CN215256367U - Four-stroke braking system of engine - Google Patents

Abstract

The utility model provides a system of engine four-stroke braking, adopt four rocking arms to produce the valve motion of engine braking, the same exhaust valve lift when utilizing conventional exhaust rocking arm to produce and igniting with the engine, utilize the braking exhaust rocking arm to produce the braking exhaust valve lift of engine four-stroke braking, utilize the conventional rocker arm that admits air to produce the same air inlet valve lift when igniting with the engine, utilize the braking air inlet rocking arm, open the air inlet valve of engine at the expansion stroke of engine, the braking air inlet valve lift of engine is produced, the engine cylinder air input is introduced in the increase, the resistance and the exhaust backpressure that cylinder piston rises in the increase engine exhaust stroke, increase pumping pressure acting and turbo charger's rotational speed, improve the brake power of engine.

Description

Four-stroke braking system of engine

Technical Field

The utility model relates to the field of machinary, especially, relate to engine valve drive field, especially an engine four-stroke braking system.

Background

Conventional valve actuation for vehicle engines is well known in the art and has been in use for over a hundred years. Conventional valve actuation utilizes conventional valve actuators (including conventional rocker arms) to control the motion of engine valves for conventional spark-ignition operation of the engine. But due to additional demands on engine fuel efficiency, exhaust emissions and engine braking, more and more engines employ variable valve actuation, including engine braking. Engine brakes have been widely used on commercial vehicle engines. The four-stroke engine brake is currently used in the market, namely, only once compression release brake is carried out at the end of the compression stroke (near the compression top dead center) in one cycle of the engine (four strokes: intake stroke, compression stroke, expansion stroke and exhaust stroke). The two-stroke brake of the engine is to do two times of compression release brake near the compression top dead center and the expansion top dead center respectively in one cycle (four-stroke). So, theoretically, the power of the two-stroke brake should be twice that of the four-stroke brake. However, the two-stroke braking requires the cylinder of the engine to be stopped, namely, the valve lift of the ignition of the engine is cancelled during the braking, so that the technical difficulty is high, the mechanism is complex, the cost is high, and no product exists so far.

One prior example of four-stroke engine braking is disclosed in U.S. patent No. US 3,220,392, by Cummins (Cummins), according to which an engine braking system is made with commercial success. However, such engine braking systems are engine-mounted accessories. To install the engine brake, a gasket is added between the cylinder and the valve cover, thus additionally increasing the height, weight, and cost of the engine. In addition, the cummins brake adopts hydraulic connection to drive the valve, and has the problems of three high hydraulic pressures (high load, high leakage and high deformation), a hydraulic jack and the like.

US 5,937,807 and US 5,975,251 (1999) disclose another four-stroke brake that adds a brake exhaust rocker arm, mounted on the rocker shaft alongside a conventional exhaust rocker arm (also called an ignition exhaust rocker arm), which actuates only one of the two exhaust valves during braking, in a manner that remains hydraulically connected.

US 4,572,114 (1986) and US 5,537,976(1996) disclose an apparatus and method for two-stroke engine braking, which includes cam actuation, hydraulic connections, high speed solenoid valves, and electronic control to achieve different valve motions for engine ignition or engine braking. Since the solenoid valve needs to be opened at least once during each cycle, there are particularly high demands on the reliability and durability of the solenoid valve. Coupled with other problems with hydraulic actuation such as control of valve seating velocity, cold start of the engine, etc., the invention has not been practical.

US 6,293,248 (2001) discloses another device and method for two-stroke engine braking. Four rocker arms are adopted: the cylinder deactivation exhaust rocker arm, the brake exhaust rocker arm, the cylinder deactivation intake rocker arm and the brake intake rocker arm drive the valve of the engine, the structure and the control are complex, and the valve of the engine is opened by adopting hydraulic drive.

US 8,936,006 (2015) discloses a two-stroke engine braking device and method similar to the 2001 US, again using four rocker arms: cylinder deactivation exhaust rocker arm, brake exhaust rocker arm, cylinder deactivation intake rocker arm and brake intake rocker arm. The cylinder deactivation mechanism is a motion loss mechanism integrated in a valve bridge of an engine, a braking exhaust rocker arm and a braking intake rocker arm are both hydraulically driven to open a valve (double valves are opened when the engine is ignited), the lift of the braking valve is influenced by the inclination of the valve bridge, and the reliability and the durability are difficult problems.

SUMMERY OF THE UTILITY MODEL

The utility model provides an engine four-stroke braking system when improving engine braking power, solves structure and control complicacy among the current engine braking technique, reliability and durability poor, hydraulic drive "three high", the cost is expensive and can't become product scheduling problem.

The utility model provides an engine four-stroke braking system, including braking air intake cam and a half rocking arm for the conventional air intake rocking arm of drive engine produces the intake valve lift of engine braking, half rocking arm in be equipped with connecting rod piston mechanism, connecting rod piston mechanism include first connecting rod, second connecting rod and connecting piston, the one end of first connecting rod and the one end rotary type ground of second connecting rod link to each other, the other end of first connecting rod with half rocking arm rotary type ground link to each other, the other end of second connecting rod and the one end rotary type ground of connecting piston link to each other, the shrink between first connecting rod and the second connecting rod and the extension change connecting rod piston mechanism's length, be used for losing and transmitting the motion of braking air intake cam, when connecting piston straightens first connecting rod and second connecting rod, the other end of connecting piston with conventional air intake rocking arm link to each other, the motion of the brake cam is transmitted to an intake valve of the engine.

Furthermore, the half rocker arm and a conventional rocker arm of the engine are arranged on a rocker arm shaft of the engine side by side, when the engine is braked, oil pressure of the engine drives a connecting piston in the half rocker arm to straighten a first connecting rod and a second connecting rod, and the connecting piston acts on one end, close to an air inlet valve of the engine, of the conventional air inlet rocker arm to generate an air inlet valve lift of the engine brake.

Further, the rotatably coupling includes a cylindrical coupling.

Further, the rotationally coupling includes a cylindrical-spherical coupling.

Furthermore, the engine further comprises an anti-flying off spring which pushes the half rocker arm to a brake air inlet cam of the engine.

Furthermore, the device also comprises a pre-tightening spring, wherein the pre-tightening spring enables an included angle between the upper connecting rod and the lower connecting rod to be reduced and the connecting rod piston mechanism to be shortened.

Furthermore, the oil cylinder also comprises a spring piston, one side of the spring piston comprises the pre-tightening spring, and the other side of the spring piston can bear the action of oil pressure.

Compared with the prior art, the utility model has positive and obvious effect. The utility model discloses an engine four-stroke braking system and method adopt solid chain formula rocking arm, pass through solid connected mode transmission load, especially remain conventional advance/exhaust rocking arm and advance/exhaust valve lift by its conventional that produces, only on the basis of conventional engine four-stroke braking, increase braking air inlet valve lift (the second time air inlet valve lift) and engine cylinder and admit air, improve the exhaust resistance during the exhaust stroke, increase braking power, have simple structure reliably, the manufacturing assembly is easy, reduce cost and use advantages such as extensive.

Drawings

FIG. 1 is a schematic diagram of intake and exhaust valve lift during normal operation (firing) of an engine.

FIG. 2 is a schematic diagram of intake and exhaust valve lift during four-stroke engine braking.

Fig. 3 is a schematic diagram of intake and exhaust valve lift for four-stroke engine braking according to the present invention.

Fig. 4 is a schematic diagram of four rocker arms of the engine four-stroke brake of the present invention.

Fig. 5 is a schematic diagram of the retraction state of the rod-piston mechanism in a specific structure of the braking intake rocker arm adopting the fixed chain type braking mechanism of the present invention.

Detailed Description

FIG. 1 is a schematic diagram of intake and exhaust valve lift during engine ignition in the prior art. Valve motion for conventional ignition of an engine is common knowledge. The exhaust cam of the engine drives a conventional (firing) exhaust rocker arm, which opens the exhaust valve on the exhaust stroke of the engine, discharging the combusted exhaust gases. The valve lift 20 (thin solid line in fig. 1) of the exhaust valve is opened before the expansion (power) bottom dead center of the engine and closed after the exhaust top dead center of the engine. An intake cam of the engine drives a conventional (ignition) intake rocker arm, and an intake valve is opened in an intake stroke of the engine to suck fresh air. The valve lift 30 (thick solid line in fig. 1) of the intake valve is opened before the exhaust top dead center of the engine and closed after the intake bottom dead center of the engine. It is particularly worth noting that the function of the engine is mainly that the ignition produces positive power. Whether engine two-stroke braking or engine four-stroke braking, it is necessary to ensure that the intake and exhaust valve lifts 20 and 30 shown in fig. 1 are present at the time of engine ignition.

FIG. 2 is a schematic diagram of intake and exhaust valve lift during four-stroke braking of a prior art engine. The four-stroke engine braking valve motion is also well known and is generated in many ways, and one of the most widely used methods at present is that an exhaust brake cam drives a valve of an engine by braking an exhaust rocker arm. At engine braking, in addition to the exhaust valve lift 20 and the intake valve lift 30 that retain the engine's conventional firing, the exhaust valve lift 201 and 204 (thin dashed lines in fig. 2) of the engine brake are increased. Wherein the exhaust valve lift 201 is a compression release brake valve motion, occurring near the compression top dead center of the engine (open before compression top dead center, closed after compression top dead center), for releasing high pressure gas (air) compressed in the cylinder during the compression stroke of the engine; the exhaust valve lift 204 is the exhaust cycle brake valve motion, and occurs near the intake bottom dead center of the engine (the exhaust valve lift is opened before the intake bottom dead center and closed after the intake bottom dead center), so that the gas in the exhaust pipe reversely fills the cylinder near the closing of the intake valve, and the brake power is increased.

Fig. 3 is a schematic diagram of intake and exhaust valve lift for four-stroke engine braking according to the present invention. Unlike the prior art four-stroke engine brake shown in fig. 2, the braking intake valve lift 302 (dashed bold line in fig. 3), also called the second intake valve lift (the intake valve lift 30 generated during the intake stroke is the first intake valve lift), is increased during the expansion (power) stroke of the engine, and is opened after compression top dead center and closed near expansion bottom dead center. The braking intake valve lift (second intake valve lift) 302 is smaller (lower) than the first intake valve lift 30 at the time of ignition, but larger (higher) than the braking exhaust valve lift (201, 202), with respect to the ignition intake valve lift 30.

The utility model discloses increase braking air inlet valve lift 302 during the expansion (acting) stroke of engine, introduce the cylinder of engine with fresh air for the resistance increase (increase pump pressure acting) that cylinder piston rises in the engine exhaust stroke that follows improves the braking power of engine. In addition, the air intake amount is increased in each engine braking cycle period, the exhaust gas amount (exhaust gas pressure) and the rotating speed of the turbocharger are increased, the air intake amount is further increased, a virtuous cycle is formed, and the braking power is increased.

Fig. 4 is a schematic diagram of four rocker arms used to describe the four-stroke engine braking of the present invention. The engine braking system includes a conventional exhaust rocker arm 21, a brake exhaust rocker arm 22 (i.e., the brake exhaust rocker arm in the above-described prior art four-stroke brake), a conventional intake rocker arm 31, and a brake intake rocker arm 32. The conventional rocker arms (the conventional exhaust rocker arm 21 and the conventional intake rocker arm 31) herein refer to the rocker arms for engine ignition described above, and are distinguished from the brake rocker arms (the brake exhaust rocker arm 22 and the brake intake rocker arm 32). The four rocker arms shown in fig. 4 are arranged side by side on the same rocker shaft 205, but there are other mounting arrangements, such as four rocker arms arranged on two different rocker shafts.

It is noted that engine two-stroke braking requires cancellation of intake and exhaust valve motion at ignition, that is, conversion of a conventional rocker arm to a deactivating rocker arm that cancels valve motion at braking. As the technical difficulty of the cylinder deactivation rocker arm is high, the mechanism is complex, the cost is increased, the reliability of ignition operation is reduced and the like, the cylinder deactivation rocker arm product does not exist in the field of commercial vehicle engines.

The embodiment of the application does not use a cylinder deactivation exhaust rocker arm or a cylinder deactivation intake rocker arm (the traditional conventional rocker arm is reserved), and only adds the braking intake rocker arm 32 on the basis of four-stroke braking of the engine in the prior art, so that an intake valve of the engine (here, the half rocker arm 32 drives the conventional intake rocker arm 31) is opened in the expansion stroke of the engine to generate the braking intake valve lift 302 of the engine. In this embodiment, the brake intake rocker arm 32 adopts a fixed chain type brake mechanism, and the specific structure is as follows.

Fig. 5 is a diagram for describing a specific structure of the fixed chain type brake mechanism used in the brake intake rocker arm of the present invention. The brake intake rocker arm 32 is shown as a half rocker arm in which there is a connecting rod-piston mechanism 100 comprising a first connecting rod 152, a second connecting rod 154 and a connecting piston 160. One end of the first link 152 is rotatably connected to one end of the second link 154, the other end of the first link 152 is rotatably connected to the rocker arm 32, and the other end of the second link 154 is rotatably connected to one end of the connecting piston 160. When the connecting rod-piston mechanism 100 is deployed, the other end face (protruding end) of the connecting piston 160 is connected to the conventional intake rocker arm 31 (see fig. 4, one end 36 of the conventional intake rocker arm 31 near the intake valve 300 has a protruding portion 38 on the side of the brake intake half rocker arm 32, and a lash adjustment mechanism is provided that sets the lash between the connecting piston 160 and the brake intake rocker arm 32), transmitting the motion of the brake intake cam 330 to the intake valve. When the rod-piston mechanism 100 is retracted (see fig. 5), the contraction between the first and second connecting rods 152 and 154 shortens the rod-piston mechanism 100, canceling (losing) the movement of the brake intake cam 330. That is, the motion of the brake intake cam 330 is not transmitted to the conventional intake rocker arm 31 and the intake valve 300.

The angle of extension and retraction between the first link 152 and the second link 154 of the connecting rod piston mechanism 100 is between greater than 0 ° and less than or equal to 180 °, and the minimum angle can be controlled by a stop mechanism. When the included angle is a straight angle (180 °), the first and second connecting rods 152 and 154 are on the axis of the connecting piston 160, the connecting piston 160 is fully extended, and the connecting-rod-piston mechanism 100 is longest. When the angle decreases, the connecting piston 160 retracts and the connecting rod-piston mechanism 100 shortens.

The present embodiment further includes a drop-off prevention spring 198 for urging the half rocker arm 32 toward the brake intake cam 330 via the roller shaft 331 and the roller 335, preventing an impact between the half rocker arm 32 and the conventional intake rocker arm 31.

The operation of this embodiment is as follows. In the normal (or default) state, the brake control valve (not shown) is de-oiled, the oil pressure in the spring piston oil chamber 132 and the drive piston oil chamber 162 is zero, the pre-load spring 136 pushes the spring piston 130 out (upward), pushing the connecting piston mechanism 100 to the retracted (contracted) position shown in fig. 5, eliminating (losing) the motion of the brake intake cam 330, and the intake valve only produces the valve motion produced by the normal (firing) intake cam from the normal intake rocker arm 31.

When the braking intake valve lift (second intake valve lift) 302 is needed, the brake control valve (not shown) is turned on to supply oil, the engine oil supplies oil to the driving piston oil chamber 162 through oil passages (such as oil holes (not shown) in the rocker shaft 205b and oil passages 213 and 214 in the rocker arm 32), the oil pressure pushes out the driving piston 160 (note that the connecting piston and the driving piston are the same piston here) (to the left), the connecting rods 152 and 154 in the contracted position in fig. 5 are straightened, the connecting piston 160 extends out, the braking intake half rocker arm 32 is connected with the conventional intake rocker arm 31, the motion of the braking intake cam 330 is transmitted to the intake valve of the engine, and the braking intake valve lift 302 as shown in fig. 4 is generated. Of course, oil may be simultaneously supplied to spring piston oil chamber 132 through oil bore 213 to push spring piston 130 back (downward in FIG. 5) against the biasing force of biasing spring 136, which may facilitate pulling rod piston mechanism 100 in the retracted position of FIG. 5 to the fully extended and extended position.

The utility model discloses retained conventional exhaust rocking arm 21 and conventional intake rocker arm 31 and the conventional (ignition) exhaust valve lift 20 and the conventional (ignition) intake valve lift 30 that produce, only increased braking intake valve lift (second intake valve lift) 302 in traditional engine four-stroke braking, eliminated engine two-stroke braking and turned into conventional (advance/exhaust) rocking arm and the mechanism that brings is complicated, cost increase, reliability and durability reduction scheduling problem.

The above description should not be taken as limiting the scope of the invention, but rather as representing a specific exemplification of the invention, from which many other evolutions are possible. For example, the engine braking methods or systems shown herein may be used not only in overhead cam engines, but also in push rod/push tube engines; not only can open a single valve, but also can open double valves. In addition, the connecting rod piston mechanism can also be arranged in a brake exhaust (half) rocker arm and driven by a brake exhaust cam to push a conventional exhaust rocker arm to open an exhaust valve brake. The four rocker arms may also be different in structure, arrangement and arrangement, for example, they may be single rocker arms, two rocker arms, or they may be arranged on different rocker shafts. In addition, the rotary connection between the connecting rod and the piston can be a pin (cylindrical surface) or a ball (spherical surface). In addition to the fixed chain type rocker arm, other driving methods such as hydraulic pressure may be selected.

Claims (7)

1. A four-stroke engine braking system, comprising a braking intake cam and a half rocker arm for actuating a conventional intake rocker arm of an engine to generate an intake valve lift for braking the engine, said half rocker arm being provided with a link piston mechanism therein, said link piston mechanism comprising a first link, a second link and a connecting piston, one end of the first link being rotatably connected to one end of the second link, the other end of the first link being rotatably connected to said half rocker arm, the other end of the second link being rotatably connected to one end of the connecting piston, contraction and expansion between the first link and the second link changing the length of the link piston mechanism for losing and transmitting the motion of said braking intake cam, the other end of the connecting piston being connected to said conventional intake rocker arm when the connecting piston straightens the first link and the second link, the motion of the brake intake cam is transferred to the intake valve of the engine.

2. The engine four-stroke brake system according to claim 1, wherein: the half rocker arm and the conventional air inlet rocker arm are arranged on a rocker arm shaft of the engine side by side, when the engine brakes, the oil pressure of the engine drives the connecting piston in the half rocker arm to straighten the first connecting rod and the second connecting rod, and the connecting piston acts on one end, close to an air inlet valve of the engine, of the conventional air inlet rocker arm to generate an air inlet valve lift for braking the engine.

3. The engine four-stroke brake system according to claim 1, wherein: the rotationally coupling includes a cylindrical coupling.

4. The engine four-stroke brake system according to claim 1, wherein: the rotationally coupling may comprise a spherical coupling.

5. The engine four-stroke brake system according to claim 1, wherein: the anti-flying-off device further comprises an anti-flying-off spring, and the anti-flying-off spring pushes the half rocker arm to a brake air inlet cam of the engine.

6. The engine four-stroke brake system according to claim 1, wherein: the hydraulic cylinder further comprises a pre-tightening spring, and the pre-tightening spring enables an included angle between the upper connecting rod and the lower connecting rod to be reduced and the connecting rod piston mechanism to be shortened.

7. The engine four-stroke brake system according to claim 6, wherein: the hydraulic oil cylinder also comprises a spring piston, one side of the spring piston comprises the pre-tightening spring, and the other side of the spring piston can bear the action of oil pressure.

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