valve timing control unit

Abstract

The valve timing control unit has a valve timing control mechanism constituted by a driving-side rotary body, a driven-side rotary body, a motor and a reduction gear that set the relative rotational phase, and a phase sensor unit that detects the actual phase of the driving-side rotary body and the driven-side rotary body. The valve timing control unit has a control section that controls the motor in the direction in which the phase difference between the actual phase and the target phase is reduced, and the control section includes a swing control section that swings the target phase in the vicinity of the maintained target phase when the target phase is maintained at a constant value and the variation amount of the actual phase is kept in a holding region where the variation amount is less than a set value.

Description

Technical Field

[0001] This invention relates to a valve timing control unit. Background Technology

[0002] In internal combustion engines, specifically four-stroke engines, variable valve devices are known to adjust the opening and closing timing of intake or exhaust valves, as shown in Japanese Patent Application Publication No. 2004-332671, Japanese Patent Application Publication No. 2008-286120, and Japanese Patent Application Publication No. 2019-157679.

[0003] Japanese Patent Application Publication No. 2004-332671 discloses a variable valve device that, in order to simultaneously and continuously control the lift and operating angle (lift characteristic) of an intake valve, determines the valve lift characteristic based on the rotational position of a control shaft equipped with an eccentric cam. In this device, an actuator connected via a worm gear mechanism drives the control shaft, thereby setting the control method for the lift characteristic.

[0004] In particular, the aforementioned Japanese Patent Application Publication No. 2004-332671 describes the following: when the target rotational position of the control axis is maintained at a certain value for a specified period of time, the control actuator forces the control axis to reciprocate with a small amplitude.

[0005] Furthermore, Japanese Patent Application Publication No. 2008-286120 discloses a variable valve mechanism in which a nut is driven to rotate by an electric motor, causing a planetary gear shaft screwed into the nut to move linearly, thereby changing the maximum lift of the intake valve. Also in Japanese Patent Application Publication No. 2008-286120, a control method is disclosed in which, at the moment the change of the maximum lift ends, if the maximum lift exceeds a specified value, the electric motor is reciprocated.

[0006] Japanese Patent Application Publication No. 2019-157679 discloses a valve timing control device, in which a drive-side rotating body that rotates synchronously with the crankshaft and a driven-side rotating body that rotates integrally with the camshaft are arranged on the same axis, and a reduction mechanism is provided. The reduction mechanism has an input gear, an output gear, and a cross-slider coupling, etc., so as to set the relative rotational phase of the drive-side rotating body and the driven-side rotating body by the driving force of an electric actuator. Summary of the Invention

[0007] In a device that uses the driving force of an electric actuator (motor) to set the valve timing via a reduction mechanism, pressure is continuously applied to a specific position of the gear while maintaining the specified valve timing. As a result, wear is easily caused at the contact position of the gear. In order to suppress the above-mentioned wear, Japanese Patent Application Publication No. 2004-332671 and Japanese Patent Application Publication No. 2008-286120 have described control measures that suppress gear wear at a specific position by causing the electric actuator to reciprocate.

[0008] It is believed that the aforementioned wear is not limited to gears. For example, as described in Japanese Patent Application Publication No. 2019-157679, there are also cases where ball wear occurs in ball bearings that support reduction gears.

[0009] That is, since the speed reduction mechanism described in Japanese Patent Application Publication No. 2019-157679 is a structure in which pressure is applied from an eccentric component to make a part of the external teeth of the input gear mesh with a part of the internal teeth of the output gear, there is also concern that excessive radial force may be applied to the bearing, causing ball wear and affecting smooth operation.

[0010] For the reasons mentioned above, people are looking for a valve timing control unit that can control the wear of bearings.

[0011] The valve timing control unit of the present invention is characterized by having a valve timing control mechanism comprising the following components: a drive-side rotating body that rotates synchronously with the crankshaft of an internal combustion engine; a driven-side rotating body that rotates integrally with a camshaft of a valve for opening and closing the combustion chamber of the internal combustion engine, configured to be coaxial with the rotation axis of the drive-side rotating body, and capable of changing the relative rotation phase relative to the drive-side rotating body via a bearing; an electric motor and a reduction gear for setting the relative rotation phase; and a phase sensor unit that detects the relative rotation phase between the drive-side rotating body and the driven-side rotating body as an actual phase centered on the rotation axis. The valve timing control unit includes a control unit that controls the electric motor in a direction that reduces the phase difference between the actual phase detected by the phase sensor unit and a target phase. The control unit includes an oscillation control unit that oscillates the target phase near the target phase while maintaining the target phase and keeping the amount of variation of the actual phase relative to the target phase within a holding region below a set value.

[0012] When an internal combustion engine is running, the force (cam undulation torque) from the camshaft acts on the valve timing control mechanism, and the multiple gears of the reduction gear continuously rotate due to the driving force of the electric motor. Because the bearing rotates, even if a force from the cam is applied, the force is distributed in the circumferential area of ​​the bearing, and the pressure does not strongly act on a specific position in the circumferential direction of the bearing. Conversely, when the actual phase approaches the target phase and the amount of variation in the actual phase decreases, the force from the cam acts on a specific position in the circumferential direction of the bearing. That is, when the difference between the target phase and the actual phase exceeds a set value, due to continuous phase difference convergence control, for example, in the case of rolling bearings, although the rotation of the balls is large and can suppress the undesirable phenomenon of strong forces continuously acting on specific parts of the balls and bearing races, the phase convergence control causes the difference to decrease. For example, the rotation of the balls in the rolling bearing decreases, and the pressure acts locally, resulting in wear.

[0013] For the reasons mentioned above, while maintaining the target phase and keeping the actual phase variation below the set value, phase swing control is performed to make the target phase swing near the target phase, thereby making the bearing rotate actively. This expands the area where the bearing's pressure acts in the circumferential direction and eliminates the undesirable phenomenon of strong forces continuously acting on specific parts of the bearing.

[0014] This constitutes a valve timing control unit that can suppress bearing wear.

[0015] As an additional structure to the above structure, the swing control unit sets a swing target phase that is displaced by an equal amount only to the advance angle side and the lag angle side based on the value of the target phase, and swings the target phase back and forth between the two swing target phases at a set period.

[0016] Therefore, the target phase can be made to swing back and forth at a set period, which can suppress bearing wear while keeping the average value of the swinging target phase at the original target phase. Thus, the average valve timing can be maintained at the original valve timing.

[0017] As an additional structure to the above structure, the phase sensor unit consists of a crankshaft angle sensor for detecting the rotation angle of the crankshaft, a camshaft angle sensor for detecting the rotation angle of the camshaft, and a calculation unit for calculating the actual phase based on the detection signals of the crankshaft angle sensor and the camshaft angle sensor. The absolute value of the difference between the maximum and minimum values ​​of the actual phase calculated by the calculation unit is used as the variation.

[0018] Because the cam undulation torque acts from the camshaft, the driven rotating body increases or decreases its rotational speed at a specified cycle, and the actual phase changes accordingly. Therefore, the actual phase can be calculated by the control unit based on the values ​​detected by the crankshaft angle sensor and the camshaft angle sensor, and the absolute value of the difference between the maximum and minimum values ​​of the calculated actual phase can be set as the variation.

[0019] As an additional structure to the above structure, the swing amount of the target phase in the swing control unit can be set to a value greater than the amount of change in the actual phase in the holding region.

[0020] As a result, the swing amount of the target phase set in the swing control unit becomes greater than the actual phase variation when the actual phase of the valve timing control mechanism is held in the holding region. Therefore, the area where the pressure acts on the bearing and gear can be expanded, effectively eliminating the adverse phenomenon of pressure acting locally on specific parts of the bearing and gear.

[0021] As an additional structure to the above structure, a rotational speed detection unit may be provided to detect the number of revolutions of the crankshaft per unit time. If the number of revolutions detected by the rotational speed detection unit exceeds a set value, control in the oscillation control unit shall be initiated.

[0022] When the valve timing control mechanism rotates at a low speed (revolutions per unit time), a "vibration" phenomenon of actual phase oscillation occurs because the driving and driven rotating bodies naturally oscillate in the direction of rotation (rotation speed increases or decreases). The amplitude of this "vibration" tends to gradually decrease as the crankshaft speed increases. Therefore, when the speed detected by the speed detection unit is low, even without control by the oscillation control unit, the area where pressure acts on the bearings and gears can be expanded, and the undesirable phenomenon of strong forces continuously acting on specific parts of the bearings and gears can be suppressed. However, as the speed increases, it becomes difficult to suppress the undesirable phenomenon.

[0023] For the reasons mentioned above, when the rotational speed exceeds the set value, phase swing control can be performed to expand the area where the pressure acts on the bearing and gear, eliminating the undesirable phenomenon of strong force continuously acting on specific parts of the bearing in the circumferential direction.

[0024] As an additional structure to the above structure, the internal combustion engine includes an intake-side valve timing control mechanism for controlling the opening and closing periods of the intake valve and an exhaust-side valve timing control mechanism for controlling the opening and closing periods of the exhaust valve. The control unit performs a correlation operation, which is associated with the control of the swing control unit to swing the target phase of one of the intake-side valve timing control mechanism and the exhaust-side valve timing control mechanism, so that the target phase of the other party swings in the same phase swing direction.

[0025] Therefore, during phase swing control, since the target phase of the intake-side valve timing control mechanism and the target phase of the exhaust-side valve timing control mechanism swing simultaneously in the same swing direction, the relationship between the intake valve timing and the exhaust valve timing can be maintained. Especially in devices where there is an overlap between the opening and closing periods (valve timing) of the intake-side valve timing control mechanism and the opening and closing periods (valve timing) of the exhaust-side valve timing control mechanism, the length of the overlap area can be maintained, and good intake and exhaust performance can be achieved.

[0026] As an additional structure to the above structure, the internal combustion engine may include an intake-side valve timing control mechanism for controlling the opening and closing periods of the intake valve and an exhaust-side valve timing control mechanism for controlling the opening and closing periods of the exhaust valve. In the timing before the exhaust valve is closed using the exhaust-side valve timing control mechanism, an overlap region for opening the intake valve using the intake-side valve timing control mechanism is set. In a state where the opening and closing periods of either the intake-side valve timing control mechanism or the exhaust-side valve timing control mechanism are shifted in the direction of expanding the overlap region, the target phase of either the intake-side valve timing control mechanism or the exhaust-side valve timing control mechanism is oscillated by the swing control unit.

[0027] Therefore, by shifting the opening and closing times of one of the intake valve timing control mechanism and the exhaust valve timing control mechanism in advance to expand the overlap area, and by swinging the other of the intake valve timing control mechanism and the exhaust valve timing control mechanism in turn, even with a reduced overlap area, the required overlap area for intake and exhaust in the combustion chamber can be ensured without reducing the intake and exhaust performance of the internal combustion engine.

[0028] As an additional structure to the above structure, the internal combustion engine includes an intake-side valve timing control mechanism for controlling the opening and closing period of the intake valve, and an electrically operated regulating valve (throttle) for controlling the amount of intake air supplied to the combustion chamber. In the control unit, when the oscillating control unit is used to control the intake-side valve timing control mechanism, the regulating valve is used to increase the intake air volume in relation to the increase in the amount of change of the intake-side valve timing control mechanism in the advance angle direction.

[0029] Therefore, when performing phase swing control in the intake side valve opening and closing control mechanism, the intake timing of the intake side valve timing control mechanism can be shifted in the advance angle direction to increase the intake volume. Corresponding to the shift in the advance angle direction, the flow rate of the regulating valve can be increased, thereby eliminating the adverse phenomenon of insufficient intake volume in the combustion chamber.

[0030] As an additional structure to the above structure, the internal combustion engine includes a fuel injection device for supplying fuel to the combustion chamber, and the control unit controls the amount of fuel injected by the fuel injection device by adjusting the intake air volume using the regulating valve.

[0031] Therefore, in conjunction with the control of the oscillation control unit, a certain air-fuel ratio can be maintained by increasing or decreasing the fuel injection quantity of the fuel injection device when the intake volume of the intake valve increases or decreases, thereby achieving good combustion. Attached Figure Description

[0032] Figure 1 This diagram shows a cross-section of the engine and the control unit.

[0033] Figure 2 This is a cross-sectional view of the control device during valve opening and closing.

[0034] Figure 3 for Figure 2 Sectional view along line III-III.

[0035] Figure 4 A chart to illustrate the actual phase changes.

[0036] Figure 5 This is a flowchart for phase control.

[0037] Figure 6 This is a flowchart for the swing control.

[0038] Figure 7 A diagram to illustrate valve timing and the overlapping area.

[0039] Figure 8 This is a timing diagram showing the crankshaft speed, the timing of the intake-side variable valve mechanism, the markings, and the opening of the exhaust-side variable valve mechanism and the regulating valve.

[0040] Figure 9 A diagram illustrating valve timing and overlap region in another implementation (a). Detailed Implementation

[0041] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0042] [Basic Structure]

[0043] like Figure 1As shown, the valve timing control unit A is configured to have an intake-side variable valve mechanism VTa (an example of an intake-side valve timing control mechanism) that sets the valve timing (opening and closing period) of the intake valve Va of the engine E, which is an internal combustion engine, and an exhaust-side variable valve mechanism VTb (an example of an exhaust-side valve timing control mechanism) that sets the valve timing (opening and closing period) of the exhaust valve Vb of the engine E, and to have an engine control device 40 (an example of a control unit) that controls the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb.

[0044] Engine E (an example of an internal combustion engine) refers to the device installed in a vehicle to obtain driving force for a car or similar vehicle. Engine control unit 40 controls not only the variable valve mechanism VT (a higher-level concept than the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb), but also the starting and stopping of engine E. Specifically, when engine E is running, and specified conditions are met, engine control unit 40 adjusts the target phase T of the variable valve mechanism VT (refer to...) Figure 4 The oscillation control (reciprocating oscillation towards the advance angle and the lag angle) suppresses wear on the bearings and gears of the variable valve mechanism VT. This control method will be described later.

[0045] [engine]

[0046] like Figure 1 , Figure 2 As shown, engine E is configured as a four-stroke type structure, with a cylinder head 3 connected to the upper part of the cylinder block 2 that supports the crankshaft 1 in a manner that allows the crankshaft 1 to rotate freely. Pistons 4 that can reciprocate freely are housed in multiple cylinder bores formed in the cylinder block 2, and the pistons 4 are connected to the crankshaft 1 by connecting rods 5.

[0047] The cylinder head 3 has an intake valve Va and an exhaust valve Vb. The upper part of the cylinder head 3 has an intake camshaft 7 that controls the intake valve Va and an exhaust camshaft 8 that controls the exhaust valve Vb. In addition, a timing belt 6 is wound around the output pulley 1S across the crankshaft 1 and the respective drive pulleys 21S of the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb.

[0048] The cylinder head 3 is equipped with an injector 9 (an example of a fuel injection device) for injecting fuel into the combustion chamber and a spark plug 10. An intake manifold 11 for supplying air to the combustion chamber through an intake valve Va and an exhaust manifold 12 for discharging combustion gases from the combustion chamber through an exhaust valve Vb are connected to the cylinder head 3.

[0049] Furthermore, an electrically operated regulating valve 13, which regulates the intake air volume via a regulating valve and an electric motor 13a, is located upstream of the intake manifold 11, and a catalyst 14 for purifying exhaust gases is located in the middle of the exhaust manifold 12. The engine E includes a starter motor 15 that drives the crankshaft 1 to rotate during startup (see reference). Figure 2 ).

[0050] (Variable valve mechanism)

[0051] Because the intake-side variable valve mechanism VTa (intake-side valve timing control mechanism) and the exhaust-side variable valve mechanism VTb (exhaust-side valve timing control mechanism) share a common structure, therefore... Figure 2 , Figure 3 Common structures are marked with common symbols, and distinguishable parts are marked with distinguishing symbols.

[0052] like Figure 2 , Figure 3 As shown, in the variable valve mechanism VT, the drive housing 21 (an example of an intake drive-side rotating body / exhaust drive-side rotating body), the internal rotor 22 (an example of an intake driven-side rotating body / exhaust driven-side rotating body), and the rotation axis X of the intake camshaft 7 or the exhaust camshaft 8 are arranged coaxially, and a phase adjustment mechanism G (an example of a reduction gear) is provided to control the relative rotation phase of the motors by the driving force of the phase control motor M (a higher concept of the intake-side phase control motor Ma and the exhaust-side phase control motor Mb), which is an electric motor.

[0053] A drive pulley 21S is formed on the outer periphery of the drive housing 21. The inner rotor 22 is enclosed within the drive housing 21 and is connected and fixed to the intake camshaft 7 or the exhaust camshaft 8 by connecting bolts 23. With this structure, the drive housing 21 is supported on the outer periphery of the inner rotor 22 in a relatively rotatable manner, and the inner rotor 22 rotates integrally with the corresponding camshaft (intake camshaft 7 or exhaust camshaft 8).

[0054] The front plate 24 is secured to the opening of the drive housing 21 by a plurality of fastening bolts 25. Thus, the displacement of the phase adjustment mechanism G and the internal rotor 22 in the direction along the rotation axis X is limited by the front plate 24.

[0055] like Figure 1 , Figure 3As shown, the variable valve mechanism VT rotates as a whole in the drive rotation direction S via the driving force from the timing belt 6. Additionally, the driving force of the phase control motor M is transmitted to the internal rotor 22 via the phase adjustment mechanism G, causing a shift in the relative rotational phase of the internal rotor 22 relative to the drive housing 21. In this shift, the shift direction in the same direction as the drive rotation direction S is called the advance angle direction Sa, and its opposite direction is called the lag angle direction Sb.

[0056] [Variable valve mechanism: phase adjustment mechanism]

[0057] The phase adjustment mechanism G includes a gear ring 26 formed on the inner circumference of the inner rotor 22, coaxial with the rotation axis X; an internal gear 27 coaxial with the eccentric axis Y on the inner circumference side of the inner rotor 22 and rotatably arranged; an eccentric cam body 28 arranged on the inner circumference side of the internal gear 27; a front plate 24; and a connector J. The eccentric axis Y is formed in an orientation parallel to the rotation axis X.

[0058] The gear ring 26 has multiple internal tooth portions 26T, and the internal gear 27 has multiple external tooth portions 27T. The internal gear 27 is positioned on the eccentric cam surface 28A along the outer periphery of the eccentric cam body 28, and is arranged coaxially with the eccentric shaft Y. A portion of the external tooth portions 27T meshes with the internal tooth portions 26T of the gear ring 26. The phase adjustment mechanism G is configured as an internal meshing planetary gear reducer where the number of teeth on the external tooth portions 27T of the internal gear 27 is only one less than the number of teeth on the internal tooth portions 26T of the gear ring 26.

[0059] The connector J includes a connector component 33 formed by stamping steel sheet, and is configured as a cross-slider coupling type, in which the outer periphery of the connector component 33 engages with the drive housing 21, and the engaging protrusion 27U of the internal gear 27 engages with the inner periphery of the connector component 33. Thus, the connector J maintains the eccentric positional relationship of the internal gear 27 relative to the drive housing 21, and realizes the action of rotating the internal gear 27 and the drive housing 21 together.

[0060] The eccentric cam body 28 is generally cylindrical, and a pair of engaging grooves 28B are formed on its inner circumference in an orientation parallel to the rotation axis X. The eccentric cam body 28 is supported relative to the front plate 24 by a first bearing 31 (an example of a bearing) that functions as a rolling bearing, allowing it to rotate coaxially with the rotation axis X. Furthermore, an eccentric cam surface 28A is formed on the outer circumference of a portion closer to the intake camshaft 7 than the support position of the first bearing 31.

[0061] The eccentric cam surface 28A is formed as a circle (with a circular cross-sectional shape) centered on an eccentric axis Y parallel to the rotation axis X. The internal gear 27 is rotatably supported relative to the outer periphery of the eccentric cam surface 28A by a second bearing 32 (an example of a bearing) that functions as a rolling bearing. Furthermore, a spring body 29 is embedded in a recess formed in the eccentric cam surface 28A, and a force is applied to the internal gear 27 via the second bearing 32. Based on this structure, a portion of the outer teeth 27T of the internal gear 27 meshes with a portion of the inner teeth 26T of the gear ring 26, and the meshing state is maintained by the force of the spring body 29.

[0062] The phase-controlled motor M is supported by the engine E, and the engagement pin 34 formed on the output shaft Ms is embedded in the engagement groove 28B on the inner circumference of the eccentric cam body 28. Although not shown in detail, the phase-controlled motor M has a rotor with permanent magnets, a stator with multiple excitation coils arranged around the rotor, and an output shaft Ms that transmits the rotation of the rotor, thus forming a brushless structure with a structure common to three-phase motors.

[0063] In the aforementioned variable valve mechanism VT, when the engine E is running, the output shaft Ms is driven to rotate in the drive rotation direction S at the same speed as the camshaft, thereby maintaining the relative rotational phase of the variable valve mechanism VT. Furthermore, when the relative rotational phase shifts in the advance angle direction Sa, the rotational speed of the output shaft Ms is reduced; when the relative rotational phase shifts in the lag angle direction Sb, the rotational speed of the output shaft Ms is increased.

[0064] To explain the state where the engine E is stopped, in the phase adjustment mechanism G, because the outer tooth 27T of the internal gear 27 meshes with the inner tooth 26T of the gear ring 26, when the eccentric cam body 28 rotates around the rotation axis X along with the rotation of the output shaft Ms due to the drive of the phase control motor M, the internal gear 27 revolves around the rotation axis X and rotates on its own axis Y.

[0065] Furthermore, with each revolution of the internal gear 27 around the rotation axis X, the internal gear 27 rotates relative to the gear ring 26 at an angle corresponding to the difference in the number of teeth between the internal gear 27 and the gear ring 26, thereby achieving a significant speed reduction. As a result, by controlling the rotational speed of the phase-controlled motor M, the drive housing 21, which rotates integrally with the internal gear 27 via the connector J, rotates relative to the camshaft connected to the gear ring 26 via the connecting bolt 23, thereby achieving valve timing adjustment.

[0066] [Control Structure]

[0067] like Figure 1 , Figure 2 As shown, the engine E is equipped with a starter motor 15 that drives the crankshaft 1 to rotate, a crankshaft angle sensor 16 that can detect the rotation angle is located near the crankshaft 1 (which also functions as a speed detection unit), an intake camshaft angle sensor 17 that can detect the rotation angle of the intake camshaft 7 is located near the intake camshaft 7, and an exhaust camshaft angle sensor 18 that can detect the rotation angle of the exhaust camshaft 8 is located near the exhaust camshaft 8.

[0068] The crankshaft angle sensor 16, the intake-side camshaft angle sensor 17, and the exhaust-side camshaft angle sensor 18 are configured as a pickup-type structure that intermittently outputs pulse signals as the crankshaft 1 rotates. The crankshaft angle sensor 16 counts pulse signals based on the rotation reference of the crankshaft 1 as the crankshaft 1 rotates, thereby obtaining the rotation angle based on the rotation reference. Similarly, the intake-side camshaft angle sensor 17 and the exhaust-side camshaft angle sensor 18 are configured to count pulse signals based on the rotation reference of the intake camshaft 7 as the intake-side camshaft 7 rotates, thereby allowing the rotation angle based on the rotation reference to be obtained in the engine control unit 40.

[0069] Based on the above structure, for example, by pre-storing Figure 3 The crankshaft angle sensor 16, with the drive housing 21 and internal rotor 22 in a specified reference phase (e.g., intermediate phase), and the count value of the intake-side camshaft angle sensor 17 or the exhaust-side camshaft angle sensor 18, can be compared to obtain the relative rotation phase, regardless of whether the relative rotation phase shifts from the reference phase to either the advance angle side (advance angle direction Sa) or the lag angle side (lag angle direction Sb).

[0070] Thus, the crankshaft angle sensor 16 and the intake-side camshaft angle sensor 17 constitute the intake-side phase sensor unit Is, and the crankshaft angle sensor 16 and the exhaust-side camshaft angle sensor 18 constitute the exhaust-side phase sensor unit Es.

[0071] like Figure 1 As shown, the engine control unit 40 inputs detection signals from the crankshaft angle sensor 16, the intake-side camshaft angle sensor 17, and the exhaust-side camshaft angle sensor 18, while simultaneously inputting detection signals from the main switch 45 and the accelerator pedal sensor 47. The engine control unit 40 outputs control signals to the main switch 15, the phase control motors M (intake-side phase control motor Ma and exhaust-side phase control motor Mb), the combustion management unit 19, and the regulating valve control motor 13a.

[0072] In addition, the engine control unit 40 includes an engine control unit 41, a phase control unit 42 (an example of a calculation unit), a yaw control unit 43, and a compensation control unit 44. Although they are composed of software, some of them can be composed of only hardware, or they can be composed of a combination of hardware and software.

[0073] The engine control unit 41 performs control from the start to the stop of the engine E. The phase control unit 42 controls the valve timing (opening and closing periods) of the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb when the engine E starts, runs, and stops. The oscillation control unit 43 performs... Figure 6 The oscillation control shown in the flowchart suppresses wear on bearings (first bearing 31 and second bearing 32) and gears (ring gear 26 and internal gear 27). The compensation control unit 44 compensates for the intake volume, etc., when the oscillation control unit 43 is in operation.

[0074] In the aforementioned control structure, the main switch 45 is located on the dashboard of the driver's seat, allowing the engine E to be started and stopped manually. The accelerator pedal sensor 47 acquires the amount of pressure applied to the accelerator pedal (not shown). The combustion management unit 19 manages the operation of the pumps supplying fuel to the injectors 9 and controls the ignition circuit supplying electricity to the spark plugs 10, managing the ignition sequence and ignition timing.

[0075] [Control Method]

[0076] The intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb have an eccentric cam body 28, and the force of the spring body 29 acting from the eccentric cam body 28 causes a portion of the inner tooth portion 26T of the gear ring 26 to mesh with a portion of the outer tooth portion 27T of the internal gear 27.

[0077] Based on the above structure, the gear ring 26 and the internal gear 27 are kept in an eccentric positional relationship, and while a strong force is applied to the first bearing 31 and the second bearing 32, which allow for relative rotational phase displacement, a strong force is also applied to the contact surface of the internal tooth portion 26T and the external tooth portion 27T.

[0078] In particular, since the first bearing 31 and the second bearing 32 have a structure in which multiple balls are arranged between the inner ring and the outer ring, it is believed that when the pressure of the cam undulation torque is applied to the first bearing 31 and the second bearing 32 under the condition of engine E running, the balls press against the inner ring and the outer ring in the radial direction, resulting in ball wear.

[0079] Similarly, it is believed that wear on the contact surface is caused by the pressure resulting from the cam undulation torque acting on the contact surface of the internal gear 26T and the external gear 27T when the engine E is running.

[0080] To control the aforementioned wear, the engine control unit 40 performs the following... Figure 5 The flowchart above illustrates the control method of the intake-side variable valve mechanism VTa, which controls the valve timing (opening and closing period) of the intake valve Va when the engine E is running.

[0081] That is, the target phase T is set based on information such as the amount of accelerator pedal depressed detected by the accelerator pedal sensor 47 or the number of revolutions counted by the crankshaft angle sensor 16 (the number of revolutions of crankshaft 1 per unit time), and the actual phase P of the intake-side variable valve mechanism VTa is obtained based on the count value of the crankshaft angle sensor 16 and the count value of the intake-side camshaft angle sensor 17 (step #02).

[0082] The phase control unit 42 performs steps #01 and #02 as described above, and determines whether the phase difference between the target phase T and the actual phase P obtained by the above method is less than the set value (e.g., 1.0CA to 1.2CA) or greater than the set value (step #03). The phase control unit 42 performs step #03 as described above, and if it determines that the phase difference is less than the set value (no in step #03), it performs phase difference convergence control (control that causes the intake side phase motor Ma to operate in the direction of reducing the phase difference) (step #04), and then exits phase control and returns. The phase control unit 42 performs step #04 as described above.

[0083] In particular, such as Figure 4 As shown, in phase difference convergence control, a holding region K is set across the advance angle side and the lag angle side, with the target phase T as the reference. Phase convergence control ends (stops) when the actual phase P reaches a state contained within the holding region K (control in step #04). When the holding region K is set in a relatively narrow area and phase convergence control is ended, the actual phase P, while contained within the holding region K, alternates between the advance angle side and the lag angle side due to the camshaft undulation torque (increasing or decreasing the rotational speed of the intake camshaft 7). It should be noted that in this figure, the initial region Q shows the state where the target phase T and the actual phase P have converged.

[0084] If, in step #03, it is determined that the phase difference is insufficient to the set value (Yes in step #03), when the duration of this state is greater than or equal to the set time (e.g., approximately 0.1 seconds), the number of revolutions per unit time of crankshaft 1 is acquired, and then it is determined whether the number of revolutions acquired in the above manner is greater than or equal to the set number of revolutions (steps #06 and #07). Furthermore, if, in the case of a phase difference insufficient to the set value (Yes in step #03), the duration of this state is less than the set time (No in step #05), the phase control is exited and the process returns.

[0085] Additionally, when it is determined in step #07 that the rotation speed is above the set rotation speed (Yes in step #07), swing control is implemented (step #100). If the rotation speed is below the set rotation speed (No in step #07), control is exited and the process returns. It should be noted that #05 to #07 are processes used to determine whether swing control needs to be entered, and are implemented by the swing control unit 43.

[0086] Thus, when the phase difference is less than the set value (convergence state) and the duration of this state exceeds the set time, and the crankshaft 1 rotates at a speed greater than the set speed, oscillation control is implemented (step #100).

[0087] The swing control (step #100) is set as a subroutine and is basically executed by the swing control unit 43. That is, as Figure 6 As shown in the flowchart, the target phase T (refer to) of the intake and exhaust sides is obtained. Figure 4 (Only one of the intake side and exhaust side is shown in this figure), and the two target phases T obtained are set as the reference and the target phases Tx and Ty are deviated by an equal amount (steps #102 and #103).

[0088] In addition, Figure 4 In the timing diagram, the target phase T is set as the reference, and the advance angle and lag angle are set in the direction of advance angle and lag angle (in Figure 4 The target phases Tx and Ty, which are oscillating with equal amplitudes in the vertical direction, are defined as follows: The oscillation directions of the aforementioned target phases Tx and Ty (in the vertical direction) are... Figure 4 The interval (in the vertical direction) is the swing amount of the target phase T. The swing amount is set to be greater than the change in the actual phase P caused by the action of the cam undulation torque.

[0089] In the intake camshaft 7, due to the cam undulation torque, the rotational speed alternates between the advance angle and the lag angle directions, thus the revolutions increase and decrease in a relatively short cycle. Therefore, as... Figure 4 As shown by the solid line in the timing diagram, the actual phase P varies in a wave-like manner with a specified amplitude, and the amplitude of the variation constitutes the amount of variation.

[0090] Because the actual phase P variation is small, if the state in the holding region K continues, the pressure exerted locally on the balls of the first bearing 31 and the second bearing 32 may cause ball wear. Therefore, to suppress such wear, it is best to rotate the balls by a specified angle (e.g., 45 degrees or 90 degrees) or more using oscillation control. For the above reasons, to enable the balls to rotate by a specified angle or more, target oscillation phases Tx and Ty are set, and the values ​​of the target oscillation phases Tx and Ty are made greater than the amount of variation in the actual phase P within the holding region K.

[0091] After setting the target swing phases Tx and Ty in this way, the swing action (step #103) is performed. It should be noted that the phase difference convergence control performed in step #103 is only a routine procedure for using phase convergence control to make the drive housing 21 and the internal rotor 22 swing, and is different from the control for converging the actual phase P to the target phase T (holding region K).

[0092] For example, when the swing target phase Tx is set to the advance angle side based on the target phase T, and the swing target phase Ty is set to the lag angle side based on the target phase T, during the swing action (step #103), the two swing target phases Tx and Ty are switched with a set period R, and the regulating valve 13 is controlled according to the change in intake volume accompanying the above control by performing phase difference convergence control. The control of the regulating valve 13 is implemented by the compensation control unit 44.

[0093] In the control of step #103 above, the two swing target phases Tx and Ty, set on the advance angle side (advance angle direction Sa) and the lag angle side (lag angle direction Sb), are switched with equal set periods R. Phase difference convergence control is performed through the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb to track... Figure 4 The timing diagram uses dashed lines to represent peaks and troughs, indicating a pattern of equal reciprocating motion. Furthermore, after performing the control in step #103 above, the process returns... Figure 5 Phase control. The target phases Tx and Ty, and the set period R can be set according to the engine status (rpm, load).

[0094] In particular, in the aforementioned swinging motion, such as Figure 7 As shown, the exhaust valve timing Ex of the exhaust-side variable valve mechanism VTb and the intake valve timing In of the intake-side variable valve mechanism VTa reciprocate with the same amount of timing in the same direction as the crankshaft rotation angle.

[0095] Thus, by performing a oscillating motion, the drive housing 21 and the internal rotor 22 oscillate relative to each other, which can suppress the undesirable phenomenon of increased wear caused by the balls of the first bearing 31 and the second bearing 32 pressing against the inner or outer ring, and the undesirable phenomenon of increased wear at the pressing surfaces of the inner teeth 26T of the gear ring 26 and the outer teeth 27T of the internal gear 27 pressing against each other. Furthermore, as... Figure 7 As shown, by performing a swinging motion, the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb are associated and move in the same direction (associated motion), which does not change the length of the overlapping area W, nor does it change the intake volume.

[0096] In addition, Figure 7 In the diagram, the initial exhaust valve timing Ex of the exhaust-side variable valve mechanism VTb is represented by a solid line, and the intake valve timing In of the intake-side variable valve mechanism VTa is represented by a dashed line. Furthermore, relative timings are set such that the exhaust valve Vb enters the closed state at the valve closing timing EVC of the exhaust valve timing Ex, and prior to this, the intake valve Va enters the open state at the valve opening timing IVO of the intake valve timing In. Thus, the region between the valve closing timing EVC and the valve opening timing IVO constitutes an overlapping region W.

[0097] [Time Sequence Diagram]

[0098] In addition, Figure 8 The timing diagram shows the crankshaft 1 revolutions, the valve timing of the intake-side variable valve mechanism VTa, and the flag when oscillation control is implemented during the process of starting and stopping the engine E.

[0099] It should be noted that, in addition to the above, the figure shows the valve timing of the exhaust-side variable valve mechanism VTb and the opening of the regulating valve 13, but these will be described in other embodiments (b).

[0100] like Figure 8 As shown in the timing diagram, when engine E starts, the valve timing of the intake-side variable valve mechanism VTa is at the maximum advance angle phase, and after engine E starts, it changes to the lag angle phase. In addition, immediately after engine E starts, catalyst preheating is performed at a high crankshaft speed.

[0101] When the valve timing of the intake-side variable valve mechanism VTa is set to the lag angle side, a specified target phase T is set (refer to...). Figure 4 By controlling the intake-side phase control motor Ma, the actual phase P is converged to the target phase T, thus fulfilling the conditions of steps #03 and #05 above. By making these conditions true, the flag switches from off to on, initiating swing control. Figure 5 Step #100).

[0102] Although this timing diagram only shows the swing control of the intake-side variable valve mechanism VTa, it can be synchronized with the intake-side variable valve mechanism VTa and swing control can be performed in the same direction and at the same timing to make the actual phase P of the exhaust-side variable valve mechanism VTb swing. Through the above swing control, the overlapping area W is kept constant.

[0103] Furthermore, when the phase difference between the target phase T and the actual phase P is above a set value, and when the crankshaft 1 rotates at a low speed, such as when the engine E is idling, no swing control is performed. Instead, the phase difference between the target phase T and the actual phase P is reduced to below the set value (step #03). When the crankshaft 1 rotates at a high speed, such as when a car is driving (step #05), the flags in the three regions of the first region U1, the second region U2, and the third region U3, where the conditions are met, are turned on, and swing control is performed in these regions.

[0104] [Effects of the Implementation Method]

[0105] When the difference between the target phase T and the actual phase P exceeds a set value, phase difference convergence control (control that moves the phase control motor M in the direction of reducing the phase difference) is performed. The bearing balls rotate between the inner and outer rings, thus suppressing the undesirable phenomenon of these balls pressing against specific positions and preventing wear. When phase control is performed for the same reason, because the contact position of the internal gear 26T and the external gear 27T shifts, the undesirable phenomenon of internal gear 26T pressing against external gear 27T and causing wear is prevented.

[0106] Furthermore, when the variable valve mechanism VT (intake-side variable valve mechanism VTa or exhaust-side variable valve mechanism VTb) rotates at a lower speed, the relative speeds of the drive housing 21 and the internal rotor 22 will naturally increase or decrease relative to each other, resulting in a "vibration" phenomenon where the actual phase P oscillates. The amplitude (rotation angle difference) of the aforementioned "vibration" tends to gradually decrease as the speed of the variable valve mechanism VT increases. Therefore, when the speed detected by the crankshaft angle sensor 16 (speed detection unit) is low, even without oscillation control, the area where pressure acts on the bearing (first bearing 31 or second bearing 32) and gear (gear ring 26 and internal gear 27) will expand, which can suppress the undesirable phenomenon of strong force continuously acting on specific parts of the bearing and gear along the pressing direction.

[0107] Conversely, as the rotational speed of the variable valve mechanism VT increases, the amplitude of the "vibration" decreases, and the pressure acting on specific locations of the bearings and gears increases, causing wear. For the above reasons, phase convergence control is used to achieve a state where the drive housing 21 and the internal rotor 22 hardly rotate relative to each other, and when the rotational speed detected by the crankshaft angle sensor 16 reaches or exceeds a set number. This results in oscillation control (step #100) to oscillate the target phase T. By performing this control, the undesirable phenomenon of strong forces continuously acting on specific parts of the bearings and gears along the pressing direction is suppressed, thereby eliminating wear.

[0108] In addition, when performing oscillation control, since the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb oscillate synchronously in the same direction with equal amounts, not only can the wear of bearings and gears be suppressed, but the length of the overlapping area W can also be maintained without changing the intake volume, so the intake and exhaust performance will not change.

[0109] [Other Implementation Methods]

[0110] In addition to the above-described embodiments, the present invention may adopt the structure shown below (the parts having the same function as the above-described embodiments are marked with the same numbers and symbols as the above-described embodiments).

[0111] (a) When only one of the exhaust-side variable valve mechanism VTb and the intake-side variable valve mechanism VTa is oscillating controlled, in order to keep the overlap length of the overlapping area W above the set value, relevant control is performed in advance so that the timing of the variable valve mechanism VT, which is not oscillating controlled, moves in the direction of expanding the overlap length of the overlapping area W.

[0112] In the other embodiment (a) described above, a control method is shown, which, as an exhaust-side variable valve mechanism VTb, uses, for example, a hydraulically controlled exhaust timing control mechanism to perform only the oscillation control of the intake-side variable valve mechanism VTa. Specifically, as Figure 9 As shown, the initial exhaust valve timing Ex of the exhaust-side variable valve mechanism VTb is represented by a solid line, and the intake valve timing In of the intake-side variable valve mechanism VTa before swing control is performed by a dashed line. Furthermore, the area where the exhaust valve timing Ex and the intake valve timing In overlap is represented as the initial overlap area Wp (an example of the overlap area W).

[0113] Therefore, when performing oscillation control of the intake-side variable valve mechanism VTa under the condition of setting the timing of each valve (in Figure 9When the timing of the exhaust valve swings in the advance angle direction Sa and the lag angle direction Sb, in order to ensure the initial overlap area Wp, a control method is set, that is, the timing of the exhaust valve Ex is changed only from the initial timing to the lag angle direction Sb by the preset timing Z marked with a double-dotted line in advance, so as to pre-set the expanded overlap area Ws (an example of the overlap area W).

[0114] Because of the aforementioned control, when the intake valve timing is shifted in the lag angle direction Sb by the swing control, combustion chamber gas emission and intake operations can be easily performed in the overlap region W. Therefore, the timing Z of the exhaust valve timing Ex can be preset by shifting it from the initial timing to the lag angle direction Sb through the control compensation control unit 44. Since the preset timing Z is set to be greater than the swing target phase Ty when the intake-side variable valve mechanism VTa is swing controlled (when Ty is set in the lag angle direction Sb), the initial overlap region Wp can be ensured even if the intake-side variable valve mechanism VTa reaches the swing target phase Ty.

[0115] Furthermore, when only the target phase T of the exhaust-side variable valve mechanism VTb is oscillating, the other implementation method (a) described above can be achieved by controlling the valve timing of the intake-side variable valve mechanism VTa in advance, so that it only shifts to the advance angle side to set the timing Z. Thus, the variable valve mechanism VT, which shifts the valve timing in advance, can use a structure that controls the valve timing hydraulically.

[0116] (b) such as Figure 8 As shown in the timing diagram, when the intake-side variable valve mechanism VTa is oscillating, the valve timing of the exhaust-side variable valve mechanism VTb is set by synchronizing the timing with the above-mentioned oscillation control, and the increase or decrease of the intake volume is controlled by controlling the regulating valve 13.

[0117] In this diagram, oscillation control is implemented in three regions: region 1 U1, region 2 U2, and region 3 U3. To increase the intake volume, the displacement of the advance angle direction of the variable valve mechanism VTa on the intake side is increased in the oscillation control of region 1 U1 and region 2 U2, while the displacement in the advance angle direction is reduced in region 3 U3 to decrease the intake volume.

[0118] In order to effectively increase or decrease the intake volume as described above, as shown by the dashed line, in the swing control of the first region U1 and the second region U2, while the exhaust timing of the exhaust-side variable valve mechanism VTb is shifted in the direction of the lag angle, the intake volume of the regulating valve 13, as shown by the dashed line in the regulating valve 13, is increased.

[0119] Conversely, as shown by the dashed line, in the swing control of the third region U3, while shifting the exhaust timing of the exhaust-side variable valve mechanism VTb to the advance angle side, the intake volume of the regulating valve 13, as shown by the dashed line in the regulating valve 13, is reduced.

[0120] In another embodiment (b), the control of the exhaust-side variable valve mechanism VTb and the regulating valve 13 is achieved by the compensation control unit 44. When performing the swing control of the intake-side variable valve mechanism VTa, the change in intake volume can be suppressed by the above control. In addition, in the above other embodiment (b), since it is not necessary to use the exhaust-side variable valve mechanism VTb to operate at high speed, a structure that controls the timing of the exhaust valve by hydraulic means can be used.

[0121] (c) As described in the other embodiments (b) above, the fuel supply to the injector 9 can be increased by increasing the displacement of the intake-side variable valve mechanism VTa in the advance angle direction and causing the exhaust-side variable valve mechanism VTb to be displaced in the lag angle direction. This control method can maintain a constant air-fuel ratio and ensure proper combustion in the combustion chamber.

Claims

1. A valve timing control unit, wherein: the valve timing control unit is provided with a valve timing control mechanism, which is formed of: a drive-side rotary body that rotates in synchronization with a crankshaft of an internal combustion engine; a driven-side rotary body that rotates in conjunction with a camshaft of a valve that opens and closes a combustion chamber of the internal combustion engine, is disposed coaxially with a rotational axis center of the drive-side rotary body, and can change a relative rotational phase with respect to the drive-side rotary body via a bearing; an electric motor and a reduction gear for setting the relative rotational phase; and a phase sensor unit that detects the relative rotational phase of the drive-side rotary body and the driven-side rotary body as an actual phase centered on the rotational axis center, the valve timing control unit is provided with a control section that controls the electric motor in a direction in which a phase difference between the actual phase detected by the phase sensor unit and a target phase is reduced, the control section is provided with a swing control section that swings the target phase in the vicinity of the target phase in a case where the target phase is maintained and an amount of variation of the actual phase is kept at a value that is less than a set value in a holding region.

2. The valve timing control unit according to claim 1, wherein: the swing control section sets swing target phases that are displaced by an equal amount to an advance angle side and a retard angle side with the value of the target phase as a reference, and swings the target phase to and fro between the two swing target phases at a set period.

3. The valve timing control unit according to claim 1 or 2, wherein: the phase sensor unit is constituted by a crankshaft rotation angle sensor that detects a rotation angle of the crankshaft, a camshaft angle sensor that detects a rotation angle of the camshaft, and a calculation section that calculates the actual phase from detection signals of the crankshaft rotation angle sensor and the camshaft angle sensor, and an absolute value of a difference between a maximum value and a minimum value of the actual phase calculated by the calculation section is set as the amount of variation.

4. The valve timing control unit according to claim 1, wherein: an amount of swing of the target phase in the swing control section is set to a value that is greater than an amount of variation of the actual phase in the holding region.

5. The valve timing control unit according to any one of claims 1 to 3, wherein: the valve timing control unit is provided with a rotation number detection section that detects a rotation number per unit time of the crankshaft, and control in the swing control section is started in a case where the rotation number detected by the rotation number detection section exceeds a set value.

6. The valve timing control unit according to any one of claims 1 to 5, wherein: the internal combustion engine is provided with an intake-side valve timing control mechanism that controls an opening and closing period of an intake valve and an exhaust-side valve timing control mechanism that controls an opening and closing period of an exhaust valve as the valve timing control mechanism. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The control section performs a correlation operation that, in association with the control of the target phase of one of the intake-side valve timing control mechanism and the exhaust-side valve timing control mechanism being swung by the swing control section, swings the target phase of the other in the same phase swing direction.

7. The valve timing control unit according to any one of claims 1 to 5, wherein the internal combustion engine is provided with an intake-side valve timing control mechanism that controls the opening and closing period of an intake valve and an exhaust-side valve timing control mechanism that controls the opening and closing period of an exhaust valve as the valve timing control mechanisms, an overlapping region in which the intake valve is opened by the intake-side valve timing control mechanism is set to overlap a period in which the exhaust valve is closed by the exhaust-side valve timing control mechanism, in a state in which the opening and closing period of either one of the intake-side valve timing control mechanism and the exhaust-side valve timing control mechanism is displaced in a direction in which the overlapping region is enlarged, the target phase of the other is swung by the swing control section.

8. The valve timing control unit according to any one of claims 1 to 5, wherein the internal combustion engine is provided with an intake-side valve timing control mechanism that controls the opening and closing period of an intake valve as the valve timing control mechanism and an electrically driven type regulating valve that controls the amount of intake air supplied to a combustion chamber, in the control section, in association with an increase in the amount of variation of the intake-side valve timing control mechanism in the advance angle direction when control by the swing control section is performed in the intake-side valve timing control mechanism, an increase in the amount of intake air by the regulating valve is sought.

9. The valve timing control unit according to claim 8, wherein the internal combustion engine is provided with a fuel injection device that supplies fuel to the combustion chamber, the control section controls the amount of injection of fuel by the fuel injection device in correspondence with an increase or decrease in the amount of intake air by the regulating valve.

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