JPH042780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve timing control device that controls the opening time of an intake valve or an exhaust valve in response to changes in operating conditions.

(Description of Prior Art) Generally, it is preferable to change the opening/closing timing of the intake and exhaust valves of an engine depending on the operating state of the engine. For example, in high-load engine operation, it is necessary to increase the charging efficiency by increasing the valve opening time in order to obtain high output, but by delaying the timing of closing the intake valve, the valve opening period can be extended This causes a problem of intake air blowback during high-load, low-speed operation. Additionally, the overlap period between the intake and exhaust valves has an effect on the amount of residual burnt gas in the intake air, but when the engine is operating at low load, it is recommended to shorten this overlap period as much as possible to reduce the amount of residual burnt gas. This is preferable in terms of achieving combustion stability, and as a result, the idling speed can be lowered, and advantageous results such as improved fuel economy and a reduction in unburned harmful components in the exhaust gas can be obtained. It is conventionally known to variably control the valve opening timing of an engine depending on the engine operating state in consideration of the above circumstances. For example, Japanese Patent Publication No. 52-35816 discloses a structure in which the meshing relationship between a timing chain and a camshaft sprocket is changed, thereby changing valve timing in response to changes in operating conditions. There is. Also, special public service 52-35819
The publication states that a planetary gear mechanism controlled by a centrifugal governor is interposed between the engine output shaft and the camshaft, and a phase change is caused between the engine output shaft and the camshaft according to the engine speed. A structure is disclosed. In addition, there is also a known structure in which a cam whose shape changes in the axial direction is formed on the camshaft, and the camshaft is moved in the axial direction according to engine operating conditions to change the valve opening timing. ing. These conventional devices control valve timing according to engine operating conditions, mainly changes in engine speed, but as mentioned above, different phenomena occur depending on changes in load, so these devices Therefore, it is not possible to perform valve timing control that adequately responds to changes in operating conditions.

(Object of the present invention) Therefore, an object of the present invention is to provide a reliable valve timing control device that can respond to changes in operating conditions, especially changes in engine load, by controlling the valve timing of an exhaust valve. That's true.

(Configuration of the present invention) The above object of the present invention is achieved by the following configuration. That is, the present invention provides an engine equipped with a load detection means for detecting engine load, and an intake valve and an exhaust valve that open and close an intake port and an exhaust port provided in one cylinder at a predetermined timing. The present invention is characterized in that a valve timing changing means is provided for changing the valve opening timing in a normal engine operating range to a later side than in a low load range and a high load range.

The configuration of the present invention will be explained with reference to FIG.

The engine according to the present invention includes at least one intake valve and one exhaust valve in one cylinder, and part or all of the exhaust valve has valve timing that changes depending on the operating state, for example, changes in engine load. Be changed. When the operating state is in a normal city driving state, that is, in a normal use range represented by a medium load range, the valve timing changing means changes at least the opening timing of the exhaust valve to a low load range such as during idling or a high speed range. Set to a slower side than in high load areas such as when driving. Preferably, at least the opening timing of the exhaust valve is set to a standard state in a low rotation and low load region, and is set to be more advanced, that is, earlier, than that in a high rotation and high load region.

Note that a conventionally known variable mechanism can be used as a variable mechanism for changing the valve timing. Furthermore, the engine speed can also be incorporated into the detection of the operating state.

(Effects of the Present Invention) According to the present invention, since the opening timing of the exhaust valve in the normal use region is shifted to the delayed side, the expansion ratio can be increased and fuel efficiency can be improved.
Furthermore, in a high load region, the opening timing of the exhaust valve is advanced, so exhaust efficiency is improved, and high output can thereby be obtained. Preferably, in addition to controlling the exhaust valve as described above, the closing timing of the intake valve is controlled to be delayed during high-speed, high-load operation, thereby reducing the pushing effect at the end of the intake stroke due to the inertia of a large amount of intake air. As a result, filling efficiency can be increased and even higher output can be obtained. Furthermore, in the low load region, the valve timing of the exhaust valve is in a standard state, and in this state, the overlap period between the exhaust valve and the intake valve is relatively short, so that the remaining burnt gas in the combustion chamber is reduced. The amount can be reduced and combustion can be stabilized.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 2, the engine 10 of this example has a plurality of cylinders 12, each cylinder 12
is provided with two intake ports: a primary side intake port 16 communicating with the primary side intake passage 14 and a secondary side intake port 20 communicating with the secondary side intake passage 18. , the primary side intake valve 22 and the secondary side intake valve 24 are respectively combined. There are also two exhaust passages 26 on the exhaust side,
28, and a first exhaust valve 34 and a second exhaust valve 36 combined therewith.
are provided for each.

The intake valves 22, 24 are combined with cams 40 and 42 formed on the camshaft 38.

The exhaust valves 34 and 36 are combined with cams 46 and 48 formed on a camshaft 44, respectively. The camshafts 38 and 44 are rotationally driven by a timing belt 50 that is synchronized with a crankshaft (not shown).

The primary side intake passage 14 and the secondary side intake passage 18 are branched from the intake passage 15, and the intake passage 15 is provided with a throttle valve 52. An on-off valve 54 is provided in the secondary intake passage, and the on-off valve 54 is
Preferably, it is opened during high load operation. A variable mechanism 57 is provided to change the valve timing of the second exhaust valve 36. If FIG. 3 is also referred to, the variable mechanism 57 is connected to the cam shaft 44.
a rotating member 59 rotatably supported by a rotating member 59; a drive shaft 61 attached to the rotating member 59;
an operating member 63 that rotates the rotating member 59 around the camshaft 44 by operating the operating member 1;
It is equipped with a motor 65 that operates left and right in FIG. The rotating member 5 is provided with a fitting hole 59a in which the tappet 67 is slidably accommodated.
The tappet 67 is interposed between the cam 48 and the valve stem 36a of the second exhaust valve 36, and is normally pushed upward by a spring 69.
When the valve 8 rotates, the tappet 67 is pressed down while contacting the cam surface, and the acting force from the cam 48 is transmitted to the valve stem 36a, thereby opening and closing the second exhaust valve 36.

When the motor 65 operates, the operating member 63 moves left and right, thereby causing the drive shaft 61 to move toward the rotating member 5.
9 around the camshaft 44. When the rotating member 59 rotates, the tapepet 67 accommodated therein
moves, the relative position between the tappet 67 and the cam 48 changes, and the contact timing shifts, causing the second exhaust valve 3
The opening/closing timing of 6 changes. In this example engine,
A variable mechanism 56 that changes the valve timing of the secondary intake valve 24 is provided.
6 is a rotating member 58, a drive shaft 60, and an operating member 6
2. Motor 64, Tappet 66, Spring 68
The operation thereof is the same as that of the variable mechanism 57, so a description thereof will be omitted.

As shown in FIG. 4, a control device 71 preferably composed of a microcomputer (hereinafter referred to as microcomputer) is provided to drive the motor 65. The control device 71 receives a rotation speed signal S ₁ output from a rotation speed sensor 70 that detects the engine rotation speed.
Then, a load signal S ₂ output from a load sensor 72 that detects the engine load is input. Control device 71 outputs control signals to motors 64 and 65.
The motors 64 and 65 are reversible motors, and rotate the gears 74 and 75 by a predetermined amount in a predetermined direction in response to the control signal, and move the operating members 62 and 63 left and right to open the secondary intake valve 24 and the second exhaust valve. Change the valve timing of valve 36. The positions of the operating members 62 and 63, that is, the valve timings of the secondary intake valve 24 and the second exhaust valve 36, are determined by the position sensor 7.
6 and 77, and this signal is input to the control device 71. The control details when a microcomputer is used as the control device 71 are shown in FIG. 5 in a flowchart format.

The microcomputer 71 first calculates the rotation speed R from the rotation speed signal _S1 , and then calculates the engine load P from the load signal _S2 . Inside the microcomputer 71
A map representing the relationship between the rotational speed R, the load P, and the target position T of the operating member 63 is preloaded in the RAM, and the map representing the relationship between the rotational speed R and the engine load P calculated above is used to set the corresponding target position of the operating member 63. Position T
is read. Next, the current position Ps of the operating member 63 is calculated based on the signal _S3 from the position sensor 77. Then, the deviation D between the target position T and the current position Ps is calculated. When the deviation D is zero, the motor 64 is not driven and the operating member 63 is not operated.
When the deviation D is positive, the motor 65 is driven, and the operating member 63 is operated in a direction corresponding to the value. If the deviation D is negative, the motor 65 is driven in accordance with the value, and the operating member 63 is returned by a predetermined value. The variable mechanism 56 for the secondary intake valve is independently controlled by inputting the same rotational speed signal S ₁ and load signal S ₂ as described above.

(Control Example) An example of the control of this example will be described with reference to FIGS. 6 and 7.

When the engine is in a low rotation and low load region including idling, the valve timing of the second exhaust valve 36 is set to the standard state as shown by line a in FIG. 6. The valve timing of the secondary intake valve 24, which is disposed opposite to the second exhaust valve 36, is also set to a standard state, as shown by line b in FIG. Furthermore, as shown by line c in Figure 7, the first exhaust valve 34 is set so that its opening timing is delayed and its closing timing is the same as the standard state a of the second exhaust valve. The primary side intake valve 22, which is arranged opposite to this, is in the same state as the first exhaust valve 34 and the primary side intake valve 22, as shown by line d in Figure 7, as shown by line b in Figure 6 above. is fixed. In such a state, the overlap period is relatively short, and therefore, the amount of residual burnt gas is reduced and combustion is stabilized, so that stable engine rotation can be obtained.

In the high load region of the engine, the valve timing of the second exhaust valve 36 is determined by line a as shown by line e in Figure 6.
It is shifted to the more advanced side and accelerated. By advancing the valve opening timing in this manner, exhaust efficiency improves, and thereby high output can be obtained. In this case, since the valve timings of the two exhaust valves 34 and 36 are shifted, the valve opening time becomes substantially longer, and the exhaust efficiency can be effectively improved.
In addition, if the valve timing of the secondary intake valve 24 is shifted to the delayed side as shown by line f in Figure 6 in a high-load, high-speed region, the valve opening timing on the intake side becomes longer. A pushing effect of the intake air at the end of the intake process is generated, making it possible to increase the filling efficiency and obtain high output.

In the normal use range, which is represented by the mid-speed and medium-load range and is frequently used in city driving, etc., the valve timing of the second exhaust valve is set in the high-load range (line e) and the low-load range, as shown by line g in Figure 6. On the later side of (line a), the valve opening timing is set to be the same as the opening timing of the first exhaust valve 34 with fixed valve timing. Therefore, the opening timing of the second exhaust valve is delayed and the expansion ratio can be increased. This improves thermal efficiency and improves fuel efficiency.

In the above example, each cylinder has 2
Although an engine having two intake and exhaust ports has been described, the present invention can be similarly applied to an engine having one intake and exhaust port.

[Brief explanation of drawings]

Figure 1 is a claim correspondence diagram of the present invention, Figure 2 is
A partial plan sectional view of an engine according to an embodiment of the present invention,
3 is a longitudinal sectional view of the engine shown in FIG. 2, FIG. 4 is an explanatory diagram of a system for operating the variable mechanism, and FIG. 5 is a flowchart showing an example of valve timing control of the present invention. Figure 6 shows the secondary intake valve,
FIG. 7 is an explanatory diagram showing the valve timing of the second exhaust valve, and FIG. 7 is an explanatory diagram showing the valve timing of the primary side intake valve and the first exhaust valve. Explanation of symbols: 10...Engine, 12...Cylinder, 22...Primary side intake valve, 24...Secondary side intake valve, 34...First exhaust valve, 36...Second exhaust valve, 38, 44...camshaft, 40, 42, 46,
48...cam, 50...timing belt, 5
8, 59... Rotating member, 64, 65... Motor,
66, 67... Tappet.

Claims (1)

[Claims] 1 load detection means for detecting engine load; 1
In an engine equipped with an intake valve and an exhaust valve that open and close the intake port and exhaust port provided in one cylinder at a predetermined timing, at least the opening timing of the exhaust valve is set in the low-load region and the high-load region in the normal operating range of the engine. 1. A valve timing control device for an engine, comprising a valve timing changing means for setting the valve timing to a later side than the valve timing.