JP6284269B2 - How to check the skipping of the timing chain - Google Patents

Description

  The present invention relates to a timing chain mountain jump check method, and more particularly, to a method of checking whether or not a timing chain mountain jump occurs in an engine valve train.

  Engine drive systems that drive opening and closing of intake valves and exhaust valves are of chain drive type and belt drive type, and the rotation of the crankshaft is transmitted to the camshaft via a timing chain or timing belt. In the case of the chain drive type shown in FIG. 3, the timing chain 8 is wound around the crank sprocket 2 fixed to the end of the crankshaft and the cam sprockets 4 and 6 fixed to the ends of the intake and exhaust camshafts. is there. A tension side guide 10 having a chain tensioner and a chain guide 12 apply tension to the timing chain 8 to adjust the elongation to a constant level.

  Timing adjustment is performed to match the rotation phases of the crankshaft and the camshaft. Conventionally, sprockets 2, 4, 6 and the timing chain 8 are provided with alignment marks, and the timing chain 8 is connected to the sprockets 2 to 6 so that the alignment marks on the sprockets 2 to 6 are aligned with the alignment marks on the timing chain 8 side. It is common to wrap. FIG. 4 shows an example in which a round protrusion 26 is provided on the sprocket and one link plate 28 of the timing belt is colored. In this case, the projection 26 and the link plate 28 that can be distinguished from others by coloring correspond to a kind of alignment mark.

  Then, after the timing chain 8 is wound around the sprockets 2 to 6, it is inspected whether the timing chain 8 is assembled at a predetermined position of the sprockets 2 to 6, in other words, there is no mountain jump. Here, mountain jumping means that the link plate of the timing chain is hung not on a sprocket mountain (tooth) to be originally hung but on a mountain (teeth) adjacent to one another or two or more apart.

  In the above inspection, as in the assembly work, the operator visually confirms whether the alignment mark matches (see FIG. 4), and determines OK / NG.

Japanese Patent Laid-Open No. 08-135468

  As described above, since the inspection relies on the visual inspection of the operator, a defective product due to human error such as oversight or mistake may occur. However, it is well known that human error is inevitable, and in order to eradicate such an artificial error, it is necessary to change the confirmation based on visual observation.

  It is conceivable to employ a check method using an image analysis technique instead of visual inspection by an operator. However, capital investment for that purpose is necessary, and the possibility of misjudgment cannot be eliminated.

  An object of the present invention is to confirm the presence or absence of mountain jumps at a stage immediately after assembling a timing chain without incurring a great deal of cost.

  According to the present invention, the cam phase is determined based on the cam profile of the cam exposed on the upper surface of the cylinder block, and the presence of jumping is checked by comparing the phase of the intake side cam and the phase of the exhaust side cam. It is.

  That is, the present invention is a method for checking whether or not there is a jump in the timing chain based on the relationship between the phase of the crankshaft and the phase of the camshaft with the timing chain wound around the crankshaft timing sprocket and the camshaft timing sprocket. Thus, a height measurement step, a phase conversion step, and a phase comparison step are included.

In the height measuring step, the height from the center of the cam to the measuring point on the cam profile is measured by applying a measuring element to each of the cam nose of the intake side cam and the cam nose of the exhaust side cam.

  In the phase conversion step, the phases of the intake side cam and the exhaust side cam are obtained from the height measurement value obtained in the height measurement step. The height from the center of the cam to the measurement point and the phase, that is, the angular position, can be easily obtained based on the coordinate data of the measurement point on the cam profile.

  In the phase comparison step, the phase of the intake cam and the phase of the exhaust cam obtained in the phase conversion step are compared. Then, based on both phases, it is determined whether the phase of the crankshaft and the phase of the camshaft match. If the phase of the intake side cam and the phase of the exhaust side cam match, it can be determined that the phases of the crankshaft and the camshaft match, in other words, there is no skipping of the timing chain. Conversely, if the phase of the intake side cam and the phase of the exhaust side cam do not match, it can be determined that the phases of the crankshaft and the camshaft do not match, in other words, there is a jump in the timing chain.

  According to the present invention, since it is not an inspection that relies on the visual observation of the operator, it is possible to reliably check whether there is a mountain jump. If it is determined that there are jumps, the assembly of the engine has not been completed at this stage, and the timing chain is in a wound state. Necessary measures such as taking can be taken quickly.

It is a schematic diagram for demonstrating embodiment of this invention. It is a schematic diagram of a cam profile. 1 is a schematic diagram of an engine valve system. It is a fragmentary perspective view of the sprocket and timing chain for demonstrating the prior art.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Phase Checking Step When checking the timing chain for jumping, first turn the crankshaft to the phase for measurement while turning the timing chain 8 around the sprockets 2, 4 and 6 (see FIG. 3). . This is called a phase out process.

Here, the phase for measurement means an angular position at which the cam is in an easy-to-measure posture. For example, the cams 16a and 16b shown in FIG. 1 have a phase (angular position) in which the cam nose is directed upward or obliquely upward. When the cam is in this phase, the heights (H ₁ , H ₂ ) are applied to the intake side cam 16a and the exhaust side cam 16b exposed from the upper surface of the cylinder head indicated by reference numeral 20 by applying the measuring elements 14a, 14b from above. Easy measurement work when measuring. Further, as can be seen from FIG. 2 illustrating the cam profile, the cam heel 24 has an arc shape and the distance from the center O of the cam, that is, the radius is the same, so that no significant difference is obtained even if the cam heel 24 portion is measured. Because.

However, since the contour of the cam nose 22 is substantially symmetric, there are portions where the height (H ₁ , H ₂ ) of the measurement point is the same and the phase is different before and after the top of the cam nose 22 as viewed in the rotational direction. Therefore, it is desirable to avoid the vicinity of the top of the cam nose 22 for the portions to which the measuring elements 14a and 14b are applied.

  As a specific example, as indicated by the symbol θ in FIG. 2, it is desirable to set a measurement point at a position away from the top of the cam nose 22 by ± θ ° or more, that is, to apply the measuring elements 14 a and 14 b to the position. When the number of teeth of the sprocket is 36, a phase shift of 10 ° occurs when one mountain jumps, so the height is mistakenly the same by excluding the ± 10 ° angle region across the top of the cam nose 22 But you don't have to worry about measuring parts with different phases.

Height Measurement Step Next, the measuring elements 14a and 14b are applied to the intake side cam 16a and the exhaust side cam 16b, respectively, and the height of the measurement points 18a and 18b, that is, the measurement point 18a on the cam profile from the cam center O, The heights H ₁ and H _{2 up} to 18b are measured. This is called a height measurement process.

  The major axis of the cam is sometimes called the cam height, but the height of the measurement point here is different from that.

Here, as shown in FIG. 1, the upper surface 20 of the cylinder head coincides with the camshaft, and therefore also the center O of the cam, so that the contact points 14a and 14b are applied with the upper surface 20 of the cylinder head as a reference. The readings of the measuring elements 14a and 14b represent the heights of the measuring points 18a and 18b. In the examples, a linear scale was used to measure the heights H ₁ and H ₂ .

Phase conversion step The measured values of the heights H ₁ and H ₂ of the measurement points 18a and 18b obtained in this way are converted into the phases of the cams 16a and 16b, that is, the angular positions. This is called a phase conversion step.

  If the height from the center O of the cams 16a and 16b to the measurement points 18a and 18b is known based on the cam profile, the angle from the top of the cam nose 22 to the measurement points 18a and 18b can be known. Therefore, the height and the angle can be associated with each other in every region of the cam nose 22 in the cam profile and can be stored in a database in advance.

  Based on the measurement result, it is determined whether or not the phase relationship between the crankshaft and the intake cam 16a is correct. At this stage, the crank has already been phased out, so if it jumps to either the leading or lagging side in the rotational direction, it can be detected here.

Next, the phase of the intake cam 16a is compared with the phase of the exhaust cam 16b. This is called a phase comparison process.

  By comparing both phases, it is possible to confirm the presence or absence of a mountain jump. That is, if the phase of the intake side cam 16a and the phase of the exhaust side cam 16b match, it is determined that the phases of the crankshaft and the camshaft match, in other words, there is no mountain jump of the timing chain 8.

  Conversely, if the phase of the intake side cam 16a and the phase of the exhaust side cam 16b do not match, it is determined that the phases of the crankshaft and camshaft do not match, in other words, there is a mountain jump of the timing chain 8. . For example, in the case where the number of teeth of the sprocket already described is 36, a difference of 10 ° will occur if one sprocket is mistaken, so how many jumps are present based on the phase (angle) difference. Can be judged immediately.

  While the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the embodiments described and illustrated herein, and various modifications can be made without departing from the scope of the claims. Can do.

  The concept of the present invention can also be applied when checking for the presence or absence of a timing belt jump.

2 Crank sprocket 4 Cam sprocket (intake side)
6 Cam sprocket (exhaust side)
8 Timing chain 10 Tension side guide 12 Chain guide 14a Measuring element (intake side)
14b Measuring element (exhaust side)
16a Intake side cam 16b Exhaust side cam 18a Measuring point 18b Measuring point 20 Cylinder head upper surface (cam center position)
22 cam nose 24 cam heel

Claims (1)

A method of checking whether or not there is a jump in the timing chain based on the relationship between the phase of the crankshaft and the phase of the camshaft in a state where the timing chain is wound around the crank sprocket and the cam sprocket,
A height measuring step of measuring the height from the center of the cam to the measuring point on the cam profile by applying a measuring element to the cam nose of the intake side cam and the cam nose of the exhaust side cam;
A phase conversion step for obtaining the phase of the intake side cam and the exhaust side cam from the height measurement value obtained in the height measurement step;
A method for checking a jump in a timing chain including a phase comparison step of comparing the phase of the intake cam and the phase of the exhaust cam obtained in the phase conversion step.

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