5.3.1. Constructive osobennostia

Fig. 3.11. Details of the mechanism of gas distribution and TNVD drive: I \CD20 engine; II \CD20E engine; 1 — a pulley of a bent shaft; 2 — the lower part of a forward cover of the drive of the mechanism of gas distribution; 3 — laying; 4 — the pump of cooling liquid; 5 — the right arm of an engine mount; 6 — the cogged pulley of a bent shaft; 7 — the top part of a forward cover of the drive of the mechanism of gas distribution; 8 — a gear belt of the drive of the camshaft; 9 — the directing roller; 10 — a tension roller; 11 — a spring; 12 — a flange; 13 — the cogged pulley of the camshaft; 14 — a back cover of the drive of the mechanism of gas distribution; 15 — an epiploon; 16 — a spline; 17 — the camshaft; 18 — a hydraulic pusher; 19 — crackers; 20 — a plate of a spring; 21 — an external spring of the valve; 22 — an internal spring of the valve; 23 — basic washers of springs; 24 — a maslootrazhatelny cap; 25 — the valve; 26 — an internal protective cover of a gear belt of the TNVD drive; 27 — the cogged pulley of the TNVD drive; 28 — a gear belt of the TNVD drive; 29 — an external protective cover of a gear belt of the TNVD drive; 30 — the vacuum pump

In the engine the valvate distributive mechanism with hydraulic pushers and the top arrangement of the camshaft set in motion by a gear belt from a pulley of a bent shaft is used. The tension of a driving belt is regulated by the semi-automatic roller device. Details of the mechanism are represented in fig. 3.11.

Fig. 3.12. Details of a head of the block of cylinders: 1 — a stopper of an oil-filling mouth; 2 — a cover of a head of cylinders; 3 — laying of a cover of a head of the block of cylinders; 4 — covers of bearings of the camshaft; 5 — a head of the block of cylinders; 6 — laying of a head of the block of cylinders; 7 — the vortex camera; 8 — saddles of valves

The head of the block of cylinders (fig. 3.12) is cast from aluminum alloy. The saddles of valves directing plugs of valves and vortex Recardo Comet V cameras are pressed in a head. Nominal height of a head of the block of cylinders of 116,6 — 117,0 mm. Maximum not planeness of a surface of interface of a head to the block of cylinders of 0,1 mm. Diameter of openings under bearings of the camshaft of 30,000 — 30,021 mm. Diameter of openings under guides of valves: nominal 10,075 mm, repair 11,185 — 11,196 mm.

The directing plugs of valves are manufactured of cast iron and pressed from above in a head of the block of cylinders. Outer diameter of plugs: nominal 11,023 — 11,034 mm, repair 11,223 — 11,234 mm. Internal diameter is 7,000 — 7,015 mm.

Saddles of valves are made of steel and pressed in a head of the block of cylinders. Parameters of facets of saddles of valves are specified in tab. 3.6.

Parameter	Saddle of the inlet valve	Saddle of the final valve
Width of a working facet, mm	1,91	1,71
Corner of a working facet	90 °	90 °
Angle of grinding of the lower facet	70 °	0 °
Angle of grinding of the top facet	0 °	0 °

Each inlet and final valve has two (external and internal) springs. Springs of inlet and final valves identical.

Characteristics of springs of valves are provided in tab. 3.7.

Parameter	External springs	Internal springs
Spring length in working order, mm	43,2	38,2
Spring length under loading, mm/N	36,1/168	32,6/80
Admissible not coaxiality of rounds, mm	2,1	1,9

Pushers of valves hydraulic. Free wheeling of pushers: nominal 0,023 — 0,059 mm, maximum permissible 0,1 mm.

Valves are manufactured of special steel, installed in one row over cylinders vertically. Are put in action by camshaft cams through hydraulic pushers therefore adjustment of gaps in the drive is not required.

Characteristics of valves are provided in tab. 3.8.

Parameter	Inlet valves	Final valves
Diameter of a plate of the valve, mm	39,0-39,2	32,0-32,2
Diameter of a core of the valve, mm	6,965-6,980	6,945-6,960
Total length of the valve, mm	100,53-100,97	100,38-100,82

Laying of a head of the block of cylinders is produced from synthetic materials with metal inserts around cylinders. At laying installation the tag of "TOP" has to be turned to a head of the block of cylinders.

Laying of four sizes on thickness depending on a vystupaniye of pistons in relation to the surface of the block of cylinders is issued. Thickness is marked by cuts on an edge of laying (tab. 3.9).

Vystupaniye of pistons, mm	Thickness of laying of a head of the block of cylinders, mm	Final valves
Less than 0,505	1,1+0,03	0
	1,15+0,03	1
0,505-0,555	1,20+0,05	2
More than 0,555	1,25+50,05	3

The camshaft is cast from cast iron, has eight cams and rotates in five bearings formed by a head of cylinders and removable covers. Admissible axial gap of the camshaft of 0,115 — 0,188 mm. Height of cams of the camshaft: inlet valves of 49,20 mm, final valves of 49,15 mm. Maximum permissible wear of 0,2 mm. Diameter of necks of the camshaft of 29,0935 — 29,955 mm.

Gap between necks of the camshaft and openings of support: nominal 0,045 — 0,086 mm, maximum permissible 0,1 mm. Maximum permissible beating of 0,05 mm.

The belt of the drive of the camshaft of the Nissan brand stretches a semi-automatic tension roller.

The drive of valves is carried out by camshaft cams through plungers of the hydraulic pushers established directly in a head of the block of cylinders.

Fig. 3.13. Hydraulic pusher: 1 — the backpressure valve; 2 — a camshaft cam; 3 — a pusher; 4 — the cylinder; 5 — a spring of compensation of gaps; 6 — a valve core; And — the camera of high pressure; B — the channel of supply of oil to a pusher; In — the accumulative camera

The hydraulic pusher consists of two main mobile parts: actually the pusher of 3 (fig. 3.13) serving at the same time in the course of work as a plunger and the cylinder 4. Under pressure of a spring the 5th plunger and the cylinder are removed from each other thanks to what the gap between a cam of the camshaft and an end face of a core of the valve is chosen. Filling and locking of the camera A of high pressure is provided with the backpressure valve 1.

Fig. 3.14. Action of a hydraulic pusher: I \beginning of raising of the valve; II \maximum raising of the valve; III \compensation of a gap between a cam and a pusher; IV \channels in a hydraulic pusher: And — an air vent; B — the channel of supply of oil to a pusher; V \the channel of a supply of oil from the oil pump

At the time of the beginning of raising of the valve (fig. 3.14, I), i.e. at the time of a camshaft cam nabeganiye on a pusher end face, the backpressure valve locks the camera and pressure increases in it. Increase in pressure does not lead to reduction of the volume occupied by oil in the camera of high pressure. The pusher, thus, works as a solid body. At the time of the maximum raising of the valve (see fig. 3.14, II) the camshaft cam with a force presses on a pusher that leads to significant increase in pressure in a pusher cavity. A small amount of oil is thrown out through thinnesses between the cylinder and a plunger that leads to compression of a hydraulic pusher as much as possible on 0,10 mm. Such compression is structurally necessary for extra earnings of pushers at reduction of distance between a cam of the camshaft and an end face of a pusher.

Compensation of a gap between a cam and a pusher (fig. 3.14, III) happens as follows. The cam of the camshaft does not press on a pusher, and pressure in the camera of high pressure falls. The spring parts a plunger and the cylinder, choosing as that a gap between a cam and an end face of a core of the valve. At this moment the backpressure valve opens, a quantity of oil comes from the accumulative camera to the camera of high pressure. This quantity depends on the size of the chosen gap.

The increased noisiness of operation of the drive of the valvate mechanism after launch of the engine is not a malfunction sign. Emergence of noise is connected with the fact that at an engine stop a part of oil follows from a cavity of pushers. From the beginning of operation of the engine the camera of high pressure is filled again and noise stops. Filling of the camera of high pressure continues until the engine does not get warm up to the working temperature. The design of a lubricant contour of a head of the block of cylinders expels full removal of oil from channels after an engine stop. It provides supply of oil in pushers right after launch of the engine and the fastest termination of noise in the drive of the valvate mechanism.

After an engine stop from the channels going from the oil pump oil flows down, and channels of a supply of oil to pushers remain filled with oil. In order that at the time of launch of the engine air did not come under the influence of oil pressure to a pusher cavity, in channels of supply of oil to pushers there are air vents providing an automatic purge of a cavity of pushers. Besides, air vents allow to reduce pressure of the oil coming to pushers (fig. 3.14, IV and 3.14, V).

Phases of gas distribution of the CD20E engine are given in tab. 3.10.

Parameter	Value, hail
The beginning of opening of the inlet valve to release step VMT	14
Closing of the inlet valve after compression step NMT	38
The beginning of opening of the final valve to NMT of the working course	56
Closing of the final valve after release step VMT	12

Frequency of replacement of a driving belt — through each 90 000 km of a run. The arrows applied on a belt have to correspond to the direction of rotation.