WO1990014505A1 - Device for automobile motor timing system with variable valve lifts - Google Patents

Abstract

The valve push rod is made up of three cups (1, 2 and 3) as shown in figure 1, and operates in two modes. At low engine speed, the cam actuates the cup (1), and, in the first stage, only the spring (4) is flattened. After this free stroke, the cam compresses the valve by means of the three cups (1, 2 and 3) pressing one against the other. At high engine speed, the pressurized oil coming through the channel (7) raises the cup (2), thus eliminating the space between the cups (1) and (2). A check valve keeps the oil captive between the cups (2) and (3), and when the the cam compresses said cups (1) and (2), the captive oil transmits movement to cup (3) and the valve is pressed down.

Description

 Device allowing variable valve and lift distribution of valves for automobile engines.

It consists of a three-part pusher transmitting the movement from the cam to the valve. It replaces the pusher (or rocker) usually used.

In all relatively high-speed engines like car engines, the intake valves open before top dead center and close after bottom dead center, while exhaust valves open before bottom dead center and close after top dead center. The reasons for this are on the one hand the inertia of the gases which, in the intake phase, for example, take a certain time to set in motion in the manifold when the piston begins its suction stroke. At the end of this one, it is useful to exploit the kinetic energy of the aspirated gases to perfect the filling of the cylinder, when the piston has already started its ascent upwards; on the other hand, it is necessary to take into account the relative slowness of the opening of the valves; if you want the gases to have a large flow section from the start of the intake or exhaust phase, you must anticipate the start of valve lift.

It is obvious that the faster the motor turns, the greater the phase shift relative to the theoretical cycle, all other things being equal. In automotive jargon, this phase shift is called the "crossing" of the distribution because it means that around the top dead center preceding the suction phase, the opening of the intake valve being anticipated and the closing the exhaust valve being delayed, the intake and exhaust valves will be open for a while. Unfortunately, the diagram is fixed and is only optimum for a well-determined speed of the cylinders. By increasing the crossing, this maximum speed is shifted which corresponds to the best conditions for filling the engine. By increasing the crossing, this speed is shifted upwards and the engine power is increased at the same time; by reducing it, we move this regime towards low and we improve the torque at low speed at the expense of maximum power.

The ideal would therefore be a distribution, the characteristics of which would vary according to the engine speed. The system presented allows this by varying the opening time and the lifting of the valves in operation.

The system operates in two modes, corresponding

 respectively at low and high engine speeds.

- In high speed engine phase. (figure 2)

 The device (5) will be actuated to allow pressure

 of oil to be introduced between the cups (2) and (.3) via the orifice (7).

This oil pressure will be higher than the spring (4) and

necessarily significantly lower than the valve spring.

 The bucket (2) lifts and comes into contact with the bucket (1).

The oil between the space of the cups (2) and (3) is

trapped by a non-return valve of the device (5).

 When the cam begins its compression phase from the pusher to

point B and up to point B ', the three cups and the oil

captive transmit movement to the valve.

The crushing of the valve will therefore be equal to the time corresponding to the rotation of the cam from point b to B ', i.e. 320 ° rpm

 Similarly, the crushing of the valve will be worth the entire profile of the cam; or 15 m m.

 - In engine phase at low speed. (figure 3)

When the cam begins its compression phase of the pusher, we see that the bucket (1) initially compresses the spring (4), this will only have happened at point A and up to point A '

that it will activate the three buckets at the same time and consequently the crushing of the valve.

The crushing of the valve will therefore be limited to the time corresponding to the rotation of the cam from point A to A '; i.e. 260 ° rpm / engine.

Similarly, the crushing of the valve will be worth the profiling of the cam deducted from the space lost between the buckets (1) and (2); or 10 mm.

There is no oil between buckets (2) and (3) because

it can escape through the device (5).

"The 260 ° and 320 ° angles as well as the 10 and 15 mm lifts are purely indicative." Legend.

FIG. 1 shows the device in neutral position,

FIG. 2 in the high engine speed phase,

Figure 3 in low engine speed phase.

1. cam bucket

 2. intermediate bucket

 3. valve cup

 4. spring now buckets 1 and 2 apart

 5. device that will control the pusher, in this case it is a drawer dispenser, but all types of existing dispenser are valid.

 6. pastiel allowing basic adjustment of bucket 3

 7. pressure oil inlet or oil outlet

8. in high engine speed phase this orifice constitutes a safety device preventing oil trapped in buckets 2 and 3 from amplifying

crushing of the valve during high expansion.

 9. pressurized oil supply

 10. pressureless oil return

 11. groove allowing the incoming oil under the entire surface of the bucket 2.

 12. orifice avoiding overpressures or depressions

Claims

Claim. Device for variable valve and lift distribution of valves for automobile engines. The valve lifter consists of three cups, as shown (1), (2) and (3) in Figure 1. It works in two modes,  - In low engine speed phase, the cam actuates the bucket (1), initially, only the spring (4) is crushed. After this free stroke, the cam compresses the valve by through the three cups (1), (2) and (3) pressing one on the other.  - In high engine speed phase, an oil pressure coming through the channel (7) comes to raise the bucket (2) and removes the space between the buckets (1) and (2), a non-return valve maintains the oil trapped between the buckets (2) and (3).  When the cam compresses the cups (1) and (2), the trapped oil transmits the movement to the cup (3) and the valve crashes.