VALVE TIMING ADJUSTING APPARATUS

- DENSO CORPORATION

A valve timing adjusting apparatus includes a housing, a vane rotor, at least one shaft member, and at least one annular seal member. The at least one shaft member is rotatable synchronously with a driven-side shaft and the vane rotor, and is journaled within the housing. The at least one annular seal member is provided between the at least one shaft member and the housing, and the at least one seal member limits leakage of working fluid from a receiving chamber of the housing to an exterior of the housing.

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Description
CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2008-27213 filed on Feb. 7, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing adjusting apparatus for changing timing of opening and closing at least one of an intake valve and an exhaust valve of an internal combustion engine in accordance with an operational condition.

2. Description of Related Art

In a conventional vane-type valve timing adjusting apparatus, it is known that a timing pulley is synchronously rotatable with a driving-side shaft of an engine, and that the driving-side shaft drives a driven-side shaft through a chain sprocket. The valve timing adjusting apparatus opens and closes at least one of intake and exhaust valves based on a phase difference of the driven-side shaft with respect to the timing pulley and the chain sprocket.

A valve timing adjusting apparatus described in JP3567551B includes a disc-like plate having a projection surface and provided between a vane rotor and a housing. Thus, in the valve timing adjusting apparatus, the disc-like plate limits leakage of hydraulic oil between oil pressure chambers defined by multiple vanes of the vane rotor. Also, a valve timing adjusting apparatus described in JP-A-2006-77662 (corresponding to U.S. Pat. No. 7,066,122) has a vane rotor or a housing having a fully thought-out shape such that leakage of hydraulic oil between oil pressure chambers is reduced.

The leakage of hydraulic oil in the valve timing adjusting apparatuses is classified as internal leakage or external leakage. The internal leakage is leakage of hydraulic oil between the oil pressure chambers through clearance between the vane rotor and the housing and takes place inside the valve timing adjusting apparatus. The external leakage is leakage of hydraulic oil to an exterior of the valve timing adjusting apparatus through clearance between (a) the housing and (b) a shaft member that is journaled within the housing.

The valve timing adjusting apparatuses described in JP3567551B and JP-A-2006-77662 are capable of reducing the internal leakage of hydraulic oil, but are incapable of reducing the external leakage. As a result, it is required to increase the amount of supply of hydraulic oil in order to normally or properly rotate the vane rotor of the valve timing adjusting apparatus with consideration of the possible external leakage. The increase in the amount of hydraulic oil to be supplied requires more energy that sufficiently drives a pump for supplying the increased amount of hydraulic oil. Accordingly, the excessive energy supply may cause energy loss of engine, and thereby fuel efficiency may deteriorate disadvantageously.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to address at least one of the above disadvantages.

To achieve the objective of the present invention, there is provided a valve timing adjusting apparatus, which is mounted on a driving force transmission system that transmits driving force from a driving-side shaft of an internal combustion engine to a driven-side shaft for opening and closing at least one of intake and exhaust valves, and which adjusts timing of opening and closing the at least one of the intake and exhaust valves, the valve timing adjusting apparatus including a housing, a vane rotor, at least one shaft member, and at least one annular seal member. The housing is rotatable synchronously with the driving-side shaft, and the housing defines a receiving chamber in a predetermined angular range in a rotational direction. The vane rotor is rotatable synchronously with the driven-side shaft. The vane rotor sections the receiving chamber into a retard chamber and an advance chamber. The vane rotor is rotatable with respect to the housing in a retard direction or in an advance direction based on pressure of working fluid that is supplied to the retard chamber and the advance chamber. The at least one shaft member is provided on at least one of a first side of the vane rotor toward the driven-side shaft and a second side of the vane rotor opposite from the first side. The at least one shaft member is rotatable synchronously with the driven-side shaft and the vane rotor. The at least one shaft member is journaled within the housing. The at least one annular seal member is provided between the at least one shaft member and the housing. The at least one seal member limits leakage of working fluid from the receiving chamber to an exterior of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a schematic drawing illustrating a configuration of a valve timing adjusting apparatus and oil passages thereof according to the first embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3 is a schematic cross-sectional view illustrating exaggerated features in shapes of parts of the valve timing adjusting apparatus according to the first embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view illustrating exaggerated features in shapes of parts of a valve timing adjusting apparatus according to the second embodiment of the present invention;

FIG. 5 is a schematic drawing illustrating a configuration of a valve timing adjusting apparatus and oil passages thereof according to the third embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view illustrating exaggerated features in shapes of parts of the valve timing adjusting apparatus according to the third embodiment of the present invention;

FIG. 7 is a schematic cross-sectional view illustrating exaggerated features in shapes of parts of a valve timing adjusting apparatus according to the fourth embodiment of the present invention; and

FIG. 8 is a chart illustrating measurement results of leakage of hydraulic oil of a conventional valve timing adjusting apparatus and of the valve timing adjusting apparatus according to the fourth embodiment.

 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Multiple embodiments of the present invention will be described with reference to accompanying drawings.

First Embodiment

A valve timing adjusting apparatus according to the first embodiment of the present invention is shown in FIGS. 1 to 3. The valve timing adjusting apparatus of the first embodiment is an oil-actuated valve timing adjusting apparatus using hydraulic oil, which serves as working fluid, for adjustment of valve timing of an exhaust valve.

As shown in FIG. 1, a valve timing adjusting apparatus 10 includes a housing 20 and a vane rotor 50. The housing 20 includes a plate housing 21, a shoe housing 22, and a chain sprocket 23. The plate housing 21 and the shoe housing 22 are formed integrally with each other and are fixed coaxially with the chain sprocket 23 through bolts 12. Also, a positioning pin 6 is fitted into the shoe housing 22 and the chain sprocket 23 such that the shoe housing 22 and the chain sprocket 23 are positioned at certain positions. The chain sprocket 23 includes a gear 231 at an outer periphery of the chain sprocket 23.

A chain (not shown) is wound around the gear 231. In other words, the gear 231 of the housing 20 is connected with a crankshaft, which serves as a driving-side shaft of an engine, through the chain. As a result, the housing 20 receives driving force from the crankshaft and is rotatable synchronously with the crankshaft. The housing 20 is rotated in a clockwise direction as shown in FIG. 2.

A camshaft 15 shown in FIG. 1 and serving as a driven-side shaft receives driving force of the crankshaft through the housing 20, the vane rotor 50, and a journal 16. The camshaft 15 opens and closes an exhaust valve (not shown). The journal 16 serving as a shaft member is provided between the vane rotor 50 and the camshaft 15. The vane rotor 50, the journal 16, and the camshaft 15 are fixed coaxially with each other through a bolt 14. A positioning pin 7 is fitted into the vane rotor 50 and the journal 16 such that the vane rotor 50 is positioned relative to the journal 16 in the rotational direction. Also, another positioning pin (not shown) is fitted into the journal 16 and the camshaft 15 such that the journal 16 is positioned relative to the camshaft 15 in the rotational direction.

Due to the above configuration, the vane rotor 50, the journal 16, and the camshaft 15 are coaxially rotatable relative to the housing 20. The camshaft 15, the journal 16, the vane rotor 50, and the housing 20 are rotated in a clockwise direction when observed in a direction indicated by an arrow X. The rotational direction is defined as an advance direction of the camshaft 15 with respect to the crankshaft.

The journal 16 connecting with the camshaft 15 is received in the chain sprocket 23 and is rotatable with respect to the chain sprocket 23 by a predetermined phase difference. The journal 16 has an insertion portion that is received by the chain sprocket 23, and the insertion portion of the journal 16 has an outer diameter slightly smaller than an inner diameter of the chain sprocket 23. The journal 16 is journaled within the housing 20 in a state, where a part of an outer peripheral wall of the journal 16 is in contact with a part of an inner peripheral wall of the chain sprocket 23. A clearance 111 is defined between the outer peripheral wall of the journal 16 and the inner peripheral wall of the chain sprocket 23, and the clearance 111 has a generally crescent shape when observed in a direction opposite from the direction of the arrow X. A seal ring 30 is provided between the journal 16 and the chain sprocket 23.

As shown in FIG. 2, the shoe housing 22 of the housing 20 has a generally tubular peripheral wall 221 and shoes 222, 223, 224, 225 that projects from the peripheral wall 221 in a radially inner direction. Each of the shoes 222, 223, 224, 225 is formed into a generally trapezoid shape, and is arranged at the peripheral wall 221 at generally equal intervals in the rotational direction. Four fan-shaped receiving chambers 24 that respectively receive vanes of the vane rotor 50 are defined at predetermined angular ranges between the shoes 222, 223, 224, 225 in the rotational direction.

The vane rotor 50 has a hub portion 51 and the vanes 52, 53, 54, 55 that are arranged at an outer peripheral side of the hub portion 51 in the rotational direction at generally equal intervals. The vane rotor 50 is received inside the housing 20 and is rotatable with respect to the housing 20. Each of the vanes 52, 53, 54, 55 is rotatably received in the corresponding receiving chamber 24. It should be noted that the outer diameter of each vane of the vane rotor 50 is designed to be smaller than an inner diameter of the peripheral wall 221 of the shoe housing 22. Also, the hub portion 51 of the vane rotor 50 has an outer diameter that is designed to be smaller than an inner diameter of each shoe of the shoe housing 22. As a result, the outer peripheral wall of the vane rotor 50 is limited from sliding on the inner peripheral wall of the shoe housing 22.

Each of the vanes 52, 53, 54, 55 sections the corresponding receiving chamber 24 into (a) a retard oil pressure chamber serving as a retard chamber and (b) an advance oil pressure chamber serving as an advance chamber. In other words, a retard oil pressure chamber 81 is defined between the shoe 222 and the vane 52. A retard oil pressure chamber 82 is defined between the shoe 223 and the vane 53. A retard oil pressure chamber 83 is defined between the shoe 224 and the vane 54. A retard oil pressure chamber 84 is defined between the shoe 225 and the vane 55. Also, an advance oil pressure chamber 91 is defined between the shoe 225 and the vane 52. An advance oil pressure chamber 92 is defined between the shoe 222 and the vane 53. An advance oil pressure chamber 93 is defined between the shoe 223 and the vane 54. An advance oil pressure chamber 94 is defined between the shoe 224 and the vane 55.

Multiple seal chips 17 are provided between the housing 20 and the vane rotor 50. More specifically, the seal chip 17 is provided between the peripheral wall 221 of the shoe housing 22 and each of the vanes 52, 53, 54, 55. Also, the seal chip 17 is provided between the hub portion 51 of the vane rotor 50 and each of the shoes 222, 223, 224, 225. The seal chip 17 is fitted into a groove formed on the vane 52, 53, 54, 55 and is also fitted into a groove formed on the outer peripheral wall of the hub portion 51. For example, the seal chip 17 is pressed against the inner peripheral wall of the peripheral wall 221 of the shoe housing 22 or against the inner peripheral wall of the shoes 222, 223, 224, 225 by a spring. Due to the above configuration, the seal chips 17 fluid-tightly support the retard oil pressure chambers 81 to 84 and the advance oil pressure chambers 91 to 94, and thereby reduces leakage of hydraulic oil between each retard oil pressure chamber and the adjacent advance oil pressure chamber.

As shown in FIG. 1, the vane 52 of the vane rotor 50 defines a bore 521 that axially extends inside the vane 52 from an end surface of the vane 52 to a middle thereof but that does not extends through the vane 52 to open at the other end surface of the vane 52. The above end surface of the vane 52 is opposed to the chain sprocket 23. Due to the above configuration, a bottom portion 522 is formed on a side of the bore 521 or at the other end surface of the vane 52 toward the plate housing 21. The bore 521 is fitted with a tubular member 523. The tubular member 523 has a generally hollow cylindrical shape and defines a hole 524 on a peripheral wall of the tubular member 523. The hole 524 radially extends through the peripheral wall to provide communication between inside and outside of the tubular member 523. The tubular member 523 receives therein a stopper piston 100 and a spring 101 that serve as a limitation member. The stopper piston 100 has a generally hollow cylindrical shape and is axially reciprocably received in the tubular member 523. The spring 101 has one axial end portion contacting the bottom portion 522 and has the other axial end portion contacting the stopper piston 100. The spring 101 is a compression coil spring and exerts a force that is applied in opposite longitudinal directions. Due to the above spring force, the spring 101 biases the stopper piston 100 toward the chain sprocket 23.

The chain sprocket 23 defines a recess 232 that is press fitted with a fitting ring 102 serving as a fitting portion. The stopper piston 100 is fittable with the fitting ring 102. The stopper piston 100 and the fitting ring 102 have fitting parts that are fitted with the each other, and the fitting parts are tapered shapes. As a result, the stopper piston 100 is smoothly fitted with the fitting ring 102. The stopper piston 100 and the chain sprocket 23 define an oil pressure chamber 103 therebetween, and an oil pressure chamber 104 is defined between at an outer periphery of the stopper piston 100 and the inner periphery of the tubular member 523. Hydraulic oil that is supplied to the oil pressure chamber 103 and to the oil pressure chamber 104 has pressure applied to the stopper piston 100 in a direction such that the stopper piston 100 is disengaged from the fitting ring 102. The stopper piston 100 is engaged with or disengaged from the fitting ring 102 in accordance with balance between (a) biasing force by the spring 101 and (b) force applied by the oil pressure chamber 103 and the oil pressure chamber 104. As shown in FIG. 2, the oil pressure chamber 103 communicates with a retard oil pressure chamber 81 through a passage 525, and the oil pressure chamber 104 communicates with the retard oil pressure chamber 81 through the hole 524 and a passage 526.

FIG. 2 shows a state, where the vane rotor 50 is fully advanced with respect to the shoe housing 22. Because the stopper piston 100 is fitted with the fitting ring 102 in the above full advance state, the vane rotor 50 is connected with the chain sprocket 23, and thereby is limited from rotating relative to the chain sprocket 23. As a result, the vane rotor 50 is rotatable synchronously with the chain sprocket 23, or in other words, with the housing 20. In the above case, the vane 52 contacts a side surface of the shoe 222. Accordingly, even in a case, where the camshaft 15 receives rotational driving force from the crankshaft, and thereby the camshaft 15 receives torque reversals in positive and negative directions, the vane rotor 50 and the housing 20 are limited from rotating or vibrating relative to each other. Thereby, generation of noise caused by the contact between the vane rotor 50 and the housing 20 is limited effectively. When the stopper piston 100 is disengaged from the fitting ring 102, the vane rotor 50 is disconnected from the chain sprocket 23, and thereby the vane rotor 50 is enabled to rotate relative to the shoe housing 22 in an angular range from a full advance position to a full retard position.

As shown in FIG. 1, an oil pump 1 serving as a fluid supplier pumps hydraulic oil from an oil tank 2 and supplies hydraulic oil to a supply passage 3. A switching valve 70 is a known solenoid spool valve, and is provided between the camshaft 15 and the oil pump 1. More specifically, the switching valve 70 is provided between (a) a group of the supply passage 3 and a drain passage 4 and (b) another group of a retard passage 80 and an advance passage 90. The switching valve 70 includes a solenoid drive portion 71 and a spool 72. The switching valve 70 is supplied with a drive electric current from an electronic control device (ECU) 5 through the solenoid drive portion 71. The drive electric current is duty-ratio controlled. Thus, the switching valve 70 is switched or controlled based on the drive electric current, and thereby the spool 72 of the switching valve 70 is displaced based on the duty ratio of the drive electric current. The switching valve 70 controls supply of hydraulic oil to the retard oil pressure chambers 81, 82, 83, 84 and to the advance oil pressure chambers 91, 92, 93, 94 based on the position of the spool 72. Also, the switching valve 70 is switched to control discharge of hydraulic oil from the retard oil pressure chambers 81, 82, 83, 84 and from the advance oil pressure chambers 91, 92, 93, 94 based on the position of the spool 72. The above switching control enables the switching valve 70 to be switched between a first state 701, a second state 702, and a third state 703. The first to third states 701 to 703 will be described later. When the switching valve 70 is under the first state 701, the switching valve 70 is deenergized.

The camshaft 15 has an outer peripheral wall that is journaled by a bearing (not shown), and the outer peripheral wall defines thereon annular passages 151, 152. The annular passage 151 is connected with the retard passage 80, and the annular passage 152 is connected with the advance passage 90. Four retard passages 85 are axially formed inside the camshaft 15, the journal 16, and the hub portion 51, and each of the retard passages 85 provides communication among the camshaft 15, the journal 16, and the hub portion 51. The retard passages 85 communicate with the annular passage 151.

The camshaft 15 defines therein an advance passage 95 that connects the annular passage 152 with a side of the camshaft 15 adjacent the journal 16. An advance passage 96 having a generally hollow cylindrical shape is defined between (a) an inner peripheral wall 161 of the journal 16 and (b) an outer peripheral wall of the bolt 14. As above, the journal 16 has a generally hollow cylindrical shape. Also, an advance passage 97 having a generally hollow cylindrical shape is defined between an inner peripheral wall 511 of the hub portion 51 and an outer peripheral wall of the bolt 14. As above, the hub portion 51 has a generally hollow cylindrical shape. The advance passage 96 connects the advance passage 95 with the advance passage 97.

As shown in FIG. 2, the hub portion 51 defines therein four retard passages 86 that connect the retard passages 85 with the retard oil pressure chambers 81 to 84, respectively. Due to the above configuration, the retard passage 80 is communicated with each of the retard oil pressure chambers 81 to 84 through the annular passage 151 and the retard passages 85, 86. Also, the hub portion 51 defines therein four advance passages 98 that connect the advance passage 97 with each of the advance oil pressure chambers 91 to 94. Due to the above configuration, the advance passage 90 is connected with each of the advance oil pressure chambers 91 to 94 through the annular passage 152 and the advance passage 95, 96, 97, 98.

Next, the seal ring 30 is detailed with reference to FIG. 1 and FIG. 3. It should be noted that FIG. 3 is a schematic cross-sectional view of the valve timing adjusting apparatus 10 and shows each of components having a dimension ratio different from an actual ratio such that features in shape of the component are emphasized.

The seal ring 30 serving as a seal member is made of resin and is formed into a generally circular ring shape, for example, and is provided between the journal 16 and the chain sprocket 23 as shown in FIGS. 1, 3. The seal ring 30 has an inner peripheral wall that fluid tightly contacts the outer peripheral wall of the journal 16 over an entire perimeter of the journal 16. The inner peripheral wall of the chain sprocket 23 that is opposed to the outer peripheral wall of the journal 16 defines thereon a groove 233 having a circular ring shape. The groove 233 receives an outer peripheral edge portion of the seal ring 30.

In a state, where the journal 16 is journaled within or is pivotally supported by the housing 20, a clearance 111 is defined between the outer peripheral wall of the journal 16 and the inner peripheral wall of the chain sprocket 23. The clearance 111 has a generally crescent shape when observed in a direction Y in FIG. 3. The seal ring 30 has a dimension or a width of W in a radial direction, and the clearance 111 has a maximum dimension or width of C that is measured at maximum between the journal 16 and the chain sprocket 23 in the radial direction of the journal 16. The width W of the seal ring 30 is designed or determined to satisfies a relation of C<W. Due to the above configuration, leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 111 is reduced.

As above, the chain (not shown) is wound around the gear 231 of the chain sprocket 23. As a result, in a state, where the journal 16 is journaled within the housing 20, tensile force of the chain is applied as bearing load to the outer peripheral wall of the journal 16 through the chain sprocket 23. In the present embodiment, the groove 233 has a dimension or depth of D in the radial direction, the width W of the seal ring 30 is designed to satisfy a relation of W≦D. Therefore, in a state, where the journal 16 is journaled within the housing 20, the bearing load is applied to a group of the journal 16 and the chain sprocket 23 or is applied to both a first group of the journal 16 and the seal ring 30 and a second group of the journal 16 and the chain sprocket 23. As a result, the bearing load is limited from being applied excessively and exclusively to the seal ring 30, and thereby the abnormal wear of the seal ring 30 is effectively limited.

Next, the operation of the valve timing adjusting apparatus 10 will be described.

(1) As shown in FIGS. 1, 2, in a case, where hydraulic oil from the oil pump 1 has not been introduced into the oil pressure chambers 103, 104 in the event of starting the engine, the rotation of the crankshaft causes the vane rotor 50 to be located at the full advance position relative to the shoe housing 22. Also, at this time, the biasing force of the spring 101 causes the stopper piston 100 to be fitted with the fitting ring 102, and the stopper piston 100 causes the vane rotor 50 to be connected with the chain sprocket 23.

(2) When the first state 701 of the switching valve 70 is selected, and thereby hydraulic oil is pumped from the oil pump 1, hydraulic oil flows into the advance oil pressure chambers 91, 92, 93, 94 through the advance passage 90, the annular passage 152, and the advance passage 95, 96, 97, 98. Then, pressure of hydraulic oil that has flown into the advance oil pressure chambers 91, 92, 93, 94 is applied to the side surfaces of the vanes 52, 53, 54, 55, respectively. However, because the stopper piston 100 is fitted with the fitting ring 102, the vane rotor 50 is held at the full advance position relative to the shoe housing 22 as shown in FIG. 2. Thus, the noise caused when the vane rotor 50 is brought into contact with the shoe housing 22 is effectively prevented.

(3) When the operation of the switching valve 70 is switched from the first state 701 to the third state 703, hydraulic oil is introduced from the oil pump 1 to the retard oil pressure chambers 81, 82, 83, 84 through the retard passage 80, the annular passage 151, and the retard passages 85, 86. Also, hydraulic oil is introduced into the oil pressure chamber 103 through the passage 525, and hydraulic oil is introduced into the oil pressure chamber 104 through the passage 526 and the hole 524. In the above state, hydraulic oil in the advance oil pressure chambers 91, 92, 93, 94 is released to the oil tank 2. When pressure of hydraulic oil that has been introduced to the oil pressure chamber 103 and the oil pressure chamber 104 is increased, the stopper piston 100 is displaced in a direction for pushing the stopper piston 100 into the bore 521 toward the plate housing 21 against the biasing force of the spring 101. Then, the stopper piston 100 is completely disengaged from the fitting ring 102, and thereby the connection of the vane rotor 50 with the chain sprocket 23 is disabled. In other words, the vane rotor 50 is disconnected from the chain sprocket 23.

When pressure of hydraulic oil that has entered into the retard oil pressure chambers 81, 82, 83, 84 is applied to the side surfaces of the vanes 52, 53, 54, 55, the vane rotor 50 is rotated relative to the shoe housing 22 in a retard direction shown in FIG. 2, and thereby valve timing of the exhaust valve that is opened and closed by the camshaft 15 is retarded. When the rotation of the vane rotor 50 relative to the shoe housing 22 causes the vane rotor 50 to be displaced from the full advance position, the stopper piston 100 is displaced from the fitting ring 102 in the circumferential direction, and thereby the fitting of the stopper piston 100 with the fitting ring 102 is prevented.

(4) When the operation of the switching valve 70 is again switched into the first state 701, the vane rotor 50 is rotated relative to the shoe housing 22 in the advance direction shown in FIG. 2, and thereby the valve timing of the exhaust valve opened and closed by the camshaft 15 is advanced. In a case where the operation of the switching valve 70 is switched into the second state 702 while the vane rotor 50 is rotated relative to the shoe housing 22 in the advance direction or in the retard direction, hydraulic oil in the retard oil pressure chambers 81, 82, 83, 84 and the advance oil pressure chambers 91, 92, 93, 94 becomes limited from flowing therefrom and flowing therein. As a result, the vane rotor 50 is held at an intermediate position, and thereby required valve timing is obtained. The above intermediate position is a position somewhere between the full advance position and the full retard position, for example.

As described above, in the first embodiment, the seal ring 30 having the circular ring shape is provided between the journal 16 and the chain sprocket 23. Due to the above configuration, hydraulic oil in the retard oil pressure chambers and the advance oil pressure chambers defined in the housing 20 is limited from leaking to the exterior of the housing 20 through the clearance 111 between the journal 16 and the chain sprocket 23. As a result, it is possible to reduce supply amount of hydraulic oil used for driving the valve timing adjusting apparatus 10. Thereby, it is possible to increase the drive efficiency of the valve timing adjusting apparatus 10.

Also, in the first embodiment, the outer peripheral edge portion of the seal ring 30 is received by the groove 233, which has the circular ring shape, and which is defined at the inner peripheral wall of the chain sprocket 23. Thus, the inner peripheral wall of the seal ring 30 fluid tightly contacts the outer peripheral wall of the journal 16 over the entire perimeter of the journal 16. Due to the above configuration, leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 is effectively reduced.

Furthermore, in the first embodiment the radial dimension or the depth of the groove 233 formed at the inner peripheral wall of the chain sprocket 23 is defined as D, the radial dimension or the width of the seal ring 30 is defined as W, and the maximum dimension of the clearance 111 measured between the journal 16 and the chain sprocket 23 in the radial direction of the journal 16 is defined as C. In the above case, the relation of C<W≦D is satisfied. Because the relation of C<W is satisfied, it is possible to reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 111. Also, because the relation of W≦D is satisfied, the bearing load is applied to the group of the journal 16 and the chain sprocket 23, or to both the first group of the journal 16 and the seal ring 30 and the second group of the journal 16 and the chain sprocket 23 in a state, where the journal 16 is journaled within the housing 20. Thus, the bearing load is limited from being applied solely to the seal ring 30, and thereby the seal ring 30 is limited from receiving excessive bearing load thereon. Due to the above configuration, it is possible to prevent the seal ring 30 from wearing abnormally or excessively. As a result, it is possible to reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20, and also it is possible to prevent the abnormal wear of the seal ring 30.

Second Embodiment

FIG. 4 shows a valve timing adjusting apparatus according to the second embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of the valve timing adjusting apparatus of the second embodiment, and the dimension ratio of each component is different from an actual ratio such that the features in shape of the components are highlighted. It should be noted that the second embodiment is modification of the first embodiment, and thereby components of the valve timing adjusting apparatus of the second embodiment are basically the same as the components of the valve timing adjusting apparatus of the first embodiment. However, some of the components in the second embodiment are different from those in the first embodiment. Similar components of the valve timing adjusting apparatus of the present embodiment, which are similar to the components of the valve timing adjusting apparatus of the first embodiment, will be indicated by the same numerals, and the description of the similar configuration will be omitted.

The seal ring 30 is provided between the journal 16 and the chain sprocket 23 similarly to the first embodiment. The outer peripheral wall of the seal ring 30 fluid tightly contacts the inner peripheral wall of the chain sprocket 23 over the entire perimeter. The outer peripheral wall of the journal 16 defines thereon a groove 162 at a part of the outer peripheral wall opposed to the inner peripheral wall of the chain sprocket 23. The groove 162 has a circular ring shape. The groove 162 receives therein the inner peripheral edge portion of the seal ring 30.

In a state, where the journal 16 is journaled within the housing 20, the clearance 111 is defined between the outer peripheral wall of the journal 16 and the inner peripheral wall of the chain sprocket 23 similar to the first embodiment. The clearance 111 has the generally crescent shape when observed in direction Y in FIG. 4. In a case, where the width of the seal ring 30 in the radial direction is W and the maximum dimension or width of the clearance 111 defined between the journal 16 and the chain sprocket 23 in the radial direction of the journal 16 is C, the dimension or width W of the seal ring 30 is designed to satisfy the relation of C<W. Due to the above configuration, it is possible to reduce leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 111.

Also, in a case, where the dimension or depth of the groove 162 in the radial direction is D, the width W of the seal ring 30 is designed to satisfy the relation of W≦D. As a result, in a state, where the journal 16 is journaled within the housing 20, the bearing load is applied to the group of the journal 16 and the chain sprocket 23 or to both the first group of the journal 16 and the seal ring 30 and the second group of the journal 16 and the chain sprocket 23. As a result, the seal ring 30 is prevented from solely receiving excessive bearing load, and thereby the seal ring 30 is effectively limited from abnormally wearing.

As described above, in the second embodiment, the seal ring 30 having the circular ring shape is provided between the journal 16 and the chain sprocket 23 similar to the first embodiment. As a result, it is possible to reduce leakage of hydraulic oil through the clearance 111 from the interior of the housing 20 to the exterior of the housing 20. Thus, it is possible to reduce the amount of hydraulic oil supplied for driving the valve timing adjusting apparatus, and thereby the drive efficiency of the valve timing adjusting apparatus is improved.

Also, in the second embodiment, the inner peripheral edge portion of the seal ring 30 is received by the groove 162 having the circular ring shape and formed at the outer peripheral wall of the journal 16. Also, the outer peripheral wall of the seal ring 30 fluid tightly contacts the inner peripheral wall of the chain sprocket 23 over the entire perimeter. Due to the above configuration, it is possible to effectively reduce leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20.

Furthermore, in the second embodiment, in a case, where the depth of the groove 162 formed at the outer peripheral wall of the journal 16 is D, the width of the seal ring 30 is W, the maximum width of the clearance 111 defined between the journal 16 and the chain sprocket 23 is C, the relation of C<W≦D is satisfied. Due to the above configuration, similar to the first embodiment, it is possible to reduce leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20, and also it is possible to effectively limit the seal ring 30 from abnormally wearing.

Third Embodiment

FIGS. 5, 6 show a valve timing adjusting apparatus according to the third embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of the valve timing adjusting apparatus according to the third embodiment. In FIG. 6, a dimension ratio of each of the components is different from an actual dimension ratio thereof in order to highlight the features of the components in shape. Similar components of the valve timing adjusting apparatus of the present embodiment, which are similar to the components of the valve timing adjusting apparatus of the first embodiment, will be indicated by the same numerals, and the description of the similar configuration will be omitted.

In the third embodiment, as shown in FIG. 5, a bush 18 serving as a shaft member is provided to a side of the vane rotor 50 opposite from the camshaft 15 in addition to the journal 16 provided on the other side of the vane rotor 50 toward the camshaft 15. The bush 18 has a generally hollow cylindrical shape having a bottom portion 181. The bottom portion 181 defines therein a hole 182. The bush 18 is coaxially fixed to the camshaft 15, the journal 16 and the vane rotor 50 by inserting the bolt 14 into the hole 182. Also, the bush 18 is rotatable synchronously with the camshaft 15, the journal 16, and the vane rotor 50.

The bush 18 connected to the vane rotor 50 is received by the plate housing 21 and is rotatable relative to the plate housing 21 by a predetermined phase difference between the bush 18 and the plate housing 21. The bush 18 has an insertion part that is received by the plate housing 21, and the insertion part has an outer diameter slightly smaller than the inner diameter of the plate housing 21. The bush 18 is journaled within or pivotally supported by the housing 20 in a state, where the part of the outer peripheral wall is in contact with the inner peripheral wall of the plate housing 21. A seal ring 40 is provided between the bush 18 and the plate housing 21.

The seal ring 40 serving as a seal member is made of, for example, resin and is formed into a generally circular ring shape. As shown in FIGS. 5, 6, the inner peripheral wall of the seal ring 40 fluid tightly contacts the outer peripheral wall of the bush 18 over the entire perimeter. The inner peripheral wall of the plate housing 21 opposed to the outer peripheral wall of the bush 18 defines thereon a groove 211 having a circular ring shape. The seal ring 40 has an outer peripheral edge portion received by the groove 211.

In a state, where the bush 18 is journaled within the housing 20, a clearance 112 is defined between the outer peripheral wall of the bush 18 and the inner peripheral wall of the plate housing 21 The clearance 112 has a generally crescent shape when observed in a direction X in FIG. 6. In a case, where the seal ring 40 has a dimension or width of W1 in the radial direction and the clearance 112 defined between the bush 18 and the plate housing 21 has a dimension or width of C1 measured at maximum in the radial direction of the bush 18, the width W1 of the seal ring 40 is designed to satisfy the relation of C1<W1. Due to the above configuration, it is possible to reduce leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 112.

Also, in a case, where the groove 211 has a dimension or depth of D1 in the radial direction, the width W1 of the seal ring 40 is designed to satisfy the relation of W1≦D1. Therefore, in a state, where the bush 18 is journaled within the housing 20, bearing load is applied to a group of the bush 18 and the plate housing 21 or is applied to both a first group of the bush 18 and the seal ring 40 and a second group of the bush 18 and the plate housing 21. As a result, it is possible to prevent a situation, where the seal ring 40 solely receives excessive bearing load, and thereby it is possible to effectively limit the seal ring 40 from abnormally wearing.

As described above, in the third embodiment, the seal ring 40 having the circular ring shape is provided between the bush 18 and the plate housing 21. Accordingly, it is possible to reduce the leakage of hydraulic oil through the clearance 112 from the interior of the housing 20 to the exterior of the housing 20. Thus, it is possible to reduce the supply amount of hydraulic oil for driving valve timing adjusting apparatus, and thereby the drive efficiency of the valve timing adjusting apparatus is improved.

Also, in the third embodiment, the seal ring 40 has an outer peripheral edge portion that is received by the groove 211 having the circular ring shape and defined on the inner peripheral wall of the plate housing 21. The inner peripheral wall of the seal ring 40 fluid tightly contacts the outer peripheral wall of the bush 18 over the entire perimeter. Due to the above configuration, it is possible to effectively reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20.

Furthermore, in the third embodiment, the depth D1 of the groove 211 defined on the inner peripheral wall of the plate housing 21, the width W1 of the seal ring 40, and the maximum width C1 of the clearance 112 defined between the journal 16 and the chain sprocket 23 satisfy the relation of C1<W1≦D1. Due to the above configuration, it is possible to reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 112, and also it is possible to effectively limit the seal ring 40 from abnormally wearing.

As above, in the third embodiment, the journal 16 and the bush 18 are journaled within or pivotally supported by the housing 20. Also, the seal ring 30 is provided between the journal 16 and the chain sprocket 23 and the seal ring 40 is provided between the bush 18 and the plate housing 21. As a result, the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 111 and the leakage of hydraulic oil to the exterior through the clearance 112 are both reduced.

Fourth Embodiment

FIG. 7 shows a valve timing adjusting apparatus according to the fourth embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of the valve timing adjusting apparatus of the fourth embodiment, and a dimension ratio of each of the components is intentionally differentiated from an actual dimension ratio of the same in order to highlight the features of the components in shape. It should be noted that the fourth embodiment is modification of the third embodiment, and thereby the valve timing adjusting apparatus of the fourth embodiment basically includes similar components similar to those of the third embodiment. However, part of the components in the present embodiment has a shape different from that in the third embodiment. Similar components of the valve timing adjusting apparatus of the present embodiment, which are similar to the components of the valve timing adjusting apparatus of the third embodiment, will be indicated by the same numerals, and the description of the similar configuration will be omitted.

The seal ring 40 is provided between the bush 18 and the plate housing 21 similar to the third embodiment. The seal ring 40 has an outer peripheral wall fluid tightly contacting the inner peripheral wall of the plate housing 21 over the entire perimeter. The outer peripheral wall of the bush 18 defines a groove 183 having a circular ring shape at a part thereof opposed to the inner peripheral wall of the plate housing 21, and the part. The seal ring 40 has an inner peripheral edge portion received in the groove 183.

In a state, where the bush 18 is journaled within the housing 20, the clearance 112 is defined between the outer peripheral wall of the bush 18 and the inner peripheral wall of the plate housing 21 similar to the third embodiment. The clearance 112 has a generally crescent shape when observed in direction X in FIG. 7. In a case, where the seal ring 40 has a width of W1 in the radial direction, the clearance 112 defined between the bush 18 and the plate housing 21 has the width of C1 measured at maximum in the radial direction of the bush 18, the width W1 of the seal ring 40 is designed to satisfy the relation of C1<W1. Due to the above configuration, it is possible to effectively reduce leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 112.

Also, in a case, where the groove 183 has the depth of D1 in the radial direction, the width W1 of the seal ring 40 is designed to satisfy the relation of W1≦D1. Thereby, in a state, where the bush 18 is journaled within the housing 20, bearing load is applied to the group of the bush 18 and the plate housing 21 or is applied to the first group of the bush 18 and the seal ring 40 and the second group of the bush 18 and the plate housing 21. As a result, it is possible to prevent a case, where the seal ring 40 solely receives excessive bearing load, and thereby it is possible to effectively limit the seal ring 40 from abnormally wearing.

FIG. 8 shows a measurement result of a leakage amount of hydraulic oil of the valve timing adjusting apparatus of the fourth embodiment and that of a conventional valve timing adjusting apparatus. The conventional valve timing adjusting apparatus is not provided with the seal member between the shaft member and the housing. The chart in FIG. 8 has an ordinate axis indicating an amount of leaked hydraulic oil and has an abscissa axis indicating a dimension of clearance defined between the vane rotor and the housing in the longitudinal direction. In FIG. 8, a solid line L1 indicates an external leakage amount that is an amount of hydraulic oil leaking to the exterior of the valve timing adjusting apparatus of the fourth embodiment. A solid line L2 indicates a total leakage amount of (a) the above external leakage amount and (b) an internal leakage amount that is an amount of hydraulic oil leaking between the oil pressure chambers inside the valve timing adjusting apparatus of the fourth embodiment. In contrast, a dashed line L3 indicates an external leakage amount of the conventional valve timing adjusting apparatus, and a dashed line L4 indicates a total leakage amount of the above external leakage amount and an internal leakage amount of the conventional valve timing adjusting apparatus.

In comparison between L1 and L3, the external leakage amount of the valve timing adjusting apparatus of the fourth embodiment is substantially reduced compared with the external leakage amount of the conventional valve timing adjusting apparatus. The above is caused because it is possible to reduce the leakage of hydraulic oil through the clearance between the shaft member and the housing in the valve timing adjusting apparatus of the fourth embodiment due to the seal member provided between the shaft member and the housing. It should be noted that the external leakage amount is constant even when a dimension of clearance between the vane rotor and the housing in the axial direction is increased in the valve timing adjusting apparatus of the fourth embodiment and the conventional valve timing adjusting apparatus.

In comparison between L2 and L4, it is shown that the internal leakage amount is increased accordingly to the increase in the dimension of the clearance between the vane rotor and the housing in the valve timing adjusting apparatus of the fourth embodiment and the conventional valve timing adjusting apparatus. However, in the valve timing adjusting apparatus of the fourth embodiment, the seal member provided between the shaft member and the housing is capable of reducing the external leakage amount of hydraulic oil, and thereby the total leakage amount of hydraulic oil of the internal leakage amount and the external leakage amount in the valve timing adjusting apparatus is substantially reduced compared with the conventional valve timing adjusting apparatus.

As described above, in the fourth embodiment, the seal ring 40 having the circular ring shape is provided between the bush 18 and the plate housing 21 similar to the third embodiment. As a result, it is possible to reduce the leakage of hydraulic oil through the clearance 112 from the interior of the housing 20 to the exterior of the housing 20. Thereby, it is possible to reduce the supply amount of hydraulic oil for driving valve timing adjusting apparatus, and thereby the drive efficiency of the valve timing adjusting apparatus is improved.

Also, in the fourth embodiment, the inner peripheral edge portion of the seal ring 40 is received by the groove 183 having the circular ring shape and formed on the outer peripheral wall of the bush 18. The outer peripheral wall of the seal ring 40 fluid tightly contacts the inner peripheral wall of the plate housing 21 over the entire perimeter. Due to the above configuration, it is possible to effectively reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20.

Furthermore, in the fourth embodiment, the depth D1 of the groove 183 formed on the outer peripheral wall of the bush 18, the width W1 of the seal ring 40, and the maximum width C1 of the clearance 112 defined between the bush 18 and the plate housing 21 satisfy the relation of C1<W1≦D1. Due to the above configuration, similar to the third embodiment, it is possible to reduce the leakage of hydraulic oil from the interior of the housing 20 to the exterior of the housing 20 through the clearance 112, and also it is possible to effectively limit the seal ring 40 from abnormally wearing.

Other Embodiment

In the other embodiment of the present invention, the seal member provided between the shaft member and the housing may be alternatively made of any material, such as metal, and thus, the material of the seal member is not limited to the resin. Even in the above alternative case, where the material of the seal member is different from the resin, it is possible to reduce the leakage of hydraulic oil from the interior of the housing to the exterior of the housing similar to the above multiple embodiments. Also, In the other embodiment of the present invention, the journal that is journaled within the housing may be integrally provided to the camshaft.

In the above multiple embodiments, the seal member is solely provided between the shaft member and the housing on a side of the vane rotor toward the camshaft. Also, the seal members are provided at positions between the shaft member and the housing on the side of the vane rotor toward the camshaft and on the other side of the vane rotor opposite from the camshaft. However, in the other embodiment of the present invention, the seal member may be alternatively provided between the shaft member and the housing solely on a side of the vane rotor opposite from the camshaft.

Also, in the above multiple embodiments, the groove having the circular ring shape is defined on the shaft member or the housing and the part of the seal member is received by the groove. However, in the other embodiment of the present invention, the grooves may be defined on both the shaft member and the housing.

In the above multiple embodiments, the valve timing adjusting apparatus is applied to the exhaust valve of the engine. However, in the other embodiment of the present invention, the valve timing adjusting apparatus may be alternatively applied to the intake valve. It should be noted that the present invention may be applicable to a valve timing adjusting apparatus that is not provided with the stopper piston.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.

Claims

1. A valve timing adjusting apparatus mounted on a driving force transmission system that transmits driving force from a driving-side shaft of an internal combustion engine to a driven-side shaft for opening and closing at least one of intake and exhaust valves, wherein the valve timing adjusting apparatus adjusts timing of opening and closing the at least one of the intake and exhaust valves, the valve timing adjusting apparatus comprising:

a housing that is rotatable synchronously with the driving-side shaft, wherein the housing defines a receiving chamber in a predetermined angular range in a rotational direction;
a vane rotor that is rotatable synchronously with the driven-side shaft, wherein: the vane rotor sections the receiving chamber into a retard chamber and an advance chamber; and the vane rotor is rotatable with respect to the housing in a retard direction or in an advance direction based on pressure of working fluid that is supplied to the retard chamber and the advance chamber;
at least one shaft member that is provided on at least one of a first side of the vane rotor toward the driven-side shaft and a second side of the vane rotor opposite from the first side, wherein: the at least one shaft member is rotatable synchronously with the driven-side shaft and the vane rotor; and the at least one shaft member is journaled within the housing; and
at least one annular seal member that is provided between the at least one shaft member and the housing, wherein the at least one seal member limits leakage of working fluid from the receiving chamber to an exterior of the housing.

2. The valve timing adjusting apparatus according to claim 1, wherein:

the housing includes an annular groove defined at an inner peripheral wall of the housing;
the at least one seal member has an outer peripheral edge portion received by the groove of the housing; and
the at least one seal member has an inner peripheral wall that fluid-tightly contacts an outer peripheral wall of the at least one shaft member over an entire perimeter of the at least one shaft member.

3. The valve timing adjusting apparatus according to claim 1 wherein:

the at least one shaft member includes an annular groove defined at an outer peripheral wall of the at least one shaft member;
the at least one seal member has an inner peripheral edge portion received by the groove of the at least one shaft member; and
the at least one seal member has an outer peripheral wall that fluid-tightly contacts an inner peripheral wall of the housing over an entire perimeter of the housing.

4. The valve timing adjusting apparatus according to claim 2, wherein;

the groove of the housing has a dimension of D in a radial direction of the groove;
the at least one seal member has a dimension of W in a radial direction of the at least one seal member;
the housing and the at least one shaft member define therebetween a clearance having a maximum dimension of C measured in a radial direction of the at least one shaft member; and
C<W≦D is satisfied.

5. The valve timing adjusting apparatus according to claim 3, wherein:

the groove of the at least one shaft member has a dimension of D in a radial direction of the groove;
the at least one seal member has a dimension of W in a radial direction of the at least one seal member;
the housing and the at least one shaft member define therebetween a clearance having a maximum dimension of C measured in a radial direction of the at least one shaft member; and
C<W≦D is satisfied.
Patent History
Publication number: 20090199799
Type: Application
Filed: Feb 4, 2009
Publication Date: Aug 13, 2009
Applicant: DENSO CORPORATION (Kariya-city)
Inventor: Tadao Ikihara (Okazaki-city)
Application Number: 12/365,309
Classifications
Current U.S. Class: Camshaft Or Cam Characteristics (123/90.17); Actuated By Fluid Or Electricity (464/2)
International Classification: F01L 1/34 (20060101);