JP4204501B2 - Automatic valve clearance adjustment device - Google Patents

Description

  The present invention relates to an automatic valve clearance adjusting device incorporated in a valve mechanism of an internal combustion engine.

  The valve mechanism of the internal combustion engine includes a direct type that directly opens and closes the valve by a camshaft provided on the axis of the reciprocating motion, and an arm that swings with a position off the axis of the reciprocating motion of the valve as a fulcrum. It can be roughly divided into the arm type performed via Among arm types, there is a so-called swing arm type that does not have a fixed shaft that penetrates the fulcrum, supports one end of the arm with a pivot, and reciprocates the valve at the other end of the arm.

  In the above swing arm type valve mechanism, the valve clearance (clearance between the valve shaft end and the other end of the arm) is usually kept constant against variations in assembly accuracy, wear of the valve seat, thermal expansion of the cylinder head, and the like. In order to maintain, an automatic valve clearance adjustment device called a lash adjuster is incorporated on the pivot side. As this lash adjuster, in addition to the hydraulic type, one using a sawtooth screw has been proposed (for example, see Patent Documents 1 and 2).

  FIG. 3 shows an example of a swing arm type valve operating mechanism incorporating a conventional sawtooth screw type lash adjuster 51. In this valve operating mechanism, when the camshaft 3 rotates and pushes the central portion of the arm 5 with the cam 4 from the closed state of the valve 2 shown in FIG. 3, the arm 5 swings with its one end supported by the lash adjuster 51. Then, by pushing down the valve 2 at the other end, the valve 2 is separated from the valve seat 7 attached to the cylinder head 6 and is opened. When the cam 4 moves away from the arm 5, the valve 2 is pulled back by the force of the valve spring 8 and closed again.

  The lash adjuster 51 incorporated in the valve operating mechanism includes an arm support member 52 having a pivot portion 52a for supporting one end portion of the arm 5 and a male screw portion 52b having a sawtooth screw formed on the outer peripheral surface thereof. A cylindrical female screw member 53 that is screw-coupled to the support member 52 and a spring member 54 that urges the arm support member 52 in a direction to press the arm support member 52 against one end of the arm 5 are provided, and the male screw portion 52b of the arm support member 52 and Designed so that the sawtooth screw formed on the inner periphery of the female screw member 53 is locked when it receives a pressing load from the arm 5 and generates a sliding rotation by the biasing force of the spring member 54 when the pressing load is released. Has been. The female screw member 53 is fixed to the holding hole 6 a of the cylinder head 6 by fitting a bottom lid 55 that supports the spring member 54 into the lower end side opening.

  Therefore, when the valve is opened, the arm support member 52 that has received the pushing load from the arm 5 is pushed by the backlash of the screw, and then stops by locking the sawtooth screw. When the sawtooth screw is locked, a slight sliding rotation occurs, and this sliding rotation is caused by the backlash of the screw by the urging force of the spring member 54 when the arm support member 52 is released from the pushing load when the valve is closed. It is offset by sliding and rotating only after being pushed up. As a result, the valve operating mechanism can open the valve 2 with a constant valve lift by the arm 5 being supported by the pivot portion 52a of the arm support member 52 at a constant position.

  When the valve clearance increases due to wear of the shaft end of the valve 2 or thermal expansion of the cylinder head 6, the arm support member 52 pushes up one end of the arm 5 until the clearance disappears due to the above-described sliding rotation when the valve is closed. Therefore, the clearance increase is absorbed immediately. On the other hand, when the valve clearance decreases due to thermal expansion of the valve 2 or wear of the valve seat 7, the arm support member 52 is prevented from moving axially at one end of the arm 5 until it is pushed up by the backlash of the screw when the valve is closed. Therefore, the clearance is gradually screwed into the female screw member 53 by the slight sliding rotation at the time of opening the valve, so that the clearance reduction is gradually absorbed. By these operations, the valve clearance of the valve operating mechanism is automatically adjusted.

  By the way, in this lash adjuster 51, the pushing load that the arm support member 52 receives from the arm 5 is supported by the bottom surface of the holding hole 6a of the cylinder head 6 via the cylindrical female screw member 53. Accordingly, the surface pressure between the lower end surface of the female screw member 53 and the bottom surface of the holding hole 6a of the cylinder head 6 is considerably large. When the cylinder head 6 is formed of aluminum for weight reduction, the holding hole 6a Abnormal wear may occur on the bottom.

  On the other hand, when the female screw member (fixing member) is integrally formed in a bottomed cylindrical shape as in the lash adjuster described in Patent Document 1, there is a concern that abnormal wear may occur in the holding hole of the cylinder head. There is no. However, since it is desirable to design the female screw member as short as possible for downsizing the internal combustion engine, when it is formed in a bottomed cylindrical shape, even if the tap is screwed until it hits the bottom during tapping, the female screw part Often the axial length is not sufficient.

As shown in FIG. 4A, when the axial length of the female threaded portion 53 a is shortened by forming the female threaded member 53 in a bottomed cylindrical shape, the arm support member 52 applies a pushing load from the arm 5. Easy to tilt when receiving. In addition to the fact that the direction of the indentation load is deviated from the axial direction of the arm support member 52, as shown in FIG. 4B, the straight portion between the female screw portion 53 a and the bottom portion 53 b of the female screw member 53. 53c is formed so as to take a gap δ _{1B of a} size that generally does not cause contact with the male threaded portion 52b of the arm support member 52. Compared to the example of FIG. This is because there are few parts to regulate. If the inclination of the arm support member 52 is increased to some extent, there arises a problem that the arm support member 52 cannot perform a smooth rotation operation, and the thread surfaces of the arm support member 52 and the female screw member 53 are unevenly worn.

In particular, as shown in FIGS. 5A and 5B, when the arm support member 52 is screwed into the female screw member 53, the length of engagement of both screws is shortened, and the arm support that has entered the female screw member 53 is supported. Since the gap δ _2B between the straight portion 52c of the member 52 and the female screw portion 53a is wide, the portion that restricts the inclination of the arm support member 52 is further reduced, and the arm support member 52 is more easily inclined. Therefore, in this state, there is a high possibility that the above problem will occur.
US Pat. No. 4,981,117 Japanese Utility Model Publication No. 4-44407

  An object of the present invention is to make it possible to stably use an automatic valve clearance adjusting device using a sawtooth screw for a long period of time.

  As one means for solving the above-described problems, the present invention is incorporated in a valve operating mechanism that opens and closes a valve by swinging an arm that supports one end, and a pivot that supports one end of the arm. And an arm supporting member having a male threaded portion that is screw-coupled to the inner surface of the bottomed cylindrical fixing member, and a spring member that biases the arm supporting member in a direction in which the arm supporting member is pressed against one end of the arm. A saw-toothed screw that locks to the male threaded portion of the member and the female threaded portion of the fixing member when receiving a pressing load from the arm and causes a sliding rotation by the biasing force of the spring member when the pressing load is released. In the formed valve clearance automatic adjusting device, the fixing member has a straight portion between the female screw portion and the bottom portion, and the inner diameter of the straight portion of the fixing member The symbol representing the position of the tolerance zone of the shaft in the hole reference fit in JIS standard (JIS B 0401) for the gap with the outer diameter of the male threaded portion of the arm support member is one of d, e, f, g, and h. A configuration with a size corresponding to the clearance fit of the case was adopted.

  That is, the axial length of the female threaded portion of the fixing member is relatively short by reducing the clearance between the straight inner diameter of the bottomed cylindrical fixing member and the outer diameter of the male threaded portion of the arm support member to a degree of clearance fit. However, when the arm support member receives a pushing load from the arm, the inclination of the arm support member is regulated by the straight portion of the fixed member while being tilted only slightly, thereby stabilizing the posture of the arm support member. .

  According to the present invention, as another means for solving the above-described problem, in the automatic valve clearance adjusting device, the arm support member has a straight portion between the pivot portion and the male screw portion. The clearance between the outer diameter of the straight portion of the member and the inner diameter of the female screw portion of the fixing member is represented by the symbols d, e, f, g, h indicating the position of the tolerance zone of the shaft in the hole standard fit in JIS standard (JIS B 0401). A configuration with a size corresponding to the clearance fit clearance in either case was adopted.

  That is, by reducing the clearance between the outer diameter of the straight portion of the arm support member and the inner diameter of the female screw portion of the fixing member to a degree of clearance fit, the length of the arm support member screwed into the fixing member and the engagement of both screws can be reduced. Even when a pressing load is received from the arm in a shortened state, the straight portion abuts on the female screw portion of the fixing member, the inclination is restricted, and a stable posture can be maintained.

  As described above, according to the present invention, the clearance between the straight portion inner diameter of the fixing member of the valve clearance automatic adjusting device and the outer diameter of the male screw portion of the arm support member is reduced to a clearance fit, so that the shaft of the female screw portion of the fixing member is reduced. Even when the directional length is relatively short, the tilt when the arm support member receives the pushing load can be suppressed to be extremely small, so that the arm support member can always be kept in a stable posture.

  In addition, by reducing the clearance between the outer diameter of the straight portion of the arm support member and the inner diameter of the female screw portion of the fixing member to the extent of clearance fit, the inclination of the arm supporting member that is screwed into the fixing member can be suppressed.

  Therefore, the valve clearance automatic adjusting device to which the present invention is applied ensures the smooth operation of the arm support member and is stable for a long time without causing uneven wear on the thread surfaces of the arm support member and the fixing member. Can be used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig.1 (a) shows the lash adjuster 1 as a valve clearance automatic adjustment apparatus of 1st Embodiment. This lash adjuster 1 is incorporated in the swing arm type valve operating mechanism shown in FIG. 3 in the same manner as the conventional one, and has a pivot portion 9a for supporting one end of the arm 5 of the valve operating mechanism and an outer peripheral surface. An arm support member 9 having a male screw portion 9b formed with teeth, a bottomed cylindrical female screw member 10 screwed to the arm support member 9, and a direction in which the arm support member 9 is pressed against one end of the arm 5 It comprises a spring member 11 to be urged, and a stopper 12 that is fitted to the outer periphery of the upper end portion of the female screw member 10 and prevents the arm support member 9 from coming off. The female screw member 10 is embedded and fixed in a holding hole 6a of an aluminum cylinder head 6 to which a valve mechanism is attached.

  The arm support member 9 is configured such that the pivot portion 9a is slidably fitted into the recess 5a at one end of the arm 5, and can enter the female screw member 10 between the pivot portion 9a and the male screw portion 9b. It has the straight part 9c formed.

  On the other hand, the female screw member 10 is formed at its upper part with a female screw portion 10a that is screw-coupled with the male screw portion 9b of the arm support member 9, and a part of the male screw of the arm support member 9 is provided between the female screw portion 10a and the bottom portion 10b. It has the straight part 10c facing the part 9b. This is because the female screw member 10 is integrally formed in a bottomed cylindrical shape, so that the axial length of the female screw portion 10a meshes with the entire male screw portion 9b even if the tap is screwed into contact with the bottom portion 10b during tapping. This is because it cannot be taken so long.

  The sawtooth screw formed on the male threaded portion 9b of the arm support member 9 and the female threaded portion 10a of the female threaded member 10 has a flank angle on the pressure side flank surface that receives the pushing load transmitted from the arm 5 and is attached to the spring member 11. It is formed larger than the flank angle of the sliding-side flank surface that receives the force, and locks when receiving a pressing load from the arm 5, and when the pressing load is released, sliding rotation is generated by the biasing force of the spring member 11. It has become. Thus, the lash adjuster 1 can support the arm 5 of the valve operating mechanism and adjust the valve clearance by the same mechanism as the conventional one described above.

Further, as shown in FIG. 1B, the straight portion 10c of the female screw member 10 has a gap δ _1A between the inner diameter and the outer diameter of the male screw portion 9b so that the hole standard fits in the JIS standard (JIS B 0401). It is formed to have a size corresponding to the clearance fit when the symbol representing the position of the tolerance zone of the shaft is any one of d, e, f, g, and h.

  Since the lash adjuster 1 has the above-described configuration and the female screw member 10 is formed in a bottomed cylindrical shape, the lower end surface of the female screw member 10 and the bottom surface of the holding hole 6a of the cylinder head 6 are compared with the case of a cylindrical shape having no bottom. There is no concern that abnormal wear will occur in the holding hole 6a.

Further, although the axial length of the female screw portion 10a of the female screw member 10 is relatively short, the gap δ _1A between the inner diameter of the straight portion 10c of the female screw member 10 and the outer diameter of the male screw portion 9b of the arm support member 9 is about a clearance fit. Since the arm support member 9 receives a pushing load from the arm 5, the male screw portion 9 b is in contact with the straight portion 10 c of the female screw member 10 in a state where the arm support member 9 receives a pressing load from the arm 5. Maintained posture.

  Next, a lash adjuster as a valve clearance automatic adjusting device of the second embodiment will be described. FIGS. 2A and 2B show a state in which the arm support member 9 of the lash adjuster is screwed into the female screw member 10 and the length of engagement of both screws is shortened.

In this embodiment, as shown in FIG. 2B, the straight portion 9c of the male screw member 9 has a gap δ _2A between the outer diameter and the inner diameter of the female screw portion 10a, which is a hole in the JIS standard (JIS B 0401). The reference fit is formed to have a size corresponding to the clearance fit when the symbol representing the position of the tolerance zone of the shaft is one of d, e, f, g, and h.

  Therefore, even if the arm support member 9 receives a pressing load from the arm 5 in this state, the straight portion 9c abuts on the female screw portion 10a of the female screw member 10 and the inclination is restricted, and a stable posture can be maintained. .

  FIG. 2A shows an example in which the gap between the straight portion 10c of the female screw member 10 and the male screw portion 9b is wide as in the conventional case. However, this gap is the same as in the first embodiment. It may be as small as a clearance fit. The configuration of other parts is the same as that of the first embodiment.

a is a front sectional view of the lash adjuster of the first embodiment, and b is an enlarged view of a main part of a. a is a front sectional view showing a state in which the arm support member of the lash adjuster of the second embodiment is screwed, and b is an enlarged view of a main part of a. Front sectional view of a valve mechanism incorporating a conventional lash adjuster a is a front sectional view of another conventional lash adjuster, and b is an enlarged view of a main part of a. a is a front sectional view showing a state in which the arm support member of the lash adjuster of FIG. 4 is screwed, and b is an enlarged view of a main part of a.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rush adjuster 5 Arm 5a Recess 6 Cylinder head 6a Holding hole 9 Arm support member 9a Pivot part 9b Male thread part 9c Straight part 10 Female thread member 10a Female thread part 10b Bottom part 10c Straight part 11 Spring member 12 Stopper

Claims (2)

  A pivot part that is incorporated in a valve operating mechanism that opens and closes a valve by swinging an arm supported at one end, and a male thread part that is screw-coupled to the inner surface of the bottomed cylindrical fixing member. And a spring member that biases the arm support member in a direction in which the arm support member is pressed against one end portion of the arm, and the male screw portion of the arm support member and the female screw portion of the fixing member are pushed against the arm. In the valve clearance automatic adjusting device in which a sawtooth screw is formed which is locked when received and the push load is released, and a sliding rotation is generated by the urging force of the spring member, the fixing member has its female screw portion The gap between the straight portion inner diameter of the fixing member and the male screw outer diameter of the arm support member is JIS standard. Automatic valve clearance characterized by the size corresponding to the clearance fit when the symbol indicating the position of the tolerance zone of the shaft is d, e, f, g or h Adjustment device.   A pivot part that is incorporated in a valve operating mechanism that opens and closes a valve by swinging an arm supported at one end, and a male thread part that is screw-coupled to the inner surface of the bottomed cylindrical fixing member. And a spring member that biases the arm support member in a direction in which the arm support member is pressed against one end portion of the arm, and the male screw portion of the arm support member and the female screw portion of the fixing member are pushed against the arm. In a valve clearance automatic adjusting device in which a sawtooth screw is formed which is locked when receiving the force and releases sliding movement by the biasing force of the spring member when the pushing load is released, the arm support member is pivoted A straight portion between the portion and the male screw portion, and a gap between the outer diameter of the straight portion of the arm support member and the inner diameter of the female screw portion of the fixing member. A valve characterized in that it has a size corresponding to the clearance fit when the symbol representing the position of the tolerance zone of the shaft in the JIS standard hole fit is one of d, e, f, g, and h Clearance automatic adjustment device.

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