Injection device

Abstract

To provide an injection device capable of maintaining a state of protruding of an injection needle from a housing for a while after charge is completed.SOLUTION: An injection device includes a disengaging mechanism for disengaging a plunger and an engaging member 6 by a barrel being housed in a barrel housing part with an injection needle protruding from one side of the housing and a plunger and an engaging member 6 relatively rotating around a center axis line with the plunger located at a terminal point by an energizing force of the plunger energizing part. There is provided a rotation suppressing mechanism suppressing rotary speed in relative rotation of the plunger and the engaging member 6.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to an injection device in which the needle can be withdrawn from the housing when used and can be returned to the housing after use. [Background technology]

[0002] An example of the injection device is described in Patent Document 1. The injection device includes a syringe, an engagement member, a plunger biasing portion, a barrel biasing portion, a housing that accommodates them, and a trigger portion. The syringe includes a barrel that is filled with a drug solution and has an injection needle at its tip, and a plunger that is configured to be movable from the base end side to the tip side of the barrel and is inserted into the barrel. A spiral inclined portion is provided at the base end of the barrel. The plunger includes a rod body extending in the central axis direction, and a first branch portion and a second branch portion protruding from the outer circumferential surface of the rod body, and the second branch portion is provided on the tip side in the central axis direction relative to the first branch portion. The engagement member includes a cylindrical engagement body into which the rod body can be inserted, and an outer flange-shaped biasing engagement portion protruding radially from the outer circumferential surface of the engagement body, and the biasing engagement portion is provided with a release hole through which the first branch portion can be inserted in the central axis direction. Moreover, the plunger and the engaging member are engaged by the second branch portion and the biasing engaging portion engaging with each other. Furthermore, the plunger biasing portion biases the engaging member toward the tip end side in the central axis direction, and the barrel biasing portion biases the barrel toward the base end side in the central axis direction. Moreover, the biasing force of the barrel biasing portion is set to be weaker than the biasing force of the plunger biasing portion. The housing includes a barrel accommodating portion and a plunger accommodating portion. The barrel accommodating portion accommodates the barrel and the barrel biasing portion in this order from the base end side to the tip end side in the central axis direction. In addition, the plunger accommodating portion accommodates the plunger biasing portion, the engaging member, and the plunger in this order from the base end side to the tip end side in the central axis direction. Moreover, the engaging member is accommodated in the plunger accommodating portion in a state where it resists the biasing force of the plunger biasing portion. Furthermore, the trigger portion engages with the engaging member housed in the plunger accommodating portion to hold the bias of the plunger biasing portion against release, and when operated, disengages from the engaging member to release the bias of the plunger biasing portion.

[0003] According to this injection device, the trigger portion is operated to release the engagement with the engaging member, thereby releasing the bias of the plunger biasing portion. The engaging member and the syringe are then pushed toward the tip side in the central axis direction by the bias of the plunger biasing portion. As a result, the barrel moves toward the tip side within the barrel housing portion while compressing the barrel biasing portion, and the injection needle protrudes from the barrel housing portion. Thus, the injection needle can be inserted into, for example, the skin.

[0004] Furthermore, when the barrel moving toward the tip side abuts against a part inside the barrel housing, the movement of the barrel is restricted. In response to this, the engagement member and the plunger are further moved toward the tip side in the central axis direction by the biasing force of the plunger biasing portion. Then, when the plunger moves toward the tip side inside the barrel, the medicinal liquid is discharged from the injection needle. Thus, for example, the medicinal liquid can be administered into the skin.

[0005] In the injection device described in Patent Document 1, when the plunger reaches just before the tip of the barrel, the second branch abuts against the inclined portion and slides, causing the plunger to rotate relative to the engaging member. Therefore, the first branch and the release hole are positioned in a circumferentially aligned position, and the engagement between the plunger and the engaging member is released. Thus, the syringe is released from the bias of the plunger biasing portion and is pushed toward the base end by the bias of the barrel biasing portion. Therefore, the injection needle returns into the housing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 162086 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in order to deal with problems such as leakage of the drug solution from the puncture site, it may be desirable to keep the injection needle punctured in the skin for a while after administration is completed. However, the injection device described in Patent Document 1 does not have a function for keeping the injection needle punctured in the skin for a while after administration is completed.

[0008] Therefore, an object of the present invention is to provide an injection device that can reliably complete administration by maintaining the injection needle protruding from the housing for a while after injection is completed. [Means for solving the problem]

[0009] The present invention relates to a syringe including a barrel having an injection needle at its tip, and a plunger inserted into the barrel so as to be reciprocally movable between the base end side of the barrel and the injection needle side, and a cylindrical housing for accommodating the syringe, the housing having a barrel accommodating section formed on one side in the direction of the central axis for accommodating the barrel so as to be movable between a state in which the injection needle is accommodated and a state in which the injection needle protrudes from one side of the housing at a predetermined distance to one side from the accommodated state, and a plunger accommodating section formed on the other side of the barrel accommodating section for accommodating the plunger; and a barrel accommodating section provided in the barrel accommodating section for urging the barrel from one side of the housing to the other side. an engaging member that is disposed in the plunger accommodating section and engages with the plunger; a plunger biasing section that engages with the engaging member and biases the plunger from the starting point toward the end point; and a disengagement mechanism that disengages the plunger from the engaging member by rotating the plunger and the engaging member relatively about a central axis when the barrel is accommodated in the barrel accommodating section with the injection needle protruding from one side of the housing and the plunger is positioned at the end point by the biasing force of the plunger biasing section, and further comprising a rotation suppression mechanism that suppresses the rotational speed of the relative rotation between the plunger and the engaging member in the disengagement mechanism.

[0010] According to the above configuration, when the plunger is at the end point with the injection needle protruding from one side of the housing, the injection of the drug solution is completed. Then, the disengagement mechanism rotates the plunger and the engagement member relative to each other with the plunger at the end point, thereby disengaging the plunger from the engagement member. Here, since the injection device of the present invention includes the rotation suppression mechanism, when the plunger and the engagement member rotate relative to each other, the rotation speed of the relative rotation is suppressed, and the time until the engagement between the plunger and the engagement member is released can be extended.

[0011] In addition, in the present invention, the disengagement mechanism may be configured to release the engagement between the plunger and the engaging member by rotating the engaging member about a central axis relative to the plunger, and the rotation suppression mechanism may suppress the rotational speed of the engaging member.

[0012] According to the above configuration, the rotation suppression mechanism suppresses the rotation speed of the engaging member, thereby making it possible to lengthen the time until the engagement between the plunger and the engaging member is released.

[0013] In addition, in the present invention, the engaging member includes an engaging rotating portion that engages with the plunger and rotates about a central axis relative to the plunger to disengage from the plunger, and the disengagement mechanism is configured to disengage the plunger from the engaging member by causing the engaging rotating portion to rotate relative to the plunger to disengage from the engaging rotating portion, and the rotation suppression mechanism includes an engaging non-rotating portion that does not rotate about the central axis relative to the engaging rotating portion, and a rotation suppression portion that is disposed between the engaging rotating portion and the engaging non-rotating portion and suppresses the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion, and may suppress the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion.

[0014] According to the above configuration, the rotation suppression mechanism suppresses the rotational speed of the engaging rotating part relative to the engaging non-rotating part, thereby suppressing the rotational speed of the engaging rotating part relative to the plunger, thereby lengthening the time until the engagement between the plunger and the engaging rotating part is released, and thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0015] In the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the engaging rotating portion and the engaging non-rotating portion.

[0016] According to the above configuration, the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion can be suppressed by the elastic force of the rotation suppression portion, thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0017] In addition, in the present invention, the disengagement mechanism may be configured to release the engagement between the plunger and the engaging member by rotating the plunger about a central axis relative to the engaging member, and the rotation suppression mechanism may suppress the rotational speed of the plunger.

[0018] According to the above configuration, the rotation suppression mechanism suppresses the rotation speed of the plunger, thereby making it possible to lengthen the time until the engagement between the plunger and the engaging member is released.

[0019] In addition, in the present invention, the plunger includes a plunger rotating portion that engages with the engaging member and rotates about a central axis relative to the engaging member to release the engagement, a plunger non-rotating portion that does not rotate about the central axis relative to the plunger rotating portion, and a rotation suppression portion that is disposed between the plunger rotating portion and the plunger non-rotating portion and suppresses the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion, and the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the plunger rotating portion to rotate relative to the engaging member to release the engagement between the engaging member and the plunger rotating portion, and the rotation suppression mechanism may include the plunger non-rotating portion and the rotation suppression portion, and suppress the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion.

[0020] According to the above configuration, the rotation suppression mechanism suppresses the rotational speed of the plunger rotating part relative to the plunger non-rotating part, thereby suppressing the rotational speed of the plunger rotating part relative to the engaging member, thereby lengthening the time until the engagement between the engaging member and the plunger rotating part is released, and the time until the engagement between the plunger and the engaging member is released can be lengthened.

[0021] In the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the plunger rotating portion and the plunger non-rotating portion.

[0022] According to the above configuration, the rotation speed of the plunger rotating portion relative to the plunger non-rotating portion can be suppressed by the elastic force of the rotation suppression portion, thereby lengthening the time until the engagement between the plunger and the engaging member is released. Effect of the Invention

[0023] As described above, according to the present invention, the time until the engagement between the plunger and the engaging member can be extended, thereby ensuring that administration is completed by maintaining the injection needle protruding from the housing for a while after injection is completed. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view of an injection device according to a first embodiment of the present invention, showing the initial state and an outline view of a plunger. [Diagram 2] FIG. 2 is a cross-sectional view of the housing according to the embodiment as viewed in a first radial direction. [Diagram 3] FIG. 3 is an exploded perspective view of the syringe according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the plunger main body according to the embodiment, and is a partially enlarged view of the plunger base. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV of FIG. [Figure 6] FIG. 6 is a perspective view of the engaging member according to the embodiment. [Figure 7] FIG. 7 is a cross-sectional view of the engaging member according to the embodiment as viewed in a second radial direction. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 10 is a detailed view showing a state in which the plunger accommodating engagement portion and the main body engagement portion in FIG. 1 are engaged with each other. [Figure 11] FIG. 11 is a cross-sectional view of the injection device according to the embodiment, showing a state in which the injection needle protrudes from the housing, and also showing an outline view of the plunger. [Figure 12] FIG. 12 is a cross-sectional view of the injection device according to the embodiment, showing a state in which administration of the medicinal liquid has been completed, and also showing an outline view of the plunger and the engagement member. [Figure 13]FIG. 13 is a detailed view showing a state in which the plunger accommodating engagement portion and the main body engagement portion in FIG. 12 are disengaged from each other. [Figure 14] FIG. 14 is a cross-sectional view of the injection device according to the embodiment, showing a state in which the engagement member has been rotated around the central axis relative to the plunger, and also showing an outline view of the plunger and the engagement member. [Figure 15] FIG. 15 is a detailed view showing a state in which the engagement body of FIG. 14 is rotated about the central axis. [Figure 16] FIG. 16 is a cross-sectional view taken along line XVI-XVI in FIG. [Figure 17] FIG. 17 is a cross-sectional view of the injection device according to the embodiment, showing a state in which the injection needle has returned into the housing, and also showing an outline view of the plunger and the engagement member. [Figure 18] FIG. 18 is a cross-sectional view of the plunger housing according to the second embodiment as viewed in a second radial direction. [Figure 19] FIG. 19 is a front view of the plunger body according to the embodiment. [Figure 20] FIG. 20 is a cross-sectional view taken along the line XX-XX in FIG. [Figure 21] FIG. 21 is a cross-sectional view of the rod body, plunger ring, and elastic body of the plunger. [Figure 22] FIG. 22 is a perspective view of the engaging member according to the same embodiment. [Figure 23] FIG. 23 is a cross-sectional view of the engaging member according to the same embodiment as viewed in a second radial direction. [Figure 24] FIG. 24 is a front view of the injection device according to the embodiment, showing the housing in cross section and illustrating the initial state. [Diagram 25] 25 is a cross-sectional view taken along the line XXV-XXV in FIG. 24. FIG. [Figure 26] FIG. 26 is a front view of the injection device according to the embodiment, showing the housing in cross section and illustrating the state in which administration of the medicinal liquid has been completed. [Figure 27] FIG. 27 is a cross-sectional view taken along the line XXVII-XXVII in FIG. [Figure 28] FIG. 28 is a front view of the injection device according to the embodiment, showing the housing in cross section and the state in which the plunger has been rotated about the central axis relative to the engagement member. [Figure 29] FIG. 29 is a cross-sectional view taken along the line XXIX-XXIX in FIG. [Diagram 30] FIG. 30 is a front view of the injection device according to the embodiment, showing the housing in cross section and the injection needle retracted into the housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the injection device of the present invention will be described. First, the configuration of an injection device 1 according to a first embodiment will be described.

[0026] In the following description, the direction in which the central axis O of the injection device 1 extends is referred to as the central axis direction X. The lower side of FIG. 1 is one side of the central axis direction X, and the upper side of FIG. 1 is the other side of the central axis direction X. In addition, the direction perpendicular to the central axis direction X is referred to as the radial direction. As shown in FIGS. 3 and 5, the radial direction includes a first radial direction Y1 and a second radial direction Y2 that are perpendicular to each other. Furthermore, the direction around the central axis O is referred to as the circumferential direction.

[0027] The injection device 1 is used, for example, when a patient administers a liquid medicine, such as insulin or a rheumatism treatment drug, to the patient's own body. As shown in Figs. 11 and 17, this injection device 1 projects an injection needle 503 from a housing 2 during use and returns the injection needle 503 to the housing 2 after use. As shown in Fig. 1, the injection device 1 includes a housing 2, a plunger biasing portion 3, a barrel biasing portion 4, a syringe 5, and an engagement member 6.

[0028] As shown in Fig. 1, the housing 2 is for accommodating the plunger biasing portion 3, the barrel biasing portion 4, the syringe 5, and the engagement member 6. As shown in Fig. 2, the housing 2 is formed in a tubular shape (specifically, a cylindrical shape) with one side open in the central axial direction X and the other side closed by a trigger portion 23 described later. The housing 2 includes a barrel accommodating portion 20, a partition portion 21, and a plunger accommodating portion 22.

[0029] As shown in Fig. 1, the barrel accommodating portion 20 is for accommodating the barrel 50. The barrel accommodating portion 20 is cylindrical with both sides open in the central axial direction X. As shown in Fig. 2, the barrel accommodating portion 20 includes a cylindrical other-side barrel accommodating portion 200 arranged on the other side in the central axial direction X, and a cylindrical one-side barrel accommodating portion 201 arranged on one side in the central axial direction X.

[0030] 2, a barrel convex portion 20A that protrudes radially inward is provided on the inner circumferential surface of the barrel other side accommodating portion 200 of this embodiment. This barrel convex portion 20A is provided over the entire area of ​​the central axial direction X of the barrel other side accommodating portion 200. Moreover, the barrel convex portion 20A of this embodiment is provided along the central axial direction X. Note that, in this embodiment, a pair of barrel convex portions 20A are provided on the inner circumferential surface of the barrel other side accommodating portion 200 so as to face each other in the first radial direction Y1.

[0031] 2, an urging stand 20B configured in an inner flange shape forming a through hole (not numbered) in the central axial direction X is provided on the inner peripheral surface of the barrel one-side accommodating portion 201. Note that the urging stand 20B in this embodiment is disposed on one side of the other end of the barrel one-side accommodating portion 201 in the central axial direction X.

[0032] As shown in FIG. 2, the barrel one accommodating portion 201 of this embodiment is provided with a through-hole 20C penetrating in the radial direction. The through-hole 20C is a through hole penetrating the barrel one accommodating portion 201 in the second radial direction Y2. The through-hole 20C of this embodiment is configured in a rectangular shape along the peripheral surface of the barrel one accommodating portion 201. In this embodiment, the through-hole 20C is provided on one side and the other side in the central axis direction X with respect to the biasing base portion 20B. Note that a pair of the through-holes 20C are provided in the barrel one accommodating portion 201 so as to face each other in the second radial direction Y2.

[0033] 2, the barrel one-side accommodating portion 201 is connected to one side of the barrel other-side accommodating portion 200 in the central axial direction X. Here, the inner diameter of the barrel one-side accommodating portion 201 is smaller than the inner diameter of the barrel other-side accommodating portion 200. Therefore, a barrel step 20D, which is a step continuous with the barrel other-side accommodating portion 200, is formed at the other end of the barrel one-side accommodating portion 201 in the central axial direction X. Note that the barrel step 20D is a flat surface that extends along the radial direction and also expands in the circumferential direction.

[0034] As shown in FIG. 2, the partition 21 is made of an annular member that forms a through hole penetrating in the central axial direction X. The partition 21 has one end and the other end in the central axial direction X that are flat surfaces that extend radially and circumferentially. The inner diameter of the partition 21 is smaller than the inner diameter of the barrel other-side accommodating part 200. Meanwhile, the outer diameter of the partition 21 is approximately the same as the outer diameter of the barrel other-side accommodating part 200. The partition 21 is arranged with one end in the central axial direction X abutting against the other end in the central axial direction X of the barrel accommodating part 20.

[0035] The plunger accommodating portion 22 is cylindrical and extends in the central axial direction X. As shown in Fig. 2, the plunger accommodating portion 22 includes a cylindrical plunger first accommodating portion 220 arranged on one side in the central axial direction X, and a cylindrical plunger second accommodating portion 221 arranged on the other side in the central axial direction X.

[0036] The plunger one-side accommodating portion 220 is cylindrical in shape with an inner diameter larger than the outer diameters of the barrel other-side accommodating portion 200 and the partition portion 21. Therefore, as shown in Fig. 2, the plunger one-side accommodating portion 220 is fitted onto the barrel other-side accommodating portion 200 and the partition portion 21 from the other side in the central axis direction X, whereby the plunger accommodating portion 22 is connected to the barrel accommodating portion 20 and the partition portion 21. Thus, the housing 2 is formed.

[0037] A plunger accommodating engagement portion (not numbered) is provided on the inner circumferential surface of the plunger other accommodating portion 221. As shown in Fig. 2, the plunger accommodating engagement portion of this embodiment includes a plunger accommodating protrusion 22A protruding radially inward from the plunger other accommodating portion 221 and a plunger accommodating recess 22B recessed into the plunger other accommodating portion 221.

[0038] The plunger accommodating protrusion 22A is continuously formed from the other end of the plunger other accommodating portion 221 in the central axial direction X toward one side. Moreover, one end of the plunger accommodating protrusion 22A in the central axial direction X is provided on the other side of the one end of the plunger other accommodating portion 221 in the central axial direction X. Therefore, the plunger accommodating protrusion 22A is not formed in the entire area of ​​the plunger other accommodating portion 221 in the central axial direction X, and is shorter than the plunger other accommodating portion 221 in the central axial direction X. Furthermore, the plunger accommodating protrusion 22A is formed along the central axial direction X. Note that the plunger accommodating protrusions 22A of this embodiment are provided in pairs on the inner circumferential surface of the plunger other accommodating portion 221 so as to face each other in the first radial direction Y1 and the second radial direction Y2. In contrast, the plunger accommodating recesses 22B are provided in the entire area of ​​the plunger other accommodating portion 221 in the central axial direction X. The plunger accommodating recess 22B is formed along the central axis direction X. Furthermore, the plunger accommodating recess 22B is disposed between the plunger accommodating protrusions 22A, 21A adjacent to each other in the circumferential direction.

[0039] 2, the plunger other accommodating portion 221 is connected to the other side of the plunger one accommodating portion 220 in the central axial direction X to form the plunger accommodating portion 22. Here, the inner diameter of the plunger other accommodating portion 221 is smaller than the inner diameter of the plunger one accommodating portion 220. Therefore, a plunger step portion (not numbered) that is a step portion continuing from the plunger one accommodating portion 220 is formed at one end of the plunger other accommodating portion 221 in the central axial direction X. The plunger step portion is a flat surface that extends along the radial direction and expands in the circumferential direction.

[0040] Here, the inner diameter of the plunger other side accommodating portion 221 is smaller than the outer diameter of the partition portion 21. Therefore, in the housing 2, the plunger step portion abuts against the other end of the partition portion 21 in the central axial direction X, as shown in FIG. 2. In this embodiment, the inner diameter of the plunger other side accommodating portion 221 is larger than the inner diameter of the partition portion 21.

[0041] 1 and 2, a trigger portion 23 is provided on the other side in the central axial direction X of the plunger other side accommodating portion 221. The trigger portion 23 includes a trigger attachment portion 230, a trigger main body portion 23A, and a trigger lock operation portion 23a.

[0042] As shown in FIG. 2, the trigger mounting portion 230 includes a trigger mounting base portion 231 that protrudes radially inward from the plunger other side accommodating portion 221, and a cylindrical trigger tube portion 232 that protrudes from the trigger mounting base portion 231 to the other side in the central axis direction X.

[0043] The trigger mount 231 has an inner flange shape that forms an insertion hole in the central axial direction X. The trigger mount 231 is disposed at the other end in the central axial direction X of the plunger other-side accommodating part 221. An insertion hole (not shown) is provided at one end in the central axial direction of the trigger mount 231.

[0044] The trigger tube portion 232 is disposed so as to surround the insertion hole. A locking step portion 233 is formed on the inner peripheral surface of the trigger tube portion 232. The locking step portion 233 extends in the central axis direction X from the trigger mount portion 231 along the middle of the trigger tube portion 232. A pair of the locking step portions 233 are provided circumferentially spaced apart from each other by approximately 180 degrees. In addition, a plurality of convex portions 234 that protrude radially outward are formed on the outer peripheral surface of the trigger tube portion 232.

[0045] As shown in FIG. 2, trigger body 23A includes a disk-shaped top plate portion 23B that is pressed down by a user to operate it, an outer skirt portion 23C that hangs down to one side in the central axis direction X from the outer peripheral edge of top plate portion 23B, an inner skirt portion 23F that hangs down to one side in the central axis direction X from top plate portion 23B radially inward from outer skirt portion 23C, and a flat plate portion 23G.

[0046] The outer skirt portion 23C is formed in a cylindrical shape. As shown in FIG. 1, the outer skirt portion 23C is formed with a release groove 23D by cutting out a part of the circumferential direction from one end in the central axis direction X to the other side in the central axis direction X. This release groove 23D is configured so that the lock step portion 233 can be inserted. In addition, the outer skirt portion 23C of this embodiment is formed with a pair of release grooves 23D that face each other in the radial direction. As shown in FIG. 2, a recessed interlocking groove 23E is provided on the outer peripheral surface of the outer skirt portion 23C. This interlocking groove 23E is provided on one side from the other end in the central axis direction X of the outer skirt portion 23C. Note that a plurality of interlocking grooves 23E are provided on the outer peripheral surface of the outer skirt portion 23C.

[0047] The outer diameter of the outer skirt portion 23C is smaller than the inner diameter of the trigger tube portion 232. Therefore, the trigger body portion 23A is configured to be insertable into the trigger tube portion 232. The length of the outer skirt portion 23C in the central axis direction X is the same as the length of the trigger tube portion 232 in the central axis direction X. In FIG. 2, the trigger body portion 23A is inserted into the trigger tube portion 232 with one end of the outer skirt portion 23C in the central axis direction X abutting against the lock step portion 233. Furthermore, the outer skirt portion 23C is configured to be rotatable about the central axis O while being inserted into the trigger tube portion 232. Therefore, the outer skirt portion 23C inserted into the trigger tube portion 232 is rotated about the central axis O, and the lock step portion 233 and the release groove 23D are aligned in the circumferential direction, so that the lock step portion 233 can be inserted into the release groove 23D. Therefore, when the release groove 23D and the lock step 233 are aligned in the circumferential direction, the trigger body 23A can be pushed toward one side in the central axis direction X.

[0048] The inner skirt portion 23F is cylindrical. As shown in Fig. 2, the outer diameter of the inner skirt portion 23F is smaller than the inner diameter of the outer skirt portion 23C. Therefore, the inner skirt portion 23F is disposed inside the outer skirt portion 23C. The inner skirt portion 23F has approximately the same length as the outer skirt portion 23C in the central axis direction X.

[0049] The flat plate portion 23G is a plate-like member having a length in the central axis direction X and a width and thickness in the radial direction. In Figs. 1 and 2, the flat plate portion 23G has a width in the first radial direction Y1 and a thickness in the second radial direction Y2. The flat plate portion 23G hangs down from the top plate portion 23B radially inward of the inner skirt portion 23F. The flat plate portion 23G is longer in the central axis direction X than the inner skirt portion 23F and the outer skirt portion 23C. The flat plate portion 23G is configured to be insertable into the through hole of the trigger mount portion 231.

[0050] 2, the trigger lock operation part 23a includes a cylindrical tube part 23b and a protruding part 23c protruding radially inward from the other end of the tube part 23b in the central axis direction X. A rotation groove 23d extending in the circumferential direction is formed in the tube part 23b by cutting out a part of the circumferential surface. The rotation groove 23d is configured so that the protruding part 234 can be inserted therein.

[0051] The inner diameter of the cylinder 23b is larger than the outer diameter of the trigger cylinder 232. Therefore, in FIG. 2, the cylinder 23b fits the trigger cylinder 232 with the protrusion 234 inserted into the rotation groove 23d. The protrusion 23c is configured to be insertable into the interlocking groove 23E. The protrusion 23c is inserted into the interlocking groove 23E, so that the trigger body 23A does not come off the trigger cylinder 232. Note that a plurality of protrusions 23c are provided in the circumferential direction in this embodiment. Here, the trigger lock operation part 23a is configured to be rotatable around the central axis O. Therefore, the trigger lock operation part 23a rotates around the central axis O, so that the trigger body 23A can be rotated around the central axis O.

[0052] The plunger biasing part 3 biases the syringe 5 and the engagement member 6 from the other side in the central axis direction X to one side. The plunger biasing part 3 of this embodiment biases the engagement member 6 to rotate around the central axis O. The plunger biasing part 3 of this embodiment is a compression coil torsion spring wound around the central axis O. The outer diameter of the plunger biasing part 3 is smaller than the inner diameter of the plunger accommodating part 22. Therefore, the plunger biasing part 3 is configured to be able to be accommodated in the plunger accommodating part 22. As shown in FIG. 1, the plunger biasing part 3 is accommodated in the plunger one accommodating part 220 with the other end in the central axis direction X inserted from one side in the central axis direction X into an insertion hole provided in the trigger mounting base part 231.

[0053] The barrel biasing part 4 biases the barrel 50 from one side to the other side in the central axis direction X. As shown in FIG. 1, the barrel biasing part 4 in this embodiment is a compression coil spring wound around the central axis O. The barrel biasing part 4 is configured to be accommodated in the barrel housing part 20. Specifically, the barrel biasing part 4 has a diameter larger than the through hole formed by the biasing stand part 20B and a diameter smaller than the inner diameter of the barrel one housing part 201. Therefore, as shown in FIG. 1, the barrel biasing part 4 is accommodated in the barrel housing part 20 in a state of abutting against the biasing stand part 20B from the other side in the central axis direction X. Therefore, the barrel biasing part 4 is prevented from moving to one side in the central axis direction X by the biasing stand part 20B. The biasing force of the barrel biasing part 4 is set to be weaker than the biasing force of the plunger biasing part 3.

[0054] 3, the syringe 5 includes a barrel 50 having an injection needle 503 at its tip, and a plunger 51. The barrel 50 also includes a barrel main body 500 filled with a medicinal liquid, and a cover portion 50A attached to the barrel main body 500.

[0055] The barrel main body 500 is made of transparent resin, glass, etc. The barrel main body 500 includes a barrel tubular portion 501 filled with a drug solution, and an outer flange portion 502 (see FIG. 1 ) protruding radially outward from the other end of the barrel tubular portion 501 in the central axis direction X.

[0056] The barrel cylinder part 501 is cylindrical. As shown in FIG. 3, an injection needle 503 is protruding from one end of the barrel cylinder part 501 in the central axis direction X. Therefore, the injection needle 503 is provided at one end of the barrel 50 in the central axis direction X, which is the tip of the barrel. In this embodiment, the outer diameter of the barrel cylinder part 501 is smaller than the inner diameter of the barrel biasing part 4, which is a compression coil spring. Therefore, as shown in FIG. 1, the barrel cylinder part 501 is inserted into the barrel biasing part 4. In addition, the outer diameter of the barrel cylinder part 501 is smaller than the through hole formed by the biasing base part 20B. Therefore, the barrel main body part 500 is arranged in the barrel housing part 20 with the barrel cylinder part 501 inserted into the through hole.

[0057] As shown in FIG. 3, the cover portion 50A is cylindrical with a part of the outer circumferential surface cut and a bottom surface formed into an approximately C-shape. The cover portion 50A has flat surfaces with one end and the other end in the central axis direction X extending radially and circumferentially. The cover portion 50A has a circular through hole 50B penetrating in the central axis direction X. As shown in FIG. 9, the through hole 50B has an axial movement groove portion 50C formed by cutting out a part of the inner circumferential surface of the cover portion 50A. In this embodiment, two axial movement groove portions 50C, 50C are formed in the second radial direction Y2. Also, as shown in FIGS. 3 and 9, the outer circumferential surface of the cover portion 50A has a cover recess 50D recessed radially inward. The cover recess 50D is provided along the central axis direction X. The cover recess 50D is formed from one end to the other end in the central axis direction X of the cover portion 50A. In this embodiment, a pair of cover recesses 50D, 50D are provided in the cover portion 50A so as to face each other in the first radial direction Y1.

[0058] The cover part 50A is configured to be attachable to the barrel main body part 500. The cover part 50A of this embodiment is attached to the barrel main body part 500 by sliding the outer flange part 502 radially from a part of the cut outer circumferential surface. In addition, in a state where the cover part 50A is attached to the barrel main body part 500, the through hole 50B of the cover part 50A and the inside of the barrel cylinder part 501 are in communication with each other.

[0059] The outer diameter of the cover part 50A is substantially the same as the inner diameter of the barrel other-side accommodating part 200. Therefore, the cover part 50A is configured to be able to be accommodated in the barrel other-side accommodating part 200. Here, as shown in FIG. 9, the cover part 50A is accommodated in the barrel other-side accommodating part 200 with the cover recess 50D of the cover part 50A engaged with the barrel protrusion 20A of the barrel other-side accommodating part 200.

[0060] 1, the length of the cover part 50A in the central axis direction X is shorter than the length of the barrel other-side accommodating part 200 in the central axis direction X. Therefore, the cover part 50A is movable in the barrel other-side accommodating part 200 in the central axis direction X.

[0061] Here, the outer diameter of the cover part 50A is larger than the outer diameter of the barrel biasing part 4, which is a compression coil spring. Therefore, when the barrel 50 is disposed in the barrel housing part 20, the barrel biasing part 4 abuts against one end of the cover part 50A in the central axial direction X. Therefore, the cover part 50A stops the biasing of the barrel biasing part 4 from the other side in the central axial direction X. Therefore, as shown in Figs. 11 and 17, the cover part 50A moves to one side in the central axial direction X by resisting the biasing force of the barrel biasing part 4, and moves to the other side in the central axial direction X by the biasing force of the barrel biasing part 4.

[0062] Incidentally, the outer diameter of the cover part 50A is larger than the inner diameter of the barrel-first accommodating part 201 and the inner diameter of the partition part 21. Thus, the cover part 50A is configured to abut against the barrel step part 20D when it moves to one side in the central axial direction X in the barrel-second accommodating part 200, and to abut against one end of the partition part 21 in the central axial direction X when it moves to the other side in the central axial direction X.

[0063] The length of the barrel 50 in the central axis direction X is shorter than the length of the barrel housing part 20 in the central axis direction X. Therefore, in the state shown in FIG. 1, the barrel 50 (specifically, the cover part 50A) is biased to the other side in the central axis direction X by the biasing force of the barrel biasing part 4, and the injection needle 503 is housed in the housing 2. This state is referred to as a first state. On the other hand, in the state shown in FIG. 11, the barrel 50 (specifically, the cover part 50A) resists the biasing force of the barrel biasing part 4, so that the injection needle 503 protrudes from one side in the central axis direction X of the housing 2. This state is referred to as a second state. That is, the barrel 50 is movable between the first state and the second state.

[0064] The plunger 51 is inserted into the barrel 50. As shown in Fig. 3, the plunger 51 includes a piston 51A and a plunger body 510 that is engaged with the piston 51A.

[0065] Piston 51A serves to prevent the liquid medicine in barrel 50 from leaking out of barrel 50, and to push the liquid medicine out of barrel 50 from injection needle 503. Piston 51A is disposed in barrel tubular portion 501, and is in close contact with the entire inner circumferential surface of barrel tubular portion 501.

[0066] The plunger body 510 includes a rod 511 and a plunger base portion 513 disposed on the other side in the central axis direction X relative to the rod 511.

[0067] As shown in Fig. 3, the rod 511 is a member extending along the central axis direction X. The diameter of the rod 511 is smaller than the inner diameter of the barrel tubular portion 501 and the through hole 50B of the cover portion 50A. Therefore, the rod 511 is configured to be insertable into the barrel 50. Therefore, as shown in Fig. 1, the plunger 51 is inserted into the barrel 50 in a state in which it can reciprocate on one side and the other side of the central axis direction X of the barrel 50.

[0068] As shown in Fig. 3, an axial movement protrusion 512 is formed on the outer circumferential surface of the rod 511 so as to protrude outward. The axial movement protrusion 512 extends from one end of the rod 511 in the central axial direction X toward the other end. The axial movement protrusion 512 is configured so as to be able to be fitted into the axial movement groove 50C. In this embodiment, a pair of axial movement protrusions 512, 512 are formed in the second radial direction Y2.

[0069] 9, with the axial movement protrusion 512 fitted in the axial movement groove 50C, the rod 511 is inserted into the through hole 50B, so that the plunger body 510 is inserted into the barrel 50 in a state in which it cannot rotate around the central axis O. Note that, as shown in FIG. 1, one end of the rod 511 in the central axis direction X abuts against the other end of the piston 51A in the central axis direction X.

[0070] 3, the plunger base 513 is disposed on the other side in the central axis direction X of the rod 511. The plunger base 513 in this embodiment has a larger diameter than the rod 511. The plunger base 513 includes a plunger engagement portion 514 and a trigger engagement portion 515.

[0071] 4, the plunger engagement portion 514 is connected to the other end of the rod 511 in the central axial direction X. In this embodiment, the plunger engagement portion 514 is a member having a larger diameter than the rod 511.

[0072] A groove portion 51a recessed radially inward is formed on the outer peripheral surface of the plunger engagement portion 514. As shown in Figs. 4 and 5, the groove portion 51a of this embodiment includes an axial groove portion 51b extending in the central axial direction X and a circumferential groove portion 51c extending in the circumferential direction. The axial groove portion 51b is provided in the plunger engagement portion 514 so as to extend from one end of the plunger engagement portion 514 in the central axial direction X to the other side. This axial groove portion 51b extends along the central axial direction X. As shown in Figs. 4 and 5, the circumferential groove portion 51c is provided in the plunger engagement portion 514 so as to extend along the circumferential direction. The circumferential groove portion 51c includes a circumferential one end 51d which is one end in the circumferential direction and a circumferential other end 51e which is the other end in the circumferential direction. The circumferential groove portion 51c is disposed on the other side in the central axial direction X than the axial groove portion 51b, and is continuous with the axial groove portion 51b in the central axial direction X. Specifically, one circumferential end 51d of the circumferential groove portion 51c is continuous with the shaft groove portion 51b.

[0073] As shown in Figs. 3 and 4, the trigger engagement portion 515 is a member configured such that the other side in the central axis direction X is bifurcated. The trigger engagement portion 515 is configured to be able to bend so that the bifurcated portions approach each other. The bent trigger engagement portion 515 is configured to return to its original state. Thus, the trigger engagement portion 515 is configured to be elastically deformable. A rib 516 that protrudes radially outward is formed at the other end of the trigger engagement portion 515 in the central axis direction X. The rib 516 is configured in a tapered shape such that the amount of protrusion radially outward increases as it progresses from the other side in the central axis direction X to one side. One end of the rib 516 in the central axis direction X is a flat surface along the radial direction.

[0074] The trigger engagement portion 515 is configured to be insertable into a through hole formed by the trigger mount 231. Specifically, the rib 516 abuts against the inner circumferential surface of the trigger mount 231, and the bifurcated portions of the trigger engagement portion 515 are deflected to approach each other, so that the trigger engagement portion 515 is inserted into the through hole formed by the trigger mount 231, as shown in Fig. 1. Then, the trigger engagement portion 515 returns to its original state by elastic force, and one end of the rib 516 in the central axis direction X abuts against the trigger mount 231 from the other side in the central axis direction X.

[0075] The distance between the bifurcated portions of trigger engagement portion 515 is longer than the width of flat plate portion 23G. Therefore, flat plate portion 23G can be inserted between the bifurcated portions of trigger engagement portion 515. In FIG. 1, flat plate portion 23G is disposed between the bifurcated portions of trigger engagement portion 515.

[0076] 6, the engaging member 6 is configured in an annular shape. The engaging member 6 includes a cylindrical engaging body 60, an engaging ring 61, and an elastic body 62. The engaging body 60 of this embodiment includes an engaging annular portion 600 and an engaging cylindrical portion 601.

[0077] As shown in Fig. 6, the engaging annular portion 600 is an annular member. As shown in Fig. 7, in the engaging annular portion 600 of this embodiment, one end and the other end in the central axis direction X are flat surfaces. The inner diameter of the engaging annular portion 600 is larger than the plunger main body 510. On the other hand, the outer diameter of the engaging annular portion 600 is smaller than the inner diameter of the plunger other-side accommodating portion 221.

[0078] The engaging annular portion 600 is formed with a radially inwardly protruding portion 60a. The radially inwardly protruding portion 60a is configured to be insertable into the groove portion 51a of the plunger engaging portion 514. As shown in FIG. 6, the engaging annular portion 600 of this embodiment is provided with a plurality of (specifically, two) radially inwardly protruding portions 60a in the circumferential direction. In addition, a fixing portion for fixing one end of the plunger biasing portion 3 in the central axial direction X is provided at the other end of the engaging annular portion 600 in the central axial direction X. The fixing portion in this embodiment is an insertion hole 60b into which one end of the plunger biasing portion 3 in the central axial direction X can be inserted. In addition, an annular recess 60A that can be recessed and fitted into the plunger accommodating protrusion 22A is formed on the outer circumferential surface of the engaging annular portion 600. A pair of the annular recesses 60A is provided in each of the first radial direction Y1 and the second radial direction Y2.

[0079] The engagement tubular portion 601 is cylindrical. As shown in Fig. 7, the engagement tubular portion 601 is connected to the engagement annular portion 600 from one side in the central axis direction X. The inner diameter of the engagement tubular portion 601 is approximately the same as the inner diameter of the engagement annular portion 600. Therefore, the plunger body 510 can be inserted into the engagement body 60. The outer diameter of the engagement tubular portion 601 is smaller than the outer diameter of the engagement annular portion 600.

[0080] As shown in FIG. 7, the flange 602 is provided on the outer peripheral surface of the engagement tube 601 and protrudes radially outward. The flange 602 in this embodiment is disposed on one side of the central axis direction X of the engagement tube 601. The flange 602 is configured in a stepped shape with one side in the central axis direction X located radially outward than the other side. Therefore, the flange 602 in this embodiment has the largest outer diameter at one end in the central axis direction X. In addition, the other end and one end of the flange 602 in the central axis direction X are flat surfaces that extend radially and circumferentially. Furthermore, the outer diameter of one end of the flange 602 in the central axis direction X is approximately the same as the outer diameter of the engagement ring portion 600. Therefore, the engagement main body 60 can be accommodated in the plunger other end accommodating portion 221.

[0081] The flange portion 602 has an outer peripheral surface provided with a flange recess 60B that can be fitted to the plunger accommodating protrusion 22A. The flange recess 60B is provided at one end of the flange portion 602 in the central axis direction X where the outer diameter is the largest. The flange recess 60B is disposed at approximately the same position as the annular recess 60A in the circumferential direction. Therefore, a pair of flange recesses 60B are provided in each of the first radial direction Y1 and the second radial direction Y2. In this embodiment, the flange recess 60B and the annular recess 60A constitute a main body engaging portion 60C that can be engaged with the plunger accommodating engaging portion.

[0082] The engagement ring 61 is an annular member. One end and the other end of the engagement ring 61 in the central axis direction X are flat surfaces. The inner diameter of the engagement ring 61 is larger than the outer diameter of the engagement tube portion 601. Therefore, as shown in FIG. 7, the engagement ring 61 is arranged on the outer circumferential surface of the engagement body 60 in a state where it is fitted onto the engagement tube portion 601. Specifically, the engagement ring 61 is arranged between the engagement annular portion 600 and the flange portion 602 in the central axis direction X. Therefore, the length of the engagement ring 61 in the central axis direction X is shorter than the length of the engagement tube portion 601 in the central axis direction X. The outer diameter of the engagement ring 61 is approximately the same as the outer diameter of the engagement annular portion 600 and the outer diameter of one end of the flange portion 602 in the central axis direction X of the engagement body 60. The outer circumferential surface of the engagement ring 61 is provided with a ring protrusion 61A configured to be able to be fitted into the plunger accommodating recess 22B, and a ring recess 61B configured to be able to be fitted into the plunger accommodating recess 22A. As shown in Fig. 6, the ring recess 61B is disposed at substantially the same position as the main body engagement portion 60C in the circumferential direction. Therefore, a pair of ring recesses 61B is provided in each of the first radial direction Y1 and the second radial direction Y2.

[0083] The elastic body 62 is configured to be elastically deformable in the circumferential direction. The elastic body 62 in this embodiment is an O-ring configured in an annular shape. Specifically, the elastic body 62 in this embodiment is configured of oil-bleed silicone rubber obtained by kneading oil into silicone rubber. Note that the elastic body 62 may be configured of a material similar to oil-bleed silicone rubber, such as fluororubber, nitrile rubber, or silicone rubber.

[0084] The elastic body 62 is disposed between the engagement body 60 and the engagement ring 61. In this embodiment, the elastic body 62 is disposed between the engagement body 60 and the engagement ring 61 in the central axial direction X. Specifically, the elastic body 62 is disposed between one end of the engagement annular portion 600 in the central axial direction X and the other end of the engagement ring 61 in the central axial direction X, and between one end of the engagement ring 61 in the central axial direction X and the other end of the flange portion 602 in the central axial direction X. Thus, in this embodiment, two elastic bodies 62, 62 are disposed between the engagement body 60 and the engagement ring 61 on one side and the other side of the central axial direction X. Also, the elastic body 62 abuts against the engagement body 60 and the engagement ring 61.

[0085] The length of the engaging member 6 in the central axis direction X is shorter than the distance between the partition portion 21 and the plunger accommodating protrusion 22A in the central axis direction X. The radial length of the engaging member 6 is larger than the inner diameter of the partition portion 21.

[0086] The engagement member 6 is engaged with the plunger engagement portion 514. Specifically, when the plunger base portion 513 is inserted into the engagement member 6, the radially inner protrusion 60a is inserted into the groove portion 51a, whereby the engagement member 6 is engaged with the plunger engagement portion 514. In this embodiment, after the radially inner protrusion 60a inserted into the shaft groove portion 51b is moved to the circumferential groove portion 51c, the engagement member 6 and the plunger body 510 are rotated relatively around the central axis O. Specifically, the engagement body 60 is rotated around the central axis O with respect to the plunger 51. As a result, as shown in FIG. 8, the radially inner protrusion 60a is disposed on the other circumferential end 51e side of the circumferential groove portion 51c. Therefore, the engagement member 6 is engaged with the plunger 51.

[0087] As shown in FIG. 1, the engagement member 6 engaged with the plunger 51 is accommodated in the plunger accommodating portion 22. The engagement member 6 compresses the plunger biasing portion 3 in the central axis direction X in a state where the twist is not released. Here, the plunger biasing portion 3 is inserted at the other end in the central axis direction X into an insertion hole provided in the trigger mounting base portion 231 in a state where it is twisted around the central axis O, and at one end in the central axis direction X into an insertion hole 60b of the engagement annular portion 600. On the other hand, the engagement member 6 is accommodated in the plunger other accommodating portion 221 in a state where the main body engagement portion 60C of the engagement main body 60 and the ring recessed portion 61B of the engagement ring 61 are engaged with the plunger accommodating protrusion 22A of the plunger other accommodating portion 221, and the ring protrusion 61A of the engagement ring 61 is engaged with the plunger accommodating recessed portion 22B of the plunger other accommodating portion 221. Therefore, the engagement member 6 cannot rotate around the central axis O, and prevents the torsion of the plunger biasing portion 3 from being released. In addition, the engagement member 6 moves to the other side of the central axis direction X in the plunger other-side accommodation portion 221, whereby the engagement member 6 and the trigger mount portion 231 compress the plunger biasing portion 3 in the central axis direction X. Furthermore, the trigger engagement portion 515 is inserted into the through hole formed by the trigger mount portion 231, whereby the rib 516 abuts against the trigger mount portion 231 from the other side of the central axis direction X, as shown in FIG. 1. Therefore, the engagement member 6 holds the plunger biasing portion 3 in a state twisted around the central axis O and compressed in the central axis direction X.

[0088] Furthermore, in a state in which the engaging member 6 is accommodated in the plunger other-side accommodating portion 221, the elastic body 62 is disposed in a state spaced apart from the inner circumferential surface of the plunger other-side accommodating portion 221 in the radial direction.

[0089] The above is a description of the configuration of the injection device 1 according to the first embodiment. Next, a method of using this injection device 1 will be described.

[0090] As shown in FIG. 1, the injection device 1 of this embodiment is in an initial state before use. In this initial state, the injection needle 503 is housed in the housing 2. Thus, the barrel 50 is in a first state. In the initial state, a cap (not shown) is attached to one side of the housing 2 in the central axial direction X so that the injection needle 503 does not protrude outside the housing 2. Therefore, when using the injection device 1, first, the cap is removed from the housing 2.

[0091] Next, the injection needle 503 is protruded from one side of the central axis direction X of the housing 2, and the barrel 50 is moved from the first state to the second state. Thus, the lock of the trigger portion 23 is released, and the trigger body portion 23A is pushed into one side of the central axis direction X. Specifically, the trigger lock operation portion 23a and the trigger body portion 23A are rotated about the central axis direction X with respect to the trigger mounting portion 230, and the release groove 23D and the lock step portion 233 are arranged at positions that coincide with each other in the circumferential direction. Here, with the rotation of the trigger body portion 23A about the central axis direction X, the thickness of the flat plate portion 23G is arranged in a direction that matches the direction in which the bifurcated portions of the trigger engagement portion 515 face each other. Therefore, the trigger engagement portion 515 can bend so that the bifurcated portions approach each other. Then, the trigger body portion 23A is pushed into one side of the central axis direction X. As a result, the lock step portion 233 is inserted into the release groove 23D, and the inner skirt portion 23F comes into contact with the rib 516. This causes the bifurcated portions of the trigger engagement portion 515 to bend toward each other, releasing the engagement between the plunger 51 and the trigger portion 23. This releases the bias of the plunger biasing portion 3 that has been held in a compressed state.

[0092] As shown in FIG. 11, the engagement member 6 and the syringe 5 having the plunger 51 engaged with the engagement member 6 are moved to one side in the central axis direction X by the urging force of the released plunger urging portion 3. Here, the urging force of the barrel urging portion 4 is set to be weaker than the urging force of the plunger urging portion 3. Therefore, the urging force of the plunger urging portion 3 causes the syringe 5 to move to one side in the central axis direction X while compressing the barrel urging portion 4 via the engagement member 6. Specifically, the barrel 50 moves to one side in the central axis direction X until the cover portion 50A abuts against the barrel step portion 20D while compressing the barrel urging portion 4. That is, the barrel urging portion 4 is compressed by the plunger urging portion 3 via the syringe 5. The cover recess 50D and the barrel protrusion 20A are engaged with each other. Therefore, the barrel 50 is prevented from rotating around the central axis direction X. Then, as the syringe 5 moves to one side in the central axis direction X, the injection needle 503 protrudes outward from the one side in the central axis direction X of the housing 2. Thus, the barrel 50 moves from the first state to the second state. Then, when the cover portion 50A comes into contact with the barrel step portion 20D, the movement of the barrel 50 to one side in the central axis direction X is restricted.

[0093] The engaging member 6 and the plunger 51 move further to one side in the central axis direction X by the biasing force of the plunger biasing portion 3. Specifically, as shown in Figs. 11 and 12, the plunger 51 moves inside the barrel 50, starting from the other side in the central axis direction X, which is the base end side of the barrel 50, and ending from one side in the central axis direction X, which is the injection needle 503 side. Thus, as the plunger 51 moves inside the barrel 50, the piston 51A pushes the liquid medicine from the injection needle 503 to the outside of the barrel 50. Thus, the liquid medicine in the barrel 50 can be discharged. The piston 51A moves to the tip, which is one end of the barrel 50 in the central axis direction X.

[0094] Here, the plunger biasing part 3 of this embodiment biases the syringe 5 and the engagement member 6 from the other side in the central axis direction X to one side, and also biases them to rotate around the central axis O. The other end of the plunger biasing part 3 in the central axis direction X is inserted from one side in the central axis direction X into an insertion hole provided in the trigger mounting base part 231. Also, as shown in Figs. 8 and 10, one end of the plunger biasing part 3 in the central axis direction X is inserted into the insertion hole 60b. On the other hand, the annular recess 60A and the flange recess 60B are recessed and recessed into the plunger accommodating protrusion 22A. Therefore, the engagement main body 60 cannot rotate around the central axis O. Therefore, in a state in which the main body engaging part 60C and the plunger accommodating engaging part are engaged, the torsion of the plunger biasing part 3 is not released, and the engaging member 6 moves to one side in the central axis direction X within the plunger other accommodating part 221 without rotating around the central axis O. As shown in FIGS. 8 and 10, the ring recess 61B and the plunger accommodating protrusion 22A, and the ring protrusion 61A and the plunger accommodating recess 22B also fit together.

[0095] 9, the axial movement protrusion 512 is fitted into the axial movement groove 50C. Therefore, the plunger 51 is configured to be unable to rotate around the central axis O. Therefore, the plunger body 510 also moves to one side in the central axis direction X within the plunger accommodating portion 22 without rotating around the central axis O. Therefore, as shown in FIG. 8, the engaging member 6 and the plunger body 510 move to one side in the central axis direction X while the radial inner protrusion 60a and the groove 51a remain engaged with each other.

[0096] As described above, the length of the engagement member 6 in the central axis direction X is shorter than the separation distance between the partition portion 21 and the plunger accommodating protrusion 22A in the central axis direction X. As shown in Figs. 12 and 13, when the engagement member 6 and the plunger body 510 move to one side in the central axis direction X until the piston 51A moves to one end in the central axis direction X, which is the end point of the barrel 50, the engagement member 6 is disposed between the partition portion 21 and the plunger accommodating protrusion 22A. In addition, the concave-convex fit between the annular recess 60A, the flange recess 60B, and the ring recess 61B and the plunger accommodating protrusion 22A is released. That is, the engagement between the body engagement portion 60C and the plunger accommodating portion is released. Therefore, the engagement body 60 becomes rotatable around the central axis O, and the torsion of the plunger biasing portion 3 can be released.

[0097] On the other hand, even after the plunger body 510 moves to one side in the central axis direction X, the axial movement protrusion 512 remains fitted in the axial movement groove 50C. Also, as shown in Fig. 13, the ring protrusion 61A remains recessed and fitted in the plunger accommodating recess 22B. Therefore, while the engagement body 60 becomes rotatable around the central axis O, the engagement ring 61 and the plunger body 510 remain unable to rotate around the central axis O.

[0098] 13 and 15, one end of the plunger biasing portion 3 in the central axis direction X is fixed to the fixed portion of the engagement ring portion 600. Specifically, one end of the plunger biasing portion 3 in the central axis direction X is inserted into the insertion hole 60b. Therefore, when the engagement between the main body engagement portion 60C and the plunger accommodating portion is released, the engagement main body 60 is biased to rotate around the central axis O by the torsion of the released plunger biasing portion 3. Therefore, the engagement main body 60 transitions from the pre-rotation state shown in FIGS. 12 and 13 to the post-rotation state shown in FIGS. 14 and 15.

[0099] On the other hand, as described above, the engagement ring 61 and the plunger body 510 remain non-rotatable about the central axis O. Therefore, the engagement body 60 rotates about the central axis O relative to the non-rotatable engagement ring 61 and plunger body 510. Therefore, in this embodiment, the engagement body 60 is configured as an engagement rotating part that rotates about the central axis O relative to the plunger 51, and the engagement ring 61 is configured as an engagement non-rotating part that does not rotate about the central axis O relative to the engagement rotating part.

[0100] Here, as shown in FIG. 12, the elastic body 62 is disposed between the engagement body 60 and the engagement ring 61 in a state where it is in contact with the engagement body 60 and the engagement ring 61. Therefore, the engagement body 60 rotates around the central axis O while elastically deforming the elastic body 62 in the circumferential direction. In addition, the elastic force of the elastic body 62 acts on the engagement body 60 and the engagement ring 61, and the engagement body 60 rotates around the central axis O while receiving the elastic force of the elastic body 62 in the elastically deformed state. Therefore, the elastic force of the elastic body 62 becomes a rotational resistance, which is a resistance force in the opposite direction to the direction in which the engagement body 60 rotates, and the rotational speed of the engagement body 60 is suppressed by this rotational resistance. Therefore, the elastic body 62 is disposed between the engagement rotating portion and the engagement non-rotating portion, and is configured as a rotation suppressing portion that suppresses the rotational speed of the engagement rotating portion relative to the engagement non-rotating portion.

[0101] 12, in this embodiment, two elastic bodies 62, 62 are disposed between the engagement body 60 and the engagement ring 61 on one side and the other side in the central axial direction X. Therefore, the engagement body 60 in this embodiment rotates around the central axis O while receiving rotational resistance from the elastic bodies 62 on one side and the other side in the central axial direction X.

[0102] Furthermore, by suppressing the rotation speed of the engagement body 60, the movement of the radially inner protrusion 60a from the other circumferential end 51e side to the one circumferential end 51d side in the circumferential groove portion 51c becomes slow. Therefore, while the radially inner protrusion 60a continues to move in the circumferential groove portion 51c, the engagement state between the engagement member 6 and the plunger 51 is maintained. Thus, the state in which the injection needle 503 protrudes from the housing 2 is maintained. In this embodiment, the state in which the injection needle 503 protrudes from the housing 2 is maintained for 3 to 5 seconds.

[0103] Therefore, a rotation suppression mechanism is configured that suppresses the rotation speed about the central axis O of the engagement member 6 relative to the plunger 51. In this embodiment, the rotation suppression mechanism includes the engagement ring 61 which is an engagement non-rotating part, and the elastic body 62 which is a rotation suppression part, and suppresses the rotation speed of the engagement main body 60 relative to the engagement ring 61.

[0104] 16, when the radially inner protrusion 60a moves toward one circumferential end 51d of the circumferential groove 51c, the shaft groove 51b and the radially inner protrusion 60a are arranged at the same position in the circumferential direction, and thus the engagement between the engagement member 6 and the plunger body 510 is released.

[0105] By releasing the engagement between the engagement member 6 and the plunger main body 510, the urging force of the plunger urging part 3 against the syringe 5 is released. Therefore, the barrel urging part 4 compressed by the plunger urging part 3 through the syringe 5 is released. Therefore, as shown in FIG. 17, the barrel urging part 4 urges the syringe 5 to the other side in the central axis direction X. Here, as shown in FIG. 16, in a state in which the engagement between the engagement member 6 and the plunger 51 is released, the radial inner protrusion 60a and the shaft groove 51b are arranged in a state of being aligned in the circumferential direction. Therefore, while the shaft groove 51b moves to the other side in the central axis direction X relative to the radial inner protrusion 60a, the syringe 5 moves to the other side in the central axis direction X. Therefore, as shown in FIG. 17, the barrel 50 can be moved from the second state to the first state, and the injection needle 503 can be housed in the housing 2. When the cover portion 50A comes into contact with the partition portion 21 from one side in the central axis direction X, the syringe 5 stops.

[0106] 14, 15, and 16, when the barrel 50 is accommodated in the barrel accommodation portion 20 with the injection needle 503 protruding from one side of the central axis direction X of the housing 2, and the plunger 51 is positioned at the end point by the biasing force of the plunger biasing portion 3, the plunger 51 and the engaging member 6 rotate relative to each other around the central axis O, thereby forming a disengagement mechanism for disengaging the plunger 51 and the engaging member 6. In this embodiment, the engagement body 60 rotates relative to the plunger body 510 due to the twisting of the plunger biasing portion 3, and the radially inner protrusion 60a and the shaft groove portion 51b are positioned at a position where they coincide in the circumferential direction. Thus, the engagement between the plunger body 510 and the engaging member 6 is released. Therefore, in this embodiment, the plunger biasing portion 3, which biases the engagement body 60 to rotate around the central axis O, and the shaft groove portion 51b form the disengagement mechanism.

[0107] As described above, according to this embodiment, when the engagement body 60 rotates around the central axis O relative to the plunger body 510, the elastic force of the elastic body 62 acts as a rotational resistance to suppress the rotational speed of the engagement body 60, so that the time until the engagement between the engagement member 6 and the plunger 51 is released can be extended. Therefore, the injection needle 503 that has discharged the liquid medicine can be maintained in a state protruding from the housing 2. In this embodiment, the injection needle 503 can be maintained in a state protruding from the housing 2 for 3 to 5 seconds. Therefore, for example, it is possible to prevent the injection needle 503 that has been punctured into the patient's skin from coming out of the skin, and the liquid medicine from leaking from the puncture site.

[0108] In this embodiment, the plunger 51 is configured to be unable to rotate around the central axis O, the engagement body 60 is configured to be rotatable around the central axis O, the plunger biasing unit 3 applies a biasing force to the engagement body 60 to rotate around the central axis O, the disengagement mechanism rotates the engagement body 60 relative to the plunger 51 due to the biasing force of the plunger biasing unit 3 to disengage the engagement body 60 from the plunger 51, and the rotation suppression mechanism suppresses the rotation speed of the engagement body 60 due to the biasing force of the plunger biasing unit 3 to rotate around the central axis O. Thus, by the rotation suppression mechanism suppressing the rotation speed of the engagement body 60 relative to the engagement ring 61, the time until the engagement between the engagement body 60 and the plunger 51 is released by the disengagement mechanism can be extended.

[0109] In this embodiment, the plunger accommodating recess 22B is provided over the entire area in the central axis direction X of the plunger other-side accommodating portion 221, and the ring protrusion 61A of the engagement ring 61 is engaged with the plunger accommodating recess 22B. Therefore, the engagement ring 61 cannot rotate around the central axis O. In addition, an elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61. Therefore, it is possible to prevent the engagement ring 61 and the elastic body 62 from rotating together due to the rotation of the engagement main body 60, and it is possible to reliably operate the mechanism for suppressing the rotation speed of the engagement main body 60.

[0110] In addition, the elastic body 62 in this embodiment is made of oil-bleed silicone rubber. Therefore, the oil kneaded into the silicone seeps onto the surface of the elastic body 62, making it possible to adjust the rotation speed of the engagement body 60. As a result, the rotation speed of the engagement body 60 can be appropriately controlled by the elastic body 62.

[0111] In this embodiment, the elastic body 62 is disposed between the engagement body 60 and the engagement ring 61 in the central axial direction X. Therefore, the elastic body 62 does not affect the movement of the syringe 5 or the engagement member 6 to one side in the central axial direction X by the biasing force of the plunger biasing portion 3. Furthermore, in a state in which the engagement member 6 is accommodated in the plunger other accommodating portion 221, the elastic body 62 is disposed in a state spaced apart from the inner circumferential surface of the plunger other accommodating portion 221 in the radial direction. Therefore, when the engagement member 6 moves to one side in the central axial direction X, the elastic body 62 comes into contact with the plunger other accommodating portion 221, and the movement of the engagement member 6 to one side in the central axial direction X can be prevented from being hindered.

[0112] In this embodiment, the engagement ring 61 is disposed between the engagement annular portion 600 and the flange portion 602 in the central axis direction X, and the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axis direction X. This makes it possible to prevent a situation in which the elastic body 62 separates from the engagement main body 60 when the engagement main body 60 rotates around the central axis O, resulting in the rotational speed of the engagement main body 60 not being suppressed.

[0113] In this embodiment, two elastic bodies 62, 62 are disposed between the engagement body 60 and the engagement ring 61 on one side and the other side of the central axial direction X. Therefore, the engagement body 60 in this embodiment rotates around the central axis O while receiving rotational resistance from the elastic bodies 62 on one side and the other side of the central axial direction X. Therefore, the rotational speed of the engagement body 60 can be further suppressed.

[0114] In the present embodiment, one barrel accommodating portion 201 is provided with a through-hole 20C that penetrates in the radial direction. Therefore, the remaining amount of the liquid medicine in barrel 50 accommodated in housing 2 can be confirmed.

[0115] Next, an injection device 1 according to a second embodiment will be described with reference to Figures 18 to 30. In describing the second embodiment, descriptions of the same configuration, method of use, and action as those of the first embodiment will be omitted.

[0116] As shown in Fig. 18, the plunger accommodating engagement portion of the second embodiment includes only the plunger accommodating protrusion 22A. Therefore, the plunger accommodating engagement portion of the second embodiment does not include the plunger accommodating recess 22B. The plunger accommodating protrusion 22A of the second embodiment is formed over the entire area of ​​the central axis direction X of the plunger other accommodating portion 221. The plunger accommodating protrusions 22A are provided in pairs in each of the first radial direction Y1 and the second radial direction Y2.

[0117] The plunger biasing portion 3 in the second embodiment is a compression coil spring wound around the central axis O. Therefore, unlike the first embodiment, the plunger biasing portion 3 in the second embodiment only biases the syringe 5 and the engaging member 6 from the other side to one side in the central axis direction X.

[0118] 19, the plunger body 510 of the second embodiment includes a plunger main body portion 510a, a plunger ring 510b configured in an annular shape, and an elastic body 510c. The plunger main body portion 510a includes a rod 511 and a plunger base portion 513.

[0119] As shown in FIG. 21, the rod 511 is configured such that the middle portion 511a in the central axis direction X has a smaller diameter than the other portions. Therefore, between the middle portion 511a in the central axis direction X and the portions disposed on one side and the other side of the middle portion 511a in the central axis direction X, rod steps 511b and 511c extending in the radial direction are formed. The rod steps 511b and 511c are flat surfaces extending in the radial direction and expanding in the circumferential direction. In addition, as shown in FIG. 19, the axial movement protrusion 512 of the second embodiment is formed on one side of the middle portion 511a in the central axis direction X of the rod 511 in the central axis direction X.

[0120] A plunger ring 510b and an elastic body 510c configured in an annular shape are disposed in a middle portion 511a in the central axis direction X of the rod 511. Therefore, as shown in FIG. 21, the inner diameter of the plunger ring 510b is larger than the outer diameter of the middle portion 511a in the central axis direction X of the rod 511. On the other hand, the outer diameter of the plunger ring 510b is substantially the same as the outer diameter of the portion of the rod 511 other than the middle portion 511a in the central axis direction X. In this embodiment, one end of the plunger ring 510b in the central axis direction X abuts against the rod step portion 511c.

[0121] As shown in Fig. 19, a radially outer protrusion 510d that protrudes radially outward is formed on the outer circumferential surface of the plunger ring 510b. This radially outer protrusion 510d is configured to be the same as the axial movement protrusion 512 formed on the rod 511. Therefore, the radially outer protrusion 510d is configured to be able to be fitted into the axial movement groove 50C. The radially outer protrusion 510d is disposed at approximately the same position as the axial movement protrusion 512 in the circumferential direction. Therefore, the radially outer protrusion 510d is continuous with the axial movement protrusion 512 in the central axis direction X.

[0122] The elastic body 510c is an O-ring that is elastically deformable in the circumferential direction. The elastic body 510c of this embodiment is made of oil-bleed silicone rubber. As in the first embodiment, the elastic body 510c may be made of a material similar to oil-bleed silicone rubber, such as fluororubber, nitrile rubber, or silicone rubber.

[0123] 19 and 21, the elastic body 510c is disposed between the plunger main body 510a and the plunger ring 510b. The elastic body 510c of this embodiment is disposed between the rod 511 and the plunger ring 510b in the central axis direction X. Specifically, the elastic body 510c abuts against the rod step portion 511b and the other end of the plunger ring 510b in the central axis direction X.

[0124] As shown in Fig. 19, the outer peripheral surface of the plunger engagement portion 514 of the second embodiment is formed with a groove portion 51a recessed radially inward, as in the first embodiment. Here, the groove portion 51a of the second embodiment is configured as a helical groove portion 51a extending in the circumferential direction from one end of the plunger engagement portion 514 in the central axial direction X toward the other side. Also, as shown in Fig. 20, the helical groove portion 51a has a one circumferential end 51d which is one end in the circumferential direction and a second circumferential end 51e which is the other end in the circumferential direction. The one circumferential end 51d is disposed on the other side in the central axial direction X, and the other circumferential end 51e is disposed on one side in the central axial direction X.

[0125] 22 and 23, the engaging member 6 of the second embodiment includes only an engaging body 60. Therefore, unlike the first embodiment, the engaging member 6 of the second embodiment does not include an engaging ring 61 and an elastic body 62. Also, the flange portion 602 of the second embodiment has the same protruding amount on one side and the other side in the central axis direction X. Furthermore, the inner diameter protruding portion 60a of the second embodiment is configured to be insertable into the spiral groove portion 51a.

[0126] As shown in Fig. 24, the engagement member 6 engages with the plunger engagement portion 514. In this embodiment, the engagement member 6 and the plunger body 510 rotate relatively around the central axis O such that the inner radial protrusion 60a inserted into the spiral groove portion 51a from one side in the central axis direction X moves from the other circumferential end 51e side to the one circumferential end 51d side. As a result, as shown in Fig. 25, the inner radial protrusion 60a is disposed on the one circumferential end 51d side of the spiral groove portion 51a.

[0127] As described above, the plunger biasing portion 3 of the second embodiment only biases the syringe 5 and the engaging member 6 from the other side to one side in the central axial direction X. Therefore, as shown in Fig. 24, the engaging member 6 accommodated in the plunger other accommodating portion 221 compresses the plunger biasing portion 3 in the central axial direction X. Furthermore, as shown in Fig. 25, the engaging member 6 is accommodated in the plunger other accommodating portion 221 with the main body engaging portion 60C of the engaging main body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221 engaged with each other.

[0128] Next, a method of using the injection device 1 of the second embodiment will be described. Here, in describing a method of using the injection device 1 of the second embodiment, the process from the initial state until the injection needle 503 protrudes is the same as that of the first embodiment. Therefore, a description of this part will be omitted.

[0129] 26 and 27, when piston 51A has moved to the tip, which is one end in the central axis direction X of barrel 50, radially outer protrusion 510d is fitted into axial movement groove 50C. Therefore, plunger ring 510b is configured not to rotate around central axis O.

[0130] On the other hand, the engaging member 6 is about to move further to one side in the central axis direction X due to the biasing force of the plunger biasing portion 3. Here, in the second embodiment, the plunger accommodating protrusion 22A is formed over the entire area of ​​the central axis direction X of the plunger other accommodating portion 221, and the main body engaging portion 60C of the engaging body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221 are engaged with each other in a concave-convex manner. Therefore, the engaging member 6 cannot rotate around the central axis O. Therefore, while the radially inner protruding portion 60a moves from the circumferential one end 51d side of the spiral groove portion 51a to the circumferential other end 51e side, the engaging member 6 that cannot rotate around the central axis O moves to one side in the central axis direction X. Therefore, the plunger main body 510 rotates around the central axis O by the engaging member 6 moving to one side in the central axis direction X. The plunger main body 510 of this embodiment rotates counterclockwise around the central axis O.

[0131] When the plunger body 510 rotates, the rod 511 rotates around the central axis O relative to the plunger ring 510b configured to be non-rotatable. Therefore, in this embodiment, the plunger body 510a is configured as a plunger rotating part that rotates around the central axis O relative to the engagement member 6, and the plunger ring 510b is configured as a plunger non-rotating part that does not rotate around the central axis relative to the plunger rotating part.

[0132] Here, as shown in FIG. 26, the elastic body 510c is disposed between the plunger main body 510a and the plunger ring 510b. The elastic body 510c is in contact with the rod step 511b and the other end of the plunger ring 510b in the central axis direction X. Therefore, as shown in FIG. 28, the plunger main body 510a rotates around the central axis O while elastically deforming the elastic body 510c in the circumferential direction. In addition, the elastic force of the elastic body 510c acts on the plunger main body 510a and the plunger ring 510b, and the plunger main body 510a rotates around the central axis O while receiving the elastic force of the elastic body 510c in the elastically deformed state. Therefore, the elastic force of the elastic body 510c becomes a rotational resistance, which is a resistance force in the opposite direction to the direction in which the plunger main body 510a rotates, and this rotational resistance suppresses the rotational speed of the plunger main body 510a. Therefore, the elastic body 510c is disposed between the plunger rotating portion and the plunger non-rotating portion, and is configured as a rotation suppressing portion that suppresses the rotation speed of the plunger rotating portion relative to the plunger non-rotating portion.

[0133] By suppressing the rotation speed of the plunger body 510a, the movement of the radially inner protrusion 60a from the one circumferential end 51d side to the other circumferential end 51e side of the helical groove 51a becomes slow. Therefore, while the radially inner protrusion 60a continues to move in the helical groove 51a, the state in which the engagement member 6 and the plunger 51 are engaged is maintained. Therefore, the state in which the injection needle 503 protrudes from the housing 2 is maintained.

[0134] Therefore, a rotation suppression mechanism is configured to suppress the rotation speed of the plunger 51 about the central axis O relative to the engagement member 6. In this embodiment, the rotation suppression mechanism includes the plunger ring 510b which is the plunger non-rotating portion, and the elastic body 510c which is the rotation suppression portion, and suppresses the rotation speed of the rod 511 relative to the plunger ring 510b. Therefore, the rotation suppression mechanism suppresses the rotation speed of the plunger 51.

[0135] When the inner diameter protrusion 60a moves to the other circumferential end 51e of the spiral groove portion 51a, the inner diameter protrusion 60a is disposed at one end in the central axis direction X of the plunger engagement portion 514. Thus, the engagement between the inner diameter protrusion 60a and the spiral groove portion 51a is released. Therefore, the disengagement mechanism of the second embodiment is configured to release the engagement between the plunger 51 and the engagement member 6 by rotating the plunger 51 (specifically, the plunger main body portion 510a which is the plunger rotating portion) about the central axis O relative to the engagement member 6 and releasing the engagement between the engagement member 6 and the plunger main body portion 510a.

[0136] By releasing the engagement between the plunger 51 and the engaging member 6, the barrel biasing part 4 compressed by the plunger biasing part 3 is released. Therefore, as shown in FIG. 30, the syringe 5 moves to the other side in the central axis direction X by the biasing force of the barrel biasing part 4. Therefore, the injection needle 503 is accommodated in the housing 2.

[0137] As described above, according to this embodiment, the rotation speed of the plunger 51 is suppressed, and the time until the engagement between the plunger 51 and the engaging member 6 is released can be extended. Therefore, the injection needle 503 that has discharged the medicinal liquid can be maintained in a state protruding from the housing 2.

[0138] In this embodiment, the radially outer protruding portion 510d is inserted into the axial movement groove portion 50C, so that the plunger body portion 510a rotates around the central axis line O relative to the plunger ring 510b. At that time, the rotation speed of the rod 511 can be suppressed by the elastic force of the elastic body 510c disposed between the plunger body portion 510a and the plunger ring 510b.

[0139] In this embodiment, the engaging member 6 moves to one side in the central axial direction X due to the biasing force of the plunger biasing portion 3, and the radially inner protruding portion 60a moves to one side in the central axial direction X along the helical groove portion 51a, thereby rotating the plunger body 510 around the central axis O. Therefore, the biasing force of the plunger biasing portion 3 to one side in the central axial direction X is changed to a rotational force that rotates the plunger 51, thereby rotating the plunger 51.

[0140] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the invention.

[0141] In the second embodiment, the rotation of the engagement body 60 about the central axis O is restricted by the recess 60A of the engagement body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221 engaging with each other in a concave-convex manner. However, this is not limited thereto, and for example, the engagement body 60 may be provided with an annular recess 60A protruding radially outward from the engagement body 60, and may be engaged with the plunger accommodating recess 22B of the plunger other accommodating portion 221 in a concave-convex manner to restrict the rotation of the engagement body 60 about the central axis O.

[0142] In the above embodiment, the engaging member 6 includes an engaging rotation portion and an engaging non-rotating portion. However, the present invention is not limited to this, and the engaging member 6 may include only an engaging rotation portion. For example, the engaging member 6 may not include the engaging ring 61 and the elastic body 62, and the partition portion 21 may include an elastic body on the other side of the central axis direction X, and the engaging body 60 may be configured to abut against the elastic body of the partition portion 21 when the concave-convex fit between the annular recess 60A of the engaging body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221 is released. In this case, the engaging body 60 abuts against the elastic body in the central axis direction X.

[0143] In the above embodiment, the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axis direction X. However, this is not limiting, and for example, the elastic body 62 may be disposed between the engagement main body 60 and the engagement ring 61 in the radial direction. The same applies to the elastic body 510c of the second embodiment.

[0144] For example, the time during which the injection needle 503 can be maintained in a state where it protrudes from the housing 2 may be changed by changing the circumferential length of the circumferential groove portion 51c formed in the plunger engagement portion 514.

[0145] In the above embodiment, the barrel biasing portion 4 and the plunger biasing portion 3 are compression coil springs. However, the present invention is not limited to this and may be made of, for example, rubber that is elastically deformable so as to extend in the central axis direction X.

[0146] In the above embodiment, one of the engaging member 6 and the plunger 51 is fixed so as not to rotate around an axis, and the other is configured to be rotatable around an axis, and the other is configured to rotate relative to the other. However, this is not limited thereto, and for example, both the engaging member 6 and the plunger 51 may be configured to rotate around the central axis O.

[0147] In the above embodiment, the case has been described where the starting point is at a position on one side of the other end in the central axial direction X of the barrel 50, and the end point is at one end in the central axial direction X of the barrel 50. However, this is not limiting, and for example, the starting point may be at the other end in the central axial direction X of the barrel 50. Also, the end point may be at the other side of the one end in the central axial direction X of the barrel 50. In other words, as long as the starting point is at the other side in the central axial direction X of the barrel 50 and the end point is at one side in the central axial direction X of the barrel 50, the starting point may be set at a position other than the other end in the central axial direction X of the barrel 50 and the end point may be set at a position other than the one end in the central axial direction X of the barrel 50. [Explanation of symbols]

[0148] 1: injection device, 2: housing, 20: barrel housing, 200: barrel other housing, 201: barrel one housing, 20A: barrel protrusion, 20B: biasing base, 20C: through portion, 20D: barrel step, 21: partition, 22: plunger housing, 220: plunger one housing, 221: plunger other housing, 22A: plunger housing protrusion, 22B: plunger housing recess, 23: trigger, 230: trigger mounting, 231: trigger mounting base, 232: trigger Guard barrel portion, 233: lock step portion, 234: convex portion, 23A: trigger body portion, 23B: top plate portion, 23C: outer skirt portion, 23D: release groove, 23E: interlocking groove, 23F: inner skirt portion, 23G: flat plate portion, 23a: trigger lock operation portion, 23b: barrel portion, 23c: protrusion portion, 23d: rotation groove, 3: plunger biasing portion, 4: barrel biasing portion, 5: syringe, 50: barrel, 500: barrel body portion, 501: barrel barrel portion, 502: outer flange portion, 503: injection needle, 50A: cover portion

Claims

1. a syringe including a barrel having an injection needle at its tip, and a plunger inserted into the barrel so as to be movable back and forth between the base end side of the barrel and the injection needle side; a housing formed in a cylindrical shape for accommodating the syringe, the housing having a barrel accommodating section formed on one side in a central axial direction for accommodating the barrel so as to be movable between a state in which the injection needle is accommodated and a state in which the injection needle protrudes from one side of the housing at a predetermined distance from the accommodated state, and a plunger accommodating section formed on the other side of the barrel accommodating section for accommodating the plunger; a barrel biasing portion provided in the barrel accommodating portion and biasing the barrel from one side of the housing to the other side; an engagement member disposed in the plunger accommodating portion and engaging with the plunger; a plunger biasing portion that engages with the engaging member and biases the plunger from the starting point toward the end point; a disengagement mechanism for disengaging the plunger from the engaging member by rotating the plunger and the engaging member relatively around a central axis in a state in which the barrel is accommodated in the barrel accommodating section with the injection needle protruding from one side of the housing and the plunger is positioned at the end point by the biasing force of the plunger biasing section, An injection device characterized by comprising a rotation suppression mechanism that suppresses the rotational speed of the relative rotation between the plunger and the engagement member in the engagement release mechanism.

2. the disengagement mechanism is configured to disengage the plunger and the engagement member by rotating the engagement member about a central axis relative to the plunger, The injection device of claim 1 , wherein the rotation suppression mechanism suppresses the rotational speed of the engagement member.

3. the engaging member includes an engaging rotation portion that engages with the plunger and rotates about a central axis relative to the plunger to release the engagement with the plunger, the disengagement mechanism is configured to disengage the plunger from the engagement member by rotating the engagement rotation portion relative to the plunger to disengage the plunger from the engagement rotation portion, The injection device of claim 2, wherein the rotation suppression mechanism includes an engaging non-rotating portion that does not rotate around a central axis relative to the engaging rotating portion, and a rotation suppression portion that is disposed between the engaging rotating portion and the engaging non-rotating portion and suppresses the rotation speed of the engaging rotating portion relative to the engaging non-rotating portion, and suppresses the rotation speed of the engaging rotating portion relative to the engaging non-rotating portion.

4. The injection device according to claim 3 , wherein the rotation suppressing portion is an elastic body that is arranged in an elastically deformed state between the engaging rotating portion and the engaging non-rotating portion.

5. the disengagement mechanism is configured to disengage the plunger from the engagement member by rotating the plunger about a central axis relative to the engagement member, The injection device of claim 1 , wherein the rotation suppression mechanism suppresses a rotational speed of the plunger.

6. the plunger includes a plunger rotation portion that engages with the engaging member and rotates about a central axis relative to the engaging member to release the engagement, a plunger non-rotation portion that does not rotate about the central axis relative to the plunger rotation portion, and a rotation suppression portion that is disposed between the plunger rotation portion and the plunger non-rotation portion and that suppresses a rotation speed of the plunger rotation portion relative to the plunger non-rotation portion, the disengagement mechanism is configured to disengage the plunger from the engaging member by rotating the plunger rotation portion relative to the engaging member to disengage the engaging member from the plunger rotation portion, The injection device according to claim 5 , wherein the rotation suppressing mechanism includes the plunger non-rotating portion and the rotation suppressing portion, and suppresses a rotational speed of the plunger rotating portion relative to the plunger non-rotating portion.

7. The injection device according to claim 6 , wherein the rotation suppressing portion is an elastic body that is arranged in an elastically deformed state between the plunger rotation portion and the plunger non-rotation portion.

Images