JP3355226B2 - Intake and exhaust valve drive control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake / exhaust valve drive control device for variably controlling the opening / closing timing of intake / exhaust valves according to the operating state of an internal combustion engine.

[0002]

2. Description of the Related Art Various types of conventional intake / exhaust valve drive control devices have been provided, and one of them is disclosed in, for example, Japanese Utility Model Laid-Open No. 57-198306. .

[0005] Referring to FIGS. 11 and 12, a schematic diagram 2 is provided on the outer periphery of a camshaft 1 so as to be relatively rotatable, and an intake valve 16 is opened against a spring force of a valve spring 17. The cam 2 is a single cam to be operated, and the cam 2 is axially positioned by a cam bearing bracket 3 and a flange portion 5 fixed to the cam shaft 1 via a key 4. Also, one side of the cam 2 has a U
While a flange 7 having a groove 6 is formed, a U-shaped groove 8 is also formed in the flange 5, and an annular disk 9 is interposed between the flanges 5 and 7. The disk 9 is provided with pins 10 and 11 that engage with the U-shaped grooves 6 and 8 at opposing positions on both sides, and the outer periphery is rotatably supported by a control ring 12. The control ring 12 is swingably supported by a support hole 13 on the cylinder head side via a projection 12a on the outer periphery, and an arc-shaped gear portion 12b on the opposite side of the projection 12a is pivotally connected to the rocker arm 15. It meshes with a spur gear ring 14 a formed on the outer periphery of the supporting rocker shaft 14.

The control ring 12 swings in one direction or the other according to the operating state of the engine by a drive mechanism (not shown) via a gear ring 14a meshed with the gear portion 12b. That is, for example, when the engine is at high speed and high load, the center P of the disk 9 is held at the position shown in FIG. 11, and the rotation centers of the camshaft 1 and the disk 9 coincide with each other. 8, the cam 2 is rotated in synchronization with the camshaft 1 while the cam 2 is
It rotates synchronously with the camshaft 1 through the groove 6.

When the rocker shaft 14 is rotated by the hydraulic actuator of the drive mechanism at low engine speed and low load, the control ring 12 swings about the projection 12a as a fulcrum via the gear ring 14a and the gear portion 12b. As a result, the center P of the disk 9 is eccentric in the rotation direction with respect to the center of the camshaft 1. Therefore, pins 10 and 11 are
The flange portions 5 and 7 are moved along the grooves 6 and 8 and are rotated about the camshaft 1 in the eccentric direction. Therefore,
For each rotation of the camshaft 1, the rotation phase of the disk 9 changes with respect to the camshaft 1, and at the same time, the rotation phase of the cam 2 also changes with respect to the disk 9. Therefore, cam 2
Rotates with respect to the camshaft 1 with a phase difference of twice the phase difference of the disc 9 with respect to the camshaft 1. As a result, the operating angle of the intake valve 16 is controlled to be small, and in particular, the valve closing timing is controlled to be advanced, so that the combustion efficiency is improved due to the improvement of the intake charge efficiency, and the fuel efficiency and output torque are improved.

[0006]

However, in the above-mentioned conventional apparatus, as described above, by changing the rotational phase difference between the camshaft 1 and the cam 2 according to the engine operating condition, the fuel consumption and output can be reduced. Although the torque can be improved, no consideration is given to improving the fluidity of the intake air in the combustion chamber, that is, the swirl and the like. For this reason, it is impossible to expect the above-mentioned large improvement in combustion efficiency. As a result, the improvement in fuel efficiency and output torque is also limited, and the engine performance cannot be sufficiently improved.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the problems of the above-described conventional intake and exhaust valve drive control device, and has a drive shaft that is rotationally driven by an engine and a coaxial drive shaft. a cam shaft mounted for relative rotation, provided integrally on the outer periphery of the cam shaft, at least a pair of cams operating the intake valves of the small <br/> transfected also a pair per cylinder, the drive A control mechanism for connecting the shaft and the camshaft, and rotating relative to the axis of the drive shaft to change the relative rotation phase between the drive shaft and the camshaft to change the operating angle of the intake valve ; An intake / exhaust valve drive control device for an internal combustion engine having a drive mechanism for rotating the control mechanism in accordance with an operating state, wherein the rising surface of the one-side cam has a steeply inclined shape different from the rising surface of the other-side cam. formed by said by the one side cam one By the other side cam the opening timing of the intake valve
The opening timing of the other intake valve is retarded, and the timing at which the air-fuel mixture flows from each of the intake valves into the combustion chamber at least during the small operation angle control of the two intake valves is different. According to a second aspect of the present invention, the difference between the two cams is provided.
Operating angle of each intake valve based on the profile
It is characterized in that it is controlled to expand.

[0008]

According to the present invention having the above-described structure, the profiles of the two cams are made different, for example, the opening timings of the two intake valves are made different. At the time of control, the intake air flowing into the combustion chamber from the earlier of the valve opening time has directivity,
A relatively strong swirl flow is generated in the combustion chamber.

That is, at the time of the small operation angle control of the valve by the eccentricity control, the rising speed of the valve lift is increased, so that the opening timing of the intake valve is accelerated. Therefore, the preceding intake air generates swirl in the combustion chamber with strong directivity. When the internal pressure of the combustion chamber temporarily decreases due to the opening of the preceding intake valve, the intake valve with the later valve opening timing opens, so that the intake air rapidly flows into the combustion chamber and Interfering with the swirl to generate a stronger swirl. Accordingly, the combustion efficiency can be greatly improved in combination with the small operation angle control of the intake valve.

[0010]

1 to 4 show an embodiment in which an intake / exhaust valve drive control device according to the present invention is applied to the intake side of a multi-cylinder engine.

That is, in the figure, reference numeral 21 denotes a drive shaft which is rotationally driven from a crankshaft of an engine (not shown) via a sprocket, and 22 denotes a drive shaft 21 which is coaxially arranged on the outer periphery of the drive shaft 21 with a certain gap. And a hollow camshaft 23 rotatable relative to the drive shaft 21 and the camshaft 22, a control mechanism connecting the two 21 and 22, 24
Is a drive mechanism for swinging the control mechanism 23.

The drive shaft 21 extends in the front-rear direction of the engine, and is formed hollow inside to reduce the weight.

As shown in FIG. 3, the camshaft 22 is formed at a predetermined position in the longitudinal direction for each cylinder from a direction perpendicular to the axis, and each of the camshafts 22 has a cam bracket 20a, 20a provided at the upper end of the cylinder head 20. And two intake valves 25 and 26 per cylinder are provided at predetermined positions on the outer periphery.
A pair of cams 63, 64, which are opened via valve lifters 62, 62, respectively, against the spring force of the springs 1, 61, are provided integrally.

Each of the cams 63 and 64 has a different profile as shown in FIGS. 1 and 2, and the other cam 64 has a lift rising surface 64a (valve opening side).
And the lift falling surface 64b (valve closing side) is formed in a symmetrical shape about the center line N, whereas the one-side cam 63 is formed in an asymmetrical shape and the lift rising surface 63
a is formed to be steeper than the lift falling surface 63b.

As shown in FIGS. 1 and 4, the control mechanism 23 has a first flange portion 27 integrally provided at one end of each camshaft 22 and a sleeve 28 on a predetermined outer periphery of the drive shaft 21. A second flange portion 32 provided to face the first flange portion 27;
2 and a disk housing 34 that rotatably supports the outer periphery of the annular disk 29 on the inner peripheral surface of the support hole 34a.

As shown in FIG. 5, the first flange portion 27 is formed with an elongated rectangular engaging groove 30 extending in the radial direction from the hollow portion, and has a circumferentially extending outer surface. A protruding surface 27a that slides on one side surface of the annular disk 29 is provided integrally. On the other hand, the second flange portion 32
As shown in FIG. 6, an elongated rectangular engaging groove 33 is formed integrally with the sleeve 28 at the rear end side of the engine, and is formed at a position opposite to the engaging groove 30 by 180 ° along the radial direction. Further, a protruding surface 32a which is in sliding contact with the other side surface of the annular disk 29 is integrally provided on the outer side surface.

As shown in FIG. 3, the sleeve 28 has a small-diameter end 28b rotatably inserted into the other divided end of each camshaft 22 and penetrates diametrically at a substantially central position. And is fixedly connected to the drive shaft 21 via the connection shaft 31.

The annular disk 29 has a substantially donut shape, and has an inner diameter substantially equal to the inner diameter of the camshaft 22, and forms an annular gap S with the outer peripheral surface of the drive shaft 21. In addition, a small-diameter outer peripheral portion is held via a holding member 35 fixed to one side of the disk housing 34. A pair of pins 36 and 37 that engage with the respective engagement grooves 30 and 33 are rotatably inserted into and supported by pin holes 29b and 29c that are formed at opposed positions on the diameter line. The pins 36, 37 project in opposite directions to each other in the camshaft axial direction, and are formed on both side edges of the distal end portion, as shown in FIGS.
Two plane-width flat portions 36a, 36b, 37a, and 37b that are in contact with 0a, 30b, 33a, and 33b are formed.

The disk housing 34 has a substantially annular shape as shown in FIG. 1, and is swingably supported by a support shaft 40 through a pivot hole 38 of a boss 34b provided at one end of the outer periphery. At the same time, a rectangular cam groove 39 is formed on the projection 34c provided on the diametrically opposite side of the boss 34b. In the cam groove 39, a control shaft 42
An eccentric cam 41 provided integrally with the camera is rotatably provided. Therefore, the disk housing 34 swings up and down around the support shaft 40 as the eccentric cam 41 rotates.

As shown in FIG. 4, the support shaft 40 has its base fixed to a fixing hole 43a of a bracket 43 fixed to the upper end of the cylinder head 20. On the other hand, the eccentric cam 41 has its thickness in the circumferential direction gradually changed so that the portion facing the thin portion 41a becomes the maximum thick portion 41b as shown in FIG. 42 from the axis P2. The control shaft 42 extends in the front-rear direction of the engine in parallel with the support shaft 40, a predetermined portion is supported by a bearing (not shown) on the cylinder head 20, and rotation control is performed by the drive mechanism 24. It is supposed to be.

As shown in FIG. 7, the drive mechanism 24 includes a hydraulic actuator 46 provided at one end of the control shaft 42, and a hydraulic circuit 47 for supplying and discharging hydraulic pressure to the hydraulic actuator 46.

The hydraulic actuator 46 includes a cylindrical housing 48 fixed to the cylinder head 20 via a bracket, a two-blade rotary vane 49 rotatably provided in the cylindrical housing 48, Vane 49
And the first oil chambers 50 and 5 located on a diagonal line.
A control shaft 42 is connected to the center of the rotary vane 49.

The hydraulic circuit 47 includes first and second oil chambers 5.
A pair of first and second oil passages 52 for supplying and discharging hydraulic pressure to the first and second oil passages 51 and 52;
a, 52b, a four-port, two-position electromagnetic switching valve 53 provided at an end of the oil passages 52a, 52b, and an oil pump 5 provided at an upstream end of an oil main gallery 54.
5, a drain passage 57 for returning hydraulic oil into the oil pan 56 in appropriate communication with the oil passages 52a and 52b, and a relief valve 58 for controlling the pump discharge pressure to a constant pressure.

Further, the electromagnetic switching valve 53 is switched by an ON-OFF signal from a controller 59 for detecting a current engine operating state based on signals such as an engine speed and an intake air amount. The pump 55 communicates with the first oil passage 52a, the second oil passage 52b communicates with the drain passage 57, and the ON signal turns the communication in reverse.

The operation of this embodiment will be described below.
First, when the engine is running at high speed and high load, an OFF signal is output from the controller 59 to the electromagnetic switching valve 53 so that the first oil chamber 5
Hydraulic oil in the chambers 0 and 50 is discharged from the drain passage 57, and at the same time, oil pressure is fed from the oil pump 55 into the second oil chambers 51 and 51, and the rotary vanes 49 rotate counterclockwise in FIG. Therefore, the eccentric cam 41 also rotates counterclockwise and is held at the position shown in FIG. Thus, the disk housing 34 is also held at the position shown in FIG. 1 around the support shaft 40, and the center Y of the annular disk 29 is
1 coincides with the axis X.

Accordingly, no rotational phase occurs between the annular disk 29 and the drive shaft 21 and the center Y of the camshaft 22 and the center Y of the annular disk 29 coincide with each other. No phase difference occurs. Therefore, the sleeve 28 rotates synchronously with the rotation of the drive shaft 21, and the locking groove 33 of the second flange 32 and the pin 37, the annular disk 29, the pin 36, and the locking groove 30 of the first flange 27 are interposed. The camshaft 22 also rotates synchronously.

Therefore, the intake valves 25, 26
As shown by the solid lines L1 and L2, the operating angle increases, the valve opening timing is advanced, and the valve closing timing is delayed, so that the intake charging efficiency using the intake inertia is improved, and high output can be achieved.

On the other hand, when the engine is at low speed and low load, an ON signal is output from the controller 65 to the electromagnetic switching valve 53, and the hydraulic pressure discharged from the oil pump 55 is applied to the first oil chambers 50, 50.
The hydraulic oil in the second oil chambers 51, 51 is discharged from the drain passage 57 into the oil pan 56. Therefore, the rotating vane 49 rotates clockwise in FIG. 7 to rotate the control shaft 42 in the same direction. Therefore, the eccentric cam 41 rotates clockwise in the drawing from the solid line position to the broken line position shown in FIG. 1 and rotates to the maximum at the θ angle position, and the maximum thickness portion 41b moves to the lower side. Accordingly, the disk housing 34 swings about the support shaft 40 as a fulcrum via the cam hole 39, and the center Y of the annular disk 29 is
It is eccentric from the center X of the (camshaft 22). That is,
When the projection 34c is pulled down with the rotation of the eccentric cam 41, the whole swings downward about the support shaft 40 as a fulcrum and is eccentric by a predetermined amount. Therefore, the second flange portion 32
The sliding position between the locking groove 33 and the pin 37 and the locking groove 30 of the first flange portion 27 and the pin 36 move for each rotation of the drive shaft 21, and the angular velocity of the annular disk 29 changes, resulting in unevenness. It becomes angular velocity rotation.

That is, when the sliding position between the locking groove 30 and the pin 36 approaches the center X of the drive shaft 21, the sliding position between the locking groove 33 and the pin 37 is separated from the center X. In this case, the angular velocity of the annular disk 29 is higher with respect to the drive shaft 21, and the angular velocity of the camshaft 22 is higher with respect to the annular disk 29. Therefore, the camshaft 22 is partially doubled in speed with respect to the drive shaft 21.

As a result, the rotational phase difference between the camshaft 22 and the drive shaft 21 based on the changes in the respective angular velocities is shown in FIG.
B, and the operating angles are indicated by broken lines L3, L in FIG.
The small operation angle is controlled as shown in FIG.

That is, when the angular velocity of the camshaft 22 is relatively high, the rotational phase with respect to the drive shaft 21 advances until the two 21 and 22 become equal in speed. Phase 2
It is delayed until 1 and 22 become uniform speed. The maximum rotational phase difference shown <br/> Suyo in Figure 8 B, the phase point in the middle of the minimum point (P point) is present, the change in the rotational phase shown by the broken line in the figure, P point The valve opening timing of the intake valve 23 before is delayed, the valve closing timing after the point P is advanced, and the operating angle of the valve is reduced as shown by broken lines L3 and L4 in FIG. 8A. Therefore, in the low engine speed and low load range, the opening timing of the intake valve 23 is slightly delayed and the closing timing is advanced. As a result, the valve overlap of the intake and exhaust valves is reduced, the residual gas in the combustion chamber is reduced, and the fuel efficiency can be improved by stable combustion. Further, due to the early valve closing timing, the intake charging efficiency is improved, and the low-speed torque can be increased.

In this embodiment, the rising surface 63a of the one-side cam 63 is formed to be steeper than the falling surface 63b, so that the opening timings of the one-side and the other-side intake valves 25 and 26 are made different. Particularly, at the time of the small operation angle control of the intake valves 25 and 26, a strong intake swirl can be generated in the combustion chamber.

That is, during the small operating angle control of the valve, the valve lift rises sharply as indicated by the broken lines L3 and L4 in FIG. 8A, and the valve is opened first by the other cam 64. The valve opening speed of the other intake valve 26 (on the side of the broken line L3) increases. Therefore, the intake air passing through the other intake valve 26 has a strong directivity in the combustion chamber, and generates a relatively strong swirl in the combustion chamber. In addition, due to the rapid opening of the preceding other-side intake valve 26, the internal pressure of the combustion chamber temporarily drops sharply below the intake pipe internal pressure (dashed line) as shown by the solid line in FIG. 8C. The intake air from the opened one-side intake valve 25 (on the broken line L4 side) rapidly flows into the combustion chamber, and interferes with the preceding intake swirl to generate a stronger swirl. As a result, the combustion efficiency is further improved in combination with the increase in the intake air amount by the two-valve system, and the output torque and the fuel consumption can be greatly improved.

At the time of the small operating angle control, the valve closing timing is advanced, so that the compression start timing in the combustion chamber is advanced and the so-called effective compression ratio is increased. It is effective in improving the fuel efficiency and the like as described above in a low load range.

On the other hand, based on the different profiles of the two cams 63 and 64 as described above, it is also possible to control the operating angles of the intake valves 25 and 26 so as to increase the operating angles. That is, in order to enlarge such an operation angle, the disk housing 34 is swung upward in the drawing as shown by a broken line in FIG. 9 so that the center Y of the disk 29 is positioned with respect to the axis X of the drive shaft 21. This can be done by eccentricity upwards.

The operating angles of the intake valves 25 and 26 are shown in FIG.
By expanding as shown by broken lines L5 and L6 of 0A, the opening timing of the intake valves 25 and 26 is advanced more than at the time of concentric control (solid line in the drawing), and the opening timing of the exhaust valves (valve lift Z) is increased. The valve overlap also increases. At this time, the difference θ1, θ2 between the opening timings of the two intake valves 25, 26 is greatly increased by the eccentricity control. Therefore, due to such eccentricity control, a large valve overlap is formed only in the other intake valve 26, and when the intake valve 26 is opened, the backflow of intake air from the combustion chamber to the intake passage becomes strong. Therefore, 2
Since the flow of one of the intake passages is suppressed by the intake backflow, the difference between the intake inflow speeds between the two intake passages is increased, and the directivity of the intake inflow is enhanced. As a result, a strong swirl is generated in the combustion chamber.

As described above, increasing the operating angle of the valve delays the closing timing of the intake valves 25 and 26 and lowers the effective compression ratio. Suitable for driving range.

In a high-speed, high-load operating range, it is not suitable to increase the operating angle of such a valve. However, if the operating angle of the valve is controlled to a medium level, the operating performance is reduced while ensuring a sufficient swirl. Can be prevented.

Further, in this embodiment, the eccentric disc housing 34, without using the spur gear cormorants good conventional cam 41
The camshaft 22
It is possible to prevent the occurrence of hitting noise, abrasion, etc. due to the alternating load of the disk housing 34 due to the fluctuation of the rotational torque.

Further, as described above, since the pins 36, 37 have both side edges formed on the flat portions 36a, 36b, 37a, 37b, the opposing inner surfaces 30 of the locking grooves 30, 33 are formed.
a, 30b, 33a, 33b in a surface contact state.
Therefore, the plane portions 36a, 36b, 37a, 37b and the inner surfaces 30a, 3a are not rotated when the rotation is transmitted from the drive shaft 21 to the camshaft 22 and the annular disk 29 is eccentric.
When sliding with 0b, 33a, 33b, generation of concentrated load between them is prevented, and the surface pressure is reduced. As a result, the generation of wear over time between the locking grooves 30 and 33 and the pins 36 and 37 is prevented, and the flanges 27 and 32 and the pins 36 and 37 between the flange portions 27 and 32 and the rotation torque of the camshaft 22 change. The occurrence of a tapping sound and a decrease in control accuracy due to a deviation in valve timing are prevented.

[0041]

As is apparent from the above description, claim 1
According to the invention described in the above , particularly, the rising surface of the one-side cam that operates at least a pair of intake valves per cylinder,
The other cam is formed in a shape different from the falling surface of the other cam , and the opening timing of the intake valve by the one cam is set differently by the other cam.
The opening timing of the intake valve is retarded, and at least during the small operating angle control of the two intake valves, the timing at which the air-fuel mixture flows into the combustion chamber from each of the intake valves is changed.
It is possible to generate a strong intake swirl in the combustion chamber during the small operation angle control of both intake valves . As a result, the combustion efficiency in a predetermined engine operating state is further improved in combination with the combustion efficiency by the small operation angle control, and the fuel efficiency and output torque can be further improved. Claim 2
According to the invention, the operating angles of both intake valves are increased.
Therefore, the opening timing of the intake valve is advanced more than the concentric control,
The valve overlap with the exhaust valve also increases. At this time,
The difference between the opening timings of both intake valves is greatly expanded by eccentricity control
I do. Therefore, by such eccentricity control, the other side intake
Because only the valve forms a large valve overlap,
When the intake valve is opened, the intake air from the combustion chamber to the intake passage
Backflow becomes stronger. Therefore, one of the intake passages
Since the flow is suppressed by the flow, the intake flow between each intake passage
The difference in the inflow speed increases, and the directivity of the inflow of intake air increases.
As a result, a strong swirl is generated in the combustion chamber.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along the line AA of FIG. 4 showing one embodiment of the present invention.

FIG. 2 is a front view showing a cam provided in the embodiment.

FIG. 3 is a sectional view of a main part of the embodiment.

FIG. 4 is a plan view of a main part of the embodiment.

FIG. 5 is a sectional view taken along line BB of FIG. 4;

FIG. 6 is a sectional view taken along line CC of FIG. 4;

FIG. 7 is a schematic diagram showing a drive mechanism provided in the embodiment.

8A is a diagram showing a valve lift characteristic of the intake valve of the present embodiment, FIG. 8B is a diagram showing a rotational phase difference between the drive shaft and the camshaft during eccentricity control, and FIG. 8C is a diagram showing the relationship between the pressure in the combustion chamber and the pressure in the intake passage. FIG.

FIG. 9 AA of FIG. 4 showing different eccentric directions of the disc.
Line sectional view.

10A is a valve lift characteristic diagram at the time of the different eccentricity control and at the time of the concentricity control, FIG. 10B is a characteristic diagram of a rotational phase difference between the drive shaft and the camshaft at the time of the same eccentricity control, and FIG. FIG. 3 is a characteristic diagram showing a relationship between the pressure and the intake passage internal pressure.

FIG. 11 is a sectional view of a main part showing a conventional intake and exhaust valve drive control device.

FIG. 12 is a sectional view taken along line DD of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Drive shaft 22 ... Cam shaft 23 ... Control mechanism 24 ... Drive mechanism 25 ... One side intake valve 26 ... The other side intake valve 63 ... One side cam 63a ... Rising surface 64 ... The other side cam 64a ... Rising surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-1707 (JP, A) JP-A-2-256808 (JP, A) JP-A-59-25015 (JP, A) JP-A-1- 159417 (JP, A) Fully open 1983-191336 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01L 13/00 301 F01L 1/08 F02B 31/02 F02D 13/02

Claims (2)

(57) [Claims] A drive shaft driven to rotate by 1. A engine, a camshaft which is provided to be relatively rotatable coaxially of the drive shaft, provided integrally on the outer periphery of the cam shaft, one also less per cylinder At least one pair of cams for operating a pair of intake valves , the drive shaft and the camshaft are connected, and the relative rotation phase between the drive shaft and the camshaft is changed by rotating with respect to the axis of the drive shaft. An intake / exhaust valve drive control device for an internal combustion engine, comprising: a control mechanism for changing an operating angle of the intake valve ; and a drive mechanism for rotating the control mechanism in accordance with an engine operating state. The surface is formed into a steeply inclined shape different from the rising surface of the other cam, and the opening timing of the one intake valve by the one cam is adjusted by the other intake by the other cam.
Wherein the timing at which the air-fuel mixture flows into the combustion chamber from each of the intake valves is made different at least during the small operation angle control of the two intake valves by retarding the valve opening timing. Exhaust valve drive control device. 2. Based on different profiles of said two cams
And control the operating angle of each of the intake valves in a direction to increase the operating angle.
The intake / exhaust valve for an internal combustion engine according to claim 1, wherein
Drive control device.