Cars and Tuning

The distribution system is the set of elements that regulate the opening and closing of valves at the opportune moment and as well the entrance of the mixture, (fresh gases) and the exit of residual gases of the cylinders, at the moment adapted after taking place the explosion.

Of the moment in which the opening is made and closes of the admission valves and escapes, thus it will be the correct operation of the motor (advance and delay to the opening and close of the corresponding valves).
Different types from compression chambers
The compression chambers are classified by their geometric form. The form of the compression chambers is fundamental in the yield and the engine power.
The form of the camera comes imposed by the disposition and size, as much of the spark plugs as of the valves.

Next one imagines some types of used compression chamber more.
Cylindrical camera
Very it is used, by his simplicity in the design, and the good operation produced by the proximity of the spark to the point of maximum advantage. They are economic.

Camera of bathtub and in wedge formation
They make generally with valves in the butt and the spark plug is located laterally. They have the advantage of which the route of the spark is very short and reduces the excess of turbulence of the gas. It produces, to the entrance of gases, a blowing on the head of the piston that reduces the mincemeat of connecting rods.
Hemisférica camera
By his symmetry, it shortens the distance that must cross the flame from the spark plug to the head of the piston, obtaining itself a good combustion.
She is next to the ideal form.
It allows to mount valves of great dimensions as well as, a better filling of the cylinders.

Elements of the distribution system
The main elements of the distribution are: camshaft, gear of control, and the valves with its wharves.
They are classified, in agreement with its function in:
Inner elements
or Valve of admission
or Valves of escape
Elements of exteriors
or Camshaft.
or Elements of control.
or Taqués.
or Balance beams
Inner elements
These elements are the valves of admission and the valves of escape.
Valves
They are the ones in charge to open or to close the orifices of mixture entrance or exit of gases burned in the cylinders.

In each valve, two parts are distinguished: head and tail. The head, that has mushroom form, is the one that acts like true valve, because she is the one that closes or opens the admission orifices or escapes. The tail or piston rod, (prolongation of the head) is the one that, sliding within a guide, will receive in its opposite end at the top the impulse to open the valve.
The valves cool off by it guides, mainly, and by the head.
The valves that are deteriorated more are those of escape, due to the high temperatures that they have to support 1000º C.

Some valves, mainly those of escape, cool off inner with sodium.
It must have a good fatigue strenght and to the wearing down (shocks).
It must also present/display a good thermal conductivity (the heat expands the valves) and good properties of sliding.
The head or tulipa of admission is of greater diameter than the one of escape, to facilitate the filling.

Wharves (and)
The valves stay closed on their seats by the action of means (soft).
The wharves must have the sufficient force and elasticity to avoid bounces and to maintain the contact with the control elements.
or It must assure the mission the valve and maintain it flat on his seat.
or the number of wharves can be simple or double.

Guides of valve (and)
Due to the high speeds, the distribution system is often driven in short periods of time. In order to avoid a premature wearing down of the orifices practiced in the butt by where the piston rods of the valves move and since light alloys in the manufacture of the butt are used, they equip these orifices with sockets of guidance G, called guides of valve, resistant to the wearing down and they mount, generally, to pressure in the butt.
The guides allow that the valve is centered and guided well.

The valve guide must allow a good sliding of the tail of the valve, without friction.
If too much comfort between the guide and the body of an admission valve existed, would enter oil the compression chamber, due to the suction of the piston, producing an excess of fine coal in this camera, and if outside in an escape valve, the oil is expelled by the exhaust pipe.
Seats of valves
They are detachable earrings placed to pressure on the butt to avoid the deterioration of this one, by the contact with a material one it last like the one of the valve, his golpeteo, and to the corrosion due to burned gases.
The assembly of the seats becomes to pressure by means of an adjustment (cold-heat), and when they are deteriorated they can replace.

Outer elements
They are the set of mechanisms that serve as control between the crank and the valves. These elements are: camshaft, elements of control, pushers or taqués and balance beams. According to the used system, the motors sometimes lack some of these elements.
Camshaft
It is an axis that controls the opening of the valves and allows its closing. It has distributed throughout same a series of levies, in equal number to the number of valves that the motor has.

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The camshaft or tree of the distribution, receives the movement of the crank through a system of gears. The speed of turn of the camshaft has to be smaller, concretely half that the one of the crank, so that by each two returns to the crank (complete cycle) the camshaft gives a single return. Thus, the gear of the camshaft, has a number of teeth doubles that the one of the crank.
The camshaft takes another gear, that serves to make work by the inferior part to the lubrication pump, and by the part superior to the axis of the distributor. In addition it has an eccentric for the fuel pump in many cases.
According to the types of motors and their uses, the levies have different forms and positionings.
In the 0 one imagines two types of camshaft:
or It details B: with gear to drive the pump of oil and distributor.
or Detail A: with eccentric for the fuel pump.
In the 1, one imagines the profile of the levy and the corresponding phases that are made during their turn.

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Elements of control
The control system is constituted by a pinion of the crank, placed in the end opposed to the motor steering wheel and by another pinion that the camshaft in one of its ends takes, that turn shared in common with that one.
In the diesel engines the gear takes advantage of control to give movement, generally, to the inyectora pump.
The connection between both pinions can be made by some of the three following systems:
Transmission by gears
When the crank and the camshaft are very separated, so that it is not possible to unite them of direct form, is possible to be used a consisting of mechanism a series of gears in constant taking to each other to transmit the movement.

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The teeth of the pinions can be straight, these are noisy and of short duration or in oil angle helical bathed in a case or cover of distribution, being these of a greater duration.
In the case of two gears, the crank and the camshaft turn in opposite sense and, if they are three, they turn the crank and camshaft in the same sense.

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Transmission by chain
Just as in the previous case, this method is used when the crank and the camshaft very are distanced. Here both gears by means of a chain connect.
So that the adjustment of the chain is always the correct one, it has a consisting of tension a pinion or a small fiber skid, located to half of the route and connected generally to a wharf, that maintains the tension required.
In this system one diminishes the wearing down and the noises when not being in contact with the enemy the teeth. He is little noisy.

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Transmission by dentated strap
The principle is the same one that the one of the control by chain, only that in this case is used an indented strap of neopreno that offers like advantage a quieter gear, smaller weight and a reduced cost more, which makes its substitution economic.
It is the used system more at the moment, although the life of the dentated strap is much smaller than the one of the other systems. If this one were broken, the motor would undergo great consequences. These pinions are outside the motor, reason why it is a system that does not need lubrication, but the verification of the tightened state and of the strap.
In the figure, it indicates the screws for the tightened one of the strap.

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Taqués
They are elements that interpose between the levy and the element that these drive. Its mission is to increase to the faying surface between these elements and the levy. Taqués, has to be very hard to support the push of the levies and to overcome the resistance of the wharves of the valves.
In order to extend the life utility of taqués, it is positioned to them of such way, that during its operation they make a tumbling on its geometric axis.
Taqués always is lubricated by their proximity the camshaft.
The lightness is a quality necessary to reduce the inertia effects.

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Taqués hydraulic
Taqués hydraulic engineers work in an oil bath and are supplied of lubricant of the circuit of the lubrication system of the motor.
The pushers or taqués adjust automatically to adapt to the variations in the length of the piston rod of the valves to different temperatures. They lack setting. The most important advantages of this system are their quiet operation and its great reliability.

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Dozer rod
They do not exist in the motors that take camshaft in head.
The rods go placed between the balance beams and taqués.
They have the mission to transmit to the balance beams the movement originated by the levies.
The dozer rods:
or They are massive or hollow, in steel or light alloy.
or Their dimensions are reduced to the maximum so that they have a weak inertia at the same time and a good resistance to the deformations.
or the side of I marked has spherical form.
or the side of the balance beam has a concave form that allows to receive the setting screw.

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Balance beams (9 and 0)
They are handles that oscillate around an axis (axis of balance beams), that is placed between the valves and the rods of the balance beams (or between the valves and the levies, in the case of a camshaft in head).
The balance beams are of steel. They oscillate around a hollow axis in whose interior oil to pressure circulates. This axis goes drilled to allow the lubrication of the balance beam.
The mission of the balance beams is the one to send to the opening and the closing of the valve.
Two types of balance beams are distinguished:
or oscillating Balance beams.
or Balance beams tilted.
Oscillating balance beams
They use the motors with camshaft in head. The spin axis happens through an end of the balance beam. It is also known him with the name “semibalancín”. It receives the direct movement of the camshaft and it transmits it to the piston rod of the valve through his free end.

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Tilted balance beams
They use the motors with lateral camshaft.
The valves go in head. The spin axis happens through the center of the balance beam. One of its ends receives the movement of the dozer rod and it transmits it to the piston rod of the valve by the other end.

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Systems of distribution
They are classified according to the location of the camshaft:
or Camshaft in lateral block or.
or Camshaft in the butt or head.
The valves generally, go placed in the butt. In some motors lateral valves are used (system SV), but is in disuse.
Camshaft in the block (system OHV)
It is a system very used in medium diesel engines of and great piston displacements. In the tourism, due to the revolutions that reach these motors every time less are used. This is as a result of the created forces of inertia in the elements that have alternative movements.
Operation
The crank gives movement him to the camshaft and this one drives I marked, in which the rod is supported. To the driven being the rod rises and drives the tail of the balance beam (tilted) that when turning on the axis of balance beams causes that this one acts on the tail of the valve, winning the action of the wharf, opening the corresponding orifice. When disappearing the action of the levy, the wharf recovers its initial length and the valve closes the orifice, when allowing it the levy.

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Camshaft in the butt (OHC)
It is the used system more. The drive of the valves is or direct or through some organ. This causes that they use the motors that reach a high number of revolutions, although the control is more delicate.
The drive can be:
or Direct.
or Indirect.
System OHC of direct drive
It is a system that takes few elements. One is used for revolutionized motors. The transmission between the crank and camshaft usually one becomes through indented strap of neopreno. It uses hemisférica compression chamber type, being used very frequently three or four valves by cylinder. These systems present/display the problem of which the butt is of difficult design.
It can take one or two camshafts in the butt, call system DOHC, if they are two camshafts.

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System OHC of indirect drive
This system practically is just as the previous one, with the only difference of which the camshaft, drives a semibalance beam, placed between the levy and the tail of the valve.
The operation is very similar to the system of direct drive.
When turning the levy, pushes the semibalance beam, that makes contact with enemy with the tail of the valve, producing the opening of this one.

Settings
As a result of the temperature in the elements of the distribution, these elements dilate during their operation reason why it is necessary to equip to them with a certain game in cold (separation between pieces that allows its expansion).
Although the main reason to give this game (comfort of taqués) is that they determine the levels of the distribution, is important not to forget the effects the expansion in the valve.
This comfort with the operation, tends to be reduced or to be increased (depending on the used system), reason why every certain time it is necessary to return to fit them then otherwise the valves they will not close nor they will open correctly. This comfort comes determined by the manufacturer and following its instructions.
This verification is necessary to make it when the valve completely is closed. In a system OHV the game of taqués is moderate between the piston rod of the valve and the end of the balance beam.
In the system of distribution OHC of direct drive, the setting of taqués is done placing in the interior of I marked, more or less steel laminae.
In the system of distribution OHC of indirect drive the setting of taqués is done acting on the screws of adjustment and lock nut. The setting will always take control of the motor in cold and as it were said previously, its value, depends on the manufacturer.
A great game of taqués causes that, the valve does not open the corresponding orifice absolutely, with which the gases will not happen in all their magnitude. A small game of taqués causes that the valve is more open time does not even get to close if does not exist comfort, not being able to obtain a good compression and being able to fuse the valve in the part of its head (left without a leader valve) being given rise to take place great failures in the interior of the cylinder and the butt.