JPH042829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a breakage prediction device for a cogged belt in an apparatus in which a cogged belt is passed between a pair of pulleys to transmit power.

An internal combustion engine is equipped with an intake valve and an exhaust valve, and these valves are opened and closed at predetermined timings. In order to open and close the cylinder block, in conventional engines, a camshaft is provided on the lower side of the cylinder block. The valves and exhaust valves were opened and closed. Such a valve opening/closing mechanism has a large number of intermediate parts and an increased weight, resulting in large inertia and is not suitable for increasing the speed of the engine. Therefore, overhead camshaft type engines, in which a camshaft equipped with cams for opening and closing intake and exhaust valves is disposed at the top of the engine, are becoming widely used.

When such an overhead camshaft is used, the camshaft is located at a distance from the crankshaft, so that the power is generally transmitted via a cog belt. Cogged belts have teeth formed on their inner periphery, which makes it possible to accurately transmit rotation without causing slips. Therefore, by using the cogged belt, the intake valve and the exhaust valve can be opened and closed accurately. However, if this cogged belt breaks, not only will the intake and exhaust valves no longer open and close, but there is also a risk of valve crash due to interference with the piston that has risen toward top dead center. As a result, the engine will be damaged. Conventionally, countermeasures have been taken, such as providing a warning lamp that is linked to the mileage meter, and having the warning lamp light up every 100,000 km of driving, for example, to notify the driver that it is time to replace the cogged belt.
However, there is no guarantee that all cogged belts will not break during a mileage of 100,000 km, and the lifespan of a cogged belt changes depending on the tension applied to the belt or the manner in which it is used. There was also a possibility that the cogged belt would break at a distance of less than Km.

In order to avoid such a situation, for example, as seen in Japanese Unexamined Patent Publication No. 49-46054, in order to detect a slip in a belt stretched between a pair of pulleys, the rotational speed of both pulleys is compared, Some motors are designed to activate an alarm when this rotational difference exceeds a predetermined value.

However, with this method of detecting belt slip based on the rotational difference between a pair of pulleys, it is not possible to detect the difference in rotational phase between the two pulleys due to elongation of the belt. Therefore,
For example, it is unsuitable as a monitoring means for a transmission mechanism in which the rotational phase must be maintained with high precision, such as when driving a camshaft of an engine.

The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately detect even the temporary elongation of the belt, thereby increasing the accuracy of predicting breakage of the cogged belt.

In order to achieve such an object, the present invention provides a device in which a plurality of cogged belts are stretched between a pair of pulleys to transmit power, and a means for detecting the rotational phase of each of the pair of pulleys is provided. and phase difference detection means for predicting breakage of the cogged belt by activating a warning device when the difference between the rotational phases of both pulleys detected by these detection means becomes larger than a predetermined value;
Moreover, the power transmission capacity of each of the cogged belts alone is larger than the maximum value of the power transmitted between the pair of pulleys.

In the cogged belt cut prediction device configured in this way, the rotational phases of a pair of pulleys that are interlocked via a plurality of cogged belts are constantly monitored, and the rotational phase difference between the two pulleys is set to a predetermined value (tolerable value). ), a warning device is activated to predict the cogged belt breakage.

Therefore, not only when a slip occurs between the cogged belt and the pulley, but also when the belt elongates before the slip occurs or remains due to breakage or deterioration of one cogged belt among multiple cogged belts. Since it is possible to accurately detect even a temporary shift in the rotational phase due to an increase in the tension of the cogged belt, it is possible to more accurately detect the time to replace the cogged belt.

Embodiments of the present invention will be described in detail below based on the drawings. The drawing shows a cogged belt breakage prediction device according to this embodiment, and an engine equipped with this prediction device has a crankshaft 1. A crankshaft 1 has the same number of crank pins 2 as the number of cylinders of an engine, and these crank pins 2 are connected to a piston via a connecting rod. Further, a toothed pulley 3 is fixed to the tip of the crankshaft 1. On the other hand, an overhead camshaft 4 is arranged at the top of this engine. The camshaft 4 includes cams 5 and 6 for opening and closing intake valves and exhaust valves, respectively, corresponding to each cylinder.
is provided. Further, a toothed pulley 7 is attached to the tip of the camshaft 4. For example, two cogged belts 8 are connected between this pulley 7 and the pulley 3 of the crankshaft 1.
is being handed over.

Rotation detection sensors 9 and 10 are provided on the outer peripheral sides of the pulley 3 attached to the crankshaft 1 and the pulley 7 attached to the camshaft 4. These sensors 9 and 10 are composed of sensors that generate pulses corresponding to the teeth of the pulleys 3 and 7 using, for example, magnetism, and the detection outputs of these sensors 9 and 10 are supplied to a phase difference detection circuit 11. It is becoming more and more like this. This phase difference detection circuit 11 is connected to a drive circuit 12.
The drive circuit 12 is adapted to drive a warning device 13.

In the above configuration, the rotation of the crankshaft 1 is transmitted to the overhead camshaft 4 via the pulley 3, the cogged belt 8, and the pulley 7, and the cam 5 provided on the camshaft 4 , 6 open and close the intake valve and the exhaust valve, respectively. The camshaft 4 is configured to rotate at 1/2 the rotation speed of the crankshaft 1. And crankshaft 1 at this time
The phase difference between the rotations of the camshaft 4 and the camshaft 4 is detected by a pair of rotation detection sensors 9 and 10, and the phase difference between them is detected by a phase difference detection circuit 11. If the phase difference between the pulses obtained from the two sensors 9 and 10 does not exist and is normal, the detection circuit 11 does not supply a control signal to the drive circuit 12, and therefore the drive circuit 12 is activated by the warning device. 13 will not be activated.

Next, if one of the pair of cogged belts 8 is damaged and cut for some reason, this will prevent the other belt 8 from transmitting the rotational force from the crankshaft 1 to the camshaft 4. It will be done. At this time, twice the load will be applied to the remaining belt 8, and as a result, the belt 8 will be stretched under a large tension. Therefore, depending on the elongation of the remaining belt 8, a phase difference is generated between the pulses of the rotation detection sensors 9 and 10, and this phase difference is detected by the phase difference detection circuit 11. Become. Therefore, in this case, a control signal is supplied from the detection circuit 11 to the drive circuit 12, and the drive circuit 12 operates the warning device 13. The operation of the warning device 13 notifies the driver that the cogged belt 8 has been cut. Note that the pair of cogged belts 8 are as follows:
Each alone has sufficient strength to transmit rotational force from the crankshaft 1 to the camshaft 4, so even if one cogged belt 8 breaks, the camshaft 4 will still be driven by the other cogged belt 8. Therefore, the normal operation of the engine is not disturbed, and therefore, no valve crash occurs. Also a pair of belts 8
If one of the belts elongates abnormally due to fatigue due to long-term use, for example, a large load will be placed on the other belt 8 and a phase difference will occur between the outputs of the sensors 9 and 10. Abnormal elongation of the belt 8 can be detected by this.

As described above, according to the break prediction device for the cogged belts 8 according to the present embodiment, when one of the pair of cogged belts 8 is cut or abnormally stretched, the warning device 13 responds accordingly. is activated, the cut or extension of the cogged belt 8 is notified, and the cogged belt 8 can be replaced accordingly. Moreover, even if one cogged belt 8 breaks, the other cogged belt 8
As a result, normal operation of the engine can be continued, thereby preventing damage to the engine. The pair of cogged belts 8 have the strength to drive the camshaft 1 independently, as described above.
Furthermore, since there is almost no possibility that the pair of cogged belts 8 will break at the same time, it is possible to reliably prevent engine troubles such as valve crashes.

Although the present invention has been described above with reference to an illustrated embodiment,
The present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiment, when one of the pair of cogged belts 8 is cut, the phase shift of the camshaft 4 due to the elongation of the other cogged belt 8 is detected. Breaking of the cog belt may be predicted by detecting a phase difference caused by elongation. Alternatively, it is also possible to wrap three or more cogged belts. Further, in the above embodiment, the detection outputs of the pair of sensors 9 and 10 are supplied to the phase difference detection circuit 11, but instead of the phase difference detection circuit 11, a microcomputer is used to perform the warning. It's okay.

As described above, the present invention provides means for detecting the rotational phase of each of a pair of pulleys, and uses these detection means to detect the phase difference between the pair of pulleys to predict breakage of the cogged belt. Because of this, it is possible to accurately predict the breakage of the cogged belt, thereby making it possible to prevent damage to the machine.

In addition, by wrapping multiple cogged belts whose individual power transmission capacity is greater than the maximum value of the power transmitted between the pair of pulleys, even if one of the cogged belts breaks, the interlocking function of both pulleys can be maintained. Therefore, the transmission function will not be impaired even in the unlikely event that the transmission mechanism uses the cogged belt, and the reliability of the transmission mechanism using the cogged belt can be increased.

[Brief explanation of drawings]

The drawing is a front view showing an overhead camshaft driving device equipped with a cogged belt cut prediction device according to an embodiment of the present invention. In addition, in the symbols used in the drawings, 1... crankshaft, 3, 7... toothed pulley, 4...
Overhead camshaft, 8... Cog belt, 9, 10... Rotation detection sensor, 11... Phase difference detection circuit, 12... Drive circuit, 13... Warning device.

Claims (1)

[Claims] 1. In a device in which a plurality of cogged belts are stretched in parallel between a pair of pulleys to transmit power, a signal corresponding to the rotational phase of the pair of pulleys interlocked via the cogged belts is transmitted. A rotation detection sensor that outputs and a phase difference that operates a warning device to predict breakage of the cogged belt when the rotation phase difference between both pulleys calculated based on the outputs of these rotation detection sensors exceeds a predetermined value. a detection circuit, and each cogged belt stretched in parallel between the pair of pulleys has an independent power transmission capacity greater than the maximum value of the transmission power between the pair of pulleys interlocked via the cogged belt. A cogged belt cut prediction device featuring: 2. The cogged belt cut prediction device according to claim 1, wherein the pair of pulleys are respectively attached to a crankshaft and an overhead camshaft of an engine.