CA1208999A

CA1208999A - Turbo-charged compression ignition engine operable at small compression ratio

Info

Publication number: CA1208999A
Application number: CA000432473A
Authority: CA
Inventors: Hiroshi Kanesaka
Original assignee: Usui Kokusai Sangyo Kaisha Ltd; Kanesaka Gijutsu Kenkyusho KK
Current assignee: Usui Kokusai Sangyo Kaisha Ltd; Kanesaka Gijutsu Kenkyusho KK
Priority date: 1982-07-21
Filing date: 1983-07-14
Publication date: 1986-08-05
Also published as: JPS5918230A; JPS6364617B2; DE3326133C2; FR2530730A1; GB8318837D0; GB2123483B; US4502282A; GB2123483A; DE3326133A1; FR2530730B1

Abstract

ABSTRACT OF THE DISCLOSURE
A turbo-charged compression ignition engine having a turbo-charger (40) for supercharging the engine, a mechanism (56, 59) for controlling the timing of closing of the inlet passage (42) of the engine, and an auxiliary cam for opening the exhaust valve of the engine at a point near the bottom dead centre in the suction stroke. The area of the nozzle of the turbine of turbo-charger is controllable by a rotor-type mechanism (69). A passage formed in the rotary-type mechanism opens to the downstream side of this mechanism.
The passage is communicated with the inlet pipe of the engine through a passage (42a).

Description

TURBO-CHARGED COMPRESSION IGNITION ENGINE
OPERA13LE AT SMZ~LL COMPRESSION RATIO

The present invention relates to a turbo~charged compression ignition engine of low compression ratio type.
It is well known that combustion pressure, and hence, output power of an engine are increased as supercharging pressu~e is increased so that ~he maximum p~wer output of the engine is determlned by the maximum allowable pressure.
It is possible to increase the power, while maintaining the maximum combustion pressure below the maximum allowable pressure, hy decreasing the compression ratio. This, however, leads to problems such as difficulty in starting the engine, misfire during light-load operation and so forth. In the case of a diesel engine which is designed lS to operate at a compression ratio of around 8:1, it is possible to obtain a mean effective pressure of about 32 Kg/cm .
To enable the background to the invention to be explained with the aid of diagrams, the figures of the drawings will first be listed.
Figure 1 is a diagram of operational characteristics of a compression ignition type engine, showing particularly the misEire zone region in relation to output torque and engine speed;
Figure 2 is a sectional view of an exhaust turbine of a turbo-charged engine in accordance with an embodiment of the invention;

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Figure 3 is a sectional view taken along the line III-III of Figure 2;
Figure 4 is a sectional view of part of the exhaust-turbine on the line VI-VI of Figure 3;
Figure 5 is a PV diagram;
Figure 6 is a sectional view of a part of a 4-stroke cycle engine in accordance with an embodiment of ~he invention;
Figure 7 is a sectional view taken along the line VII~VII of Figure 6;
Figures 8 and 9 are graphs showing how the opening area of the intake valve and the pressure in the cylinder are changed in relation to the crank angle, Figure lO (with Figure 7) is a front elevational view of a cam;
Figure 11 is a diagrammatic illustration of a turbo-charged compression ignition engine in accordance with an embodiment of the invention;
Figure 12 is a graph showing the relationship between the engine speed and the polytropic index in the compression stroke; and Figure 13 is a diagram showing the performance of a turbo~charger;
In the misfire region shown hatched in Pigure 1 of the accompanying drawings, however, the level of the load imposed on the engine is low so that the turbo-charger cannot exert its power. As a result, the pressure and temperature of the induced air are lowered so that the ~x..~.

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desired ignitîon temperature is not reached in the compression stroke. In such a case, white or blue smoke having an offensive smell is discharged from the exhaust side of the engine and the engine finally becomes inoperative due to misfiring.
In order to obviate this problem, two countermeasures have been proposed: namely, a variable compression type method and a hyperbar method. These countermeasures are~
however, used only in weapons because the former requires a complicated control mechanism while the latter suffers from an impractically large drop in thermal efficiency.
Accordingly, it is a primary object of the invention to provide a turbo-charged compression ignition engine which can operate in a stable manner even at a low compression ratio, thereby avoiding the above-descrih~d problems of the prior art.
To this end, according to the invention, there is provided a turbo-charged compression ignition engine comprising: a turbo-charger for supercharging said engine, 2Q control means for controlling the timing of closing of an inlet passage of said engine, opening means for opening an exhaust valve of said engine at a point near bottom dead centre in the suction stroke, means for varying the area of a nozzle in the turbine of said turbo-charger and said ~5 last mentioned means defining a passage openable to the downstream side of said last mentioned means, and an inlet pipe communicating with said last mentioned passage.

Re~erring to Figures 2 to 4, a turbine casing 1 o a turbo-charger has a nozzle 2 which is provided with a plurality of nozzle vanes of a fluid-dynamical profile.
In the illustrated embodiment, the nozzle 2 has three nozzle vanes 2a, 2b and 2c. Exhaust gas coming from an exhaust gas inlet 3 is accelerated and orientated as it flows through the nozzle 2 and then drives a turbine 4.
A rotor 5 is provided with shafts 5c and 5d ~see Figure 3) which are rotatably supported in bearings by the 10. turbine casing 1 and a cover 6. A lever 7 is fixed to the shaft 5c. When the lever 7 occupies a position shown in full lines, the rotor 5 also occupies a position illustrated in full lines. The nozzle 2 can be of conventional constructionO
1~ As the lever 7 is rotated clockwise as indicated by an arrow in Figure 2, the rotor 5 is also rotated to move one end 5a thereof into the nozzle 2 thereby to reduce the nozzle area. In consequence, the pressure at the exhaust ~2~

inlet 3, i.e. the exhaust pressure of the engine, is increased to increase the velocity of the gas flowing in the nozzle 2, thereby to increase the power ou-tput of the turbine 4. As a result, the driving power for driving the compressor is increased to elevate the charging air pressure.
As the lever 7 is rotated to the position shown by a chain line in ~igure 2, the end 5a of the rotor 5 can be moved to the illustrated position to form a nozzle of an extremely small area. In this state, the turbine efficiency is low and the pressure at the turbine inlet is much higher than the pressure at the compressor outlet.
As will be understood from the P-V diagram of ~igure 5, the engine has to produce work corresponding to the hatched area for expelling the exhaust gas so that the fuel consump--tion is inevitably increased. In the low-speed and light-load operational condition of the engine, this ~ork is essential ~or operating the turbo-charger, and the charging pressure `can be increased àt a cost of reduction in the -thermal e~ficiency.
~0 ~he rotor 5 is provided with a passage 5b which is kept closed during normal opera-tion as shown in Figure 2.
~he nozzle area, however, is decreased as the rotor 5 is rotated clockwise. At the same time, the passage 5b provides a communication between the nozzle 2 and a passage 8 which is connected to the compressor outlet of the turbo-charger through a connection port 9 shown by chain line.

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In the high-speed no-load operation of the engine, the work corresponding to the hatched area in Figure 5, i~e~ the negative work, can be utilized as an exhaust brake.
~ igure 4 shows a state in which the rotor 5 has been rotated counter-clockwise. ~s will be understood from the Figure, the rotor in this position produces the same effect as that produced when the same is rotated clockwise.
The turbo-charger of the invention can maintain a high charging pressure even when the flow rate of air is small, by an efficient use of the high gas pressure at the turbine inlet. As will be detailed later, it is possible to prevent misfire during light-load operation, by m~ki ng an efficient use of this ~eature.
Figure 6 shows a 4-stroke cycle turbo-charged compression ignition engine in accordance with the invention. The engine has a plurality of cylinders 10 ~only one of which is shown) each slidably and reciprocally receiving a piston 11 which is pivotally connected to the upper end~of a piston rod 12. ~he lower end o~ the piston rod 12 is connected to a cranksha~-t tnot shown). ~he cylinder 10 carries a cylinder head 13 in which are formed an inlet port 14 and an exhaust port 15.
An inlet valve 16 and an exhaust valve 17 are arranged in the port 14 and 15 9 respectively.
A rotary valve 19 is disposed in an inlet pipe 18 connected between ~he inlet port 14 and the turbo-charger (not shown in this Figure). ~he rotary valve 19 ls driven -by -the crankshaft of the engine through a gear mechanism so as to serve as a control Valve, an example of such a mechanism being explained below with reference to Figure 7 The rotary valve 19 is fixed by a pin 21 to a drive shaft 20 and is clamped between sleeves 22 and 23 on the shaft 20. A further sleeve 24 is also carried by the drive shaft 20. ~he drive shaft 20 is rotatably supported by ball bearing as assemblies 25, 26 and 27 disposed respecti~-ely between the sleeves 22, 23 and 24 and the wall of the inlet pipe 18.
A rotary shaft 32 is rotatably supported by a frame 28 through ball bearing assemblies 29 and 30, and is adapted to be driven by a timing gear 31 which is connected drivingly to the crankshaft (not shown) through a gear mechanism. ~he drive shaft 20 is connected to the rotar~ shaft 32 through an adjusting member 33 constituting a means for adjusting the opening and closing timings.
As will be seen from Figure 9, the rotary valve 19 is designed to open and close at an interval of about 90. ~he rotary valve 19 is driven at a speed which is a half of the speed of the crank shaft.
On the other hand, the period of the suction stroke of the engine is about 180ain terms of the crank angle.
~here~ore, the rotary valve 19 has an opening period of about 180 in terms of the crank angle as in the case of the inlet valve 16.
An explanation will be made below as to the construction of means for adjusting the opening and closing timing~ of the rotary valve 19, with specific reference to Figure 7.
The opposing ends of the drive shaft 20 and ~he rotary shaft 32 are provided with helical splines 20a and 32a of opposite hand. ~he splines 20a and 32a engage with projec-tlons formed on the inner peripheral surface of the adjusting member 33. ~he arrangement is such that, as the adjusting member 33 is moved axially in one direction, the drive shaft 20 makes an angular displacement in a predetermined direction with respect to the rotary shaft 32, while movement of the adjusting members 33 in the opposite axial direction causes an opposite angular displacement of the drive shaft 20. It is thus possible to change the timing of rotation of the drive shaft by the movement of the adjusting member 33, thereby to adjust the opening and closing ti ming~ of the rotary valve 19.
~ he axial movement of the adjusting member 33 is caused by rocking movement of an adjusting lever 34 having one end located in an annular retAi ni ng groove 33a ~ormed in the outer peripheral surface of the adjusting member 33. ~he adàusti~g lever 34 is supported rockably by a shaft 35.
The other end of the lever 3~ is operatively connected to a control mechanism (not shown in Figure 7).
An explanation will be made hereinunder as to the operational timing of the inlet valve 16 and the rotary valve 19, with reference to Figures 8 and 9, as well as the P-~

diagram.
In Figures 8 and 9, full-line curves A in the upper part of the charts show the lift or opening area of the inlet valve 16 in relation to the crank angle of the engine, whereas the broken-lines B show how the opening angle or opening area is changed.
In the full-load operation of the engine as shown in Figure 8, both the inlet valve 16 and the rotary valve 19 start to open in the initial period of the suction stroke at around a point (a) near the suction top dead centre.
In the final period of the suction stroke, both of the inle-t valve 16 and the rotary valve l9 start to close at a point near the point ~b). ~he P-V diagram in the full-load oper-ation is thus identical to that attained in the conventional engine.
As shown in Figure 9, during the light-load operation to which the inven-tion pertains, the rotar~ valve 19 starts to open as shown by the broken-line curve B in advance to the opening of the inlet valve 16, by the axial movement of the adàusting member 33 through the action of the adjusting mechanism which will be explained later. ~hus, no suction occurs as the rotary valve 19 initially opens because the inlet valve 16 lS stlll closed at that moment. When the inlet valve 16 starts to open, the rotary valve 19 is almost fully open and at an intermediate point (c) of the suction stroke, the rotary valve 19 closes. ~he inlet valve 16 closes at the end of the _ 9 ~ ~ .

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suction stroke near the bottom dead centre of the stroke of the piston 11.
When the inlet val~e 16 starts to open in the ini-tial period of the suction stroke, the rotary valve 1~ has been opened fully so that the air is introducèd to the cylinder 10. At an intermediate point (1) of the suction stroke, however, the rotary val~e 19 is closed as will be seen ~rom the curve in the lower part of Figure 9, as will be under-stood from the comparison with the broken-line B.
At this moment, the exhaust val~e designated at 17 in Figure 7 is opened by the action of an auxiliary exhaust cam which will be explained later in connection with Figure 10, so that the hot exhaust gas o~ a pressure elevated by the turbo-cha~ger starts to be drawn into the cylinder. ~he exhaust gas is introduced only during the period between the points (1) and (2) shown in ~igure 9.
In this state, the inlet passage has been closed by the rotar~ valve 19 so that the e~hal~.st gas of high-pressure a~d high-temperature does not escape to the inlet side o~ `

2~ ~he engine. ~he high pressure exhaus-t gas introduced into the Gylinder h~ats and pressurises the air in the cylinder 10 to ~orm a mixture having an extremely high temperature and pressure at the point (shown at 2 ln Figure 9) of com-: mencement of the compression stroke. At this moment, both f the inlet and exhaust valves 16 and 17 are closed toensure ignition which ~ill take place at the end of the ~8~

compression stroke ~ow commenced.
Figure 10 shows a known exhaust cam incorporated in the engine of the invention. The cam has two cam portions:
namely, a main cam 36 and an auxiliar~ cam 37. ~he main cam 36 has the same function as the ordinary exhaust cams to open the exhaust valve 17 during the exhaust stroke, while -the auxiliary cam 37 has a function to open the exhaust valve 17 at a moment near the bo-ttom dead centre in the suction stroke as will be seen from Figure 9.
An explanation will be made below as to the construction and operation of a turbo-charged compression igni-tion engine in accordance with the invention designed to operate even at a low compression ratio.
Referring to Figure 11, the compressed air or mixture discharged from the compressor 41 of the turbo-charger 40 is introduced into the cylinders of the engine (indicated at 46) through an inlet pipe 42, intake manifold 43, air cooler and branch pipes 45. ~he e~haust gas emitted from the en~ine L~6 acts on an exhaus-t turbine 48 (of the same type as the turbine 4 shown in Figures ? to 4) of a turbo-charger 40, through an exhaust pipe 47. ~he exhaust turbine ~8 is provided with a variable area noæzle of the type shown in Figures 2, 3, and 4. The exhaust gas then drives the turbine and is expanded to the atmospheric pressure before it is relieved to the atmosphere.
A drive shaft 49 connected to one end of -the ~rankshaft ~08~3399 rotates as ~ unit with the latter as the engine 46 operates.
The drive s;-aft 49 carries at its one end a gear 50 which meshes and drives a timing gear 51 for driving various devices such as a cam shaft carrying the exhaust cam 36 shown in ~i~ure 10, fuel injection pump and so forth. The gear 50 meshes also with the drive gear 52 for driving the rotary valve serving as a control valve. ~he gear 50 drives the drive gear 52 at a speed which is a half of that of the crankshaft speed.
Ro-tary valves 53 of the two-blade type similar to the rotary valve 19 shown in ~igure 6 are disposed in the intake branch pipes 45 leading to the inlet ports of the c~linders of the engine 46 or within the inlet ports. These valves are carried by a common drive shaft 54. ~he operation timings of the rotar~ valves 53 are adjusted by a mechanism substantial-ly identical to that explained before in connection with ~igure 7. ~he mechanism comprises a rotary shaft 55 adapted to rotate as a unit with the drive gear 52 disposed coaxially with the drive shaft 54 and is connected to the latter through ~0 an adjusting member 56. Helical splines 54a and 55a are formed on the opposing ends of both shafts and are of opposite hand.
The helical splines engage projections formed on the inner peripheral surface of the adjusting member 56. ~he adjusting member 56 is provided in its outer peripheral surface with an annular ret~ining groove 57 which retains one end of an adjusting lever 59 rockabl~ supported by a shaft 58. ~he î2~

other end of the lever 59 is connected to a link 60, link rod 61 and a flexible cable 62. ~he link rod 61 is connected at its right end to one end of a lever 63 which is mounted at its o-ther end for pivoting on a shaft 64. The shaft 64 is rotatably supported by the intake pipe 42. A charge-over valve 65 fixed to the other end of the shaft 64 is rockable by means of the shaft ~4 be-tween a first position where it permits the charged air to flow through an air cooler 66 and a second position where it makes the air flow through a bypass 67.
'~he right-hand end of the flexible cable 62 is connected to a lever 68 which is substantially identical to the lever 7 of the nozzle area varying mechanism of the turbine as shown in Figures 2 to 4. ~he rotor 69, which is substantially identical to rotor 5 shown in Figures 2 to L~, iS rotated by the lever so as to vary the turbine nozzle area. As in the case of the rotor 5, the ro-tor 69 is provided with a passage similar to the passage 5b shown in Figures 2 to ~ his passage is provided with a bypass 42a communicating with the intake passage 42. ~ cylinder 70 receives a piston 71 to which is connected one end of a piston rod 72 the other end of which is connected to the right-hand end of the link 60.
A spring 73 is disposed between the piston 71 and the cylinder 70 as viewed in the drawings so as to bias the piston towards the righ-t as viewed in Figure 11. An inlet formed in the right wall of the cylinder 70 as view in Figure ~2a~

11 is in communication with the inlet pipe 42 through the pipe 74. ~he chamber show~ at the right side of the ~igure, defined by the cylinder and the piston 71, receives compressed air discharge~ from a compressor 41.
The turbo-charger exhibits high performance and efficiency in the ordinary range of operation, i.e. in the area other than the hatched area in ~ig. 1. In the ordinary range of operation, therefore, sufficiently high charging pressure and air temperature are attained to provide good engine operational characteristics.
'~he invention offers advantages particularl~ in the light-load operation range, i.e~ the range as hatched in ~igure 1, as will be understood from the following description.
Usually, the operational characteristics of a turbo-charged engine are such that as the load imposed on the engine is decreased, the charging pressure and the air temperature are lowered~
~An explanation will be made hereinunder as the misfire region 1 shown in Figure 1. A pressure reduction ~0 in the inlet pipe 42 causes a counter-clockwise rotation of -the lever 59 around the axis of the shaft 5~ through the action of the piston 71, piston rod 72 and the link 60.
In consequence, the lever 63 is rotated clockwise by the link rod 61 which interconnects the lever 59 and the lever 63, so that the change-over valve 65 connected to the lever 63 is moved to the postion shown ~y full~line in Figure 11 _ 14 -~2~

thereby to make the air flow through the bypass 6'7 detouring the air cooler 66. ~hus, in contrast to the case of the heavy-load operation, the reduction of air temperature is suppressed to avoid the misfiring of the engine.
As the air pressure and temperature are further lowered within the misfiring region 2, the piston 71 is further moved to the right to rotate the lever 68 and the rotor 69.
~his relationship will be explained in more detail with reference to Figure 12. In this state of engine operation, the lever 7 has travelled about a half of the whole stroke so that the turbine nozzled area is reduced almost to a half.
~hen, as the exhaust pressure is increased, the turbine 48 (corresponding to the turbine 4 shown in Figure 4) is energised to accelerate the compressor 41 so that the discharge air pre-ssure and temperature are raised to prevent misfiring of the engine. ~he misfiring region 3 shown in Figure 1 involves the greatest factor which hinders the development of turbo-charged compression ignition engine operable at low compres-sion ratio.
~0 ~igure 12 shows the relationship between the engine spaed c~nd the polytropic lndex in the compression stroke.
~s will be understood ~rom this Figure, when the engine operates at a low speed, the temperature rise of the com-pressed air in the cylinder is not made in adiabatic manner but a considerably large amount of heat is lost in each compression stroke.

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On the other hand, the turbo-charger combined with the engine exhibits a performance as shown by a curve 1-2-~-4 in Figure 13. More specifically, the point 1 corresponds to an idle state of the engine, while the point 2 shows -the pressure ratio as obtained when the engine is operated with full load at the instant speedO
The region 3 is the region in which the compression ratio is low and the polytropic index showing the heat transfer to cylinder and o-ther parts is large so that the temperature ri.se caused by the compression is small while the turbo-charger is almost ineffective. According to the invention, however, it is possible to prevent misfiring even in this region 3~
A reduction in the charging pressure causes the spring 73 to further urge the piston 71 to the right so that the lever 7 and the rotor 5 of the turbo-charger shown in ~igure 2 are moved to the position shown by two-dot-and-dash line to drastically decrease the nozzle area, by the action of the ~le~ible cable 62 connected to the lever 59.
~0 Consequently, the exhaust pressure is raised to increase the ~low velccity o~ the gas coming out from the nozzle so that the turbine is energized to increase the power ~or driving the compr~3ssor.
However, when the engine speed is low, i.e. when the rate of supply o.~ the air to the engine i.s smalI, the compressor cannot provide the air at high pressure ratio ~08~

because of the presence of the surging region, even though the driving power produced by the gas turbine is large.
In the turbo-charger to which the invention pertains, therefore, the passage 5b in the rotor 5 is made to open at its one end to the passage 8 and its other end to the downstream side of the minimum nozzle area which is defined by one end 5a of the rotor 5 and one end 1a of the casing 1 ~he passage 8 is connected via a connecting port 9 and through the b~pass 42a to the dischrage side of the com-1Q pressor of the turbo-charger i.e. to the intake pipe 42 shown in Figure 11, so that a part of the turbine nozzle 2 is brought into communication with the inlet side.
The high exhaust pressure available at the turbine inlet 3 is changed into a kinetic energy as the exhaust gas flows through the nozzle of small area defined between one end 5a of the rotor and one end 1a of the casing 1, so that the pressure of the gas is low at the downstream side of the nozzle.
Since the passage 5b opens to the low-pressure side, ~0 it is possible to introduce the air to the exhaust side.
Referring now to Figure 13, the air o~ an amount corresponding to the di~erence between 2b and 2a is made to bypass through tha passage 5b (see Figure 2) so that the compressor 41 operates to compress the air at a rate and pressure shown by 2b averting from the surging region so that the engine suc~s the air at a pressure and rate as - ~7 -~2~ g shown by 2a.
Furthermore, according to the invention, it is possible to prevent emission of white or blue smoke with offensive smell, as well as misfiring, by raising the -temperature at the begi nni ng of the compression stroke1 as will be understood from the following description.
As sta-ted before, in this state of operation, the efficiency of the turbo-charger is low and the exhaust pressure is increased compared with the charging pressure.
In this state, the engine operates under an increased load for overcoming the negative work corresponding to the hatched area in ~igure 9. In consequence, the fuel consumption of the engine is increased and the exhaust gas temperature is also increased ..
With this invention, it is possible to raise the air temperature at the be~inning of the compression stroke, by m~ki nE an efficient use of this hot exhaust gas. Namely, in the engine of the invention, the lever 59 shown in ~igure 11 is rotated counter-clockwise as explained before so that the adjusting member 56 engaging one end of this lever is moved to the left. In conse~uence, the timing of closing of the rotary valve is advanced as shown in ~igure 9.
Concurrently with the closing of the inlet passage by the rotary valve, the auxiliary exhaust cam 37 shown in ~igure 10 is opened at a moment 1 shown in Figure 9 so that the exhaust gas of high pressure and temperature is made to ~2~g9g flow back into the cylinder.
~ hus, from the moment 1 to the moment 2 shown in ~igure 9, the air in the cylinder is pressurised and heated by the exhaust gas introduced into the cylinder so that a high temperature is established within the cylinder at the begi nni n@
of the compression stroke. ~he compression ignition engine, therefore, can operate even under reduced compression ratio, without suffering from misfiring and emission of white or blue smoke with offensive smell.
It will be clear to those skilled in the art that the same advantage can also be obtained by shifting the timing of closing of the intake valve to a point (c) shown in Figure 9 by a suitable known measure.
Although the invention has been described through specific terms, it is to be noted here that the described embodiment is not exclusive and various changes and modifi-cations may be imparted thereto without departing from the scope o~ the invention which is defined b~ the appended claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A turbo-charged compression ignition engine comprising:
a turbo-charger for supercharging said engine, control means for controlling the timing of closing of an inlet passage of said engine, opening means for opening an exhaust valve of said engine at a point near bottom dead centre in the suction stroke, means for varying the area of a nozzle in the turbine of said turbo-charger and said last mentioned means defining a passage openable to the downstream side of said last mentioned means, and an inlet pipe communicating with said last mentioned passage.

2. A turbo-charged compression ignition engine according to claim 1 in which the control means comprises a first shaft drivable by the engine and a second shaft connected to a rotary valve arranged to open or close said inlet passage, the first shaft being arranged to rotate the second shaft through an adjusting member which enables the relative angular position of said shafts to be varied.

3. A turbo-charged compression ignition engine according to claim 2 in which the adjusting member engages splined portions of the first and second shafts, said splined portions being of opposite hand and the adjusting member being tubular and having projections thereon which engage the splined portions so that axial movement of the adjust-ing member will turn one shaft relative to the other.

4. A turbo-charged compression ignition engine according to claim 3 in which axial movement of the adjusting member is effected by pivoting movement of a lever, said pivoting movement being controlled in response to pressure in the inlet passage downstream of the compressor of the turbo charger.

5. A turbo-charged compression ignition engine according to claim 4 in which the pivoting movement of the lever operates valve means in the inlet passage to cause air in the inlet passage to pass through or by-pass cooling means.

6. A turbo-charged compression ignition engine according to claim 4 in which the pivoting movement of the lever operates said means for varying the area of the nozzle in the turbine.

7. A turbo-charged compression ignition engine according to claim 1 in which the means for varying the area of the nozzle in the turbine of said turbo-charger comprises a rotor which can be rotated to reduce or increase the area of the nozzle.

8. A turbo-charged compression ignition engine according to claim 7 in which said passage is formed in the rotor and opens to the downstream side of the rotor when the rotor occupies a position in which it reduces the area of the nozzle.

9. A turbo-charged compression ignition engine according to claim 1 in which the opening means comprising a cam having a main cam section for opening the exhaust valve during the normal exhaust stroke and an auxiliary cam section which effects opening of the exhaust valve near bottom dead centre in the suction stroke.

10. An internal combustion engine comprising a turbo-charger for supercharging said engine, control means for controlling the timing of closing of an inlet passage of said engine, opening means for opening an exhaust valve of said engine at a point near bottom dead centre in the suction stroke, means for varying the area of a nozzle in the turbine of said turbo-charger and said last mentioned means defining a passage openable to the downstream side of said last mentioned means, and an inlet pipe communicating with said last mentioned passage.

11. A turbo-charged compression ignition engine according to claim 5 in which the pivoting movement of the lever operates said means for varying the area of the nozzle in the turbine.