JP2021038791A - Hydraulic automatic tensioner for internal combustion engine - Google Patents

Abstract

To suppress flapping of a timing chain by quickening rise of an automatic tensioner in starting an engine in an oil release state, in the hydraulic automatic tensioner for a timing chain.SOLUTION: An air bleeding passage 26 is formed on an oil release passage 24 of an automatic tensioner 14, and a valve device 27 through which air is passed though an oil is not passed, is disposed on the air bleeding passage 26. The valve device 27 includes a ball-type valve element 29 held by a tension spring 30. As a dynamic pressure of the air is small, the air can be discharged without extending and deforming the tension spring 30. Accordingly, inflow of the oil can be enhanced. When the oil flows in, the ball-type valve element 29 is moved in a closing direction by a dynamic pressure of the oil. Thus rise of a function of the automatic tensioner 14 can be enhanced.SELECTED DRAWING: Figure 2

Description

The present invention relates to a hydraulic auto tensioner used in an internal combustion engine, for example, to automatically adjust the tension of a timing chain.

In an internal combustion engine, a hydraulic auto tensioner is used to apply an appropriate tension to a timing chain that drives a camshaft. That is, the guide body that guides the slack side of the timing chain is rotatably configured, and the portion of the guide body that is distant from the rotation fulcrum is supported by the plunger of the auto tensioner. The plunger is supported by a spring and oil so that the force is constant.

Specifically, for example, as disclosed in Patent Document 1, a pressure chamber in which a plunger urged in the forward direction by a spring is slidably arranged, an oil supply passage for supplying oil to the pressure chamber, and the like. It has an oil escape passage that allows oil to escape when the pressure in the pressure chamber exceeds the set value, and while blocking the backflow of oil from the pressure chamber to the oil supply passage with a check valve, a relief provided in the oil escape passage. The valve sets the pressure in the hydraulic chamber so that it does not exceed the set value.

That is, when the pressure in the hydraulic chamber exceeds the set value, the oil passes through the relief valve and is discharged from the oil relief passage, so that the pressure in the hydraulic chamber is kept constant and the bearing force (pushing pressure) of the plunger is maintained. Is kept constant.

By the way, in the operating state of the engine, the outflow of oil from the pressure chamber is blocked by the check valve, but after a certain amount of time has passed since the engine was stopped, a slight gap between the plunger and the pressure chamber The oil gradually flows out from the slight gap of the check valve, and the oil in the pressure chamber runs out or decreases. Therefore, until the oil is supplied from the oil pump at the next start. During that time, the auto tensioner did not work and the timing chain sometimes fluttered.

Furthermore, since air is accumulated in the pressure chamber and the oil escape passage, the air becomes a resistance and the oil supply is suppressed. Therefore, after starting the engine, the pressure chamber and the oil escape passage It took some time for the oil to fill up, and as a result, the timing chain fluttered.

Regarding this point, Patent Document 1 provides an air tank having a large capacity in the oil escape passage to accelerate the inflow of oil into the pressure chamber.

Japanese Unexamined Patent Publication No. 2014-159891

It can be said that Patent Document 1 attempts to accelerate the inflow of oil into the pressure chamber by utilizing the compression of air, but when the air is pressed by the oil and compressed, it is large with respect to the flow of oil. Because of the resistance, it is doubtful whether the time from starting the engine to filling the pressure chamber with oil can be significantly reduced.

Further, in Patent Document 1, the plunger can be pushed by the oil only after the oil fills the oil escape passage and the air tank, but there is a problem that it takes a long time for the oil to flow in if there is an air tank. , It is understood that it is doubtful whether the time when the function of the auto tensioner is exhibited can be shortened.

The present invention has been made against the background of such a situation, and it is an object of the present invention to significantly shorten the start-up time of the auto tensioner even when the start is performed in a state where oil is drained from the inside of the auto tensioner. It is a thing.

The auto tensioner of the present invention is
"A pressure chamber in which a plunger urged in the forward direction by a spring is slidably arranged, and
An oil supply passage for supplying oil to the pressure chamber and
It has an oil relief passage that allows oil to escape when the pressure in the pressure chamber exceeds the set value.
The backflow of oil from the pressure chamber to the oil supply passage is blocked by a check valve, and the set value is defined by a relief valve provided in the oil relief passage. "
In the basic configuration
"The air bleeding passage is connected to the oil bleeding passage, and the air bleeding passage is provided with a valve device that allows the passage of air and blocks the passage of oil."
It has the feature.

The valve device in this case is divided into a powered one and a powered one. Examples of the power valve device include those that open and close the valve body using an electromagnetic solenoid or an electric motor. In this case, the valve device is interlocked with the ignition switch, and the valve device may be opened for a preset time after the ignition switch is turned on and the engine is started.

As a non-powered valve device, a kind of relief valve that does not close by the dynamic pressure of air but closes by the dynamic pressure of oil can be used. Alternatively, it is also possible to use a bimetal whose shape changes depending on the temperature of the oil and to close the air bleeding passage by utilizing the deformation of the bimetal.

In the present invention, even if the oil has escaped from the pressure chamber or the oil escape passage after the engine is stopped, the air can be discharged (pushed) out of the air vent passage by the inflow of the oil at the next start. It is possible to prevent the air from becoming a resistance to the inflow of oil, and to quickly fill the pressure chamber and the oil relief passage with oil. Therefore, it is possible to speed up the start-up of the function of the auto tensioner and prevent or remarkably suppress the fluttering of the timing chain.

In particular, it is preferable to use a valve device that closes by the dynamic pressure of oil as the valve device because the structure can be simplified.

It is a front view of the internal combustion engine which concerns on embodiment. FIG. 1 is a sectional view taken along line II-II of FIG. 1, showing the valve device of the first embodiment. (A) is a cross-sectional view of a state in which the relief valve is closed in the operating state, and (B) is a cross-sectional view of a state in which the relief valve is open in the operating state. It is a figure which shows the other embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the words front and back, left and right are used to specify the direction, but the side where the timing chain and crank pulley are arranged is the front, and the side where the mission case is arranged is the back.

(1). Overview Fig. 1 is a front view (front view) of the engine body constituting the internal combustion engine. The engine body includes a cylinder block 1 in which cylinder bores are arranged in the direction of the crank axis and an upper surface of the cylinder block 1. A cylinder head 2 fixed to the cylinder head 2 and an oil pan 3 fixed to the lower surface of the cylinder block 1 are provided, and a head cover 4 is fixed to the upper surface of the cylinder head 2. The front surfaces of the cylinder block 1 and the cylinder head 2 are covered with a front cover (not shown).

A crankshaft 6 is rotatably held on the lower surface of the cylinder block 1 via a crank cap 5. Further, a recess is formed on the front surface of the cylinder block 1, and the timing chain 7 is arranged in this recess. The parallel diagonal lines displayed in FIG. 1 indicate the front surface (flat surface) of the wall of the cylinder block 1, not the cross section.

The timing chain 7 is wound around a main sprocket 8 provided on the crankshaft 6 and a driven sprocket 9 attached to an intake valve camshaft and an exhaust valve camshaft via a VVT device (not shown). , Each sprocket 8 and 9 rotates clockwise in front view. Therefore, in the state of FIG. 1, the right side portion of the timing chain 7 is on the tension side, and the left side portion is on the slack side.

Since two driven sprockets 9 are arranged on the left and right, the timing chain 7 is stretched in an inverted triangular posture when viewed from the front. Therefore, in order to ensure smooth circulation while narrowing the arrangement space of the timing chain 7 as much as possible, a fixed guide body 10 and a rotary guide in which the contact surface with the timing chain is gently curved are formed in the recess of the cylinder block 1. The body 11 and the body 11 are arranged. The fixed guide body 10 is arranged on the tension side (right side) of the timing chain 7 and is fixed to the cylinder block 1 by the upper and lower bolts 12.

On the other hand, the rotary guide body 11 is arranged on the loose side (left side) of the timing chain 7, and is connected to the cylinder block 1 by a pivot bolt 13 so as to rotate with the upper end portion thereof as a fulcrum. Further, the rotary guide body 11 is elastically supported at a portion of the cylinder block 1 which is separated from the rotation fulcrum to some extent, and an appropriate tension is applied to the timing chain 7. An auto tensioner 14 is arranged.

(2). Structure of the auto tensioner As shown in FIG. 2, the auto tensioner 14 includes a housing 15 fixed to the cylinder block 1, and the pressure opened in the housing 15 toward the rotary guide body 11. A chamber 16 is formed, and a plunger 17 that supports the rotary guide body 11 is slidably attached to the pressure chamber 16 via a sleeve 18 so as not to come off. The plunger 17 has a recess 19 that opens toward the bottom surface of the pressure chamber 16, and a spring 20 that urges the plunger 17 in the forward direction is arranged in the recess 19.

An oil supply passage 22 for communicating the oil gallery 21 formed in the cylinder block 1 and the pressure chamber 16 is formed in the housing 15, and a reverse flow for preventing backflow of oil is prevented at the end of the oil supply passage 22. A check valve 23 is attached. The branch passage 21a branches from the oil gallery (main gallery) 21 of the cylinder block 1, and the branch passage 21a and the oil supply passage 22 communicate with each other.

Further, the housing 15 is formed with an oil relief passage 24 for releasing oil when the pressure in the pressure chamber 16 becomes excessive, and a relief valve 25 for setting a relief pressure is provided at the end of the oil relief passage 24. It is installed. The relief valve 25 may be opened in the recess of the cylinder block 1 or may be connected to the return passage formed in the cylinder block 1.

Then, an air bleeding passage 26 opened in a recess of the cylinder block 1 is formed in a portion of the oil escape passage 24 on the upstream side of the relief valve 25, and the air bleeding passage 26 of the first embodiment is used for removing air from the first embodiment. The valve device 27 is attached. The air exhaust valve device 27 is a pressure response type, and has a stepped tubular casing 28 fitted and fitted into the air bleeding passage 26 from the outside, a ball type valve body 29 built in the casing 28, and a ball type valve body 29. It has a tension spring 30 for holding.

The end plate 31 is fixed to the opening exposed to the outside of the housing 15 in the casing 28, and the end plate 31 has an air discharge hole 32. Further, one end of the tension spring 30 is fixed to the front end of the casing 28, and the other end is fixed to the ball type valve body 29.

Then, the spring force of the tension spring 30 is not stretched or deformed at all or almost even if the dynamic pressure of the air acts on the ball type valve body 29, but is stretched and deformed when the dynamic pressure of the oil acts on the ball type valve body 29. The strength is set so that the ball-type valve body 29 comes into contact with the end plate 31.

When the engine is stopped for a long time and the oil is drained from the pressure chamber 16 and then restarted, the oil pumped by the oil pump flows into the pressure chamber 16 and the oil escape passage 24. Since the air accumulated inside is discharged from the air bleeding passage 26, the pressure chamber 16 and the oil escape passage 24 are quickly filled with oil by preventing the air from becoming a resistance to the inflow of oil.

The mass (density) of oil is much larger than that of air, and the dynamic pressure acting on the ball-type valve body 29 is also much larger than that of air. Therefore, the ball-type valve body 29 is pushed by the flow of oil. The air discharge hole 32 is closed by the ball-type valve body 29. Therefore, the plunger 17 is supported by the oil at an appropriate pressure (the pressure in the pressure chamber 16 can be maintained). Therefore, it is possible to speed up the start-up of the function of the auto tensioner 14 and prevent or remarkably suppress the fluttering of the timing chain 7.

In the operating state of the engine, the pressure of the oil always acts on the ball type valve body 29, so that the air bleeding passage 26 is always closed as shown in FIGS. 3A and 3B. Therefore, the pressure regulating function of the relief valve 25 is not impaired.

When the operation of the engine is stopped, the oil may leak from the air bleeding passage 26, but since the oil flows in quickly at the next start, no particular problem occurs. If the air discharge hole 32 is provided at a position higher than the pressure chamber 16 and the oil escape passage 24 as in the embodiment, oil can be prevented or remarkably suppressed from leaking from the air discharge hole 32 when the operation of the engine is stopped. When restarting shortly after stopping, there is an advantage that the auto tensioner 14 can be started up instantly.

(3). Other Embodiments FIG. 4 shows the air exhaust valve device 27 of the other embodiment. These air exhaust valve devices 27 are of the pressure response type as in the first, and in the second embodiment shown in (A), the valve seat plate 33 in which the air discharge hole 32 is formed inside the casing 28. Is arranged, and a rotary valve body 34 made of an elastic plate such as a leaf spring is attached to the valve seat plate 33. The rotary valve body 34 may be connected by a pin and urged in the opening direction by a spring body such as a torsion spring.

In this embodiment, air is discharged from the air discharge hole 32 without closing and operating the rotary valve body 34, while when oil flows, dynamic pressure is applied to a wide surface of the rotary valve body 34. By acting, the rotary valve body 34 automatically closes and rotates to close the air discharge hole 32.

In the third embodiment shown in FIG. 4B, the needle valve 35 is used as the valve body, and the needle valve 35 is urged in the opening direction by the compression coil spring 36. The needle valve 35 is held in an open position by a stopper plate 38 having a center hole 37, and the stopper plate 38 is provided with a plurality of small-diameter flow holes 39 through which air passes.

In this embodiment, the air in the stopper plate 38 escapes to the recess of the cylinder block 1 via the flow hole 39 and the air discharge hole 32 in the end plate, while when the oil flows in, the oil mainly flows into the stopper plate. It flows into the casing 28 from the center hole 37 of the 38 and moves the needle valve 35 in the closing direction. That is, since the flow hole 39 has a small diameter, the air hardly passes through the oil due to the flow resistance, and the oil enters the center hole 37 exclusively. Therefore, the oil urges the needle valve 35 in the closing direction. Can be done.

In any of the embodiments, some oil may leak from the air bleeding passage 26 toward the recess of the cylinder block 1, but the oil leaked into the recess of the cylinder block 1 returns to the oil pan, so that the air bleeding passage 26 There is no particular problem even if the cylinder block 1 is left open in the recess.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various ways. For example, if the valve body of the air exhaust valve device is urged by a hydraulic cylinder in the opening direction, oil is supplied to the hydraulic cylinder from the upstream side of the pressure chamber, and the pressure chamber and the oil escape passage are filled with oil. , It is also possible to configure the valve body to close.

Further, the auto tensioner of the present invention can be used not only for adjusting the tension of a timing chain but also for adjusting the tension of an alternator driving belt or a motor generator driving belt, for example.

The present invention can be embodied in a hydraulic auto tensioner for an internal combustion engine. Therefore, it can be used industrially.

1 Cylinder block 6 Crankshaft 7 Timing chain 8 Driven sprocket 9 Driven sprocket 10 Fixed guide body 11 Rotating guide body 14 Auto tensioner 15 Housing 16 Pressure chamber 17 Plunger 20 Spring 21 Oil gallery 22 Oil supply passage 23 Check valve 24 Oil relief passage 25 Relief valve 26 Air bleeding passage 27 Air bleeding valve device 28 Casing 29 Ball type valve body 30 Tension spring 32 Air discharge hole

Claims (1)

A pressure chamber in which a plunger urged in the forward direction by a spring is slidably arranged, and
An oil supply passage for supplying oil to the pressure chamber and
It has an oil relief passage that allows oil to escape when the pressure in the pressure chamber exceeds the set value.
The backflow of oil from the pressure chamber to the oil supply passage is blocked by a check valve, and the set value is defined by a relief valve provided in the oil relief passage.
An air bleeding passage is connected to the oil bleeding passage, and a valve device is provided in the air bleeding passage to allow the passage of air and prevent the passage of oil.
Hydraulic auto tensioner for internal combustion engine.

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