JP2536250B2 - Variable valve timing mechanism - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing varying mechanism that varies the operation timing of an intake valve and an exhaust valve during engine operation.

[Prior Art] Conventionally, as a valve timing variable mechanism of this type, for example, the technology disclosed in JP-A-61-268810 is known.

That is, as shown in FIG. 3, in the technique of the above publication, a camshaft rotatably supported by the cylinder head 41.
A timing pulley assembly 43, which is drivingly connected to the engine, is provided at one end of 42. A hollow shaft 44 is integrally rotatably provided on the cam shaft 42, and a ring gear 45 is interposed between the hollow shaft 44 and the timing pulley assembly 43 to connect the both 43, 44. That is, at least one of the teeth 45a and 45b provided on the inner and outer circumferences of the ring gear 45 is a helical tooth, and is rotatable relative to the cam shaft 42 by moving in the axial direction. The teeth 45a and 45b on the inner and outer circumferences of the ring gear 45 mesh with the outer teeth 44a of the hollow shaft 44 and the inner teeth 43a of the timing pulley assembly 43, respectively.

Inside the timing pulley assembly 43, a piston 46 is provided in a space in the axial direction one end side of the ring gear 45. Control oil acts on one end of the piston 46 through the oil passage 47 of the camshaft 42 and the hollow bolt 48, and the control oil pressure acts on the ring gear 45 through the piston 46. In addition, the ring gear 45 should face the control oil pressure.
A balancing spring 49 is provided in the other end side space.

Then, the control oil adjusted to a predetermined pressure by the control valve 50 is added to one end side of the ring gear 45 via the piston 46, and the ring gear 45 is moved in the axial direction against the biasing force of the spring 49, The camshaft 42 is twisted so that the camshaft 42 and the timing pulley assembly
The relative position in the rotation direction with respect to 43 can be changed. As a result, the operation timing of the intake valve and the exhaust valve (not shown) can be changed. The above is the basic configuration of the variable valve timing mechanism.

In addition to this, a seal 51 for sealing the control oil leaking from the inside of the timing pulley assembly 43 is provided between one end of the timing pulley assembly 43 and a part of the cylinder head 41 (cam cover). There is. Similarly, between one end of the timing pulley assembly 43 and the cam shaft 42, an oil recovery chamber 52 for recovering the control oil leaking from the inside of the timing pulley assembly 43 is provided. Further, an oil return hole 53 for returning the control oil recovered in the oil recovery chamber 52 to an oil pan (not shown) is formed in a part of the cylinder head 41 below the camshaft 42.

[Problem to be Solved by the Invention] Therefore, in the above-mentioned conventional technique, when the ring gear 45 is released from the control hydraulic pressure and returned by the urging force of the spring 49, the space volume in which the spring 49 is located tends to increase. However, the cylinder head 41 is provided with only the oil return hole 53, and the oil return hole 53 may be blocked with oil, which deteriorates the return responsiveness of the ring gear 45 and causes the variable valve timing mechanism. The operation response was not good.

In addition, if the amount of control oil added to the piston 46 increases or if there is an intermittent fluctuation in the supply of control oil, the return from the oil return hole 53 will be poor and the inside of the oil recovery chamber 52 will be clean. It causes pressure or pulsation of hydraulic pressure. Therefore, positive pressure may be applied to the seal 51 in the vicinity of the oil recovery chamber 52, causing oil leakage.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to make variable valve timing capable of ensuring smooth operation response and suppressing oil leakage from a seal even with excessive control oil. To provide a mechanism.

[Means for Solving the Problems] In order to achieve the above object, in the present invention,
A valve driving cam shaft rotatably supported by the cylinder head and the bearing cap, a timing pulley assembly provided at one end of the cam shaft and drivingly connected to the engine, and teeth provided on the inner and outer circumferences. At least one of the teeth is a helical tooth and is interposed between the cam shaft and the timing pulley assembly to connect the two, and at the same time, the ring gear rotatable relative to the cam shaft by axial movement and the timing pulley assembly. The control hydraulic pressure applied against the biasing force of the spring is provided with a balancing spring provided on the other end side of the ring gear facing the control hydraulic pressure applied to the one end side in the axial direction of the ring gear. Twists the camshaft by rotating the ring gear while moving it axially. In the variable valve timing mechanism to be applied, a seal provided between the timing pulley assembly and the cylinder head and bearing cap to seal the control oil leaking from the inside of the timing pulley assembly, the camshaft, the cylinder head and the bearing cap. And a seal, and an oil recovery chamber that recovers control oil leaking from the inside of the timing pulley assembly,
An oil return hole provided in the cylinder head for returning the control oil recovered in the oil recovery chamber to the supply side, and an oil recovery hole, which is provided separately from the oil recovery hole, above the oil recovery hole. And an atmosphere communication hole for communicating the chamber with the atmosphere.

[Operation] According to the above configuration, when the camshaft is rotationally driven by the timing pulley assembly driven by the engine, the control oil pressure is applied to one end side in the axial direction of the ring gear, so that the ring gear is urged by the spring. It is rotated while moving in the axial direction. by this,
The camshaft is twisted to change the relative position of the camshaft and the timing pulley assembly in the rotational direction. As a result, the operation timings of the intake valve and the exhaust valve (not shown) are changed.

At this time, the control oil leaking from the inside of the timing pulley assembly is prevented from leaking to the outside by the seal, and is recovered in the oil recovery chamber, and a part of it is returned to the supply side from the oil return hole. Further, since the oil recovery chamber communicates with the atmosphere through an atmosphere communication hole that is provided above the oil recovery hole, which is separate from the oil recovery hole, excess control oil pressure applied to the oil recovery chamber is communicated through the atmosphere communication hole. There is no relief and no excessive positive pressure is applied to the seal.

On the other hand, when the ring gear is released from the pressurization of the control oil, the ring gear returns to the position before pressurization by the urging force of the spring. At this time, since the atmospheric pressure is introduced into the timing pulley assembly through the atmosphere communication hole and the oil recovery chamber, the ring gear can be smoothly returned.

[Embodiment] An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view for explaining the valve timing varying mechanism of this embodiment. A camshaft 1 for driving an intake valve and an exhaust valve (not shown) has a cam journal 2 rotatably supported between a bearing portion 4 of a cylinder head 3 and a bearing cap 5. The bearing cap 5 has a block shape and is attached to the upper portion of the bearing 4. A perspective view of the bearing cap 5 is shown in FIG. or,
A timing pulley assembly 6 is provided at one end of the camshaft 1.

The cylinder head 3 and the cam shaft 1 have journal oil passages 7 and 8 for supplying lubricating oil to the cam journal 2.
Are formed respectively. Then, during operation of the engine, the lubricating oil sucked up from the oil pan 10 by the oil pump 9 is sent to the journal oil passages 7 and 8 via the oil filter 11 and supplied to the cam journal 2.

The timing pulley assembly 6 has a plurality of outer teeth 12 on its outer circumference.
And a pulley body 14 having a housing recess 13 on one side
And a cap 16 fixed with a bolt 15 at the tip of the camshaft 1 so as to cover the accommodation recess 13 of the pulley body 14. Also, the open end of the pulley body 14 and the cap 16
A well-known viscous joint (viscous coupling) 17 for cushioning is provided between the outer periphery and the outer periphery of the. The viscous coupling 17 includes an outer plate 18 press-fitted and fixed to the pulley body 14 and an inner plate 19 incorporated in the outer plate 18 and formed on the cap 16, and not shown between the two 18 and 19. A high-viscosity viscous fluid is enclosed. Further, this viscous fluid is a seal 20A provided inside the inner plate 19 and outside the outer plate 18,
It is sealed by 20B.

A ring gear 21 is interposed between the timing pulley assembly 6 and the camshaft 1 to connect the both 6, 1. That is, the pulley body 14 sealed by the cap 16
A ring gear 21 is housed in the housing recess 13 of. This ring gear 21 has a plurality of teeth 21 provided on its inner and outer circumferences.
Both a and 21b have helical teeth, and can move relative to the camshaft 1 by moving in the axial direction. The teeth 21a and 21b on the inner and outer circumferences of the ring gear 21 are the pulley body 14
And the inner teeth 14a of the cap 16 and the inner teeth 16a of the cap 16, respectively. The timing pulley assembly 6 is drivingly connected to the engine via a timing belt (not shown) that is attached to the outer teeth 12 of the pulley body 14.

Therefore, when the drive is transmitted from the engine to the timing pulley assembly 6, the pulley body 14 and the cap 16 connected by the ring gear 21 are integrally rotated, and the camshaft 1 is rotationally driven.

In the housing recess 13 of the pulley body 14, one end side in the axial direction of the ring gear 21 is acted on by control oil sent through a control oil passage 22 formed in the cylinder head 3 and a control oil passage 23 formed in the camshaft 1. It is the pressure chamber 24.
Similarly, in the accommodation recess 13, the other end of the ring gear 21 is a spring chamber 26 for accommodating a balancing spring 25 facing the control oil pressure.

And the oil switching valve during engine operation
By operating 27, a part of the lubricating oil sent from the oil filter 11 to the journal oil passage 7 is guided as control oil through the control oil passages 22 and 23 to the pressurizing chamber 24 of the accommodating recess 13 and the ring gear 21 It is added to one end. By this control hydraulic pressure, the ring gear 21 is moved in the axial direction against the urging force of the spring 25, and the camshaft 1 is twisted. As a result, the relative positions of the camshaft 1 and the timing pulley assembly 6 in the rotational direction are changed, and the operation timings of the intake valve and the exhaust valve (not shown) are changed. Further, when the camshaft 1 is twisted, backlash is generated in the ring gear 21, but the backlash is buffered by the action of the viscous coupling 17 and the generation of abnormal noise is suppressed.

Also, the timing pulley assembly 6 and the cylinder head 3
A rubber seal 28 for sealing the control oil leaking from the inside of the timing pulley assembly 6 is provided between the bearing cap 5 and the bearing cap 5. That is, the spring chamber 26
A flange 14b extending in the axial direction is formed at one end of the corresponding pulley body 14, and the seal holding portion 3a, which projects outward, is provided on the Linda head 3 and the bearing cap 5 so as to face the flange 14b. 5a is formed. The seal 28 is held between the flange 14b and the seal holding portions 3a, 5a.

An oil recovery chamber 29 for recovering control oil leaking from the inside of the timing pulley assembly 6 is provided between the camshaft 1, the cylinder head 3, the bearing cap 5, and the seal 28. That is, the annular space surrounded by the seal holding portions 3a, 5a and the seal 28 is the oil recovery chamber 29. In this embodiment, a return oil passage for guiding the control oil to the oil recovery chamber 29 is provided in a part of the pulley body 14 and the camshaft 1.
30 are formed. Therefore, the control oil leaking from the pressurizing chamber 24 of the housing recess 13 to the spring chamber 26 is guided to the oil recovery chamber 29 through the return oil passage 30.

Further, at the lower position of the camshaft 1, only one oil return hole 31 for returning the control oil recovered in the oil recovery chamber 29 to the oil pan 10 is formed in a part of the cylinder head 3. ing.

In addition, in this embodiment, as shown in FIGS. 1 and 2, a part of the bearing cap 5 at a position above the camshaft 1 is provided with one atmosphere communication hole for communicating the oil recovery chamber 29 with the atmosphere.
32 is provided separately from the oil return hole 31. The atmosphere communication hole 32 is opened to the inside of the cylinder head 3 and also functions as a hole for returning the control oil recovered in the oil recovery chamber 29 to the oil pan 10.

The upper side of the cylinder head 3 is covered with a head cover 33. The joint between the head cover 33 and the bearing gap 5 is sealed by a gasket 34.

Next, the operation of the valve timing variable mechanism configured as described above will be described.

Now, when the camshaft 1 is rotationally driven by the timing pulley assembly 6 driven by the engine,
When the oil switching valve 27 is opened, the control oil is introduced into the pressurizing chamber 24. As a result, a control hydraulic pressure is applied to one end side of the ring gear 21, and the ring gear 21 is rotated against the biasing force of the spring 25 while moving in the axial direction. As a result, the camshaft 1 is twisted, the relative positions of the camshaft 1 and the timing pulley assembly 6 in the rotational direction are changed, and the operation timings of the intake valve and the exhaust valve are changed.

At this time, the control oil leaking from the inside of the timing pulley assembly 6 through the return oil passage 30 is prevented from leaking to the outside by the seal 28, and is collected in the oil collecting chamber 29. In addition, a part of the control oil in the oil recovery chamber 29 is
Returned to oil pan 10. Moreover, in this embodiment, since the atmosphere communication hole 32 is provided above the oil return hole 31 in addition to the oil return hole 31 and communicates with the atmosphere, the control oil pressure increases and the oil recovery chamber 29 enters the oil recovery chamber 29. Even if excessive control oil pressure is applied, the excess control oil can be released through the atmosphere communication hole 32. Further, even if the control oil supply fluctuates intermittently, the pulsation can be alleviated by the atmosphere acting through the atmosphere communication hole 32.

As a result, the positive pressure more than necessary is not applied to the seal 28, and the oil leakage from the seal 28 due to the positive pressure can be suppressed. That is, the sealability of the seal 28 can be sufficiently ensured.

On the other hand, when the oil switch valve 27 is closed, the ring gear 21 is released from the pressurization of the control oil. As a result, the ring gear 21 tries to return to the position before pressurization by the biasing force of the spring 25. At this time, since the atmospheric pressure is introduced into the timing pulley assembly 6 through the atmosphere communication hole 32, the oil recovery chamber 29, etc., the ring gear 21 is smoothly returned. Further, at that time, even when the oil return hole 31 is blocked by the control oil, the atmosphere communication hole 32 provided above the oil return hole 31 causes a large internal space in the timing pulley assembly 6. Atmospheric pressure is reliably introduced.

As a result, the return response of the ring gear 21 can be improved, and the operation response of the variable valve timing mechanism can be improved.

However, in order to improve the sealability and the operation response as the variable valve timing mechanism as described above,
For example, instead of providing the atmosphere communication hole 32, it is conceivable to increase the inner diameter of the conventional oil return hole 31. However, in this case, since the oil return hole 31 is located on the lower side of the camshaft 1, oil and air act at the same time, resulting in poor efficiency. It is also possible to provide a plurality of oil return holes 31, but when making a plurality of holes in the cylinder head 3 at the same time, it is difficult to secure a hole pitch for simultaneous processing by a multi-axis drilling machine or the like. Met.

Therefore, forming the atmosphere communication hole 32 in the bearing cap 5 at a position above the camshaft 1 as in this embodiment can most effectively suppress the pressure increase in the oil recovery chamber 29. .

The present invention is not limited to the above-described embodiments, and a part of the configuration can be appropriately modified and carried out as follows without departing from the spirit of the invention.

(1) In the above-mentioned embodiment, one atmosphere communication hole 32 is formed in the bearing cap 5, but the number may be increased appropriately. Further, when a plurality of atmosphere communication holes are formed, it is not necessary to limit the position to the upper position of the camshaft, and it is possible to form the holes at both lateral positions of the camshaft as long as they are above the oil return hole. You can also do it.

(2) In the above embodiment, both the inner and outer teeth of the ring gear 21
21a and 21b are helical teeth, but the inner and outer teeth 21a and 21b
Only one of these may be used as the helical tooth.

As described above in detail, according to the present invention, the seal for sealing the control oil leaking from the inside of the timing pulley assembly is provided between the timing pulley assembly and the cylinder head and the bearing cap. , Between the camshaft and cylinder head and between the bearing cap and seal,
An oil recovery chamber is provided to collect the control oil that leaks from the timing pulley assembly, and an oil return hole is provided in the cylinder head to return the control oil recovered in the oil recovery chamber to the supply side. Separately from the oil return hole, an atmosphere communication hole for communicating the oil recovery chamber with the atmosphere is provided above the oil return hole, so that even if there is a possibility that the oil return hole is blocked by the control oil, By communicating the atmosphere through the communication hole, a smooth operation response can be secured, and an excellent effect that oil leakage from the seal to the outside can be suppressed even with an excessive control hydraulic pressure is exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a valve timing variable mechanism in an embodiment embodying the present invention, and FIG. 2 is a perspective view showing an atmosphere communication hole formed in a bearing cap thereof. FIG. 3 is a sectional view for explaining a valve timing varying mechanism in the conventional example. In the figure, 1 is a camshaft, 3 is a cylinder head, 5 is a bearing cap, 6 is a timing pulley assembly, 21
Is a ring gear, 21a and 21b are teeth, 25 is a spring, 28 is a seal, 29 is an oil recovery chamber, 31 is an oil return hole, and 32 is an atmosphere communication hole.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor, Yasutomi, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Shuji Morita 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Nobuyuki Murakami 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (56) References 61-268810 (JP, A) JP-A-62-45912 (JP, A)

Claims (1)

(57) [Claims] 1. A camshaft for driving a valve, which is rotatably supported by a cylinder head and a bearing cap, a timing pulley assembly provided at one end of the camshaft and drivingly connected to an engine, and inner and outer circumferences. At least one of the teeth provided is a helical tooth, and is interposed between the cam shaft and the timing pulley assembly to connect them,
A ring gear that is rotatable relative to the cam shaft by movement in the axial direction, and a control hydraulic pressure applied to one end side in the axial direction of the ring gear inside the timing pulley assembly,
A balance spring provided on the other end side of the ring gear; and the camshaft by rotating the ring gear while moving it axially by a control hydraulic pressure applied against the biasing force of the spring. A variable valve timing mechanism for imparting a twist to a seal, which is provided between the timing pulley assembly and the cylinder head and the bearing cap and seals control oil leaking from the inside of the timing pulley assembly. An oil recovery chamber that is provided between the camshaft, the cylinder head, the bearing cap, and the seal, and collects control oil leaking from the inside of the timing pulley assembly; and an oil recovery chamber that recovers the control oil. Oil return hole provided in the cylinder head for returning control oil to the supply side A valve timing variable mechanism, which is provided separately from the oil return hole and above the oil return hole, and an atmosphere communication hole for communicating the oil recovery chamber with the atmosphere.