JPS6143000Y2 - - Google Patents

Description

[Detailed explanation of the idea] This proposal relates to a tensioner for toothed belts.

Generally, it is necessary to apply appropriate tension to a toothed belt to prevent skipped stitches. For example, when a toothed belt is used to drive an engine's camshaft, the belt tension is adjusted appropriately using a tensioner because of the high ambient temperature and large thermal expansion, and the high engine speed that tends to cause vibrations. Must be kept within range. For this reason, conventionally,
As shown in FIG. 1, a support plate 2 supporting a pulley 1 is pivoted to a fixed member by a pin 3, a spring 4 is tensioned, a bolt 5 is loosened, and the pulley 1 is moved to a toothed belt by the spring 4 or by hand. After adjustment is made so that an appropriate initial tension is applied to the belt 6 by applying pressure to the belt 6, the support plate 2 is fixed by tightening the bolt 5. In general, the initial tension is not readjusted.

However, when the support plate 2 is fixed as described above, there is a drawback that the initial tension decreases due to elongation of the belt 6 during use, resulting in skipped stitches. Additionally, there is usually a difference in linear expansion coefficient between the glass fiber that is often used as the tensile member of the toothed belt 6 and the structure to which the toothed belt is assembled, so the initial tension may become too large or too small due to changes in ambient temperature. Sometimes. Particularly in the case of engine applications, the temperature reaches around 100 degrees Celsius, and toothed belts, which have a smaller coefficient of linear expansion than engine constituent materials such as iron and aluminum alloys, have the problem of being stretched and increasing tension.

In order to solve these problems, an improved tensioner shown in FIG. 2 has also been proposed. That is, a support plate 7 supporting the pulley 1 is freely pivoted by a pin 8, and a plunger 10 driven by spring pressure that slides inside a cylinder 9 pressurizes the support plate 7 and fills the cylinder 9. The fluid is allowed to enter and exit the low pressure fluid chamber 13 through the two reverse check valves 11 and 12, and when the belt tension increases beyond the allowable upper limit, the plunger 10 is allowed to retreat to reduce the belt tension. Therefore, the check valve 11 is a spring-loaded check valve. Further, the inside of the fluid chamber 13 is maintained at a low pressure corresponding to the normal value of the belt tension by the plunger 14 and the spring 15. With the above structure, the belt tension is maintained between the normal value and the permissible upper limit.

However, in the above-mentioned improved tensioner, there is a possibility that the belt tension decreases and skipped stitches occur at the moment when the plunger 10 rapidly retreats in response to a sudden change in the belt tension. Particularly in engines, the camshaft torque and the load on the injection pump alternately fluctuate, and the latter load fluctuations are particularly large.
When such alternating load fluctuations occur, valve 11 opens when the load exceeds the load corresponding to the allowable upper limit of belt tension, and valve 12 opens when the belt tension falls below the normal value. Vibration occurs. Although high-speed vibrations are difficult to occur due to the inertia of the tensioner, the low-speed vibrations described above can occur.Moreover, since the valves 11 and 12 have low fluid flow resistance, if valve 11 opens rapidly during low-speed vibrations, the belt tension will increase. There is a risk that the value may drop momentarily, causing skipped stitches.

The purpose of the present invention is to provide a tensioner for toothed belts that prevents skipped stitches when low-speed vibration occurs by imparting throttling characteristics to the spring-loaded check valve 11 in the improved tensioner to prevent sudden opening operations. There are suggestions.

FIG. 3 shows a sectional view of a main part of an embodiment of the present invention, in which a throttle passage 16 is provided at the inlet of the spring-loaded check valve 11. At this time, since the opening speed of the valve 10 is suppressed by the throttle passage 16, the belt tension does not decrease rapidly, and skipped stitches are therefore prevented.

As mentioned above, this proposal reduces the operating speed of the tensioner in the direction of belt tension reduction by providing an extremely simple means of providing a throttle passage, thereby preventing stitch skipping when the belt load vibrates at low speed. It has a moisturizing effect.

[Brief explanation of the drawing]

FIG. 1 is an elevational view of a conventional example, FIG. 2 is an elevational view showing a part of an improved tensioner in cross section, and FIG. 3 is a sectional view of a main part of an embodiment of the present invention. 1... Pulley, 6... Toothed belt, 9... Cylinder, 10... Plunger, 11... Spring loaded check valve, 12... Check valve, 13... Low pressure fluid chamber,
16...Aperture passage.

Claims (1)

[Scope of utility model registration request] A cylinder chamber on the spring pressure side of a cylinder equipped with a spring-pressurized plunger that applies tension to the toothed belt via a pulley in contact with the toothed belt is filled with fluid, and the cylinder chamber is used to apply tension to the belt by the spring pressure. connected to a low-pressure fluid chamber pressurized to maintain normal values through two check valves oriented in opposite directions,
The check valve that allows fluid to flow from the cylinder chamber to the low-pressure fluid chamber is a spring-loaded check valve that opens when the tension reaches an allowable upper limit, and the inflow port of the spring negative-pressure check valve. A tensioner for toothed belts with a constriction passage.