GB2250801A

GB2250801A - Solenoid actuated control valve

Info

Publication number: GB2250801A
Application number: GB9125357A
Authority: GB
Inventors: Osman Sari
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1990-12-10
Filing date: 1991-11-28
Publication date: 1992-06-17
Also published as: GB9125357D0; FR2670245A1; DE4039351A1

Abstract

A solenoid actuated valve for controlling the flow of exhaust gas recirculated to the induction pipe of an internal combustion engine, particularly of a motor vehicle, has a valve closure assembly which is spring biassed closed and opened when current is applied to a solenoid device (10) and which is additionally loaded by a pressure balancing element, for example a diaphragm (20), whose force effect is approximately equal, but in the opposite direction, to that caused by pressure differences across the valve when it is closed, that is when the plate (5) abuts with the valve seat (6). The pressure balancing element is located such that one side of it is exposed to the pressure upstream of the closure assembly and the other side is exposed either to the downstream pressure or to atmospheric pressure. A valve guide (8) is supported in the valve housing (2) by way of a spherical bearing (33). <IMAGE>

Description

2 2 5 03 3i 1 SOLENOID ACTUATED CONTROL VALVE The invention concerns a

solenoid actuated valve for controlling flow of exhaust gas recirculated into the induction pipe of an internal combustion engine., Such a solenoid actuated valve, also known as a proportional valve, is known from DE-OS 37 03 091, and this valve can vary its opening in proportion to a control signal. It is known from DE-PS 30 43 752 that the recirculation of exhaust gas quantities matched to the particular operating condition of a diesel type internal combustion engine represents an effective means of reducing environmentally polluting constituents in the exhaust gas of the engine.

Recirculation permits, in particular, a reduction in the proportion of nitrogen oxides in the exhaust gas. it is, however, necessary to adjust and control the recirculated exhaust gas quantity along with the fresh air quantity and the injected fuel quantity supplied to the engine, because under certain circumstances, whilst a reduction of nitrogen oxides in the exhaust gas finally discharged can be achieved by this means, this may be accompanied by an increase in the soot, CO and HC proportions occuring.

A device which is used for controlling the exhaust gas recirculation quantity and the injection quantity in compression-ignition internal combustion engines is known from DE-OS 28 49 507. In this, an arbitrarily operable throttle butterfly is provided in the air inlet duct and a pneumatically operated exhaust gas recirculation valve is provided in a recirculation pipe connecting the exhaust gas duct to the air inlet duct. This achieves the effect that little or no exhaust gas is recirculated to the internal combustion engine at idle and at full load, and that the exhaust gas recirculation quantity is controlled at medium 2 load and rotational speed in a way corresponding to the quantity of air induced or corresponding to the load and rotational speed.

The object of exhaust gas recirculation in diesel engines is to reduce the emissions of nitrogen oxides. A diesel engine tends to increasing fomation of soot on reduction of the oxygen content in the combustion mixture, i.e. with a large exhaust gas recirculation contribution. On the other hand, the tendency to increase the emission of polluting constituents in the exhaust gas is greater with increasing proportion of air in the combustion mixture. The maximum quantity of recirculated exhaust gas is required in the lower partload range (because a greater air surplus is present in this condition), and decreases with increasing load. if exhaust gas is recirculated in the lower part-load range to the extent that minimum pollutant emission is achieved, and if the load is suddenly increased from this driving condition, smoke emissions occur which are simultaneously associated with high HC emissions.

Measures for fuel control are, in fact, known from the second of the aforementioned prior specifications cited, and by their means the formation of a smoke emission can be avoided. These measures consist in the fact that the setting motion of the accelerator pedal is connected to the element determining the injection quantity after a dead period and a subsequent transition function of first or higher order. Since, however, these measures involve overloading the accelerator operation with damping elements, etc., and can only be achieved at the cost of high design complexity and since, in addition, they cause a delayed power output of the internal combustion engine (dead period), which is experienced as an unpleasant feature when the engine is used in a vehicle.

3 The use of the solenoid actuated valve known from the first above mentioned prior specification appears sensible because of very rapid switching - as a compromise by means of which the exhaust gas recirculation can be rapidly switched off with a reduced delay in the output of power. However, as will be appreciated, the pressures in the air induction duct and in the exhaust gas duct change continually over the operating ranges of the internal combustion engine so that the flow through the proportional valve, known from the first above mentioned prior specification, must change continually in order to achieve a specified exhaust gas recirculation contribution, it being necessary to design the electromagnetic setting forces necessary for this purpose, for the maximum possible loads, with the associated provision of large amounts of electrical energy, installation space and material.

With this as a basis, the object of the invention is to design a solenoid actuated control valve of the indicated type in such a way that more rapid switch-off can be achieved as compared with the known control valves, the material, energy and installation space requirements for the electromagnetic device being simultaneously reduced. In addition, the control valve is to be designed for mass production, i.e. with the largest possible tolerances on all the component dimensions.

Claims

This object is achieved in the control valve as defined in Claim 1.

Further advantageous features of the invention are defined in the subsidiary claims.

Accordingly this invention provides a solenoid actuated valve for controlling exhaust gas flow recirculated into the induction pipe of an internal combustion engine, and having a valve member, a plate part of which protrudes into an exhaust 4 gas duct and there interacts with a valve seat to close the valve, and the valve member further having a shaft which protrudes from the exhaust gas duct through a valve guide into a housing chamber in which is located an electromagnetic solenoid device whose magnetic armature acts on the valve shaft in such a way that the valve is closed, under the action of spring forces, when no current is flowing through the electromagnetic solenoid device and is opened, against the spring force, when current is flowing, and wherein the valve shaft is additionally loaded by a pneumatic setting device whose force effect is approximately equal to that caused by pressure differences at the valve plate when closed, but in the opposite direction.

Advantages obtainable by means of the invention are given in the following description of illustrative examples which are shown in the drawing.

This shows, in Fig. 1, a solenoid control valve as a sectioned drawing and, in Fig.
2 and 3, alternative embodiments, again as sectioned drawings.

Fig. 1 shows the control valve 1, formed with a housing 2 defining an exhaust gas duct
3 which can be connected on to an exhaust gas passage (not shown) which connects the exhaust gas duct and the air induction duct of an internal combustion engine. A valve plate 5 of a valve member
4 protrudes into the exhaust gas duct 3 and there interacts with a valve seat 6. A valve shaft 7 of the valve member 4 protrudes through a valve guide 8 into a housing chamber 9 in the upper part of which (as seen in the drawing) is located an electromagnetic solenoid device 10.

This consists of an electrical coil 11, a sheet steel cover 12 covering the outer walls of the coil 11, an adjustably fixed iron core 13 and a movable magnetic armature 14. The core 13 and armature 14 are designed as tubular sections, the armature 14 having a plastic insert 15 on which is supported a spring 16 penetrating through the tubular sections. The other end of the spring is supported on a plastic cap 17 which has a connecting cable 18 connected to the coil 11 for supplying current thereto. The armature 14 is guided in a brass sleeve 19 and its end with the plastic insert 15 protrudes into the housing chamber 9.

The housing chamber 9 is divided into two housing chamber sections 22, 23 by means of a pneumatic setting device, here in the form of a diaphragm 20 which is connected to the housing wall, on the one hand, and to the valve shaft 7, by means of upper and lower diaphragm plates 21, on the other. The upper chamber section 22 is connected, via the hollow valve shaft 7, to an exhaust gas duct section 24 located upstream of the valve seat 6 and the lower chamber section 23 is connected to a exhaust gas duct section 25 located downstream of the valve seat 6, through a hole 26. A spring 28 is clamped between the lower diaphragm plate 21 and a sheet metal insert 27 inserted in the lower housing chamber section 23, so that the valve member 4 is pre-loaded in the opening direction or is in contact with the plastic insert 15 of the magnet armature 14.

Underneath the sheet metal insert 27, which, where appropriate, forms a cylindrical bearing 29 for the valve shaft 7, may be seen the valve guide 8 which is formed from a bearing 30 and a spherical bearing 31, the spherical bearing 31 being held in a guide 33 by the force of a spring 32, in this case a clamped leaf spring, the guide 33 having a conical or spherical seat. As shown, the operative face of 6 the closure plate
5 and the lower face of the bearing 31 are both spherical with respect to substantially the same sphere centre. The bearing 30 and the guide 33 are shaped parts of the housing 2.

In the case of engine operation without exhaust gas recirculation, no cur3ent is supplied to the electromagnetic solenoid device 10, so that the magnetic armature 14 is pushed out of the brass sleeve 19 under the action of the force of the spring 16 and the valve plate 5 of the valve member 4 is loaded against the valve seat
6. The closing force of the valve corresponds to the resultant of the forces of the two springs 16, 28.

With the valve closed, the outlet pressures act in the exhaust gas duct section 24 located upstream of the valve seat 6 and the internal combustion engine induction pressures act in the downstream section 25. These pressures acting in the two sections are transmitted via the hollow valve shaft
7 and the hole 26 into the upper and lower housing chamber sections 22 and 23 respectively and, by means of the diaphragm 20, produce a force acting on the valve member 4 which is approximately equal to that caused by the pressures on the valve plate, i. e. the effective area of the diaphragm 20 is equal to that of the valve plate 5.

Fig. 2 shows an embodiment in which, in contrast to that of Fig. 1, the lower housing chamber section 23 is not subjected to the pressure of the exhaust gas duct section 25 located downstream of the valve seat 6 but is subjected to atmospheric pressure. This pressure reaches the lower housing chamber 23 through a wall cut-out 34 in housing 2 which is made sufficiently large so that there is only a very small wall cross-section and hence little heat flux between the lower part and the upper part of the housing. It is 7 obvious that a sufficiently large distance between the housing parts is also provided in order to reduce heat conduction and heat radiation. This embodiment represents a simpler embodiment in accordance with the invention.

Pig. 3 shows an embodiment in which the diaphragm 20 is not connected to the valvd'shaft 7 but to the armature 14. In this embodiment, which can under certain circumstances - be manufactured at a more favourable cost, the upper housing chamber section 22 is connected to the exhaust gas duct section 24 upstream of the valve seat 6 via a housing hole 35 (shown rotated by 900), and the lower housing chamber section 23 is connected to the downstream exhaust gas duct section 25 by the hollow valve shaft 7. The function and the other components are the same as those of Fig. 1.

In all three embodiments, the air gap between the armature 14 and the iron core 13 can be adjusted by pressing the core 13 into the air gap or into the brass sleeve 19; and holes 36 for a press tool, provided for this purpose, can be closed by plugging after the adjustment. The space 37 forming the air gap between the armature 14 and core 13 is connected to the upper housing chamber section 22 via a hole 38 in the plastic insert 15.

In all three embodiments, the armature 14 can also be solidly connected to the valve shaft 7 or, in order to permit alignment tolerances, can be movable radially and in angle (Oldham ring).
8 If required, the position of the valve shaft 7 or of the magnetic armature 14 can be determined by means of a sensor 39, indicated in Fig. 3, with respect to the flow control effect, this sensor 39 being formed by an ohmic (potentiometer), inductive (immersed armature), a magnetoresistive (magnetic field) or a capacitive (polarisation) measurement sensor whose signals are processed in, for example, an electronic control unit into control signals for the electromagnetic device 10.

In the case of engine operation with exhaust gas recirculation, current flows through the electromagnetic solenoid device 10 to suit an exhaust gas recirculation demand, this current producing lines of magnetic force which are collected by the sheet metal cover 12 and the magnetic core 13 and, concentrated in the air gap between the armature 14 and the core 13, these lines of force pulling the armature 14 into the air gap against the force of the spring 16. This motion is followed by the valve member 4 assisted by the force of the spring 28, so that the valve plate 5 is raised from the valve seat 6 and exhaust gas flows through the exhaust gas duct 3 to the air induction duct of the internal combustion engine.

An anti-magnetic layer 42, for example a plastic ring, is advantageously placed between contact surfaces 40, 41 of the magnet core 13 and the armature 14 - or is applied to one of the surfaces - in order to prevent the core and armature from sticking.

I 9 The moving parts of the electromagnetic device 10 are manufactured with low mass so that they require minimal electrical energy for the most rapid adjustment. The sheet metal insert 27 is used, in addition to its employment as part of the guide means for the valve shaft 7 and support for the spring 8, as a heat shield to protect the diaphragm 20.

Advantacres The embodiments according to the invention permit rapid adjustment of the valve member 4 so that load changes can take place in minimal time without intolerable exhaust gases or uneven propulsion faults occurring. The electromagnetic device 10 can be minimized by the light-weight construction used for the moving parts (armature 14 and valve part 4), and by the balanced valve arrangement - or valve force compensation by means of the diaphragm 20, the valve forces being caused by the pressure difference at the valve plate 5.

The spherical-shaping of the operative faces of the valve plate 5, the valve seat 6 and of the valve guide 8 and the housing guide 33, permits manufacturing assembly without difficulty, the valve guidance (bearing) in the spherical bearing 31 taking place with minimum clearance in order to achieve minimum leakage.

CLAIMS 1. A solenoid actuated valve for controlling exhaust gas flow recirculated into the induction pipe of an internal combustion engine, and having a valve member (4), a plate part (5) of which protrudes into an exhaust gas duct and there interacts with a-valve seat (6) to close the valve, and the valve member further having a shaft (7) which protrudes from the exhaust gas duct through a valve guide into a housing chamber, in which is located an electromagnetic solenoid device (10) whose magnetic armature (14) acts on the valve shaft in such a way that the valve is closed, under the action of spring forces, when no current is flowing through the electromagnetic solenoid device and is opened, against the spring force, when current is flowing, and wherein the valve shaft (7) is additionally loaded by a pneumatic setting device (20) whose force effect is approximately equal to that caused by pressure differences at the valve plate (5) when closed, but in the opposite direction.

2. A control valve according to Claim 1, wherein the setting device (20) is located in a housing chamber (9) located between a valve guide (8) and the solenoid device (10), the setting device (20) dividing the housing chamber (9) into two housing chamber sections (22, 23).

3. A control valve according to Claim 2, wherein the pneumatic setting device is constituted by a piston or diaphragm (20), and wherein the housing chamber sections (22, 23) existing on opposite sides of the setting device (20), are connected respectively, with the exhaust gas duct sectidns (24, 25), on the upstream and downstream sides of the valve seat (6).

11 4. A control valve according to Claim 2, wherein the pneumatic setting device is constituted by a piston or diaphragm (20) and the housing chamber sections (22, 23) existing on opposite sides of the setting device (20) are connected respectively, with the exhaust gas duct section (24) on the upstream side of the valve seat (6), on the one hand, and to atmosphere, on the other.

5. A control valve according to Claim 2, wherein one housing chamber section (22) is connected through a hollow valve shaft (7), and the other housing chamber section (23) is connected through a housing hole (26) to exhaust gas duct sections (24, 25), respectively on the upstream and downstream sides of the valve seat (6).

6. A control valve according to Claim 2, wherein one housing chamber section (22) is connected by a hollow valve shaft (7), to an exhaust gas duct section (24) on the upstream side of the valve seat (6) and the other housing chamber section (23) is connected by a housing wall cut-out (34) to atmosphere.

7. A control valve according to any one of the preceding claims, wherein the electromagnetic solenoid device (10) has an adjustable magnet core (13) by means of which an air gap between the magnet core (13) and a magnetic armature (14) is pre-set.

1 12 8. A control valve according to any one of the preceding claims, wherein the spring force acting on the valve member (4) is the resultant of a spring force (16) acting on the magnetic armature (14) and a smaller spring force (28) acting on the valve member (4) in the opening direction, and wherein the magnetic armature (14) and the valve shaft (7) are pressed together underthe action of the force of both springs (16, 28).
9. A control valve according to any one of the preceding claims, wherein a guide (8) for the valve member (4) is formed from a housing bearing (30) and a spherical bearing (31), the spherical bearing (31) being held in a housing guide (33) against a seat on the bearing (30) under the action of spring force.
10. A control valve according to any one of the preceding claims, wherein the valve plate (5) and the valve seat (6) are designed to be spherical where they interact.
11. A control valve according to any one of the preceding claims, wherein the position of the valve member (4) and hence its flow control effect is determined by a sensor (39)
12. A control valve according to Claim 11, wherein the sensor (39) is an ohmic, an inductive, a magneto-resistive or a capacitive measurement sensor.
13. A control valve according to any one or more of the preceding claims and substantially as described with reference to any one of the accompanying drawings.