clamping device

Abstract

A clamping device (10) comprising: a plunger (20) having a plunger hole (21) open on a rear side; a housing (30) having a plunger receiving hole (31) open on a front side for receiving the plunger (20); a main biasing device (40) accommodated in an oil pressure chamber (11) formed between the plunger receiving hole (31) and a rear end of the plunger (20) so as to be capable of expanding and contracting and pressing the plunger (20) toward the front side; an oil supply passage (35) that supplies oil from outside the housing (30) to the oil pressure chamber (11); and a check valve (50) which allows oil to flow from the oil supply passage (35) into the oil pressure chamber (11) and prevents the oil from flowing out of the oil pressure chamber (11) to the oil supply passage (35), wherein the housing (30) has a valve receiving hole (32), an insertion hole (33) continuously formed on the rear side of the valve receiving hole (32), and a communication hole (34) continuously formed on the rear side of the insertion hole (33) and communicating with the oil supply passage (35), the check valve (50) is arranged in the valve receiving hole (32), the clamping device (10) has a flow rate control mechanism (60) which is inserted at a position between the check valve (50) and the oil supply passage (35), the clamping device (10) has a control chamber (61) formed at a position between the check valve (50) and the oil supply passage (35), the flow rate control mechanism (60) comprises a flow rate control element (62), at least a part of which is inserted into the insertion hole (33) forming the control space (61) so as to be able to move along a back-and-forth direction, a biasing unit (63) that presses the flow rate control element (62) toward the rear side, a first restricting part (64) that restricts movement of the flow rate control element (62) toward the front side, and a second restricting part (65) that restricts movement of the flow rate control element (62) toward the oil supply passage (35), when the flow control element (62) comes into contact with the first restriction part (64), a first control flow passage (66) is formed between the flow control element (62) and the first restriction part (64) through first connecting grooves (62a') of the flow control element (62), so that it is possible for the oil to flow between the control space (61) and the oil pressure chamber (11), when the flow rate control element (62) comes into contact with the second restriction part (65), a second control flow passage (67) is formed between the flow rate control element (62) and the second restriction part (65), so that it is possible for the oil to flow between the oil supply passage (35) and the control space (61), and the first control flow passage (66) has a greater flow resistance than the second control flow passage (67).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to a tensioning device that applies an appropriate tension to a running chain, a running belt or the like. 2. Description of the state of the art

[0002] It is common practice to use a tensioner to maintain proper tension of a chain or the like. For example, in a known chain guide mechanism for slidably guiding a drive chain, such as an endless roller chain, which passes over respective sprockets of a crankshaft and a camshaft in an engine compartment, a tensioner is used to preload a tensioner lever to maintain proper tension of the chain or the like.

[0003] A known tensioner used in such a chain guide mechanism includes: a plunger having a plunger hole open on a rear side; a housing having a plunger receiving hole open on a front side for receiving the plunger; a biasing device accommodated in an oil pressure chamber formed between the plunger receiving hole and a rear end of the plunger so as to be capable of expanding and contracting and urging the plunger toward the front side; an oil supply passage for supplying oil from outside the housing into the oil pressure chamber; and a check valve that allows oil to flow from the oil supply passage into the oil pressure chamber and prevents oil from flowing out of the oil pressure chamber to the oil supply passage (see, for example, Japanese Patent Application Laid-Open No. 2001-12569).

[0004] US 2015 / 0 024 887 A1 shows further relevant prior art for the present invention. SUMMARY OF THE INVENTION

[0005] However, with this tensioner, when the engine is running at high speed, the amount of oil supplied from a hydraulic power source such as an oil pump increases, and sometimes the supplied oil is excessively supplied into the oil pressure chamber via the check valve. The oil pressure in the oil pressure chamber then becomes too high, causing the plunger to protrude toward the tensioner lever more than necessary. If the drive chain or the like is pressed too hard, problems such as noise or a shortened drive chain life will occur.

[0006] As a solution to the above problem, it is conceivable to provide a relief valve mechanism that releases oil from the oil pressure chamber to the outside of the plunger when the oil pressure in the oil pressure chamber increases (see, for example, Japanese Patent Application Laid-Open No. JP 2001-12569 A).

[0007] With the relief valve mechanism of Japanese Patent Application Laid-Open No. 2001-12569 A, when the oil pressure in the oil pressure chamber increases, a portion of the oil supplied from the hydraulic power source, such as an oil well, is released to the outside. This increases oil consumption and requires more power from the hydraulic power source.

[0008] As another solution to the above-described problem, it is known to form an excess oil drain passage in the housing, which communicates with the oil supply passage, to release excess oil to the outside of the tensioner. When too much oil is supplied from the hydraulic power source, a portion of the oil is released from the excess oil drain passage to prevent excessive oil supply to the oil pressure chamber (see, for example, Japanese Patent Application Laid-Open No. 2003-206999 A).

[0009] The tensioner of Japanese Patent Application Laid-Open No. 2003-206999 requires the formation of a drain passage for excess oil in the housing. This not only increases production costs but also, in substantially the same way as the invention of Japanese Patent Application Laid-Open No. 2001-12569, increases oil consumption and requires more power from the hydraulic power source, since part of the oil supplied from the hydraulic power source is released from the drain passage to the outside of the tensioner.

[0010] The present invention solves these problems, and the object of the invention is to provide a clamping device with which the oil pressure in the oil pressure chamber can be kept stable with a simple structure.

[0011] The present invention is defined in claim 1.

[0012] The present invention solves the problems described above by providing a clamping device comprising: a plunger having a plunger hole open on a rear side; a housing having a plunger receiving hole open on a front side for receiving the plunger; a main urging device accommodated in an oil pressure chamber formed between the plunger receiving hole and a rear end of the plunger so as to be capable of expanding and contracting and urging the plunger toward the front side; an oil supply passage that supplies oil from outside the housing to the oil pressure chamber; a check valve that allows oil to flow from the oil supply passage into the oil pressure chamber and prevents oil from flowing out of the oil pressure chamber to the oil supply passage; and a flow amount control mechanism.which is inserted at a position further toward the oil supply passage than the check valve. The flow control mechanism includes a flow control element inserted into a control chamber formed at the position further toward the oil supply passage than the check valve so that it is capable of approaching and separating from the oil pressure chamber, a control biasing unit that urges the flow control element toward the oil supply passage, a first restricting part that restricts movement of the flow control element toward the oil pressure chamber, and a second restricting part that restricts movement of the flow control element toward the oil supply passage. When the flow control element comes into contact with the first restricting part,The first control flow passage is formed between the flow control element and an inner wall of the control chamber, allowing oil to flow between the control chamber and the oil pressure chamber. When the flow control element comes into contact with the second restriction part, a second control flow passage is formed between the flow control element and an inner wall of the control chamber, allowing oil to flow between the oil supply passage and the control chamber. The flow control element and the inner wall of the control chamber are arranged such that the first control flow passage has a greater flow resistance than the second control flow passage.

[0013] According to one aspect of the present invention, the flow rate control mechanism, which is inserted at a position further toward the oil supply passage than the check valve, includes a flow rate control member inserted into a control space formed at the position further toward the oil supply passage than the check valve so as to be capable of approaching and separating from the oil pressure chamber, a control biasing unit that urges the flow rate control member toward the oil supply passage, a first restricting part that restricts movement of the flow rate control member toward the oil pressure chamber, and a second restricting part that restricts movement of the flow rate control member toward the oil supply passage.When the flow control element comes into contact with the first restriction part, the first control flow passage is formed between the flow control element and an inner wall of the control chamber, allowing oil to flow between the control chamber and the oil pressure chamber. When the flow control element comes into contact with the second restriction part, a second control flow passage is formed between the flow control element and an inner wall of the control chamber, allowing oil to flow between the oil supply passage and the control chamber. The flow control element and the inner wall of the control chamber are arranged such that the first control flow passage has a greater flow resistance than the second control flow passage.

[0014] In this way, although a sufficient amount of oil is supplied to the oil pressure chamber through the second oil flow passage, which has a relatively smaller flow resistance during normal operation, when the amount of supplied oil is increased due to the engine rotation at high speed or the like, the flow rate control element is moved toward the oil pressure chamber by the oil pressure, so that the amount of oil supplied to the oil pressure chamber can be controlled through the first control flow passage, which has a relatively large flow resistance. Thus, the oil pressure in the oil pressure chamber can be stabilized with a simple structure.

[0015] Furthermore, since the release of part of the oil to the outside, as is done in known clamping devices, can be avoided, the oil consumption can be reduced, thereby enabling a reduction in the size of the hydraulic power source.

[0016] According to another aspect of the present invention, the check valve is used as part of the inner wall of the control chamber, thus simplifying the structure. Furthermore, since the check valve is easier to machine than the housing, the inner wall of the control chamber can be precisely formed without increasing production costs, thus achieving favorable control of the amount of oil supplied to the oil pressure chamber.

[0017] According to another aspect of the present invention, the flow control element has a restricted surface abutting a restriction wall surface, which serves as a first restriction portion when the first restriction portion restricts movement of the flow control element toward the oil pressure chamber. A first communication groove is formed on the restricted surface. Therefore, when the movement of the flow control element toward the oil pressure chamber is restricted, its restricted surface contacts the first restriction portion to advantageously control the position of the flow control element while allowing oil to flow through the first communication groove between the control chamber and the oil pressure chamber.

[0018] According to another aspect of the present invention, the flow control member has a small-diameter portion formed on the restricted surface. Consequently, when the first restricting portion restricts the movement of the flow control member toward the oil pressure chamber, the small-diameter portion of the flow control member is inserted into the oil hole of the first restricting portion, and the flow control member is held in a stable position. Furthermore, the gap between the small-diameter portion of the flow control member and the communication hole of the first restricting portion can be used as a first control flow passage.

[0019] According to another aspect of the present invention, the flow rate control member includes a base portion having the restricted area, and a large-diameter portion formed on the side of the base portion facing the oil supply passage and having a larger diameter than the base portion. One end of the control spring is inserted into a side surface of the large-diameter portion on the side facing the oil pressure chamber. Thus, the flow rate control member and the control spring are stably inserted into the control chamber. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory schematic diagram of a timing control system incorporating a tensioning device according to a first embodiment of the present invention; Fig. 2 shows a cross-sectional view showing the clamping device; Fig. 3 is a perspective cross-sectional view showing a flow rate control mechanism; Fig. 4A is a perspective cross-sectional view showing a flow rate control element; Fig. 4B is a perspective cross-sectional view showing the flow rate control element; Fig. 5 is a cross-sectional view showing a state of the flow rate control mechanism during normal operation; Fig. 6 is a cross-sectional view showing a state of the flow rate control mechanism when the oil pressure increases; Fig. 7A is a perspective view showing a flow rate control element of a tensioner according to a second embodiment of the present invention; and Fig. 7B is a perspective view showing the flow rate control member of the tensioner according to the second embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A clamping device 10 according to a first embodiment of the present invention will be described with reference to the drawings.

[0021] First, the tensioner 10 is incorporated into a chain transmission system used in a timing system or the like of a vehicle engine. As shown in Fig. 1, the tensioner for applying an appropriate tension via a tensioner lever G to the slack side of a drive chain CH passing over a plurality of sprockets S1 to S3 is mounted on an engine block (not shown) to reduce vibration during driving.

[0022] The clamping device 10 comprises, as in Fig. 2, a plunger 20 having a plunger hole 21 open on a rear side, a housing 30 having a plunger receiving hole 31 open on a front side for receiving the plunger 20, a main spring (main biasing unit) 40 accommodated in an oil pressure chamber 11 formed between the plunger 20 and the plunger receiving hole 31 so as to be capable of expanding and contracting and urging the plunger 20 toward the front side, a check valve 50, and a flow amount control mechanism 60 disposed at a position further toward the oil supply passage 35 than the check valve 50.

[0023] Various components of the clamping device 10 are described below with reference to the drawings.

[0024] First, the plunger 20 is made of metal such as iron and is inserted into the plunger receiving hole 31 so that it is able to move back and forth in the front-back direction as shown in Fig. 2 is shown.

[0025] The housing 30 is made of metal and the like and comprises, as shown in Fig. 2, the cylindrical plunger receiving hole 31 open on the front side, a cylindrical valve receiving hole 32 continuously formed on the rear side of the plunger receiving hole 31 and having a smaller diameter than the plunger receiving hole 31, a cylindrical insertion hole 33 continuously formed on the rear side of the valve receiving hole 32 and having a smaller diameter than the valve receiving hole 32, a cylindrical communication hole 34 continuously formed on the rear side of the insertion hole 33 and having a smaller diameter than the insertion hole 33, an oil supply passage 35 extending from the outside of the housing 30 to the communication hole 34 in the form of a hole for supplying oil from the outside of the housing 30 into the oil pressure chamber 11, and a mounting part 36 used for fixing the housing 30 to the engine block.

[0026] The main spring 40 has one end abutting against the bottom of the plunger hole 21 (front side portion of the plunger 20), and the other end being arranged with the check valve 50 (ball seat 52 and holding part 53), as shown in Fig. 2 is shown.

[0027] The check valve 50 allows the oil to flow into the oil pressure chamber 11 and prevents the oil from flowing out of the oil pressure chamber 11. As shown in Fig. 2, the check valve is arranged in the valve receiving hole 32.

[0028] As in Fig. As shown in Fig. 2, the check valve 50 is formed of a spherical check ball 51, a ball seat 52 having a check ball support portion 52a open on the side facing the oil pressure chamber 11 (front side in this embodiment), a retaining portion 53 that restricts the movement of the check ball 51, and a ball spring 54 disposed between the check ball 51 and the retaining portion 53. These components of the check valve 50 are made of metal, synthetic resin, or the like.

[0029] The ball seat 52 is press-fitted into the valve receiving hole 32 of the housing 30 and is thus fixed to the housing 30, as shown in Fig. 2. The ball seat 52 may be secured to the housing 30 by means other than a press fit. The ball seat 52 includes the check ball support portion 52a, a retainer receiving recess 52b continuously formed on the front side of the check ball support portion 52a, and an oil hole 52c extending from the check ball support portion 52a to the rear side of the ball seat 52.

[0030] The holding part receiving recess 52b has a larger diameter than the check ball support hole 52a, as shown in Fig. 2, while the oil hole 52c has a smaller diameter than the check ball support portion 52a. The step between the check ball support portion 52a and the oil hole 52c (bottom of the check ball support portion 52a) serves as a ball seat portion 52d for the check ball 51 to be seated thereon in annular close contact.

[0031] The holding part 53 is press-fitted into the holding part receiving recess 52b, as shown in Fig. 2. The holding part 53 has a plurality of oil holes 53a extending in the front-back direction and a spring support part 53b projecting from the rear surface of an upper plate of the holding part 53 toward the rear side.

[0032] The ball spring 54 is arranged to fit around the spring support part 53b as shown in Fig. 2, and pushes the check ball 51 toward the ball seat part 52d. This ball spring 54 is not an essential component and can be omitted depending on the design.

[0033] The flow rate control mechanism 60 comprises, as shown in Fig. 2 and Fig. 3, a flow rate control member 62 inserted into a control space 61 formed at a position further toward the oil supply passage 35 than the check valve 50 so as to be capable of approaching and separating from the oil pressure chamber 11 (to be movable in the front-back direction), a control spring (control biasing unit) 63 that urges the flow rate control member 62 toward the oil supply passage 35, a first restricting part 64 that restricts movement of the flow rate control member 62 toward the oil pressure chamber 11, and a second restricting part 65 that restricts movement of the flow rate control member 62 toward the oil supply passage 35.

[0034] The control chamber 61 is formed on the side of the check valve 50 facing the oil supply passage 35, as shown in Fig. 2 and Fig. 3, so that the flow rate control element 62 and the control spring 63 are inserted therein. In this embodiment, the inner wall of the control chamber 61 is formed by the inner peripheral wall and the rear end wall of the insertion hole 33 (stepped portion between the insertion hole 33 and the communication hole 34) in the housing 30 and a rear portion of the check valve 50 (ball seat 52).

[0035] In this embodiment, the first restricting part 64, which restricts movement of the flow rate control member 62 toward the oil pressure chamber 11, is formed by a rear portion of the check valve 50 (ball seat 52), and the second restricting part 65, which restricts movement of the flow rate control member 62 toward the oil supply passage 35, is formed by the rear end wall of the insertion hole 33 of the housing 30.

[0036] As in Fig. 3 and Fig. 4A and Fig. 4B, the flow rate control member 62 is formed of a substantially columnar base part 62a, a small-diameter part 62b formed on a side of the base part 62a facing the oil pressure chamber 11 and having a smaller diameter than the base part 62a, and a large-diameter part 62c formed on a side of the base part 62a facing the oil supply passage 35 and having a larger diameter than the base part 62a. The base part 62a, the small-diameter part 62b, and the large-diameter part 62c are coaxial with each other.

[0037] A side surface of the base part 62a on the side facing the oil pressure chamber 11 serves as a restricted surface abutting against the first restricting part 64, as shown in Fig. 6 when the first restricting part 64 restricts the movement toward the oil pressure chamber 11.

[0038] A plurality of radially extending first communication grooves 62a' are formed in the side surface of the base part 62a on the side (restricted surface) facing the oil pressure chamber 11, as shown in Fig. 3 and Fig. 4A and Fig. 4B is shown.

[0039] The small diameter part 62b has a conical shape as shown in Fig. 3 and Fig. 4A and Fig. 4B, and protrudes from the side surface of the base part 62a on the side (restricted surface) facing the oil pressure chamber 11.

[0040] This small diameter part 62b enters the oil hole 52c when the first restricting part 64 restricts the movement toward the oil pressure chamber 11, as shown in Fig. 6 is shown.

[0041] The large diameter part 62c is formed by a plurality of legs projecting from an outer peripheral surface of the base part 62a on the side facing the oil supply passage 35, as shown in Fig. 3 and Fig. 4A and Fig. 4B. The plurality of legs are arranged circumferentially spaced from each other. The large-diameter portion 62c is designed to have an outer diameter slightly smaller than the inner diameter of the inner peripheral wall of the insertion hole 33 forming the control chamber 61.

[0042] The control spring 63 has one end fitted to the rear surface of the check valve 50 (ball seat 52) ​​and the other end fitted to the side surface of the large diameter part 62c on the side facing the oil pressure chamber 11, as shown in Fig. 2 and Fig. 3 is shown.

[0043] During normal operation of the clamping device 10 according to this embodiment configured as described above, the flow rate control member 62 is first pressed backward by the urging force of the control spring 63 such that the large diameter part 62c of the flow rate control member 62 abuts against the second restriction part 65, as shown in Fig. 5 is shown.

[0044] In this state, a second control flow passage 67 is formed between the flow rate control member 62 and the inner wall of the control chamber 61 to allow the oil to flow between the oil supply passage 35 and the control chamber 61. Specifically, the oil flows from the oil supply passage 35 into the control chamber 61 through the gaps between the plurality of legs constituting the large-diameter part 62c, and the oil that has entered the control chamber 61 is supplied to the oil pressure chamber 11 through the check valve 50.

[0045] When the amount of oil supplied from the oil supply passage 35 increases (when the oil pressure increases), the flow amount control member 62 moves forward such that the side surface of the base part 62a on the side facing the oil pressure chamber 11 (restricted surface) abuts against the first restriction part 64, as shown in Fig. 6 is shown.

[0046] In this state, a first control flow passage 66 is formed between the flow rate control member 62 and the inner wall of the control chamber 61 to allow the oil to flow between the control chamber 61 and the oil pressure chamber 11. Specifically, the oil is supplied from the control chamber 61 toward the oil pressure chamber 11 through the first communication grooves 62a' formed on the side surface of the base part 62a on the side facing the oil pressure chamber 11 and through the gap between the oil hole 52c and the small-diameter part 62b.

[0047] Since the flow resistance of the first control flow passage 66 is set larger than the flow resistance of the second control flow passage 67, the amount of oil supplied to the oil pressure chamber 11 is kept small as the amount of oil supplied from the oil supply passage 35 increases. Consequently, excessive supply of oil to the oil pressure chamber 11 can be avoided while maintaining the amount of oil supplied to the oil pressure chamber 11 during normal operation.

[0048] Next, a clamping device 10 according to a second embodiment of the present invention will be described mainly with reference to Fig. 7A and Fig. 7B. The second embodiment is the same as the above-described first embodiment except for some parts of the flow rate control member 62, and therefore, the configurations except for the differences will not be described.

[0049] The large diameter part 62c of the flow rate control member 62 according to the first embodiment is formed by a plurality of legs as shown in Fig. 4A and Fig. 4B. In the second embodiment, the large diameter part 62c of the flow rate control member 62 is formed as a columnar portion as shown in Fig. 7A and Fig. 7B is shown.

[0050] The flow rate control member 62 according to the second embodiment has second communication grooves 62c' continuously formed on the side surface of the large diameter part 62c on the side facing the oil supply passage 35 and on the outer peripheral surface of the large diameter part 62c, as shown in Fig. 7A and Fig. 7B is shown.

[0051] The second communication grooves 62c' formed on the side surface of the large-diameter part 62c on the side facing the oil supply passage 35 extend in the radial direction, while the second communication grooves 62c' formed on the peripheral surface of the large-diameter part 62c extend in the front-back direction.

[0052] Therefore, when the flow rate control member 62 is pressed rearward by the urging force of the control spring 63 and the large diameter part 62c of the flow rate control member 62 abuts against the second restricting part 65, the oil can flow between the oil supply passage 35 and the control chamber 61 through the second communication grooves 62c'.

[0053] The flow rate control member 62 according to the first embodiment has the first communication grooves 62a' only on the side surface of the base part 62a on the side facing the oil pressure chamber 11, as shown in Fig. 4A and 4B. In the flow rate control element 62 according to the second embodiment shown in Fig. 7A and Fig. 7B, the first connecting grooves 62a' are also formed on the outer peripheral surface of the base part 62a to extend in the front-back direction.

[0054] That is, in the flow amount control member 62 according to the second embodiment, the first communication grooves 62a' formed on the side surface of the base part 62a on the side facing the oil pressure chamber 11 and the first communication grooves 62a' formed on the outer peripheral surface of the base part 62a' are provided continuously with each other.

[0055] Therefore, the first communication grooves 62a' formed on the outer peripheral surface of the base part 62a also serve as guides for guiding oil to the first communication grooves 62a' formed on the side surface of the base part 62a on the side facing the oil pressure chamber 11.

[0056] Although embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, and it can be embodied with various design changes without departing from the scope of the present invention as set forth in the claims.

[0057] For example, although the tensioner 10 has been described in the above embodiments as a component incorporated into a timing system of a vehicle engine, the intended use of the tensioner 10 is not limited to this specific application.

[0058] Furthermore, although the tensioner 10 in the above embodiments has been described as a component that applies tension to a drive chain CH by means of a tensioner lever G, the plunger 20 may directly slide the drive chain CH with a distal end thereof to apply tension to the drive chain CH.

[0059] The application of the tensioning device does not necessarily have to be limited to a transmission mechanism with a drive chain CH, but it can also be applied to substantially similar transmission mechanisms using belts, ropes and the like, and can be used in a variety of industrial fields where it is necessary to apply tension to an elongated component.

[0060] Although in the above-described embodiments, the housing 30 accommodating the plunger 20 has been described as the component known as a clamp body attached to an engine block or the like, the housing 30 is not limited to the specific shape described above, but may be a cylindrical component known as a sleeve inserted into a body hole formed in the clamp body.

[0061] Although in the above-described embodiments, the first communication grooves 62a' formed on the side surface of the base part 62a on the side facing the oil pressure chamber 11 (restricted surface) and the like are used as parts for configuring the first control flow passage 66, the first control flow passage 66 may be formed in any manner as long as it allows the oil to flow between the control space 61 and the oil pressure chamber 11 when the flow rate control member 62 comes into contact with the first restriction part 64. For example, grooves may be formed on the inner wall of the control space 61 and used as parts for configuring the first control flow passage 66.

[0062] In substantially the same manner, the second control flow passage 67 may be formed in any manner as long as it allows the oil to flow between the oil supply passage 35 and the control space 61 when the flow amount control member 62 comes into contact with the second restriction part 65.

[0063] Although in the above-described embodiments, the inner wall of the control chamber 61 is formed from the inner peripheral wall and the rear end wall of the insertion hole 33 in the housing 30 and a rear portion of the check valve 50 (ball seat 52), the control chamber 61 may be formed in any manner.

[0064] Although in the above-described embodiments, the control space 61 is formed adjacent to the check valve 50 on the rear side, the control space 61 may be provided at any other location as long as it is located at a position farther toward the oil supply passage 35 than the check valve 50 (that is, closer to the oil supply passage opening opening into the outer surface of the housing 30). For example, when an oil reservoir chamber (not shown) that retains oil to be supplied to the oil pressure chamber 11 is provided in the tensioner, the control space may be formed on a side facing the oil supply passage 35 of the check valve 50 disposed between the oil pressure chamber 11 and the oil reservoir chamber.

Claims

[1] A clamping device (10) comprising: a plunger (20) having a plunger hole (21) open on a rear side; a housing (30) having a plunger receiving hole (31) open on a front side for receiving the plunger (20); a main urging device (40) accommodated in an oil pressure chamber (11) formed between the plunger receiving hole (31) and a rear end of the plunger (20) so as to be capable of expanding and contracting and pressing the plunger (20) toward the front side; an oil supply passage (35) that supplies oil from outside the housing (30) to the oil pressure chamber (11); and a check valve (50) which allows oil to flow from the oil supply passage (35) into the oil pressure chamber (11) and prevents the oil from flowing out of the oil pressure chamber (11) to the oil supply passage (35), wherein the housing (30) has a valve receiving hole (32), an insertion hole (33) continuously formed on the rear side of the valve receiving hole (32), and a communication hole (34) continuously formed on the rear side of the insertion hole (33) and communicating with the oil supply passage (35), the check valve (50) is arranged in the valve receiving hole (32), the clamping device (10) has a flow rate control mechanism (60) which is inserted at a position between the check valve (50) and the oil supply passage (35), the clamping device (10) has a control chamber (61) formed at a position between the check valve (50) and the oil supply passage (35), the flow rate control mechanism (60) comprises a flow rate control element (62), at least a part of which is inserted into the insertion hole (33) forming the control space (61) so as to be able to move along a back-and-forth direction, a biasing unit (63) that presses the flow rate control element (62) toward the rear side, a first restricting part (64) that restricts movement of the flow rate control element (62) toward the front side, and a second restricting part (65) that restricts movement of the flow rate control element (62) toward the oil supply passage (35), when the flow control element (62) comes into contact with the first restriction part (64), a first control flow passage (66) is formed between the flow control element (62) and the first restriction part (64) through first connecting grooves (62a') of the flow control element (62), so that it is possible for the oil to flow between the control space (61) and the oil pressure chamber (11), when the flow rate control element (62) comes into contact with the second restriction part (65), a second control flow passage (67) is formed between the flow rate control element (62) and the second restriction part (65), so that it is possible for the oil to flow between the oil supply passage (35) and the control space (61), and the first control flow passage (66) has a greater flow resistance than the second control flow passage (67). [2] Clamping device (10) according to claim 1, wherein a part of the inner wall of the control chamber (61) is formed by the check valve (50). [3] Clamping device (10) according to claim 1 or 2, in which the first restriction part (64) has an oil hole (52c) communicating with the oil pressure chamber (11), and the flow rate control member (62) has a small diameter part (62b) to be inserted into the oil hole (52c) when the flow rate control member (62) is restricted from moving toward the front side by the first restricting part (64). [4] Clamping device (10) according to one of claims 1 to 3, wherein the flow rate control element (62) comprises a base part (62a) and a large diameter part (62c) formed on the rear side of the base part (62a) and having a larger diameter than the base part (62a), the pretensioning unit is designed as a control spring (63), and one end of the control spring (63) is set on a side surface of the large diameter part (62c) on a side facing the oil pressure chamber (11), and the other end of the control spring (63) is set on the first restriction part (64).

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