JP2805705B2 - Engine valve gear - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve train for an engine.

(Prior art) As shown in Japanese Utility Model Application Laid-Open No. 61-58605, the valve operating device of an engine uses high / low speed cams to change the opening / closing characteristics of intake / exhaust valves according to the engine speed. Something to do is suggested. That is, at low rotation speeds, the lift amount of the intake valve is reduced by using the low-speed cam, and at high rotation speed, the lift amount of the intake valve is increased by using the high-speed cam. Regardless of the load,
A high output is always obtained in any engine speed range in the low speed range.

(Problems to be Solved by the Invention) However, when attention is paid to the engine load, it is better to focus on the fuel consumption without much output at the time of the medium load. The valve device could not respond.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to improve fuel efficiency at a medium load while maintaining a conventional operating state at a low / high load.

(Means and Action for Solving the Problems) In order to achieve the above object, the present invention has the following configuration as a first configuration. That is, on / off valve characteristic adjusting means for adjusting the on / off valve characteristics of the intake / exhaust valve, load detecting means for detecting an engine load, receiving an output from the load detecting means, and controlling the on / off valve characteristic adjusting means. A control means for delaying the closing timing of the intake valve at a middle engine load so that a part of the intake air is pushed back to the intake port before the intake valve closes and the intake charging efficiency is reduced, as compared with a high engine load. , Is provided.

To achieve the above object, the present invention has the following configuration as a second configuration.

That is, on / off valve characteristic adjusting means for adjusting the on / off valve characteristics of the intake / exhaust valve, load detecting means for detecting an engine load, receiving an output from the load detecting means, and controlling the on / off valve characteristic adjusting means. When the engine is under medium load, the overlap period of the intake / exhaust valve is made longer than when the engine is at high load, and the closing timing of the intake valve is adjusted such that a part of the intake air is pushed back to the intake port before the intake valve closes, and the intake air is exhausted. And control means for delaying the filling efficiency so as to decrease it.

The first and second configurations are shown in a block diagram in FIG.

(Effects of the Invention) According to the invention having the first configuration, the closing timing of the intake valve is pushed back to the intake port before the intake valve closes when a part of the intake is closed during the middle load of the engine as compared with when the engine is heavily loaded. Therefore, the intake charging efficiency is reduced so as to decrease the intake charging efficiency, so that the work at the time of intake can be reduced, and the fuel efficiency under a medium load can be improved.

According to the invention having the second configuration, in addition to the effect of improving the fuel efficiency at the time of medium load corresponding to the effect of the first configuration, it is possible to raise the temperature of the combustion chamber by increasing the internal EGR so that HC Can also be reduced.

Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 2, reference numeral 1 denotes a 4-cycle reciprocating Otto-type engine body. As is known, the engine body 1 includes a combustion chamber 5 comprising a cylinder block 2, a cylinder head 3, and a piston 4 for each cylinder. Each combustion chamber 5 is provided with first and second two intake ports 6 (one of which is not shown) and an exhaust port 7. The intake ports 6 are each provided with an intake valve 8, and the exhaust port 7 is equipped with an intake valve 9. These valves are operated by a valve operating device 10, and each port 6 is operated at a predetermined timing. , 7 are opened and closed.
In each of the combustion chambers 5, an ignition plug 12 is arranged.
An air cleaner 14 and an air flow meter are sequentially provided from the upstream side to the downstream side of the intake pipe 13 connected to the intake ports 6.
15, a throttle valve 16 and a fuel injection valve 17 are arranged.

The valve train 10 will be described in detail with reference to FIGS. 3 to 5. On the cylinder head 3, a cam shaft 18 is pivotally supported between the intake valves 8, 8 and the exhaust valve 9. The camshaft 18 is provided with two first cams 19a and 19b each having a low-speed cam profile for each cylinder, and a second high-speed profile having a high-speed profile between the two first cams 19a and 19b. A cam 20 is provided, and a cam 21 for the exhaust valve 9 is provided between the one first cam 19b and the second cam 20. The cam profile of the second cam 20 is
As shown in FIG. 5, the intake valves 8, 8 are provided by the first cams 10a, 10b.
So that the valve opening period is longer than when
The first cams 19a and 19b are formed to have a larger shape over the entire circumference than the profile of the first cams 19a and 19b so as to increase the lift amount.

A rocker shaft 22 for the intake valve and a rocker shaft 23 for the exhaust valve are provided on the intake valve 8 side and the exhaust valve 9 side of the camshaft 18.
Are arranged respectively. Rocker shaft for intake valve
The rocker arm 22 has two rocker arms 24a, 24b for transmitting the movements of the cams 19a, 19b to the intake valves 8, 8, respectively, corresponding to the two intake valves 8, 8 of each cylinder. . The rocker arms 24a, 24b have one end disposed on the stem of each intake valve 8, 8 and the other end of each rocker arm 24, 24a.
It is mounted on cams 19a and 19b and pivoted. At the ends of the rocker arms 24a and 24b on the intake valve 8 side, a hydraulic lash adjuster 25 for maintaining the valve lash at an appropriate value is arranged, and at the ends of the first cams 19a and 19b, Roller that reduces sliding resistance with the first cams 19a and 19b
26 are pivoted.

Further, the rocker arm 22 for transmitting the movement of the second cam 20 to the rocker arms 24a, 24b on both sides between the two rocker arms 24a, 24b of each cylinder is provided on the rocker shaft 22 for the intake valve. One end is arranged on the second cam 20 and is pivotally supported. Rocker arm 27 second
A roller 28 for reducing sliding resistance with the second cam 20 is pivotally supported at the cam 20 side end. The roller 28 has an axial length longer than the rollers 26 of the rocker arms 24a and 24b.

On the other hand, an exhaust valve rocker arm 29 for transmitting the movement of the exhaust valve cam 21 to the exhaust valve 9 is pivotally supported on the exhaust valve rocker shaft 23, and a roller 30 is also pivotally supported at the cam side end. ing.

The rocker arm 27 is provided with hydraulic switching mechanisms 31, 31 for switching the rocker arm 27 and the rocker arms 24a, 24b on both sides thereof into an interlocking state or a non-interlocking state. Each switching mechanism 31 includes a cylinder 31a formed on the rocker arm 27, a switching pin 31b fitted in the cylinder 31a, and a hydraulic chamber 31c formed in the cylinder 31a by the switching pin 31b. The hydraulic chambers 31c are connected to an oil pump P via an oil passage 32 passing through the rocker arm 27 and the intake valve rocker shaft 22. A solenoid valve as a switching valve is provided in the oil passage 32
A bypass passage 32a that bypasses the solenoid valve 33 is connected to the oil passage 32,
The bypass passage 32a has a smaller diameter than the oil passage 32. On the other hand, each rocker arm 24a, 24b is formed with a fitting hole 34 into which the switching pin 31b is fitted, and a pin receiver 35 is attached to the fitting pin 34 by a return spring 36 on the switching pin 31b side. It is inserted in a state of being urged. When the solenoid valve 33 is closed (OFF), the oil passage 32 is closed and the bypass passage 32a is closed.
Only the open state, the hydraulic pressure in the hydraulic chamber 31c drops due to the large pressure loss of the bypass passage 32a, the switching pin 31b is thrown into the cylinder 31a by the urging force of the return spring 36, and each rocker arm 24a, 24b and the rocker arm When the solenoid valve 3 is opened (ON), the oil passage 32 and the bypass passage 32a are opened, and the pressure loss becomes considerably smaller than when the solenoid valve 33 is closed. The hydraulic pressure in the hydraulic chamber 31c rises,
The switching pin 31b protrudes from the cylinder 31a against the urging force of the return spring 36 and fits into the fitting hole 34 of each rocker arm 24a, 24b, and each low-speed rocker arm 24a, 24b and the high-speed rocker arm 27 are connected. They are linked.

In FIG. 2, reference numeral 41 denotes a control unit constituted by, for example, a microcomputer. Each signal from the sensors 42 and 43 is input to the control unit 41. The sensors 42 and 43 will be sequentially described. The sensor 42 detects the amount of intake air in the air flow meter 15, and the sensor 43 detects the engine speed.

On the other hand, the control unit 41 outputs a control signal to the solenoid valve 33.

In this control unit 41, switching characteristics between the first cams 19a and 19b and the second cam 20 are stored in advance as shown in FIG. In FIG. 6, the area A is an area using the second cam 20, and the area B is an area using the first cams 19a and 19b. That is, in the high engine speed range, the second cam 20 is used regardless of the engine load (indicated by the air charge amount Q in FIG. 6). In the low engine speed range, the engine load is high (K2 ≦ in FIG. 6).
Q), a medium load range (K ₁ <Q <K _{2 in} FIG. 6) and a low load range (K ₁ ≧ Q in FIG. 6). While the first cams 19a and 19b are to be used, the second
A cam 20 is to be used.

Therefore, in the low engine speed range of the engine speed,
As a result of the use of the second cam 20 in the medium load range, as shown in FIG. 5, the lift amount of the intake valves 8, 8 increases, the valve opening time becomes longer, and the high / low load range increases. As compared with the case of (1), the overlap period of the intake / exhaust valves 8 and 9 becomes longer and the closing timing of the intake valve 8 becomes later.
In the low load region, the first cams 19a and 19b are used, and the overlap period of the intake and exhaust valves 8, 9 is shorter than in the middle load region.

As a result, exhaust gas (internal EGR) remains without being exhausted, especially in a medium load range in a low engine speed range compared to a high / low load range, and the calorific value of the exhaust gas is reduced. This can help to increase the temperature of the combustion chamber, so that even if a large amount of exhaust gas stays in the combustion chamber, it is possible to maintain good flammability.

In addition, since the overlap period of the intake / exhaust valves 8 and 9 becomes longer, the intake resistance can be reduced by pulling back the exhaust gas during intake, and the closing timing of the intake valve 8 becomes later, A part of the intake air is pushed back to the intake port 6 shortly before the intake valve 8 closes, so that the intake work is partially canceled and the intake work can be reduced. As a result, pumping loss can be significantly reduced.

By improving the flammability and reducing the pumping loss, fuel efficiency is remarkably improved in a medium load range.

On the other hand, the first cams 19a and 19b are used in a high / low load range in a low engine speed range, and the second cam 20 is used in a full load range in a high engine speed range. Therefore, in each of these cases,
High output can be secured as before.

In switching between the second cam 20 and the first cams 19a and 19b, a time lag is taken into consideration. That is, the first
Switching between the cams 19a and 19b and the second cam 20 is performed by turning on and off the solenoid valve 33 and applying hydraulic pressure to the switching mechanism 31, but in practice, as shown in FIG. There is a time lag before the ON / OFF signal of the solenoid valve 33 reaches a predetermined hydraulic pressure state (FIG. 7 shows a time lag with respect to the ON signal to the solenoid valve 33). Switching speed Ner
However, torque shock is to occur. For this reason, in the present embodiment, the ON signal to the solenoid valve 33 is set to an ON signal to the solenoid valve 33 at a rotation speed lower than the predetermined switching rotation speed Nec in accordance with the increase or decrease in the engine rotation speed Ne. As a result, torque shock is prevented by setting the rotation speed higher than a predetermined switching rotation speed.

Further, at the time of medium load, the combustion chamber 5 becomes high temperature due to the heat of the internal EGR due to the increase of the internal EGR, so that the HC can be reduced.

Next, an example of the above-described control will be described with reference to a flowchart shown in FIG. S indicates a step.

First, in S1, the intake air amount from the sensors 42 and 43,
The engine speed is read, and a predetermined switching speed Nec is set in S2. In S3, a rotation speed change amount ΔNe, which is a difference between the previous engine rotation speed and the current engine rotation speed, is calculated.
Is calculated. In S5, the correction amount of the predetermined switching speed Nec is obtained from the rotation speed change amount ΔNe based on the map, and in S6, the correction amount c is calculated from the predetermined switching speed Nec.
Is subtracted to calculate the correction switching rotational speed Nop (see FIG. 7). As a result, the engine speed based on the time lag
Ne will be able to cope with changes.

In S7, the engine speed Ne is the correction switching speed
It is determined whether or not it is larger than Nop.When S7 is YES, the solenoid valve 33 is turned ON in S8 because it belongs to the high rotation speed range, and when the predetermined switching rotation speed Nec is based on the time lag, Timely, second cam 20
(See FIG. 6).

When the S7 is NO, it will belong to the low-speed range, in the next S9, K ₁ <Q <whether K _2, i.e. belongs to the medium load range is determined. When S9 is NO, since the load is high and low, the solenoid valve 33 is turned off, and the timing is good at a predetermined switching speed Nec.
This is switched to the first cams 19a and 19b (see FIG. 6). On the other hand, when S9 is YES, the solenoid valve 33 is turned ON because the load is in the middle load range, and the first switching speed Nec is good at the first switching speed Nec.
It will be switched to cam 20.

FIG. 9, FIG. 10, and FIG. 11 show the second embodiment. In this embodiment, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In this embodiment, as in the previous embodiment, the detection signals from the sensors 42 and 43 are input to the control unit 41,
From the control unit 41, a control signal is output not only to the solenoid valve 33 but also to the igniter 45. As is well known, the igniter 45 interrupts the temporary current of the ignition coil 46 at a timing corresponding to the ignition timing signal from the control unit 41, and this high voltage is applied to each ignition plug via the distributor 47. It is supplied to 12 and ignition is performed.

In this control unit 41, the cam switching characteristics as shown in FIG. 6 are stored in advance in the same manner as in the above-described embodiment, and the switching control between the second cam 20 and the first cams 19a19b is performed based on the characteristics. The torque shock due to the time lag at the time of cam switching at that time,
Without correcting the predetermined switching rotation speed Nec, the ignition timing is alleviated by correcting the ignition timing at the time of cam switching.

An example of the above control will be described with reference to the flowcharts shown in FIGS. In each of the flowcharts, the flag FON indicates whether or not an ON signal has been output to the solenoid valve 33. When FON = 1, it means that an ON signal has been output to the solenoid valve 33, and when FON = 0, This means that an OFF signal is being output to the solenoid valve 33. FC indicates whether the cam is being switched or not. When FC = 0, the cam is being switched, that is, the solenoid valve 33 is turned ON, OF
This means a state from when the F signal is transmitted until the cam switching is completed. When FC = 1, it means that the cam is not being switched. Note that P in FIG. 10 and Q in FIG.
Indicates a step.

First, in P1, initialization is performed, FON and FC are set to 0, and in P2, the intake air amount and the engine speed Ne are read from the sensors 42 and 43. Next, in P3, a predetermined switching rotation speed Nec is set, and in P4, a rotation speed change amount ΔNe which is a difference between the previous engine rotation speed and the current engine rotation speed is calculated, and in P5, A charge amount Q indicating an engine load state is calculated from the intake air amount and the engine speed Ne.

Next, in P6, it is determined whether or not the engine speed Ne is higher than a predetermined switching speed Nec, and P6 is YES.
In the case of, it is determined that the engine rotational speed belongs to the high rotational speed region, and it is determined in P7 whether or not FON = 0. P7
In the case of YES, it is determined that it has just shifted to the region A in FIG. 6, and in P8, the ignition number CD within the time lag time is calculated from the rotation speed change ΔNe, and in P9, FON = 1 is set, and in P10, Will go on.

When P7 is NO, the process directly proceeds to P10 because it is not immediately after shifting to the region A.

At P10, it is determined whether the number of ignitions CD = 0 or not.
When 0 is YES, it is not during cam switching,
Is set to FC = 1. Then, at P12, FON =
It is determined whether the value is 1 or not, and when P12 is YES, in P13, the solenoid valve 33 is turned ON and the mode is switched to the second cam 20.

When P12 is NO, an OFF signal is output to the solenoid valve 33.
3 is OFF.

When P10 is NO, it is determined that the number of ignitions CD is present. At P15, it is determined whether or not ignition has occurred. When P15 is YES, 1 is subtracted from the number of ignitions CD at P16 to count down. Then, in P17, it is determined whether or not the ignition number CD = 0, and when P17 is YES, the process proceeds to P11. On the other hand, when P17 is NO, FC is set to FC = 0 in P18. You will proceed to P12.

When P15 is NO, the process directly proceeds to P18 without counting down the ignition number CD.

Wherein when P6 is NO, will be the engine speed belongs to a low speed range, in the next _{P19, K 1 <Q <K} 2,
That is, it is determined whether or not it belongs to the medium load region (see FIG. 6). When P19 is YES, the process proceeds to P7. When P19 is NO, it belongs to the high and low load range, so that it is determined at P20 whether FON = 1 or not in order to determine whether or not it is immediately after the shift. When P20 is YES, it is determined that it is immediately after the shift, and in P21, the ignition number CD within the time lag time is calculated from the rotation speed change amount ΔNe, and P
In F22, FON is set to 0, and the process proceeds to P10.

When P20 is NO, since the transition to the area B is not immediately after, the process directly proceeds to P10.

On the other hand, using the state of the flag FC in FIG.
The ignition timing is adjusted based on the flowchart shown in FIG. That is, in Q1, various signals are read, and in Q2, it is determined whether or not the vehicle is in an idle state. When Q2 is NO, the basic ignition timing IgB is set based on the engine speed Ne and the charging amount Q based on the ignition timing basic map. Next, it is determined whether or not FC = 0 in Q4, and when Q4 is YES, the ignition timing correction amount IgC is calculated in Q5.
Then, in Q6, the basic ignition timing IgB and the ignition timing correction amount IgC are added, and the final ignition timing Ig is calculated.
In, ignition is performed based on the final ignition timing Ig,
The torque shock at the time of cam switching is reduced.

When Q4 is NO, it is not during the cam switching, so that IgC = 0 in Q8, and in Q6,
gB and IgC = 0 are added, and the final ignition timing I without correction is added.
g is calculated, and then the process proceeds to Q7.

When Q2 is YES, the ignition timing Igi at the time of idling is calculated in Q9, which is set as the final ignition timing Ig in Q10, and thereafter, the process proceeds to S7.

Although the embodiments have been described above, the present invention includes the following.

Detect boost pressure, accelerator opening, etc. as engine load.

In the first embodiment, as shown in FIG. 12, the differential value of the change in the engine speed, the acceleration of the accelerator opening, the change rate of the air charge amount (the differential Value), using map control of intake air amount and engine speed.

In the second embodiment, the torque shock at the time of cam switching is reduced by adding a correction (fuel rich) to the air-fuel ratio instead of correcting the ignition timing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is an explanatory diagram showing the overall configuration according to the first embodiment, FIG. 3 is an explanatory diagram illustrating the valve train in plan view, FIG. Fig. 5 is an enlarged explanatory view of a main part of the valve train, Fig. 5 is a characteristic diagram showing valve opening characteristics of intake and exhaust valves, Fig. 6 is a characteristic diagram showing cam switching characteristics, and Fig. 7 is shaft torque-engine speed. , FIG. 8 is a flowchart showing a control example according to the first embodiment, FIG. 9 is an explanatory diagram showing the overall configuration according to the second embodiment, FIG. 10, FIG. FIG. 12 is a flowchart showing a control example according to the second embodiment. FIG. 12 is a characteristic diagram showing a modification of the first embodiment. 8: Intake valve 9: Exhaust valve 33: Solenoid valve 41: Control unit 42, 43: Sensor

Continuation of front page (56) References JP-A-60-153411 (JP, A) JP-A-62-191636 (JP, A) JP-A-63-120820 (JP, A) JP-A-59-63338 (JP) JP-A-61-93216 (JP, A) JP-B-63-29093 (JP, B2) JP-B 5-80561 (JP, B2) JP-B 5-31659 (JP, B2) 2-38041 (JP, Y2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 13/02 F01L 13/00 F01L 1/34 F02B 29/08

Claims (2)

(57) [Claims] An opening / closing valve characteristic adjusting means for adjusting opening / closing valve characteristics of an intake / exhaust valve; a load detecting means for detecting an engine load; an output from the load detecting means; The engine is controlled to delay the closing timing of the intake valve so that a part of the intake air is pushed back to the intake port before the intake valve closes and the intake charging efficiency is reduced when the engine is at the medium load compared to when the engine is at the high load. A valve train for an engine, comprising: control means. 2. An on-off valve characteristic adjusting means for adjusting an on-off valve characteristic of an intake / exhaust valve; a load detecting means for detecting an engine load; By controlling, when the engine is at medium load, the overlap period of the intake / exhaust valve is made longer than at the time of high engine load, and the closing timing of the intake valve is pushed back to the intake port before a part of the intake valve closes. Control means for delaying the intake air charging efficiency so as to reduce the intake air charging efficiency.