JP4271212B2 - Clearance adjustment jig - Google Patents

Description

  The present invention relates to a jig for adjusting a clearance between members, for example, a jig for adjusting a tappet clearance and a clutch clearance between an engine valve stem and an adjustment screw of a rocker arm.

  If the clearance (tuppet clearance) between the valve stem of the engine and the adjusting screw of the rocker arm is too small, it will cause idling stability and engine stall, and if it is too large, noise will be generated. For this reason, it is necessary to accurately adjust the tappet clearance so that the above-described problems do not occur in both the cold and hot states of the engine.

  As a general tappet clearance adjustment method, there is an adjustment screw that is attached to the tip of the rocker arm and a method in which a thickness gauge is inserted between the valve stem and the adjustment screw is fed by a screwdriver until the thickness gauge is lightly pressed. However, since this method requires the skill level of the operator and there is a possibility of human error, a tappet clearance adjustment method as disclosed in Patent Documents 1 to 5 has been proposed.

  In Patent Document 1, as a wrench for feeding an adjustment screw, a flange portion is provided in the wrench body, and when a force greater than a certain level is applied by interposing a ratchet mechanism on the flange portion, the handle rotates idly and the adjustment screw is moved to the adjustment screw. The content which interrupts | blocks transmission of a driving force is disclosed.

  In Patent Document 2, the adjusting screw is tightened in a state where the slipper surface of the rocker arm is in contact with the movable cam, the displacement amount of the valve at this time is measured, and the target clearance value is added to this measured value, The content of loosening (reversing) the adjustment screw by an amount corresponding to this added value is disclosed.

  In Patent Document 3, the base end side of the rocker arm is pressed toward the reference surface of the camshaft, the adjustment screw on the other end side is fed by a screwdriver, and then the adjustment screw is returned to the displacement set value to adjust the tappet clearance. When setting the amount to be fed by the driver up to the point where the displacement of the rocker arm almost disappears even if the adjustment screw is fed, the backlash between the rocker arm and the rocker shaft and the backlash between the camshaft and its bearing Proposals have been made to avoid the problem.

  In Patent Document 4, compressed air from an air source is supplied to a port of a cylinder head with a wind speed sensor inserted into a port of an air supply head, and then an adjustment screw is rotated to press the valve to the open side. . Then, since the wind speed sensor detects that the valve starts to open and an air flow toward the valve is generated in the port, this time is set as the valve opening time, and the rotation position of the adjustment screw at this time is used as a reference. It is disclosed to adjust the tappet clearance by reversing the screw by a predetermined amount.

  In Patent Document 5, after the adjustment screw is fed until the displacement of the rocker arm reaches a stable region, the adjustment screw is loosened based on the displacement detection means so as to reduce the displacement of the rocker arm by a predetermined reference amount. A method is disclosed in which the adjustment screw is loosened by an amount obtained by subtracting the loosening amount corresponding to the reference amount of the rocker arm from the clearance setting standard value with the adjusted position as the adjustment origin.

JP 2002-235476 A JP-A-5-65810 JP-A-62-610 Japanese Unexamined Patent Publication No. 6-17619 JP 2001-27106 A

  In the method disclosed in Patent Document 1, since it is a manual type, it cannot be continuously processed, and there is no disclosure of how to determine the return amount of the adjustment screw.

  In the method disclosed in Patent Document 2, there is no particular disclosure regarding a mechanism for transmitting a driving force to a driver (output shaft) that rotates an adjusting screw. For example, the rotating speed is increased when the adjusting screw is driven, and the rotating force is slowly rotated when returning. Therefore, an accurate clearance cannot be ensured.

  In the method disclosed in Patent Document 3, the displacement rate of the rocker arm has to be obtained every time, and there are problems that it takes man-hours for adjustment and the apparatus configuration is complicated.

  In the method disclosed in Patent Document 4, the valve opening time is determined based on the value detected by the wind speed sensor. However, it is difficult to accurately detect the valve opening time, and the wind speed sensor must be inserted one by one. Inferior workability.

  Although the method disclosed in Patent Document 5 is improved over Patent Document 2, the displacement of the rocker arm must be measured by the displacement detection means, and adjustment takes time.

  In order to solve the above-mentioned problems, the present invention provides a clearance adjustment jig that adjusts the clearance between the member to be adjusted and the adjustment screw by rotating the output shaft, and the clearance adjustment jig outputs the input driving force to the output. A driving force transmission mechanism that transmits to the shaft is provided. The driving force transmission mechanism incorporates a clutch mechanism, a planetary gear mechanism, and a ratchet mechanism. When the output shaft rotates forward, the driving force is output via the clutch mechanism and the ratchet mechanism. When the resistance during forward rotation reaches a predetermined value, the ratchet mechanism is disengaged and the transmission of the driving force is interrupted. When the output shaft is reversely rotated, the driving force is transmitted via the planetary gear mechanism by the clutch mechanism. It was set as the structure transmitted to.

  Examples of the member to be adjusted include a valve stem of an engine, and the output shaft may have a structure in which an adjustment screw attached to a rocker arm is rotated.

  According to the present invention, the adjustment screw can be driven (forward rotation) via the ratchet mechanism without using a thickness gauge, so that a short time is required, and the adjustment screw return (reverse rotation) is performed via the planetary gear mechanism. Clearance can be adjusted accurately.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 3 are diagrams for explaining the procedure for adjusting the tappet clearance using the adjusting jig according to the present invention.
FIG. 1 shows a state before adjustment. One end of the rocker arm 1 is in contact with the camshaft 2, and an adjustment screw 3 is attached to the other end, and a lock nut 4 is used to prevent loosening.

  A valve stem 6 is inserted through the guide 5 fixed to the engine block, and the valve 7 at the lower end of the valve stem 6 is in contact with the valve seat 8. A spring receiver 9 is attached to the upper end of the valve stem 6, and a spring 11 is contracted between the spring receiver 9 and a spring receiver 10 provided on the outer periphery of the guide 5 to urge the valve stem 6 upward. .

  An adjustment jig 20 according to the present invention is disposed above the adjustment screw 3. An output shaft 21 that is rotated by a motor protrudes downward from the adjustment jig 20, and a nut portion 22 that engages with the upper end portion of the adjustment screw 3 is provided at the lower end of the output shaft 21.

  In the state shown in FIG. 1, a clearance is formed between the upper end portion of the valve stem 6 and the adjustment screw 3, but this is not a precisely set clearance.

  As shown in FIGS. 4 to 6, the adjusting jig 20 has an input shaft 23 connected to a motor inserted therein, and a one-way clutch 24a constituting a clutch mechanism between the input shaft 23 and the output shaft 21. 24b, 24c, 24d, ratchet mechanism 25 and planetary gear mechanism 30 are interposed. In FIG. 4, only the left half of the one-way clutches 24a, 24b, 24c, 24d and the ratchet mechanism 25 is shown in order to avoid complication of the drawing.

  The ratchet mechanism 25 includes a spring 26 and a steel ball 27, and the planetary gear mechanism 30 includes a ring gear 31, a sun gear 32, a planet gear 33, and carriers 34 and 35.

  An adjustment method using the adjustment jig 20 having the above configuration will be described with reference to FIGS. First, the adjustment jig 20 is lowered from the state of FIG. 1 to engage the nut portion 22 with the lock nut 4, and the nut portion 22 is rotated to loosen the lock nut 4.

  Next, as shown in FIG. 2, the nut portion 22 is engaged with the adjustment screw 3, the output shaft 21 is rotated forward, and the adjustment screw 3 is driven (screwed downward in the figure).

By the way, when the output shaft 21 is rotated forward, as shown in FIG.
The driving force from the input shaft 23 is transmitted to the ratchet mechanism 25 when the one-way clutch 24a is turned off, the one-way clutch 24b is turned on, the one-way clutch 24c is turned off, and the one-way clutch 24d is turned on. It is transmitted to the output shaft 21 via the carrier. In FIGS. 4 (a) and 4 (b), a thick arrow indicates a driving force transmission path.

  When the output shaft 21 is rotated forward to drive the adjustment screw 3, the reaction force of the spring 11 exceeds the resistance force against the rotation of the adjustment screw 3, and the adjustment screw 3 is driven by the ratchet mechanism 25. It turns off when seated, and the adjustment screw 3 is automatically driven.

  Thereafter, the target tappet clearance value is converted into the rotation angle of the adjusting screw 3, and the output shaft 21 is reversed.

  When the output shaft 21 is reversely rotated, as shown in FIG. 4 (b), the driving force from the input shaft 23 is such that the one-way clutch 24a is turned on and the one-way clutch 24c is turned off. It is transmitted to the output shaft 21 via 32. By transmitting the driving force via the planetary gear mechanism 30, the reduction ratio is increased, fine adjustment is facilitated, and an accurate tappet clearance can be obtained.

  When the adjustment screw 3 is rotated to adjust the tappet clearance to the set size as described above, the lock nut 4 is tightened and the adjustment jig 20 is retracted to complete the tappet clearance adjustment operation.

  In the one-way clutch 24c, when the output shaft 21 is overloaded during reverse rotation and the input shaft 23 tries to rotate, the planetary gear mechanism 30 starts to rotate and is transmitted from the steel ball 27 to the one-way clutch, which may cause idle rotation. Therefore, the one-way clutch 24c prevents it. Therefore, normally, both the forward rotation and the reverse rotation are OFF.

  FIG. 7 is a cross-sectional view of an adjusting jig according to another embodiment. In the adjusting jig 20 shown in FIG. 7, three planetary gear mechanisms 30 are provided in the vertical direction to increase the reduction ratio.

The figure explaining the procedure which adjusts tappet clearance using the adjustment jig concerning the present invention The figure explaining the procedure which adjusts tappet clearance using the adjustment jig concerning the present invention The figure explaining the procedure which adjusts tappet clearance using the adjustment jig concerning the present invention (A) The figure which showed the transmission path of the driving force at the time of forward rotation (b) The figure which showed the transmission path of the driving force at the time of reverse rotation Perspective view of planetary gear mechanism Plan view of essential parts of planetary gear mechanism Sectional drawing of the adjustment jig which concerns on another Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rocker arm, 2 ... Cam shaft, 3 ... Adjustment screw, 4 ... Lock nut, 5 ... Guide, 6 ... Valve stem, 7 ... Valve, 8 ... Valve seat, 9, 10 ... Spring receiver, 11 ... Spring, 20 ... Adjusting jig, 21 ... Output shaft, 22 ... Nut, 23 ... Input shaft, 24, 24a, 24b, 24c, 24d ... One-way clutch, 25 ... Ratchet mechanism, 26 ... Spring, 27 ... Steel ball, 30 ... Planet Gear mechanism 31 ... Ring gear, 32 ... Sun gear, 33 ... Planet gear, 34, 35 ... Carrier.

Claims (2)

A clearance adjustment jig that adjusts the clearance between the member to be adjusted and the adjustment screw by rotating the output shaft, and the clearance adjustment jig includes a driving force transmission mechanism that transmits the input driving force to the output shaft. The driving force transmission mechanism incorporates a clutch mechanism, a planetary gear mechanism, and a ratchet mechanism. When the output shaft rotates in the forward direction, the driving force is transmitted to the output shaft through the clutch mechanism and the ratchet mechanism. The clearance is characterized in that the ratchet mechanism is disengaged when the torque reaches a predetermined value, and the transmission of the driving force is interrupted, and the driving force is transmitted to the output shaft by the clutch mechanism via the planetary gear mechanism when the output shaft is reversely rotated. Adjustment jig. The clearance adjustment jig according to claim 1, wherein the member to be adjusted is a valve stem of an engine, and the output shaft rotates an adjustment screw attached to a rocker arm.