JPH065017B2 - Valve timing controller for engine with supercharger - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an exhaust valve in an engine equipped with an exhaust turbocharger.

(Prior Art) Conventionally, in an engine equipped with an exhaust turbocharger, the valve timing of the exhaust valve is variable and the valve opening timing of the exhaust valve is variable in the low speed range, as seen in Japanese Patent Laid-Open No. 59-131714. Techniques for speeding up are known.

However, to open the exhaust valve early in the low speed range
The valve opening period becomes longer, the average flow velocity of exhaust gas becomes slower,
The turbine efficiency is low and a sufficient supercharging effect cannot be obtained.

In particular, when the total exhaust gas amount is constant, it is necessary to extend the exhaust valve open period so that this exhaust gas is discharged for a long time, which reduces the exhaust gas flow rate per hour and reduces the turbine work load. As a result, the intake supercharging amount is small and the supercharging effect cannot be sufficiently obtained. On the other hand, if the exhaust valve is opened for a short time by shortening the exhaust valve opening period,
The exhaust gas flow rate per unit time is increased, which increases the turbine work amount and the intake supercharging amount to obtain a good supercharging effect.

Regarding shortening the opening period of the exhaust valve, advancing the closing time means closing the exhaust valve while the piston is rising, increasing the amount of exhaust gas remaining in the combustion chamber, and It has a problem that the property is deteriorated.

(Object of the Invention) In view of the above circumstances, an object of the present invention is to provide a valve timing control device for an engine with a supercharger, which improves turbine efficiency in a low speed range and obtains good supercharging performance. It is a thing.

(Structure of the Invention) In the valve timing control device of the present invention, when the low speed state of the engine is detected by the low speed detection means, the valve opening timing of the exhaust valve is delayed to the time when the piston is raised by a predetermined amount after passing through the bottom dead center. A valve timing control means for shortening the valve opening period as compared with the valve opening period in other operating states is provided.

(Effects of the Invention) According to the present invention, in the low speed region, the exhaust valve is opened by delaying the time when the exhaust valve is opened by a predetermined amount after passing through the bottom dead center and shortening the exhaust period. Since the exhaust gas is compressed and discharged in a short time, the flow velocity of the exhaust gas is increased and the flow rate per hour is increased, the turbine efficiency is improved in the low speed range, and a good supercharging effect is obtained. Also, by obtaining the shortening of the exhaust period by delaying the opening timing of the exhaust valve after the bottom dead center, it is possible to maintain good combustibility by ensuring good scavenging without the exhaust gas remaining in the combustion chamber. Is something that can be done.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

Example 1 An overall schematic configuration of this example is shown in FIG. 1, and two intake ports 3 and 4 and two low speed and high speed exhaust ports are provided for four cylinders 2 provided in an engine body 1. 5 and 6 are opened, the intake ports 3 and 4 are opened and closed by the first and second intake valves 7 and 8, and the low speed and high speed exhaust ports 5 and 6 are opened by the first and second exhaust valves 9 and 10. It is opened and closed. Intake passage 11 is provided in intake ports 3 and 4.
And the exhaust passage 12 is connected to the exhaust ports 5 and 6. An exhaust turbocharger 13 is provided which supercharges intake air by driving a blower 13b installed in the intake passage 11 by a turbine 13a installed in the exhaust passage 12 and driven by exhaust gas.

The first exhaust valve 9 that opens and closes the low speed exhaust port 5 and the second exhaust valve 10 that opens and closes the high speed exhaust port 6 have different valve timings, and the operation of the second exhaust valve 10 is selectively stopped. As a result, valve timing control means 14 for variably controlling the exhaust timing of the exhaust valves 9 and 10 as a whole is additionally provided. The valve timing control means 14 includes a valve inactivating mechanism 15 arranged for the second exhaust valve 10 on the high speed side, and a controller 16 for operating the valve inactivating mechanism 15. A detection signal from the low speed detection means 17 for detecting the low speed operation state is input.

That is, the valve timing of the first exhaust valve 9 is set to the second
As shown by the curve I in FIG. 3A, the piston after the bottom dead center BDC opens at the late opening timing EO ₁ when it rises by a predetermined amount, and closes at the closing timing EC ₁ after the top dead center TDC. On the other hand, the valve timing of the second exhaust valve 10 for high speed is, as shown by the curve II in FIG. 2 (A), opened at the early opening time EO ₂ before the bottom dead center BDC and almost after the top dead center TDC. Same closing time E
It closes to O ₂ .

Then, when the low speed detecting means 17 detects the low speed operation state of the engine, the valve timing control means 14 operates the valve inactivating mechanism 15 to maintain the second exhaust valve 10 in the closed state, and to open the exhaust timing. The valve timing is controlled so that the timing is delayed and the valve opening period is shortened. That is, in the medium and high speed regions other than the low speed region, as shown in FIG.
Opens and closes, and the opening timing is the second exhaust valve 10 (curve II)
It opens at an early opening time EO ₂ before the bottom dead center BDC and closes at a closing time EC ₂ after the top dead center TDC. On the other hand, in the low speed range, the second exhaust valve 10 does not open as shown in FIG. 2 (B), and at the opening timing, the first exhaust valve 9 (curve I) causes the piston after the bottom dead center BDC to reach a predetermined amount. Late opening EO rose
Open to _1, are those close to closing timing EO ₁ after top dead center TDC, in which opening timing is slow opening period becomes shorter.

FIG. 3 shows the exhaust gas flow velocity with respect to the valve timing of the exhaust valve. The curve A indicates the exhaust gas flow rate in the low speed range and the exhaust gas in the case of a short valve opening period due to the valve timing of the curve I in FIG. This is a change in flow velocity, and a large flow velocity is obtained throughout the valve opening period. On the other hand, the curve B is the change in the exhaust gas flow velocity in the case where the exhaust valve has a long opening period as shown by the curve II in FIG.
After that, the flow velocity drops sharply.

The turbine work amount with respect to the exhaust gas flow rate as described above has the characteristic of FIG. 4, and according to the valve timing with a large flow rate as shown by the curve A, the exhaust gas flow rate per hour is large, so the turbine work The amount increases,
This allows efficient supercharging of intake air, and the curve B
With such a flow velocity characteristic, the turbine work is small and the supercharging efficiency is reduced. In the medium and high speed range,
Since the exhaust gas amount increases and the entire amount is not exhausted with good scavenging property in a short valve opening period, opening and closing the exhaust valve with the valve timing characteristics of curve II in Fig. 2 accelerates the opening timing of the exhaust valve. In this way, the valve opening period is lengthened to obtain good discharge characteristics. In this case, since the exhaust gas amount is increasing, a large exhaust gas flow velocity can be obtained throughout the valve opening period, the turbine work amount is high, and efficient supercharging can be performed.

The specific structure of the valve inactivating mechanism 15 is shown in FIGS. 5 and 6. The air supply valve 8 and the second exhaust valve 10 are each biased in the valve closing direction by a valve spring 31, and a rocker arm 33 is installed between the cam shaft 32 and the rocker arm 33.
An intermediate position of the rocker arm 33 is supported by a movable fulcrum member 34 on the second exhaust valve 10 side and a fixed fulcrum member 35 on the intake valve 8 side. The movable fulcrum member 34 and the fixed fulcrum member 35 are held by a support block 36, and an eccentric cam 37 is provided on the upper part of the movable fulcrum member 34, and a pressure introduced into the movable fulcrum member 34 by the rotation of the eccentric cam 37. The oil path is changed to perform switching control between a valve operating state in which the fulcrum position is fixed and a valve inoperative state in which the fulcrum position is floated.

The internal structure of the movable fulcrum member 34 is shown in FIG. 6 (valve operating state). The movable fulcrum member 34 is slidably inserted into the support block 36, the lower end side is formed into a spherical shape and contacts the rocker arm 33, the inside is formed into a cylindrical shape, and the rod 38 is projectingly provided at the bottom portion, and the spring 39 is provided. It is housed. A tubular intermediate member 40 fitted into the movable fulcrum member 34.
The spring 39 comes into contact with the lower surface and is urged upward, and an opening is formed in the center of the lower surface. An oil sump plate 41 and a first plunger 42 are provided in the intermediate member and 40.
Is slidably inserted, and a lower oil chamber 43 is formed between the first plunger 42 and the oil sump plate 41. First above
An upper oil chamber 45 is formed by inserting the second plunger 44 inside the plunger 42, and a pressure receiving plate 46 that abuts against the eccentric cam 37 is provided at the upper end of the intermediate member 40. A spring 47 is compressed in the upper oil chamber 45, and a check valve 49 for opening and closing the central orifice of the second plunger 44 is provided. A relief member 50 having pins 50a and 50b projecting vertically is housed in the upper portion of the second plunger 44 by being urged upward, the lower pin 50b faces the check valve 49, and the upper pin 50a is the pressure receiving plate. It penetrates upward 46 and engages with the groove 37a of the eccentric cam 37, and when it moves downward, the check valve 49 is opened and the upper drain passage 46a is opened.

The support block 36 is formed with a pressure oil supply passage 51 to which pressure oil from an oil pump is supplied, and the pressure oil is an upper pressure oil formed above and below the intermediate member 40 from the pressure oil passage 34a of the movable fulcrum member 34. The lower pressure oil port 40b is selectively supplied to the port 40a or the lower pressure oil port 40b, the upper pressure oil port 40a is communicated with the upper oil chamber 45 and the upper drain passage 46a, and the lower pressure oil port 40b is the lower oil chamber 43 and the lower drain passage. 34b.

Describing the operation, FIG. 6 shows a valve operating state, in which the eccentric cam 37 pushes down the intermediate member 40 and the relief member 5
The pressure oil is introduced from the upper pressure oil port 40a into the upper oil chamber 45 through the check valve 49, while the lower oil chamber 43 is communicated with the lower drain passage 34b, and the upper oil chamber 45 is connected to the upper oil chamber 45. The volume is increased to push down the first plunger 42, press the rod 38 through the oil sump plate 41, and secure the fulcrum position of the rocker arm 33 to open / close the second exhaust valve 10.

Next, in order to make the second exhaust valve 10 inoperative, the eccentric cam 37 is rotated by 180 °, the intermediate member 40 is moved upward by the spring 39, and the relief member 50 is moved downward to check the check valve 49. Is released, and the pressure oil in the upper oil chamber 45 is relieved from the upper drain passage 46a. As the intermediate member 40 rises, pressure oil is introduced from the lower pressure oil port 40b to the lower oil chamber 43, and the lower oil chamber 43
, The volume of the upper oil chamber 45 is made constant, and the intake of air is prevented. Further, the intermediate member 40 is located apart from the rod 38 and is located above, and the movable fulcrum member 34 can be floated with respect to the intermediate member 40 by the action force of the spring 39.
6, the rocker arm 33 swings around the second exhaust valve 10 side as a fulcrum, and the second exhaust valve 10 is maintained in the closed state and in the valve inoperative state.

Embodiment 2 This embodiment is shown in FIG. 7, and is different from the first embodiment shown in FIG. 1 in the exhaust gas inflow passage for the turbine 13a of the exhaust turbocharger 13 and the partition wall 12a (exhaust passage). Two
0 and a shutter valve 21 are provided, and the shutter valve 21 is opened / closed by an actuator 22 which is operated by a control signal from the controller 16. Other than that, the structure is the same as that of FIG. 1 and the valve timing is the same as that of FIG.

The shutter valve 21 is closed in the low speed range to close the turbine 1.
The exhaust gas inflow passage 12a to 3a is narrowed to increase the gas flow velocity to increase the turbine efficiency, while it is opened in the middle and high speed regions where the exhaust gas flow rate increases and exhausted to the turbine 13a by the wide exhaust gas inflow passage 12a. Gas is introduced. By operating the shutter valve 21 and the valve timing control means 14, the turbine efficiency in the low speed range is further improved.

Embodiment 3 This embodiment is shown in FIG. 8 and includes each cylinder 2 of the engine body 1.
An intake port 24 that is opened and closed by an intake valve 23 and an exhaust port 26 that is opened and closed by an exhaust valve 25 are opened in each. The intake passage 11 is connected to the intake port 24, and the exhaust passage 12 is connected to the exhaust port 26. An exhaust turbocharger 13 that supercharges intake air is provided by driving a blower 13b provided in the intake passage 11 by a turbine 13a provided in the exhaust passage 12 and driven by exhaust gas.

The exhaust valve 25 is provided with valve timing control means 27 for variably controlling the valve timing.
The valve timing control means 27 includes a variable valve timing mechanism 28 arranged in the valve mechanism of the exhaust valve 25,
A controller 29 for operating the variable valve timing mechanism 28 is provided, and a detection signal from the low speed detection means 17 for detecting a low speed operation state is input to the controller 29.

The valve timing control means 27 controls the valve timing so as to delay the valve opening timing of the exhaust valve 25 and shorten the valve opening period when the low speed detecting means 17 detects the low speed operation state of the engine as in the previous example. It is a thing.

That is, the variable valve timing mechanism 28 includes, for example, a first cam for the low speed range and a second cam for the medium and high speed ranges, and the two types of cams are output by a signal from the controller 29 according to the operating state of the engine. Select is operated. As shown by the curve I in FIG. 9, the valve timing by the first cam selected in the low speed range is the slow opening timing EO ₁ when the piston after the bottom dead center BDC rises by a predetermined amount.
It opens at the closing time EC ₁ after the top dead center TDC. On the other hand, the valve timing by the second cam selected in the middle and high speed range is opened at the early opening time EO ₂ before the bottom dead center BDC and is reached at the top dead center TDC as shown by the curve II in FIG.
It is to be closed at almost the same closing timing EC ₂ later.

As a result, the turbine efficiency in the low speed range is improved as in the first embodiment.

In this embodiment as well, the shutter valve 21 is provided in the exhaust gas introduction passage 12a for the exhaust turbocharger 13 as in the second embodiment, and the exhaust passage is throttled to the low speed range to further improve the turbine efficiency. You may do it.

In addition, the valve timing of the exhaust valve can be variably controlled by appropriately adopting a known valve timing control means other than the above-mentioned embodiment.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram showing a first embodiment of the present invention, FIGS. 2A and 2B are characteristic diagrams showing valve timing of an exhaust valve, and FIG. 3 is a relationship between exhaust valve timing and exhaust gas flow velocity. FIG. 4 is a characteristic diagram showing the relationship between exhaust gas flow rate and turbine work, FIG. 5 is an upper sectional view of an engine showing an example of a valve inoperative mechanism, and FIG. FIG. 7, FIG. 7 is an overall schematic configuration diagram showing a second embodiment of the present invention, FIG. 8 is an overall schematic configuration diagram showing a third embodiment of the present invention, and FIG. 9 is a third embodiment. It is a characteristic view which shows an exhaust valve timing. 1 ... Engine body, 2 ... Cylinder 5, 6, 26 ... Exhaust port 9, 10, 25 ... Exhaust valve 11 ... Intake passage, 12 ... Exhaust passage 13 ... Exhaust turbocharger 13a ... Turbine, 13b ... Blower 14,27 ... Valve timing control means 15 ... Valve inoperative mechanism 16 ... Controller, 17 ... Low speed detection means 28 ... Valve timing variable mechanism

Claims (1)

[Claims] 1. An engine equipped with an exhaust turbocharger that supercharges intake air with a blower driven by a turbine driven by exhaust gas, and a low speed detection means for detecting a low speed state of the engine, and the low speed detection means. When a low speed operation state is detected by, the valve opening timing of the exhaust valve is delayed until the piston rises by a predetermined amount after passing through the bottom dead center, and the valve opening period is shortened compared to the valve opening period in other operating states. A valve timing control device for an engine with a supercharger, comprising: