tensioning device

Abstract

The present invention provides a tensioning device that can prevent the ratchet pawl from wobbling relative to the rack with a simple structure and can ensure a large backlash. Specifically, the tensioning device (10) includes a ratchet (60) which is rotatably mounted on a housing (20) and has a front pawl (61) and a rear pawl (62) formed apart in the front-rear direction on a side opposite to the rack (32). The ratchet (60) also has an additional pawl (63) formed in the front-rear direction between the front pawl (61) and the rear pawl (62) on a side opposite to the rack (32).

Description

Technical Field

[0001] This invention relates to a tensioning device for imparting appropriate tension to a drive belt or drive chain in a timing system of an engine, etc. Background Technology

[0002] Traditionally, tensioning devices are typically used to maintain the appropriate tension of chains, etc. For example, there is a known tensioning device that applies force to the tensioning rod in a chain guide mechanism that slides a roller chain or other drive chain through a tensioning rod to maintain the appropriate tension of the chain, etc. The roller chain or other drive chain is seamlessly wound between sprockets on the crankshaft and camshaft respectively located in the engine compartment.

[0003] As such a tensioning device, a ratchet-type tensioning device is known, comprising: a housing having a housing hole formed by opening to the front side; a plunger configured to move in the front-rear direction within the housing hole and having a rack portion on its outer peripheral surface, the rack portion having a plurality of rack teeth arranged side by side in the front-rear direction; a main force-applying unit that applies force to the plunger toward the front side; and a ratchet supported on the housing by a rotatable shaft and configured such that the ratchet engages with the rack portion to prevent the plunger from moving to the rear side (see, for example, Patent Documents 1-3).

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-214957

[0006] Patent Document 2: Japanese Patent Application Publication No. 2007-147018

[0007] Patent Document 3: Japanese Patent Application Publication No. 11-344086 Summary of the Invention

[0008] like Figure 6A As shown, in this existing tensioning device, on the side of the ratchet 160, which is arranged opposite to the rack portion 132 formed on the plunger 130, in addition to the front pawl 161 that engages with the rack portion 132 to prevent the plunger 130 from moving to the rear, a rear pawl 162 is also formed at a predetermined interval on the rear side of the front pawl 161, thereby ensuring the backlash.

[0009] Furthermore, this toothed tensioning device is configured such that, starting from the state where the front claw 161 engages with the rack portion 132 to prevent the plunger 130 from moving rearward, the tension of the drive chain weakens, and thus, when the plunger 130 moves forward relative to the housing, it starts from the state where only the front claw 161 is in contact with the rack portion 132, as... Figure 6AAs shown, the process transitions from a state where the forward claw 161 and the rear claw 162 are in contact (tangentially) with the rack portion 132, and then from... Figure 6A From the state shown, the process transitions to a state where only the rear claw 162 contacts the rack portion 132. Subsequently, as the plunger 130 advances further, and the rack teeth 133 that engage with the rear claw 162 pass forward past the rear claw 162, each claw 161, 162 engages with a new rack tooth 133 (the next rear rack tooth 133 that has engaged so far).

[0010] However, such a backlash tensioning device has the following problem: when the backlash is increased, as... Figure 6B As shown, since the front claw 161 and the rear claw 162 are in contact (tangentially) with each rack tooth 133 near the tooth tip side of each rack tooth 133, the result is that, starting from the state where only the front claw 161 is in contact with the rack portion 132, towards... Figure 6B When the front claw 161 and rear claw 162 are in contact with the rack portion 132, a so-called "free swing" may occur, which may cause damage to the engagement between the rear claw 162 and the rack portion 132.

[0011] Therefore, the present invention is an invention that solves these problems. The technical problem to be solved is to provide a tensioning device that can prevent the ratchet pawl from swinging relative to the rack with a simple structure and can ensure a large backlash.

[0012] The tensioning device according to the present invention comprises: a housing having a housing hole formed by opening to the front side; a plunger disposed within the housing hole and movable in the front-rear direction, and having a rack portion on its outer peripheral surface, the rack portion having a plurality of rack teeth arranged side by side in the front-rear direction; a main force-applying unit that applies force to the plunger toward the front side; and a ratchet rotatably mounted on the housing, and having a front pawl and a rear pawl formed apart in the front-rear direction on a side disposed opposite to the rack portion, and configured such that the front pawl engages with the rack portion to prevent rearward movement of the plunger. The problem can be solved by the following: the ratchet has an additional pawl formed in the front-rear direction between the front pawl and the rear pawl on a side disposed opposite to the rack portion.

[0013] According to one embodiment of the invention, since an additional pawl is formed between the front pawl and the rear pawl in the front-rear direction on the side of the ratchet arranged opposite to the rack portion of the plunger, the additional pawl can engage with the rack portion midway from the state where the front pawl engages with the rack portion and prevents the plunger from moving rearward, to the state where the plunger moves forward relative to the housing and then contacts the rack portion with the rear pawl. Thus, while preventing the ratchet pawl from wobbling relative to the rack portion, the distance between the front pawl and the rear pawl can be increased to ensure a larger backlash.

[0014] According to other embodiments of the present invention, it is possible to avoid the additional pawl getting too close to the rack side when the ratchet rotates, which would cause the additional pawl to lock at the bottom (valley) of the teeth between the rack teeth, and to achieve smooth engagement of each pawl of the ratchet relative to the rack. Attached Figure Description

[0015] Figure 1 This is an explanatory diagram showing a timing system incorporating a tensioning device according to an embodiment of the present invention.

[0016] Figure 2 This is a cross-sectional view showing the tensioning device.

[0017] Figure 3 This is an explanatory diagram centered on the ratchet mechanism.

[0018] Figure 4 This is an explanatory diagram showing a variation of the ratchet mechanism.

[0019] Figure 5A This is an explanatory diagram showing the operation of a ratchet mechanism.

[0020] Figure 5B This is an explanatory diagram showing the operation of a ratchet mechanism.

[0021] Figure 5C This is an explanatory diagram showing the operation of a ratchet mechanism.

[0022] Figure 6A This is a reference diagram used to illustrate problems in the prior art.

[0023] Figure 6B This is a reference diagram used to illustrate problems in the prior art.

[0024] Symbol Explanation

[0025] 10-Tensioning device; 11-Oil chamber; 20-Housing; 21-Housing hole; 22-Oil supply hole; 23-Ratchet receiving groove; 24-Mounting hole; 30-Plunger; 31-Plunger hole; 32-Rack section; 33-Rack tooth; 40-Main spring (main force-applying unit); 50-Check valve; 60-Ratchet; 61-Front pawl; 62-Rear pawl; 63-Additional pawl; 64-Rotation center of ratchet; 70-Ratchet spring; CH-Drive chain; G;-Tensioning rod; S1~S3-Sprocket; X-Forward and backward direction; Y;-Lateral direction; L1-First imaginary line; L2-Second imaginary line. Detailed Implementation

[0026] The tensioning device 10 according to one embodiment of the present invention will now be described with reference to the accompanying drawings.

[0027] First, the tensioning device 10 is a device installed in chain drive systems used in automobile engines, such as timing systems. Figure 1 As shown, it is mounted on the engine assembly (not shown) and, through the tensioning rod G, imparts appropriate tension to the slack side of the drive chain CH, which is wound on multiple sprockets S1 to S3, in order to suppress vibrations generated during movement.

[0028] like Figure 2 As shown, the tensioning device 10 includes: a housing 20 having a housing hole 21 opening to the front; a plunger 30 configured within the housing hole 21 to be movable (slidable) in the front-rear direction X and having a cylindrical plunger hole 31 opening to the rear; an oil pressure chamber 11 formed between the plunger 30 and the housing hole 21; a main spring 40, serving as the main force-applying unit, which is retractably housed within the oil pressure chamber 11 and applies force to the plunger 30 towards the front; a check valve 50 that allows oil to flow from the oil supply hole 22 formed on the housing 20 into the oil pressure chamber 11 while preventing oil from flowing out of the oil pressure chamber 11 into the oil supply hole 22; a ratchet 60 mounted on the housing 20 in a rotatable (rocking) state; and a ratchet spring 70, serving as a ratchet force-applying unit, which applies force to the ratchet 60.

[0029] The components of the tensioning device 10 will now be described based on the accompanying drawings.

[0030] First, the shell 20 is formed of metals such as aluminum alloy, and as... Figure 2 As shown, it has: a ratchet receiving groove 23 for configuring the ratchet 60; and mounting holes 24 for through screws, etc., for fixing the housing 20 to a mounting object such as an engine assembly (not shown).

[0031] The plunger 30 is made of metals such as iron, such as Figure 2 As shown, it is formed into a cylindrical shape with a front bottom and is inserted into the housing hole 21, and can move forward and backward in the front-back direction X.

[0032] like Figure 2 , Figure 3 As shown, a serrated rack portion 32 is engraved on the outer peripheral surface of the plunger 30. The rack portion 32 has multiple rack teeth 33 of the same shape (approximately triangular) arranged side by side with equal tooth pitch in the front-rear direction X.

[0033] The front-to-back dimension X of the rack section 32 is set according to the expected slack of the transmission chain CH.

[0034] The main spring 40 is formed as a helical spring, and as... Figure 2 The device is configured such that one end is located behind the front bottom of the plunger 30, and the other end is located at the check valve 50.

[0035] Therefore, as Figure 2 As shown, while the main spring 40 applies force to the plunger 30 towards the front, it presses the check valve 50 against the rear bottom of the housing hole 21 of the housing 20.

[0036] The ratchet 60 is made of metal such as iron, and as... Figure 2 As shown, it is mounted on the housing 20 in a rotatable (shaking) state. In this embodiment, it is fixed to a ratchet pin (not shown), which is supported on the housing 20 in a rotatable state.

[0037] like Figure 2 As shown, on the side opposite to the rack portion 32 of the plunger 30, the ratchet 60 has: a front pawl 61 and a rear pawl 62, which are separated in the front-rear direction X; and an additional pawl 63, which is formed between the front pawl 61 and the rear pawl 62 in the front-rear direction X.

[0038] The front claw 61, the rear claw 62, and the additional claw 63 are formed into a roughly triangular shape corresponding to the tooth shape of the rack tooth 33.

[0039] Next, the following is divided into Figure 3 The examples shown and Figure 4 The detailed structure of each part of the ratchet 60 will be explained using the example shown.

[0040] Additionally, in the following explanation, such as Figure 3 , 4 As shown, the imaginary line passing through the rotation center 64 of the ratchet 60 and extending along the front-rear direction X is defined as the first imaginary line L1, and the imaginary line passing through the rotation center 64 of the ratchet 60 and extending along the transverse direction Y orthogonal to the front-rear direction X is defined as the second imaginary line L2.

[0041] Furthermore, in the following explanation, such as Figure 3 , 4As shown, with the front pawl 61 engaged with the rack portion 32 to prevent the plunger 30 from moving rearward, the distance in the transverse Y direction from the rotation center 64 of the ratchet 60 to the top of the front pawl 61 is defined as A, the distance in the transverse Y direction from the rotation center 64 of the ratchet 60 to the top of the additional pawl 63 is defined as B, and the distance in the radial direction centered on the rotation center 64 of the ratchet 60 from the rotation center 64 of the ratchet 60 to the top of the rear pawl 62 is defined as C.

[0042] First of all, Figure 3 In the example shown, the ratchet 60 is configured such that, in the state where the front pawl 61 engages with the rack portion 32 and prevents the plunger 30 from moving to the rearward side, the tip of the additional pawl 63 is located further forward in the front-rear direction X than the rotation center 64 of the ratchet 60 (in other words, further forward than the second imaginary line L2).

[0043] In addition, Figure 3 In the example shown, the ratchet 60 is configured such that, when the front pawl 61 engages with the rack portion 32 and prevents the plunger 30 from moving to the rearward side, the tip of the front pawl 61 is located further forward than the rotation center 64 of the ratchet 60 in the front-rear direction X (in other words, further forward than the second imaginary line L2), while the tip of the rear pawl 62 is located further rearward than the rotation center 64 of the ratchet 60 in the front-rear direction X (in other words, further rearward than the second imaginary line L2).

[0044] Moreover, in the above-described structure Figure 3 In the example shown, the distances A to C are configured such that A ≧ B > C.

[0045] In addition, Figure 4 In the example shown, the ratchet 60 is configured such that, when the front pawl 61 engages with the rack portion 32 to prevent the plunger 30 from moving to the rearward side, the tip of the additional pawl 63 is located in the front-rear direction X at a position further rearward than the rotation center 64 of the ratchet 60 (in other words, further rearward than the second imaginary line L2), or at the same position as the rotation center 64 of the ratchet 60 (in other words, at the same position as the second imaginary line L2).

[0046] In addition, Figure 4 In the example shown, the ratchet 60 is configured such that, when the front pawl 61 engages with the rack portion 32 and prevents the plunger 30 from moving to the rearward side, the tip of the front pawl 61 is located further forward than the rotation center 64 of the ratchet 60 in the front-rear direction X (in other words, further forward than the second imaginary line L2), while the tip of the rear pawl 62 is located further rearward than the rotation center 64 of the ratchet 60 in the front-rear direction X (in other words, further rearward than the second imaginary line L2).

[0047] Moreover, in the above-described structure Figure 4 In the example shown, the distances A to C are configured such that A > C ≧ B.

[0048] The ratchet spring 70 is formed as a helical spring, and as... Figure 2 The device is configured such that one end is located on the housing 20 and the other end is located on the ratchet 60, and force is applied to the ratchet 60 so that the ratchet 60 rotates in the direction in which the front pawl 61 moves to the rear (the direction in which the front pawl 61 engages with the rack portion 32).

[0049] Next, the following is based on Figures 5A to 5C The operation of the ratchet 60 and the like in the tensioning device 10 of this embodiment will be explained. Furthermore, although the following description uses... Figure 3 The example shown illustrates the action of ratchet 60, etc., but... Figure 4 In the example shown, the action of ratchet 60 and others is the same.

[0050] First, on the tensioning device 10, such as Figure 5A As shown, the movement of the plunger 30 is prevented by engaging the front pawl 61 of the ratchet 60, which is stressed by the ratchet spring 70, with the rack portion 32 formed on the outer peripheral surface of the plunger 30.

[0051] At this time, as Figure 5A As shown, the front claw 61 engages with the rack teeth 33 of the rack portion 32 with almost no gap. In addition, the additional claw 63 does not contact the rack portion 32 (there is a small gap between it and the rack portion 32). Furthermore, the rear claw 62 also does not contact the rack portion 32.

[0052] Alternatively, the ratchet 60 can be configured such that, while the front pawl 61 engages with the rack portion 32 to prevent the plunger 30 from moving to the rearward side, the additional pawl 63 also contacts the rack portion 32.

[0053] Next, as Figure 5A As shown, when the piston 30 is prevented from moving to the rearward side by engaging the front pawl 61 with the rack portion 32, the tension of the transmission chain CH decreases, the piston 30 moves forward relative to the housing 20, the ratchet 60 rotates, and then transitions to the state where the rear pawl 62 contacts the rack portion 32, the operation of the ratchet 60 is as follows.

[0054] First, from Figure 5A In the state shown, when the plunger 30 moves forward, the front pawl 61 (the rear part) is pressed forward by the rack part 32 (rack teeth 33), and the ratchet 60 rotates.

[0055] Subsequently, as the plunger 30 moves further forward, the ratchet 60 rotates, as... Figure 5B As shown, in addition to the front claw 61 (the rear part), the additional claw 63 (the rear part) also becomes in contact with the rack part 32.

[0056] Subsequently, when the plunger 30 moves further forward, the ratchet 60 rotates, and the front pawl 61 (the rear part) separates from the rack 32, so that only the additional pawl 63 (the rear part) contacts the rack 32.

[0057] Subsequently, as the plunger 30 moves further forward, the ratchet 60 rotates, as... Figure 5C As shown, in addition to the additional claw 63 (rear part), the rear claw 62 (rear part) also becomes in contact with the rack part 32.

[0058] Subsequently, as the plunger 30 moves further forward, the ratchet 60 rotates, and the rear portion of the additional pawl 63 separates from the rack portion 32, so that only the rear portion of the rear pawl 62 is in contact with the rack portion 32.

[0059] Furthermore, as the plunger 30 moves further forward, the ratchet 60 rotates, and the rack tooth 33, which engages with the rear pawl 62, passes over the rear pawl 62 on the forward side. As a result, each pawl 61 to 63 engages with a new rack tooth 33 (the next rear rack tooth 33 after the previously engaged rack tooth 33). Consequently, the tension rod G is pressed by the plunger 30 and undergoes a rocking displacement, thus following the extension of the drive chain CH.

[0060] Furthermore, although in the above, there exists a situation where, during the transition from the state where only the front claw 61 is in contact with the rack portion 32 to the state where only the additional claw 63 is in contact with the rack portion 32, there are... Figure 5B The state in which both the front pawl 61 and the additional pawl 63 are in contact with the rack portion 32 has been described. However, it is also possible to eliminate the state in which both the front pawl 61 and the additional pawl 63 are in contact with the rack portion 32, and design the ratchet 60 to directly transition from the state in which only the front pawl 61 is in contact with the rack portion 32 to the state in which only the additional pawl 63 is in contact with the rack portion 32.

[0061] Furthermore, similarly, although in the above, there exists a transition from the state where only the additional claw 63 contacts the rack portion 32 to the state where only the rear claw 62 contacts the rack portion 32, as shown above, during the transition, there is a situation where... Figure 5CThe state in which both the additional pawl 63 and the rear pawl 62 are in contact with the rack portion 32 has been described. However, it is also possible to eliminate the state in which both the additional pawl 63 and the rear pawl 62 are in contact with the rack portion 32, and design the ratchet 60 to directly transition from the state in which only the additional pawl 63 is in contact with the rack portion 32 to the state in which only the rear pawl 62 is in contact with the rack portion 32.

[0062] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Various design changes can be made without departing from the scope of the claims.

[0063] For example, although the above embodiment describes the case where the tensioning device is installed in a timing system for an automobile engine, the specific uses of the tensioning device are not limited to this.

[0064] Furthermore, although the above embodiment describes the case where the tensioning device applies tension to the drive chain via a tensioning rod, it is also possible to configure the drive chain to be slidably guided directly by the top of a plunger and to apply tension to the drive chain.

[0065] Furthermore, it is not limited to transmission mechanisms with transmission chains, but can also be applied to similar transmission mechanisms such as belts and ropes. As long as the application requires applying tension to long objects, it can be used in various industrial fields.

[0066] Furthermore, although the above embodiment describes the case where one additional claw is formed between the front claw and the rear claw, it is also possible to provide two or more additional claws that are formed side by side in the front-rear direction between the front claw and the rear claw.

Claims

1. A tensioning device, It comprises: a housing having a housing bore formed by opening to the front side; a plunger configured within the housing bore for movement in the front-rear direction and having a rack portion on its outer peripheral surface, the rack portion having a plurality of rack teeth arranged side-by-side in the front-rear direction; a main force-applying unit for applying force to the plunger towards the front side; and a ratchet rotatably mounted on the housing and having a front pawl and a rear pawl formed apart in the front-rear direction on a side disposed opposite to the rack portion. Furthermore, it is configured such that the front pawl engages with the rack portion to prevent the plunger from moving rearward, characterized in that... The ratchet has an additional pawl formed in the front-rear direction between the front pawl and the rear pawl on a side disposed opposite to the rack portion. The ratchet is formed such that, From the state where the front pawl engages with the rack portion, preventing the plunger from moving rearward, the plunger moves forward relative to the housing, causing the ratchet to rotate and transitioning to the state where the rear pawl contacts the rack portion. The state changes from a state where only the front claw is in contact with the rack portion to a state where both the front claw and the additional claw are in contact with the rack portion, then to a state where only the additional claw is in contact with the rack portion, then to a state where both the additional claw and the rear claw are in contact with the rack portion, and finally to a state where only the rear claw is in contact with the rack portion.

2. The tensioning device according to claim 1, characterized in that, The ratchet is configured such that, in a state where the front pawl engages with the rack portion to prevent the plunger from moving rearward, the tip of the additional pawl is located further forward in the front-rear direction than the center of rotation of the ratchet. Furthermore, the configuration is such that, in a state where the front pawl engages with the rack portion to prevent the plunger from moving rearward, when the distance from the rotation center of the ratchet to the tip of the front pawl in the lateral direction orthogonal to the front-rear direction is defined as A, the distance from the rotation center of the ratchet to the tip of the additional pawl in the lateral direction is defined as B, and the distance from the rotation center of the ratchet to the tip of the rear pawl in the radial direction centered on the rotation center of the ratchet is defined as C, the relationship A≧B>C is satisfied.

3. The tensioning device according to claim 1, characterized in that, The ratchet is configured such that, in a state where the front pawl engages with the rack portion to prevent the plunger from moving rearward, the tip of the additional pawl is located in the front-rear direction either further rearward than the center of rotation of the ratchet or at the same position as the center of rotation of the ratchet. Furthermore, the configuration is such that, in a state where the front pawl engages with the rack portion to prevent the plunger from moving rearward, when the distance from the rotation center of the ratchet to the tip of the front pawl in the lateral direction orthogonal to the front-rear direction is defined as A, the distance from the rotation center of the ratchet to the tip of the additional pawl in the lateral direction is defined as B, and the distance from the rotation center of the ratchet to the tip of the rear pawl in the radial direction centered on the rotation center of the ratchet is defined as C, the relationship A>C≧B is satisfied.

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