Valve timing adjustment device and method for manufacturing valve timing adjustment device

Provided is a valve timing adjustment device that suppresses slippage of an assist spring, prevents disengagement, and facilitates assembly of the assist spring. A valve timing adjustment device adjusts an opening timing and closing timing of an intake valve or an exhaust valve of an internal combustion engine. In the assist spring, the inner peripheral end portion is formed in a non-bent shape, the outermost periphery is in contact with the rib, a second winding is in contact with the inner peripheral end portion, and there is no contact between windings from the second winding to the outermost periphery.

TECHNICAL FIELD

The present disclosure relates to a valve timing adjustment device including a spiral-spring-type assist spring that biases a rotor.

BACKGROUND ART

Conventionally, a variable valve timing adjustment device that controls an opening timing and closing timing of an intake valve or an exhaust valve of an internal combustion engine for an automobile has been devised, and a vane type hydraulic actuator is often adopted. In some variable valve timing adjustment devices, an assist spring that biases a rotor in which a vane is formed in one direction is disposed for the purpose of returning to a reference position or equalizing an operation speed. Various types of the assist spring are conceivable depending on a disposition position and a spring shape, but for example, there is also an example in which a spiral spring is adopted from a viewpoint of a disposition space and a spring constant.

This spring is formed in such a manner that an inner peripheral end thereof is bent toward a center, and is disposed so as to be engaged with an engagement groove formed at an end portion of an extending portion of a boss portion. In addition, the spring is formed in a hook shape in such a manner that an outer peripheral end thereof is bent radially outward and then folded back, and is disposed so as to be engaged with an engagement pin. In addition, in order to be able to suppress omission and positional deviation of the inner peripheral end, the spring is disposed in such a manner that a wire gap between a plurality of specific points of an element wire is substantially zero, that is, in a state where the plurality of specific points is in a slight contact with each other. Note that the engagement groove and the inner peripheral end of the spring are located near the specific points, and the specific points are located near the engagement pin (see, for example, Patent Literature 1).

CITATION LIST

Patent Literature

Patent Literature 1: JP 2013-36395 A

SUMMARY OF INVENTION

Technical Problem

In the conventional valve timing adjustment device described above, the spring is formed in such a manner that an inner peripheral end of the spring is bent toward a center, and is disposed so as to be engaged with an engagement groove formed at an end portion of an extending portion of a boss portion. As a result, there is a problem that the spring slides due to torque fluctuation or engine vibration, and the engagement is released from the engagement groove. In addition, the spring is disposed in a state where a plurality of specific points of an element wire are in a slight contact with each other. Therefore, the spring is engaged with the engagement groove in a state where torque is applied. As a result, there is a problem that a spring assembling property is deteriorated.

The present disclosure has been made in order to solve the above-described problems, and an object of the present disclosure is to obtain a valve timing adjustment device that suppresses slippage of an assist spring, prevents disengagement, and facilitates assembly of the assist spring.

Solution to Problem

A valve timing adjustment device according to the present disclosure includes: a first rotating body that has a bottomed cylindrical shape with a plurality of operating hydraulic chambers therein, a bottom of the bottomed cylindrical shape being penetrated by a distal end of a camshaft, and has an opening closed by a disk-shaped plate; a second rotating body that has a vane that divides each of the operating hydraulic chambers into an advanced angle side and a retarded angle side, is disposed inside the first rotating body, is fixed to the distal end of the camshaft, relatively rotates with respect to the first rotating body, has a substantially columnar shape, forms the vane having a protruding shape on an outer periphery of the substantially columnar shape, and has a through hole forming a two-surface width portion on a central axis of the substantially columnar shape; a holder that is disposed on the axis of the second rotating body outside the plate of the first rotating body, has a substantially cylindrical shape, and is fixed to the second rotating body with a two-surface width formed by two opposing sides of a polygonal shape of an outer peripheral surface of the substantially cylindrical shape; a protrusion-shaped rib disposed outside the plate of the first rotating body and protruding from the first rotating body; and a spiral-spring-type assist spring that is disposed outside the plate of the first rotating body, has an outer peripheral end portion fixed to the first rotating body, has an innermost periphery and an inner peripheral end portion wound around an outer periphery of the holder and fixed to the second rotating body, and biases the second rotating body in one direction with respect to the first rotating body. In the assist spring, the inner peripheral end portion is formed in a non-bent shape, an outer side of an outermost periphery is in contact with the rib, a second winding is in contact with the inner peripheral end portion, and there is no contact between windings from the second winding to the outermost periphery.

Advantageous Effects of Invention

The valve timing adjustment device configured as described above is formed by winding the inner peripheral end portion of the assist spring around the holder in a non-bent shape. In addition, the second winding is in contact with the inner peripheral end portion, and there is no contact between windings from the second winding to the outermost periphery. Therefore, the valve timing adjustment device that suppresses slippage of the assist spring, prevents disengagement, and facilitates assembly of the assist spring can be obtained.

DESCRIPTION OF EMBODIMENTS

Hereinafter, in order to describe the present disclosure in more detail, an embodiment for embodying the present disclosure will be described with reference to the attached drawings.

First Example

First Embodiment

A valve timing adjustment device according to a first embodiment will be described with reference toFIGS.1to6.FIG.1is a plan view illustrating a configuration example of the valve timing adjustment device according to the first embodiment.FIG.2is a cross-sectional view taken along line AA inFIG.1.FIG.3is a cross-sectional view taken along line BB inFIG.2.FIG.4is a diagram illustrating a state of a free length of an assist spring in the valve timing adjustment device according to the first embodiment.FIG.5is a diagram illustrating a state of the assist spring in the valve timing adjustment device according to the first embodiment at an operation angle, in whichFIG.5Aillustrates a state of a most advanced angle position, andFIG.5Billustrates a state of a most retarded angle position.FIG.6is a diagram illustrating a method for assembling the assist spring in the valve timing adjustment device according to the first embodiment, in whichFIGS.6(1) to6(4) illustrate an assembling procedure.

As illustrated inFIGS.1,2, and3, a valve timing adjustment device1includes, as a basic structure, a first rotating body having an operating hydraulic chamber, a second rotating body that has a vane3athat divides the operating hydraulic chamber into an advanced angle hydraulic chamber11and a retarded angle hydraulic chamber12, and relatively rotates with respect to the first rotating body, a spiral-spring-type assist spring5that biases the second rotating body in one direction with respect to the first rotating body; a holder4that is engaged with an inner peripheral end portion5aof the assist spring5and is fixed to the second rotating body, locking ribs8band8cthat are disposed in the first rotating body and lock an outer peripheral end portion5bof the assist spring5, and ribs13aand13bwith which an outer periphery of the assist spring5is in contact. Here, the first rotating body is a housing2, and the housing2includes a case7, a plate8, and a cover9. The second rotating body is a rotor3.

A sprocket portion7bis formed on an outer surface of the case7. A chain (not illustrated) is mounted on the sprocket portion7b, and a driving force of a crankshaft of an internal combustion engine is transmitted to the case7. This driving force causes the housing2to rotate synchronously with the crankshaft. Meanwhile, the rotor3and the holder4are fastened to a camshaft100of the internal combustion engine by a center bolt101and rotate synchronously with the camshaft100.

A hole through which a bolt10passes is formed in each of the case7and the cover9, and a female screw to which the bolt10is fastened is formed in the plate8. With the case7and the rotor3sandwiched between the plate8and the cover9, the case7, the plate8, and the cover9are coaxially fixed by a plurality of the bolts10.

A plurality of shoe portions7aprotruding inward is formed on an inner surface of the case7. A space surrounded by the shoe portions7a, the plate8, and the cover9is an operating hydraulic chamber. In the configuration example ofFIG.3, there are four operating hydraulic chambers. The rotor3is disposed inside the case7. A plurality of vanes3aprotruding outward is formed on the rotor3. On a central axis of the rotor3, a two-surface width portion3bto which the holder4is fitted and fixed is formed on an inner periphery, and a hole being penetrated by the center bolt101is drilled. Each of the plurality of vanes3ais disposed in each of the plurality of operating hydraulic chambers of the case7. One vane3adivides one operating hydraulic chamber into the advanced angle hydraulic chamber11and the retarded angle hydraulic chamber12.

By operating oil being supplied to the advanced angle hydraulic chamber11or the retarded angle hydraulic chamber12via a hydraulic path100aformed inside the camshaft100and the rotor3, the rotor3relatively rotates with respect to the housing2, and a relative angle of the rotor3with respect to the housing2is adjusted to an advanced angle side or a retarded angle side. When the relative angle of the rotor3with respect to the housing2is adjusted, a rotational phase of the camshaft100with respect to the crankshaft changes to an advanced angle side or a retarded angle side, and an opening timing and closing timing of an intake valve or an exhaust valve also changes.

The holder4has a bottomed cylindrical shape, has an outer peripheral surface formed in a polygonal shape such as a substantially octagonal shape, and has a two-surface width formed by two opposing sides. In the holder4, a cylindrical portion4band a hole4care formed by a steel plate being pressed. An innermost periphery5c, which is the first winding of the assist spring5, is wound around an outer peripheral surface of the cylindrical portion4b, and the inner peripheral end portion5ais engaged therewith. The holder4is fastened to the rotor3and the camshaft100by the center bolt101inserted into the hole4c.

The assist spring5biases the rotor3toward an advanced angle side with respect to the housing2in order to oppose a reaction force that the camshaft100receives from the intake valve or the exhaust valve. The assist spring5is a spiral spring in which a square wire is horizontally wound, and is fixed to the rotor3by the holder4and is fixed to the plate8of the housing2by the locking ribs8band8c. The inner peripheral end portion5aof the assist spring5is formed in a non-bent shape, while the outer peripheral end portion5bis formed in a bent shape. Note that the outer peripheral end portion5bmay have a hook shape or the like. The innermost periphery5c, which is the first winding of the assist spring5, is wound around an outer peripheral surface of the cylindrical portion4b. By the inner peripheral end portion5aof the assist spring5being engaged with the outer peripheral surface of the cylindrical portion4b, the inner peripheral end portion5aof the assist spring5is fixed to the holder4and connected to the rotor3. By the outer peripheral end portion5bof the assist spring5being engaged with a groove8aformed by the locking ribs8band8carranged on the plate8, the outer peripheral end portion5bof the assist spring5is fixed to the plate8.

An outer peripheral side of an outermost periphery5dof the assist spring5is in contact with the ribs13aand13b, and release of the assist spring5is restricted. A second winding5eof the assist spring5is in contact with the inner peripheral end portion5a, and the assist spring5biases the inner peripheral end portion5atoward the holder4. In addition, a third winding5fand the second winding5eare not in contact with each other, and for example, in the configuration example ofFIG.1, the third winding5fand the second winding5eare not in contact with each other near the inner peripheral end portion5a. The third winding5fof the assist spring5is excluded from the biasing of the inner peripheral end portion5atoward the holder4. In addition, similarly, there is no contact between windings from the third winding5fto the outermost periphery5d. Note that, in the configuration example ofFIG.1, the number of windings of the assist spring5is four, but the number of windings is not limited to that of the configuration example.

The locking ribs8band8care protrusions that are projected on the assist spring5side of the plate8so as to face each other and form the groove8a. The locking ribs8band8care formed upright by press-fitting into holes drilled in the plate8, formed by attachment with bolts (not illustrated), or formed by processing the plate8, for example. The outer peripheral end portion5bof the assist spring5is engaged with the groove8aformed by the locking ribs8band8c.

The ribs13aand13bare protrusions projected on the assist spring5side of the plate8. The ribs13aand13bare formed upright by press-fitting into holes drilled in the plate8, formed by attachment with bolts (not illustrated), or formed by processing the plate8, for example. The number of the ribs13aand13bto be disposed is at least one. An outer peripheral side of the outermost periphery5dof the assist spring5is in contact with the ribs13aand13b, and release of the assist spring5is restricted. Note that, in the configuration example ofFIG.1, the two ribs13aand13bare disposed at two positions on an outer peripheral portion of the plate8, but the number and disposition positions of the ribs13aand13bare not limited to those of the configuration example ofFIG.1.

As illustrated inFIG.4, in the assist spring5, element wires are not in contact with each other in a free length state. That is, all the element wires including the inner peripheral end portion5a, the innermost periphery (first winding)5c, the second winding5e, the third winding5f, and the outer peripheral end portion5bof the outermost periphery5dare formed so as to have a gap therebetween. Note that, in the configuration example ofFIG.4, the number of windings of the assist spring5is four, but the number of windings is not limited to that of the configuration example. The assist spring5has been subjected to shot peening. The shot peening improves fatigue strength resistance due to processing hardening.

As illustrated inFIG.5, the valve timing adjustment device1is used within an operation angle range between a most advanced angle position and a most retarded angle position. Within the operation angle range of the valve timing adjustment device1, the second winding5eof the assist spring5is in contact with the inner peripheral end portion5a, and the assist spring5biases the inner peripheral end portion5atoward the holder4. In addition, the third winding5fand the second winding5eare not in contact with each other, and the third winding5fof the assist spring5is excluded from the biasing of the inner peripheral end portion5atoward the holder4. In addition, similarly, there is no contact between windings from the third winding5fto the outermost periphery5d. Note that, in the configuration example ofFIG.5, the number of windings of the assist spring5is four, but the number of windings is not limited to that of the configuration example.

Next, an operation of the valve timing adjustment device configured as described above will be described with reference toFIGS.1to5.

As illustrated inFIGS.1,2, and3, a driving force of a crankshaft of an internal combustion engine is transmitted to the case7by a chain (not illustrated). This driving force causes the housing2to rotate synchronously with the crankshaft. Meanwhile, the rotor3and the holder4rotate synchronously with the camshaft100. By operating oil being supplied to the advanced angle hydraulic chamber11or the retarded angle hydraulic chamber12, the rotor3relatively rotates with respect to the housing2, and a relative angle of the rotor3with respect to the housing2is adjusted to an advanced angle side or a retarded angle side. Then, a rotational phase of the camshaft100with respect to the crankshaft changes to an advanced angle side or a retarded angle side, and an opening timing and closing timing of an intake valve or an exhaust valve also changes. In this state, the rotor3is biased toward an advanced angle side with respect to the housing2by the assist spring5in order to oppose a reaction force that the camshaft100receives from the intake valve or the exhaust valve.

As illustrated inFIGS.1and5, the inner peripheral end portion5aof the assist spring5has a non-bent shape, and the innermost periphery (first winding)5cis wound around and engaged with an outer peripheral surface of the cylindrical portion4b. Within the operation angle range, the second winding5eof the assist spring5is in contact with the inner peripheral end portion5a, and the inner peripheral end portion5ais biased toward the holder4. As a result, slippage between the assist spring5and the holder4due to torque fluctuation or engine vibration is suppressed. As a result, disengagement of the assist spring5is prevented.

In addition, within the operation angle range, the third winding5fof the assist spring5and the second winding5ethereof are not in contact with each other, and the third winding5fis excluded from the biasing of the inner peripheral end portion5atoward the holder4. In addition, similarly, there is no contact between windings from the third winding5fto the outermost periphery5d. Therefore, hysteresis due to contact between element wires of the assist spring5is suppressed.

In addition, an outer peripheral side of the outermost periphery5dof the assist spring5is in contact with the ribs13aand13b, and release of the assist spring5is restricted. Therefore, resonance of the assist spring5due to engine vibration is suppressed.

As illustrated inFIG.4, in the assist spring5, element wires are not in contact with each other in a free length state. That is, since there is a gap between the element wires, shot peening is performed on the entire surface.

Next, a method for manufacturing a valve timing adjustment device related to assembly of the assist spring5of the valve timing adjustment device configured as described above will be described with reference toFIG.6.

As illustrated inFIG.6(1), in a first step, the outer peripheral end portion5bof the assist spring5is fitted to the groove8aand engaged with and fixed to the locking ribs8band8c.

As illustrated inFIG.6(2), in a second step, the innermost periphery5cof the assist spring5is rotated, the diameter of the outermost periphery5dis reduced, and the outermost periphery5dis fitted to inner peripheral sides of the ribs13aand13b.

As illustrated inFIG.6(3), in a third step, the holder4is rotated, and the position of the shape of the innermost periphery5cof the assist spring5and the position of the shape of the outer periphery of the holder4are matched, that is, are matched to a position in a state of being wound. Thereafter, the innermost periphery5cis fitted to the outer periphery of the holder4, and the inner peripheral end portion5ais engaged with the outer periphery of the holder4.

As illustrated inFIG.6(4), in a fourth step, the holder4is twisted and rotated, and the position of the two-surface width formed by two sides of the outer periphery of the holder4and the position of the two-surface width portion3bformed on an inner periphery of the rotor3are matched. Thereafter, the holder4is fitted to the two-surface width portion3b, and the holder4is fixed. That is, the inner peripheral end portion5aof the assist spring5is fixed to the rotor3, and the assist spring5of the valve timing adjustment device1is assembled, thus manufacturing the valve timing adjustment device.

As described above, in the valve timing adjustment device described in the first embodiment, the inner peripheral end portion5aof the assist spring5is formed in a non-bent shape, and the innermost periphery (first winding)5cis wound around and engaged with the outer peripheral surface of the cylindrical portion4b. Then, the second winding5eis in contact with the inner peripheral end portion5a, and the inner peripheral end portion5ais biased toward the holder4. As a result, it is possible to suppress slippage between the assist spring5and the holder4due to torque fluctuation or engine vibration, and as a result, it is possible to prevent disengagement of the assist spring5.

In addition, the third winding5fof the assist spring5and the second winding5ethereof are not in contact with each other. In addition, similarly, there is no contact between windings from the third winding5fto the outermost periphery5d. As a result, the assist spring5can be assembled by applying a low torque, and the assembly of the assist spring5is facilitated.

Furthermore, the third winding5fof the assist spring5and the second winding5ethereof are not in contact with each other. In addition, similarly, there is no contact between windings from the third winding5fto the outermost periphery5d. Therefore, hysteresis due to contact between element wires of the assist spring5is suppressed.

In addition, an outer peripheral side of the outermost periphery5dof the assist spring5is in contact with the ribs13aand13b. Therefore, resonance of the assist spring5due to engine vibration is suppressed.

In addition, in the assist spring5, element wires are not in contact with each other in a free length state, and therefore there is a gap between the element wires. As a result, shot peening can be performed on the entire surface, and as a result, fatigue strength resistance is improved.

By the way, the valve timing adjustment device1described in the above embodiment may be used on either an intake side or an exhaust side. In addition, a biasing direction of the assist spring5may be either an advanced angle side or a retarded angle side.

In addition, since the structure of the assist spring5of the first embodiment does not affect the internal structure of the valve timing adjustment device1, it goes without saying that the structure of the assist spring5of the first embodiment can be applied to a device other than the valve timing adjustment device1having the illustrated internal structure.

Note that the present disclosure can modify any constituent element in the embodiment, or omit any constituent element in the embodiment within the scope of the disclosure.

INDUSTRIAL APPLICABILITY

The valve timing adjustment device according to the present disclosure can be used for a valve timing adjustment device that adjusts an opening timing and closing timing of an intake valve or an exhaust valve of an internal combustion engine, and the like.

REFERENCE SIGNS LIST