JP3873662B2 - Control device for variable valve timing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sound countermeasure technique for a variable valve timing device that variably controls a valve timing by changing a rotational phase of a camshaft with respect to a crankshaft by friction braking by an electromagnetic brake.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a variable valve timing device for an engine having a configuration in which a rotational phase of a camshaft with respect to a crankshaft (hereinafter simply referred to as a rotational phase) is changed by friction braking by an electromagnetic brake (see JP-A-10-153105). ).
The amount of change in the rotational phase due to the electromagnetic brake is regulated by a stopper provided between the rotating bodies that rotate relative to each other. However, if the target value of the rotational phase changes greatly, such as when starting the vehicle or accelerating, the rotating body is caused by overshoot. The two collide with the stopper, and the collision sound becomes a problem. In addition, the increase in the number of collisions also shortens the life of the stopper.
[0003]
Conventionally, there has been proposed a method in which the amount of change in the rotational phase is limited to prevent a collision with the stopper in advance, or the rate of change is sufficiently reduced in advance in consideration of product variation to suppress overshoot. However, in the former, the control range of the valve timing is limited, and in the latter, the low responsiveness is always maintained, and both of them impair the performance.
[0004]
The present invention has been made paying attention to such a conventional problem, and by reducing the rotational phase change operation moderately moderately, the impact noise to the stopper is reduced while maintaining the control range and responsiveness. An object of the present invention is to provide a variable valve timing device for an internal combustion engine in which the life of the stopper is also improved.
[0005]
[Means for Solving the Problems]
For this reason, the invention according to claim 1
In a variable valve timing device for an internal combustion engine that variably controls the valve timing by changing the rotational phase of the camshaft relative to the crankshaft by friction braking by an electromagnetic brake,
Adjusted so that the rotational phase of the camshaft changes gradually according to the number of times it reaches a predetermined position near the limit position where the amount of change from the initial position due to the increase in friction braking is regulated by a stopper. It is characterized by doing.
[0006]
According to the invention of claim 1,
By estimating the number of times of collision with the stopper according to the number of times reaching the predetermined position in the vicinity of the limit position, and adjusting the rotational phase change operation to be gentle according to the number of times, the frequency of the collision can be reduced. It is possible to reduce or reduce the impact sound by reducing the impact at the time of collision, and by adjusting according to the estimated number of collisions, it is possible to suppress excessive adjustment and ensure control responsiveness. it can.
[0007]
The invention according to claim 2
The rotational phase of the camshaft is adjusted so that the rate of change of the rotational phase decreases as the number of times the rotational phase reaches the predetermined position increases.
According to the invention of claim 2,
As the number of times of reaching a predetermined position increases, the rate of change of the rotational phase is reduced, so that the effect of suppressing overshoot is enhanced and it becomes difficult to collide with the stopper, or the collision speed is reduced, thus reducing the collision sound. it can.
[0008]
The invention according to claim 3
While setting the target change rate of the rotational phase of the camshaft to be decreased as the number of times of reaching the predetermined position is increased, the target rotational phase of the camshaft is periodically calculated and set,
When the difference between the basic target rotational phase calculated based on the current engine operating state and the final target rotational phase calculated last time is within the target change rate, the target rotational phase is set as the basic target Set the rotation phase as the final target rotation phase,
When the difference exceeds the target change rate, the target change rate is added to the final target rotation phase calculated last time and set as the final target rotation phase at this time. .
[0009]
According to the invention of claim 3,
By limiting the change rate of the target rotational phase of the camshaft to be equal to or less than the target change rate, the camshaft can be operated at a change rate corresponding to the number of stopper collisions.
The invention according to claim 4
A table in which the target change rate is set in stages according to the number of times the predetermined position is reached is provided, and the target change rate is set with reference to the table.
[0010]
According to the invention of claim 4,
The target change rate can be easily set by referring to the table.
The invention according to claim 5
The number of times to reach the predetermined position is a cumulative value.
According to the invention of claim 5,
Even if there is a manufacturing variation, it is learned that the collision frequency of the stopper settles at a predetermined frequency, and it is possible to achieve both the reduction of the collision noise and the control responsiveness, and to ensure the durable life of the stopper.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 shows a cross section and a control system of a variable valve timing device using an electromagnetic brake in the embodiment, and FIG. 2 shows a schematic configuration in which functions of respective parts of the device are clarified. Here, what controls variable control of the valve timing of the intake valve will be described. The structurally the same is also applied to the one that variably controls the valve timing of the exhaust valve, but the control direction of the advance / retard angle when the friction braking force of the electromagnetic brake is applied is opposite.
[0012]
In the figure, on the extension line of the end 1a of the camshaft 1 that is rotatably supported with respect to a cylinder head (not shown), the cylindrical transmission member 2 is engaged with the engagement pin 3 to be prevented from rotating. The bolts 4 are connected and fixed.
A sprocket 5 is rotatably supported on the circumference of the transmission member 2. The sprocket 5 is supported so as to be rotatable relative to the camshaft 1, and rotates synchronously with the rotation of the crankshaft of the engine via a timing chain.
[0013]
The rotation of the sprocket 5 is transmitted to the transmission member 2 through a transmission mechanism described below.
A cylindrical drum 6 having a flange 6 a is provided coaxially with the camshaft 1, and a direction in which the rotational phase of the drum 6 is advanced between this drum 6 and the sprocket 5 (retarded for exhaust valves). A coil spring 7 for biasing in the direction) is interposed. That is, a case member 8 is fixed to the sprocket 5, one end portion (right end portion in the drawing) of the coil spring 7 is fixed to the case member 8, and the other end portion of the coil spring 7 is fixed to the flange 6 a of the drum 6. Has been.
[0014]
At opposite ends of the drum 6 and the case member 8, stoppers 6b and 8a for restricting the relative rotation amounts are provided (see FIG. 3 for the case member 8).
The gear 2a formed on the outer peripheral surface of the transmission member 2 and the gear 9a formed on the inner periphery of the cylindrical piston member 9 are engaged with each other by a helical mechanism using a helical gear.
[0015]
On the other hand, a male screw 9b is formed on the outer peripheral surface of the left end portion of the piston member 9 and a female screw 6c is formed on the inner peripheral surface of the drum 6 by about three threads, both of which are engaged by a screw action. The gear 9c formed on the outer peripheral surface of the right end portion of the piston member 9 and the gear 8b formed on the inner peripheral surface of the case member 8 are engaged with each other by a helical mechanism using a helical gear.
[0016]
The drum bearing member 10 is interposed between the outer peripheral surface of the transmission member 2 and the inner peripheral surface of the drum 6, and supports the relative rotation between the two. The outer peripheral portion of the drum bearing member 10 is engaged with an annular claw member 11 fitted to the drum 6 and a nut 12 screwed to the outer peripheral surface of the end portion of the transmission member 2 to move in the axial direction. Is regulated.
In addition, an electromagnetic brake 13 is fixedly disposed on the engine body at the outside (left side in the figure) of the drum 6. The electromagnetic brake 13 includes a clutch member 13b having a friction member 13a attached to a surface of the drum 6 facing the flange 6a. When the electromagnetic brake 13 is energized, the electromagnetic brake 13 moves in the direction of the flange 6a. It can be pressed against the end face of the flange 6a.
[0017]
The basic operation of such a variable valve timing device will be described.
When the electromagnetic brake 13 is not energized (control current = 0), the drum 6 is held at a position regulated by one of the stoppers 6b and 8a by the biasing force of the coil spring 7. The camshaft 1 is held at a position most retarded with respect to the crankshaft.
[0018]
When the camshaft 1 is controlled to the target valve timing by advancing the target angle with the most retarded position as a reference, the electromagnetic brake 13 is energized and the clutch member 13b is pressed against the flange surface 6a of the drum 6 to cause friction. Apply braking. As a result, the drum 6 is delayed with respect to the rotation of the sprocket 5 synchronized with the crankshaft. As a result, the piston member 9 meshed with the drum 6 by the male screw 9b and the female screw 6c Move in the axial direction (from left to right in the figure).
[0019]
The piston member 9 is meshed with the case member 8 and the transmission member 2 by the helical mechanism cut at opposite angles, and when the piston member 9 moves in the axial direction, the piston member 9 is cut at the opposite angle. The transmission member 2 rotates relative to the case member 8 in the advance direction along the helical tooth stripe, and the cam shaft 1 moves in the advance direction relative to the crankshaft that rotates synchronously with the sprocket 5. Relative rotation. Here, among the two helical mechanisms provided on the outer peripheral side and the inner peripheral side, one can be configured with a straight spline mechanism, but by providing two helical mechanisms cut at opposite angles, It can be advanced more greatly.
[0020]
As the current value to the electromagnetic brake 13 is increased and the braking force (sliding friction) against the urging force of the coil spring 7 is increased, the rotational phase of the camshaft 1 is advanced (or retarded for exhaust valves). Will be changed.
As described above, the rotational phase of the camshaft 1 changes with respect to the sprocket 5 (crankshaft) according to the rotational delay amount of the drum 6 determined according to the braking force by the electromagnetic brake 13, and the braking force by the electromagnetic brake 13 is increased. Can continuously control the amount of change in rotational phase (advance amount, retard amount for exhaust valves) by, for example, duty-controlling the control current supplied to the electromagnetic brake 13.
[0021]
Further, a number of protrusions (detected portions) 1b corresponding to the number of engine cylinders are formed at equal intervals in the rotational direction of the cam shaft 1 or the rotating member connected to the cam shaft 1. For example, in the case of a V-type 6-cylinder engine, three protrusions 1b are formed at intervals of 120 ° on the two left and right camshafts 1 corresponding to the left and right banks. A cam sensor 21 for detecting the protrusion 1b is provided in the vicinity of the outer periphery of the cam shaft 1.
[0022]
In addition to the cam sensor 21, an air flow meter 23 for detecting the intake air amount of the engine is included in a control unit 22 incorporating a microcomputer that controls energization to the electromagnetic brake 13 to control the valve timing of the intake and exhaust valves. Detection signals are input from a crank angle sensor 24 that detects crank rotation, a water temperature sensor 25 that detects engine coolant temperature, and the like.
[0023]
The control unit 22 sets the target valve timing of the intake / exhaust valves based on the engine operating state (rotation speed, load, water temperature, etc.) detected based on the detection signals from the sensors, In order to obtain the target rotational phase of the camshaft corresponding to the target valve timing, the rotational phase is detected on the basis of the signal from the crank angle sensor 24 and the signal from the cam sensor 21, and matches the target rotational phase. Thus, the control current of the electromagnetic brake 13 is controlled.
[0024]
As a configuration according to the present invention, the rate of change of the rotational phase is calculated while estimating the cumulative number of collisions between the stoppers 6b and 8a that regulate the maximum advance angle position of the target valve timing (maximum retard angle position for the exhaust valve). Learning to adjust to an appropriate size.
FIG. 4 shows a flowchart of a routine for setting a target change rate (upper limit value of the change rate) of the rotational phase in accordance with the cumulative number of collisions.
[0025]
In step 1, the actual rotation phase of the cam shaft detected by the cam sensor 21 is set at a position slightly before the maximum advance angle position where the stoppers 6b and 8a abut each other (maximum advance position in consideration of errors). It is determined whether it has passed through a position 2 to 3 degrees smaller than that. Specifically, when the set position is exceeded and then returned to the set position, a decrease in the advance amount of the actual rotational phase is detected and the passage is determined.
[0026]
Then, each time it is determined that it has passed, it is estimated that the stoppers 6b and 8a have substantially collided with each other, and the routine proceeds to step 2 where the collision counter STCNT is counted up. Here, the count value of the collision counter STCNT indicates a cumulative value without being reset after the variable valve timing device starts operation after manufacture.
In step 3, based on the count value of the collision counter STCNT, a target change rate ΔTGVTC of the rotational phase is retrieved and set from a map table set in advance as shown in FIG. Specifically, the maximum target change rate ΔTGVTC is maintained until the first count value reaches a first predetermined value (for example, about 100 times), and when the first set value is reached, the target change rate ΔTGVTC is set to a predetermined amount. Decrease, and when it reaches the next second set value, it decreases in a stepwise manner, such as further decreasing by a predetermined amount. In addition, since the stoppers 6b and 8a are less likely to collide with each other step by decreasing the target change rate ΔTGVTC, the count value (the number of cumulative collisions) until the count value reaches the upper limit setting value (for example, about 250 times). The decrease amount of the target change rate ΔTGVTC with respect to the increase amount of the (estimated value) is increased, but when the upper limit set value is reached, the target change rate ΔTGVTC is not further decreased.
[0027]
FIG. 6 shows a flowchart of a routine for controlling the rotational phase using the target change rate set as described above.
In step 11, the engine speed Ne and the load (for example, the basic fuel injection amount Tp) are read.
In step 12, a basic target rotational phase BTGVTC is calculated based on the engine rotational speed Ne and the load. The basic target rotational phase BTGVTC is a target rotational phase corresponding to the case where the engine operating state determined by the engine rotational speed Ne and the load is a steady state.
[0028]
In step 13, the target change rate ΔTGVTC is read.
In step 14, it is determined whether or not a deviation ΔVTC between the basic target rotation phase BTGVTC and the final target rotation phase TGVTCold calculated last time exceeds the target change rate ΔTGVTC.
When it is determined in step 14 that the deviation ΔVTC exceeds the target change rate ΔTGVTC, the process proceeds to step 15 where the current target rotation phase TGVTC is added to the previous target rotation phase TGVTCold and the target change rate ΔTGVTC is added. Calculated as the value obtained.
[0029]
On the other hand, when it is determined in step 14 that the deviation ΔVTC is equal to or less than the target change rate ΔTGVTC, the basic target rotation phase BTGVTC set in step 11 in step 16 is set as the current target rotation phase TGVTC.
Based on the target rotation phase TGVTC and the actual rotation phase RVTC that are finally set in this manner, the energization of the electromagnetic brake 13 is duty-controlled by PID control or the like.
[0030]
In this way, as shown in FIG. 7, the change rate of the target rotational phase is limited to the target change rate ΔTGVTC or less, and the target change rate ΔTGVTC gradually increases as the estimated cumulative value of the number of stopper collisions increases. Therefore, the overshoot is suppressed, and the collision frequency and collision speed of the stopper are gradually reduced. Thereby, even if there is a manufacturing variation, it is learned that the collision frequency and collision speed of the stopper settle at a predetermined frequency and speed, and it is possible to achieve both a reduction in collision sound and control responsiveness.
[0031]
Further, the cumulative number of collisions of the stopper can be prevented from exceeding a predetermined value within a certain period after the start of use, and the effect that the life of the stopper can be secured is also obtained. As another embodiment of the present invention, it is possible to sequentially estimate the number of stopper collisions per fixed time, that is, the collision frequency, and to set the target change rate according to the collision frequency. The collision sound is reduced in real time while monitoring the ease of collision according to a change in conditions. On the other hand, in the case of learning with the cumulative value, stable control responsiveness and impact noise reduction effect can be obtained from the beginning of operation after learning.
[0032]
Further, when the basic target rotation phase BTGVTC or the actual rotation phase RVTC is at a position far away from the maximum advance angle position where the stoppers 6b and 8a are in contact with each other and does not immediately collide with the stopper, the target change rate A configuration may be adopted in which the responsiveness is improved by changing the rotational phase at a larger change rate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view and a partial side view of a variable valve timing device according to an embodiment.
FIG. 2 is a sectional view showing a schematic configuration in which the function of the variable valve timing device is clarified.
FIG. 3 is a perspective view showing a stopper forming portion of the variable valve timing device.
FIG. 4 is a flowchart of a routine for setting a target change rate of the camshaft rotation phase in the embodiment.
FIG. 5 is a map table for searching for a target change rate of the camshaft rotation phase in the embodiment.
FIG. 6 is a flowchart of a routine for setting a target rotation phase of the camshaft in the embodiment.
FIG. 7 is a time chart showing the operation and effect of the present invention in comparison with the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cam shaft 6b ... Stopper 8a ... Stopper 13 ... Electromagnetic brake 21 ... Cam sensor 22 ... Control unit 24 ... Crank angle sensor

Claims (5)

In a variable valve timing device for an internal combustion engine that variably controls the valve timing by changing the rotational phase of the camshaft relative to the crankshaft by friction braking by an electromagnetic brake,
Adjusted so that the rotational phase of the camshaft changes gradually according to the number of times it reaches a predetermined position near the limit position where the amount of change from the initial position due to the increase in friction braking is regulated by a stopper. A control device for a variable valve timing device. 2. The control of a variable valve timing device according to claim 1, wherein the rotational phase of the cam shaft is adjusted so that the rate of change in operation of the rotational phase decreases as the number of times the rotational phase reaches the predetermined position increases. apparatus. While setting the target change rate of the rotational phase of the camshaft to be decreased as the number of times of reaching the predetermined position is increased, the target rotational phase of the camshaft is periodically calculated and set,
When the difference between the basic target rotational phase calculated based on the current engine operating state and the final target rotational phase calculated last time is within the target change rate, the target rotational phase is set as the basic target Set the rotation phase as the final target rotation phase,
When the difference exceeds the target change rate, the target change rate is added to the final target rotation phase calculated last time and set as the final target rotation phase at this time. The control apparatus of the variable valve timing apparatus of Claim 1 or Claim 2. The variable valve according to claim 3, wherein a table in which the target change rate is set stepwise according to the number of times to reach the predetermined position is provided, and the target change rate is set with reference to the table. Control device for timing device. The control device for a variable valve timing device according to any one of claims 1 to 4, wherein the number of times to reach the predetermined position is a cumulative value.

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