Internal combustion engines

Abstract

An internal combustion engine has inlet and/or exhaust valves which are held in open or closed positions by magnetic field generated by a solenoid. Resilient means are provided to bias the valve against the action of the magnetic field. The magnetic field is generated periodically, as a function of engine speed, by activation of a scanning means activated by light or other radiation periodically being allowed to pass to the scanning means by way of an aperture in a mask.

Description

This invention relates to internal combustion (i.e.) engines. It is concerned with i.c. engines having at least one cylinder having a fuel inlet and/or an exhaust outlet valve and is particularly applicable to atmospheric pollution control.

According to one aspect of the present invention there is provided an internal combustion engine having at least one cylinder with a poppet valve displaceable between an open and a closed position by means of a magnetic field generator which acts on the valve against a biassing action provided by resilient loading means.

According to a second aspect of the invention the generator of the first aspect is periodically energised by way of an activated scanning means; the scanning means being activated by the passage of a beam of light or other radiation to the scanning means from a source of the radiation through an aperture periodically interposed between scanning means and source. Typically the aperture is provided in a drum rotatable about an axis at a speed which is a function of the engine speed.

A vehicle exhaust valve and ignition system will now be described with reference to the accompanying drawings of which:

FIG. 1 shows a cross-sectional view of a magnetically operated valve;

FIG. 2 is a force diagram of solenoids and springs described in connection with FIG. 1;

FIG. 3 shows diagrammatically a multichannel signal transmitting and scanning means for the control of an internal combustion engine equipped with valves similar to that shown in FIG. 1;

FIG. 4 is a developed view of part of FIG. 3; and

FIG. 5 shows a block diagram of a control circuit incorporating a number of valves similar to that shown in FIG. 1 and the transmitting and scanning means of FIG. 3 and 4.

FIG. 1 shows a solenoid operated valve which enables typical working loads to be provided for an exhaust valve in an internal combustion engine. The valve is also suitable for use as an inlet valve but this function is not further detailed since the exhaust valve duty is more onerous than that of the inlet valve.

Part of a cylinder head 11 is shown in which a combustion chamber 12 is isolated from an exhaust duct 13 by an exhaust poppet valve 14. Head 15 of valve 14 seats on a valve seating 16 to isolate the chamber 12 from duct 13. The head 15 is formed integrally with a stem 17 which slidably locates the valve in a sleeve guide 18. End 19 of stem 17 incorporates a groove 20 in which seats a split collar 20a. The collar serves to retain a flanged washer 21 on which one end of a closing control spring 22 seats. The other end of spring 22 is seated against the cylinder head 11 by way of an end stop 23. The flanged washer 21 retains the inner periphery of a closing belleville washer 24. The end 19 of stem 17 has mounted on it a spacer 25 whereby the stem 17 can be displaced by spindle 26 which is of non-magnetic material.

Spindle 26 has rigidly secured to it a closing plunger 27 and an opening plunger 28. The spindle 26 and plungers 27, 28, are slidably disposed in solenoid body 29 which is rigidly mounted in valve body 30. Mounting is by way of an externally threaded ring 31 by means of which flange 32 of solenoid body 29 is axially retained on seat 33 in the valve body 30. Radial location of the solenoid body 29 in the valve body is by way of ring seals 34, 35 mounted on integral internal flanges in the valve body.

Opening plunger 28 has seated on it an opening belleville washer 36 (shown compressed) and is resiliently biassed away from an end support 37 by way of an opening control spring 38. Solenoid end check 39 limits movement of opening plunger 28 away from end support 37. In a similar manner end check 40 limits movement of closing plunger 27 away from end stop 23.

The solenoid body 29 has mounted within it an opening coil 41 and a closing coil 42. Leads, not shown, enable the coils to be energised, as will be hereinafter described, to open or close valve 14.

Solenoid body 29 and valve body 30 define between them an annular volume 43 into which cooling water is fed by supply pipe 44 and from which water is withdrawn by outlet pipe 45. In this way the coils 41, 42 are maintained at an optimum temperature despite their relative proximity to combustion chamber 12.

Before operation of the valve of FIG. 1 is described attention is drawn to FIG. 2 which shows graphically forces arising from operation of the valve of FIG. 1. The abscissa shows axially valve displacement (in inches) from the fully closed position at the origin to the fully open position at the right hand extremity of the axis. The ordinate shows the force exerted by:

i. opening control spring 38 as curve 38A;

ii. opening belleville washer 36 as curve 36A;

iii. closing control spring 22 as curve 22A;

iv. closing belleville washer 24 as curve 24A;

v. net spring force arising from items (i) to (iv) above as curve S;

vi. opening coil 41 as curve 41A;

vii. closing coil 42 as curve 42A.

(a) Valve closed

Assuming engine operating conditions with the relative positions of the system as shown in FIG. 1 current passes through closing coil 42 to hold plunger 27 within coil 42 so retaining the valve head 15 on its seat 16.

__________________________________________________________________________ The coil 42 force on closing plunger 27 = 160 lbs. The composite spring force trying to open the valve = - 130 lbs. Thus, the resultant force on the valve holding it shut = + 30 lbs. The composite spring force is made up of the following components: The force exerted by the belleville washer 36 = - 90 lbs. The force exerted by the control spring 38 = - 110 lbs. The force exerted by the control spring 22 = + 70 lbs. Resultant spring force = - 130 lbs. When the valve is closed the maximum force which can be exerted on the valve seat is that of control spring 22 = 70 lbs. The valve will stay closed until the current through coil 42 stops. The resultant force on the valve is then The coil 42 force on closing plunger 27 = 0 lbs. The coil 41 force on opening plunger 28 = 0 lbs. The composite spring force trying to open the valve = 130 lbs. Thus, the resultant force on the valve accelerating it open = + 130 lbs. (b) Valve on 0.030" Lift This stage occurs at a point in the force diagram when the force exerted by the belleville washer 36 reduces to zero The coil 41 force on opening plunger 28 now depends on the rise time of the coil 41 = + 5 lbs. The composite spring force accelerating the valve open = + 30 lbs. Thus, the resultant force on the valve accelerating it open = + 35 lbs. (c) Valve on Half Lift 0.13" The coil 41 force on opening plunger 28, determined by the rise time of the coil 41 = 12 lbs. The composite spring force = 0 lbs. Thus, the resultant force on the valve accelerating the valve open = 12 lbs. (d) Valve 0.03" from Full Lift This stage occurs at a point in the force diagram when the belleville washer 24 is on the point of being compressed. The coil 41 force on opening plunger 28, determined by the rise time of coil 41 = + 50 lbs. The composite spring force trying to prevent the valve from opening = - 30 lbs. The resultant force on the valve pulling it towards full lift = + 20 lbs. __________________________________________________________________________

A critical period thus exists between steps (a) and (d) when the force exerted on the valve is small. Thus, if the surface area of the valve in question is large and the pressure in the cylinder, even with the valve half-open, is greater than say 10 p.s.i., the valve may not open in the opening period when coil 42 is energised.

The situation can be improved by increased rate control springs changing from 30 lbs. to 130 lbs., giving a resultant composite spring changing from 100 lbs. to 0 to 100 lbs. over the full valve lift. An equivalent reduction in belleville poundage would also be required.

__________________________________________________________________________ (e) Valve on Full Lift 0.26" The coil 41 force on opening plunger 28 now rises to a peak from say = + 80 lbs. to + 160 lbs. The composite spring force trying to prevent the valve from opening = - 130 lbs. Thus, the resultant force on the valve pulling it to full lift = - 50 lbs. to + 30 lbs. __________________________________________________________________________

For valve closure, the reverse of the above steps occurs.

The seating of the plungers 27, 28 is relatively slow and when the valve is closing, the valve also seats slowly onto its seat over the last 0.030 inch of travel. On valve opening, the springs 36, 37 push the plunger 28 which opens the valve; on valve closing, the springs 22, 24 push the washer 21 which pushes the plunger 27 because of the valve stem 17 and spindle 26 are separate entities.

FIGS. 3 and 4 show features of a multichannel signal transmitter and scanning means used to generate signals which are utilised, to operate ignition system and valves of a four cylinder i.c. engine.

FIG. 3 shows a hollow timing drum 50 of transparent plastic mounted on a splined shaft 51 which rotates at half engine speed. The drum 50 is mounted within a housing 52. Projecting into the open end of the drum 50 is an inner carrier 53 on which are mounted nine gallium arsenide light emitters. The inner carrier 53 is disposed parallel to the axis of rotation of drum 50. Parallel to the inner carrier 53 but outside the drum 50 is an outer carrier 54 of nine light activatable switches. Secured to the housing 52 is an advance/retard mechanism in the form of a cover 55 from which projects a displaceable piston 56. Carriers 53, 54 are fixed to the piston 56 which is displaceable in direction A by suitable electric or hydraulic means to vary the axial position of carriers 53, 54 relative to the drum 50 in dependence upon engine speed or any other required parameter. The drum carries a photographic negative 57 which is generally opaque except for timing lines 58 which allow light from an emitter on inner carrier 53 to pass through the drum wall to activate a corresponding switch on outer carrier 54.

A developed view of the negative 57 and outer carrier 54 is shown in FIG. 4. The drum is divided axially into nine channels 60-68 which rotate in the direction of arrow 69. Each of channels 60-68 has a slot in it, typically slot 70 in channel 65, exposing light from one of the emitters on the inner carrier. Each channel 60-68 of the drum is scanned by one of the light activated switches 60A to 68A on the outer carrier 54. The inner and outer carriers can be displaced from the rest position shown in the direction of arrow 71 by an amount in direct proportion to engine speed and also to engine load or any other required variable. This displacement causes the part of each slot in a given channel that is "seen" by the appropriate switch to differ in its relative position on each rotation of the drum. Thus in the case of slot 70 in channel 65 at low engine speeds the switch 65A "sees" the lower end (as shown in FIG. 4) of illuminated slot 70 on each rotation of the drum 50. With increasing engine speed the switch 65A is driven upwardly in the direction of arrow 71 so traversing the channel 65 and scanning the upper end of slot 70 so effectively advancing the transit time of slot 70 past switch 72 for each revolution of drum 50. Conversely with decreasing engine speed the switch 65A moves in the opposite direction to arrow 71 and returns towards scanning the lower end of slot 70. The passage of any part of a slot in any given channel past its corresponding reading switch causes the head to generate an appropriate pulse. In this way the nine switches on outer carrier 54 cause pulses A to I to be generated and transmitted from separate outputs. The pulses A to I are used to provide control of a four cylinder i.c. engine, with the cylinders firing in the order 1-3-4-2 and having inlet valves I to I.sub.4 and exhaust valves E.sub.1 to E.sub.4, as follows:

Advance Range Available by Pulse Open Close Head Displacement ______________________________________ A I.sub.1 E.sub.1 0 - 17.degree. B E.sub.3 I.sub.1 0 - 57.degree. C I.sub.3 E.sub.3 0 - 17.degree. D E.sub.4 I.sub.1 0 - 57.degree. E I.sub.4 E.sub.4 0 - 17.degree. F E.sub.2 I.sub.3 0 - 57.degree. G I.sub.2 E.sub.2 0 - 17.degree. H E.sub.1 I.sub.4 0 - 57.degree. ______________________________________

I provides set/reset, ignition and engine speed pulses.

The slots in each channel can be straight or curved so that for a linear movement of the carriers variable rates of advance and retard can be achieved for each output pulse. The width of the lines will be as small as possible for accuracy of timing but wide enough to let sufficient light through to activate the switch at high speed. To achieve this end a slot of varying width along its length can be used.

FIG. 5 shows circuitry utilising the pulses A, D, H and I generated for use with an i.c. engine as described in connection with FIG. 4. To avoid duplication the circuitry shows only components concerned with ignition and the opening and closing of the inlet (I.sub.1) and exhaust (E.sub.1) valves of the first cylinder of the four cylinder engine. For the other three cylinders most of the components shown would be repeated for each cylinder and the remaining pulses B, C, E, F and G are utilised. Pulses fed to inputs on the left hand side of the circuitry shown in FIG. 5 are utilised to operate coils 81, 82, 83, 84 on the right hand side. Inlet valve coils 81, 82 are similar to, and operate in the same way as, coils 41, 42 described in connection with FIG. 1. Thus energising coil 81 will cause inlet valve I.sub.1 to be opened and energising coil 82 will cause inlet valve I.sub.1 to be closed. Exhaust valve coils 83, 84 likewise are similar to, and operate in the same way as, coils 41, 42. Energising coil 83 will cause exhaust valve E.sub.1 to be opened and energising coil 84 will cause exhaust valve E.sub.1 to be closed.

To allow selection of the inlet valves coil 81 or 82 a bistable 85 is used having "open" output 86 and "close" output 87. To obtain an output from bistable 85:

i. a "set" pulse needs to be fed to the bistable by way of input 88 from set/reset gate 89 which is adapted to receive I pulses at input 90; and

ii. either an open or close pulse needs to be fed to the bistable 85 by way of inputs 92, 93.

The set/reset gate 89 is used for setting up the electronics in the correct order when starting and stopping the engine. The set/reset gate is rendered inoperative when the engine is running at a speed greater than 100 rpm.

Input 92 is adapted to receive A pulses as open signals and input 93 is adapted to receive D pulses as close signals by way of monostable 94. The monostable is variable in proportion to engine load as sensed by way of sensor 91 incorporated in a torque converter forming part of a transmission system driven by the engine.

Output 86 feeds coil 81 by way of a synchronising arrangement made up of a paralleled multivibrator 96 and a monostable 97. Amplifier 98 is used to provide a current of sufficient amplitude to hold open coil 81. The monostable 97 provides a pulse wide enough to open the valve. Thereafter the multivibrator 96 supplies current to hold the valve open.

Output 87 feeds solenoid 82 by way of an amplifier 99. In this case a synchronising arrangement comparable to that provided by multivibrator 96 and monostable 97 can be used to speed up valve closure. It has not been included here in order to limit complexity of the circuitry.

To allow selection of the exhaust valve coil 83 or 84 a bistable 101 is used having open output 116 and close output 117. To obtain an output from bistable 101:

i. a set pulse needs to be fed to bistable 101 by way of input 102 from set/reset gate 89; and

ii. either an open or close pulse needs to be fed to the bistable by way of inputs 103, 104.

Input 103 is adapted to receive H pulses as open signals and input 104 is adapted to receive A pulses as close signals by way of monostable 105. The monostable 105 is controllable by way of an input 106. The monostable is variable in proportion to engine load as sensed by sensor 91.

Output 102 feeds coil 83 by way of a synchronising arrangement made up of a paralleled multivibrator 109 and a monostable 110 which feeds an amplifier 111 so as to provide a voltage of sufficient amplitude to operate coil 83.

Output 103 feeds coil 84 by way of an amplifier 112.

I pulses fed to input 90 of set/reset gate 89 are also fed by way of line 113 to a spark generator and by way of monostable 114, serving as a tachometer drive, to a tachometer display 115.

Operation of the four cylinder vehicle engine equipped with inlet and outlet valves according to FIG. 1, multichannel signal transmitter and scanning means according to FIGS. 3 and 4 and the control circuit of FIG. 5 is as follows.

With the engine running drum 50 (FIG. 2) rotates at half engine speed with ignition occurring in the cylinder order 1-3-4-2. The various switches 60A to 68A (FIG. 4) pass over and so scan each of channels 60 to 68 respectively. Any resulting output pulses A, D, H or I are fed to the control circuit of FIG. 5 which relates to the first engine cylinder and three similar circuits, not shown, which control the second, third and fourth cylinders. An A pulse arrives at input 92 to bistable 85 once every drum revolution, that is to say once every 2 engine revolutions. At the same time an I pulse is fed to input 88 of the bistable 85 by way of set/reset gate 89. On bistable 85 being switched by the A and I pulses open output 86 feeds the paralleled monostable 97 and multivibrator 96. As a result open coil 81 is fed current by way of amplifier 98 so causing the inlet valve governed by coil 81 to open in the manner described in connection with FIG. 1. The valve will remain open until bistable 85 is switched by the application of a D pulse fed to input 93 by way of monostable 94. The necessary D pulse arises from the passage past switch 63A (FIG. 4) of the slot contained in channel 63. The arrival of the D pulse at the bistable 85 will switch the bistable from open output 86 to close output 87. As a result the close coil 82 is energised by way of amplifier 99 resulting in the valve governed by the coil being closed in the manner described in connection with FIG. 1.

Arrival of an A pulse at input 92 causing the inlet valve to be opened is matched by the arrival of a similar pulse at close input 104 of bistable 101. The simultaneous arrival of an I pulse fed to input 102 of bistable 101 by way of set/reset switch 89 results in the bistable being switched to give an output on close output 117 resulting in close coil 84 being energised to close so causing the exhaust valve governed by coil 84 to be closed. The exhaust valve will remain closed until bistable 101 is switched by the application of an H pulse fed to input 103. The necessary H pulse arises from the passage past switch 67A (FIG. 4) of the slot contained in channel 67. The arrival of the H pulse at the bistable 101 switches the bistable from close output 117 to open output 116. Output 116 feeds the paralleled monostable 109 and multivibrator 110. As a result the open solenoid 83 is fed current by way of amplifier 111 causing the exhaust valve governed by solenoid 83 to open in the manner described in connection with FIG. 1.

The necessary ignition pulses for a spark plug mounted in the cylinder are derived from the I pulses arriving on line 113.

In the event that engine speed, or the engine loading detected by sensor 91 are increased then the outer carrier 54 (FIGS. 3 and 4) is driven in the direction of arrow 71. This provides for advancing, or retarding, of valve opening or closing by provision of a suitably angled slot in the appropriate channel of channels 60-68. Conversely with a reduction of engine speed, or loading, the outer carrier 54 is returned, in the opposite direction to arrow 71 to the position shown in FIG. 4.

Among a number of advantages conferred by the specific embodiment it will be apparent that an engine of the type described can be readily modified, for research and development purposes, to determine the effect of varying individual valve and ignition pulse timing and of varying valve overlap.

Claims

We claim:

1. An internal combustion engine having:

a. a block including at least one cylinder;

b. the block defining a duct providing access to the cylinder;

c. a tappet valve having a stem and a valve head, the stem being disposed in, and slidable relative to, the block for movement between a closed position in which the valve head isolates the duct from the cylinder and an open position in which the valve head allows the passage of fluid between the duct and cylinder;

d. magnetic means linked to the valve stem;

e. a magnetic field generator mounted on the block and adapted to generate a magnetic field to retain the valve, by way of the magnetic means, in the open or the closed position; and

f. resilient means disposed on the block, and adapted to act between valve and block to bias the valve against the action of the magnetic field of the generator, said resilient means comprising first and second belleville spring washers so disposed between valve and block that, in the open position, the first belleville spring washer is fully compressed while the second belleville spring washer is uncompressed and, in the closed position, the second belleville spring washer is fully compressed while the first belleville washer is uncompressed.

2. An internal combustion engine as claimed in claim 1 wherein the generator incorporates means whereby it is periodically energised by way of a scanning means activated by the passage of a beam of light or other radiation to the scanning means from a source of the radiation through a mask member defining an aperture periodically interposed between scanning means and source.

3. An internal combustion engine as claimed in claim 2 wherein the mask member is displaceable from a datum position, by an amount dependent on the engine speed, to vary that part of the aperture through which the radiation passes to the scanning means.

4. An internal combustion engine as claimed in claim 3 wherein the mask member is a cylinder rotating about its longitudinal axis, the aperture being provided in the cylinder wall, the datum position lying on the axis and the cylinder being displaceable axially therefrom by the amount.

5. An internal combustion engine as claimed in claim 1 comprising a spark ignition device connected to a second scanning means and a second aperture in the mask member to allow the periodic passage of light or other radiation from a source to the second scanning means to initiate spark ignition by the device.