EP0139566A1 - Electro-hydraulic unit for the control of the valves of an internal-combustion engine - Google Patents

Abstract

1. An electrohydraulic valve-control unit for an internal combustion engine provided with an electronic control system supplying an electric signal for opening the valve, which unit comprises : a three-way feed/drain solenoid valve (2) receiving the said electric signal ; a three-way feed/drain hydraulic distributor (4) whose switching slide valve (70) is operated by a hydraulic pilot actuator (60, 76) connected to the said solenoid valve, the said slide valve (70) having an end (76) constituting the piston of the said hydraulic pilot actuator ; the said distributor having a first aperture (32) connected to a high pressure source (36, 38), a second aperture (44) connected to a lowpressure vessel (100), and a third utilization aperture (66) ; a hydraulic power actuator (6) whose working chamber (68) is connected to the third aperture (66) of the distributor ; means (93) for returning the piston (90) of the said actuator to the rest position ; means (10) for connecting, in respect of thrust, the rod (92) of the said actuator to the stem (12) of the valve (14) which is to be controlled ; the three components - solenoid valve (2), hydraulic distributor (4) and power actuator (6) being disposed side by side in a single unit mounted on an engine component (8) fastened to the cylinder head (16) of the engine ; said control unit being characterized : in that, in the absence of the electric signal for the opening of the valve, the solenoid valve (2) is in the feed position and subjects the piston (76) of the hydraulic pilot actuator to the high pressure, while when it is energized by the said electric signal, the said solenoid valve assumes the drain position and establishes the low pressure on the said piston (76) ; and in that the other end (78) of the slide valve (70) is always subjected to the high pressure, whereby the slide valve (70) moves to the position in which it feeds the power actuator (6), in response to the said electric signal, through the action of a fall in pressure on the piston (76).

Description

The present invention relates to internal combustion engines, in particular diesel engines, and it relates to an electro-hydraulic valve control unit for engines of this kind provided with an electronic control system.

It has already been proposed, for example in French patent 2,339,748 filed on January 26, 1977, to replace the conventional mechanical control, generally obtained by means of cams, of certain functions of the engines (control of the injectors, control of the valves, control of regulation) by an electronic control system comprising one or more computers into which various operating parameters of the engine are introduced and which supply electrical signals for controlling the organs concerned of the engine.

Such electronic engine control systems have mainly been applied so far to electronic control of fuel injection, but it does not appear that electronic control of valve lift has been widely used, due to practical difficulties. of carrying out such orders.

With the classic control system for valves by cams, the valve opening law is mechanically fixed by the profile and timing of the cams which provide optimal operating conditions only for a well-defined operating point.

However, modern engines, especially supercharged engines, must have a very wide range of use (in speed and torque) and are therefore subject to very large variations in air and fuel flow rates. As a result, it is difficult to obtain correct engine operation at certain speeds, because of the valve opening law fixed once and for all by the cams. Mechanical systems have been proposed making it possible to vary the point of attack of the cams on the valve tappets, but these systems were complicated and did not have sufficient reliability.

The object of the present invention is to improve the operation of internal combustion engines by controlling and controlling the valve opening law by means of an electro-hydraulic control unit controlled by a control system. electronic, said control block having a safe operation and a small footprint which allows the housing of two blocks (one for the intake and one for the exhaust) in a cylinder head of the existing engine.

Already known, for example from German application 2,151,331, an electro-hydraulic valve control unit for an internal combustion engine provided with an electronic control system providing an electrical signal for opening the valve. This block comprises: a three-way solenoid valve, supply / purge, receiving said electrical signal; a three-way hydraulic distributor, supplied tion / purge, the switching member of which is actuated by a hydraulic pilot cylinder connected to said solenoid valve, said distributor comprising a first orifice connected to a high pressure source, a second orifice connected to a low pressure enclosure and a third orifice of use; a hydraulic power cylinder whose working chamber is connected to the third orifice of the distributor; means for returning the piston of said cylinder to the rest position; means for pushing the rod of said cylinder with the rod of the valve to be controlled; the three organs: solenoid valve, hydraulic distributor and power cylinder being joined in a single block mounted on an engine member secured to the cylinder head of the engine.

In such a known control unit, the electrical signal for excitation of the solenoid valve, constituting the order of opening of the valve, causes the pressurized hydraulic pilot cylinder of the distributor to be pressurized. Such a control unit has an insufficiently rapid response for modern diesel engines and it requires, on the other hand, a tight assembly of the electromagnet of the electro-valve which is subjected to high pressure.

The present invention overcomes these drawbacks.

According to the invention, the switching member of the hydraulic distributor consists of a slide valve in a distributor body, said drawer being hydraulically balanced. One end of said drawer is permanently subjected to high pressure, while the other end, which constitutes the piston of the pilot cylinder, is selectively subjected, via the electro-valve, to high pressure in the rest position, or else, in the power jack supply position, at the low pressure established via the solenoid valve when the latter is excited by the electrical signal produced by the electrical control system of the engine.

Thanks to this arrangement, on the one hand, the electromagnet of the electro-valve is always only subjected to low pressure and, on the other hand, the electrical signal of excitation of the electro-valve produces a electric pressure drop signal on the pilot cylinder of the distributor, which provides a faster response than a pressurization signal.

Preferably, the means for returning the power cylinder to the rest position (corresponding to the closing of the valve) are hydraulic means, the power cylinder being a differential cylinder, the second chamber of which, opposite the working chamber, is subjected permanently at high pressure.

Advantageously, in the high pressure hydraulic circuit supplying the block, a hydraulic pressure accumulator is provided and, on each block, a calibrated check valve now in the block, a residual purge pressure (low pressure) greater than atmospheric pressure. .

There is also provided, on the power cylinder, a damping system, by oil rolling, for the opening and closing limit switches of the valve. Finally it is advantageous, in an electro-hydraulic control unit according to the invention to use, as hydraulic fluid, the engine oil, suitably filtered, which avoids any special additional hydraulic circuit.

• La figure 1 est une vue en coupe du bloc de commande suivant l'invention.
• La figure 2 est une vue partielle agrandie de la partie centrale du bloc de la figure 1.
• La figure 3 est une vue schématique d'un bloc de commande unique commandant deux soupapes.

The invention will be better understood on reading the detailed description which follows and on examining the appended drawings which represent, by way of nonlimiting examples, several embodiments tion of the invention.

• Figure 1 is a sectional view of the control unit according to the invention.
• FIG. 2 is an enlarged partial view of the central part of the block of FIG. 1.
• Figure 3 is a schematic view of a single control unit controlling two valves.

The control unit comprises three parts joined and assembled to one another: an electro-valve 2, a hydraulic distributor 4 and a hydraulic power cylinder 6, this unit being mounted on the cylinder head cover 8 of the engine. The pusher 10 of the hydraulic cylinder acts in thrust on the rod 12 of a valve 14 which has been shown diagrammatically mounted in the cylinder head 16 of the engine and returned to the closed position by a valve spring 18.

The solenoid 20 of the solenoid valve 2 receives its electrical excitation signals from an electronic control system, which is not part of the invention, and which is represented schematically by a sensor 22 of the speed and position of the motor shaft 24 and by a processing unit 26 which receives the information supplied by the sensor 22 as well as other information 28 relating to other operating parameters of the motor. The processing unit 26 prepares and conditions the opening control signals of the various valves, with their instant, their duration and their optimal shape, each signal being transmitted to the electro-valve concerned via an interface. power 30, transforming the signal received from the processing unit 26 into a power current compatible with the solenoid 20 of the solenoid valve 2.

The control unit has an orifice 32 for supplying high pressure oil, preferably formed in the body 34 of the distributor 4. This orifice is connected to a high pressure source (for example of the order of 150 to 250 bars) comprising a pump 36, a hydraulic accumulator 38 and a reservoir 40. In the preferred case where engine oil is used as the hydraulic fluid for the control unit, a filter 42 is interposed, giving for example filtration at 3 microns.

The control unit also includes an orifice 44 for discharging low-pressure oil which is also preferably formed in the body 34 of the distributor.

The electro-valve 2 is a three-way valve, supply / purge, the body 46 of which is attached to the body of the distributor 34. The body 46 comprises: a high pressure inlet 48 which is permanently connected to the high pressure orifice 32 by holes 50-52 drilled in the body 34 of the distributor; a low pressure outlet 54 which is permanently connected to the low pressure orifice 44 by a bore 56 drilled in the body 34; and a use orifice 58 which is in communication with a chamber 60 of the dispenser. The shutter orqane of the solenoid valve 2 is constituted by a valve, such as a ball 62, on which the rod 64 of the solenoid 20 acts in thrust when the latter is excited. In the rest position (not excited) shown in the figure, the chamber 60 is under pressure. In the working position (energized), the ball 62 discovers the purge pipe 54 and closes the _{high-pressure} line 48, which puts the chamber 60 to the low pressure.

Thanks to this arrangement of the solenoid valve (at rest in the "supply" configuration and at work in the "purge" configuration), the solenoid 20 and its rod 64 are always subjected to the bass pressure, which avoids any sealing system and seals likely to increase friction in the solenoid valve.

The electro-valve 2 plays the role of a low-flow servovalve controlling the distributor 4 which, in turn, is a high-flow power valve controlling the power cylinder 6.

The distributor 4 is also a three-way valve which comprises, in addition to the two high pressure and low pressure orifices 32, 44 already mentioned, a third orifice 66, orifice for use, which is connected to the working chamber 68 of the jack power.

The switching member of the distributor 4 is constituted by a slide 70 which slides in a bore 72 drilled in the body 34 of the distributor. The drawer 70 has four openings 74 ₁ , 74 ₂ , ₇₄₃ , ₇₄₄ sliding in leaktight manner in the bore 72 and delimiting the switching channels of the distributor.

The actuation of the drawer 70 is hydraulically controlled by a pilot cylinder, the piston 76 of which is formed by one of the ends (the left end in FIG. 1) of the drawer which enters the chamber 60. The other end 78 of the drawer 70 also constitutes a piston, of smaller cross section than piston 76, which opens into a chamber 80 which is formed in the distributor body 34 and which is permanently subjected to high pressure by communication with a pipe 82 communicating with it. even with 50-32 holes. In the distributor's rest position, shown in FIG. 1 (solenoid 20 not excited), the two ends 76-80 of the slide are subjected to high pressure, but, due to the differences in cross section of the pistons 76, 78, the drawer is held to the right, position in which the openings 74 ₂ , 74 ₃ put the use orifice 66 in communication with the low pressure outlet 44 (purge position). A light spring 84 fixes this position of the slide, even in the absence of pressure in the high pressure fluid circuit 36, 38.

The power jack 6 comprises a jack body 86 in which a jack cylinder 88 is hollowed out receiving the piston 90 of the jack, which is connected to the pusher 10 by a jack rod 92.

Return means are provided to return the piston 90 to the rest position shown in Figure 1. These return means may be constituted by a spring, but preferably a hydraulic return means is used.

The chamber 93, located opposite the working chamber 60 relative to the piston is permanently subjected to high pressure by a line 94-96 which is pierced in the body of the jack 86 and which communicates with the high pressure line 50-32 of the distributor body.

The cylinder 6 therefore functions as a double-acting differential cylinder and it is the difference in section between the piston 90 and the rod 92 which produces the displacement of the piston towards its working position.

End-of-travel damping members are also provided for the piston of the jack, which will be described below with reference to FIG. 2.

The operation of the control unit is as follows: starting from the rest position shown in FIG. 1, with the high pressure supply in service, when the electronic control system 22, 24, 26, 30 issues an opening order of the valve, the finger 64 of the solenoid 20 pushes the ball 62 which closes the high pressure inlet 48 and places the line 58 in communication with the low pressure lines 54, 44.

The chamber 60 of the pilot cylinder 76 of the distributor is thus brought to low pressure and the drawer 70 is unbalanced, that is to say it is pushed to the left by the high pressure exerted permanently on its end. 78. As seen above, the opening order is an order to put the pilot cylinder 76 at low pressure, an order whose response is faster, at the high pressures used, than an order to increase in pressure. . In this "working" position of the drawer, the openings 74 ₂ , 74 ₃ of the drawer 70 put the orifice 66 of the dispenser into communication with the high pressure inlet 32 and isolate this orifice 66 from the low pressure outlet 44. The high pressure oil is thus introduced into the working chamber 68 of the power cylinder. The high pressure oil being on either side of the piston 90, in the chambers 68 and 93, it is the difference in section which creates the displacement of the assembly 90, 92, 10 and the force to be communicated to the valve 14 to open it, against the force of the valve spring 18.

When the order to close the valve is given, the electrical signal ceases and the solenoid 20 is no longer energized. Under the action of the high pressure pressure, the ball 62 closes the return 54, 44 at the low pressure and again admits this high pressure in the chamber 60 dtr distributor. The drawer 70 is again unbalanced and moves to the right until the position of FIG. 1 for which the working chamber 68 of the power cylinder is put in communication with the bass pressure. The chamber 93 is still under pressure, the piston 90 rises and returns to its rest position in which the valve is closed.

The frequency of opening of the valves being relatively high (for example 20 to 30 Hz), one of the difficulties, for the proper functioning of a control unit according to the invention, consists in maintaining the integrity of the lines. and their correct filling, without oil emulsion or cavitation. The presence of the accumulator 38 in the high pressure supply circuit promotes control of the hydraulic lines, but it is also advantageous to provide for the maintenance of a residual pressure in the low pressure circuit. For this, a tared retaining valve 98 (for example tared for 3 to 10 bars) is mounted on the low pressure outlet orifice 44, this valve preferably being incorporated in the distributor body 34.

Beyond the check valve 98, the purge oil from the pilot cylinder 76, 60 and from the power cylinder returns to a tank 100 at atmospheric pressure which can advantageously be formed, when the engine oil is used. even in the hydraulic circuit of the control unit, by the cylinder head, so as to grease the mechanical connection assemblies (ball joints, rocker arms, etc.) between the pusher 10 and the valves. In this case, it is preferable to provide the low-pressure oil outlet 44 at the bottom of the control unit and opening directly inside the cylinder head cover 8, which avoids having the cylinder head cover pass through. oil lines.

It should also be noted that the three main organs of the block being attached to each other, as shown in Figure 1, or having bodies common, there is no long link pipe that could cause delays in response to the opening or closing of the valves.

The control unit according to the invention makes it possible to obtain opening and closing speeds of the valves which would be mechanically impracticable, the mechanical system being limited by the accelerations linked to the profiles of the cams.

Since the displacement speeds of the piston 90 of the power cylinder are very high, hydraulic damping systems are provided for the end positions of the cylinder, by oil rolling, an embodiment of which is shown in FIG. 2.

This figure is a partial sectional view of the central part of Figure 1. The piston 90 of the power cylinder 6 has, at its upper part, a projecting collar 102 which penetrates, with reduced clearance, into a bore 104 delimiting the working chamber 68 of the power cylinder, at the upper end of stroke of the piston 90. One or more slots 106 are provided in the flange 102 to produce a rolling of the oil discharged by the piston 90 when the latter rises to 'to its rest end position.

Below the piston 90, on the rod 92, a conical portion 108 is provided which, at the end of the low stroke of the piston 90, enters a damping ring 110. The internal bore 112 of this ring determines, with the conical portion 108, an annular slot with variable section for the rolling of the oil at the bottom end of the piston stroke. It should be noted that, in this ring 110 are pierced the passages 96 (see FIG. 1) for supplying high pressure oil to the lower chamber 93 of the power cylinder 6.

Thanks to these damping systems, it is possible to apply a high opening and closing speed to the valves, without shock to the end-of-travel components. This also makes it possible to carry out brief intermediate reopening of the exhaust valves at certain speeds to reduce the thermal load on the valves or to heat the intake air.

FIG. 1 shows the control of a single valve by means of the control unit according to the invention. However, it is also possible, as shown diagrammatically in FIG. 3, to control two intake valves 14, 14 ′ (or exhaust) by means of a single block whose pusher 10 of the power cylinder 6 acts in pushing on a spreader 112 whose ends bear on the rods 12, 12 'of the valves 14, 14'. Of course, mechanical connections are provided by ball joints, similar to those of rocker arms or rocker rods, to avoid parasitic effects due to misalignments.

It should be noted that the control unit according to the invention provides great security because, in the event of an operating anomaly (lack of hydraulic pressure, lack of electrical signal on the electro-valve), the unit always returns to the rest position shown in Figure 1, with the corresponding valve or valves in the closed position, which avoids any risk of valve / piston impact towards top dead center.

As indicated, the control unit is very compact, which allows the accommodation of two assemblies (intake and exhaust) in an existing engine cylinder head. In addition, the assembly constituted by the solenoid valve 2 and the distributor 4 can be standard regardless of the type of engine, which reduces cost prices. The power cylinder 6 can also include a majority of standard components, the cylinder being simply adapted to the forces required by such or such type of motor by modification of its differential section, which allows adaptation to any existing motor.

The invention makes it possible to obtain durations and instants of opening of the variable valves according to the most favorable valve lift law as a function of the various operating parameters of the engine (speed, power, etc.), which was impossible with cam operated valves. It is even possible, with a suitable program, to operate on a reduced number of cylinders at low load (without losses by transfer) and, also, a simple and immediate reversibility of the engine.

Claims (3)

1. Electro-hydraulic valve control unit for an internal combustion engine provided with an electronic control system providing an electrical signal for opening the valve, which comprises: a three-way electro-valve (2), supply / purge, receiving said electrical signal; a three-way hydraulic distributor (4), supply / purge, the switching slide (70) of which is actuated by a hydraulic pilot cylinder (60, 76) connected to said solenoid valve, said slide (70) having one end ( 76) constituting the piston of the aforementioned pilot hydraulic cylinder; said distributor comprising a first orifice (32) connected to a high pressure source (36, 38), a second orifice (44) connected to a low pressure enclosure (100) and a third use orifice (66); a hydraulic power cylinder (6), the working chamber (68) of which is connected to the third orifice (66) of the distributor; return means (93) of the piston (90) of said cylinder in the rest position; means for pushing connection (10) of the rod (92) of said cylinder with the rod (12) of the valve (14) to be controlled; the three members: solenoid valve (2), hydraulic distributor (4) and power cylinder (6) being joined in a single block mounted on a member (8) of the engine secured to the cylinder head (16) of the engine; said block being characterized: in that, in the absence of the electrical signal for opening the valve, the electro-valve 2 is in the supply position and subjects the piston 76 of the pilot hydraulic cylinder to high pressure, while that, when excited by said electrical signal, said solenoid valve comes to the purge position and establishes low pressure on said piston 76; and in that the other end 78 of the drawer 70 is always subjected to the high. pressure, whereby the slide 70 comes into the power cylinder 6 supply position, in response to said electrical signal, under the effect of a pressure drop on the piston 76. 2. Block according to claim 1, characterized in that the power cylinder (6) is a differential cylinder, the chamber (93), opposite the working chamber (68), is permanently connected by pipes (96, 94, 32) to the same high pressure supply circuit (38, 36) which supplies the working chamber (68) for opening the valve. 3. Block according to claim 2, characterized in that the high pressure supply circuit (36, 38) uses the lubricating oil of the crankcase (40) of the engine; in that an oil filter (42) is interposed in the high pressure supply circuit (40, 36, 38), and in that the orifice 44 for return of purge oil is connected to bring the purge oil on the cylinder head.

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