are driven, and the coil spring 91 is formed from the wire rod 90. The control circuit 60C measures the feeding amount of the wire 90 based on the output value of the encoder 54E provided in the feeding servomotor 54. Further, as described above, the spring length of the coil spring 91 formed from the wire 90 is measured based on the output value of the encoder 21E provided in the contact servomotor 21. The encoder 54E and the control circuit 60C correspond to the “feed amount measuring means” of the present invention.

  Here, the spring forming operation of the coil spring forming apparatus 10 will be described. The wire feeding device 50 feeds a wire 90 having a preset set feeding amount every time to form one coil spring 91, and the coil spring forming device 10 feeds the wire 90 having the set feeding amount. From this, a coil spring 91 having a preset spring length, a preset coil diameter, and a preset pitch is formed. The coil spring 91 formed by the coil spring forming apparatus 10 of the present embodiment is a closed end coil spring, and has end windings 91A and 91C at both ends of a coil body 91B that acts as a spring. (See FIG. 9A).

  The spring forming operation starts from the initial state shown in FIG. 6 (A). As shown in FIG. 6 (B), when the pitch tool 14 is arranged at the end winding forming position slightly raised from the initial position, the state is shown. Then, the wire rod feeding device 50 feeds the wire rod 90 for a predetermined length. Then, the wire rod 90 abuts on the coiling tools 16 and 16 and is slidably contacted with the pitch tool 14, and the end winding 91 </ b> A (hereinafter referred to as appropriate) having a preset number of turns (1 turn in this embodiment). (Referred to as “tip end turn 91A”).

  When the end end turn 91A has been formed, as shown in FIG. 6C, the pitch tool 14 rises to a pitch forming position corresponding to the set pitch, and in this state, the wire feeding device 50 has a predetermined length of wire. 90 is sent. Then, the wire rod that has passed through the coiling tools 16 and 16 is brought into sliding contact with the pitch tool 14 to form a coil body 91B having a preset number of turns (effective number of turns) and a pitch for each turn (FIG. 6). (C) to FIG.

  When the forming of the coil body 91B is completed, as shown in FIG. 6G, the pitch tool 14 is lowered from the pitch forming position to the end winding forming position, and in this state, the wire rod feeding device 50 has a predetermined length of the wire rod 90. To send. Then, a rear end end turn 91C (hereinafter, referred to as “rear end end turn 91C” as appropriate) having a predetermined number of turns (1 turn in the present embodiment) is formed.

  Next, as shown in FIG. 6H, the cutting tool 15 descends from the initial position, and the coil spring 91 is separated from the subsequent wire 90 by the cutting tool 15 and the mandrel 13. When the coil spring 91 is cut off, the pitch tool 14 and the cutting tool 15 are returned to the initial state (the state shown in FIG. 6A) in which the pitch tool 14 and the cutting tool 15 are arranged at the initial position, and the molding of the next coil spring 91 is started.

  Now, the coil spring forming apparatus 10 of the present embodiment measures the spring length during the forming of the coil spring 91 in order to ensure that the spring length of the completed coil spring 91 as a whole is a preset spring length that is set in advance. If there is an error in the spring length, it is possible to cancel the error and bring it closer to the set spring length before the coil spring is completed.

  Here, since the end windings 91A and 91C in the closed-end coil spring 91 are tightly wound without leaving a gap, the length of the end windings 91A and 91C can be considered to be constant every time. Therefore, the error in the spring length is caused by the error in the length of the coil body 91B, and the error in the length of the coil body 91B is mainly caused by the error in the pitch of the coil body 91B. Therefore, in the coil spring forming apparatus 10 of the present embodiment, the spring length of the coil spring 91 is measured as “intermediate measured spring length” during the formation of the coil body 91B, and the “intermediate reference spring length” and “intermediate spring length” stored in advance are measured. The position of the pitch tool 14 is changed according to the error from the “actually measured spring length”, and the pitch of the coil body 91B is changed during the molding. Then, when the subsequent portion that is continuous with the molded portion of the coil spring 91 in the middle of molding is molded, the changed pitch is immediately applied. As a result, the error of the spring length is canceled until the feeding amount of the wire 90 reaches the preset feeding amount of one coil spring and the coil spring 91 is completed. The actual spring length of the entire spring 91 can be brought close to the set spring length.

  More specifically, when the CPU 61 of the control circuit 60C executes the NC program, input of the specification value (setting value) of the coil spring 91 is required. When the input of the specification value is completed, next, the coil spring forming device 10 is formed with one coil spring 91 as a master sample based on the specification value, and the actual spring length of the master sample is set to “intermediate”. It is stored as “reference spring length” and “set spring length”.

  Specifically, when the feeding amount of the wire 90 from the start of forming the coil spring 91 as a master sample matches the preset intermediate wire feeding amount, the feeding of the wire 90 is temporarily stopped, and the coil The forming of the spring 91 is temporarily stopped. In this state, the contact 24 of the spring length detection unit 20 is advanced toward the coil spring 91 serving as a master sample to contact the tip of the coil spring 91. Then, the moving distance from the origin position of the contactor 24 to the contact position with the coil spring 91 is detected from the encoder 21E provided in the contactor servomotor 21, and the master sample in the middle of molding is detected from the detected moving distance. The actual spring length is measured and stored in the RAM 63 as an “intermediate reference spring length” which is a target spring length for the intermediate wire feed amount. Further, when the feeding amount of the wire 90 reaches the set feeding amount for one coil spring, that is, before the molding of the coil spring 91 as a master sample is completed and separated from the subsequent wire 90, the master The actual spring length of the entire coil spring 91 as a sample is measured, and this is stored in the RAM 63 as a “set spring length” that is the target spring length of the entire coil spring 91. That is, the coil spring 91 as a product is molded with the coil spring 91 actually molded as a master sample as a target. The intermediate reference spring length need not be one, and the actual spring length may be measured at a plurality of intermediate wire feed amounts, and each of the plurality of spring lengths may be stored as the intermediate reference spring length.

  When the storage of the intermediate reference spring length and the set spring length by forming the master sample is completed, the normal spring forming program PG1 is executed, and the coil spring 91 as a product is formed. In the normal spring forming program PG1, the same spring forming and spring length measurement as in the master sample are performed. The difference from the molding of the master sample is that the pitch can be changed during the molding of the coil spring 91.

  As shown in FIG. 7, in the spring forming program PG1, first, it is determined whether or not the feeding amount of the wire 90 from the forming start measured based on the output of the encoder 54E exceeds a preset measurement operation starting amount. It is determined (S11). Specifically, for example, it is determined whether or not the feeding amount of the wire 90 exceeds a feeding amount corresponding to a predetermined number of turns in the coil spring 91 (for example, up to the second turn of the coil body 91B).

  When the measurement operation start amount is exceeded (YES in S11), the movement of the contact 24 provided in the spring length detection unit 20 (advance to the tip of the coil spring 91) is started (S12). On the other hand, when the measurement operation start amount is not exceeded (NO in S11), the process of step S11 is repeated while the contactor 24 is stopped at the origin position.

  Next, when the feeding amount of the wire 90 from the start of molding coincides with the preset intermediate wire feeding amount (in this embodiment, for example, the feeding amount corresponding to the third volume of the coil body 91B), the feeding is performed. The feeding servo motor 54 is stopped and the feeding of the wire 90 is stopped (S13). As a result, the molding of the coil spring 91 is temporarily stopped, and the coil spring 91 is in a stationary state (the state shown in FIG. 6D). Here, the time required for forming one coil spring 91 is shortened by starting the movement of the contactor 24 before the feeding of the wire 90 (forming the coil spring 91) is temporarily stopped (S12). It becomes possible to do.

  Even after the formation of the coil spring 91 is temporarily stopped, the contactor 24 continues to advance toward the coil spring 91. If it is detected that the contact 24 has contacted the tip of the coil spring 91 (YES in S14), the output value of the encoder 21E at the time of contact is stored (S15).

  When the contact 24 comes into contact with the tip of the coil spring 91, the contact servomotor 21 immediately stops and reversely rotates, as shown by the dotted line in FIG. 6D, from the tip of the coil spring 91. The contactor 24 is retracted so as to leave (S16).

  Next, the pitch required to bring the actual spring length of the entire coil spring 91 when the coil spring 91 in the middle of molding is close to the set spring length (the total spring length of the master sample) is calculated (S17). Specifically, based on the output value of the encoder 21E stored in step S15, the moving distance from the origin position of the contactor 24 is detected, and the coil spring that is temporarily stopped during the molding based on the moving distance. The actual spring length of 91 is measured. As shown in FIG. 6D, the actual spring length is obtained by subtracting the moving distance Y of the contact 24 from the known distance X between the cutting position by the cutting tool 15 and the origin position of the contact 24. Good.

  Further, the intermediate reference spring length corresponding to the intermediate wire feed amount is read from the RAM 63 and determined from the intermediate wire feed amount that is the feed amount of the wire 90 when the contact 24 contacts the coil spring 91. The error between the intermediate reference spring length and the intermediate measured spring length is calculated. If the error is within the allowable range, the pitch until then is maintained. If the error exceeds the allowable range, the error is canceled until the coil spring is completed, and the entire coil spring 91 is The pitch required to bring the actual spring length closer to the set spring length is calculated. The control circuit 60C including the RAM 63 that stores the intermediate reference spring length and the CPU 61 that executes the process (S17) for determining the intermediate reference spring length from the intermediate wire feed amount is the “intermediate reference spring length” of the present invention. This corresponds to “determination means”.

  When it is necessary to change the pitch, the pitch tool 14 is moved to a position corresponding to the changed pitch (hereinafter referred to as “corrected pitch” as appropriate) (S18). The control circuit 60C including the CPU 61 that executes the processes of steps S17 and S18 corresponds to the “pitch changing means” of the present invention.

  Here, the position of the pitch tool 14 is determined from the pitch data table DT1 stored in the RAM 63 of the control circuit 60C. As shown in FIG. 8, the pitch data table DT1 stores the position of the pitch tool 14 in association with the pitch applied to the coil spring 91 at that position. From the pitch data table DT1, The position of the pitch tool 14 corresponding to the corrected pitch is determined.

  When the pitch tool 14 moves to the determined position, the feeding of the wire 90 is resumed (S19). As a result, the subsequent portion is formed continuously with the formed portion of the coil spring 91, and a correction pitch is given to the coil body 91B of the subsequent portion.

  Here, in this embodiment, as shown in FIG. 6 (F), before the formation of the coil body 91B of the coil spring 91 is completed and the formation of the rear end end turn 91C is started, the spring length detector 20 to measure the actual spring length.

  Further, as shown in FIG. 6G, before the coil spring 91 is formed up to the rear end end turn 91C and separated from the subsequent wire rod 90, the actual spring length is measured by the spring length detection unit 20. This measurement is for finally confirming whether or not the actual spring length of the entire coil spring 91 matches the set spring length (matches if within the predetermined tolerance range).

  As described above, since the length of the rear end end turn 91C can be considered to be constant every time, for example, as shown in FIG. 6F, the formation of the coil body 91B is completed and the rear end If it is found from the spring length measured before starting the formation of the end turn 91C that the actual spring length of the entire coil spring 91 does not match the set spring length, the rear end end turn 91C is omitted. And you may make it cut | disconnect from the wire 90 immediately. Thereby, the loss of the wire 90 can be suppressed.

  In the present embodiment, the pitch can be changed only once during the molding of one coil spring 91, but a plurality of intermediate reference spring lengths corresponding to a plurality of intermediate wire feed amounts are stored in the RAM 63. In addition, the configuration may be such that the actual spring length (intermediate measured spring length) is measured a plurality of times during the molding of one coil spring 91, and the pitch can be changed each time.

  As described above, the coil spring forming apparatus 10 according to the present embodiment measures the spring length as the intermediate actually measured spring length during the formation of the coil spring 91 and from the start of forming the coil spring 91 to the time of measuring the intermediate actually measured spring length. The feed amount of the wire 90 is measured as the intermediate wire feed amount. The error between the intermediate reference spring length as the target spring length with respect to the intermediate wire feed amount and the intermediate actually measured spring length is equal to or less than the time when the intermediate actually measured spring length is measured. The pitch tool 14 is repositioned so that the actual spring length of the entire coil spring 91 approaches the set spring length, and the pitch is changed during molding.

  Specifically, in the coil spring 91, when the actual pitch of the molded part until the measurement of the intermediate actual measurement spring length is larger than the design pitch, and the intermediate actual measurement spring length exceeds the intermediate reference spring length, By narrowing the pitch of the subsequent part that is continuous with the molded part, the error generated in the molded part is canceled, and the actual spring length of the entire coil spring 91 approaches the set spring length. On the contrary, in the coil spring 91, when the actual pitch of the molded part until the measurement of the intermediate actual measured spring length is smaller than the design pitch, the intermediate actual measured spring length has not reached the intermediate reference spring length. By expanding the pitch of the subsequent portion that is continuous with the completed portion, the error generated in the formed portion is canceled, and the actual spring length of the entire coil spring 91 approaches the set spring length.

  That is, the pitch is changed in accordance with the error of the spring length generated during the molding of the coil spring 91, and the changed pitch is immediately applied at the time of molding the subsequent portion continuous with the molded portion of the coil spring 91 during the molding. As a result, the error in the spring length generated during the molding can be eliminated before the molding of the coil spring 91 is completed. This makes it possible to reliably mold the coil spring 91 having a set spring length.

  Further, according to the present embodiment, the contact 24 is linearly moved from the origin position toward the coil spring 91, and the coil spring 91 is based on the moving distance from the origin position to the contact position with the tip of the coil spring 91. For example, a conventional coil spring in which a capacitance sensor is arranged away from the tip of the coil spring and the spring length is measured based on the capacitance between them. Compared to the molding apparatus, the degree of freedom of installation location can be increased. Specifically, it is said that the capacitance is easily affected by temperature, an object close to the capacitance sensor, and the like, and it is difficult to install the capacitance in a place where these disturbances cannot be excluded. On the other hand, since the spring length detection unit 20 provided in the coil spring forming apparatus 10 of the present embodiment is not affected by the disturbance, the degree of freedom of the installation location of the coil spring forming apparatus 10 is greater than that of the conventional one. Can be increased.

  Furthermore, according to the present embodiment, the feeding of the wire rod 90 is temporarily stopped, and the spring length is measured by bringing the contactor 24 into contact with the coil spring 91 in a state where the forming of the coil spring 91 is temporarily stopped. Thus, the intermediate actually measured spring length can be measured in a state where the coil spring 91 is stationary, and the intermediate actually measured spring length can be measured more accurately.

  In addition, the contactor 24 starts to advance toward the coil spring 91 while the coil spring 91 is being formed (before the feeding of the wire 90 is temporarily stopped). Compared with the case where the contactor 24 is started to advance after the forming is temporarily stopped, the time required to form one coil spring 91 can be shortened.

[Second Embodiment]
In the first embodiment, the actual spring length of the coil spring 91 as a master sample actually formed by the coil spring forming apparatus 10 is stored as the intermediate reference spring length and the set spring length. Then, the intermediate reference spring length to be compared is determined from the intermediate wire feed amount when the intermediate actually measured spring length is measured, and an error between the intermediate reference spring length and the intermediate actually measured spring length is detected.

  On the other hand, in the present embodiment, the CPU 61 provided in the control circuit 60C uses the preset specification value (design value) and the theoretical formula in the process of step S17 in the spring forming program PG1 (see FIG. 7). The difference from the first embodiment is that the “intermediate reference spring length” and the “set spring length” are calculated and determined. Other configurations are the same as those in the first embodiment, and thus redundant description is omitted.

Specifically, the setting value of the effective number of turns (the number of turns of the coil body 91B) in the coil spring 91 shown in FIG. 9A is set to N, the set number of turns of the front end turn 91A is set to Na, and the setting of the rear end end turn 91C is set. When the number of turns is Nc, the set pitch in the coil body 91B is P, the wire diameter is d, and the theoretical spring length of the entire coil spring 91 is Ht,
Ht = N · P + (Na + Nc + 1) · d
The theoretical spring length Ht of the entire coil spring 91 calculated by substituting the specification values into the theoretical formula is as the set spring length.

Further, the feeding amount from the start of forming the coil spring 91 is L, the wire feed amount required for the tip end turn 91A is La, the set pitch is P, the set coil diameter is D, and the end end turn 91A is set. When the number of turns is Na, the wire diameter is d, and the theoretical intermediate spring length including the tip end turn 91A when the feed amount is L is H,
s = L-La
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
The theoretical intermediate spring length H calculated by substituting the specification value and the feed amount L as the intermediate wire feed amount measured based on the output of the encoder 54E into the theoretical formula becomes It is set as the reference intermediate spring length for the supply amount L. Also according to this embodiment, the same effect as the first embodiment can be obtained, and the coil spring 91 matched with the theoretical spring length Ht can be formed.

Hereinafter, the reason why the above theoretical formula is established will be described with reference to FIG. A coil spring 91 shown in FIG. 9 (B) is a coil spring 91 in the middle of molding having a theoretical intermediate spring length H when the feeding amount of the wire 90 from the start of molding is L. When the number of turns of the coil body 91B when the feeding amount of the wire 90 is L is n, the following formula is established for the theoretical intermediate spring length H.
H = n · P + Na · d + d / 2

When the wire rod length required for forming the coil body 91B when the wire rod 90 feed amount is L is s, the wire rod feed amount required for the tip end turn 91A is La, and the following equation is established.
s = L-La
Further, if the wire length per turn of the coil body 91B is K,
n = s / K
Therefore, the following equation is established for the theoretical intermediate spring length H.
H = P · s / K + Na · d + d / 2

Furthermore, regarding the wire length K per winding of the coil body 91B,
K = [(π · D) ² + P ² ] ^1/2
Since the well-known theoretical formula is established,
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
s = L-La
The theoretical formula is established.

[Third Embodiment]
In this embodiment, in the coil spring forming apparatus 10 of the second embodiment, the CPU 61 provided in the control circuit 60C has a correction pitch for bringing the actual spring length of the entire coil spring 91 close to the theoretical spring length Ht. These are determined by the calculation described below.

That is, the set value of the effective number of turns of the coil spring 91 is N, the set pitch is P, the set coil diameter is D, the wire diameter is d, the intermediate wire feed amount is L, and the end end winding of the coil spring 91 is If the wire feed amount required for 91A is La, the value obtained by subtracting the intermediate reference spring length from the intermediate actual measured spring length is δ, and the correction pitch is p, the CPU 61 in the spring forming program PG1 (see FIG. 7) In the process of step S17,
s = L-La
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
K = [(π · D) ² + P ² ] ^1/2
The correction pitch p is determined from the following equation.

  The reason why the above formula is established will be described with reference to FIG. In addition, the coil spring shown with the dashed-two dotted line in the same figure is a "target coil spring" whose whole spring length is the theoretical spring length Ht, The coil spring shown with the oblique line is This is the “actual coil spring” when the wire 90 is fed to the intermediate wire feed amount L. Moreover, the symbol Q is an intermediate actually measured spring length of the actual coil spring. In FIG. 10, for the convenience of explanation, the error of the spring length between the target coil spring and the actual coil spring is emphasized more than actual.

The length obtained by subtracting the intermediate length m of the actual coil body 91B when the wire 90 is fed from the total length M of the coil body 91B of the target coil spring 91 to the intermediate wire feed amount L is defined as ΔM. The number of turns obtained by subtracting the actual number of turns n of the coil body 91B from the set value N of the effective number of turns of the body 91B up to the intermediate wire feed amount L is ΔN, and the per turn of the coil body 91B In order that the wire length of the coil spring 91 is K and the actual spring length of the entire coil spring 91 is the target coil spring length (set spring length Ht), the corrected pitch to be applied to the unformed portion of the actual coil body 91B Is p,
p = ΔM / ΔN = (M−m) / (N−n)
M = N ・ P
m = n · P + δ
n = s / K
The above relational expression is established, and when these four relational expressions are summarized, as described above,
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
It becomes.

  Then, the pitch tool 14 is moved to the position of the pitch tool 14 determined from the corrected pitch p determined from the above formula and the pitch data table DT1 (see FIG. 8), and the subsequent portion of the coil spring 91 in the middle of forming. Molding is performed while applying a correction pitch p to the. Also according to the present embodiment, the same effects as those of the first and second embodiments can be obtained.

[Fourth Embodiment]
In the first embodiment, the intermediate measured spring length of the coil spring 91 in the middle of forming is measured in a state where the feeding of the wire 90 (forming of the coil spring 91) is temporarily stopped. The intermediate measured spring length may be measured in a state where the forming of the coil spring 91 is continued.

  Specifically, for example, if the contactor 24 is moved forward toward the coil spring 91 in a state where the feeding of the wire 90 (formation of the coil spring 91) is continued and the tip of the coil spring 91 is contacted, the molding is hindered. Therefore, the contactor 24 is retracted faster than the growth rate of the coil spring 91. Further, based on the output value of the encoder 54E of the feeding servo motor 54 when the contact 24 contacts the coil spring 91 and the output value of the encoder 21E of the contact servo motor 21, an intermediate actual measurement of the coil spring 91 is performed. The spring length and the intermediate wire feeding amount of the wire 90 when the intermediate measured spring length is measured are measured.

Next, the intermediate wire feed amount is L, the wire feed amount required for the tip end turn 91A of the coil spring 91 is La, the set pitch is P, the set coil diameter is D, the wire diameter is d, the tip When the set number of turns of the end turn 91A is Na and the intermediate reference spring length is H,
s = L-La
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
The intermediate reference spring length H is calculated and determined from the theoretical formula to be obtained and the intermediate wire feed amount L measured when the contactor 24 comes into contact with the coil spring 91.

  Alternatively, the intermediate reference value data table DT2 (see FIG. 11) in which a plurality of intermediate wire feed amounts and a plurality of intermediate reference spring lengths are stored in association with each other is stored in the control circuit 60C ("intermediate reference spring length determining means" of the present invention). The intermediate reference spring length H corresponding to the intermediate wire feed amount L measured at the time of contact between the contactor 24 and the coil spring 91 is selected from the intermediate reference value data table DT2. To decide.

The error between the intermediate reference spring length H determined by any one of the above means and the intermediate measured spring length measured when the contactor 24 and the coil spring 91 are in contact with each other means that the feed amount of the wire 90 is the coil spring. The position of the pitch tool 14 is moved so that the actual spring length of the coil spring 91 as a whole approaches the set spring length, canceled until the set feed amount for one piece is reached. Specifically, for example, as in the third embodiment,
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
The pitch tool 14 is moved to a position determined from the corrected pitch p calculated from the above equation and the pitch data table DT1 (see FIG. 8).

  With such a configuration, the same effect as that of the first embodiment can be obtained, and the time required for forming one coil spring 91 can be further shortened. The feeding speed of the wire 90 may be constant during the molding of the coil body 91B, or the molding is continued by reducing the feeding speed before the contactor 24 and the coil spring 91 come into contact with each other. After returning to the origin position after contact with the spring 91, the original feeding speed may be restored. Also according to the present embodiment, the same effects as those of the first embodiment can be obtained.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) In the above embodiment, the pitch tool 14 is disposed on the opposite side of the cutting tool 15 with the mandrel 13 interposed therebetween, but as shown in FIG. 12, the opposite side of the coiling tool 16 with the mandrel 13 interposed therebetween. Alternatively, the pitch tool 14 may be disposed on the metal core 13 and the pitch tool 14 may be abutted against the mandrel 13 from above.

  (2) In the above embodiment, the contactor 24 is configured to linearly move in the winding axis direction of the coil spring 91. However, the contactor 24 is linearly moved in a direction oblique to the winding axis. Also good.

  (3) In the above embodiment, the case where the closed end coil spring 91 is formed by the coil spring forming apparatus 10 is illustrated, but even when an open end coil spring having no end winding is formed, it is equivalent to the above embodiment. There is an effect.

10 Coil Spring Forming Device 14 Pitch Tool 16 Coiling Tool (Forming Tool)
20 Spring length detection unit 21E Encoder (rotational position sensor)
24 Contact 25 Linear Actuator 50 Wire Feeder 54E Encoder 60 Controller 60C Control Circuit (Spring Length Measuring Means, Intermediate Reference Spring Length Determining Means, Pitch Changing Means)
90 Wire material 91 Coil spring 91A Tip end winding (tip end side winding)
DT1 Pitch data table DT2 Intermediate reference value data table

Claims (6)

A wire with a preset feed amount set in advance is fed from the wire feeder, abutted against the forming tool and slidably contacted with the pitch tool, and the preset spring length, coil diameter and pitch set in advance. In a coil spring forming apparatus for forming a coil spring,
A linear actuator that converts the rotational power of the servo motor into linear motion power in the winding axis direction of the coil spring to linearly move the contact;
A rotational position sensor for detecting a distance between an origin position in a linear movement range of the contact and a contact position contacting the tip of the coil spring provided in the servo motor;
A spring length measuring means for measuring a spring length in the middle of forming the coil spring as an intermediate measured spring length based on a distance detected by the rotational position sensor;
A feed amount measuring means for measuring the feed amount of the wire from the start of forming the coil spring to the time of measuring the intermediate measured spring length as an intermediate wire feed amount;
The target spring length for the intermediate wire feed amount is stored as an intermediate reference spring length and determined from the intermediate wire feed amount, or the target spring length for the intermediate wire feed amount is determined as an intermediate reference Intermediate reference spring length determination means that calculates and determines from the theoretical formula as the spring length;
An error between the intermediate reference spring length and the intermediate measured spring length is canceled after the measurement of the intermediate measured spring length and before the wire feed amount reaches the set feed amount, and the coil A coil spring comprising pitch changing means for changing the position of the pitch tool and changing the pitch of the coil spring during molding so that the actual spring length of the entire spring approaches the set spring length Molding equipment.   The intermediate wire feed amount is set to a constant value, and when the wire feed amount measured by the feed amount measuring means coincides with the intermediate wire feed amount which is the constant value, the wire feed amount is set. 2. The coil spring forming apparatus according to claim 1, wherein the supply is stopped and the intermediate measured spring length is measured by the spring length measuring means.   The intermediate reference spring length determining means includes an intermediate reference value data table that stores a plurality of intermediate wire feed amounts and a plurality of intermediate reference spring lengths corresponding to each other, and is measured by the feed amount measuring means. 2. The coil spring forming apparatus according to claim 1, wherein the intermediate reference spring length corresponding to the intermediate wire feeding amount is selected and determined from the intermediate reference value data table. The intermediate reference spring length determining means sets the intermediate wire feed amount to L, sets the wire feed amount required for the end winding portion of the coil spring to La, sets the set pitch to P, and sets the set coil diameter. Is D, the wire diameter is d, the number of turns of the end winding portion is Na, and the intermediate reference spring length is H,
s = L-La
H = P · s / [(π · D) ² + P ² ] ^1/2 + Na · d + d / 2
The intermediate reference spring length H is calculated and determined from the theoretical formula as follows and the intermediate wire feed amount L measured by the feed amount measuring means. 1. A coil spring forming apparatus according to 1. A pitch data table storing the pitch of the coil spring and the position of the pitch tool in association with each other;
The pitch changing means sets the set value of the effective number of turns of the coil spring as N, sets the set pitch as P, sets the corrected pitch as the changed pitch as p, sets the set coil diameter as D, and sets the wire diameter as d. The intermediate wire feed amount is L, the wire feed amount required for the end winding portion of the coil spring is La, and the value obtained by subtracting the intermediate reference spring length from the intermediate measured spring length is δ. If
s = L-La
p = {N · P − [(s / K) · P + δ]} / (N−s / K)
K = [(π · D) ² + P ² ] ^1/2
5. The pitch tool according to claim 1, wherein the pitch tool is moved to the position of the pitch tool determined from the corrected pitch p calculated from the formula and the pitch data table. A coil spring forming apparatus according to claim 1. A wire rod is fed from a wire rod feeding device, abutted against a forming tool and slidably contacted with a pitch tool to mold a coil spring having a preset spring length, a preset coil diameter and a preset pitch, and the coil The spring length during spring formation is measured as the intermediate measured spring length, and the error between the intermediate measured spring length and the preset intermediate reference spring length determining means is canceled after the measurement of the intermediate measured spring length. A part of a coil spring forming apparatus that changes the position of the pitch tool and changes the pitch of the coil spring in the middle of forming so that the actual spring length of the entire coil spring approaches the set spring length. , A spring length measuring device for measuring the intermediate measured spring length,
A linear actuator for converting the rotational power of the servo motor into linear motion power in the winding axis direction of the coil spring to linearly move the contact; and from the origin position in the linear motion range of the contact to the tip of the coil spring The distance between the contact position and the contact position is detected by a rotational position sensor provided in the servo motor, and the intermediate measured spring length is measured based on the detected distance. Spring length measuring device.

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