Injection device

Abstract

To provide an injection device capable of fitting a spline shaft to a spline groove even when a central axis of a screw and the central axis of a bush are inclined.SOLUTION: A control part 90 of the present invention sequentially executes a first control step of controlling an operation of rotational drive means 71 to rotate an output shaft 78 forward and then reverse after an engagement between a screw side engagement part and an output shaft side engagement part has begun, and a second control step of controlling an operation of linear drive means 61 to move the output shaft 78 forward. In the first control step, a forward rotation angle θF and a reverse rotation angle θR of the output shaft 78 have a relationship of rotation angle θF>rotation angle θR.SELECTED DRAWING: Figure 4

Description

[TECHNICAL FIELD]

[0001] The present invention relates to an injection device used for, for example, an injection molding machine. [BACKGROUND ART]

[0002] An injection device includes a screw for plasticizing and injecting resin. The screw can rotate and move forward and backward to plasticize and inject the resin. For this purpose, the injection device includes a linear driving means and a rotation driving means. The linear driving means moves the screw forward and backward in the axial direction, and the rotation driving means rotates the screw around the axis. By way of example, the advancing / retreating force of the linear driving means and the rotational force of the rotation driving means are transmitted to the screw via a bush fitted to the screw. The fitting between the screw and the bush is performed using a key or a spline structure which is a type of key. That is, a spline shaft having, for example, a plurality of splines formed thereon is provided on the outer peripheral surface of the screw, a plurality of spline grooves are provided on the inner peripheral surface of the bush, and the screw and the bush are fitted to each other.

[0003] Patent Document 1 and Patent Document 2 propose a method for automatically fitting a screw and a bush using a spline structure. Patent Document 1 controls the operations of the linear drive motor and the rotary drive motor based on the output torque (linear motion torque) of the linear drive motor to automatically fit the screw and the bush. Patent Document 2 controls the operations of the linear drive motor and the rotary drive motor based on not only the linear motion torque but also the rotation torque of the rotary drive motor to automatically fit the screw and the bush. According to the proposal of Patent Document 2, unnecessary rotation of the bush in Patent Document 1 can be avoided. [PRIOR ART DOCUMENTS] [PATENT DOCUMENTS]

[0004] [Patent Document 1] Japanese Patent No. 6546236 [Patent Document 2] Japanese Patent No. 7082254 [Overview of the project] [Problems that the invention aims to solve]

[0005] Ideally, the screw and bush should be fitted together with the central axis of the screw aligned with the central axis of the bush. However, in reality, the straightness of the screw and the installation conditions of the bush can cause the central axes to be misaligned. This misalignment causes the central axes to become non-parallel, and as the screw is inserted into the bush, the spline shaft of the screw and the spline groove of the bush interfere with each other at the bush's opening, increasing the linear torque. Patent documents 1 and 2 do not consider this increase in linear torque due to the tilting of the central axes. Therefore, in patent documents 1 and 2, the fitting process may be incorrectly terminated due to the increased linear torque, even though the fitting is not complete. Furthermore, if the degree of interference is large, not only may the fitting not progress, but galling may occur at the point of interference, or the spline shaft and spline groove may become impossible to separate due to a wedge effect.

[0006] Therefore, the present invention aims to provide an injection device that can complete the fitting of a spline shaft and a spline groove even when the central axis of the screw and the central axis of the bush are inclined. [Means for solving the problem]

[0007] The injection device of the present invention comprises a screw having a screw-side fitting portion, An output shaft having an output shaft side fitting portion that fits into a screw side fitting portion, A linear drive mechanism for moving the output shaft in the axial direction of the screw, A rotational drive mechanism that rotates the output shaft around the axis of the screw, The system includes a control unit that controls the operation of a linear drive means and a rotary drive means so as to engage the screw-side fitting portion and the output shaft-side fitting portion. The control unit of the present invention is After the engagement between the screw-side fitting portion and the output shaft-side fitting portion begins, A first control step involves controlling the operation of the rotational drive means so that the output shaft rotates forward and then reverses, The process involves sequentially performing a second control step, which controls the operation of the linear drive means to advance the output shaft, In the first control step, the forward rotation angle θF and the reverse rotation angle θR of the output shaft are in a relationship where rotation angle θF > rotation angle θR.

[0008] In the preferred control unit of the present invention, the first control step and the second control step are repeated until the output shaft moves forward by a predetermined travel distance threshold.

[0009] In the preferred control unit of the present invention, in the first control step, when the measured rotational torque value in the forward direction of the rotational drive means reaches a rotational torque threshold, the output shaft is reversed.

[0010] In the preferred control unit of the present invention, in the second control step, when the measured forward force of the output shaft reaches a predetermined second forward force threshold, the forward movement of the output shaft is stopped.

[0011] In the present invention, a preferred control unit controls the operation of the linear drive motor so that the screw-side fitting portion and the output shaft-side fitting portion move closer together from a separated state, prior to the first control step, and when the measured forward force reaches a predetermined first forward force threshold, it stops the forward movement of the output shaft and stores the stopped position as a stop position threshold, and then moves the output shaft backward by a predetermined amount, rotates it forward by a predetermined amount, and then moves it forward.

[0012] A preferred control unit in the present invention continues forward movement if the measured value of the stop position of the output shaft exceeds the stop position threshold.

[0013] In the present invention, a preferred control unit stops the forward movement of the output shaft and then reverses it by a predetermined amount when the measured forward force of the output shaft reaches a predetermined second forward force threshold. [Effects of the Invention]

[0014] According to the injection device of the present invention, by reversing the output shaft in the middle of the fitting procedure, fitting can proceed smoothly while eliminating or alleviating interference. Therefore, even when the central axis of the screw and the central axis of the bush are inclined, the spline shaft and the spline groove can still be fitted together. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [Figure 1] It is a diagram showing an overall configuration of the injection device according to the embodiment. [Figure 2] It is a diagram showing an example of the configuration of a spline structure in the injection device according to the embodiment. [Figure 3] It is a diagram showing a configuration example of a control unit according to the embodiment. [Figure 4] It is a plan view of a set of a spline and a spline groove, showing the gist of a fitting procedure in the spline structure according to the embodiment. [Figure 5] It is a front view of a set of a spline and a spline groove, showing a series of fitting procedures in the spline structure according to the embodiment. [Figure 6] It is a plan view of a set of a spline and a spline groove, showing a series of fitting procedures in the spline structure according to the embodiment. [Figure 7] It is a timing chart showing the fitting procedure according to the embodiment. [Figure 8] It is a flow chart showing a control procedure according to the embodiment. [Figure 9] Following FIG. 8, it is a flow chart showing a control procedure according to the present embodiment. [Figure 10] It is a plan view of a set of a spline and a spline groove, showing the gist of another fitting procedure in the spline structure according to the embodiment. [Figure 11] It is a diagram showing an example of an operation before the start of fitting according to the embodiment. [Figure 12] It is a diagram showing another example of an operation before the start of fitting according to the embodiment. [Modes for carrying out the invention]

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. The injection device 1 according to this embodiment, when combined with a clamping device (not shown), constitutes an injection molding machine. The injection device 1 has a spline structure SS between the screw 31 and the output shaft 78, and the screw 31 and the output shaft 78 are fitted together via this spline structure SS. The injection device 1 automatically fits the screw 31 and the output shaft 78, but in the process of fitting, the output shaft 78 is rotated in reverse in addition to forward rotation relative to the screw 31, so that fitting can be completed even if the spline 31D of the spline shaft 31C and the spline groove of the bush 78B are inclined relative to each other. The following describes the configuration of the injection device 1, the configuration of the spline structure, and the fitting procedure of the spline structure in that order. In the injection device 1, the side indicated by F in Figure 1 is defined as the front, and the side indicated by R is defined as the rear. The definitions of front F and rear R include a relative meaning. Furthermore, the length direction L and height direction H of the injection device 1 are defined as shown in Figure 1.

[0017] [Configuration of injection device 1: Figure 1] The configuration of the injection apparatus 1 according to this embodiment will be described with reference to Figure 1. The injection device 1 comprises a base 10 that supports the components of the injection device 1, an injection unit 30 that includes a screw 31 and is involved in the injection of resin, a drive unit 50 that is responsible for the forward and backward movement and rotation of the screw 31, and a control unit 90 that controls the operation of the drive unit 50. The injection device 1 supplies molten resin toward the mold of a clamping device (not shown) by controlling the forward and rotational movement of the screw 31 by the drive unit 50 with the control unit 90.

[0018] [Base 10] The base 10 comprises a bed 11 extending from the front F to the rear R, support members 13A and 13B provided on the bed 11, and a guide rail 16 provided on the bed 11. The support members 13A and 13B rotatably support the ball screw shaft 66 of the linear drive unit 60 in the front (F) and rear (R) directions. The linear motion transmission unit 15 is connected to a ball screw nut 67 that is rotatably supported on the ball screw shaft 66 and moves in the front-rear direction as the ball screw nut 67 moves in the front-rear direction.

[0019] The base 10 includes a support base 17 that supports the heating cylinder 33 of the injection molding unit 30 on the bed 11. The support base 17 is fixed in front (F) of the bed 11. Therefore, the injection molding unit 30 supported by the support base 17 is fixed in position relative to the bed 11. The support base 17 is provided with a hopper 19 into which resin pellets, which are the raw material for injection molding, are fed. The hopper 19 communicates with a pellet passage 18 that penetrates the inside of the support base 17 in the height direction H and with an inlet 34 provided in the heating cylinder 33.

[0020] [Injection unit 30: Figure 1] As shown in Figure 1, the injection unit 30 comprises a screw 31, a hollow cylindrical heating cylinder 33 that surrounds almost the entire length L of the screw 31, and an injection nozzle 35 provided at the front end of the heating cylinder 33.

[0021] The screw 31 comprises a body 31A with a helical groove formed on its outer circumference, a screw shaft 31B connected to the rear end of the body 31A, and a spline shaft 31C provided at the rear end of the screw shaft 31B. The screw 31 is connected to the output shaft 78 via the spline shaft 31C, but Figure 1 shows them separated. The spline shaft 31C constitutes the screw-side fitting element, and the bush 78B of the output shaft 78 constitutes the output shaft-side fitting element, and together they constitute the spline structure SS.

[0022] The heating cylinder 33 is detachably fixed to the support base 17. Therefore, the heating cylinder 33 is fixed in position relative to the bed 11 together with the support base 17. The screw 31 housed inside the heating cylinder 33 is capable of reciprocating in the front-to-back direction and rotating within the heating cylinder 33. The heating cylinder 33 is surrounded by electric wire heaters, such as band heaters and cartridge heaters (not shown in the diagram), and the resin material inside the heating cylinder 33 is heated by supplying power to the electric wire heaters from a power source (not shown in the diagram).

[0023] [Drive unit 50: Figure 1] Next, the drive unit 50 will be described. The drive unit 50 comprises a linear drive unit 60 responsible for the forward and backward movement of the output shaft 78, and a rotary drive unit 70 responsible for the rotation of the output shaft 78. When referring to the rotation of the output shaft 78 by the rotary drive unit 70, both forward and reverse rotation are included. Forward and reverse rotation means that if one is clockwise, the other is counterclockwise.

[0024] The linear drive unit 60 includes a first motor 61 and a ball screw 65 that operates by the rotational driving force of the first motor 61. The first motor 61 comprises a first rotating shaft 62 and a first pulley 63 fitted and fixed to the first rotating shaft 62. The first motor 61 is a servo motor, and its rotation is controlled by the control unit 90. The second motor 71 is similar. In this embodiment, the linear drive unit 60 is shown as comprising the first motor 61 and a ball screw 65 that operates by the rotational driving force of the first motor 61, but the linear drive unit 60 may be a hydraulic cylinder. Furthermore, the second motor 71 is preferably a servo motor capable of high-precision position control of minute amounts, but a hydraulic motor may be used if the mating gap between the bush 78B and the spline shaft 31C is large.

[0025] The ball screw 65 comprises a ball screw shaft 66 whose ends are rotatably supported by supports 13A and 13B, and a ball screw nut 67 rotatably supported on the ball screw shaft 66. Inside the ball screw nut 67 are multiple balls, which are not shown in the illustration, serving as rolling elements. A third pulley 68 is fixed to the front (F) end of the ball screw shaft 66 of the ball screw 65. An endless transmission belt 69 is wrapped around the third pulley 68 and the first pulley 63. A linear motion transmission unit 15 is also connected to the ball screw nut 67. Therefore, when the first motor 61 is rotated forward, the linear motion transmission unit 15 moves forward as the ball screw nut 67 moves forward, and when the first motor 61 is rotated backward, the linear motion transmission unit 15 moves backward as the ball screw nut 67 moves backward. The housing 75 is mounted on the guide rail 16. In this context, "forward movement" refers to movement from the rear (R) to the front (F), while "backward movement" refers to the opposite, movement from the front (F) to the rear (R).

[0026] The rotary drive unit 70 comprises a second motor 71 and a housing 75 that supports the second motor 71. The second motor 71 includes a second rotating shaft 72 and a first gear 73 that is fitted and fixed to the second rotating shaft 72. The first gear 73 and the second gear 79, which will be described later, mesh with each other to function as a reduction gear.

[0027] The housing 75 comprises a chassis 76 having an internal storage space 77, and an output shaft 78 rotatably supported in the storage space 77. The housing 76 has shaft support holes 76F and 76R that penetrate from front to back on the front (F) and rear (R) sides, respectively, and the housing space 77 communicates with the outside through the shaft support holes 76F and 76R.

[0028] The output shaft 78 comprises a drive shaft 78A rotatably supported in a shaft support hole 76F, a driven shaft 78E supported in a shaft support hole 76R, and a connecting shaft 78D connecting the drive shaft 78A and the driven shaft 78E. The output shaft 78 is rotatably supported in the housing 76 of the housing 75 via ball bearings BB, with the drive shaft 78A and the driven shaft 78E both being supported. A bush 78B is formed on the front (F) side of the drive shaft 78A, and this bush 78B and the spline shaft 31C constitute a spline structure SS. The spline structure SS will be described in more detail later. The driven shaft 78E has its rear (R) side exposed to the outside from the housing 76, and the second gear 79 is fitted and fixed to this exposed portion. Here, a parallel-axis gear is exemplified as the reduction gear that transmits the rotational motion of the second motor 71 to the second rotating shaft 72, but known gears such as helical gears, bevel gears, and hypoid gears can be used. Furthermore, the reduction gear is not limited to a gear train, but may also consist of, for example, a pulley and belt.

[0029] When the first motor 61 rotates forward, the output shaft 78, which is housed in the housing 75 mounted on the guide rail 16, moves forward, and when the first motor 61 rotates in reverse, the output shaft 78 moves backward. If the bush 78B of the output shaft 78 and the spline shaft 31C of the screw 31 are fitted and connected, the screw 31 will move forward or backward depending on whether the first motor 61 rotates forward or backward. When the second motor 71 rotates forward, the screw 31 rotates forward via the output shaft 78, and when the second motor 71 rotates in reverse, the output shaft 78 also rotates in reverse.

[0030] As shown in Figure 1, a pressure sensing sensor PS, such as a load cell, is provided between the linear motion transmission unit 15 and the housing 75. The pressure sensing sensor PS measures the forward force when the housing 75 moves forward or backward, and this measured forward force value FF is sent to the control unit 90.

[0031] [Spline structure SS: Figure 2] Next, the spline structure SS will be explained with reference to Figure 2. The spline structure SS consists of a spline shaft 31C and a bush 78B. The spline shaft 31C has multiple splines 31D projecting outward in the radial direction r1 on its outer surface 31O, for example, six splines 31D. The splines 31D are formed parallel to the central axis C1 of the spline shaft 31C. The bush 78B has multiple spline grooves 78C on its inner circumferential surface 78I that are recessed outward in the radial direction r2, for example, six spline grooves, the same number as the spline 31D. The spline grooves 78C are formed along the central axis C2 of the bush 78B.

[0032] The spline shaft 31C and bush 78B are manufactured with dimensions and shapes that allow the spline 31D, spline groove 78C, etc., to be fitted together. When the spline shaft 31C and bush 78B are fitted together, the screw 31 and the output shaft 78 are connected in the circumferential direction, and the spline (not shown) is mechanically connected in the direction of the central axes C1 and C2 by a retaining member that prevents it from coming out of the output shaft 78 in the axial direction. Therefore, when the output shaft 78 rotates forward or backward, the screw 31 rotates forward or backward. Also, when the output shaft 78 moves forward or backward, the screw 31 moves forward or backward.

[0033] [Control Unit 90: Figure 3] The control unit 90 controls the operation of the drive unit 50 of the injection device 1. The control unit 90 controls the forward and backward movement of the screw 31 by controlling the rotation of the first motor 61, and controls the forward and reverse rotation of the screw 31 by controlling the rotation of the second motor 71.

[0034] [Configuration of the control unit 90: Figure 3] As shown in Figure 3, the control unit 90 includes a transmitting / receiving unit 91, a storage unit 93, a processing unit 95, and an input / display unit 97. This functional division is just one example, and the functions can be further subdivided or integrated. For example, the input / display unit 97 can be divided into a part specialized for input and a part specialized for display. The control unit 90 is composed of a computer device that includes a CPU (Central Processing Unit), auxiliary storage devices such as a hard disk drive (HDD) and a solid state drive (SSD), main memory such as random access memory (RAM), and a display.

[0035] [Transmitting / receiving unit 91] The transmitting / receiving unit 91 transmits signals to instruct the operation of the first motor 61 and the second motor 71, respectively. The transmitting / receiving unit 91 also receives pressure data (actual forward force value FF) from the position sensor PS. Furthermore, the transmitting / receiving unit 91 receives rotation angle data (actual rotation angle value) and rotation torque data (actual rotation torque value RT) from the encoder and rotation torque detector of the first motor 61 and the second motor 71, respectively. The various measured data received by the transmitting / receiving unit 91 are transferred to the processing unit 95. The actual forward force value FF, the actual rotation angle value, and the actual rotation torque value RT are collectively referred to as measured value data.

[0036] [Storage section 93] The storage unit 93 stores data necessary for controlling the operation of the first motor 61 and the second motor 71, and in particular for handling measured value data, it includes a determination data storage unit 93A and a measured value data storage unit 93B.

[0037] [Decision data storage unit 93A] The judgment data storage unit 93A stores data that serves as a criterion for determining whether the measured value data is within an acceptable range by comparing it with the measured value data. The judgment data includes the following: First forward force threshold FFc1, second forward force threshold FFc2 Stop position threshold SPc, torque threshold Tc, travel distance threshold TLC

[0038] [Measured Value Data Storage Unit 93B] The measured value data storage unit 93B stores the measured value data acquired via the transmitting / receiving unit 91 in conjunction with the operation of the first motor 61 and the second motor 71. The measured value data includes the following: Measured forward force FF, measured position SP, measured rotational torque RT, actual distance traveled TL

[0039] [Processing section 95] The processing unit 95 controls the operation of the first motor 61 and the second motor 71 using the threshold value stored in the determination data storage unit 93A and the measured value data stored in the measured value data storage unit 93B. Through this operation control, the processing unit 95 can achieve automatic engagement between the screw 31 and the output shaft 78 via the spline structure SS. The procedure for controlling the first motor 61 and the second motor 71 by the processing unit 95 will be described later.

[0040] [Input / Display Unit 97] The input / display unit 97 can input various types of data, such as judgment data, and display the control status of the operation of the first motor 61 and the second motor 71 by the control unit 90.

[0041] [Key parts of the fitting procedure: See Figure 4] The following describes the fitting procedure for the spline structure SS in the injection device 1. First, the main parts of the fitting procedure will be explained with reference to Figure 4, and then the entire fitting procedure will be explained with reference to Figures 5 to 8. In Figure 4, the dimensions of spline 31D and spline groove 78C are exaggerated to distinguish their behavior. Although it is spline groove 78C that moves, in Figure 4, spline groove 78C is depicted as stationary. This is also the case in Figures 5 and 6. In Figure 4, the mating procedure proceeds in the order I, II, III, ... VIII, IX. Furthermore, the symbols such as in Figure 4 correspond to the symbols such as in Figures 5 and 6, and the dashed circles indicate the points where spline 31D and spline groove 78C abut and interfere. The spline 31D actually abuts the wall surrounding spline groove 78C, but for the sake of simplicity, it is described as "spline 31D and spline groove 78C abutting." The same applies below.

[0042] The fitting mechanism described here begins with a state in which a portion of the spline 31D has already begun to fit into the spline groove 78C, and the spline 31D is interfering with the spline groove 78C at the right wall surface RW shown in the figure (Figure 4). If the spline groove 78C is advanced while the interference state shown in Figure 4(I) persists, the degree of interference between the two will increase, making it impossible to advance the spline groove 78C to the back of the spline 31D and complete the fitting. Therefore, the output shaft 78 is rotated forward to separate the spline 31D from the right wall surface RW of the spline groove 78C and eliminate the interference. This forward rotation causes the tip of the spline 31D to interfere with the left wall surface LW of the spline groove 78C, as shown in Figure 4. Next, the output shaft 78 is rotated in reverse. Ideally, this reverse rotation should be such that the interference between the spline 31D and the side wall of the spline groove 78C is eliminated, as shown in Figure 4(III). As an example, this reverse rotation is such that the rotation angle is about half of the previous forward rotation. Once the interference between the spline 31D and the spline groove 78C is eliminated, the spline groove 78C can be advanced. Thus, by performing the first control step of the present invention, which involves forward rotation and reverse rotation by an angle smaller than the amount of forward rotation, the spline groove 78C can be advanced relative to the spline 31D even if the spline 31D and the spline groove 78C are inclined relative to each other.

[0043] After forward and reverse rotation, the spline 31D can be advanced further than before as the second control step of the present invention. However, as shown in Figure 4, the spline 31D may interfere with the right wall surface RW of the spline groove 78C, making it impossible to advance the spline groove 78C any further. In this case, as shown in Figure 4(V), the spline groove 78C is retracted, and then, after the forward rotation (Figure 4) and reverse rotation (Figure 4(VII)) of the spline groove 78C described above, it is advanced (Figure 4(VIII)). This procedure is repeated until the spline 31D and spline groove 78C are completed (Figure 4). At this time, the inclination between the spline 31D and the spline groove 78C may or may not be resolved.

[0044] As described above, in this embodiment, a first control step is performed to control the operation of the second motor 71 so as to rotate the output shaft 78 forward and then in the reverse direction after the engagement between the spline 31D and the spline groove 78C begins, and a second control step is performed to control the operation of the first motor 61 for linear drive so as to advance the output shaft 78. By doing so, even if the central axes C1 and C2 are inclined, relative forward movement between the spline 31D and the spline groove 78C can be achieved.

[0045] [For all fitting procedures, see Figures 5, 6, 7, 8, and 9] Next, with reference to Figures 5 to 9, the entire fitting procedure of the spline structure SS in the injection device 1 will be explained. Figure 5 shows a front view of a pair of splines 31D and spline grooves 78C, and Figure 6 shows a plan view of the same pair of splines 31D and spline grooves 78C, similar to Figure 4 mentioned above. Figure 7 shows an example of the progression of the position, forward force, and rotational torque of the output shaft 78 from the start to the completion of the mating operation. In the graph shown in Figure 7, the horizontal axis represents the elapsed time from the start of mating, and the vertical axis, from bottom to top, represents the measured position of the output shaft 78 from the start, the measured forward force FF of the output shaft 78, and the measured rotational torque RT of the output shaft 78.

[0046] The mating procedure begins with a gap between the spline 31D of the screw 31 and the spline groove 78C of the output shaft 78, as shown in Figure 6 S1, for example. Furthermore, the spline 31D and the spline groove 78C are offset in the circumferential direction CD from their mating positions, and the central axes C1 and C2 are inclined. The relationship between the forward or backward movement of the output shaft 78 and the rotation of the first motor 61, and the correspondence between the forward or reverse rotation of the output shaft 78 and the rotation of the second motor 71 are as follows; in the following explanation, the forward and reverse rotation of the first motor 61 and the second motor 71 will be omitted. Output shaft 78 moves forward: First motor 61 rotates forward. Output shaft 78 retracts: First motor 61 reverses. Output shaft 78 rotates forward: Second motor 71 rotates forward Output shaft 78 reverses: Second motor 71 reverses

[0047] [Figures 5, 6, 7: S1, Figures 8, 9: S101~S105] First, the output shaft 78 is moved forward, but this forward movement stops when the bush 78B of the output shaft 78 hits the spline shaft 31C of the screw 31 (Figures 6 and 7 S1, Figure 8 S105). Whether or not the bush 78B hits the spline shaft 31C is determined by whether or not the measured forward force value FF acquired by the control unit 90 reaches the first forward force threshold FFc1 (Figure 8 S103). The control unit 90 continues to move the output shaft 78 forward, that is, to rotate the first motor 61 forward, until the measured forward force value FF reaches the first forward force threshold FFc1 (Figure 8 S103 N). When the measured forward force value FF reaches the first forward force threshold FFc1 (Figure 8 S103 Y), the control unit 90 stops moving the output shaft 78 forward, that is, to rotate the first motor 61 forward, and stores the stopped position as the stop position threshold SPc (Figure 8 S105). The stopping position threshold SPc is used to determine whether the phases of the spline 31D and the spline groove 78C are aligned.

[0048] From the time the output shaft 78 starts moving forward until it stops, the measured forward force FF of the output shaft 78 remains constant, but while it is stopped, it is maintained at the first forward force threshold FFc1 (Figure 7 S1). From the moment the output shaft 78 starts moving forward until it stops, the measured rotational torque RT of the output shaft 78 remains at 0 (Figure 7 S1).

[0049] [Figures 5, 6, 7: S2, 8, 9: S107 (reverse / forward / forward)] After stopping the forward movement of the output shaft 78, the control unit 90 performs an operation to align the spline 31D with the spline groove 78C. In a preferred form, this operation begins by retracting the output shaft 78 by a small amount (e.g., about 1 mm) so that the bush 78B is positioned at a distance where it does not come into contact with the spline shaft 31C, in order to move the bush 78B away from the spline shaft 31C (Figures 6 and 7 S1, Figure 8 S107). Next, the output shaft 78 is rotated forward by a small amount (e.g., about 1°), and then the output shaft 78 is advanced (Figures 6 and 7 S2, Figure 8 S107). Note that the small retraction amount and small forward rotation amount are not limited to the approximately 1 mm and 1° exemplified, and any angle that the operator deems efficient based on experiments and experience is acceptable. Prior to or instead of the automatic forward movement of the output shaft 78 by the control unit 90, the operator may manually move the output shaft 78 forward to a position where it is close to the spline shaft 31C, and align it to the extent that the corresponding spline 31D and spline groove 78C engage. At this time, the position to which the corresponding spline 31D and spline groove 78C engage does not need to be a position where the spline 31D and spline groove 78C perfectly coincide and fit together; for example, it may be sufficient if the spline 31D and spline groove 78C coincide by about half in the width direction (circumferential direction).

[0050] During the above process, the measured forward force FF becomes negative while the output shaft 78 is reversing, but remains zero while the output shaft 78 is stationary, and returns to a positive value while it is moving forward (Figure 7 S2). Since the output shaft 78 rotates in the forward direction while it is not moving in the forward or backward direction, the rotational torque is positive. During the backward movement before the stop period and the forward movement after the stop period, the output shaft 78 stops rotating, so the rotational torque is zero (Figure 7 S2).

[0051] [Figures 5, 6, 7: S3, Figures 8, 9: S109~S113 (reverse / forward / forward)] During this forward movement, the control unit 90 acquires a measured position SP of the output shaft 78 and compares it with a previously stored stop position threshold SPc (Figure 8, S109). This comparison is performed to determine whether the phases of the spline 31D and the spline groove 78C are aligned. In other words, if the measured position SP of the output shaft 78 can move forward past the stop position threshold SPc, it means that the phases of the spline 31D and the spline groove 78C are aligned, and the spline 31D is in the spline groove 78C. In this case, the control unit 90 continues the forward movement of the output shaft 78 (Figure 8, S109 Y, Figure 8, S113).

[0052] If the measured position SP of the output shaft 78 does not exceed the stop position threshold SPc (Figure 8 S109 N), a determination is made as to whether the measured forward force FF reaches the first forward force threshold FFc1 (Figure 8 S111). If the measured forward force FF does not reach the first forward force threshold FFc1 (Figure 8 S111 N), the control unit 90 compares the measured position SP with the stop position threshold SPc. If the measured forward force FF reaches the first forward force threshold FFc1 (Figure 8 S111 Y), the control unit 90 causes the output shaft 78 to move backward by a small amount, rotate forward by a small amount, and then advances the output shaft 78 (Figure 8 S107).

[0053] During the above process, the measured forward force FF becomes negative while the output shaft 78 is reversing, but remains zero while the output shaft 78 is stationary, and returns to a positive value while it is moving forward (Figure 7 S3). While the output shaft 78 is stopped, it rotates in the forward direction, so the rotational torque is positive. During the forward movement period after the stop period, the output shaft 78 stops rotating, so the rotational torque is zero (Figure 7 S3).

[0054] [Figures 5, 6, 7: S4, S5, Figures 8, 9: S115~S123] During the process in which the phases of the spline 31D and the spline groove 78C align and the output shaft 78 continues to advance, the control unit 90 performs the operation described with reference to Figure 4. The determination process will also be discussed below. During the process of advancing the output shaft 78, the control unit 90 compares the measured forward force value FF with the second forward force threshold FFc2 (Figure 8, S115). This comparison is performed to determine whether or not the spline 31D and the spline groove 78C are interfering with each other based on the measured forward force value FF. In other words, if the spline 31D and the spline groove 78C are interfering with each other, the measured forward force value FF will increase, and this interference can be detected by comparing it with the second forward force threshold FFc2.

[0055] The control unit 90 continues to advance the shaft until the measured forward force FF reaches the second forward force threshold FFc2 (Figure 8, S115 N). Once the measured forward force FF reaches the second forward force threshold FFc2 (Figure 8, S115 S), the control unit 90 retracts the output shaft 78 by a small amount and then stops retracting (Figures 6, 7, S4, and 8, S117). The control unit 90 then rotates the output shaft 78 in the forward direction (Figure 8, S119). During this forward rotation, the control unit 90 compares the measured rotational torque RT of the output shaft 78 with the rotational torque threshold RTc (Figure 9, S121). This comparison is performed to determine whether the spline 31D interferes with the spline groove 78C (left wall LW or right wall RW). In other words, if the spline 31D interferes with the spline groove 78C, the measured rotational torque RT increases, and this interference can be detected by comparing it with the rotational torque threshold RTc. The control unit 90 continues to rotate the output shaft 78 in the forward direction until the measured rotational torque RT in the forward direction reaches the rotational torque threshold RTc. Once the measured rotational torque RT reaches the rotational torque threshold RTc, it stops the forward rotation of the output shaft 78 (Figures 6, 7 S5, 9 S123). Let θF be the angle (rotation angle) by which the output shaft 78 rotates in the forward direction from state S3 to state S5 in Figure 4.

[0056] [Figures 5, 6, 7: S6, S7, Figures 8, 9: S125~S133] The control unit 90 stops the forward rotation of the output shaft 78, then reverses the rotation of the output shaft 78 within a predetermined range of rotation angle θR, and then stops the reverse rotation (Figures 6, 7 S6, and 9 S125). The rotation angle θR and rotation angle θF have the relationship θF > θR, and the preferred rotation angle θR is 1 / 4θF to 3 / 4θF, more preferably about 1 / 2θF. This reverse rotation is intended to resolve the interference between the spline 31D and the spline groove 78C. The control unit 90 reverses the output shaft 78 and then moves the output shaft 78 forward (Figures 6, 7 S7, 9 S127). During this forward movement, the control unit 90 determines whether the output shaft 78 has moved forward by a distance equal to the length of the spline 31D, i.e., the travel distance threshold TLc (Figure 9 S129). If the output shaft 78 has moved forward by a distance equal to the travel distance threshold TLc (Figure 9 S129 Y), the control unit 90 stops the forward movement of the output shaft 78 (Figure 9 S133). On the other hand, if the output shaft 78 has not moved forward by a distance equal to the travel distance threshold TLc (Figure 9 S129 N), the control unit 90 compares the measured forward force FF with the second forward force threshold FFc2 during the forward movement of the output shaft 78 (Figure 8 S115). The control unit 90 continues to advance the shaft until the measured forward force FF reaches the second forward force threshold FFc2 (Figure 8 S115 N). Once the measured forward force FF reaches the second forward force threshold FFc2 (Figure 8 S115 S), the control unit 90 retracts the output shaft 78 by a small amount and then stops retracting (Figure 8 S117). Thereafter, the control unit 90 controls the rotation and movement of the output shaft 78 according to the procedure described above until the fitting is complete.

[0057] [effect] According to this embodiment, even if the central axes C1 and C2 begin to be fitted together while tilted relative to each other, the output shaft 78 is made to perform actions that avoid, eliminate, and mitigate excessive interference between the spline 31D and the spline groove 78C, i.e., forward rotation, reverse rotation, and forward movement. As a result, fitting can be completed even if the central axes C1 and C2 are tilted relative to each other.

[0058] In addition to the above, it is possible to select or replace the configurations listed in the above embodiments, or to change them to other configurations as appropriate, as long as it does not deviate from the spirit of the present invention.

[0059] [Tilt Reduction Action] Before performing the interference avoidance operation described above, an operation can be performed to reduce the inclination of spline 31D and spline groove 78C. This inclination reduction operation will be explained below with reference to Figure 10. The tilt reduction operation is performed between the forward movement (Figure 6 S3, Figure 8 S113) and backward movement (Figure 6 S4, Figure 8 S117) of the output shaft 78 before the interference avoidance operation. In other words, the forward movement of the output shaft 78 is continued as shown in S31 of Figure 10. Then, as shown in S32 of Figure 10, at interference point A, the output shaft 78 receives reaction forces F, F1 from the screw 31 (spline shaft 31C). Due to this reaction force F1, the output shaft 78 reverses direction by a small angle in the circumferential direction, as shown in S32. At this time, in order to facilitate the reversal due to the reaction force F1, it is preferable to leave the output shaft 78 free (unconstrained) in the rotational direction (forward and reverse directions). Simultaneously, as shown in S33 of Figure 10, at interference point A, the screw 31 receives a forward force F2 from the output shaft 78. At this time, as the output shaft 78 moves forward, contact point B moves towards the rear of the output shaft 78 and becomes the pivot point (B) of the spline 31D. As shown in S3 and S4 of Figure 10, the forward force F2 generates a moment M2 around the pivot point (B) of the spline 31D. Due to this moment M2, the screw 31 connected to the spline 31D is rotated by a small angle in a direction that reduces its tilt, as shown in S34 of Figure 10. After that, the forward movement of the output shaft 78 stops, and then the output shaft 78 moves backward.

[0060] As described above, the injection device 1, which includes a tilt reduction operation, can reduce the number of times interference avoidance operations are repeated.

[0061] [Before interference mitigation action] In the injection device 1, the operation prior to the interference reduction operation is not limited to the embodiments described above. It is sufficient that a portion of the spline 31D is inserted into the spline groove 78C. For example, the procedure described below can be adopted with reference to Figure 11 (first pattern) and Figure 12 (second pattern). The first and second patterns are similar in that they combine forward and reverse rotation, but the degree of reverse rotation differs.

[0062] <Pattern 1: Figure 11> Assume that the corresponding spline 31D and spline groove 78C do not mesh and interfere with each other. In this case, the output shaft 78 is moved back a small amount (S01), then rotated forward by a predetermined rotation angle θ1 (S02), and then moved forward again (S03). If the corresponding spline 31D and spline groove 78C still interfere after this forward movement, the output shaft 78 is moved back a small amount (S04). Figure 11 shows the procedure S02-S04 only once, but the procedure S02-S04 can be repeated multiple times. If the interference between the spline 31D and spline groove 78C cannot be resolved even after repeating S02-S04 and rotating to a rotation angle θ3, then the output shaft 78 is rotated in the reverse direction by a rotation angle θ1 instead of forward (S05), and then moved forward (S06). If the corresponding spline 31D and spline groove 78C interfere with this forward movement, the output shaft 78 is moved back a small amount (S07), then the output shaft 78 is rotated in the opposite direction by an angle θ1 (S08), and then moved forward again (S09). As a result of this operation, the corresponding spline 31D and spline groove 78C are aligned to the extent that they can engage with each other, and thus engagement begins.

[0063] The rotation angle θ3 referred to here is a reference value at which interference between the spline 31D and the spline groove 78C is judged to increase in the forward rotation direction. It refers to an angle corresponding to 1 / 2 to 1 / 3 of the groove width of the spline groove 78C, and is common to both forward and reverse rotation. Furthermore, instead of rotating to a rotation angle θ3 before starting the reverse rotation, the circumferential position of the output shaft 78 may be stored in advance in S01, and once the rotation angle reaches θ3, the shaft may be reversed to the circumferential position stored in S01 before starting S07. Also, in the forward rotation direction, the reference value for determining when the interference between the spline 31D and the spline groove 78C increases may be the number of rotations repeated at a rotation angle θ1, the time spent repeating the forward rotation, or the length of the circumferential direction of the output shaft 78 corresponding to the rotation angle θ3, rather than the rotation angle θ3. In addition, there is no problem in using a rotation angle different from the forward rotation angle θ1 for the reverse rotation (S05, S08).

[0064] As described above, the first pattern can perform multiple forward rotations at a rotation angle θ1 and multiple reverse rotations at a rotation angle θ1 before the fitting between the corresponding spline 31D and spline groove 78C begins.

[0065] <Pattern 2: Figure 12> In the second pattern, the operation is the same as the first pattern until the retraction by S04, but the rotation angle θ2 for the next reversal is larger in the second pattern than in the first pattern. In other words, in the second pattern, if the interference between the spline 31D and the spline groove 78C cannot be resolved by repeating S02 to S04 until the rotation angle θ3, the spline groove 78C is reversed by the width of the spline groove 78C (S11). This reversal changes the positional relationship between the central axis C1 and the central axis C2. That is, before this reversal, the central axis C2 was located to the left of the central axis C1 in the diagram, whereas after the reversal, the central axis C2 moves to the right of the central axis C1 in the diagram. The shaft is reversed by an angle θ2 corresponding to the groove width (S11), and then moved forward (S12). If the corresponding spline 31D and spline groove 78C still interfere with this forward movement, the output shaft 78 is moved back by a small amount (S13), and then the output shaft 78 is rotated forward by an angle θ1 (S14), and then moved forward (S15). Due to this forward movement, the corresponding spline 31D and spline groove 78C are aligned to the extent that they can fit together, and thus the fitting begins.

[0066] As described above, in the second pattern, while the rotation angle θ1 is the same for both the reverse rotation (S5, S8) and the forward rotation in the first pattern, the rotation angle θ2 in the reverse rotation is made considerably larger than that of the forward rotation, thereby changing the positional relationship between the central axis C1 and the central axis C2. This makes it possible to reduce the degree of interference between the spline 31D and the spline groove 78C by repeatedly performing forward rotation, and thus potentially reducing the number of forward rotations performed before mating begins. [Explanation of Symbols]

[0067] 1 Injection device 10 base 11 beds 13A,13B Support 15 Linear motion transmission section 16 Guide rails 17 Support stand 18 Pellet passage 19 Hoppa 30 Injection part 31 Screw 31A Main Unit 31B Screw shaft 31C Spline shaft 31D spline 31O outer surface 33 Heating cylinder 34 Inlet 35 Injection nozzles 50 Drive unit 60 Linear drive unit 61 First Motor 62 First rotation axis 63 First Pulley 65 Ball screw 66 Ball screw shaft 67 Ball screw nut 68 Third Pulley 69 Transmission belt 70 Rotary drive unit 71 Second Motor 72 Second rotation axis 73 First gear 75 Housing 76 cabinets 76F,76R Shaft support hole 77 storage spaces 78 Output shaft 78A Drive shaft 78B bushing 78C Spline groove 78D connecting shaft 78E Driven shaft 78I Inner surface 79. Second gear 90 Control Unit 91 Transmitter / Receiver 93 Memory section 93A Judgment Data Storage Unit 93B Measured Value Data Storage Unit 95 Processing Unit 97 Input / Display Unit BB ball bearing SS spline structure C1 center axis C1,C2 center axis F forward R rear H (height direction) L (Length direction) r1 radial direction r2 radial direction CD circumferential direction

Claims

1. A screw having a screw-side fitting portion, An output shaft having an output shaft side fitting portion that fits into the screw side fitting portion, A linear drive means for moving the output shaft in the axial direction of the screw, The output shaft is rotated by a rotational drive means that rotates it around the axis of the screw, The system includes a control unit that controls the operation of the linear drive means and the rotary drive means so as to engage the screw-side fitting portion and the output shaft-side fitting portion, The control unit, After the engagement between the screw-side fitting portion and the output shaft-side fitting portion begins, A first control step involves controlling the operation of the rotational drive means so that the output shaft rotates forward and then reverses, The following steps are performed in order: a second control step of controlling the operation of the linear drive means to advance the output shaft, An injection device in which, in the first control step, the forward rotation angle θF and the reverse rotation angle θR of the output shaft are in the relationship θF > θR.

2. The control unit, The first control step and the second control step are repeated until the output shaft moves forward by a predetermined distance threshold. The injection device according to claim 1.

3. The control unit, In the first control step, when the measured rotational torque value of the rotational drive means in the forward direction reaches the rotational torque threshold, the output shaft is reversed. The injection device according to claim 1.

4. The control unit, In the second control step, when the measured forward force of the output shaft reaches a predetermined second forward force threshold, the forward movement of the output shaft is stopped. The injection device according to claim 1.

5. The control unit, Prior to the first control step, the operation of the linear drive means is controlled so that the screw-side fitting portion and the output shaft-side fitting portion move closer together from a separated state. When the measured forward force reaches a predetermined first forward force threshold, the forward movement of the output shaft is stopped, and the stopped position is stored as the stop position threshold. Next, the output shaft is moved backward by a predetermined amount, rotated forward by a predetermined angle, and then moved forward in sequence. The injection apparatus according to claim 4.

6. The control unit, If the measured value of the stop position of the output shaft exceeds the stop position threshold, forward movement will continue. The injection device according to claim 5.

7. The control unit, When the measured forward force of the output shaft reaches a predetermined second forward force threshold, the forward movement of the output shaft is stopped, and then it is moved backward by a predetermined amount. The injection device according to claim 6.

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