EP0640749A1

EP0640749A1 - Device for controlling a valve timing for an internal combustion engine

Info

Publication number: EP0640749A1
Application number: EP94113507A
Authority: EP
Inventors: Eiji Shirai; Atsushi Sato; Takayuki Kurumi; Katsuhiko Eguchi; Ichiro Kimura; Koji Hotta; Hiroyuki Nakadouzono
Original assignee: Aisin Seiki Co Ltd
Current assignee: Aisin Corp
Priority date: 1993-08-31
Filing date: 1994-08-30
Publication date: 1995-03-01
Also published as: JPH0771278A

Abstract

Device for controlling a valve timing for an internal combustion engine includes a cam selectively operating mechanism for selecting and operating one of low speed cams and high speed cams which have different advances or phase angles and are located on an intake cam 4 and an exhaust cam 5, respectively for a second cylinder and a third cylinder while the engine is in a cold and a range of low speeds, a rotation advance control mechanism for controlling a rotation advance of an exhaust cam on a cam shaft 7 in response to engine speeds variation, a cylinder control mechanism for interrupting an operation of first and fourth cylinders corresonding to partial engine loads, and a volume displacement pump for supplying oil in the form of steps to the rotation advance control mechanism and the cylinder control mechanism according to the engine speeds.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a device for controlling a valve timing of opening and closing exhaust valve and intake valve for an internal combustion engine.
A conventional valve timing device is disclosed in the laid open publication of JP 4-194331 wherein at engine high speeds and engine light loads a small amount of overlap of open periods of the intake valve and the exhaust valve is required and under the engine cold condition the small amount of such the valve overlap is also required, but except these cases the large amount of overlap of open periods the intake valve and the exhaust valve is desired, as shown in Figs. 19 and 20.
In the reciprocating type internal combustion engine having the valve timing device of the conventional type, the overlap of open periods of the intake valve and the exhaust valve allows a combustion air taken into a combustion chamber through the intake valve to be exhausted through the exhaust valve toward an exhaust pipe at the engine low speeds, the engine light loads and the engine cold, thereby reducing the engine output.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned drawbacks encountered in the prior art, inventors of the present invention recognize a technical conception to minimize an amount of overlap of open periods of the intake valve and the exhaust valve at the engine cold and the engine low speeds, so that air intake efficiency is increased and at the engine high speeds gases of HC and NOx are reduced. Further, this conception is effective in improvements of engine starting performance and fuel consumption.
A device for controlling a valve timing for an internal combustion engine which varies an amount of overlap of open periods of an intake valve and an exhaust valve comprises a valve timing control mechanism to minimize the amount of said overlap at the engine cold. By minimizing the amount of overlap of open periods of the intake valve and the exhaust valve the exhaust valve is closed during asuction stroke so that air taken into an combustion chamber is not discharged into an exhaust passage. The valve timing control mechanism permits to minimize an amount of overlap of open periods of the intake valve and the exhaust valve at the engine low speeds, so that air intaken into the combustion chamber does not exit to the exhaust passage because the exhaust valve is closed during a suction stroke.
These objects and advantages of the invention will become more apparent from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view showing a structural relation between intake-cam and exhaust-cam of a first enbodiment of the present invention which are used in a first and third cylinders;
Fig. 2 is a cross-section showing a cam actuator mechanism of the first embodiment;
Fig. 3 is a vertical cross-section of an intake valve and an exhaust valve;
Fig. 4 is a valve timing diagram of the first embodiment;
Fig. 5 is a plain view an intake-cam shaft and an exhaust-cam shaft of the first embodiment;
Fig. 6 is a vertical cross-section of a rotation advanced angle control mechanism of the first embodiment;
Fig. 7 is a cross-section of a cylinder control mechanism of the first embodiment;
Fig. 8 is a partially enlarged view of the mechanism as shown in Fig. 7;
Fig. 9 is a flow rate diagram of a valiable displacement pump of the first embodiment;
Fig. 10 is a schematic view showing a structural relation between intake-cam and exhaust-cam of a first embodiment of the present invention which are used in a second and fourth embodiments;
Fig. 11 is a view showing an oil circuit for each cylinders of the first embodiment;
Fig. 12 is a block diagram showing a control circuit of the first embodiment;
Fig. 13 is a cross-section showing a modification of the first embodiment;
Fig. 14 is a view showing an oil circuit of the first embodiment;
Fig. 15 is a plain view showing an intake-cam and an exhaust-cam of a second embodiment of the present invention;
Fig. 16 is a valve timing diagram of the second embodiment;
Fig. 17 is a plain view showing an intake-cam and an exhaust-cam of the third embodiment;
Fig. 18 is a valve timing diagram of the third embodiment;
Fig. 19 is a chart for switching an amount of an overlap of valves at an engine cold condition in a prior art; and
Fig. 20 is a diagram showing a switching patern of an amount of overlap of a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

A device (see Figs. 1 - 4) for controlling a valve timing of open periods of an intake valve 2 and an exhaust valve 3 for are internal combustion engine 1 according to a first embodiment includes a cam selectively operating means 10 to selectively operate an intake cam 4 and an exhaust cam 5 which have different phases and are located on low speeds cams 11, 12 and high speeds cams 13, 14, corresponding to a second cylinder and a third cylinder, so that an amount of the overlap of the opening of the valves 2, 3 is minimized. The valve timing device further includes a rotation advance control means 20 to control an advance of the exhaust cam located on the exhaust cam shaft of according to the engine operating condition, a cylinder control means 40 to interrupt an operation of a first cylinder and a fourth cylinder the engine 1 at the engine partial loads, and a volume displacement pump 50 to supply oil in the form of step to said rotation advance control means 20 and said cylinder control means 40 according to the engine speeds.
The cam selectively operating means 10 comprises the low speeds cams 11, 12 and the high speeds cams 13, 14 having the intake-cam 4 and the exhaust cam 5, an exhaust lifter 16 engaging with the exhaust cam 5, and an intake lifter 15 engaging with the intake cam 4, so that phase and amount of strokes of the valves 2, 3 are controlled.
As shown in Fig. 1, the low speeds cams 11, 12 are so constructed that an amount of overlap of open periods of two intake valves 2 and one of the exhaust valves 3 is minimized. This is shown in Fig. 4 (A) and (B) which illustrate relation of strokes of two intake valves 2 and one of two exhaust valves 3 at the engine starting performance and the engine low speeds.
The high speeds cams 13, 14 are formed between two low speeds cams 11, 12 to provide a constant overlap of open periods of two intake valves 2 and two exhaust valves 3 at the engine high speeds. The relation of these valves 2, 3 are illustrated in Fig. 4 (C) and (D).
The intake lifter 15 and the exhaust lifter 16 are disposed in a hole formed on a cylinder head (refer to Fig. 2). The lifters 15, 16 have oil pressure chambers 15c, 16c into which oil pressure is not fed or a constant volume of oil is fed from a volume displacement pump 50 at the engine starting and engine low speeds, and U-shape pins P1, P2, P3 which receive biasing forces of springs 15S, 16S. When the pins P1, P2, P3 are moved rightward (Fig. 2(A)), the pin P2 is placed in the holes 15H, 16H and sliders 15D, 16D engaging the high speeds cams 13, 14 are moved downward so that the high speeds cams 13, 14 are sunk in the lifters 15, 16 and only the low speeds cams 11, 12 are in slide contact with upper surfaces 15U, 16U of the lifters. Thus, the lifters 15, 16, two intake valves 2 and one the exhaust valves 3 are driven by profiles of the low speeds cams 11, 12.
The high oil pressure is supplied into the pressure chambers 15C, 16C from the volume displacement pump 50 at the engine high speeds. Since the U-shape pins P1, P2, P3 are moved rightward (Fig. 2(B)) against the biasing force of the spring 15S and the slider 15D is not moved downward, the lifters 15, 16, two intake valves 2 and one of the exhaust valves 3 are driven according to profiles of the high speeds cams 13, 14 (Fig. 3).
The rotation advance control means 20 (see Fig. 5) is connected through a gear 32 to one end of the exhaust cam shaft 7. The intake cam shaft 6 is provided at one end with a pulley 6P and at the other end with a rotating transmitting means 30 having a scissors gear 31.
The rotation advance means 20 (Fig. 6) has a chamber 20C into which high oil pressure is supplied through a passage 20P from the volume displacement pump 50 at the engine high speeds. When the high oil pressure is supplied in the chamber 20C, a cylindrical piston 20P is moved leftward against a biasing force of a spring 20S and the volume of the chamber 20C is expanded to a maximum extent. The advance of the piston 20P allows to make a relative rotation between the piston 20P and the input gear 7S by means of helical splines 20H, 20I and between the piston 20P and a case 20L by means of helical splines 20J, 20K. The rotation advance of the exhaust cam shaft 7 with respect to rotation of the input gear 32 is advanced in the maximum range as shown by a dotted line and a timing for opening or closing each valve is advanced.
At the engine starting and the engine low speeds oil pressure in the chamber 20C is drained and the piston 20 is moved rightward against the biasing force of the spring 20S. The rearward movement of the piston 20P allows to make a relative rotation between the scissors gear 32 and the piston by means of the helical splines 20H, 20I and between the piston 20P and the case 20L.
The cylinder control means 40 includes an intake lifter 41 and an exhaust lifter 42 engaging with the intake cam 4 and the exhaust cam 5 corresponding to the first and fourth cylinders of the engine 1 having the high speeds cams 13, 14 as shown in Figs. 7 - 10.
The intake lifter 41 and the exhaust lifter 42 are disposed in a hole formed on the cylinder head (refer to Fig. 8). The lifters 41, 42 have oil chamber 41C, 42C into which oil pressure is not fed or a constant-volume of oil is fed from the pump 50 at the engine starting or the engine low speeds, and U-shape pins R1, R2, R3 which receive biasing force of the springs 41S, 42S. When the pins R1, R2, R3 are moved rightward, the pin R2 is placed in holes 414, 424 and sliders 41D, 42D engaging the high speeds cams 13, 14 are moved downward so that the high speed cams 13, 14 are sunk in the lifter 41, 42 and two intake valves 2 and one of the exhaust valves are not driven to close the valves.
At the engine high speeds, the high oil pressure from the volume displacement pump 50 is supplied into the chambers 41C, 42C and U-shape pins R1, R2, R3 are moved rightward (Fig. 8(B)) against biasing force of the springs 41S, 42S, so that the sliders 41D, 42D are not moved downward. Thus, according to profiles of the high speeds cams 13, 14 the lifters 41, 42 is reciprocated to drive two intake valves 2 and one of the exhaust valves 3.
The volume displacement pump 50 is of gear pump or vane pump and connected to the lifters 15, 16 of the cam selectively operating means 10 and the cylinder control means 40 as shown in Figs. 7, 9, 11 and 12. As shown by a dotted line in Fig. 9 oil flow is increased in response to increase in the number of rotation of the engine in the range from 0 to NE1, a constant low oil flow is kept in the range from NE1 to NE2. Between NE2 and NE3 the oil flow is increased in response to increase in the engine speeds and a constant high oil flow is kept in the range over NE3 (for example 4000 rpm) Oil circuit 51 as shown in Fig. 11 is used to control cylinders of the engine 1.
Oil pressure control valves 52 - 53 are controlled by ECU inputting factors of engine speeds (for example 4000 rpm), boost pressure, throttle opening (20%), crank position, cam position and oil pressure.
The valve timing control means according to the first embodiment allows to supply a low oil flow or low pressure oil in the chambers 15C, 16C of the intake lifter 15 and the exhaust lifter 16 at the engine cold and the engine low speeds so that the pin 2 is moved in the hole 15H and the high speed cams 13, 14 are sunk in the lifters 15, 16. The low speeds cams 11, 12 are in engagement with the top surface 15U of the lifters 15, 16, and the intake valve 2 and the exhaust valve 3 are driven according to profiles of the low speed cams 11, 12 (Fig. 4(A)), to minimize the overlap of open periods of the valves.
At the engine cold and the engine low speeds, low flow oil from the pump 50 is charged in the chambers 41C, 42C of the intake lifter 41 and the exhaust lifter 42 and the pins R2 are aligned with the holes 41H, 42H by assist of the springs 41S, 42S. Thus, the sliders 41D, 42D are moved downward and the high speeds cams 13, 14 are sunk in the lifters 41, 42, so that the intake valves 2 and the exhaust valves 3 of the first and fourth cylinders are not driven to keep the closing of the valves 2, 3.
At the engine high speeds, the valve timing means allows to supply a high pressure oil from the volume displacement pump 50 into the pressure chambers 15C, 16C of the intake lifter 15 and the exhaust lifter 16 and the pins P1, P2, P3 are moved rightward (Fig. 8 (B)). The U-shape pins P1, P2 are not aligned with the holes 15H, 16H and hence the sliders 15D, 16D are unable to move downward. Thus, two intake valves 2 and the exhaust valves 3 of the second and third cylinders are driven according to profiles of the high speeds cams 13, 14 which are in contact with the sliders 15D, 16D to produce sufficient amount of overlap of open period of the valves 2, 3.
Further, at the engine high speeds, a high pressure oil of high flow rate from the pump 50 is supplied in the chambers 41C, 42C of the intake lifter 41 and the exhaust lifter 42 and the U-shape pins R1, R2 are moved rightward (Fig. 8(B)) against the biasing force of the springs 41S, 42S, so that, since the pins R1, R2 are not aligned with the holes 41H, 42H the sliders 41D, 42D engaging the high speeds cams 13, 14 are not moved downward, the high speeds cams 13, 14 are brought into contact with the sliders 41D, 42D. Thus, two intake valves 2 and the exhaust valve 3 of the first and second cylinders according to profiles of the high speeds cams 13, 14 to produce sufficient amount of the overlap of open periods of the valves 2, 3.
The valve timing control means of the first embodiment is useful in making non-operative condition of the first and fourth cylinders by means of the cylinder control means 40 at the engine cold and the engine low speeds and minimizing an amount of the overlap of the cams of the second and third cylinders, so that a suction efficiency at the engine cold and the engine low speeds is increased and improvements of starting performence and fuel consumption are realized.
The valve timing control means of the first embodiment assists to make operative condition of the high speeds cams 12, 13 of the first and fourth cylinders by means of the cylinder control means 40 and to drive the second and third cylinders through the high speeds cams 12, 13 by means of the cam selectively operating means 10 at the engine high speeds. Thus, a full overlap is produced and the decrease of HC and NOx is possible in the range of high speeds of the engine with a high output.
The valve timing control means of the first embodiment supplys oil flow on the basis of a flow pattern in the form of two steps from the volume displacement pump 50, and assists to prevent a lack of flow in the range of low speeds of the engine and over-flow in the range of high speeds of the engine.

(modification the first embodiment)

In this case the gears 31, 32 are omitted from the first embodiment as shown in Figs. 13 and 14, and oil circuit for each cylinders of the engine 1 is modified as shown in Fig. 11. The other components are the same as used in the first embodiment. This leads to cost-down of the first embodiment, but advantages of the first embodiment is kept in this case.

(second embodiment)

Refer to Figs. 15 and 16, a valve timing control means of the second embodiment includes a rotation advance control means 20 as arranged to a position of the pulley 6P and a set of scissors gears 31, 32 as arranged around center portions of the intake cam shaft 6 and the exhaust cam shaft 7. The other elements are the same as used in the first embodiment.

(third embodiment)

A valve timing control means includes a first rotation advance control means 21 connected to one end of the intake cam shaft 6 and a second rotation advance control means 22 connected to one end of the exhaust cam shaft 7, both the means 21, 22 are identical in structure to the means as used in the first embodiment.
In this case, the intake valve 2 and the exhaust valve 3 are simultaneously advanced as shown by a dotted line in Fig. 16 according to the engine condition. The exhaust valve 3 with respect to the intake valve 2 is relatively advanced as shown by a chain line in Fig. 16 and the optimum advance angle and overlap are obtained with the advantages of the first embodiment.
In the first embodiment the first and fourth cylinders of the engine are not operated under some engine conditions, but this is applied to the second and third cylinders and also to six-cylinders engine or eight cylinders engine.
In the first embodiment two intake valve 2 and exhaust valve 3 are driven by the high speeds cam 13, 14 at the engine high speeds. However, as shown in Fig. 4 (E) two intake valves 2 and one of the exhaust valves 3 can be driven by the low speeds cams 11, 12 and only the other exhaust valve 3 can be driven by the high speeds cam 14 at the engine high speeds to produce the preferred overlap.
In the first embodiment, in order to improve the starting performance of the engine a pump for supplying high pressure oil only to the rotation advance control means can be used independent of the lubricant oil pump.
While preferred embodiments of the invention has been disclosed and described, it should be appreciated that principles are applicable to other embodiments.
Device for controlling a valve timing for an internal combustion engine includes a cam selectively operating mechanism for selecting and operating one of low speed cams and high speed cams which have different advances or phase angles and are located on an intake cam 4 and an exhaust cam 5, respectively for a second cylinder and a third cylinder while the engine is in a cold and a range of low speeds, a rotation advance control mechanism for controlling a rotation advance of an exhaust cam on a cam shaft 7 in response to engine speeds variation, a cylinder control mechanism for interrupting an operation of first and fourth cylinders corresonding to partial engine loads, and a volume displacement pump for supplying oil in the form of steps to the rotation advance control mechanism and the cylinder control mechanism according to the engine speeds.

Claims

A device for controlling a valve timing for an internal combustion engine which varies an amount of overlap of open periods of an intake valve and an exhaust valve includes a valve timing control mechanism to minimize the amount of said overlap at the engine cold.
A device according to claim 1, wherein said valve timing control mechanism permits to minimize the amount of said overlap at the engine low speeds.
A device according to Claim 2, wherein said valve timing control mechanism includes a cam phase angle control mechanism to control phase angles of either one of an intake cam or an exhaust cam.
A device according to Claim 3, wherein said cam phase angle control mechanism includes a cam selectively operating mechanism to selectively operate plurality of cams which has different phase angle and are located on a cam shaft in parallel.
A device according to Claim 4, wherein a rotation advance control mechanism to control a rotation advance of either one of said intake cam or said exhaust cam in accordance to the engine operating condition is added.
A device according to Claim 5, wherein a cylinder control mechanism to select cylinder to be operated is added.
A device according to Claim 6, wherein said cam selectively operating mechanism is arranged on said intake cam and said exhaust cam, respectively.
A device according to Claim 7, wherein said rotation advance control mechanism is secured on the exhaust cam shaft.
A device according to Claim 8 , wherein a rotation transmitting mechanism is interposed between said exhaust cam shaft and said intake cam shaft to transmit a rotation.
A device according to Claim 7, wherein said rotation advance control mechanism is secured on the intake cam shaft and the rotation transmitting to transmit a rotation between said intake cam shaft and said exhaust cam shaft.
A device according to Claim 8, wherein a second rotation advance control mechanism is secured on said intake cam shaft.