JP3635911B2 - Catalyst temperature controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst temperature control device that makes the temperature of a catalyst provided in an exhaust system of an internal combustion engine suitable for operating conditions, and in particular, a variable valve timing mechanism that moves an opening period of an intake valve and / or an exhaust valve. And a catalyst temperature control device in an engine in which an overlap period in which both an intake valve and an exhaust valve are open is made variable.
[0002]
[Prior art]
An engine having a so-called variable valve timing mechanism that changes an opening / closing period of an intake valve or an exhaust valve according to an operating condition is known. And when the engine is cold, both the intake valve and the exhaust valve are open. So-called overlap period is expanded to burn after combustion in the combustion chamber to promote activation of the catalyst disposed in the exhaust system. Devices for doing this are known.
[0003]
For example, in the apparatus disclosed in Japanese Patent Application Laid-Open No. 5-59936, the activation of the catalyst is promoted by delaying the closing timing of the exhaust system and extending the overlap period of the exhaust valve and the intake valve when cold. ing. Further, in the apparatus disclosed in Japanese Patent Laid-Open No. 5-21001, when the engine is cold, the valve opening overlap period of the exhaust valve and the intake valve is increased, the ignition timing is retarded, and the activation of the catalyst is promoted.
[0004]
[Problems to be solved by the invention]
However, the idea of the invention of each of the above publications is that the exhaust period is mixed into the new air-fuel mixture by increasing the overlap period, so-called internal EGR is increased, and the combustion speed is delayed. It tries to raise the temperature.
However, only by extending the overlap period, much of the energy of the exhaust gas that has risen as described in the above publication is transmitted to the coolant through the cylinder head. As a result, there is a problem that it does not act effectively on the rise of the catalyst inlet gas temperature for the purpose of catalyst activation.
Accordingly, an object of the present invention is to provide a catalyst temperature control device that can reliably increase the exhaust gas temperature and promote the warm-up of the catalyst when cold.
Further, such an extension of the overlap period may induce overheating of the catalyst after warming up, but there is a problem that this point is not taken into consideration, so it prevents overheating of the catalyst after warming up. This is also an object of the present invention.
[0005]
[Means for Solving the Problems]
  According to the invention of claim 1, the valve overlap period is changed according to the operating state.Possible valve characteristic control deviceA catalyst temperature control device for controlling the temperature of a catalyst disposed in an exhaust system of an engine comprising:
  InstitutionMeans for determining whether it is necessary to promote catalyst activation depending on whether it is in a predetermined temperature range and whether it is in a predetermined rotation speed and load range;
  Means for activating the valve characteristic control device to expand the overlap period when it is determined that promotion of catalyst activation is necessary;
  During extended valve overlapInstitutionalMake the pressure in the exhaust port negativeExhaust pressure lowering means for lowering the pressure in the exhaust port;
  ExpansionBy means of exhaust pressure reduction during a large valve overlap periodNegative pressureThe pressure in the intake port is higher than the pressure in the exhaust portTo becomeThe pressure in the intake portIncrease,Intake pipe pressure increasing means for blowing the sucked air-fuel mixture into the exhaust pipe;
  An output increase suppressing means for suppressing an increase in engine output by the intake pipe pressure increasing means,
  When it is judged that promotion of catalyst activation is necessaryThere is provided a catalyst temperature control device that promotes activation of a catalyst by blowing fuel and air into the exhaust pipe and combusting in the exhaust pipe while suppressing an increase in output.
  In the catalyst temperature control device configured in this way,When it is determined that catalyst activation needs to be promoted, the valve overlap period is expanded andThe intake port pressure is made higher than the exhaust port pressure, and the sucked air-fuel mixture is blown into the exhaust pipe to promote the activation of the catalyst. Increase is suppressed.
[0006]
  According to the invention of claim 2, in the invention of claim 1, the intake pipe pressure increasing means is the intake pipe throttle.OpeningIncrease the intake pipe throttleOpeningA catalyst temperature control device which is an increasing means is provided.
  In the catalyst temperature control apparatus configured in this way, the intake pipe throttleOpeningAs a result, the intake port pressure is increased, and the intake air mixture is blown into the exhaust pipe.
[0007]
According to the invention of claim 3, in the invention of claim 1, the output increase suppressing means is an ignition timing adjusting means, and the ignition timing is adjusted so as to suppress an increase in engine output due to the increase adjustment of the intake pipe pressure. A catalyst temperature control device for adjusting the temperature is provided.
In the catalyst temperature control apparatus configured as described above, the ignition timing adjusting means adjusts the ignition timing so that the engine output due to the increase adjustment of the intake pipe pressure is suppressed.
[0008]
  According to the invention of claim 4, in the invention of claim 1, the output increase suppression means isThe overlap period is expanded so that the output does not increase.A catalyst temperature control device is provided.
  With the catalyst temperature control device configured in this wayOh-Extend the burlap periodTo suppress the increase in engine outputTherefore, it is not necessary to separately provide an output increase suppressing means.
[0009]
  According to the invention of claim 5, in the invention of claim 1,Valve characteristic control device attached to the exhaust camshaft and valve characteristic control device attached to the intake camshaftAnd bothChanging the valve overlap periodA catalyst temperature control device is provided.
  In the catalyst temperature control device configured in this way,A valve characteristic control device attached to the exhaust camshaft and a valve characteristic control device attached to the intake camshaft;Change both and overlapperiodIs enlarged.
[0010]
  According to the invention of claim 6, in the invention of claim 1,A valve characteristic control device attached to the exhaust camshaft, a valve characteristic control device attached to the intake camshaft,Either one ofTo change the valve overlap periodA catalyst temperature control device is provided.
  In the catalyst temperature control device configured in this way,A valve characteristic control device attached to the exhaust camshaft and a valve characteristic control device attached to the intake camshaft;Overlap by either one ofperiodIs enlarged.
[0011]
According to the invention of claim 7, in the invention of claim 1, the length of the exhaust pressure reducing means is optimized so as to return to the exhaust port during the valve overlap period in which the negative pressure wave due to exhaust pulsation is expanded. A catalyst temperature control device that is the exhaust pipe itself is provided.
In the catalyst temperature control apparatus configured as described above, the length of the exhaust pipe is set back to the exhaust port during the valve overlap period in which the negative pressure wave due to the exhaust pulsation is expanded.
[0012]
  According to the invention of claim 8, in the invention of claim 1,The exhaust port pressure lowering means connects two collective exhaust manifolds, each of which collects a single exhaust manifold, with a communication pipe, and provides an exhaust control valve on the communication pipe.Adjusted to return to the exhaust port during the valve overlap period when the negative pressure wave due to exhaust pulsation is expandedConsist ofA catalyst temperature control device is provided.
  In the catalyst temperature control device configured in this way,Two exhaust manifolds, each of which is a single exhaust manifold, are connected by a communication pipe, an exhaust control valve is provided in the communication pipe, and the exhaust control valve isAdjust so that the negative pressure wave due to exhaust pulsation returns to the exhaust port during the valve overlap period.The exhaust port pressure is reduced.
[0013]
According to the invention of claim 9, in the invention of claim 1, there is further provided a catalyst temperature control device provided with a catalyst overheat preventing means for preventing overheating of the catalyst due to the expansion of overlap after warm-up.
In the catalyst temperature control device configured as described above, the catalyst overheat prevention means prevents the catalyst from overheating due to the increased overlap after warm-up.
[0014]
According to the invention of claim 10, in the invention of claim 9, when the catalyst overheat prevention means reaches a condition where the catalyst overheat is expected, fuel is injected while the exhaust valve is closed and the intake valve is open. Thus, there is provided a catalyst temperature control device as fuel injection timing adjusting means for adjusting the fuel injection timing.
In the catalyst temperature control apparatus configured as described above, the fuel injection timing is adjusted by the fuel injection timing adjusting means, and the fuel injection timing is adjusted so that the fuel is injected while the intake valve is open. Is prevented from overheating.
[0015]
According to the eleventh aspect of the present invention, in the tenth aspect of the present invention, when the fuel injection time is long and the fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjusting means, the exhaust valve A catalyst temperature control device is provided in which the valve closing timing is advanced so that the overlap is shortened and fuel blow-off is prevented.
In the catalyst temperature control apparatus configured as described above, when the fuel injection time is long and fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjusting means, the closing timing of the exhaust valve This shortens the overlap and prevents the catalyst from overheating.
[0016]
According to the twelfth aspect of the present invention, in the tenth aspect of the invention, when the fuel injection time is long and fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjusting means, the fuel injection is performed. There is provided a catalyst temperature control device which shortens the time and prevents the fuel from being blown out.
In the catalyst temperature control apparatus configured as described above, the fuel injection time is shortened when the fuel injection time is long and the fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjusting means. This prevents overheating of the catalyst.
[0017]
  According to the invention of claim 13, in the invention of claim 9, the overlap occurs when the catalyst overheating reaches an expected condition.PeriodExpansionDrivingEscape from the areaChange the operating conditions to prevent overheating of the catalyst,A catalyst temperature control device is provided.
  With the catalyst temperature control device configured in this way, when the catalyst overheating reaches the expected condition.In-BurlapPeriodExpansionBe doneIt escapes from the area and prevents overheating of the catalyst.
[0018]
According to the invention of claim 14, in the invention of claim 9, the post-warming-up catalyst overheat prevention means is a port that makes the pressure of the exhaust port higher than the pressure of the intake port when a condition where the catalyst overheat is expected is reached. A catalyst temperature control device serving as an intermediate pressure adjusting means is provided.
In the catalyst temperature control device configured as described above, when the catalyst overheating is expected, the pressure of the exhaust port is made higher than the pressure of the intake port by the inter-port pressure adjusting means to prevent overheating of the catalyst. .
[0019]
According to the fifteenth aspect of the invention, in the thirteenth aspect of the invention, the inter-port pressure adjusting means reduces the throttle opening in order to reduce the intake port pressure when the catalyst overheating is expected. There is provided a catalyst temperature control device as an opening reduction means.
In the catalyst temperature control device configured as described above, when the catalyst overheating is expected, the throttle opening is reduced by the throttle opening reduction means to prevent the catalyst from being overheated.
[0020]
  According to the invention of claim 16, in the invention of claim 14, the inter-port pressure adjusting means connects two collective exhaust manifolds, each of which collects a single exhaust manifold, with a communication pipe,An exhaust control valve is provided in the communication pipe, and the exhaust control valveWhen the catalyst overheating reaches the expected condition,Close controlExhaust portThe pressure of the positive pressureA catalyst temperature control device is provided.
  In the catalyst temperature control apparatus configured in this way, two collective exhaust manifolds each collecting a single exhaust manifold are connected by a communication pipe,An exhaust control valve is provided in the communication pipe, and the exhaust control valveWhen the catalyst overheating reaches the expected condition,Close controlExhaust portSet the pressure to positiveThe pressure between the ports is adjusted.
[0021]
  According to the invention of claim 17, in the invention of claim 14, the inter-port pressure adjusting means isA back pressure control valve is provided at the rear end of the exhaust pipe, and the back pressure control valve isWhen catalyst overheating reaches the expected conditions,Closed control at the time of overlap, the exhaust port pressure is made positive pressureA catalyst temperature control device is provided.
  In the catalyst temperature control device configured in this way, when the catalyst overheating reaches the expected condition,The back pressure control valve provided at the rear end portion of the exhaust pipe is closed and closed at the time of overlap so that the pressure of the exhaust port becomes positive.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the overall structure of the first embodiment of the present invention.
Intake air is supplied to an intake port (not shown) of the engine 1 via an intake pipe 2, a surge tank 3, and an intake manifold 4. An air cleaner 5, an air flow meter 211, and an electronic throttle 251 are disposed in the intake pipe 2. A fuel injection valve 252 is attached to the intake manifold 4 for each cylinder.
[0023]
The electronic throttle 251 changes the throttle opening according to the amount of depression of an accelerator pedal (not shown). In particular, in the present invention, as will be described later, an intake valve (not shown) and an exhaust valve (not shown). ), The opening degree is increased regardless of the depression amount of the accelerator pedal so that the pressure in the intake pipe becomes higher than the pressure in the exhaust pipe.
[0024]
On the other hand, an exhaust manifold 6 is attached to an exhaust port (not shown) of the engine 1. Here, the order of ignition of this engine is the order of # 1 cylinder → # 3 cylinder → # 4 cylinder → # 2 cylinder. On the other hand, as shown in FIG. And # 4 cylinders, # 2 cylinders and # 3 cylinders are once gathered in equal length, and further gathered into one. The length is optimized so that the exhaust port is at a negative pressure during the overlap period.
[0025]
A catalyst 8 is disposed in an exhaust pipe 7 connected downstream of the exhaust manifold 6. An air-fuel ratio sensor 215 is disposed upstream of the catalyst 8, and based on the signal from the air-fuel ratio sensor 215, the fuel injection amount of the fuel injection valve 252 is feedback controlled so that the catalyst 8 optimally performs a purification action. Is done. An igniter-integrated spark plug 253 is provided for each cylinder of the engine 1.
Reference numeral 300 denotes an automatic shift, and reference numeral 310 denotes a shift control mechanism according to a first modification of the first embodiment of the present invention to be described later.
[0026]
In addition to the airflow meter 211 described above, the engine 1 includes a crank position sensor 212 that detects the angular position of the crankshaft, a water temperature sensor 213 that detects the cooling water temperature of the engine, Sensors such as cam angle sensors 214, 214 ′ for detecting the phases of the intake camshaft 50 and the exhaust camshaft 50 ′ are arranged, and signals from these sensors are sent to an electronic control unit (ECU) 200.
[0027]
The air flow meter 211 generates a signal voltage corresponding to the intake air amount GA as a load.
The details of the structure of the crank position sensor 212 are omitted. Occur. The projections of the signal generating disk are provided every 10 °, but there are 34 protrusions because they are missing two teeth. For example, since the missing tooth portion is provided at a predetermined angular position with respect to the top dead center of the first cylinder, the top dead center can be accurately obtained from a signal generated by the missing tooth portion. The signal generated every 10 ° is further divided so that the crank angle from the top dead center at the time of measurement can be accurately determined.
[0028]
The engine water temperature sensor 213 generates a signal corresponding to the cooling water temperature TW of the engine 1.
The intake cam angle sensor 214 and the exhaust cam angle sensor 214 'generate a signal voltage each time the electromagnetic pickup passes in close proximity to the signal generation protrusion provided at an appropriate location on the camshaft. This projection generates a signal once per camshaft rotation, ie once per two crankshaft rotations. This protrusion is provided so as to generate a signal at the time of maximum lift of the cam crest of the first cylinder, for example.
[0029]
The ECU 200 is a digital computer including an input interface 210, a central processing unit (CPU) 220, a random access memory (RAM) 230, a read only memory (ROM) 240, and an output interface 250 that are connected to each other.
The CPU 220 of the ECU 200 performs calculations related to the present invention, which will be described later, from the signals of each sensor input to the input interface 210, data stored in the ROM 240, and the like, and outputs the electronic throttle 251, spark plug 253, It outputs to the below-mentioned valve characteristic control apparatuses 100 and 100 ', and performs control of the present invention.
[0030]
Further, in order to change the phase of the valve opening period of the intake valve (not shown) and the phase of the valve opening period of the exhaust valve (not shown), the vane type valve characteristic control devices 100 and 100 ′ having the same structure are provided. These are attached to the intake camshaft 50 and the exhaust camshaft 50 ′.
Therefore, hereinafter, the valve characteristic control device 100 attached to the intake camshaft 50 will be described as an example.
[0031]
FIG. 2 is a cross-sectional view of the vane type valve characteristic control device 100 attached to the intake camshaft 50 taken along a plane passing through the central axis X of the intake camshaft 50.
Referring to FIG. 2, a gear 10 driven by a crankshaft (not shown) through a chain (not shown) at a half rotation ratio cooperates with the gear 10 to advance an oil chamber 110 and retard. The housing 20 forming the oil chamber 120 and the side cover 30 are fixed by B1 (only one of the four is shown). A rotor 40 is disposed inside the housing 20 so as to be rotatable by a predetermined angle. The rotor 40 is fixed to the intake camshaft 50 with a bolt B2.
[0032]
FIG. 3 is a view of the valve characteristic control device 1 as viewed from the shaft end side (left side in FIG. 1) with the side cover 30 and the bolts B1 and B2 removed.
As shown in FIG. 3, the housing 20 includes an outer peripheral portion 21 and four inner protrusions 22. A seal member 23 is disposed on the inner peripheral side of the inner protrusion 22. Reference numeral 24 denotes a hole through which the bolt B1 passes. In FIG. 2, the housing 20 is shown with an outer peripheral portion 21 and an inner projection 22 together with the seal member 23 above the center axis X of the intake camshaft 50, and below the center axis X of the intake camshaft 50. The housing 20 shows an outer peripheral portion 21, and a broken line 20 ′ is a boundary between the outer peripheral portion 21 and the inner protruding portion 22.
[0033]
As shown in FIG. 3, the rotor 40 includes a boss 41 and four vanes 42 protruding radially outward therefrom. A seal member 43 is disposed on the outer peripheral side of each vane 40. In FIG. 2, the rotor 40 shows only the boss 41 above the center axis X of the intake camshaft 50, and the boss 41 and the vane 42 are integrally sealed below the center axis X of the intake camshaft 50. It is shown together with the member 43, and a broken line 40 ′ is the boundary between the boss 41 and the vane 42.
The boss 41 of the rotor 40 has two slopes for guiding the hydraulic oil that has passed through the camshaft advance oil passage 55 to the central oil chamber 44 formed around the bolt B <b> 2 at the center of the boss 41. Four distribution oil passages 46 are formed between the oil passage 45 and the central oil chamber 44 and are introduced between the vane 42 of the rotor 40 and the inner protrusion 22 of the housing 20 and into the advance oil chamber 110. Is formed.
[0034]
Returning to FIG. 2 and paying attention to the intake camshaft 50, the intake camshaft 50 is connected to the cylinder head 70 and the cam between the outer flange 51 and the inner flange 52 via a halved upper metal bearing 60A and lower metal bearing 60B. The cap 80 is rotatably supported. Between the outer flange 51 and the inner flange 52, an annular advance oil passage 53 is formed closer to the inner flange 52, and an annular retard oil passage 54 is formed closer to the outer flange 52.
The annular advance oil passage 53 communicates with a camshaft advance oil passage 55 formed in parallel to the central axis X via a short oil passage 55a. The camshaft advance angle oil passage 55 communicates with the inclined oil passage 45 of the rotor 40.
The annular retard oil passage 54 communicates with a camshaft retard oil passage 56 formed in parallel to the central axis X via a short oil passage 56a. The camshaft advance angle oil passage 56 communicates with a shaft end side annular retard oil passage 57 provided on the shaft end side with respect to the outer flange 51.
The shaft-end-side annular retard oil passage 57 communicates with the retard oil chamber 120 via an in-gear annular oil passage 11 and an in-gear distribution oil passage 12 provided on the inner peripheral side of the gear 10.
[0035]
On the other hand, the cylinder head 70 is fitted with an oil control valve 90 that controls the supply of hydraulic oil to each oil chamber.
FIG. 4 shows details of the oil control valve 90. As shown in FIG. 4, the oil control valve 90 moves the spool valve 95 in the sleeve 91 by the plunger 93 and the spring 94 of the electromagnetic solenoid 92 to switch the flow direction of the hydraulic oil.
[0036]
The sleeve 91 has an advance port 91a, a retard port 91b, a supply port 91c, and drain ports 91d and 91e. On the other hand, the spool valve 95 has four lands 95a, 95b, 95c, and 95d and three groove passages 95e, 95e, and 95f.
The electromagnetic solenoid 92 is excited by duty control in response to a signal from an electronic control unit (hereinafter referred to as ECU) 200. By changing the duty ratio of the electromagnetic solenoid 92, the position of the spool valve 95 is changed to advance the hydraulic oil advance angle oil chamber 110, the delay time. Controls the supply and discharge to the corner oil chamber 120.
[0037]
For example, when excited at a duty ratio of 100%, the spool valve 95 moves to the leftmost side, the advance port 91a is fully opened and communicated with the supply port 91c, and the retard port 91b is fully opened and communicated with the drain port 91e. The hydraulic oil is supplied to the advance angle oil chamber 110 of the control device 100 with the maximum capacity, the hydraulic oil is discharged from the retard angle oil chamber 120 with the maximum capacity, and the intake camshaft 50 advances at the maximum speed with respect to the crankshaft. Move in the angular direction.
When the duty ratio is 0% (not energized), the spool valve 95 moves to the rightmost side so that the supply port 91c and the retard port 91b are fully opened and the advance port 91a is communicated with the drain port 91d. The hydraulic oil is supplied to the retard oil chamber 120 of the valve characteristic control device 100 with the maximum capacity, the hydraulic oil is discharged from the advance oil chamber 110 with the maximum capacity, and the intake camshaft 50 is maximum with respect to the crankshaft. Move in the retard direction at speed.
FIG. 4 shows a state in which the supply port 91c and the retard port 91b are fully opened and communicated.
[0038]
On the other hand, the engine 1 has a cam angle sensor 222 that detects a phase difference between the intake camshaft 50 and the crankshaft (see FIG. 1), and the phase difference between the intake camshaft 50 and the crankshaft becomes a predetermined phase difference. Then, the electromagnetic solenoid 92 is excited at an intermediate duty ratio, and the spool valve 95 blocks communication between the advance port 91a, the supply port 91c, and the drain port 91d by the lands 95a, 95b, 95c, and 95d. The intake camshaft 50 maintains its phase difference with respect to the crankshaft, stopping at positions where the communication between the supply port 91c and the supply port 91c and the drain port 91d is blocked.
[0039]
In FIG. 2, reference numeral 71 denotes an advance angle oil passage in the cylinder head for communicating an advance angle port 91 a of the oil control valve 90 and an annular advance oil passage 53 formed in the intake camshaft 50. Reference numeral 72 denotes a retarding oil passage in the cylinder head for communicating a retarding port 91b of the oil control valve 90 and an annular retarding oil passage 54 formed in the intake camshaft 50.
Similarly, reference numeral 73 in FIG. 2 denotes a supply oil passage for communicating an oil pump (not shown) with a supply port 91c of the oil control valve 90, and reference numeral 74 denotes a drain port of the oil control valve 90. It is a drain oil passage for communicating 91d and 91e and an oil pan.
[0040]
FIG. 5 is a cross-sectional view taken along line 4-4 of FIG. 2, and the communication between the annular advance oil passage 53 and the cylinder head advance oil passage 71, and the annular retard oil passage 54 and the cylinder. The communication with the in-head retard oil passage 72 is shown.
As shown in FIG. 4, the cylinder head internal advance oil passage 71 extends upward from the advance port 91 a of the oil control valve 90 toward the cam cap 80 and penetrates the upper surface 76 of the cylinder head 70. A groove 82 is formed in the lower surface 81 of the cam cap 80 so as to connect the cylinder head inward advance oil passage 71 and the outer side of the upper bearing metal 60A. On the other hand, a hole 61 is formed in the upper bearing metal 60 </ b> A, and the diameter of the hole 61 is set larger than the width of the annular advance oil passage 53. An inclined oil passage 83 is formed so as to communicate the groove 82 with the hole 61 and the lower surface 81 of the cam cap 80. FIG. 5 is an exploded view of the upper bearing metal 60A and the cam cap 80, showing the above configuration in an easy-to-understand manner.
[0041]
On the other hand, the retarded oil passage 72 in the cylinder head extends upward from the advance port 91a of the oil control valve 90 toward the cam cap 80, but bends in the middle and reaches the opening 72a outside the lower bearing metal 60B. ing.
Here, referring to FIG. 6 in which the structure of the lower bearing metal 60B and the cylinder head 70 is shown in an exploded view, a cross-sectional crescent-shaped groove 78 having a width larger than the diameter of the opening 72a is formed from the opening 72a. It is formed in the semicircular cross-section receiving part 77 of the cylinder head 70 that receives the lower bearing metal 60B in the axial direction.
[0042]
On the other hand, in the lower bearing metal 60B, a notch 62 is formed at a corner where the flange portion 60F rises. The size when the notch is viewed from the axial direction is at least larger than the crescent-shaped cross section of the groove 78, and the width when the notch is viewed from the direction perpendicular to the axis is the annular shape of the intake camshaft 50 inscribed in this portion. It is larger than the width of the retard oil passage 54.
[0043]
Accordingly, the hydraulic oil for advancement passes from the advance port 91a of the oil control valve 90 through the oil passage 71 in the cylinder head, the groove 82 of the cam cap 80, the inclined oil passage 83, and the hole 61 of the upper bearing metal 60A. It reaches the annular advance oil passage 53 of the intake camshaft 50. From the annular advance oil passage 53, it passes through the short communication oil passage 55a, enters the camshaft advance oil passage 55, proceeds in the axial direction, reaches the central oil chamber 44 through the inclined oil passage 45 of the rotor 40, From there, the oil is distributed to each advance oil chamber 110 through a distribution oil passage 46.
[0044]
Further, the hydraulic oil for retarding angle is formed from the retarding port 91b of the oil control valve 90 to the oil passage 72 in the cylinder head, and from an oil passage 79 formed between the crescent-shaped groove 78 and the back surface of the lower bearing metal 60B. Enters the shaft end direction, and reaches the annular retarded oil passage 54 of the intake camshaft 50 through a notch 62 formed at the corner of the shaft end of the lower bearing metal 60B. From the annular retarding oil passage 54, the camshaft retarding oil passage 56 enters the camshaft retarding oil passage 56 through the short connecting oil passage 56 a, proceeds in the axial direction, passes through the short connecting oil passage 56 b, and the shaft end side annular retarding oil passage 57. To reach. From there, it enters the inclined distribution oil passage 12 through the annular oil passage 11 formed in the gear 10 so as to face the shaft end side annular retardation oil passage 57, and is distributed to each retardation oil chamber 120.
[0045]
Hereinafter, the control of the first embodiment of the present invention configured as described above will be described.
Here, in the first embodiment, the overlap amount is increased and adjusted under a predetermined operating condition set in advance, and the throttle opening is increased to increase the intake pipe negative pressure to bring the air-fuel mixture into the exhaust pipe. It introduces and burns the air-fuel mixture in the exhaust pipe to promote the activation of the catalyst.
Also, in order to prevent the fuel from reaching the catalyst without being burned due to blow-through when the overlap is expanded after the engine is warmed up, the throttle opening is decreased and the intake port pressure is made lower than the exhaust port pressure. Have been to.
[0046]
Hereinafter, the details of the control of the catalyst activation will be described. The flowchart of FIG. 6 is for determining whether or not catalyst activation promotion is necessary.
In step 61, each parameter is read. In step 62, the engine coolant temperature TW is compared with a predetermined determination value TWA to determine whether it is necessary to promote the activation of the catalyst. Then, it is determined from the engine speed whether the catalyst needs to be activated. If the determination in both steps 62 and 63 is affirmative, the activation of the catalyst should be promoted, and the flag FCC is set to 1 in step 64. If the determination in step 62 or 63 is negative, the catalyst Since activation promotion is unnecessary, the flag FCC is set to 0 in step 65 and the process is terminated.
[0047]
FIG. 7 is a map for determination in step 63. One of the areas shown in FIG. 7 is that the intake pipe pressure is too low at the idle and light loads near the idle, and cannot exceed the exhaust port pressure. This is because this control includes control to suppress the output, so that it is not performed in the high load region where the output is required.
[0048]
FIG. 8 (a) is a flowchart for expanding the overlap executed when it is determined in the flowchart of FIG. 6 that catalyst activation promotion should be executed, and FIG. 8 (a) is a flowchart for increasing the throttle opening degree. FIG. 8 (c) shows a flowchart for executing the retarding of the ignition timing for suppressing the increase in output due to the increase in the throttle opening in b). Each control is executed when the flag FCC is determined to be 1.
[0049]
  Next, (aThe enlargement of the overlap amount shown in the flowchart of FIG. For example, the overlap amount is increased from the state shown in FIG. 9A to the state shown in FIG. 9B. For this purpose, it is necessary to shift the opening period of the intake valve to the advance side and simultaneously shift the exhaust valve opening period to the retard side. Therefore, the rotational phases of the intake camshaft 50 and the exhaust camshaft 50 'are moved to the advance side and the retard side, respectively. This movement of the camshaft is performed by feedback control while detecting the phases of the intake camshaft 50 and the exhaust camshaft 50 'by the crank position sensor 212, the intake cam angle sensor 214, and the exhaust cam angle sensor 214'.
[0050]
The current phases of the intake camshaft 50 and the exhaust camshaft 50 'are determined based on signals from the crank position sensor 212 and signals from the intake cam angle sensor 214 and the exhaust cam angle sensor 214'. As a parameter representing this phase, the crank angle from the compression top dead center of the # 1 cylinder to the time when the intake cam angle sensor 214 and the exhaust cam angle sensor 214 ′ generate a signal, that is, the maximum lift time of the cam of the # 1 cylinder. calculate. As described above, the compression top dead center is obtained as a point where a predetermined crank angle has passed after the crank position sensor 212 generates a missing tooth signal.
[0051]
On the other hand, the ROM 240 of the ECU 200 stores the phases of the intake camshaft 50 and the exhaust camshaft 50 ′ for making the overlap large, medium, and small as shown in FIG. 10 and promotes the activation of the catalyst. When doing so, the phase which makes the overlap large is used, and the overlap is made large as shown in FIG.
Normally, the vehicle is operated with a predetermined overlap according to the operating conditions. For example, the overlap is changed according to the load (see FIG. 18) or the speed is changed according to the rotational speed (see FIG. 19), as will be described later regarding prevention of overheating of the catalyst after warm-up.
The map in FIG. 10 has the same parameters as those used for the above-described camshaft phase measurement, that is, the intake cam angle sensor 214 and the exhaust cam angle sensor 214 ′ are signals from the compression top dead center of the # 1 cylinder. Is stored at the crank angle up to the point of time of occurrence, that is, the maximum lift point of the # 1 cylinder cam.
[0052]
If the measured camshaft phase is delayed with respect to the target camshaft phase value obtained from the map, a command to send an excitation current with a duty ratio of 100% to the electromagnetic solenoid 92 of the oil control valve 90 is issued. Then, the hydraulic fluid flows into the advance oil chamber 110 of the valve timing control device 100 so that the phase of the camshaft is advanced to approach the target phase. Conversely, when the measured camshaft phase has advanced relative to the camshaft target phase value obtained from the map, a command to demagnetize the electromagnetic solenoid 92 of the oil control valve 90 is issued, and the valve timing control device The hydraulic oil flows into the 100 retard oil chamber 120 so that the phase of the camshaft is delayed to approach the target phase. When the camshaft phase matches the target value, an intermediate duty ratio excitation current is sent to maintain the phase.
[0053]
FIGS. 11 and 12 show valve housings 20 and 20 ′ of the valve characteristic control devices 100 and 100 ′ when the phase of the intake camshaft 50 is most advanced and the phase of the intake camshaft 50 ′ is most retarded, respectively. This shows the relative positional relationship between the inner projections 22 and 22 'and the vanes 42 and 42' of the rotors 40 and 40 '.
In each figure, the housing 20, 20 'rotor 40, 40' rotates clockwise as indicated by the arrow in the figure. In each figure, only a minimum number of symbols is shown for easy viewing.
[0054]
First, as shown in FIG. 11, when the phase of the intake camshaft 50 is most advanced, the electromagnetic solenoid 92 of the oil control valve 90 is excited with a duty ratio of 100% and the operation introduced as shown by the thick broken arrow. The advance oil chamber 110 is filled with oil, and all the hydraulic oil in the retard oil chamber 120 is discharged, and then the duty ratio is set to an intermediate value and the state is maintained.
[0055]
On the other hand, when the phase of the intake camshaft 50 'is most retarded as shown in FIG. 12, the electromagnetic solenoid 92' of the oil control valve 90 'is demagnetized, and the hydraulic oil introduced as shown by the thick dashed arrow Then, the retard oil chamber 120 'is filled, and all the hydraulic oil in the advance oil chamber 110' is discharged, and then the duty ratio is set to an intermediate value and the state is maintained.
[0056]
The oil control valves 90 and 90 'open the advance ports 91a and 91a' only after exciting the electromagnetic solenoids 92 and 92 'to a duty ratio of 100%, and the retard port 91b only after 0% (demagnetization). , 91b 'is not open, it is lower than 100% or higher than 0%, starts gradually opening from the duty ratio, reaches the maximum opening at 100%, 0% (demagnetization) , It is not always necessary to be 100% or 0%. Rather, if control is always performed at 100% and 0%, it is not desirable because overshoot occurs and it takes time to reach the target phase. Thus, in this embodiment, the duty ratio is changed according to the difference from the target phase, but the details are omitted.
[0057]
Next, the increase in the throttle opening in FIG. 8B will be described. As described above, in this engine, the length of the exhaust manifold 6 is optimized so that the pressure Pe of the exhaust port becomes negative during the overlap period. Therefore, the throttle opening of the electronic throttle 251 is set so that the pressure of the intake port Pi is higher than the pressure of the exhaust port, that is, the negative pressure value of the intake port is larger than the negative pressure value of the exhaust port. Change to an increased value. FIG. 13 is a diagram for explaining the above idea. The increased value of the aperture of the throttle is also stored in the ROM 240 of the ECU 200.
[0058]
Next, the ignition timing retardation in FIG. 8C will be described. This retarding of the ignition timing suppresses the increase in output due to the increase in the throttle opening described above, but also has the effect of facilitating the combustion of the air-fuel mixture blown through the exhaust pipe, which has the effect of delaying the combustion period. The retarded ignition timing is also stored in the ROM 240 of the ECU 200.
[0059]
FIG. 14 is a time chart for explaining the above control, and FIG. 15 is a diagram showing a state in which the air-fuel mixture blows from the intake port to the exhaust port by the control of FIG. 6 and burns in the exhaust port. In this way, the air-fuel mixture blows from the intake port to the exhaust port and burns in the exhaust port or the exhaust pipe, so that the activation of the catalyst 8 is promoted.
[0060]
Next, in the first embodiment, the throttle opening is decreased to prevent the catalyst from being overheated due to the blow-through when the overlap is expanded after the engine is warmed, and the intake port is reduced to prevent the catalyst from overheating. The control for making the pressure lower than the exhaust port pressure will be described. 16 and 17 are flowcharts for preventing this control.
In step 161, each parameter is read. In step 162, it is determined whether or not the warm-up is completed. If the warm-up is not completed and a negative determination is made, the process returns without doing anything. If an affirmative determination is made, the process proceeds to step 163 to determine whether or not the region is a blow-by prevention target region.
[0061]
If the determination in step 163 is affirmative, a counter COT that counts the operation time within the blow-by prevention target area is incremented. In step 164, it is determined whether the counter COT has reached a predetermined value COTA. If the determination is affirmative, the blow-off prevention flag FOT is set to 1 and the process is terminated. On the other hand, if a negative determination is made in steps 162 and 1603, the process jumps to step 167 to set COT to 0, and in step 168, FOT is set to 0 and the process ends.
Here, it is determined from the map shown in FIG. 18 whether or not it is a blow-through prevention target area in step 163, and when it is in the area of large overlap, it is determined that it is in the blow-through prevention target area.
[0062]
FIG. 17 is a routine that is executed when FOT = 1 in the flowchart of FIG. 16. If it is determined in step 171 whether FOT = 1 or not and an affirmative determination is made, the throttle opening THA is set in step 172. THA−ΔTHA is set (ΔTHA is a predetermined value). If a negative determination is made, FOT is set to 0 in step 173 and the process is terminated.
[0063]
Next, a modification of the first embodiment will be described. In each modification, the catalyst activation method during cold is the same as that in the first embodiment, but the method for preventing catalyst overheating after warm-up is different. First, in the first modified example, the overlap is defined by the rotational speed, and the gear stage of the automatic transmission is changed when a predetermined time elapses in a region where the overlap is large, i.e., the blow-off prevention target region. Thus, the rotational speed is changed to escape from the blow-through prevention target area.
[0064]
FIG. 19 is a diagram for explaining the above concept. In FIG. 19, the horizontal axis is the engine speed, and the region between the speeds NE1 and NE2 is a blowout prevention target area where the overlap is increased as shown in the lower part of the figure. For example, when traveling at point X with a third gear, if the state continues for a predetermined time or longer, a signal is sent to the speed change control mechanism 310 of the automatic transmission 300 and moved to the point Y of the second gear to prevent blow-through prevention. It is made to take off.
[0065]
Similar to the first embodiment, the above-described control is executed when staying in the blow-by prevention target region for a predetermined time or more, and the flowchart of that portion is the same as FIG. FIG. 20 is a flowchart for performing the control described with reference to FIG. 19. If it is determined in step 201 that FOT = 1, the process proceeds to step 202 to issue a gear change instruction, and if not FOT = 1, step 203. The FOT is set to 0 and the process ends.
[0066]
Next, a second modification of the first embodiment will be described. In the second modification, the exhaust manifold is configured as shown by 6 'in FIG. 21, and the collecting pipe 6a of the # 1 cylinder and # 4 cylinder and the collecting pipe 6b of the # 2 cylinder and # 3 cylinder are in the middle of the communication pipe 6c. The exhaust control valve 255 which opens and closes the communication pipe 6c is provided in the middle.
When the exhaust control valve 255 is opened, the pressure of the exhaust port becomes negative during the overlap as in the case of the first embodiment, but when the exhaust control valve 255 is closed, the exhaust is exhausted during the overlap. The port pressure becomes positive. FIG. 22 is a diagram showing this action.
[0067]
Therefore, when the blowout prevention target region remains for a predetermined time or longer, the exhaust control valve 255 is closed, and the pressure of the exhaust port at the time of overlap is set to a positive pressure to prevent blowout. In this control, the flowchart of the part for determining whether or not the target area has remained in the blow-through prevention target area for a predetermined time or more is the same as FIG. FIG. 23 is a flowchart for performing the control described with reference to FIG. 22. When it is determined in step 231 that FOT = 1, the process proceeds to step 232 to issue an instruction to close the exhaust control valve, and FOT = 1 is not satisfied. In this case, FOT is set to 0 in step 233, and an instruction to open the exhaust control valve is sent in step 234, and the process ends.
[0068]
Next, a third modification of the first embodiment will be described. In this third modification, a muffler 400 disposed at the last flow part of the exhaust pipe has a structure as shown in FIG. 24 and includes a back pressure control valve 410 that is opened and closed according to operating conditions. When the back pressure control valve 410 is opened, the back pressure decreases, the average value of the exhaust port pressure Pe decreases, and the exhaust port pressure Pe becomes negative during the overlap, but when the back pressure control valve 410 is closed, As the back pressure increases, the average value of the exhaust port pressure Pe increases, and the pressure of the exhaust port Pe at the time of overlap becomes positive. FIG. 25 is a diagram for explaining this action.
[0069]
Therefore, when the air pressure remains in the blowout prevention target region for a predetermined time or longer, the back pressure control valve 410 is closed, and the pressure Pe of the exhaust port at the time of overlap is set to a positive pressure to prevent blowout. In this control, the flowchart of the part for determining whether or not the target area has remained in the blow-through prevention target area for a predetermined time or more is the same as FIG. FIG. 26 is a flowchart for performing the control described with reference to FIG. 25. When it is determined in step 261 that FOT = 1, the process proceeds to step 262 to issue an instruction to close the back pressure control valve 410, and FOT = If not 1, FOT is set to 0 in step 263, and an instruction to open the back pressure control valve 410 is sent in step 264, and the process ends.
When the back pressure control valve 410 is provided as described above, when the catalyst is activated, the back pressure control valve 410 is opened to reduce the average value of the pressure Pe of the exhaust port, thereby preventing the fuel from blowing through. To improve.
[0070]
Next, a second embodiment will be described. FIG. 27 shows the overlap period in the second embodiment, and it is moved to the retard side significantly compared to the case of the first embodiment shown in FIG. 9B. In comparison with the first embodiment, the second embodiment has a reduced effective intake stroke. As a result, the output decreases, so that the ignition timing retarding control in the first embodiment is not required for the catalyst activation promotion. FIG. 28 is a diagram for explaining control of catalyst activation promotion in the second embodiment.
The control of catalyst activation promotion in the second embodiment is not particularly shown because it is executed in the flowchart of FIG. 6 and the flowcharts of FIGS. 8A and 8B in the first embodiment.
[0071]
Further, compared with the case where the overlap shown in (a) of FIG. 9 is not enlarged, the valve opening period of the intake valve is not changed, so that the exhaust valve is opened compared to the case shown in (a) of FIG. It can be executed only by moving the period. FIG. 29 shows the phase values of the intake camshaft 50 and the exhaust camshaft 50 ′ when the overlap is made large, medium, and small in the second embodiment, and when the catalyst activation is promoted. Uses a phase value that increases the overlap. As shown in FIG. 29, in the second embodiment, the phase of the intake camshaft 50 is fixed.
Note that, as in the first embodiment, the vehicle is usually operated with a predetermined overlap according to the operating conditions.
[0072]
  Next, control for preventing overheating of the catalyst after warm-up in the second embodiment will be described.
  In this second embodiment, when the overlap is expanded after warming up, the fuel injection is closed and the intake valve is closed.OpenAnd the fuel injection time is closed and the intake valve is closed.OpenIf it does not fit while the exhaust valve is closed, the fuel injection time will close and the intake valve willOpenTo stay within.
[0073]
FIG. 30 is a diagram for explaining the above concept. FIG. 30 shows the valve opening period of the intake valve. Further, a fuel injection period TAU in which the end of the injection is closed at the closing timing of the intake valve is shown.
On the other hand, if the valve opening period of the exhaust valve is set as shown on the upper side and the overlap is increased, the fuel is injected during the overlap, and the fuel is unburned by the blow-through. It is discharged as it is and the catalyst is overheated. Therefore, the opening period of the exhaust valve is changed as shown on the lower side to reduce the overlap so that fuel cannot be injected during the overlap.
[0074]
Similar to the first embodiment, the above-described control is executed when staying in the blowout prevention target region for a predetermined time or more, and the flowchart of the determination part is the same as that in FIG. FIG. 31 is a flowchart of the above-described control executed when it is determined that FOT = 1 in the flowchart of FIG.
If an affirmative determination is made in step 311, the intake valve closing timing TINCL is calculated in step 312, and in step 313, the fuel injection start timing TFIGN is calculated by subtracting the fuel injection period TAU from the intake valve closing timing TINCL. As can be seen from this calculation, in the second embodiment, the fuel injection end timing is set to the intake valve closing timing TINCL, but it may be ended earlier than this.
[0075]
Next, at step 314, the exhaust valve closing timing TEXCL is calculated, and the routine proceeds to step 315, where it is determined whether or not the fuel injection start timing TFIGN is ahead of the exhaust valve closing timing TEXCL. If an affirmative determination is made, it means that fuel is injected during the overlap, so the routine proceeds to step 316 and the phase EXCP of the exhaust camshaft 50 ′ is shifted to the advance side by a predetermined amount ΔCP. Thus, the overlap is finished before fuel injection is started. If a negative determination is made in step 315, the process ends without advancing the phase of the exhaust camshaft 50 '. If a negative determination is made in step 311, FOT is set to 0 in step 317, and fuel injection start timing TFIBGN is determined based on a map of normal injection timing in step 318 and the processing ends.
[0076]
Next, a modification of the second embodiment will be described. In this modification, the method for activating the catalyst during cold is the same as in the second embodiment, and when the overlap is expanded after warming up, the fuel injection is closed and the intake valve is closed However, if the fuel injection time does not fit while the exhaust valve is closed and the intake valve is closed, the fuel injection time is shortened, that is, The fuel injection amount is reduced so that the fuel injection is accommodated while the exhaust valve is closed and the intake valve is closed.
[0077]
FIG. 32 is a diagram for explaining the above concept. As in FIG. 30, the exhaust valve opening period, the intake valve opening period, and the overlap period are shown. Further, it is shown that when the fuel injection time TAU is reduced, it can be prevented from overlapping.
FIG. 33 is a flowchart of this control. Steps 331 to 335 and 337 and 338 are the same as steps 311 to 315 and 317 and 318 in FIG. 31, and only TAU is calculated as TAU-ΔTAU (ΔTAU is The value is changed to a predetermined value).
[0078]
It is also possible to combine the overheat prevention means used in the first embodiment and the first to fourth modifications thereof with the catalyst activation promoting means used in the second embodiment. On the contrary, it is possible to combine the overheat prevention means used in the second embodiment and its modifications with the catalyst activation promoting means used in the first embodiment.
The overlap enlargement means, the catalyst activation promotion condition, the blow-through prevention target area, and the like described in the text are merely examples, and the means and conditions are not limited thereto as long as each purpose is achieved.
[0079]
【The invention's effect】
  According to the invention described in each claim, the valve overlap period is expanded by the valve characteristic control device when the engine is in a predetermined predetermined operating state, and the engine exhaust port is expanded during the expanded valve overlap period. The pressure in the intake pipe is increased more than the reduced pressure in the exhaust port, and the intake air mixture blows into the exhaust pipe and burns in the exhaust pipe. As a result, the catalyst is reliably activated. The increase in the output due to the increase in the pressure in the intake pipe is suppressed by the means for suppressing the increase in the output, so that the output not required by the driver is not generated and the driving feeling is not impaired.
[0080]
  Especially according to claim 4, the output increases.TheSuppressionDoThe increase in output is suppressed without requiring any means.
  In particular, exhaust gas can be exhausted as in claim 5.Attached to camshaftvalveCharacteristic control deviceAnd intakeAttached to camshaftvalveCharacteristic control deviceSince the overlap period is expanded, the degree of freedom of expansion of the overlap period is great.
  In particular, exhaust gas can be exhausted as in claim 6.Attached to camshaftvalveCharacteristic control deviceAnd intake valveAttached to camshaftvalveCharacteristic control deviceIn either case, the overlap period is enlarged, so that the overlap enlargement control is simple.
  In particular, according to the seventh aspect of the present invention, the exhaust pipe whose length is optimized is adapted to return to the exhaust port during the valve overlap period in which the negative pressure wave due to the exhaust pulsation is expanded.TheDeclineDoThere is no need to provide means, and the configuration can be simplified and the cost can be reduced.
  In particular, according to the ninth to seventeenth aspects, activation of the catalyst during cold is promoted and overheating of the catalyst after warming up is prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of the present invention.
FIG. 2 is a cross-sectional view of the structure of the valve timing control device taken along a plane passing through the cam central axis.
FIG. 3 is a view of the apparatus of FIG. 1 as viewed from the axial direction.
4 is a view showing a structure of an oil control valve 90. FIG.
5 is a cross-sectional view showing communication between an oil control valve 90 and an oil passage in the camshaft 50 as seen along line 4-4 of FIG.
FIG. 6 is a flowchart of a routine for determining whether or not catalyst activation control is necessary in the first embodiment.
FIG. 7 is a map showing an operation region in which catalyst activity is promoted.
FIG. 8 is a flowchart of control for catalyst activation in the first embodiment.
(A) is a flowchart of control for enlarging the overlap;
(B) is a flowchart of control for increasing the throttle opening and lowering the exhaust port pressure when the overlap is enlarged,
(C) is a flowchart of the control for retarding the ignition timing for suppressing the increase in output due to the increase in throttle.
FIG. 9 is a diagram showing a change in the overlap period in the first embodiment,
(A) is the case of small overlap,
(B) is the case of large overlap.
FIG. 10 is a chart showing the phases of intake camshaft 50 and exhaust camshaft 50 'for making the overlap large, medium, and small in the first embodiment.
11 is a view showing a relative positional relationship between the valve housing 20 and the rotor 40 of the valve characteristic control device 100 when the phase of the intake camshaft is advanced most. FIG.
FIG. 12 is a diagram showing a relative positional relationship between the valve housing 20 ′ and the rotor 40 ′ of the valve characteristic control device 100 ′ when the phase of the exhaust camshaft is most retarded.
FIG. 13 is a diagram comparing the exhaust port pressure and the intake port pressure.
FIG. 14 is a diagram illustrating an operation of catalyst activation in the first embodiment.
FIG. 15 is a diagram for explaining air-fuel mixture blow-through according to the present invention.
FIG. 16 is a flowchart of a routine for determining whether or not control for preventing catalyst overheating is required in the second embodiment.
FIG. 17 is a flowchart of control for preventing catalyst overheating in the second embodiment.
FIG. 18 is a diagram illustrating overlap setting according to the first embodiment.
FIG. 19 is a diagram illustrating control for preventing catalyst overheating in a second modification of the first embodiment.
FIG. 20 is a flowchart of control for preventing catalyst overheating in a second modification of the first embodiment;
FIG. 21 is a view showing a variable exhaust valve used in a third modification of the first embodiment.
FIG. 22 is a diagram for explaining control for preventing catalyst overheating in a third modification of the first embodiment;
FIG. 23 is a flowchart of control for preventing catalyst overheating in a third modification of the first embodiment;
FIG. 24 is a diagram showing a structure of a muffler that makes back pressure variable, which is used in a fourth modification of the first embodiment.
FIG. 25 is a diagram for explaining control for preventing catalyst overheating in a fourth modification of the first embodiment;
FIG. 26 is a flowchart of control for preventing catalyst overheating in a fourth modification of the first embodiment.
FIG. 27 is a diagram showing an enlarged overlap period in the second embodiment.
FIG. 28 is a diagram for explaining control of catalyst activation promotion in the second embodiment.
FIG. 29 is a chart showing the phases of the intake camshaft 50 and the exhaust camshaft 50 'for making the overlap large, medium and small in the second embodiment.
FIG. 30 is a diagram for explaining control for preventing catalyst overheating according to the second embodiment;
FIG. 31 is a flowchart of control for preventing catalyst overheating according to the second embodiment;
FIG. 32 is a diagram for explaining control for preventing catalyst overheating according to a modification of the second embodiment;
FIG. 33 is a flowchart of control for preventing catalyst overheating according to a modification of the second embodiment;
[Explanation of symbols]
2 ... Intake pipe
3 ... Surge tank
4 ... Intake manifold
5 ... Air cleaner
6 ... Exhaust manifold
7 ... Exhaust pipe
10 ... Gear
20, 20 '... housing
22, 22 '... inner protrusion
30 ... Side cover
40, 40 '... rotor
42, 42 '... Vane
50, 50 '... camshaft
60A ... Upper bearing metal
60B ... Lower bearing metal
70 ... Cylinder head
80 ... Cam cap
90 ... Oil control valve
100, 100 '... Valve characteristic control device
110, 110 '... Advance oil chamber
120, 120 '... retarded oil chamber
200 ... ECU
211 ... Air flow meter
212 ... Crank position sensor
213 ... Cooling water temperature sensor
214, 214 '... cam angle sensor
251 ... Electronic throttle
253 ... Spark plug
255 ... Exhaust control valve
300 ... automatic transmission
310 ... transmission control mechanism
400 ... Muffler
410 ... back pressure control valve

Claims (17)

A catalyst temperature control device for controlling the temperature of a catalyst disposed in an exhaust system of an engine provided with a valve characteristic control device capable of changing a valve overlap period according to an operation state,
Means for determining whether it is necessary to promote catalyst activation depending on whether the engine is in a predetermined temperature range and whether the engine is in a predetermined rotation speed or load range;
Means for activating the valve characteristic control device to expand the overlap period when it is determined that promotion of catalyst activation is necessary;
Exhaust pressure lowering means for reducing the pressure in the exhaust port so that the pressure in the exhaust port of the engine during the expanded valve overlap period becomes negative pressure ;
Than the pressure in the negative pressure exhaust port by the exhaust pressure reducing means in the expansion is a valve overlap period made to increase the pressure in the intake port pressure in the intake port to the higher due so, inhaled Intake pipe pressure increasing means for blowing the air-fuel mixture through the exhaust pipe;
An output increase suppressing means for suppressing an increase in engine output by the intake pipe pressure increasing means,
A catalyst temperature control device that promotes catalyst activation by blowing fuel and air into an exhaust pipe and burning the exhaust pipe while suppressing an increase in output when it is determined that promotion of catalyst activation is necessary . Catalyst temperature control apparatus according to claim 1, the intake pipe pressure increasing means, characterized in that a suction pipe throttle opening increasing means for increasing an intake pipe throttle opening.   2. The catalyst temperature control apparatus according to claim 1, wherein the output increase suppressing means adjusts the ignition timing so as to suppress an increase in engine output due to an increase in the intake pipe pressure. 2. The catalyst temperature control apparatus according to claim 1, wherein the output increase suppressing means extends the overlap period so that the output does not increase . 2. The catalyst temperature control device according to claim 1, wherein the valve overlap period is changed by both the valve characteristic control device attached to the exhaust camshaft and the valve characteristic control device attached to the intake camshaft . 2. The catalyst according to claim 1, wherein the valve overlap period is changed by one of a valve characteristic control device attached to the exhaust camshaft and a valve characteristic control device attached to the intake camshaft. Temperature control device.   The exhaust port pressure reducing means is an exhaust pipe itself whose length is optimized so as to return to the exhaust port during a valve overlap period in which a negative pressure wave due to exhaust pulsation is expanded. Catalyst temperature control device. The exhaust port pressure lowering means connects two collective exhaust manifolds , each of which collects a single exhaust manifold, with a communication pipe, and provides an exhaust control valve in the communication pipe. The exhaust control valve expands negative pressure waves due to exhaust pulsation. catalyst temperature control apparatus according to claim 1, adjusted back to the exhaust port during the valve overlap period, characterized by comprising.   The catalyst temperature control device according to claim 1, further comprising catalyst overheat preventing means for preventing overheating of the catalyst when the overlap is expanded after warm-up.   Fuel injection timing adjustment means for adjusting the fuel injection timing so that the fuel is injected while the exhaust valve is closed and the intake valve is open when the catalyst overheat prevention means reaches a condition where catalyst overheating is expected The catalyst temperature control device according to claim 9, wherein   If the fuel injection time is long and fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjustment means, the exhaust valve close timing is shortened to shorten the overlap, and the fuel is blown out. The catalyst temperature control device according to claim 10, wherein the catalyst temperature control device is prevented.   When the fuel injection time is long and fuel is injected during the overlap even if the fuel injection timing is adjusted by the fuel injection timing adjusting means, the fuel injection time is shortened to prevent the fuel from blowing through. The catalyst temperature control apparatus according to claim 10. The catalyst overheat prevention means after warming-up is characterized in that the operation condition is changed so as to escape from the operation region where the overlap is expanded when the condition where the catalyst overheat is expected is reached. The catalyst temperature control apparatus as described.   10. The after-warm-up catalyst overheat prevention means is an inter-port pressure adjusting means for making the pressure of the exhaust port higher than the pressure of the intake port when a condition where the catalyst overheat is expected is reached. Catalyst temperature control device.   15. The throttle opening reduction means for reducing the throttle opening in order to reduce the intake port pressure when the pressure over the port reaches a condition where catalyst overheating is expected. Catalyst temperature control device. A condition in which the pressure adjusting means between the ports connects two collective exhaust manifolds each of which collects a single exhaust manifold with a communication pipe, an exhaust control valve is provided in the communication pipe, and the exhaust control valve is expected to overheat the catalyst. 15. The catalyst temperature control device according to claim 14, wherein when the pressure reaches the value, the exhaust port pressure is set to a positive pressure by closing control at the time of overlap. The pressure adjusting means between the ports is provided with a back pressure control valve at the rear end of the exhaust pipe, and when the back pressure control valve reaches a condition where catalyst overheating is expected, the back pressure control valve is controlled to close at the time of overlap. The catalyst temperature control device according to claim 14, wherein the pressure is a positive pressure .

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