GB2320522A

GB2320522A - Device for determining the opening and closing times of a valve, eg i.c. engin inlet valve or fuel-injection valve

Info

Publication number: GB2320522A
Application number: GB9726144A
Authority: GB
Inventors: Helmut Finger; Siegfried Sumser; Gerhard Schottke
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1996-12-18
Filing date: 1997-12-10
Publication date: 1998-06-24
Also published as: DE19652719A1; ITRM970775A1; IT1297116B1; FR2757242B1; FR2757242A1; GB9726144D0

Abstract

In a device for determining the opening and closing times of a valve 1, 2 which can be opened by lifting off a closure element 3 from a valve seat 4 and can be closed by bringing the closure element 3 into contact with it, the valve forms a contact switch in an electrical circuit. In this context, at least one electrical variable can be sensed by an evaluation unit 5, it being possible for the opening and closing times of the valve 1, 2 to be determined from said electrical variable. The valve may be an inlet valve 3, fig. 1, the stem 11 of which is received in a conductive guide sleeve 8 which is isolated from the cylinder head 14 by an insulating sleeve 9. An insulating cup tappet 6 is used. A contact 10 on the guide sleeve 8 and an earth contact 13 on the head 14 are connected to a low voltage source and the time profile of the voltage of the circuit is evaluated digitally by unit 5. In the case of a fuel-injection valve, fig.2, a circuit including earth contact 13 and contacts 10 and/or 13 is closed when the valve element 3 contacts the valve seat 4.

Description

1 Device for determining the gRening and closigg times of a valve 2320522

The invention relates to a device for determining the opening and closing times of a valve.

In most applications of valves which can be opened by lifting off a closure element from a valve seat and can be closed by bringing the closure element into contact with the seat, the determination of the opening and closing times, and thus of the control times, is of great significance. In doing so, the valve controls the flow of a fluid and the valve is thus a decisive factor in the control of working processes. External influences such as, for example, different component temperatures or the dynamics of the valve drive change the control times and control periods of the valve and give rise to a possibly adverse influence on the working process controlled by the valve. Usually, the valve setting is controlled on the basis of values gained through experience, it being impossible to sense deviations from the reference value which has been set and operational influences on the valve having unlimited effects on the valve play or the control times. In particular in the case of valves for the combustion gases of internal combustion engines, the actual valve play and the resulting control times influence a large number of operating parameters of the internal combustion engine such as power output, emission of pollutants and fuel consumption. In this context when the internal combustion engine is operating a valve controller sets the valve at every operating point using predetermined parameters. This variable valve control with adjustable control times is carried out on the basis of values gained from experience, which are determined before the internal combustion engine is put into service, for example on a test bench. The changes in the control periods and control times of the valve, which occur increasingly over the service life of the internal combustion engme and which have a damaging effect on the operating parameters of the internal combustion engine, are difficult to compensate at a later time and therefore have to be compensated at long maintenance intervals since, like the precise configuration of the valve drive, they can be carried out for the respective application only by control on the basis of values gained through experience.

The present invention seeks to provide a device for determining the actual opening and closing times of a valve which takes into account all the influences on the control times.

According to the present invention there is provided a device for determining the opening and closing times of a valve openable by lifting off a valve closure element from a valve seat and closable by bringing the closure element into contact with the seat, wherein the valve forms a contact switch in an electrical circuit, and at least one electrical variable is sensed by an evaluation unit.

The valve forms, with the closure element and the valve seat, a contact switch in an electrical circuit which can be completed when the valve is closed by bringing the closure element into contact with the valve seat. At least one electrical variable of the circuit can be sensed here by an evaluation unit which determines the opening or closing time of the circuit from the change in the electrical variable. The evaluation unit determines, in a direct dependence, the opening and closing times of the valve from the time profile of the electrical variable with sudden changes in the case of an opening or closing event of the electrical circuit.

A control variable, which can advantageously be fed to a controller unit, can be generated by the evaluation unit as a function of the electrical variables of the circuit. The controller unit can control all the methods or devices for which the precise knowledge of the actual opening and closing times of a valve is significant. It is of particular advantage here that the valve or the control periods and control times of the valve can be controlled by the controller unit, as a result of which optimum and variable setting of the valve is made possible under all operating conditions.

Further features of expedient refinements of the invention emerge from the subclaims and from the following description of an advantageous exemplary embodiment described with reference to the drawing, in which:

Fig. 1 shows a longitudinal portion of an inlet valve in the cylinder head of an internal combustion engine, Fig. 2 shows a longitudinal section of an injector of a fuel-injection internal combustion engine.

The inlet valve 1 (illustrated in Fig. 1) controls an inlet port 19 in the cylinder head 14 of an internal combustion engine. The inlet port 19 can be opened by lifting off a valve element 3 from a valve seat 4 in the final portion of the inlet port 19.

3 The valve seat 4 is formed here on the casing of the cylinder head 14. A valve stem 11 which bears a cup tappet 6 is formed on the valve element 3. By appropriately activating the cup tappet 6, the valve element 3 can be lifted off from the valve seat 4 in order to open the inlet port 19. In order to ensure that the closure element 3 bears against the valve seat 4 precisely when the valve 1 closes, the valve stem 11 is longitudinally guided in a guide sleeve 8.

In order to determine the precise opening and closing times of the valve 1, the closure element 3 and the valve seat 4 form a switch in an electrical circuit. Here, an electrical potential is applied to the closure element 3, while the valve seat 4 forms an earth contact 13 of the circuit via the casing of the cylinder head 14. The electrical voltage is applied via a contact 10 to the guide sleeve 8 which is composed of electrically conductive material. The guide sleeve 8 engages around the valve stem with a guide surface 21, the contact 10 interacting with the valve element 3 in an electrically conductive fashion. The guide sleeve 8 is received in an insulation sleeve 9 of electrically non- conductive material and is thus inserted into the casing of the cylinder head 14 in an electrically insulated fashion. Furthermore, in order to activate the valve element 3, the cup tappet 6 is composed of an electrically non-conductive material, so that the only contact between the valve element 3 and earth is possible as a result of said valve element 3 bearing against the valve seat 4. The contact 10 and the earth contact 13 are connected to a voltage source so that a preferably low electrical voltage of a few volts is applied between the closure element 3 and the valve seat 4. When the valve 1 closes as a result of the closure element 3 coming to bear, a sudden voltage drop occurs, and when the valve 1 opens, a voltage jump occurs. The time profile of the electrical voltage of the circuit with two different potential levels and voltage jumps when an opening or closing event of the valve 1 occurs can be directly evaluated digitally by an evaluation unit 5. A trailing edge in the voltage profile designates here that the valve 1 is closing as a result of the closure element 3 being brought into contact with the valve seat 4 and a rising edge corresponding to a voltage rise designates that the valve 1 is opening as a result of the closure element 3 being lifted off. The time profile of a travel curve of the closure element 3 can be determined from the profile of the voltage of the circuit over time, from which curve, with knowledge of the kinematics of the valve drive, the respective distance between the 4 closure element 3 and the valve seat 4 can be determined precisely for each point in time.

By evaluating the measured voltage profile, the evaluation unit 5 determines the precise opening and closing times as well as the control times of the valve 1 and generates a correlating control variable 17 from the evaluation results. A controller unit 15, to which the control variable 17 can be fed, controls the setting of the valve 1 by feeding valve parameters 18, which can be generated in an optin-dzed way in accordance with the operating point of the internal combustion engine, to a valve controller for activating the cup tappet 6. The controller unit 15 compares the control variable 17 with information relating to the actual control times of the valve 1 with a prescribable command variable and generates appropriately controlled valve parameters 18. The control circuit for optimizing the control times of the valve 1 is thus closed. Ile control, by sensing the actual control times while the internal combustion engine is operating, takes into account all the influences on the valve play such as fluctuating component temperatures, wear or component deformation owing to force effects, and thus permits the internal combustion engine to operate with optimum operating parameters.

Fig. 2 shows an injector 2 for a fuel-injecting internal combustion engine in whose casing 14 a fuel chamber 20 is formed. The casing 14 is penetrated by a closure element 3 which interacts with a valve seat 4 which is formed in the end section of the fuel chamber 20 on the casing, and controls an injection nozzle 16. When the closure element 3 lifts off from the valve seat 4, the injector 2 opens as a result of a fluidic connection of the fuel chamber 20 and the injection nozzle 16 in order to eject fuel. The operation of the internal combustion engine with optimum injection conditions, and thus combustion conditions, requires precise injection control periods and times. A control of the injector control times is provided in order to prevent the component deformation influencing the times when the closure element 3 lifts off from, and comes into contact with, the valve seat 3 owing to the fuel injection under high pressure. A controller unit 15 generates injector parameters 18, which are optimum in terms of operating points, on the basis of a control variable 17 with information relating to the actual control thnes of the injector 2. The control variable 17 is fed to the controller unit 15 by an evaluation unit 5 which determines the actual opening and closing times of the injector 2. The evaluation unit 5 senses here the time profile of the voltage in an electrical circuit in which the interaction of the closure element 3 and of the valve seat 4 form a switch.

An activation element 10 of the closure element 3 and a guide sleeve 8 for supporting and guiding the closure element 3 in the casing 14 of the injector 2 are composed of an electrically non-conductive material, for example ceramics, so that the circuit can close only as a result of the closure element 3 coming to bear against the valve seat 4 at the closing time of the injector. An earth contact 13 of the circuit is arranged here in the casing 14 which has the valve seat 4. The potential at the closure element 3 is applied by sliding contacts 12 which are attached to the guide sleeve 8 and bear against the surface of the closure element 3.

A contact 10 is arranged, connected as an alternative to, or parallel to, the sliding contacts 12, in the activation element 7 of the closure element 3, the operating reliability of the circuit to be measured being increased by the parallel connection of a plurality of contacts. During the injection, that is to say when the injector 2 is opened and the closure element 3 is lifted off from the valve seat 4, a low electrical voltage of a few volts, for example the no-load voltage of a voltage source, is applied to the closure element 3. If the closure element 3 comes into contact with the valve scat 4 at the time when the injector 2 closes, the voltage drops as a result of the circuit being shortcircuited. At the opening time when the closure element 3 lifts off from the valve seat 4 in order to eject fuel, the circuit is interrupted again and the measurable voltage rises suddenly to the higher level. The evaluation unit 5 determines the precise times when the closure element 3 comes into contact with, and lifts off from, the valve seat 4 and thus the actual opening and closing times of the injector 2, from the time profile of the electrical voltage. Since basically only two voltage levels occur, the time profile of the electrical voltage can be directly evaluated digitally by the evaluation unit 5, a trailing edge in the time profile corresponding to the voltage dropping designating that the closure element 3 is being brought into contact with the valve seat 4, and a rising edge designating that the closure element 3 is lifting off. By means of the evaluation of the profile of the voltage over time, the evaluation unit 5 determines the actual opening and closing times of the injector and also the control times and the travel curve of the closure element 3, and generates from them the 6 control variable 17 which is required by the controller unit 15.

In addition to controlling the control periods and control times of a valve, the device according to the invention makes it possible to control working processes of any type where the control process requires precise knowledge of the actual opening and closing times of the valves involved.

7

Claims

1. A device for determining the opening and closing times of a valve openable by lifting off a valve closure element from a valve seat and closable by bringing the closure element into contact with the seat, wherein the valve forms a contact switch in an electrical circuit, and at least one electrical variable is sensed by an evaluation unit.

2. A device according to Claim 1, wherein a control variable adapted to be generated by the evaluation unit as a function of the electrical variable or variables of the circuit is fed to a controller unit.

3. A device according to Claim 2, wherein the valve is adapted to be controlled by the controller unit.

4. A device according to any one of Claims 1 to 3, wherein guide elements and activation elements of the closure element are electrically insulated with respect to a casing having the valve scat.

5. A device according to Claim 4, wherein the activation elements are composed of an electrically non-conductive material.

6. A device according to Claim 4 or 5, wherein the guide elements are composed of an electrically non-conductive material.

7. A device according to any one of Claims 4 to 6, wherein the closure element is integrated into the circuit by means of contact elements which are arranged on a guide element andlor on an activation element and bear against the surface of the closure element.

8.

A device according to Claim 4 or 5, wherein the guide element is a 8 guide sleeve which slidably surrounds the closure element and which is connected to the circuit.

9. A device according to Claim 8, wherein the guide sleeve is insertable into the casing, surrounded by an insulating sleeve made of electrically non-conductive material.

10. A device according to any one of the preceding claims, wherein the evaluation unit senses the change in the electrical voltage of the circuit.

11. A device for determining the opening and closing times of a valve, substantially as described herein with reference to, and as illustrated in, the accompanying drawings.