US3727595A

US3727595A - Control device for hydraulically operated tappet valves of internal combustion engines

Info

Publication number: US3727595A
Application number: US00068362A
Authority: US
Inventors: H Links
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1969-08-30
Filing date: 1970-08-31
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17
Also published as: NL7012856A; GB1294217A; PL75950B1; BE755478A; RO60817A; FR2059174A5; CH503892A

Abstract

In an internal combustion engine, each intake and exhaust valve is operated by an actuating piston, which, in turn, is reciprocated by hydraulic liquid admitted under pressure to, and withdrawn from said piston intermittently by means of a solenoid valve.

Description

United States Patent 1191 1111 3,727,595 Links 145] Apr. 17, 1973 1 CONTROL DEVICE FOR [58] Field of Search ..123/90.1 1, 90.12, HYDRAULICALLY OPERATED 123/9015 TAPPET VALVES OF INTERNAL V COMBUSTION ENGINES 1561 References CM [75] Inventor: Heinz Links,Stuttgart.Germany UMTED STATES PATENTS 73 I 3,220,392 11 1965 Cummins ..123/90.12 X l I lgnce 2?" Swmart 3,548,793 12/1970 Richardson", 123/90.11 x ermmy 2,392,207 1/1946 Weiss 6181 ..123/90.11 x 22] Fi Aug 3 7 3,209,737 10/1965 Omotehara et a1 .1.. ]23/9()112 [21 1 APPL NQ-I 68,362 Primary Examiner-Al Lawrence Smith I Att0rneyEdwin E. Greigg 30 Forei A li t Pri D l 1 pp 57 ABSTRACT 'A .30, 1969 G 13:57 16, 1969 2; :3 2: 912. 1 an i P gz engme F i Feb, 12, 1970 Germany ..P 20 06 304.1 aust V f y an F b 14 970 G 4 1n turn, 15 recxprocated by hydrauhc 11qu1d admltted e ermdny ..P 20 06 844.4

I under pressure to, and wlthdrawn from sa1d plston 1n- Feb. 25, 1970 Germany ..P 20 08 668.4 eminent! b means of a Solenoid valve Mar. 5, 1970 Gcrma n'yum'. ..P 20 10 291.4 y y 1 1 Claim, 16 Drawing Figures [52] U.S. Cl ..123/90.12, 123/90.l5 [51] Int. Cl ..F0ll 9/02' PATENTEU 1 71973 SHEET 02 HF 10 PATENTEB APR 1 71973 SHEET 05 0F 10 III 5 3 PATENTEB APR 1 71973 SHEET 08 0F 10 PATENTEDAPRWW 3,727,595

SHEET 070F10 39d Fig. 12

PATENTED 1 71973 3.727. 595

sum 08 0F 10 d KW PATENTEB APR] 71973 SHEE (29 OF 10 com 00m v 00 m q mt mp mt m wb Q 2 2 9 C L, r

SHEET 10 [1F 10 PATENTEB APR 1 H973 CONTROL DEVICE FOR HYDRAULICALLY OPERATED TAPPET VALVES OF INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION valve in a closed position.

In a known control device for tappet valves according to the aforenoted type (such as described in Swiss Pat. No. 245,788),'the liquid is intermittently pressurized by means'of a cam-driven piston. The metering of the pressurized liquid is effected by a separately driven control member. According to anotherknown valve control device of the aforenoted type (such as described in German Pat. No. 858,329), again, the liquid is pressurized by a cam-driven pump piston. In the pressure conduit there is disposed a check valve, while for permitting a closing motion of the engine valve, a return conduit controlled by the pump piston, is connected with a chamber of lower pressure.

In control devices of the aforenoted type; the elasticity of the fluid in the system is a determining factor for the limits of possible applications. Due to the relatively long fluid conduits, a large fluid volume is present which, dependent upon the rpm and thus the throttle effect, causes a shift in the motion pattern between the pump piston and the engine valve. Such an occurrence results in an interference with the predetermined closing and opening moments of the valve. Furthermore, temperature variations also have an adverse effect, since they cause changes in the volume of the control liquid. Also, due to the elasticity of the fluid conduits, pressure oscillations may occur which may cause natural resonances of the valves thus resulting in an interruption of the connection between pump piston and cam or valve stem and actuating piston. The harmful result of such an occurrence is that the closing mo tion of the valves may not be controlled, a factor which may also lead to valve leakage. In addition to the aforenoted disadvantages, more or less for each type of engine a particular structure of cam, pump, piston, etc. is required, so that an overall standardization and mass production with the inherent beneficial savings in the manufacture of the entire control system for the intake and exhaust valves has heretofore not been possible.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved device for the control of hydraulically operated Accordingly, the tappet valve stem is in engagement with an actuating piston which is intermittently displaced by the liquid delivered under pressure to the control device by a delivery pump in a continuous manner. Contact between the actuating piston and the pressurized liquid in the control device is intermittently established by a periodically energized solenoid valve. The latter includes a movable valve member which, dependent upon the energized or the de-energized condition of the valve solenoid, may assume two positions. In one position it admits the pressurized liquid to said actuating piston, while in the other position it causes withdrawal of said liquid therefrom. When communication between the actuating piston and the continuously delivered pressurized liquid exists, the actuating piston, urged by the pressurized liquid, executes its working stroke whereby the tappet valve is opened.

The invention will be better understood, as well as further objects and advantages of the invention will become more apparent, from the ensuing detailed specification of several exemplary embodiments taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial sectional view of an embodiment of the invention including a schematic representation of g the associated liquid circuit;

FIG. 2 is an axial sectional view of a further embodiment of the invention;

FIG. 3 is a valve lift diagram pertaining to the operation of the embodiments according to FIGS. 1 or 2;

FIG. 4 is a sectional view of another embodiment of the invention including a schematic representation of an associated liquid circuit;

FIG. 5 is a fragmentary sectional view of the same embodiment showing some components in an alternate position;

FIG. 6 is a sectional view of still another embodiment of the invention including a schematic representation of an associated liquid circuit; 7

FIG. 7 is a fragmentary sectional view of the same embodiment showing some components in an alternate position;

FIG. 8 is a sectional view of a further embodiment of the invention including a schematic representation of an associated liquid circuit;

FIG. 9 is a fragmentary sectional view of the same embodiment showing some components in an alternate position;

FIG. 10 is a sectional view of a further embodiment of the invention including a schematic representation of an associated, electronically controlled liquid cir- 'cuit;

FIG. 10a is a block diagram of an electronic control apparatus associated with the embodiment shown in FIG. 10;

FIG. 11 is a diagram of valve lift curves illustrating the operation of the embodiment according to FIG. 10;

FIG. 11 is a sectional view of another embodiment of the invention including schematic representations of associated fluid circuits; 7 l

FIG. 13 is a diagram of valve lift curves illustrating the operation of the embodiment according to FIG. 12; FIG. 14 is a sectional view of still another embodiment of the invention including a diagrammatic representation of associated liquid circuits; and

FIG. 15 is a diagram of valve lift curves illustrating the operation of the embodiment according to FIG. 14.

DESCRIPTION OF THE EMBODIMENT SHOWN IN FIG. 1

FIG. 1 illustrates the invention in its simplest form. In

a partially shown cylinder head 1 of an internal combustion engine there operates a tappet valve 2 having a valve stem 3 axially slidably guided by a bearing sleeve 4 secured in the wall of the cylinder head 1. The outer end of the valve stem 3 carries a spring seat disc 5. Between the upper face of the cylinder head 1 and the spring seat disc 5 there is disposed in a preloaded condition a valve closing spring 6. To the cylinder head 1 there is secured a housing bracket 7 containing a solenoid valve generally indicated at 8 and an actuating piston 9. The latter is axially displaceably guided in a fluid-tight manner in a bushing 10 threadedly secured to the bracket 7. During the valve movement, the lower terminal face of the actuating piston 9 is urged into contact with the valve stem 3. The actuating piston 9 projects 'into a chamber 11 which is provided in the bushing 10 and which receives a spring 12 urging the actuating piston 9 in the closing direction of the tappet valve 2.

A delivery pump 14 draws liquid from a tank 13 and 1 delivers it under a pressure of, for example 100 kg/cm through a pressure conduit 15 towards the solenoid valve 8. From the conduit 15 there extends, downstream of the pump 14, a return conduit 16 in which there is disposed a pressure control valve 17 and which terminates in the tank 13.

In the housing bracket 7 supporting the solenoid valve 8, the liquid first flows into a pressure chamber 19 which is connected with a control chamber 21 by means of a bore 20 serving as a supply channel. The mouth of the bore 20 at the control chamber 21 serves as a valve seat for a sphere 22 which is movably disposed in the control chamber 21. From the control chamber 21 there extends a bore 23 to the chamber 11. From the control chamber 21 there also extends a bore 24 which is in continuous communication with the tank 13 through a discharge channel 25 and a return conduit 26. The 'mouth of the bore 24 at the control chamber 21 serves as a valve seat for the valve sphere 22. An armature 28, having a pin-like extension 28' in contact with the sphere 22, is slidably disposed in the bore 24 and urges, under the action of a spring 27, the sphere 22 into a position in which it closes the bore 20.

The control chamber 21, the bore 24 and the armature 28 are contained in a valve support sleeve 29 which is inserted in the housing bracket 7 and which is held in position by a flange of the housing 30 of the electromagnet forming part of the solenoid 8. The electromagnet chamber accommodating the spring 27 and the bore 20 immediately upstream of the solenoid valve, are interconnected by means of a channel 31 so that in both I aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 28 sliding in the bore 24 in a fluid-tight manner, -is identical to the diameter of both seats for the sphere 22. Thus, as long as the sphere 22 is in a position shown in FIG. 1, the force derived from the pressure prevailing in bore 20 and exerted on the sphere in the opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 28 in the closing direction. Spring 27 aids the latter force so that the sphere 22 is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 20.

As soon as the coil 33 of the electromagnet is energized, for example, by an electronic control device, the force of the spring 27 is overcome by the magnetic force and the armature 28 is displaced towards the left. The pressurized liquid thus may flow through bore 20, pressing the sphere 22 against its other, opposite seat formed about the opening of bore 24. As a result,

sphere 22 closes the bore 24 so that the liquid admitted under pressure through the bore 23 may flow into the chamber 11, after displacing the actuating piston 9. This results in the opening of the tappet valve 2.

' As soon as the solenoid 33 is deenergized, the spring 27 returns the armature 28 and the sphere 22 into their initial position in which the bore 20 is again closed. As the bore 24 is opened by the returning sphere 22, the liquid may flow from the chamber 11 through the bore 24, the channel 25 and the return conduit 26 to the liquid tank 13 allowing the actuating piston 9 to return. This, in turn, causes the tappet valve 2 to assume its closed position.

DESCRIPTION OF THE EMBODIMENT SHOWN IN FIG. 2

In the embodiment shown in FIG. 2, the admission of liquid to the actuating piston 9 is effected by a servooperated control means. This embodiment finds application particularly in large internal combustion engines, where greater forces are needed to open the engine valves. In this structure the hydraulic servo circuit is controlled by a solenoid valve of the type and in the manner as described in connection with the embodiment depicted in FIG. 1. The liquid admitted through the conduit 15 flows through a channel 37 into an annular groove 38 which is formed in the wall of a bore 39. From the annular groove 38 there extend the pressure chamber 19 and the bore 20. In the bore 39 there operates a control plunger 40 which is in engagement with an axially aligned piston 50.

Controlled by the solenoid valve 8 as described in i connection with FIG. 1, the pressurized liquid flows from bore 20 to control chamber 21, bore 23 and then through a channel 41 to a lower radial face of piston 50. Under the effect of this liquid pressure, the piston 50 and thus the control plunger 40 are displaced against the force of a spring 42 disposed in bore 39. In the cylindrical face of the control plunger 40 there is provided a circumferential annular groove 43 which is in continuous communication with the annular groove 38. The portion of the bore 39 accommodating the spring 42 is'connected through a channel 44 with the return conduit 26 terminating in the liquid tank 13.

In the bore 39 there is formed an annular groove 45 which is in communication through a channel 46 with one side of a bore 47 in which there is reciprocably arranged an actuating piston 48. In the control plunger 40 there are provided radial bores 49 which, in the position of the control plunger 40 as shown in FIG. 2, connect the bore 47 with the discharge channel 44.

As soon as the solenoid of the electromagnet is energized, the pressurized liquid displaces the piston 50 and the control plunger 40 against the force of the return spring 42 whereby the annular groove 43 shifts into alignment with the annular groove 45 while, at the same time, the bores 49 hydraulically separate from the annular groove 45. In this manner the liquid present under pressure in the annular groove 38 may flow through the annular grooves 43 and 45 to the radial face of the actuating piston 48 and thereby effect an opening of the tappet valve.

As soon as the solenoid of the electromagnet is deenergized, the control plunger 40 is returned by the spring 42 into its initial position in which the annular grooves 45 and 43 are separated from one another, whereas the radial bores 49 are re-connected with the annulargroove 45. Upon this occurrence, the pressurized liquid present above the actuating piston 48 may flow from the bore 47 through the annular groove 45 to the liquid tank 13. As a result, the tappet valve closes.

In the afore-described embodiments the

work pistons

9 and 48 affect directly the stem 3 of the tappet valve 2. It is to be understood that between piston and valve stem there may be provided any other force transmitting means, such as a rocker arm, or the like.

EXAMINATION OF VALVE LIFT CURVES OBTAINABLE BY THE EMBODIMENTS ACCORDING TO FIGS. 1 AND 2 The diagram shown in FIG. 3 particularly well illustrates the advantages of the afore-described embodiments. In the diagram the stroke s of the tappet valve is shown as a function. of the angular position of the cam shaft. The stroke s designates the structurally possible maximum stroke of the tappet valve. The valve lift curve I pertains to a tappet valve operated conventionally by the cam of a cam shaft. The relatively flat initial portion of the ascent and relatively flat terminal portion of the descent of the curve is caused by the fact that the flanks of a cam, for starting and terminating the force transmission to the push rod, must not be steep. A transition into a steeper range may occur only when the stroke is already under way. As a result, at the beginning and at the end of this valve lift curve there are points in which the velocity of the tappet valve is close to zero. The effective open period x flow passage section (hereinafter designated an open time area) is the areabelow the curve I.

The lift curves II, III and IV represent the stroke ofa tappet valve operated by means of a device according to the afore-described embodiments of the invention. These curves all have a relatively steep course since the switching time of the electromagnet is extremely short. Thus, the slope of these curves depends exclusively from. flow resistances and refill'periods. Since the open ing time of the solenoid valve always remains the same, whereas the aforenoted effects change with the rpm (i.e. with the available length of time), to each rpm there corresponds a different curve. Thus, curves II, III and IV correspond to three different rpms. In the stroke portions s s and s s the dampening becomes effective. At points s and s a substantial change of the curve slope begins. While at s towards the end of the opening stroke, the motion of the actuating piston is dampened, during the return motion thereof, i.e. during the closing motion of the tappet valve (on the right side of the diagram), the setting motion is damped from s;, on.

As it may be well observed from FIG. 3, the area under the curves II, III and IV is substantially larger than that under the curve 1, resulting in the advantages set forth earlier.

DESCRIPTION OF THE EMBODIMENT ACCORDING TO FIGS; 4 AND 5 Turning now to FIGS. 4 and 5, in a partially shown cylinder head la of an internal combustion engine there operates a tappet valve 2a having a valve stem 3a axially slidably guided by a bearing sleeve 4a secured in the wall of the cylinder head la. The outer end of the valve stem 3a carries a spring seat disc 5a. Between the upper face of the cylinder head 1a and the spring seat disc 5a there is disposed in a preloaded condition a valve closing spring 6a. To the cylinder head la there is secured a housing bracket 7a containing a solenoid valve generally indicated at 8a and an actuating piston 9a. The latter is axially displaceably guided in a fluidtight manner in a bushing 10a secured to the bracket 7a. During the valve movement, the lower terminal face of the actuating piston 9a is urged into contact with the valve stem 3a. The upper end of actuating piston 9a projects into a chamber 11a.

A delivery pump 14a draws liquid through a suction conduit 12a from a tank 13a and delivers it under a pressure of, for example kg/cm through a pressure conduit towards the solenoid valve 8a. From the conduit 15a there extends, downstream of -the pump 14a, a return conduit 16a in which there is disposed a pressure control valve 17a and which terminates in the tank 13a.

From conduit 151; there extend conduits 18a which lead to the control devices of the other engine valves and which carry liquid under pressure delivered by the same pump 14a.

In the bracket housing 7o supporting the solenoid valve 8a, the liquid first flows through a supply channel 19a which is connected with a control chamber 21a by means of a bore 20a serving also as a supply channel. The mouth of the bore 20a at the control chamber 21a serves as a valve seat for a sphere 22a which is movably disposed in the control chamber 21a. From the. control chamber 210 there extends a bore 230 to the chamber 110. From the control chamber 21a there also extends a bore 240 which is in continuous communication with the suction conduit 12a through

discharge channels

25a and 26a and a return conduit 26a. The mouth of the bore 24a at the control chamber 21a serves as a valve seat for the valve sphere 220. An armature 28a, having a pin-like extension 28a in contact with the sphere 22a, is slidably disposed in the bore 24a and urges, under the action of aspring 27a, the sphere 220 into a position in which it closes the bore 20a.

The control chamber 21a, the bore 24a and the ar mature 28a are contained in a valve support sleeve 29a which is inserted in the housing bracket 7a and which is held in position by a flange of the housing 30a. of the electromagnetic forming part of the solenoid 8a. The electromagnet chamber accommodating the spring 27a and the bore 200 immediately upstream of the solenoid valve, are interconnected by means of a channel 310 so that in both aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 28a sliding in the bore 24a in a fluidtight manner, is identical to the diameter of both seats for the sphere 22a. Thus, as long as the sphere 22a is in a position shown in FIG. 4, the force derived from the pressure prevailing in bore 20a and exerted on the sphere in' the opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 28a in the closing direction. Spring 27a aids the latter force so that the sphere 22a is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 20a.

As soon as the coil 33a of the electromagnet is energized, for example, by an electronic control device, the force of the spring 27a is overcome by the magnetic force and the armature 28a is displaced towards the left. The pressurized liquid thus may flow through bore 20a, pressing the sphere 22a against its other, opposite seat formed about the opening of bore 24a. As a result, sphere 22a closes the bore 24a so that the liquid ad mitted under pressure through the bore 23a may flow into the chamber 11a, displacing the actuating piston 9a. This results in the opening of the tappet valve 2a.

As soon as the solenoid 33a is de-energized, the spring 27a returns the armature 28a and the sphere 22a into their initial position in which the bore 20a is again closed. As the bore 24a is opened by the returning sphere 22a, the liquid may flow from the chamber 11a through the bore 24a, the

channels

25a and 26a and the return conduit 26a to the suction side of pump 14a allowing the actuating piston 9a to return. This, in turn, causes the tappet valve 2a to assume its closed position.

In the suction conduit 12a upstream of the return conduit 26'a there is disposed a check valve 36a, so that the returning liquid generates a pressure build-up at the suction side of the pump 14a resulting in an improved efficiency and power thereof.

In the embodiment shown. in FIGS. 4 and 5, the motion of the actuating piston 9a is hydraulically braked towards the end of each stroke. For this purpose, on the lateral surface of the actuating piston 9a there is provided a collar 34a which, towards the end of the strokes of actuating piston 9a penetrates into one or the other cavity 35a, 35'a which have approximately the same diameter as the collar 340. As soon as the latter penetrates into one of the cavities 35a, 35'a, it displaces the liquid present in that cavity through a radial throttle gap which is defined by the wall of the cavity and the periphery of collar 34a. In this manner a dampening of the motion of work piston 9a is achieved. To obtain a gradual dampening effect, the walls of cavities 35a and 35 'a, as well as collar 34a, may have a conical configuration.

In order to ensure that the solenoid valve operates with the required switching speed at high engine rpms, the stroke of the armature 28a, as well as the traveling path of the sphere 22a, is very small. Accordingly, the

flow passage sections of the solenoid valve are also small. In larger engines this would result in an excessive throttle effect. To avoid such a disadvantage, according to this embodiment, the return and supply conduits circumvent the solenoid valve and, controlled by a plunger 37a, lead directly to the chamber 11a. The

plunger 37a has a circumferential annular groove 38a I which is in continuous communication with the supply channel 190 and an annular circumferential groove 39a which, in turn, is in continuous communication with the return channel 26a. Depending upon the position of the plunger 37a, one of the circumferential annular grooves 38a or 390 communicates with a channel 40a which, in turn, when the tappet valve 2a is in an open position, communicates with the chamber 11a. The connection between channel 40a and chamber 11a is controlled by the actuating piston 9a. Only after the latter has traveled a predetermined path, does the channel 40a open. For an axial pressure relief of the piston 9a, the latter has, in the range of the mouth of channel 40a, a circumferential annular groove 41a.

When the solenoid valve 8a opens the channel 200 and the actuating piston 9a, urged by the force of the inflowing liquid, has traveled a predetermined path, communication is established between the channel 400 and chamber 11a. Upon this occurrence, liquid may flow in an unthrottled manner into the chamber Ila from channel 40a and the actuating piston may be displaced rapidly. As soon as the solenoid valve 8a is switched (i.e. de-energized), the liquid, driven partly by the returning piston 9a and partly by the pump 14a through the channel 40a, flows through the bore 24a into the channel 25a and therefrom to the suction side of pump 14a. In the channel 25a there is disposed a throttle 43a which causes a build-up of the liquid upstream thereof.

The control plunger 37a operates in a bore 44a which is connected through a channel 45a with the channel 25a upstream of the throttle 43a. As soon as said liquid buildup occurs in the channel 25a, by virtue of the throttle 43a, liquid flows under pressure through channel 45a into the bore 44a and displaces the control plunger 37a against the force of a spring 46a until said plunger abuts against a shoulder 47a of the bore 44a (FIG. 5). Upon the aforenoted travel of the control plunger 37a, the supply channel 19a is separated from the channel 40a, whereas through groove 39a, the return channel 26a is connected with the channel 40a. As a result, the liquid may flow in an unthrottled manner from the chamber 11a through the bore 40a, the annular groove 39a, the return channel 26a and the return conduit 26a to the suction side of the pump 14a.

Shortly before the tappet valve 2a closes, the actuating piston 9a shuts off the channel 40a. During the entire period of the return motion of actuating piston 9a, effected by the valve spring 6a, in the channel 25a, there prevails a pressure (caused by the throttle 43a) which is sufficient to maintain the control plunger 37a in its terminal position shown in FIG. 5. As soon as the actuating piston 90, however, returns into its initial position, the liquid pressure in the channel 25a decreases, so that the spring 46a may return the control plunger 37a into its initial position in which, as shown in FIG. 4, the supply channel 19a is in communication with the channel 40a.

DESCRIPTION OF THE EMBODIMENT SHOWN IN FIGS. 6 AND 7 Turning now to FIGS. 6 and 7, the embodiment no play or clearance between the valve stem 3a and the actuating piston 9a.

For the aforenoted hydraulic operation, the control plunger 37a is provided with a further annular circumferential groove 49a which, by means of radial bores a and an axial bore 51a, is connected with the annular circumferential groove 39a. For the hydraulic actuation of the piston 9a the latter is provided with a collar 52a which is slidable in a fluidtight manner in a bore 530. From one end of the bore 53a there extends a channel 48a which, dependent upon the position of the plunger 37a, connects said end of bore 53a either with groove 49a (FIG. 6) or with groove 38a (FIG. 7) of the plunger 37a. The other end of the bore 53b is in continuous communication with the annular circumferential groove 390 through a channel 540. Instead of a throttle 43a in the channel25a, there is provided, in this embodiment, in the return conduit 26'a, a check valve 56a the opening pressure of which is designed in such a manner that in the entire return channel system a sufficiently high pressure is generated and maintained. As shown in FIG. 7, as soon as the control plunger 37a is displaced into its extreme position, the supply channel 19a is in hydraulic communication with the channel 48a through the annular circumferential groove 38a, so that the radial face of the collar 52a of the piston 90 is exposed to a pressure in the closing DESCRIPTION OF THE EMBODIMENT SHOWN IN FIGS. 8 AND 9 Turning now to the embodiment shown in FIGS. 8 and 9, in a partially shown cylinder head lb of an inter nal combustion engine there operates a tappet valve 2b having a valve stem 3b axially slidably guided by a bearing sleeve 4b secured in the wall of the cylinder head lb. The outer end of the valve stem 3b carries a spring seat disc 5b. Between the upper face of the cylinder head lb and the spring seat disc 5b there is disposed in a preloaded condition a valve closing spring 6b. To the cylinder head 1b there is secured a housing bracket 7b containing a solenoid valve generally indicated at 8b and an actuating piston 9b. The latter is axially displaceably guided in a fluid-tight manner in a bushing 10b secured to the bracket 7b. During the valve movement, the lower terminal face of the actuating piston 9b is urged into contact with the valve stem 3b. The upper end of actuating piston 9b projects into a chamber 11b.

A delivery pump 14b draws liquid from a tank 13b and delivers it under a pressure of, for example 100 kg/cm, through a pressure conduit 15b towards the solenoid valve 8b. From the conduit 15b there extends,

downstreamjof the pump 14b, a return conduit 16b in which thereis disposed a pressure control valve 17b and which terminates in the tank 13b.

From conduit 15b there extend conduits 18b which lead to the control devices of the other engine valves and which carry liquid under pressure delivered by the same pump 14b.

In the bracket housing 7b supporting the solenoid valve 8b, the liquid first flows into a bore 20b which is connected with a control chamber 21b. The mouth of the bore 20b at the control chamber 21b serves as a 10 valve seat for a sphere 22b which is movably disposed in the control chamber 21b. From the control chamber 21b there extends a bore 23b to the chamber 1 1b. From the control chamber 21b there also extends a bore 24b which is in continuous communication with the tank 13b through a discharge channel 25b and a return conduit 26b. The mouth of the bore 24b at the control chamber 21b serves as a valve seat for the valve sphere 22b. An armature 28b, having a pin-like extension 28'b in contact with the sphere 22b, is slidably disposed in the bore 24b and urges, under the action of a spring 27b, the sphere 22b into a position. in which it closes the bore 20b.

The control chamber 21b, the bore 24b and the armature 28b are contained in a valve support sleeve 29b which is inserted in the housing bracket 7b and which is held in position by a flange of the housing 30b of the electromagnet forming part of the solenoid 8b. The electromagnet chamber accommodating the spring 27b and the bore 20b immediately upstream of the solenoid valve, are interconnected by means of a channel 31b so that in both aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 28b sliding in the bore 24b in a fluidtight manner, is identical to the diameter of both seats for the sphere 22b. Thus, as long as the sphere 22b is in a position shown in FIG. 8, the force derived from the pressure prevailing in bore 20b and exerted on the sphere in the opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 28b in the closing direction. Spring 27b aids the latter force so that the sphere 22b is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 20b.

As soon as the coil 33b of the electromagnet is energized, for example, by an electronic control'device, the force of the spring 27b is overcome by the magnetic force and the armature 28b is displaced towards the left. The pressurized liquid thus may flow through bore 20b, pressing the sphere 22b against its other, opposite seat formed about the opening of bore 24b. As a result, sphere 22b closes the bore 24b so that the liquid admitted under pressure through the bore 23b may flow into the chamber 11b, displacing the actuating piston 9b. This results in the opening of the tappet valve 2b.

As soon as the solenoid 33b is de-energized, the spring 27b returns the armature 28b and the sphere 22b into their initial position in which the bore 20b is again closed. As the bore 24b is opened by the returning sphere 22b, the liquid may flow from the chamber 11b through the bore 24b, the channel 25b and the return conduit 26b to the liquid tank 13b allowing the actuating piston 9b to return. This, in turn, causes the tappet valve 2b to assume its closed position.

The aforenoted return motion of actuating piston 9b is, similarly to the third embodiment hydraulically braked towards the end of its stroke. Thus, for this purpose, the lateral face of the work piston 9b is provided with a collar 34b which, at the end of each return stroke of piston 9b, penetrates into a cavity 35b which has a diameter approximately identical to that of the collar 34b. From the cavity 35b the piston 9b displaces the liquid through a radial throttle gap formed between the wall of the cavity 35b and the periphery of the collar 34b. During the opening stroke of the tappet valve 2b, the collar 34b opens a bore 36b through which lubricating oil may flow from a lubricating system (not shown) into the cavity 35b. When subsequently, as shown in FIG. 9, the collar 34b emerges from the cavity 35b, the lubricating oil may flow into the spring chamber of the tappet valve 217.

The throttle gap defined between the collar 34b and the cavity 35b narrows towards the end of the return stroke in such a manner that a predetermined minimum volume remains locked between the collar 34b and the cavity 35b. Said minimum volume, by means of its elasticity, functions as an equalizer of clearance between the actuating piston 9b and the valve stem 3b. Such an equalization is advantageous since the dimensions of the valve stem 3b and the piston 9b vary as the temperature changes.

DESCRIPTION OF THE EMBODIMENT ACCORDING TO FIGS. AND 1 1 Turning now to the embodiment shown in FIGS. 10 and 11, similarly to the afore-described embodiments, in an only partially shown cylinder head 1c ofan internal combustion engine there operates a tappet valve 20 having a valve stem-3c axially slidably guided by a bearing sleeve 4c secured in the wall of the cylinder head 1c. The outer end of the valve stem 30 carries a spring seat disc 50. Between the upper face of the cylinder head 16 and the spring seat disc 5c there is disposed in a preloaded condition a valve closing spring 6c. To the cylinder head It there is secured a housing bracket 7c containing a solenoid valve generally indicated at 8c and an actuating piston 9c. The latter is axially displaceably guided in a fluid-tight manner in a bushing 100 secured to the bracket 7c. During the valve movement, the lower terminal'face of the actuating piston 96 is urged into contact with the valve stem 3c. The upper end of actuating piston 90 projects into a chamber 11c.

A delivery pump 14c draws liquid from a tank 13c and delivers it under a pressure of, for example 100 kg/cm through a pressure conduit 15c towardsthe solenoid valve 8c. From the conduit 15c there extends, downstream of the pump 140, a return conduit 160 in which there is disposed a pressure control valve 17c and which terminates in the tank 13c.

From conduit 150 there extend conduits 180 which lead to the control devices of the other engine valves and which carry liquid under pressure delivered by the same pump 140.

In the bracket housing 70 supporting the solenoid valve 80, the liquid first flows through a nipple 190 which is connected with a control chamber 210 by means of a bore 20c. The mouth of the bore 200 at the control chamber 21c serves as a valve seat for a sphere 22c which is movably disposed in the control chamber 210. From the control chamber 21c there extends a bore 230 to the chamber 11c. From the control chamber 210 there also extends a bore 240 which is in continuous communication with the tank 130 through a discharge channel 256 and a return conduit 260. The mouth of the bore 240 at the control chamber 21c serves as a valve seat for the valve sphere 220. An armature 28c, having a pin-like extension 28's in contact with the sphere 220, is slidably disposed in the bore 24c and urges, under the action of a spring 270, the sphere 22c into a position in which it closes the bore 20c.

The control chamber 21c, the bore 240 and the armature 28c are contained in a valve support sleeve 29c which is inserted in the housing bracket 70 and which is held in position by a flange of the housing 300 of the electromagnet forming part of the solenoid 8c. The electromagnet chamber accommodating the spring 270 and the bore 20c immediately upstream of the solenoid valve,are interconnected by means of a channel 31c so that in both aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 28c sliding in bore 24c in a fluid-tight manner, is identical to the diameter of both seats for the sphere 220. Thus, as long as the sphere 22c is in a position shown in FIG. 10, the force derived from the pressure prevailing in bore 200 and exerted on the sphere inthe opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 280 in the closing direction. Spring 27c aids the latter force so that the sphere 220 is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 200.

As soon as the coil 33c of the electromagnet is energized, for example, by an electronic control device, the force of the spring 27c is overcome by the magnetic force and the armature 28c is displaced towards the left. The pressurized liquid thus may flow through bore 20c, pressing the sphere 220 against its other, opposite seat formed about the opening of bore 24c. As a result, sphere 22c closes the bore 24c, so that the liquid admitted under pressure through the bore 23c may flow into the chamber 11c, displacing the actuating piston 9c. This results in the opening of the tappet valve 2c.

As soon as the solenoid 33c is de-energized, the spring 27creturns the armature 28c and the sphere 220 into their initial position in which the bore 200 is again closed. As the bore 240 is opened by the returning sphere 220, the liquid may flow from the chamber through the bore 240, the channel 250 and the return conduit 26c to the liquid tank allowing the actuating piston 90 to return. This, in turn, causes the tappet valve 2c to assume its closed position.

The motion of the actuating piston 90 may be hydraulically braked towards the end of each stroke. For this purpose, at the lateral cylindrical face of the actuating piston 90 there is provided a collar 340 which, towards the end of each stroke, penetrates into one or the other cavity 350, 35c, which have approximately the same diameter as the collar 340. As soon as the latter penetrates into one of the cavities 35c, 35's, it displaces the liquid present in that cavity through a radial throttle gap defined by the wall of the cavity and the periphery of the collar 340.

The power of the delivery pump is variable by means of a setting device 370 which may be formed of a hydraulic setting piston, but it may be an electric setting motor or any other similar device. The setting device 370 receives control signals from an electronic control apparatus 38c which converts data relating to actual conditions (particularly characteristics of the engine operation, such as the position of the accelerator 400 or the position of the brake pedal, as well as the pressure in the hydraulic system which is applied to apparatus 380 through a conduit 410) into a desired value for the power of the pump 140. This value is then applied to the setting apparatus 37c. The purpose of varying the power of pump 140 is to alter the pressure of the liquid that cause actuating piston 9c and thus valve 2c to execute its opening stroke. By varying said pressure, the amplitude of the opening stroke of the tappet valve 2c may be varied, because the equilibrium between the opposing forces of hydraulic pressure and valve spring 6c occurs at different positions of the tappet valve 2c as the hydraulic pressure is changed.

Turning to FIG. 10a, the electronic control apparatus 380 includes the regulator 38R and the converter 38F which is in the feed-back circuit to the regulator 38R. In the simplest case the regulator 38R is designed as an amplifier, the output volume of which controls the electromagnetically operating volume regulator of the pump 14c. So as to obtain the precise value as indicated by the accelerator 40c for the output pressure of the pump 140, the feed-back circuit 410 forms with the converter 38F a closed pressure regulating circuit. The converter 38F generates an electric signal from the pressure appearing at the output of the pump 140; the magnitude of said electric signal is comparable to the output volume or control value of the accelerator.

Independently from the afore-described control of 25 the hydraulic pressure in conduit 15c, the control apparatus 380 may also serve to energize and de-energize the solenoid valve SC for initiating the opening and closing of the tappet valve 2c and thus determine the timing of valve operation.

EXAMINATION OF VALVE LIFT CURVES OBTAINABLE BY THE EMBODIMENT ACCORDING TO FIG. 10

The diagram shown in FIG. 11 illustrates the ad vantage of the embodiment shown in FIG. 10. In this diagram the stroke s of the tappet valve 20 is shown as a function of the angle of rotation at of the engine cam shaft. The stroke s indicates the structurally possible largest stroke of the tappet valve. Thecurve I encloses an open time area obtained in case the valve 20 executes an opening stroke of maximum amplitude. When the power of the pump 14c is lowered, then the amplitude of the opening stroke drops to s The resulting valve lift curve II encloses a smaller open time area. By changing the opening or closing moments, as indicated by curve III, the open time area may be further altered.

DESCRIPTION OF THE EMBODIMENT ACCORDING TO FIG. 12

Turning now to the embodiment shown in FIG. 12, in a partially shown cylinder head 1d of an internal combustion engine there operates a tappet valve 2d having a valve stem 3d axially slidably guided by a bearing sleeve 4d secured in the wall of the cylinder head 1d. The outer end ofthe valve stem 3d carries a spring seat disc 5d. Between the upper face of the cylinder head Id and the spring seat disc 5d there is disposed in a preloaded condition a valve closing spring 6d. To the cylinder head 1d there is secured a housing bracket 7d containing a solenoid valve generally indicated at 8d and an actuating piston 9d.'The latter is axially displaceably guided in a fluid-tight manner in a bushing 10d secured to the bracket 7d. During the valve movement, the lower terminal face of the actuating piston 9d is urged into contact with the valve stem 3d. The upper end of actuating piston 9d projects into a chamber 1 1d.

A delivery pump 14d draws liquid from a tank 13d and delivers it under a pressure of, for example 100 kg/cm through a pressure conduit 15d towards the solenoid valve 8d. From the conduit 15d there extends, downstream of the pump 14d, a return conduit 16d in which there is disposed a pressure control valve 17d and which terminates in the tank 13d.

From conduit 15d there extend conduits 18d which lead to the control devices of the other engine valves and which carry liquid under pressure delivered by the same pump 14d.

In the bracket housing 7d supporting the solenoid valve 8d, the liquid first flows into a bore 20d which is connected with a control chamber 21d of the solenoid valve 8d. The mouth of the bore 20d at the control chamber 21d serves as a valve seat for a sphere 22d which is movably disposed in the control chamber 21d. From the control chamber 21d there extends a bore 23d to the chamber 1 1d. From the control chamber 21d there also extends a bore 24d which is in continuous communication with the tank 13d through a discharge channel 25d and a return conduit 26d. The mouth of the bore 240! at the control chamber 21d serves as a valve seat for the valve sphere 22d. An armature 28d, having a pin-like extension 28'd in contact with the sphere 22d, is slidably disposed in the bore 24d and urges, under the action of a spring 27d, the sphere 22d into a position in which it closes the bore 20d.

The control chamber 21d, the bore 24d and the armature 28d are contained in a valve support sleeve 29d which is inserted in the housing bracket 7d and which is held in position by a flange of the housing 30d of the electromagnet forming part of the solenoid 8d. The

electromagnet chamber accommodating the spring 27d and the bore 20d immediately upstream of the solenoid valve, are interconnected by means of a channel 31d so that in both aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 28d sliding in the bore 24d in a fluidtight manner, is identical to the diameter of both seats for the sphere 22d. Thus, as long as the sphere 22d is in a position shown in FIG. 12, the force derived from the pressure prevailing in bore 20d and exerted on the sphere in the opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 28d in the closing direction. Spring 27d aids the latter force so that the sphere 22d is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 20d.

As soon as the coil 32d of the electromagnet is energized by an electronic control device 33d, the force of the spring 27d is overcome by the magnetic force and the armature 28d is displaced towards the leftfThe pressurized liquid thus may flow through bore 20d, pressing the sphere 22d against its other, opposite seat formed about the opening of bore 24d. As a result, sphere 22d closes the bore 24d, so that the liquid admitted under pressure through the bore 23d may flow into the chamber 11d, displacing the actuating piston 9d. This results in the opening of the tappet valve 2d.

As soon as the solenoid 32d is de-energized, the spring 27d returns the armature 28a and the sphere 22d into their initial position in which the bore 20d is again closed. As the bore 24d is opened by the returning sphere 22d, the liquid may flow from the chamber 11d through the bore 24d, the channel 25d and the return conduit 26d to the liquid tank 13d allowing the actuating piston 9d to return. This, in turn, causes the tappet valve 2d to assume its closed position. The flow resistance of the channels ensures an operation free from play between the actuating piston 9d and the valve stem 3d.

The closing motion of the actuating piston 9d is, towards the end of each stroke, hydraulically braked. For this purpose on the lateral face of the piston 9d there is provided a collar 34d which, towards the end of each stroke, penetrates into one or the

other cavity

35d, 35d, which have approximately the same diameter as the collar 34d. From the

cavities

35d, 35d, the collar 34d displaces the liquid through an annular gap defined by the wall of the cavity and the periphery of the collar, resulting in a dampening of the piston stroke. The throttle gap has to be of such minimum dimension that even at high rpms, the tappet valve 2d closes entirely. a

By means of the electronic control apparatus 33d which is connected through a conductor 37d with the solenoid 32d of the electromagnet, the moment of opening and closing of the tappet valve 2d may be controlled independently from one another. The desired values of magnitude set by the electronic control apparatus 33d are determined from the evaluation of actual sensed data, particularly those relating to operational magnitudes of the e'ngine, such as the position of the accelerator (i.e. load), rpm, external pressure, engine temperature, etc. The signals relating to the sensed actual magnitudes are applied through conductors 38d .to the electronic control apparatus 33d. Such input signal may be derived, for example, from the position of an accelerator pedal 39d, sensed by a device 40d not shown in detail. Further, from the electronic control apparatus 33d, there extend conductors 41d to control devices (not shown) for the other engine valves. Such electronic control apparatus 33d as mentioned is described in the German Pat. No. 1,100,377 (Bendix).

EXAMINATION OF VALVE LIFT CURVES OBTAINABLE BY THE EMBODIMENT ACCORDING TO FIG; 12

The diagram shown in FIG. 13 illustrates the advantages of the embodiment shown in FIG. 12. In this diagram the stroke s (ordinate) of the tappet valve is illustrated as a function of the angular position a (abscissa) of the engine crankshaft (KW). The valve lift curves associated with an exhaust valve and an intake valve are shown side by side. In the example illustrated, the opening stroke is constant and is designated with s Further, the maximum open period of the exhaust valve constant opening and closing velocity of the tappet valves,these curves I have a relatively flat slope. In order to obtain at the intake valve a large open time area, for obtaining a maximum engine power, the two lift curves I overlap, that is, the intake valve begins to open before the exhaust valve is completely closed. In this example, the angle of overlap is the same.

The curves II represent a valve operation with minimum rpm under full load conditions. By virtue of the low rpm, the slope of the lift curves II for the opening and closing strokes, is substantially steeper than that of the lift curves I. It is seen that the duration of the opening stroke expressed in a is shorter here because i of the lower rpm. The result is a greater open time area.

Because of the aforenoted larger open time area, an overlap of the exhaust valve curve with the intake valve curve is not necessary. For the intake valve, this results in a rapid and optimal filling with air and at the exhaust valve there is a correspondingly rapid expansion and withdrawal of the combustion gases. Thus, for example, as it may be observed from the diagram, the opening moment of the exhaust valve may be the same under full load conditions for maximum rpm and minimum rpm, whereas the closing moment for maximum rpm occurs later (to cause overlap) than in case of minimum rpm. For the intake valve the converse ap plies.

The curves III correspond to the partial load range. Here, too, the moment of closing the exhaust valve and the moment of opening the intake valve may be shifted with respect to one another. Dependent upon the rpm, the positive or negative slop of the curve may vary. The valve operation may be altered, on the one'hand, as a function of the load and, on the other hand, as a function of the rpm. The said variations as a function of load and rpm are independent from one another, because one curve shift is effected as a function of the accelerator position, whereas the other is dependent upon the engine rpm. For the intake valve, this type of control has the significant advantage that the mean pressure or the torque substantially increases with decreasing rpm which results in a decrease of the fuel consumption in case of a continuous injection and further results in the decrease of the pollutants in the exhaust gases. Thus, a substantial improvement of the engine operation and particularly a quiet run in the idling range is achieved.

Curve IV pertains to an exhaust valve and encloses a relatively small area, so that beyond a determined rpm a braking effect appears. The opening or closing moment of the exhaust valve is varied as a function of the position of the brake pedal and the engine rpm. Thus, the open period of the exhaust valve is variable as a function of the brake pedal position; the open time area of the exhaust valve decreases as the brake pedal changes its position in the direction of increased braking effect. In this manner, the braking moment of the engine aids the mechanical braking by forcing the engine piston to perform increased work during its exhaust stroke. Preferably, during the actuation of the brake pedal, the fuel admission is shut off, so that only air is compressed and displaced.

The load-and-rpm-dependent change of the opening and closing moments of the intake and exhaust valves may contribute, in either Otto or diesel engines, to additional power increases. Thus, for example, as indicated by the inlet valve curve V, under full load con ditions at maximum rpm, the lift curve of the intake valve may much more substantially overlap the exhaust valve curve I than does the inlet valve curve I. Consequently, the open time area of the intake valve is increased. The portion corresponding to the opening course of the intake valve is, in curve V, as compared to curve I, shifted parallel in the direction of the exhaust valve curve. By virtue of this increase of the open time area, the so-called smoke limit is increased and, in diesel engines, the use of a compressor becomes unnecessary.

Advantages may be further achieved by shifting the beginning and the terminal moment of the valve opening with respect to the crankshaft angle as illustrated by curve VI. For the exhaust valve, this curve VI, which corresponds to the partial load range, appears duringthe braking of the engine by means of the exhaust valve.

The variable overlap or separation of the valve opening also has an effect on the course of combustion and thus, on the composition of exhaust gases. It is noted that the CO, CH and NO components appear mostly in the low to middle load and rpm ranges.

The CO content is reduced by means-of an overlap which decreases with the rpm, in that the residual gas quantities are decreased and a leaner mixture adaptation is possible. In addition, a miss-free operation may be achieved.

The CH content may be reduced in this range by a large overlap possibly coordinated with the injection periods. Particularly in case of delays when coasting in gear, the CH content may be substantially decreased by a decrease or elimination of the overlap. This valve control may be effective to such an extent that the heretofore necessary fuel shut-off device operative while coasting in gear, may be dispensed with. i

The NO content is lowered by reintroducing the exhaust gas into the intake suction system; the variable valve time overlap is insofar advantageous since the metering device and shut-off apparatus of an extem al exhaust reintroducing system may be omitted.

DESCRIPTION OFTHE EMBODIMENT ACCORDING TO FIG. 14

In a partially shown cylinder head 1d of an internal combustion engine there operates a tappet valve 2e having a valve stem 3e axially slidably guided by a bearing sleeve 42 secured in the wall of the cylinder head 12. The outer end of the valve stem 32 carries a spring seat disc 52. Between the upper face of the cylinder head 12 and the spring seat disc 52 there is disposed in a preloaded condition a valve closing'spring 62. To the cylinder head 12 there is secured a housing bracket 72 containing a solenoid valve generally indicated at 82 anda hydraulically operated actuating piston 9e. The latter is axially displaceably guided in a fluid'tight manner in a bushing 102 secured to the bracket 7e. During the valve movement, the lower terminal face of the actuating piston 9e is urged into contact with the valve stem 32. The upper end of actuating piston 92 projects into a chamber 112 which leads to solenoid valve 82. 7

A delivery pump 142 draws liquid from a tank 132 and delivers it under a pressure of, for example 100 kg/cm through a pressure conduit 152 towards the solenoid valve 82. From the conduit 152 there extends, downstream of the pump 142, a return conduit 162 in which there is disposed a pressure control valve 172 and which terminates in the tank 132.

From conduit 152 there extend conduits 182 which lead to the control devices of the other engine valves and which carry liquid under pressure delivered by the same pump 142.

In the bracket housing 72 supporting the solenoid valve 82, the liquid first flows into abore 202 which is connected with a control chamber 212. The mouth of the bore 202 at the control chamber 212 serves as a valve seat for a sphere 222 which is movably disposed in the control chamber 212. From the control chamber 212 there extends a bore 232 to the chamber 112. From the control chamber 212 there also extends a bore 242 which is in continuous communication with the tank 132 through a discharge channel 252 and a return conduit 262. The mouth of 'the bore 242 at the control chamber 212 serves as a valve seat for the valve sphere 222. An armature 28e, having a pin-like extension 282 in contact with the sphere 222, is slidably disposed in the bore 242 and urges, under the action of a spring 272, the sphere 222 into a position in which it closes the bore 202.

The control chamber 212, the bore 242 and the armature 282 are contained in a valve support sleeve 292 which is inserted in the housing bracket7e and which is held in position by a flange of the housing 302 of the electromagnet forming part of the solenoid 82. The electromagnet chamber accommodating the spring 272 and the bore 202 immediately upstream of the solenoid valve, are interconnected by means of a channel 312 so that in both aforenoted spaces identical pressures prevail. Further, the diameter of the cylindrical surface of armature 282 sliding in the bore 242 in a fluid-tight manner, is identical to the diameter of both seats for the sphere 222. Thus, as long as the sphere 222 is in a position shown in FIG. 14, the force derived from the pressure prevailing .in bore 202 and exerted on the sphere in the opening direction, is identical to the force of the pressurized liquid exerted on the sphere by the armature 282 in the closing direction. Spring 27e aids the latter'force so that the sphere 222 is, as a net result of the opposing forces, urged against the mouth or valve seat provided about the bore 202.

As soon as the coil 332 of the electromagnet is energized, for example, by an electronic control device, the force of the spring 272 is overcome by the magnetic force and the armature 282 is displaced towards the left. The pressurized liquid thus may flow through bore 202, pressing the sphere seat formed about the opening of bore 242. As a result, sphere 222 closes the bore 242, so that the liquid adinto the chamber 112, displacing the actuating piston 92. This results in the opening of the tappet valve 2e.

As soon as the solenoid 332 is de-energized, the

spring 272 returns the armature 282 and the sphere 222 into their initial position in which the bore 202 is again closed. As the bore 242 is opened by the returning sphere 222, the liquid may flow from the chamber 112 222 against its other, opposite

Claims

1. In a control device for hydraulically operated tappet valves of an internal combustion engine, said device being of the type that includes a reciprocating actuating piston mechanically connected to an associated tappet valve for periodically opening the latter against the force of a valve closing resilient means, the improvement comprising A. a source continuously supplying pressurized hydraulic liquid, B. first channel means connecting said source with said actuating piston for delivering pressurized hydraulic liquid to said actuating piston for exerting an opening force thereon, C. a hydraulic servo means having 1. a hydraulically operated valve situated in said first channel means and adapted to assume a first position in which it blocks delivery of said pressurized hydraulic liquid to said actuating piston and a second position for maintaining direct hydraulic communication between said source and said actuating piston for allowing delivery of said pressurized hydraulic liquid to said actuating piston, 2. means for urging said hydraulically operated valve into said first position, 3. second channel means connecting said source with said hydraulically operated valve for delivering pressurized hydraulic liquid to said hydraulically operated valve for exerting a force thereon to move it into said second position, said first channel means and said second channel means being connected in parallel between said source and said hydraulically operated valve, 4. a solenoid valve situated in said second channel means and adapted to assume a first position in which it blocks delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve and a second position in which it allows delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve, said first channel means fully circumventing said solenoid valve, 5. means for urging said solenoid valve into its first position and D. means for intermittently energizing said solenoid valve for moving it periodically into its second position.

2. means for urging said hydraulically operated valve into said first position,

3. second channel means connecting said source with said hydraulically operated valve for delivering pressurized hydraulic liquid to said hydraulically operated valve for exerting a force thereon to move it into said second position, said first channel means and said second channel means being connected in parallel between said source and said hydraulically operated valve,

4. a solenoid valve situated in said second channel means and adapted to assume a first position in which it blocks delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve and a second position in which it allows delivery of said last-named pressurized hydraulic liquid to said hydraulically operated valve, said first channel means fully circumventing said solenoid valve,

5. means for urging said solenoid valve into its first position and D. means for intermittently energizing said solenoid valve for moving it periodically into its second position.