JPH01106913A - Valve control device for engine - Google Patents

Abstract

PURPOSE:To prevent production of a sudden change in generated torque, by a method wherein, when the number of revolutions is approximately in a range of a set value at which shifting between a cam for a high speed and a cam for a low speed takes place, feedback control of an air-fuel ratio is prohibited. CONSTITUTION:A shifting mechanism 15 for a cam for a high speed and a cam for a low speed is actuated according to a difference between the present number of revolutions and the set number of revolutions. Based on an output from an O2 sensor, feedback control of an air-fuel ratio is performed by means of a control unit 24. When an engine is in a partial load state and runs at the number of revolutions within a specified value higher and lower than a set value at which a cam is switched, feedback control is prohibited. This constitution prevents the production of a sudden change in an air-fuel ratio occasioned by shifting of a cam, resulting in the possibility to prevent production of the sudden change in generated torque.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve control device equipped with a variable valve drive mechanism for driving and controlling an intake valve of an engine. More specifically, the present invention relates to a valve control device with a variable valve drive mechanism for an engine in which the air-fuel ratio is feedback-controlled.

(Prior art) In automobile engines, a variable valve drive type valve mechanism is known, which switches and controls the opening and closing of the intake valves of each cylinder using a high-speed cam and a low-speed cam depending on the engine speed. It is being For example, Utsukai Sho 61-58605
The publication discloses a valve control device equipped with this valve operating mechanism. In the device disclosed in this publication, a low-speed cam having a low-speed cam profile for each cylinder is mounted on a camshaft that extends above the intake valve of each cylinder.
A high-speed cam having a high-speed cam profile is formed. First and second rocker arms are in contact with both of these cams, respectively, and only the first mouth and hook arms that are in contact with the low-speed cam are in contact with the upper end of the stem of the intake valve. At low speeds, the low speed cam controls the first
Mouth 1. The car arm swings to control the opening and closing of the intake valve. However, during high rotation, hydraulic pressure acts to move the connecting pin as cam switching means to connect the second mouth/lock arm, which is swung by the high speed cam, to the first rocker arm. Therefore, after this, the swinging motion of the second port/lock arm by the large high-speed cam is transmitted to the intake valve via the first rocker arm. Therefore, the opening and closing of the intake valve is controlled by the high-speed cam.

(Problems to be Solved by the Invention) Here, switching between the two types of cams is performed based on the engine speed. That is, when the engine rotation speed is low (below a preset engine rotation speed), the cam is switched to the low speed cam, and when the engine rotation speed is higher than that, the cam is switched to the high speed cam. It is desirable that the value of the engine rotational speed at which this switching is performed is a value at which the characteristic lines of the high-speed cam and the low-speed cam intersect. This point is illustrated in Figure 7 (
This will be explained with reference to A). As shown in the figure, the amount of intake air relative to the engine speed in the high-speed and low-speed cams changes depending on the engine load, so the intersection of those characteristic lines also changes. Therefore, at full load, the characteristics H1 and Ll of the high-speed and low-speed cams intersect at Na, but at partial load, as shown by characteristic lines H2, L2 and H3, L3, the rotation is higher or lower than that. Move to the side.

Therefore, for example, when switching the cam at the point of value Na, the amount of intake air changes suddenly at the point of Na, as shown by characteristic lines H3 and L3. Therefore, especially in an engine in which the air-fuel ratio of the air-fuel mixture is feedback-controlled based on the output of the 02 sensor, the air-fuel ratio is controlled in response to this drastic change in the amount of intake air. Therefore, as shown by the solid line in FIG. 7(B), the generated torque fluctuates rapidly, and the resulting torque shock significantly deteriorates ride comfort.

An object of the present invention is to realize an engine valve control device that can eliminate such torque shock during cam switching.

(Means for Solving the Problems) In order to achieve the above object, in the valve control device of the present invention, at least the engine is in a partial load operating state, and the engine speed is different from that of the low-speed valve and the high-speed valve. Feedback control of the air-fuel ratio is prohibited when the rotation speed is within a constant range above and below the rotation speed at which switching with the valve is performed.

In this way, by prohibiting air-fuel ratio feedback control, the air-fuel ratio control precision is reduced in this section,
The air-fuel ratio will gradually approach the target value. Therefore, unlike the case where feedback control is performed, the air-fuel ratio does not react sensitively to the switching operation of the cam and fluctuate rapidly. Therefore, drastic changes in the generated torque can be avoided.

(Effects of the Invention) As described above, in the present invention, since feedback control of the air-fuel ratio is prohibited when switching the cam to be used, it is possible to prevent drastic changes in the generated torque at the time of switching.

(Example) The present invention will be described in detail below with reference to the drawings.

In this embodiment, the present invention is applied to a three-valve type engine. FIG. 1 shows a cross section of the valve mechanism of the engine of this example, FIG. 2 shows an enlarged view of the valve mechanism on the intake valve side, and FIG. 3 is a diagram showing the valve mechanism viewed from above. FIG.

In the figure, 1 is an intake valve, and two valves 1 are arranged for each cylinder. 2 is an exhaust valve, and one exhaust valve 2 is arranged per cylinder. Reference numeral 3 denotes a camshaft, and on this shaft, three cams 4a, 4b15 for driving intake valves and one cam 6 for driving exhaust valves are arranged for each cylinder. Three intake valve drive cams 4a, 4b
Among the cams 15, two cams 4a and 4b are low speed cams having a low speed cam profile, and the remaining one cam 5 is a high speed cam having a high speed cam profile. As can be seen from FIG. 3, these cams are arranged such that a high speed cam 5 and an exhaust valve driving cam 6 are arranged between low speed cams 4a and 4b for each cylinder.

Above and parallel to the camshaft 3, rocker shafts 7.8 are arranged on both sides. On the exhaust valve side rocker shaft 7, an exhaust valve driving rocker arm 31, which is interposed between the exhaust valve driving cam 6 and the exhaust valve 2, is swingably supported.

Three rocker arms 9, 10, and 11 for driving the intake valves are swingably supported on the rocker shaft 8 on the intake valve 1 side. The two rocker arms 9 and 10 located above the low speed cams 4a and 4b are low speed rocker arms. As shown in FIG. 2, the swinging arm ends 9a, 10a on one side are in rolling contact with the low-speed cams 4a, 4b of the camshaft 3 via rollers 12, and The arm ends 9b, 10b are in contact with the valve stems Ia, la of the intake valve 1.1 via a hydraulic lash adjuster 13.

On the other hand, the rocker arm 11 is a high-speed rocker arm located above the high-speed cam, and is arranged in contact with the opposing sides of the two low-speed rocker arms 9 and 10, respectively. In this high-speed rocker arm 11, a swinging arm fllla on the camshaft 3 side is in sliding contact with the high-speed cam 5 of the camshaft 3 via a slipper 14. Further, a hydraulic switching mechanism 15 is incorporated in the swinging arm end 11b of the high-speed rocker arm 11 on the valve side. This switching mechanism 15 is controlled according to the engine speed to engage and disengage the high-speed rocker arm 11 from the low-speed rocker arm 9.10. By this switching mechanism, when the high-speed rocker arm 11 is connected to the low-speed rocker arm, the high-speed rocker arm becomes interlocked with the low-speed rocker arm 9.10.

That is, the three rocker arms swing together as one. Here, as shown in FIG. 4, the lift curve of the high-speed cam is larger than that of the low-speed cam. Therefore,
When the high-speed rocker arm 11 is interlocked with the low-speed rocker arm, these three rocker arms are swung by the high-speed cam. On the other hand, when the high-speed rocker arm 11 is separated from the low-speed rocker arm, the opening and closing of the intake valve 1 is controlled by the low-speed rocker arm 9 and 10, which is swung by the low-speed cam. will be held.

Next, referring to FIG. 5, the above-mentioned hydraulic switching mechanism 1
The configuration of No. 5 will be explained. This mechanism 15 has a hydraulic chamber 1 formed in the valve-side arm of the high-speed rocker arm 11.
It is equipped with 6. This hydraulic chamber opens on the side surface of the low-speed rocker arm, and a select pin 17 is slidably inserted through this opening. On the other hand, an insertion hole 18 for inserting a select pin is formed on the side surface of the low-speed rocker arm at a position that corresponds to the opening of the hydraulic chamber.

A receiver 19 biased by a return spring 19 is slidably inserted into this hole, and the surface of the receiver 19 and the tip 17a of the select pin 17 are connected to each other.
are in contact with each other.

In the hydraulic chamber 16, the oil accumulated in the oil pan 21 is transferred to the oil pump 22 and the solenoid valve 23.
are supplied sequentially. When the solenoid bubble 23 is turned on, high hydraulic pressure PH is supplied to the hydraulic chamber 16. - On the other hand, when this valve 23 is in the OFF state, low oil pressure PI is supplied to the oil pressure chamber 16. When low oil pressure is acting, this oil pressure and the spring force of the return spring are in balance, and the tip of the select pin 17 is in a position that exactly coincides with the side surface of the high-speed rocker arm. On the other hand, when high hydraulic pressure acts on the hydraulic chamber, the balance between the two is disrupted and the select pin 17 is inserted into the insertion hole 18 on the low-speed rocker arm side against the spring force (
(See Figure 3). As a result, the high-speed rocker arm and the low-speed rocker arm are connected by this select pin.

The solenoid valve 23 mentioned above is controlled on and off by a control unit. This control unit 24 constitutes the central part of the engine control device, and can be composed of, for example, a one-chip microcomputer, such as a CPU.

ROM and RAM are its main components. Various information required for control is supplied to the human power port of the control unit 24. For example, the intake air amount Q, intake air temperature T1, throttle opening e, etc. are inputted from an air flow meter, an intake air temperature sensor, a throttle sensor, etc. attached to the intake pipe, respectively. Further, a detection signal is input from the 02 sensor attached to the exhaust pipe, and an engine rotation speed Ne is input from the rotation speed sensor attached to the engine output shaft. The control unit performs feedback control of the actual air-fuel ratio based on the output of the 0□ sensor so as to reach the target air-fuel ratio set according to the operating state. In other words, by calculating the amount of fuel supplied relative to the amount of intake air,
The fuel supply mechanism connected to the output port, in this example, the fuel injection valve 25, is driven and controlled so that this amount of fuel is supplied.

Next, control operations performed mainly by the control unit will be explained with reference to FIGS. 6 to 8.

First, FIG. 6 shows a flowchart of the control operation of the solenoid valve 23. In this example, when the engine speed Ne is in the low-speed operating range lower than the value Na, the low-speed cam 9.10 is used, and when the engine speed Ne is in the high-speed operating range H above the value Na, the high-speed cam 11 is used. like using
Performs switching control. That is, step STI
In step ST2, it is determined whether or not the engine speed Ne is equal to or greater than the value Na, and if so, the process proceeds to step ST2 and the solenoid valve 23 is turned on. On the other hand, if the engine speed Ne is less than the value Na, the process proceeds to step ST3, and the throat valve 23 is turned off. When the solenoid valve 23 is turned on, high oil pressure acts on the hydraulic chamber 16 of the switching mechanism 15 to move the select pin 17. Therefore, the high-speed rocker arm 11 is connected to the low-speed rocker arm 9.10, and the high-speed cam 5 starts opening/closing control of the intake valve 1. However, when the solenoid valve 23 is off, low oil pressure acts on the hydraulic chamber 16 of the switching mechanism 15, so the high-speed rocker arm is separated from the low-speed rocker arm. Therefore, the opening and closing of the intake valve is controlled by the low speed cam.

Therefore, in this example, as shown in FIG. 7(A), when the engine speed Ne is less than Na, the low speed cam is used and the intake air amount changes as shown by curves L1, L2, and L3. . On the other hand, when the engine speed Ne is higher than Na, the high-speed cam is used and the intake air amount is changed to curve H1.
It changes as shown by H2 and H3.

Next, referring to FIG. 8, the fuel injection amount calculation control operation by the injection valve will be explained. This injection amount is calculated as a function of the opening time of the injection valve. First, in step 5T11, the basic injection amount is calculated.

After this, various injection amount correction amounts are calculated based on various parameters indicating the detected engine operating state (steps 5T12.13.14, 16.18.19
). Additionally, an injection amount correction amount corresponding to the response delay of the injection valve is calculated as an invalid injection time (step 5T20).
. Thereafter, in step 5T21, the basic injection amount is corrected based on the calculated correction amount, and the final injection amount is calculated.

The control unit controls opening and closing of the injection valve so that the calculated injection amount of fuel is injected.

Here, as shown in step 5T16, the injection amount is 02
Feedback control is performed based on sensor output.

In other words, feedback control is performed based on this sensor output so that the air-fuel ratio matches the target air-fuel ratio.

However, as shown in step 5T15.16, the engine rotational speed Ne falls within constant intervals Nh and Nl above and below the value Na.
Feedback control is not performed when the Therefore, in this case, the air-fuel ratio is under open-loop control. As a result, within this section, the responsiveness of the air-fuel ratio control decreases, and the air-fuel ratio is gradually adjusted to the target air-fuel ratio.
The actual air/fuel ratio is changing. - As an example, see Figure 7 (A
) The case of the partial load operating state shown by curves L3 and H3 will be explained. In this case, as described above, when the engine speed Ne becomes equal to or greater than the value Na, the cam used is switched from the low-speed cam to the high-speed cam.

As a result, the intake air amount shifts from curve L3 to curve H3, so it changes discontinuously. If the air-fuel ratio is feedback-controlled in response to this change, the generated torque will change discontinuously, resulting in a torque shock, as shown by the solid line in FIG. 7(B). However, in this example, since feedback control is not performed, the responsiveness of the air-fuel ratio control decreases, and the actual air-fuel ratio gradually approaches the target air-fuel ratio corresponding to the drastically changed intake air amount. That is, the generated torque changes as shown by the broken line in FIG. 7(B).

Therefore, torque shock does not occur when switching the cam to be used.

In this way, in the device of this example, feedback control of the air-fuel ratio is prohibited within a certain engine speed range that includes the engine speed at which the cam to be used is switched, so the torque at the time of switching the cam to be used is It is possible to prevent the occurrence of shock.

In this example, feedback control is prohibited within the above-mentioned section whether the engine is operating at full load or at partial load. However, there are cases where particularly responsive control is required at full load, and therefore it may be preferable to continue feedback control as is at full load.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing a portion of the valve mechanism of an engine to which the present invention is applied, FIG. 2 is a partial sectional view showing an enlarged portion of the valve mechanism on the intake valve side of FIG. 1, and FIG. The figure is a top view of the valve mechanism in Figure 1 seen from above, Figure 4 is a characteristic diagram showing the lift curves of the high-speed and low-speed cams in Figure 1, and Figure 5 is a diagram showing the lift curves of the high-speed and low-speed cams in Figure 1. Schematic block diagram of control device, No. 6
The figure is a flowchart showing the switching operation of the cam used, No. 7 rgJ (A) is a characteristic diagram showing the value of the intake air amount with respect to the engine speed of the high-speed and low-speed cams of Fig. 1, and Fig. 7 (B) is the A characteristic diagram showing changes in torque and FIG. 8 are a flowchart showing an operation for calculating an injection amount. 1... Intake valve 3... Camshaft 4a, 4b... Low speed cam 5... High speed cam 8... Rocker shaft 9 .10...Lower speed rocker arm 11...
... High-speed rocker arm 15 ... Switching mechanism 16 ... Hydraulic chamber 17 ... Select pin 19 ... Release spring 20 ...・Receiver 23... Solenoid valve 24... Control unit L...
Low rotation region H...High rotation region Fig. 2 Fig. 3 Fig. 6 Fig. 7

Claims (1)

[Claims] A low-speed cam for controlling the opening and closing operations of the intake valve in the low-speed range, a high-speed cam for controlling the opening and closing operation of the intake valve in the high-speed range, and any of the high-speed and low-speed cams. cam switching means for switching whether to control the intake valve using the cam; and selecting the high-speed cam when the engine speed is higher than the set speed, and selecting the high-speed cam when the engine speed is lower than the set speed. In this case, at least a portion of the engine includes a switching control means for controlling the cam switching means and an air-fuel ratio control means for feedback-controlling the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber so as to select the low-speed cam. Feedback control prohibition means for prohibiting feedback control by the air-fuel ratio control means when the engine is in a load operating state and the engine speed is within a constant rotation speed range above and below the set rotation speed. An engine valve control device featuring: