"Piston combustion engine with adjustable valve opening time"
The invention relates to piston combustion
<EMI ID = 1.1>
valve against spring action is opened by the action of a rocker lever, which is supported simultaneously at least during the phase in which the valve is open, by two cams mounted on different cam rotation shafts, viz. an opening cam and a closing cam, which are joint action to fully determine valve movement, the valve opening time can be controlled by varying the phase difference between the two camshafts and the degree of filling of the cylinders to a significant degree. can be controlled by the opening time of the inlet <EMI ID = 2.1> This device is described in applicants earlier patent application no. 201.558 (Brussels, July 28
1980). A low degree of filling, with low engine load, is achieved by a short opening time of the inlet valves.
Both the opening cams and the closing cams impose an acceleration directed in the closing sentence on the inlet valves for some time. This "overlap" does not occur at the maximum valve opening time. If the accelerations of the valve in the closing clause imposed separately by each of the cams are approximately constant and equal over a considerable angle - which is preferably the case, because the valve spring force required at a given maximum speed and a maximum valve opening time is then minimal. - for a short opening period, the acceleration imposed on the valve in the closing clause is therefore for some time twice the acceleration imposed on the valve by one cam separately in the closing clause.
As a result, with the damper speed remaining the same, the valve opening time decreases from the maximum at a given moment - namely, when the intended overlap will take place - the acceleration imposed on the valve in the closing sentence doubles. This means that the valve springs and any rocker lever and / or push rod springs, which after all
must exert the force required to generate the gear imposed by the cams in the closing sentence,
should be twice as powerful as with a corresponding engine with unchanging valve opening time, to avoid temporary release of the toggle levers from the cams. This measure would lead to doubled cam bearing forces as well as the need for wider cams and cam contact surfaces to prevent faster wear and to double the friction losses. Another possibility would be to limit the engine speed with an unchanged valve spring to a value equal to that of the corresponding engine with unchanging valve opening time multiply- <EMI ID = 3.1>
gears are cut in half. However, this would significantly reduce the maximum power of the engine. Clearly, neither is theoretical
<EMI ID = 4.1>
The object of the invention is now to achieve a piston combustion
gear motor with a valve actuator of the type referred to in the preamble, wherein, despite the aforementioned phenomenon, that at constant engine speed, the acceleration imposed on valves in the closing clause doubles with shorter opening times, nor the valve and other
<EMI ID = 5.1>. The present invention is characterized in that control means are provided which ensure a long valve opening time at high engine speeds, such that the sum of the accelerations of a valve in the clasp determined separately by each of the two cams is not at any time. is significantly greater than the highest at any time during the opening period of the <EMI ID = 6.1>
that the degree of filling of the cylinders is set to less than maximum at said high engine speeds by a throttle valve placed in the supply line for air or fuel-air mixture, which is not substantially active below those high speeds.
The invention will be explained below with reference to the figures.
Fig. 1 shows, partly in section, partly in view, an example of a valve operating device, in which application of the measures according to the invention is important. Fig. 2 shows associated valve lift curves concerning the inlet valves obtained with advantageous embodiments of the opening and closing cams.
Pig. 2A-2D are schematic graphical representations of the valve lift curves of FIG. 2 occurring gears.
<EMI ID = 7.1>
Running valve light curves for the exhaust valves, obtained just-considered advantageous versions of the opening and closing cams.
Fig. 3A-3D are schematic graphical representations of the valve lift curves of FIG. 3 occurring gears. Fig. 4 is an outline of the control means of the present invention.
The valve actuator of FIG. 1, which has also already been described in applicants' aforementioned older invention patent application, is shown in a position,
<EMI ID = 8.1>
will open correctly, while the exhaust valve (valve spring housing 6 'shown) is not yet closed. In both cases, the valve opening time is set to the maximum value. The inlet valve is still held closed by the valve spring 2. The rocker lever 3 pivots about the pin 4, which has flattenings 7 on either side, which are guided in slots 5 formed in the valve spring housing 6. The corresponding parts belonging to
<EMI ID = 9.1>
sense of rotation is indicated by arrows. The periphery of the inlet valve closing cam 10 comprises a first arc of the circle 14 and a second arc of the arc 16, the centers of which coincide with the axis of rotation of the camshaft 12, as well as a run-off edge 15 and an inlet flange 17. The opening of the inlet valve 11 comprises a first circular arc part 18 and a second circular arc part 20, the centers of which coincide with the axis of rotation of the cam shaft 13,
<EMI ID = 10.1>
The starting points of the said peripheral parts are marked with transverse lines.
In the position of the device shown, the
<EMI ID = 11.1>
closing cam disk 10 and also just against the circular arc part 20 of the opening cam disk 11. Due to the prior action of the run-up flank 17, the adjustment resting in the pin 4 is
<EMI ID = 12.1>
brought with the end 26 of the inlet valve stem 1. When the camshafts rotate further from this position in the arrow direction, the inlet valve is opened by the action of the run-up flank 19. It starts to be connected as soon as the run-off edge 15 of the cam disc 10 comes into contact with the rocker lever 3
<EMI ID = 13.1>
slightly early, when the circle arc part 16 comes into contact with the rocker lever 3. Only after that
<EMI ID = 14.1>
rocker lever 3, whereby the adjusting screw 25 moves away from the end 26 of the spring under the influence of the spring 9
<EMI ID = 15.1>
In the relative position of the camshafts shown
12, 13, the opening time of the inlet valve is the maximum. The
<EMI ID = 16.1>
in the arrow sentence. As a result, the run-off edge 15 of the cam disk 10 will come into contact with the rocker lever 3 earlier, so that the valve closes earlier, but continues to open at the same time. The phase of opening is set later by adjusting the camshaft 13 backwards in phase relative to the crankshaft.
<EMI ID = 17.1> <EMI ID = 18.1>
discs always make good, evenly loaded line contact, the free end of each rocker lever can be equipped with a separate one, so that one can move in the longitudinal direction of the
<EMI ID = 19.1>
is in contact with a cam disc.
Such a self-adjusting contact piece guarantees the intended evenly loaded line contact between cam discs and rocker lever surfaces. The latter surfaces do not need to be flat, as shown, but may also be concave or convex, if desired, in particular as cylindrical surfaces, the descriptions of which run parallel to the camshafts.
In the diagram of FIG. 2, which shows the relationship
gives between valve lift (ordinate) and crankshaft positions
<EMI ID = 20.1>
10 and 11 on the valve positions shown separately (solid lines), as well as the resulting valve lift curves
<EMI ID = 21.1>
<EMI ID = 22.1>
<EMI ID = 23.1>
<EMI ID = 24.1>
the effect of the circular arc part 14 and the bleed
flank 15 of the cam disc 10, in the position according to fig. 1, so at maximum opening time. With PbQb - PfQf, the effect of the trailing edge 15 is shown in different phase positions of
<EMI ID = 25.1>
valve lift curves are marked with a - f.
The curve OM, which is the effect of the leading edge 19
<EMI ID = 26.1>
OM 'the valve is accelerated in the opening sentence with the acceleration as constant as possible, against the action of valve spring 2. The valve is delayed in the opening sentence over M'M "and M" M; in fact by the action of the valve springs 2. Size, direction and duration in crank degrees of these gears <EMI ID = 27.1>
The effect of the run-off edge 15, represented by the curves PaQa - PfQf, is essentially symmetrical with respect to the effect of the run-up edge 19. Considering the curve PaQa, which corresponds to the phase position for maximum valve opening time, three different sections are also missing. -
<EMI ID = 28.1>
<EMI ID = 29.1>
the leading edge 19. About P "Qa the valve in the closing sentence is decelerated until it is closed. Size, direction and duration in crank degrees of these gears are shown in Figures 2A 2D by the surfaces hatched from top left to bottom right. Is a surface double shaded, then
<EMI ID = 30.1>
the running edge 19 and the run-off edge 15 for that part are opposite and thus cancel each other.
Curves e and f are partly in the negative
tive area of the graph. As for the left negative portion, this means that the end of the set screw 25, which was initially brought close to the end 26 of the valve stem, first moves slightly away from that end before approaching again and opening the valve , which then takes place directly at a certain speed. The valve naturally closes at the moment that the right-hand part of the curve e, resp. f, the abscissa cuts. This also takes place at a certain speed, which in general will not be more reddish than is normally already the case as a result of the so-called "valve clearance" to be maintained. Moreover, this bursting opening and closing, as will be seen hereinafter, can only occur at relatively low speeds.
The maximum valve opening time (in crank degrees) is represented by the line segment OA. In a typical practical case this corresponds to 294 [deg.] And the optimum value is at full load and an engine speed of 6500 rpm. At full load, but lower engine speeds, the optimum valve opening time is shorter, achieved by simultaneously and in approximately the same time the closing time earlier and the opening time later
<EMI ID = 31.1>
reset cam cam 13 relative to the crankshaft
(in Fig. 1 against the arrow) and the cam cam 12 forward
<EMI ID = 32.1>
rpm or less, the optimum valve opening time for the engine under consideration is approx. 2240 (OC in Fig. 2, with associated valve lift curve c). In the control area between OA and OC applies to
<EMI ID = 33.1>
(I). (nx is the speed). Now in FIG. 2A, it can be seen that the beginning of the acceleration imposed by the closing cam in the closing clause coincides with the end of the acceleration applied by the opening cam in the closing clause. However, once the opening time is set to a value lower than the maximum, these accelerations will partially coincide. To avoid that the sum of these accelerations would be greater than the major part of each of the cams
<EMI ID = 34.1>
resp. PtP ") - in which case the force of the valve springs on this
sum value should be tuned - is the acceleration imposed by each of the cams separately over a limited area (M "M, respectively PaP") equal to half the acceleration over the remaining areas (M "M, respectively P) "P"). The intended sum value only now exceeds the intended
<EMI ID = 35.1>
<EMI ID = 36.1> <EMI ID = 37.1>
of the matter below the maximum permissible value.
The problem mentioned in the introduction therefore does not arise with the selected cam properties, if the valve opening duration is only set between the values OA and OC depending on the speed. However, this problem arises when the degree of filling of the cylinders must also be controlled by means of the valve opening time, because it must then be possible to reduce the valve opening time to any possible low value at any time, including at the maximum speed. Situations, as shown in Figures 2C and 2D - corresponding to resp. the curves
<EMI ID = 38.1>
occur. Before, with reference to FIG. 4, to describe the measures according to the invention for the elimination of this objection, the operation of the control for the
<EMI ID = 39.1>
and 2 - 2D.
The outlet valve (not shown) is moved in a similar manner as the inlet valve by the rocker lever 3 ', which is moved by the spring 9 against the opening cam 11
(dishes on cam 13) and the locking cam 10 '(fixed on cam 12) is kept pressed. In comparison with the control of the inlet valve, the opening and closing cam disk are exchanged with respect to the valve shaft center line, of course because all
<EMI ID = 40.1>
<EMI ID = 41.1>
the opening cam disk 11 'and the closing cam disk 10' are determined such that, despite the large phase shift of the camshaft
12 relative to the camshaft 13, which may occur when controlling the inlet valve opening duration, only a limited variation of the outlet valve opening duration occurs. This variation is fully accomplished during the first stage of reducing the inlet valve opening time, in a proportion
<EMI ID = 42.1>
opening time is accompanied by one degree reduction of the exhaust valve opening time. This fulfills the wish at lower speeds but maximum torque only smaller
<EMI ID = 43.1>
third torque is achieved by further reducing the inlet valve opening time, however, the outlet valve opening time may not be further reduced. To realize this, the run-up flank 30 of the opening cam 11 'does not merge directly into a circular arc-shaped portion, the center of which coincides with the camshaft centerline, as with the inlet valve opening 10, but is followed first by a run-off flank 31. into a circular arc part 32,
<EMI ID = 44.1>
is followed by the circular arc portion 34. Both circular arc portions 32 and 34 are concentric with the camshaft centerline; this is essential only with regard to the circular arc portion 32.
The closing cam 10 'comprises the concentric circular arc parts 35 and 36 with the run-up flank 37 and the run-off flank 38 between them. The difference between the radii of the parts 35 and 36 is such that the closing cam 10' can only close the outlet valve and keep it closed if the opening cam
<EMI ID = 45.1>
axis that is equal to or less than the radius of the circular arc portion 32.
<EMI ID = 46.1> with continuous lines the influences of the opening cam 11 '(positive with respect to the abscissa OL) and of the <EMI ID = 47.1>
Therefore, as well as the resulting valve lift curves (broken lines), at different phase positions of the locking cam disc relative to the opening cam disk. The control range of the closing time is limited to the area where the end pu of the run-off edge 38 of the closing cam falls to the right of the end-point of the first run-off edge 31 of the opening cam (i.e. in the area of the circular arc part 32). Also, the effect of the circular arc parts 32 and 36 is chosen to be the same, so that, except for the required valve joint, there will be no jolting of the outlet valve.
The curve OM, representing the effect of the ramp edge 30, consists of two different parts, OM 'and M'M. Over OM 'the outlet valve in the opening sentence becomes ee;
accelerated as constant as possible, against the work,
<EMI ID = 48.1>
delayed, in fact by the action of the valve spring. Size direction and duration in crank degrees of these gears
<EMI ID = 49.1>
to top-right shaded surfaces.
<EMI ID = 50.1>
PdQd, depending on the phase position of the camshaft 12
<EMI ID = 51.1>
P "Qa. About PaP 'and P'P" the valve in the closing sentence is accelerated <EMI ID = 52.1>
slow until the valve is closed. Size, direction and duration in crank degrees of these gears are shown in Figures 3A - 3D by the hatched areas from top left to bottom right. If a surface is double shaded, this means that the accelerations imposed by the
<EMI ID = 53.1>
<EMI ID = 54.1>
<EMI ID = 55.1>
As can be seen from Figures 3A-3C, the sum of this is also shown here
<EMI ID = 56.1>
then becomes OA - y. The problem mentioned in the introduction does not therefore arise with the outlet valve either. as long as only the angles of front opening and closing are dependent on
<EMI ID = 57.1>
is controlled. The solution to this problem provided by the invention will now be described by <EMI ID = 58.1>
<EMI ID = 59.1>
(13, 12 respectively in Fig. 1) are driven by planetary gear mechanisms coaxial with the respective camshafts
50, resp. 50 '. These are only very schematically represented by broken lines, which only indicate the pitch circles of the gears of the mechanisms. Therefore, these mechanisms are not in themselves part of the invention;
<EMI ID = 60.1>
be replaced by any other suitable mechanism, which allows the phase angle of the camshafts relative to the crank
<EMI ID = 61.1>
timing wheel mechanisms are driven via the chain or timing belt 52 by the wheel 53, which is fixed to the crankshaft or is driven by the crankshaft. The sun wheels 54, 54 'are held still, but their angular positions are variable in order to control the phase angles of the opening and closing camshafts, which are fixedly connected to the carriers 55, 55' of the planet wheels 56, respectively. 56 '. The phase angle of the locking camshaft is controlled by the rack 57, which extends over the entire right side edge of the plate 58 and is thereby engaged by the segment 59 mounted on the gear 54. Moving the plate 58 downwardly sets the locking camshaft in phase back with respect to the crankshaft and thus exits the closing time of the inlet valves and increases the valve opening time. Back to top
<EMI ID = 62.1>
The full control range includes a phase shift of the camshafts relative to each other of approximately 1800. Of this, 70 [deg.] Is used to control the angles of the front opening and closing at full load, depending on the
<EMI ID = 63.1>
the maximum speed. This implies that the phase of the opening camshaft must only be included during the last 35 [deg.] Of the adjustment range of the locking camshaft, in a sense opposite to the closing camshaft. To this end, the plate 58 has a
<EMI ID = 64.1>
the torque -in applied to the opening camshaft. The opposite movement of the gear wheel 54 is limited by the fact that the
<EMI ID = 65.1>
block connected cam 63.
The plate 58 is hingedly connected to the lever
64, which in turn is hingedly connected to the rod 65 and to the piston rod 66 of the piston 67 in the cylinder
68. Both rod 65 and piston rod 66 are movable up and down. Both movements independently influence the position of the plate 58, which is determined by both items. The rod 65 is hingedly connected to the lever 69 and is pushed upwards by the spring 70. One end of the lever 69 is connected to a vertically movable member 71, the position of which is determined by the accelerator pedal (not shown); the other end is hingedly connected to the arm 72, which in turn is hingedly connected to the lever 73. It is connected to the throttle valve 74, which can largely close the conduit 75 for air or fuel-air mixture fed to the cylinders, and can pivot about the shaft 76 for this purpose. The hinge pin 77 fits into the slot 78 and thereby prevents lateral movements of the lever 69.
Due to the action of the spring 70, the throttle valve 74 will usually
<EMI ID = 66.1>
With "accelerate" the left end of the boom 69 is moved downwards, against the action of the
<EMI ID = 67.1>
<EMI ID = 68.1>
65 against the stop 80. When "release gas" the organ moves
71 up to the stop 79 adjustable for controlling the idle speed. The position of the piston 67 is set in an unspecified manner such that the
<EMI ID = 69.1>
and resetting on the one hand and the engine speed on the other hand. At a low speed, the piston 67 is in the lowest position. If "full throttle" is now given, the plate 58 is moved downwards until the protrusion 60 just does not take the pin 61 with it. As the speed increases, the piston 67 will move upward and thereby move the plate 5t further downward, so that the angles of the front opening and after closing increase in the desired manner. It is noted that it is of no importance for the invention in which way the member, here shown by way of example as a piston rod 66, is set in the desired speed-dependent positions.
Now is the task, for which the invention is the solution
<EMI ID = 70.1>
the maximum speed of the valve opening duration must be at least equal to OA - 2y (Figures 2 and 3) and at each speed
<EMI ID = 71.1>
<EMI ID = 72.1>
hinges about fixed point 82 and on piston rod 66
mating slider 83. The latter includes a movable on
the piston rod 66 fits cylindrical portion 84 with two slots 85 closed at the ends, into which the ends of a pin 86 inserted through the piston rod 66 and secured therein fit. The slider 83 is moved relative to the piston
<EMI ID = 73.1>
The left end of the lever 81 is pushed upwards by the sliding piece 83 from a certain position of the piston rod 66, i.e. from a certain engine speed. The right-hand end of the lever 81 now pushes the rod 65 downwards, irrespective of the position of the accelerator pedal. The size ratio
<EMI ID = 74.1>
in any case rod 65 touches stop 80 just before it
<EMI ID = 75.1>
then comes into a position corresponding to "full throttle". However, the accelerator pedal and thus the member 71 are not already there
in the "full throttle" position, when the rod 65 is lowered the right end of the lever will also
69 will move downward and thereby bring the throttle valve 74 to a position in which it partially passes the line 75 for supplying air or fuel-air mixture to the cylinders <EMI ID = 76.1>
<EMI ID = 77.1>
maximum speed, the accelerator pedal only works on the throttle valve 74. This protection works both when the engine speed exceeds this value when the accelerator is not at full throttle, and when at a speed above the specified value from the "full throttle" position suddenly. gas is taken back. At speeds above the stated value, the piston rod 66 can continue its upward movement unobstructed because the spring 86 is then depressed.
The device, as shown in Fig. 4 and described above, is only an outline, only intended to clarify the operation of the control according to the invention as well as possible. It will therefore be clear that numerous variants are conceivable within the scope of the invention. Only one is currently mentioned. In practice, the portion of the illustrated mechanism, which includes the lever 81 and the slider 83, will advantageously be replaced by a (second) vertically on
the rod 65 acting hydraulic or pneumatic cylinder, or by a solenoid, which is actuated - i.e. the rod 65 presses against the stop 80 - as soon as the engine speed-
<EMI ID = 78.1>
is approaching. The way in which this is done is not essential. For example, upon exceeding an appropriately selected position (about halfway through the total stroke of this member), the member 66 may actuate a hydraulic, pneumatic, or electrical relay that directs the supply of fluid, compressed air, or electrical current to said hydraulic or pneumatic cylinder or the solenoid turns on and switches off this energy flow when it falls below the same or slightly lower position, so that the position of the member 65
<EMI ID = 79.1>
but this cylinder or solenoid acting on rod 65 can also be switched on and off in another way on the basis of the engine speed.