Valve timing control unit

Abstract

To constitute a valve opening / closing timing control unit which can suppress the wear of a bearing.SOLUTION: A valve opening / closing timing control unit comprises a valve opening / closing timing control mechanism VT which is composed of: a drive-side rotating body; a driven-side rotating body; an electric motor M and a reduction gear for setting relative rotation phases of the rotating bodies; and a phase sensor for detecting actual phases of the drive-side rotating body and the driven-side rotating body. The valve opening / closing timing control unit also comprises a control part 40 for controlling the electric motor M in a direction in which a phase difference between the actual phases and a target phase becomes small, and the control part 40 comprises an oscillation control part 43 for oscillating the target phase in the vicinity of the held actual phases when the target phase is maintained at a constant value, and held in a holding region in which a variation amount of the actual phases reaches a value smaller than a set value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a valve timing control unit. [Background technology]

[0002] In a four-stroke internal combustion engine, variable valve operating devices such as those shown in the following Patent Documents 1 to 3 are known for adjusting the opening and closing timing of the intake valve or exhaust valve.

[0003] Patent Document 1 discloses a variable valve train in which the valve lift characteristics are determined by the rotational position of a control shaft equipped with an eccentric cam in order to simultaneously and continuously control the lift amount and operating angle (lift characteristics) of the intake valve. In this system, the control shaft is driven by an actuator linked to a worm gear mechanism to set the lift characteristics.

[0004] In particular, Patent Document 1 describes controlling the actuator so that the control shaft is forcibly reciprocated with a small amplitude when the target rotational position of the control shaft is maintained at a constant value for a predetermined period of time.

[0005] Patent Document 2 also describes a variable valve mechanism that changes the maximum lift of the intake valve by linearly operating a planetary shaft that is threaded onto a nut by rotating the nut with an electric motor. Patent Document 2 also describes a control mode that moves the electric motor back and forth if the maximum lift exceeds a predetermined value when the change in the maximum lift is completed.

[0006] Patent Document 3 discloses a valve timing control device in which a drive-side rotor that rotates synchronously with a crankshaft and a driven-side rotor that rotates integrally with a camshaft are arranged on the same axis, and the relative rotational phase between these rotors is set by the driving force of an electric actuator, and the device is equipped with a reduction mechanism having an input gear, an output gear, and an Oldham coupling or the like. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-332671 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-286120 [Patent Document 3] Japanese Patent Application Publication No. 2019-157679 Summary of the Invention [Problem to be solved by the invention]

[0008] In systems where the valve timing is set via a reduction mechanism using the driving force of an electric actuator (electric motor), pressure is continuously applied to a specific position of the gear while maintaining the specified valve timing, which can easily lead to wear at the contact point of the gear.To suppress such wear, Patent Documents 1 and 2 describe a control method in which the electric actuator is operated in a reciprocating manner to suppress wear of the gear at a specific position.

[0009] Such wear is not limited to gears, and it has been thought that it may also affect ball bearings that support reduction gears, causing wear to the balls, as described in Patent Document 3, for example.

[0010] In other words, the reduction mechanism described in Patent Document 3 is configured to apply pressure from an eccentric member so that part of the external teeth of the input gear meshes with part of the internally toothed output gear of the output gear, and there was concern that excessive radial force would act on the bearing, causing wear on the balls and impairing smooth operation.

[0011] For these reasons, there is a demand for a valve timing control unit that can suppress bearing wear. [Means for solving the problem]

[0012] A characteristic configuration of the valve timing control unit according to the present invention includes a valve timing control mechanism including a drive-side rotor that rotates synchronously with a crankshaft of an internal combustion engine, a driven-side rotor that rotates integrally with a camshaft that opens and closes valves in a combustion chamber of the internal combustion engine, is coaxial with the rotational axis of the drive-side rotor, and is arranged so that its relative rotational phase with respect to the drive-side rotor can be changed via a bearing, an electric motor for setting the relative rotational phase, a reduction gear, and a phase sensor that detects the relative rotational phase between the drive-side rotor and the driven-side rotor as an actual phase centered on the rotational axis, and a control unit that controls the electric motor in a direction to reduce a phase difference between the actual phase detected by the phase sensor and a target phase, and a holding region is formed on both the advance side and the retard side based on the target phase, and the control unit includes an oscillation control unit that oscillates the target phase near the target phase when the target phase is maintained and a fluctuation amount of the actual phase is held in the holding region. A rotation speed detection unit is provided for detecting the rotation speed of the crankshaft per unit time, and when the rotation speed detected by the rotation speed detection unit exceeds a set value, control by the fluctuation control unit is started. The point is that

[0013] When the internal combustion engine is running, a force (cam fluctuation torque) from the cam on the camshaft acts on the valve timing control mechanism. When the driving force of the electric motor continues to rotate the multiple gears of the reduction gear, the bearing rotates. Therefore, even if a force from the cam acts, this force is dispersed over a circumferential area of ​​the bearing, and no strong pressure is applied to a specific location on the bearing. In contrast, when the actual phase approaches the target phase and the amount of fluctuation in the actual phase decreases, the force from the cam acts on a specific location on the bearing. In other words, when the deviation between the target phase and the actual phase exceeds a set value, the phase difference convergence control continues. For example, in the case of a rolling bearing, the ball rotation rate is relatively large, which can prevent the inconvenience of strong force continuously acting on specific parts of the ball or race. However, when the deviation is reduced by the phase difference convergence control, for example, the ball rotation rate of a rolling bearing decreases, resulting in localized pressure and wear.

[0014] For this reason, when the target phase is maintained and the amount of fluctuation in the actual phase is kept below a set value, phase fluctuation control is performed to fluctuate the target phase near the target phase, thereby actively rotating the bearing, expanding the area in which pressure acts circumferentially around the bearing and eliminating the inconvenience of strong force continuously acting on specific parts of the bearing. Furthermore, when the valve timing control mechanism rotates at a relatively low rotational speed (number of rotations per unit time), the driving rotor and the driven rotor naturally fluctuate in the rotational direction (increase or decrease in rotational speed), causing fluctuations in the actual phase. The amplitude of this fluctuation tends to decrease as the rotational speed of the crankshaft increases. Therefore, when the rotational speed detected by the rotational speed detection unit is low, the area where pressure acts on the bearings and gears can be expanded without control by the fluctuation control unit, thereby preventing the problem of strong force continuously acting on specific parts of the bearings and gears. However, as the rotational speed increases, this problem becomes difficult to prevent. For this reason, by performing phase fluctuation control when the rotational speed exceeds a set value, the area where pressure acts on the bearings and gears can be expanded, thereby preventing the problem of strong force continuously acting on specific parts around the bearings. Therefore, a valve timing control unit capable of suppressing bearing wear is configured.

[0015] In addition to the above configuration, the oscillation control unit may set an oscillation target phase that is displaced by an equal amount on the advance side and the retard side based on the value of the target phase, and oscillate the target phase back and forth between the two oscillation target phases at a set period.

[0016] This makes it possible to fluctuate the target phase back and forth at a set period, suppressing bearing wear and maintaining the average value of the fluctuating target phase at the original target phase, thereby maintaining the average valve timing at the original valve timing.

[0017] In addition to the above configuration, the phase sensor may include a crank 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 unit that determines the actual phase from detection signals of the crank angle sensor and the camshaft angle sensor, and the amount of fluctuation may be an absolute value of a difference between a maximum value and a minimum value of the actual phase determined by the calculation unit.

[0018] The rotational speed of the driven rotor increases or decreases periodically due to the cam fluctuation torque acting from the camshaft, and the actual phase fluctuates accordingly. Therefore, the actual phase is calculated by the control unit based on the detection values ​​of the crank 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 used as the fluctuation amount.

[0019] In addition to the above configuration, the fluctuation amount of the target phase in the fluctuation control section may be set to a value larger than the fluctuation amount by which the actual phase fluctuates in the holding region.

[0020] As a result, the amount of fluctuation of the target phase set in the fluctuation control unit becomes larger than the amount of fluctuation of the actual phase when the actual phase of the valve timing control mechanism is held in the holding region, thereby expanding the region in which pressure acts on the bearings and gears, and reliably eliminating the inconvenience of pressure acting locally on specific parts of the bearings and gears.

[0024] In addition to the above configuration, the internal combustion engine may be provided with, as the valve timing control mechanism, an intake side valve timing control mechanism that controls the opening and closing timing of the intake valve, and an exhaust side valve timing control mechanism that controls the opening and closing timing of the exhaust valve, and the control unit may perform a linked operation in which the target phase of one of the intake side valve timing control mechanism and the exhaust side valve timing control mechanism is perturbed by the perturbation control unit, and the other target phase is perturbed in the same phase perturbation direction.

[0025] According to this, when performing phase perturbation control, the target phase of the intake-side valve timing control mechanism and the target phase of the exhaust-side valve timing control mechanism are perturbed simultaneously and in the same direction, so the relationship between the intake timing of the intake valve and the exhaust timing of the exhaust valve can be maintained.In particular, in a system in which an overlap region is set between the opening and closing timing (valve timing) of the intake-side valve timing control mechanism and the opening and closing timing (valve timing) of the exhaust-side valve timing control mechanism, the length of the overlap region can be maintained, enabling good intake and exhaust.

[0026] In addition to the above configuration, the internal combustion engine may further include, as the valve timing control mechanism, an intake-side valve timing control mechanism that controls the opening and closing timing of an intake valve, and an exhaust-side valve timing control mechanism that controls the opening and closing timing of an exhaust valve, and an overlap region in which the intake valve is opened by the intake-side valve timing control mechanism is set at a timing before the exhaust valve is closed by the exhaust-side valve timing control mechanism, Intake In a state where the opening / closing timing of either the intake side valve timing control mechanism or the exhaust side valve timing control mechanism is displaced in a direction that expands the overlap region, the fluctuation control unit may fluctuate the target phase of the other of the intake side valve timing control mechanism and the exhaust side valve timing control mechanism.

[0027] According to this, by displacing the opening and closing timing of one of the intake side valve opening and closing timing control mechanism and the exhaust valve exhaust side valve opening and closing timing control mechanism in a direction that expands the overlap region, and fluctuating the other of the intake side valve opening and closing timing control mechanism and the exhaust valve exhaust side valve opening and closing timing control mechanism using fluctuation control, it is possible to secure the overlap region required for intake and exhaust of the combustion chamber even at a timing when the overlap region is decreasing, and there is no reduction in the intake and exhaust performance of the internal combustion engine.

[0028] In addition to the above configuration, the internal combustion engine may be provided with an intake side valve timing control mechanism as the valve timing control mechanism for controlling the opening and closing timing of the intake valve, and an electric throttle for controlling the amount of intake air supplied to the combustion chamber, and the control unit may increase the amount of intake air by the throttle in conjunction with an increase in the amount of displacement of the intake side valve timing control mechanism in the advance direction when control is performed by the fluctuation control unit in the intake side valve timing control mechanism.

[0029] According to this, when phase fluctuation control is performed in the intake side valve timing control mechanism, if the intake timing of the intake side valve timing control mechanism is displaced in the advance direction to increase the intake volume, the flow rate at the throttle can be increased in accordance with the amount of displacement in the advance direction, thereby eliminating the inconvenience of insufficient intake volume in the combustion chamber.

[0030] In addition to the above configuration, the internal combustion engine may be provided with a fuel injection device that supplies fuel to a combustion chamber, and the control unit may control the amount of fuel injected by the fuel injection device in response to an increase or decrease in the amount of intake air caused by the throttle.

[0031] According to this, in conjunction with the control by the fluctuation control unit, when the amount of intake air at the intake valve increases or decreases, the amount of fuel injected by the fuel injection device is increased or decreased, thereby maintaining a constant air-fuel ratio and enabling good combustion. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 2 is a diagram showing a cross section of an engine and a control unit. [Figure 2] FIG. 2 is a cross-sectional view of a valve timing control mechanism. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] 10 is a chart showing fluctuations in actual phase. [Figure 5] 10 is a flowchart of phase control. [Figure 6] 10 is a flowchart of vibration control. [Figure 7] 1 is a chart showing valve timing and overlap region. [Figure 8] 10 is a timing chart showing the rotation speed of the crankshaft, the timing of the intake side variable valve mechanism, the flag, the exhaust side variable valve mechanism, and the throttle opening. [Figure 9] 10 is a chart showing valve timing and overlap region in another embodiment (a). DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic configuration] As shown in FIG. 1, the valve timing control unit A is configured to include an intake-side variable valve mechanism VTa (an example of an intake-side valve timing control mechanism) that sets the valve timing (opening / closing timing) of an intake valve Va of an engine E as an internal combustion engine, an exhaust-side variable valve mechanism VTb (an example of an exhaust-side valve timing control mechanism) that sets the valve timing (opening / closing timing) of an exhaust valve Vb of the engine E, and 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.

[0034] The engine E (an example of an internal combustion engine) is provided in a vehicle such as a passenger car to provide driving force for the vehicle. The engine control device 40 not only controls the variable valve mechanism VT (a generic concept that includes the intake variable valve mechanism VTa and the exhaust variable valve mechanism VTb), but also controls the starting and stopping of the engine E. In particular, when a predetermined condition is met while the engine E is running, the engine control device 40 performs oscillation control that oscillates the actual phase P (see FIG. 4) of the variable valve mechanism VT (oscillates back and forth between the advance side and the retard side), thereby suppressing wear on the bearings and gears of the variable valve mechanism VT. This control form will be described later.

[0035] 〔engine〕 As shown in Figures 1 and 2, engine E is a four-stroke engine, with a cylinder head 3 connected to the top of a cylinder block 2 that rotatably supports a crankshaft 1, pistons 4 housed in multiple cylinder bores formed in the cylinder block 2 so that they can reciprocate freely, and the pistons 4 are connected to the crankshaft 1 by connecting rods 5.

[0036] The cylinder head 3 is equipped with an intake valve Va and an exhaust valve Vb, and an intake camshaft 7 that controls the intake valve Va and an exhaust camshaft 8 that controls the exhaust valve Vb are provided on the top of the cylinder head 3. A timing belt 6 is wound around an output pulley 1S of the crankshaft 1 and drive pulleys 21S of the intake-side variable valve mechanism VTa and the exhaust-side variable valve mechanism VTb.

[0037] The cylinder head 3 is equipped with an injector 9 (an example of a fuel injection device) that injects fuel into the combustion chamber, and an ignition plug 10. Connected to the cylinder head 3 are an intake manifold 11 that supplies air to the combustion chamber via an intake valve Va, and an exhaust manifold 12 that sends out the combustion gas in the combustion chamber via an exhaust valve Vb.

[0038] Furthermore, an electric throttle 13 that adjusts the intake amount by controlling a throttle control motor 13a is provided upstream of the intake manifold 11, and a catalyst 14 that purifies exhaust gas is provided intermediate the exhaust manifold 12. The engine E is equipped with a starter motor 15 (see Figure 2) that drives and rotates the crankshaft 1 when the engine E is started.

[0039] [Variable valve mechanism] 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) have a common configuration, so in Figures 2 and 3, the common symbols are used for the common configuration, and symbols that enable distinction are used for parts that need to be distinguished.

[0040] As shown in FIGS. 2 and 3, the variable valve mechanism VT has a drive case 21 (an example of an intake driving-side rotor / exhaust driving-side rotor) and an inner rotor 22 (an example of an intake driven-side rotor / exhaust driven-side rotor) arranged coaxially with the rotational axis X of the intake camshaft 7 or the exhaust camshaft 8, and is equipped with a phase adjustment mechanism G (an example of a reduction gear) that controls the relative rotational phase between them using the driving force of a phase control motor M (a generic concept that includes the intake-side phase control motor Ma and the exhaust-side phase control motor Mb) as an electric motor.

[0041] A drive pulley 21S is formed on the outer periphery of the drive case 21. The inner rotor 22 is housed within the drive case 21 and is connected and fixed to the intake camshaft 7 or the exhaust camshaft 8 by connecting bolts 23. With this configuration, the drive case 21 is supported on the outer periphery of the inner rotor 22 so as to be relatively rotatable, and the inner rotor 22 rotates integrally with the corresponding camshaft (intake camshaft 7 or exhaust camshaft 8).

[0042] A front plate 24 is fastened by a plurality of fastening bolts 25 to a position that covers the opening of the drive case 21. As a result, the front plate 24 restricts the displacement of the phase adjustment mechanism G and the inner rotor 22 in the direction along the rotation axis X.

[0043] 1 and 3, the variable valve mechanism VT rotates as a whole in a driving rotation direction S due to the driving force from the timing belt 6. Furthermore, the driving force of the phase control motor M is transmitted to the internal rotor 22 via a phase adjustment mechanism G, thereby displacing the relative rotation phase of the internal rotor 22 with respect to the drive case 21. Of this displacement, the direction of displacement that is the same as the driving rotation direction S is called the advance direction Sa, and the opposite direction is called the retard direction Sb.

[0044] [Variable valve mechanism: Phase adjustment mechanism] The phase adjustment mechanism G includes a ring gear 26 formed coaxially with the rotation axis X on the inner periphery of the inner rotor 22, an inner gear 27 rotatably arranged coaxially with the eccentric axis Y on the inner periphery side of the inner rotor 22, an eccentric cam body 28 arranged on the inner periphery side of the inner gear 27, a front plate 24, and a joint J. The eccentric axis Y is formed in an orientation parallel to the rotation axis X.

[0045] The ring gear 26 has a plurality of internal teeth 26T, and the inner gear 27 has a plurality of external teeth 27T, and by arranging this inner gear 27 in a position along the eccentric cam surface 28A on the outer periphery of the eccentric cam body 28, the inner gear 27 is arranged coaxially with the eccentric axis Y, and a portion of the external teeth 27T meshes with the internal teeth 26T of the ring gear 26. This phase adjustment mechanism G is configured as an internal planetary gear reducer in which the number of teeth of the external teeth 27T of the inner gear 27 is one less than the number of teeth of the internal teeth 26T of the ring gear 26.

[0046] The joint portion J has a joint member 33 formed by pressing a steel plate, and is configured as an Oldham coupling in which the outer periphery of this joint member 33 engages with the drive case 21, and the inner periphery of this joint member 33 engages with the engaging protrusion 27U of the inner gear 27. As a result, the joint portion J achieves an operation in which the inner gear 27 and the drive case 21 rotate integrally while maintaining an eccentric positional relationship of the inner gear 27 with respect to the drive case 21.

[0047] The eccentric cam body 28 is cylindrical overall, and has a pair of engagement grooves 28B formed on its inner periphery in a position parallel to the rotation axis X. The eccentric cam body 28 is supported by a first bearing 31 (an example of a bearing) that functions as a rolling bearing on the front plate 24 so as to rotate coaxially with the rotation axis X. Furthermore, an eccentric cam surface 28A is formed on the outer periphery of the first bearing 31 at a position closer to the intake camshaft 7 than the support position of the first bearing 31.

[0048] Eccentric cam surface 28A is formed in a circular shape (with a circular cross section) centered on eccentric axis Y, which is oriented parallel to rotation axis X. Inner gear 27 is rotatably supported on the outer periphery of eccentric cam surface 28A via second bearing 32 (an example of a bearing) that functions as a rolling bearing. In addition, a spring body 29 is fitted into a recess formed in eccentric cam surface 28A, and the biasing force of this spring body 29 is configured to act on inner gear 27 via second bearing 32. With this configuration, part of external teeth portion 27T of inner gear 27 meshes with part of internal teeth portion 26T of ring gear 26, and the meshed state is maintained by the biasing force of spring body 29.

[0049] The phase control motor M is supported by the engine E, and an engagement pin 34 formed on the output shaft Ms is fitted into an engagement groove 28B on the inner periphery of the eccentric cam body 28. Although not shown in detail, the phase control motor M is configured as a brushless type having a structure common to a three-phase motor, by including a rotor having a permanent magnet, a stator having a plurality of field coils arranged in a position surrounding the rotor, and an output shaft Ms to which the rotation of the rotor is transmitted.

[0050] In this variable valve mechanism VT, when the engine E is running, the output shaft Ms is driven to rotate in the driving 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 is shifted in the advance direction Sa, the rotational speed of the output shaft Ms is reduced, and when the relative rotational phase is shifted in the retard direction Sb, the rotational speed of the output shaft Ms is increased.

[0051] To explain this in the case where the engine E is stopped, in the phase adjustment mechanism G, the external teeth 27T of the inner gear 27 mesh with the internal teeth 26T of the ring gear 26. Therefore, when the eccentric cam body 28 rotates around the rotation axis X in accordance with the rotation of the output shaft Ms driven by the phase control motor M, the inner gear 27 revolves around the rotation axis X and simultaneously rotates around the eccentric axis Y in accordance with this rotation.

[0052] Furthermore, each time the inner gear 27 rotates (revolves) once around the rotation axis X, the inner gear 27 rotates (spins) relative to the ring gear 26 by an angle corresponding to the difference in the number of teeth between the inner gear 27 and the ring gear 26, thereby achieving a large reduction in speed. As a result, by controlling the rotational speed of the phase control motor M, the drive case 21, which rotates integrally with the inner gear 27 via the joint J, and the camshaft, which is connected to the ring gear 26 by the connecting bolt 23, are rotated relative to each other, thereby achieving adjustment of the valve timing.

[0053] [Control configuration] As shown in Figures 1 and 2, engine E is equipped with starter motor 15 that drives crankshaft 1 to rotate, a crank angle sensor 16 (which also functions as a rotation speed detector) that can detect the rotation angle is provided near crankshaft 1, an intake-side camshaft angle sensor 17 that can detect the rotation angle of intake camshaft 7 is provided near intake camshaft 7, and an exhaust-side camshaft angle sensor 18 that can detect the rotation angle of exhaust camshaft 8 is provided near exhaust camshaft 8.

[0054] Crank angle sensor 16, intake camshaft angle sensor 17, and exhaust camshaft angle sensor 18 are configured as pickup sensors that intermittently output pulse signals as they rotate. Crank angle sensor 16 acquires the rotation angle from the rotation reference by counting pulse signals from the rotation reference of crankshaft 1 as crankshaft 1 rotates. Similarly, intake camshaft angle sensor 17 and exhaust camshaft angle sensor 18 are configured to count pulse signals from the rotation reference of intake camshaft 7 as intake camshaft 7 rotates, allowing engine control device 40 to acquire the rotation angle from the rotation reference.

[0055] With this configuration, for example, by storing the count value of crank angle sensor 16 and the count value of intake-side camshaft angle sensor 17 or exhaust-side camshaft angle sensor 18 when drive case 21 and internal rotor 22 shown in FIG. 3 are in a predetermined reference phase (for example, an intermediate phase), the relative rotational phase can be obtained by comparing the two count values ​​regardless of whether the relative rotational phase is displaced from the reference phase to the advance side (advance direction Sa) or to the retard side (retard direction Sb).

[0056] In this way, the crank angle sensor 16 and the intake side camshaft angle sensor 17 constitute an intake side phase sensor, and the crank angle sensor 16 and the exhaust side camshaft angle sensor 18 constitute an exhaust side phase sensor.

[0057] 1, engine control device 40 receives detection signals from crank angle sensor 16, intake camshaft angle sensor 17, and exhaust camshaft angle sensor 18, as well as detection signals from a main switch 45 and an accelerator pedal sensor 47. Engine control device 40 outputs control signals to starter motor 15, phase control motor M (intake phase control motor Ma and exhaust phase control motor Mb), combustion management unit 19, and throttle control motor 13a.

[0058] The engine control device 40 also includes an engine control section 41, a phase control section 42, a fluctuation control section 43, and a correction control section 44. These are configured using software, but some of these can be configured using only hardware, or they can be configured using a combination of hardware and software.

[0059] The engine control unit 41 controls the engine E from start to stop, and the phase control unit 42 controls the valve timing (opening / closing timing) of the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb when the engine E is started, running, and stopped. The fluctuation control unit 43 suppresses wear on the bearings (first bearing 31 and second bearing 32) and gears (ring gear 26 and inner gear 27) by executing the fluctuation control shown in the flowchart of Fig. 6. The correction control unit 44 corrects the intake amount, etc. when the fluctuation control unit 43 is running.

[0060] In this control configuration, a main switch 45 is located on a panel near the driver's seat of the vehicle, and enables manual start and complete stop of the engine E. An accelerator pedal sensor 47 acquires the depression amount of the accelerator pedal (not shown). A combustion management unit 19 manages the operation of pumps that supply fuel to the injectors 9, and also manages the ignition order and timing by controlling an ignition circuit that supplies power to the spark plugs 10.

[0061] [Control mode] The intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb are equipped with an eccentric cam body 28 that meshes a portion of the internal tooth portion 26T of the ring gear 26 with a portion of the external tooth portion 27T of the inner gear 27, and the eccentric cam body 28 exerts a biasing force from a spring body 29.

[0062] With this configuration, a strong force acts on the first bearing 31 and the second bearing 32, which maintain the ring gear 26 and the inner gear 27 in an eccentric positional relationship with each other and enable the relative rotational phase to be displaced, and at the same time, a strong force also acts on the contact surface between the internal tooth portion 26T and the external tooth portion 27T.

[0063] In particular, since the first bearing 31 and the second bearing 32 have a structure in which multiple balls are arranged between an inner race and an outer race, when the pressure caused by the cam fluctuation torque acts on the first bearing 31 and the second bearing 32 while the engine E is running, it was thought that the balls would be pressed against the inner race and the outer race in the radial direction, causing wear on the balls.

[0064] Similarly, when engine E is running, the pressure caused by the action of cam fluctuation torque acts on the contact surface between internal tooth portion 26T and external tooth portion 27T, which could lead to wear on the contact surface.

[0065] In order to suppress such wear, the engine control device 40 performs control shown in the flowchart of Fig. 5. This flowchart shows a control form for phase control of the intake-side variable valve mechanism VTa to control the valve timing (opening / closing timing) of the intake valve Va while the engine E is operating.

[0066] That is, the target phase is obtained based on information such as the amount of accelerator pedal depression detected by the accelerator pedal sensor 47 or the number of rotations counted by the crank angle sensor 16 (number of rotations of the crankshaft 1 per unit time) (step #01), and the actual phase of the intake side variable valve mechanism VTa is obtained based on the count value of the crank angle sensor 16 and the count value of the intake side camshaft angle sensor 17 (step #02).

[0067] Steps #01 and #02 are executed by the phase control unit 42, which determines whether the phase difference between the target phase thus acquired and the actual phase is less than a set value (for example, 1.0 CA to 1.2 CA) or greater than or equal to the set value (step #03). Step #03 is executed by the phase control unit 42, and if it determines that the phase difference is not less than the set value (No in step #03), it performs phase difference convergence control (control to operate the intake-side phase control motor Ma in a direction to reduce the phase difference) (step #04), after which it exits phase control and returns. Step #04 is executed by the phase control unit 42.

[0068] In particular, as shown in Fig. 4, in the phase difference convergence control, a holding region K is formed on both the advance side and the retard side with respect to the target phase T, and the phase difference convergence control (control in step #04) converges (stops) when the actual phase P reaches a state where it is included in the holding region K. The holding region K is formed in a relatively narrow region, and when the phase difference convergence control has converged, the actual phase P is included in the holding region K and fluctuates alternately between the advance side and the retard side due to the action of the cam fluctuation torque (the rotational speed of the intake camshaft 7 increases and decreases). Note that the initial region Q in Fig. 4 shows a state where the target phase T and the actual phase P have converged.

[0069] If it is determined in step #03 that the phase difference is less than the set value (Yes in step #03), and if this state continues for a set time (for example, about 0.1 seconds) or more (Yes in step #05), the rotation speed (number of rotations per unit time) of the crankshaft 1 is acquired, and it is determined whether the acquired rotation speed is equal to or greater than the set number (steps #06 and #07). Also, if the phase difference is less than the set value (Yes in step #03), and the duration of this state is less than the set time (No in step #05), the process exits this phase control and returns.

[0070] If it is determined in step #07 that the number of rotations is equal to or greater than the set number (Yes in step #07), then oscillation control (step #100) is executed, and if the number of rotations is less than the set number (No in step #07), then control is terminated and the process returns. Note that steps #05 to #07 are processes for determining whether or not to switch to oscillation control, and are executed by the oscillation control unit 43.

[0071] In this way, fluctuation control (step #100) is executed when the phase difference is less than the set value (converged state), this state continues beyond the set time, and the rotation speed of crankshaft 1 is equal to or greater than the set rotation speed.

[0072] The oscillation control (step #100) is set as a subroutine and is basically executed by the oscillation control unit 43. That is, as shown in the flowchart of Fig. 6, the target phase T for the intake side and the exhaust side (see Fig. 4, in which only one of the intake side and the exhaust side is shown) is obtained, and oscillation target phases Tx, Ty are set that are separated by an equal amount based on the two obtained target phases (steps #102, #103).

[0073] In the timing chart of Fig. 4, the perturbation target phases Tx and Ty are set so that the amplitude is equal in the direction in which the deviation increases and in the direction in which it decreases (up and down in Fig. 4) with respect to the target phase T. The distance between the perturbation target phases Tx and Ty in the perturbation direction (up and down in Fig. 4) is the perturbation amount of the target phase, and this perturbation amount is set larger than the amount of fluctuation in the actual phase P due to the action of the cam fluctuation torque.

[0074] The rotation speed of the intake camshaft 7 fluctuates alternately between the advance and retard directions due to the action of the cam fluctuation torque, so the rotation speed increases and decreases in short cycles. As a result, the actual phase P fluctuates in a wave-like manner with a predetermined amplitude as shown by the solid line in the timing chart of Figure 4, and the amplitude of this fluctuation is the amount of fluctuation.

[0075] Because the amount of fluctuation in the actual phase P is small, if the state in the holding region K continues, there is a risk of wear occurring due to pressure acting locally on the balls of the first bearing 31 and the second bearing 32. Therefore, in order to suppress this wear, it is desirable to rotate the balls by a predetermined angle (for example, 45 degrees, 90 degrees, etc.) or more using oscillation control. For this reason, the oscillation target phases Tx, Ty are set so as to rotate the balls by a predetermined angle or more, and the values ​​of the oscillation target phases Tx, Ty are configured to be larger than the amount of fluctuation by which the actual phase P fluctuates in the holding region K.

[0076] After the oscillation target phases Tx and Ty are set in this way, the oscillation operation (step #103) is performed. Note that the phase difference convergence control executed in step #103 simply utilizes a phase difference convergence control routine to oscillate the drive case 21 and the internal rotor 22, and is different from the control for converging the actual phase P to the target phase T (holding region K).

[0077] For example, if the perturbation target phase Tx is set to the advance side with respect to the target phase T, and the perturbation target phase Ty is set to the retard side with respect to the target phase T, then in the perturbation operation (step #103), the two perturbation target phases Tx and Ty are switched at a set cycle R, and phase difference convergence control is performed, thereby controlling the throttle 13 in response to fluctuations in the intake air amount that accompany these controls. This control of the throttle 13 is executed by the correction control unit 44.

[0078] In the control of step #103, two target perturbation phases Tx, Ty are switched between the advance side (advance direction Sa) and the retard side (retard direction Sb) at an equal set period R, and phase difference convergence control is performed in the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb, resulting in equal reciprocating motion so as to follow the pattern indicated by the peaks and valleys of the dashed lines in the timing chart of Figure 4. After the control of step #103, the process returns to the phase control of Figure 5. The target perturbation phase and set period may be set depending on the engine state (speed and load).

[0079] In particular, with this oscillating operation, as shown in Figure 7, 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 by equal amounts in the same direction and at the same timing in the crank angle direction.

[0080] In this way, by performing the wobbling operation, the drive case 21 and the inner rotor 22 wobble relative to each other, which prevents the balls of the first bearing 31 and the second bearing 32 from pressing against the inner race or the outer race, which causes wear, and prevents the internal teeth 26T of the ring gear 26 from pressing against the external teeth 27T of the inner gear 27, which causes wear on the pressing surfaces. Furthermore, as shown in Figure 7, by performing the wobbling operation so that the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb operate in the same direction in coordination (coordinated operation), the length of the overlap region W does not change and the intake amount does not fluctuate.

[0081] 7, the initial exhaust valve timing Ex of the exhaust variable valve mechanism VTb is shown by a solid line, and the intake valve timing In of the intake variable valve mechanism VTa is shown by a dashed line. The exhaust valve Vb transitions to a closed state at the valve closing timing EVC of the exhaust valve timing Ex, and the intake valve Va transitions to an open state before this at the valve opening timing IVO of the intake valve timing In. This results in an overlap region W between the valve closing timing EVC and the valve opening timing IVO.

[0082] [Timing chart] The timing chart in Figure 8 also shows the rotation speed of the crankshaft 1 when fluctuation control is performed during the process from starting to stopping the engine E, the valve timing of the intake side variable valve mechanism VTa, and the flag when fluctuation control is executed.

[0083] This chart also shows the valve timing of the exhaust-side variable valve mechanism VTb and the opening of the throttle 13, but these will be explained in another embodiment (b).

[0084] As shown in the timing chart of Figure 8, when engine E starts, the valve timing of the intake variable valve mechanism VTa is Slow After engine E starts, Susumu Immediately after starting the engine E, the catalyst is warmed up with the rotation speed of the crankshaft 1 kept relatively high.

[0085] When the valve timing of the intake-side variable valve mechanism VTa is set to the retard side, a predetermined target phase T (see FIG. 4) is set, and the intake-side phase control motor Ma controls the actual phase P to converge to the target phase T, so that the conditions of steps #03 and #05 described above are met. When the conditions are met in this way, the flag switches from OFF to ON, and fluctuation control (step #100 in FIG. 5) is performed.

[0086] Although this timing chart only shows the oscillation control of the intake side variable valve mechanism VTa, oscillation control is performed in synchronization with the intake side variable valve mechanism VTa, which oscillates the actual phase P of the exhaust side variable valve mechanism VTb in the same direction and at the same timing as the oscillation direction of the intake side variable valve mechanism VTa, and this oscillation control maintains the overlap region W constant.

[0087] Furthermore, when the phase difference between the target phase and the actual phase is equal to or greater than the set value, or when the rotation speed of the crankshaft 1 is low, such as when the engine E is in an idling state, no fluctuation control is performed. Instead, when the phase difference between the target phase and the actual phase converges to less than the set value (step #03) and the rotation speed of the crankshaft 1 reaches a high state, such as when a passenger car or the like is traveling (step #05), flags are turned ON in three regions, the first region U1, the second region U2, and the third region U3, where the conditions are met, and fluctuation control is performed corresponding to these regions.

[0088] [Effects of the embodiment] When the deviation between the target phase and the actual phase exceeds a set value, phase difference convergence control (control that operates the phase control motor M in a direction that reduces the phase difference) is performed, and the bearing balls rotate and move between the inner race and the outer race, preventing them from coming into pressure contact at a specific position and eliminating the inconvenience of wear.For the same reason, when phase control is performed, the contact points between the internal teeth portion 26T and the external teeth portion 27T move, preventing the internal teeth portion 26T and the external teeth portion 27T from coming into pressure contact and causing wear.

[0089] Furthermore, when the variable valve mechanism VT (intake variable valve mechanism VTa or exhaust variable valve mechanism VTb) rotates at a relatively low rotational speed, the rotational speeds of the drive case 21 and the internal rotor 22 naturally increase and decrease relative to each other, causing a "fluctuation" in which the actual phase fluctuates. The amplitude (difference in rotational angle) of this "fluctuation" tends to decrease as the rotational speed of the variable valve mechanism VT increases. Therefore, when the rotational speed detected by the crank angle sensor 16 (rotational speed detection unit) is low, even without performing fluctuation control, the area in which pressure acts on the bearings (first bearing 31 or second bearing 32) and gears (ring gear 26 and inner gear 27) is expanded, thereby suppressing the disadvantage of strong force continuously acting in the pressing direction on specific parts of the bearings and gears.

[0090] On the other hand, when the rotation speed of the variable valve mechanism VT increases, the amplitude of the "fluctuation" decreases, and the pressure acting on specific positions of the bearings and gears increases, resulting in wear. For this reason, when the phase difference convergence control reaches a state where there is almost no control to change the relative rotation between the drive case 21 and the internal rotor 22, and the rotation speed detected by the crank angle sensor 16 reaches a set number or more, fluctuation control (step #100) is executed to perform control to fluctuate the actual phase P, thereby suppressing the phenomenon in which a strong force continuously acts in the pressing direction on specific positions of the bearings and gears and eliminating wear.

[0091] Furthermore, when performing oscillation control, the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb are synchronized in the same direction and oscillated by equal amounts, which not only reduces wear on the bearings and gears but also prevents fluctuations in the intake volume and maintains the length of the overlap region W, preventing fluctuations in intake and exhaust performance.

[0092] [Another embodiment] The present invention may be configured as follows in addition to the above-described embodiments (common numbers and symbols are used to designate components having the same functions as those in the embodiments).

[0093] (a) When only one of the exhaust side variable valve mechanism VTb and the intake side variable valve mechanism VTa is subjected to oscillation control, in order to maintain the lap length of the overlap region W at or above a set value, the timing of the variable valve mechanism VT on the side that is not subjected to oscillation control is controlled to be moved in advance in the direction that increases the lap length of the overlap region W.

[0094] In this alternative embodiment (a), for example, an exhaust-side variable valve mechanism VTb configured to hydraulically control exhaust timing is used, and only the intake-side variable valve mechanism VTa is subjected to oscillation control. To give a specific example, in Figure 9, the initial exhaust valve timing Ex of the exhaust-side variable valve mechanism VTb is shown by a solid line, and the intake valve timing In of the intake-side variable valve mechanism VTa before oscillation control is performed is shown by a dashed line. The region where the exhaust valve timing Ex and the intake valve timing In overlap is shown as an initial overlap region Wp (an example of the overlap region W).

[0095] With the valve timings set in this manner, when the intake-side variable valve mechanism VTa is controlled to fluctuate (fluctuate between the advance direction Sa and the retard direction Sb in the same figure), the control form is set so that an expanded overlap region Ws (an example of the overlap region W) is set in advance by shifting the exhaust valve timing Ex from the initial timing in the retard direction Sb by the set timing Z shown by the two-dot chain line so that the initial overlap region Wp can be secured.

[0096] By performing this type of control, even if the intake valve timing In is displaced in the retard direction Sb by perturbation control, it is possible to easily discharge and inhale gas from the combustion chamber in the overlap region W. This control of displacing the exhaust valve timing Ex from the initial timing in the retard direction Sb by a preset timing Z is realized by control of the correction control unit 44. By setting this preset timing Z to be equal to or greater than the perturbation target phase Ty (when Ty is in the retard direction Sb) when the intake-side variable valve mechanism VTa is perturbed, the initial overlap region Wp can be secured even when the intake-side variable valve mechanism VTa reaches the perturbation target phase Ty.

[0097] Furthermore, this alternative embodiment (a) can also be realized by performing control to advance the valve timing of the intake variable valve mechanism VTa in advance by the set timing Z when only the actual phase P of the exhaust variable valve mechanism VTb is subjected to fluctuation control. As a variable valve mechanism VT that advances the valve timing in this way, a mechanism that hydraulically controls the valve timing can be used.

[0098] (b) As shown in the timing chart of Figure 8, when the intake side variable valve mechanism VTa is subjected to fluctuation control, the valve timing of the exhaust side variable valve mechanism VTb is set at a timing synchronized with this fluctuation control, and the intake amount is increased or decreased by controlling the throttle 13.

[0099] In the figure, the fluctuation control is performed in three regions: a first region U1, a second region U2, and a third region U3. In the fluctuation control in the first region U1 and the second region U2, the intake-side variable valve mechanism VTa is displaced by an increased amount in the advance direction to increase the intake amount, while in the third region U3, the amount of displacement in the advance direction is reduced to reduce the intake amount.

[0100] In order to reliably increase or decrease the intake volume in this way, the fluctuation control between the first region U1 and the second region U2 shifts the exhaust timing in the retard direction as shown by the dashed line at the timing of the exhaust side variable valve mechanism VTb, and increases the intake volume at the throttle 13 as shown by the dashed line at the timing of the throttle 13.

[0101] In contrast, in the fluctuation control of the third region U3, the exhaust timing is advanced as shown by the dashed line at the timing of the exhaust side variable valve mechanism VTb, and the intake amount at the throttle 13 is reduced as shown by the dashed line at the timing of the throttle 13.

[0102] In this alternative embodiment (b), control of the exhaust-side variable valve mechanism VTb and the throttle 13 is achieved by control of the correction control unit 44. This type of control makes it possible to suppress fluctuations in the intake amount when the intake-side variable valve mechanism VTa is subjected to oscillating control. Also, in this alternative embodiment (b), high-speed operation of the exhaust-side variable valve mechanism VTb is not required, so a configuration in which the exhaust timing is controlled hydraulically can be used.

[0103] (c) In a situation where the intake-side variable valve mechanism VTa is increased in the advance direction and the exhaust-side variable valve mechanism VTb is retarded as in the previously described alternative embodiment (b), control is performed to increase the amount of fuel supplied by the injector 9. By performing such control, the air-fuel ratio can be kept constant and proper combustion in the combustion chamber can be maintained. [Industrial Applicability]

[0104] The present invention can be used in a valve timing control unit. [Explanation of symbols]

[0105] 1 crankshaft 9 Injector (fuel injection device) 13 Throttle 16 Crankshaft sensor (rotation speed detection part) 17 Intake side camshaft angle sensor (camshaft angle sensor) 18 Exhaust camshaft angle sensor (camshaft angle sensor) 21 Drive case (drive side rotor) 22 Internal rotor (driven rotor) 31 First bearing (bearing) 32 Second bearing (bearing) 40 Engine control device (control unit) 43 Vibration control unit E Engine (internal combustion engine) G Phase adjustment mechanism (reduction gear) M Electric motor Ma Intake side phase control motor (electric motor) Mb Exhaust side phase control motor (electric motor) Tx, Ty oscillation target phase Va Intake valve (camshaft) Vb Exhaust valve (camshaft) VT Variable valve timing mechanism (valve timing control mechanism) VTa variable intake valve timing mechanism (intake valve timing control mechanism) VTb Exhaust side variable valve timing mechanism (exhaust side valve timing control mechanism) R setting cycle W overlap area X rotation axis

Claims

1. a drive-side rotor that rotates synchronously with the crankshaft of the internal combustion engine; a driven-side rotor that rotates integrally with a camshaft that opens and closes a valve of a combustion chamber of the internal combustion engine, is coaxial with the rotational axis of the drive-side rotor, and is arranged so that its relative rotational phase can be changed with respect to the drive-side rotor via a bearing; an electric motor and a reduction gear for setting the relative rotational phase; a valve opening / closing timing control mechanism including a phase sensor that detects the relative rotational phase between the drive-side rotor and the driven-side rotor as an actual phase centered on the rotation axis, a control unit that controls the electric motor in a direction that reduces a phase difference between the actual phase detected by the phase sensor and a target phase, a holding region is formed across an advance angle side and a retard angle side with respect to the target phase, and the control unit includes a fluctuation control unit that fluctuates the target phase near the target phase when the target phase is maintained and a fluctuation amount of the actual phase is held in the holding region, A valve opening / closing timing control unit is provided with a rotation speed detection unit that detects the rotation speed per unit time of the crankshaft, and starts control by the fluctuation control unit when the rotation speed detected by the rotation speed detection unit exceeds a set value.

2. The valve opening / closing timing control unit according to claim 1, wherein the fluctuation control unit sets a fluctuation target phase that is displaced by an amount equal to the advance side and the retard side based on the value of the target phase, and fluctuates the target phase back and forth between the two fluctuation target phases at a set period.

3. the phase sensor comprises a crank 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 unit that calculates the actual phase from detection signals of the crank angle sensor and the camshaft angle sensor, 3. The valve timing control unit according to claim 1, wherein the absolute value of the difference between the maximum value and the minimum value of the actual phase calculated by the calculation unit is set as the fluctuation amount.

4. 2. The valve timing control unit according to claim 1, wherein the fluctuation amount of the target phase in the fluctuation control section is set to a value greater than the fluctuation amount by which the actual phase fluctuates in the holding region.

5. the internal combustion engine is equipped with, as the valve timing control mechanism, an intake-side valve timing control mechanism that controls the opening and closing timing of an intake valve, and an exhaust-side valve timing control mechanism that controls the opening and closing timing of an exhaust valve, The control unit is configured to perform a linked operation in which the target phase of one of the intake side valve timing control mechanism and the exhaust side valve timing control mechanism is fluctuated in the same phase fluctuating direction in conjunction with the control of the fluctuating control unit to fluctuate the target phase of the other of the intake side valve timing control mechanism and the exhaust side valve timing control mechanism.

6. the internal combustion engine includes, as the valve timing control mechanism, an intake-side valve timing control mechanism that controls the opening and closing timing of an intake valve, and an exhaust-side valve timing control mechanism that controls the opening and closing timing of an exhaust valve, an overlap region in which the intake valve is opened by the intake-side valve timing control mechanism is set at a timing before the exhaust valve is closed by the exhaust-side valve timing control mechanism; When the opening / closing timing of either the intake-side valve timing control mechanism or the exhaust-side valve timing control mechanism is displaced in a direction that expands the overlap region, 5. The valve timing control unit according to claim 1, wherein the fluctuation control section fluctuates the target phase of either the intake side valve timing control mechanism or the exhaust side valve timing control mechanism.

7. The internal combustion engine includes, as the valve timing control mechanism, an intake-side valve timing control mechanism that controls the opening and closing timing of an intake valve, and an electric throttle that controls the amount of intake air supplied to a combustion chamber; A valve timing control unit as described in any one of claims 1 to 4, wherein the control unit increases the intake amount by the throttle in conjunction with an increase in the amount of displacement of the intake side valve timing control mechanism in the advance direction when control is performed by the fluctuation control unit in the intake side valve timing control mechanism.

8. the internal combustion engine includes a fuel injection device that supplies fuel to a combustion chamber; 8. The valve timing control unit according to claim 7, wherein the control unit controls the amount of fuel injected by the fuel injection device in response to an increase or decrease in the intake air amount caused by the throttle.

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