JPH0231551Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a timing belt used in a timing transmission mechanism that uses a toothed timing belt to transmit the rotation of the engine crankshaft to a driven shaft such as the camshaft of an intake/exhaust valve or the camshaft of a fuel injection pump. This invention relates to a break detection device.

Conventionally, timing transmission means for rotating a driven shaft in synchronization with the rotation timing of a crankshaft of a diesel engine include methods using gears, chains, or toothed timing belts. Among these methods, the timing belt method is widely used in automobile diesel engines because of its advantages such as low noise, light weight, and no need for lubrication, but it has problems in terms of durability for industrial use. Currently, most of them are not mass-produced.

In a diesel engine, in order to achieve high compression, the relative positions of the piston and the intake and exhaust valves are related so that a minimum gap exists. Therefore,
If the timing belt breaks, the timing of the reciprocating movement of the piston and the timing of the reciprocating movement of the intake and exhaust valves will deviate, causing interference between the two belts and causing damage to the piston, intake and exhaust valves, rocker arm, etc.

The present invention aims to take advantage of the advantages of the timing belt as described above, while compensating for the disadvantage of poor durability, thereby eliminating the risk of engine destruction.

In order to achieve this purpose, the present invention provides a timing transmission mechanism that transmits the rotation of the engine crankshaft to the driven shaft using a toothed timing belt.
The timing belt is divided into two substantially equal rows of belts wrapped around the same crankshaft and driven shaft, and detection means for detecting breakage of the two rows of timing belts is provided. The gist of the present invention is a timing belt breakage detection device characterized in that it is provided with a belt switch that is activated when a breakage of either one of the two timing belts is detected by the detection means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The timing transmission mechanism using a toothed timing belt will be explained as shown in Figs. 1 to 3.
is an OHC (overhead camshaft) type diesel engine, in which a crankshaft gear 3 is fitted to the front end of a crankshaft 2, and a camshaft 7 drives an intake and exhaust valve 5 and an exhaust valve 6 via a rocker arm 4.
A camshaft gear 8 is fitted to the front end of the fuel injection pump 9, and a fuel injection pump gear 11 is fitted to the front end of the camshaft 10 of the fuel injection pump 9. These gears 3, 8, and 11 are meshed with two toothed timing belts 12 arranged in parallel in two rows, front and rear, and the width of these two timing belts 12 in the front and rear direction is equal to that of the conventional one. The width is substantially equal to the width of one toothed timing belt, so that the space occupied by the belt in the engine is approximately the same as that of a conventional belt. A tensioner 13 tensions the timing belt 12, and is fixed after tensioning the belt with an appropriate tension during engine assembly.

Each gear 3, 8, 11 and timing belt 12
The structure is such that the driving load is equally distributed between the two belts to prevent the driving load from concentrating on one belt on one side and reducing the durability life.

As shown in FIGS. 4 and 5, the crankshaft gear 3 consists of a front gear 3a and a rear gear 3b, and a separator 14 is interposed between the gears 3a and 3b. A roughly semicircular key 1 is attached to the crankshaft 2.
5 is press-fitted, and the key 15 is connected to the gears 3a, 3.
b and the separator 14, and these members and the crankshaft 2 are fixed so as to rotate together. The gears 3a, 3b and the separator 14 are also
It is fixed in the axial direction by a bolt 17 screwed onto the plate 16 and the crankshaft 2. or,
In order to equalize the driving loads applied to the two timing belts 12, it is necessary to minimize the deviation of the teeth of the front gear 3a and the rear gear 3b in the circumferential direction.
For this purpose, first, as shown in FIG. 6a, a round bar material is subjected to a gear cutting process to form a large number of teeth 3c, a press-fit hole process to form a hole 3d into which the crankshaft 2 is press-fitted, and a key 15. A gear blank 3f is formed in advance by keyway machining to form a key groove 3e to be inserted, and then, as shown in FIG. 6b, this gear blank 3f is divided into a front gear 3a and a rear gear. 3b
It forms.

Similarly, the camshaft gear 8 includes a front gear 8a and a rear gear 8.
The fuel injection pump 11 also consists of a front gear 11a and a rear gear 11b, and these gears 8a, 8b, 11a, and 11b are formed in the same manner as described above. .

Furthermore, the toothed timing belt 12 is configured such that an equal driving load is applied to each of the two belts.
It is necessary to keep the variation in length to a minimum.
For this purpose, first, as shown in FIG. 7a, a timing belt material 12a is formed in advance, and then, as shown in FIG. Form. In this way, two timing belts 12 cut from the raw material 12a molded at the same time in the same manufacturing process form one set.

Next, a mechanism for automatically stopping the engine when either one of the timing belts 12 is cut will be described.

In the emergency automatic stop circuit when the timing belt is cut as shown in FIGS. 8a, b, and c, a solenoid valve 21
A valve member 22 is disposed, and the valve member 22 is biased in the direction of closing the fuel passage 20 by a return spring 23, and opens the passage 20 when the solenoid 24 is energized. There is.
The electric circuit that controls the energization of the solenoid 24 is
It consists of a battery 25, an engine key switch 26, and a belt switch 27 that opens when it detects that one of the timing belts 12 is cut.

In the normal engine stopped state shown in Figure 8a,
Since the engine key switch 26 is open and the belt switch 27 is closed by biasing the movable contact 29 by its return spring 28, the solenoid 24 is not energized and the valve member 22 is biased by the return spring 23. fuel passage 20
is blocking. In the operating state of the engine shown in FIG. 8c, the engine key switch 26 is closed, the solenoid 24 is energized, overcomes the force of the return spring 23, attracts the valve member 22, and the fuel passage 20 is opened. . When one of the timing belts 12 breaks while the engine is running, an input to be described later moves the movable contact 29 of the belt switch 27 in the direction of arrow _F1 overcoming the force of the return spring 28, opening the switch 27 and opening the solenoid. 24 is stopped, the fuel passage 20 is shut off by the valve member 22, and fuel is no longer supplied to the engine, so that the engine is automatically stopped.

A mechanism for detecting a break in the timing belt 12 and opening the belt switch 27 is shown in FIGS. 9a and 9b. 2, which supports at one end a roller 30 that contacts the two timing belts 12, respectively.
Two levers 31 are pivotally connected to the engine 1,
Each lever 31 is biased by a spring 32 in a direction such that the other end comes into contact with the movable contact 29 of the belt switch 27.

In the normal state shown in FIG. 9a, the rollers 30 are in constant contact with the two timing belts 12 via the levers 31 and the springs 32, and at this time, the other end of the lever 31 is connected to the belt switch 2.
7, and the switch 27 is in the closed position.

As shown in FIG. 9b, when one of the two timing belts 12 breaks, the roller 30 on which the timing belt broke comes out of contact with the timing belt, and the lever 31 is moved by the spring 32. Therefore, it is rotated in the direction of arrow _F2 , that is, in the counterclockwise direction. As a result, the other end of the lever 31 comes into contact with the movable contact 29 of the belt switch 27, and the spring 3
A force of 2 is applied to the contact 29 to open the belt switch 27, and the engine is automatically stopped as described above.

10 and 11 show another embodiment of a mechanism for detecting breakage of the timing belt 12 and automatically stopping the engine. This embodiment electrically detects breakage of the timing belt 12, and a photo sensor 3 is installed on one side of the belt.
No. 3 light projecting section 33a is disposed, and a light receiving section 33b is disposed on the other side. Photo sensor 33 is connected to amplifier 34 . Amplifier 34 is connected to belt switch 27, such as a relay. The other structure is the same as that of the previous embodiment.

In normal conditions, the timing belt 12 passes between the light projecting section 33a and the light receiving section 33b, so the light beam L from the light projecting section 33a is blocked by the belt and does not reach the light receiving section 33b. Therefore, the photo sensor 33 does not input an electrical signal to the amplifier 34, and the belt switch 27 is in the closed position as described above. When one of the two timing belts 12 breaks, the light beam L from the light projecting section 33a enters the light receiving section 33b, and the photo sensor 33 passes through the amplifier 34.
The amplifier 34 amplifies this electrical signal and moves the belt switch 27 to the open position. As a result, the fuel supply to the engine is cut off and the engine is stopped.

In this embodiment, the photo sensor 33 may be used in combination with each timing belt 12;
One photo sensor that emits a spread beam of light can be placed across two timing belts 12, and in this case there is an advantage that costs can be reduced.

In a modification of the other embodiment shown in FIG. 12, a proximity sensor 35 is disposed near the timing belt 12 instead of the photo sensor.
The proximity sensor 35 is of a type that emits high frequency or ultrasonic waves and detects belt breakage based on the presence or absence of reflected waves from the timing belt 12. Also in this modification, two proximity sensors 3
5 may be combined with each of the timing belts 12, or one proximity sensor 35 may be provided so as to straddle the two timing belts 12.

As described above, in the device of the present invention, the timing belt 12 is arranged in two parallel rows, and one of the two rows of timing belts is cut by using the lever 3.
1. In addition to detecting with the photo sensor 33 or proximity sensor 35, when the belt is cut, the belt switch 2
7 and a fuel injection pump 9 via a solenoid valve 21
The system automatically stops the engine by closing the fuel passage 20 inside the engine and cutting off the fuel supply to the engine, which prevents damage to the engine and lets you know when it is time to replace the timing belt. be. Also, timing belt 12
By manufacturing each of the gears 3, 8, and 11 using the characteristic method described above, the timing belt 12
It also has the effect of being able to provide the same durability as a conventional toothed timing belt in the same space.

Therefore, according to the present invention, by taking advantage of the advantages of toothed timing belts such as low noise, light weight, and no need for lubrication,
In addition, the timing belt type timing transmission mechanism can be particularly adapted to industrial diesel engines by compensating for the disadvantage of poor durability.

Of course, the present invention can be applied not only to industrial engines but also to all kinds of diesel engines and gasoline engines.

[Brief explanation of the drawing]

Figure 1 is a front view of a diesel engine showing an embodiment of the present invention, Figure 2 is a sectional view of the main parts of Figure 1, Figure 3 is a sectional view taken along the - line in Figure 1, and Figure 4. 5 is an enlarged sectional view of the assembled portion of the crankshaft gear and the crankshaft, FIG. 5 is a sectional view taken along the - line in FIG. 4, and FIGS. 6 a and b are perspective explanatory views showing the manufacturing process of the crankshaft gear. , FIGS. 7a and 7b are perspective explanatory diagrams showing the manufacturing process of the toothed timing belt, FIGS. 8a, b, and c are electric circuit diagrams showing the emergency automatic stop circuit in different operating states, and FIGS. 9a and 9b are b is a schematic explanatory diagram showing the timing belt breakage detection mechanism in different operating states, FIG. 10 is an electric circuit diagram showing another embodiment of the present invention, FIG. 11 is a schematic perspective view showing the photo sensor of FIG. 10, FIG. 12 is a schematic perspective view of a proximity sensor showing a modification of the other embodiment described above. 1... Diesel engine, 2... Crankshaft, 3... Crankshaft gear, 8... Camshaft gear,
DESCRIPTION OF SYMBOLS 11...Fuel injection pump gear, 12...Toothed timing belt, 20...Fuel passage, 21...Solenoid valve, 26...Engine key switch, 27
...Belt switch, 31...Lever, 32...
Spring, 33...Photo sensor, 34...Amplifier, 35...Proximity sensor.

Claims (1)

[Scope of utility model registration request] In a timing transmission mechanism that transmits the rotation of an engine crankshaft to a driven shaft using a toothed timing belt, the timing belt is divided into two substantially equal rows of belts that are wound around the same crankshaft and the driven shaft. and a detection means for detecting breakage of the two rows of timing belts, and a belt switch that is operated when the detection means detects breakage of either one of the two rows of timing belts. A timing belt breakage detection device featuring: