CN115199374A

CN115199374A - Engine four-stroke braking system and method

Info

Publication number: CN115199374A
Application number: CN202110399271.9A
Authority: CN
Inventors: 杨洲; 朱汝杰; 奚正
Original assignee: Shanghai Youshun Automobile Technology Co ltd
Current assignee: Shanghai Youshun Automobile Technology Co ltd
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2022-10-18

Abstract

The invention provides a system and a method for four-stroke braking of an engine, which adopt four rocker arms to generate valve motion for engine braking, and comprise the steps of generating an exhaust valve lift which is the same as that generated when the engine is ignited by utilizing a conventional exhaust rocker arm, generating a braking exhaust valve lift for four-stroke braking of the engine by utilizing a braking exhaust rocker arm, generating an intake valve lift which is the same as that generated when the engine is ignited by utilizing a conventional intake rocker arm, opening the intake valve of the engine in an expansion stroke of the engine by utilizing a braking intake rocker arm, generating the braking intake valve lift of the engine, increasing the air inflow introduced into an engine cylinder, increasing the resistance and exhaust back pressure of the cylinder piston in the exhaust stroke of the engine, increasing pumping pressure work and the rotating speed of a turbocharger, and improving the braking power of the engine.

Description

Engine four-stroke braking system and method

Technical Field

The invention relates to the field of machinery, in particular to the field of engine valve driving, and particularly relates to a four-stroke braking system and a four-stroke braking method for an engine.

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 engine four-stroke brake, that is, the compression release brake is applied only once near 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 as much as 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 engine four-stroke braking is disclosed in U.S. patent No. US 3,220,392, supplied by Cummins (Cummins), according to which an engine braking system is manufactured 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 (high load, high leakage and high deformation) and a hydraulic jack and the like.

US patents 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), that actuates only one of the two exhaust valves during braking, in a manner that remains hydraulically coupled.

US 4,572,114 (1986) and US 5,537,976 (1996) disclose devices and methods for two-stroke engine braking, including cam actuation, hydraulic connections, high speed solenoid valves, and electronic controls 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.

Another engine two-stroke braking device and method is disclosed in US 6,293,248 (2001). 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 an engine two-stroke brake apparatus and method similar to the 2001 US patent, 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.

Disclosure of Invention

The invention provides an engine four-stroke braking system, which solves the problems of complex structure and control, poor reliability and durability, high hydraulic drive 'three-high', high cost, incapability of becoming a product and the like in the conventional engine braking technology while improving the braking power of an engine.

The invention provides an engine four-stroke brake system, which comprises a brake intake cam and a half rocker arm, wherein the brake intake cam is used for driving a conventional intake rocker arm of an engine to generate an intake valve lift of the engine brake, a connecting rod piston mechanism is arranged in the half rocker arm, the connecting rod piston mechanism comprises a first connecting rod, a second connecting rod and a connecting piston, one end of the first connecting rod is rotatably connected with one end of the second connecting rod, the other end of the first connecting rod is rotatably connected with the half rocker arm, the other end of the second connecting rod is rotatably connected with one end of the connecting piston, the contraction and extension between the first connecting rod and the second connecting rod change the length of the connecting rod piston mechanism to lose and transmit the motion of the brake intake cam, and when the connecting piston straightens the first connecting rod and the second connecting rod, the other end of the connecting piston is connected with the conventional intake rocker arm to transmit the motion of the brake cam to an intake valve of the engine.

Furthermore, the half rocker arm and the conventional rocker arm of the engine are arranged on a rocker shaft of the engine side by side, when the engine is braked, 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 range for engine braking.

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.

The invention provides a four-stroke braking method of an engine, which adopts four rocker arms to drive a valve of the engine, wherein the four rocker arms comprise a conventional exhaust rocker arm, a braking exhaust rocker arm, a conventional intake rocker arm and a braking intake rocker arm,

a. by utilizing the conventional exhaust rocker arm, the same exhaust valve lift is generated when the engine is ignited,

b. the braking exhaust rocker arm is utilized to generate the braking exhaust valve lift of the four-stroke braking of the engine,

c. using a conventional intake rocker arm, the same intake valve lift is produced as when the engine is fired, an

d. The air inlet valve of the engine is opened in the expansion stroke of the engine by using the braking air inlet rocker arm,

generating a braking intake valve lift of the engine.

Furthermore, the four rocker arms are fixed chain type mechanisms, and the cam motion of the engine is transmitted to the valve of the engine in a solid connection mode.

Further, the engine braking intake valve lift is opened after the compression top dead center of the engine and closed near the expansion bottom dead center of the engine, and the height of the engine braking intake valve lift is smaller than that of the intake valve lift during engine ignition.

Further, the brake intake rocker arm comprises a half rocker arm, and the half rocker arm drives a conventional intake rocker arm to generate an intake valve lift of engine braking.

Further, the exhaust valve lift of the engine four-stroke brake comprises:

a. exhaust valve lift for compression release near engine compression top dead center, and

b. an exhaust valve lift of an exhaust cycle near engine intake bottom dead center.

Further, the exhaust valve lift of the four-stroke engine brake is from a single exhaust valve of the engine.

Compared with the prior art, the invention has positive and obvious effect. The engine four-stroke braking system and the method of the invention adopt the fixed chain type rocker arm, transfer the load through a solid connection mode, particularly keep the conventional intake/exhaust rocker arm and the conventional intake/exhaust valve lift generated by the conventional intake/exhaust rocker arm, only increase the braking intake valve lift (the second intake valve lift) and the intake of the engine cylinder on the basis of the conventional engine four-stroke braking, improve the exhaust resistance during the exhaust stroke, increase the braking power, and have the advantages of simple and reliable structure, easy manufacture and assembly, cost reduction, wide application and the like.

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 the intake and exhaust valve lift for four-stroke engine braking of 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 illustration of the retracted state of the rod-and-piston mechanism in one embodiment of the present invention wherein the brake intake rocker arm employs a fixed-chain brake mechanism.

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 the intake and exhaust valve lift for four-stroke engine braking of 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 invention increases the lift 302 of the braking air inlet valve during the expansion (power) stroke of the engine, introduces fresh air into the cylinder of the engine, increases the resistance of the cylinder piston rising in the following exhaust stroke of the engine (increases the pump pressure to do work), and improves the braking power of the 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 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), but adds the braking intake rocker arm 32 on the basis of four-stroke braking of the engine in the prior art, and opens an intake valve of the engine (here, the half rocker arm 32 drives the conventional intake rocker arm 31) in an 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 a fixed chain type brake mechanism employed 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 that urges the half rocker arm 32 toward the brake intake cam 330 via a roller shaft 331 and a 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, 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 valve motion from the normal (firing) intake cam of 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 powered on, the engine oil of the engine is supplied 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) leftwards, the connecting

rods

152 and 154 in the contraction position in fig. 5 are straightened, the connecting piston 160 extends, the braking intake semi-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 shown in fig. 4 is generated. Of course, oil may also 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 force of preload spring 136, which makes it easier to pull rod piston mechanism 100 in the retracted position of fig. 5 up to the fully extended deployed position.

The invention reserves the conventional exhaust rocker arm 21 and the conventional intake rocker arm 31 as well as the conventional (ignition) exhaust valve lift 20 and the conventional (ignition) intake valve lift 30 generated by the conventional exhaust rocker arm and the conventional (ignition) intake valve lift, only adds the braking intake valve lift (second intake valve lift) 302 in the four-stroke braking of the conventional engine, and solves the problems of complicated mechanism, increased cost, reduced reliability and durability and the like caused by converting the conventional (intake/exhaust) rocker arm into a cylinder deactivation rocker arm by the two-stroke braking of the engine.

The above description should not be taken as limiting the scope of the invention, but as being a representative of the invention in which many other variations 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 a single valve can be opened, but also double valves can be opened. 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

1. An engine braking system, characterized by, include braking air intake cam and a half rocking arm for the conventional air intake rocking arm of drive engine produces the air intake valve lift of engine braking, half rocking arm in be equipped with the connecting rod piston mechanism, the 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 of second connecting rod link to each other with the one end rotary type, the other end of first connecting rod with half rocking arm link to each other with rotary type, the other end of second connecting rod with the one end rotary type of connecting piston link to each other, the shrink and the extension between first connecting rod and the second connecting rod change the length of connecting rod piston mechanism, 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 the conventional air intake rocking arm link to transmit the motion of braking air intake cam to the air intake valve of engine.

2. The engine braking system of 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 braking system of claim 1, wherein: the rotationally coupling includes a cylindrical coupling.

4. The engine braking system of claim 1, wherein: the rotationally coupling may include a spherical coupling.

5. The engine braking system of 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 braking system of 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 braking system according to claims 1 and 6, characterized in that: the oil pressure control valve further 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 oil pressure effect.

8. A method of engine braking, characterized by: four rocker arms are used to actuate the valves of the engine, including a conventional exhaust rocker arm, a brake exhaust rocker arm, a conventional intake rocker arm, and a brake intake rocker arm, and during engine braking,

b. the braking exhaust rocker arm is utilized to generate the braking exhaust valve lift of the engine brake,

d. And opening an air inlet valve of the engine in an expansion stroke of the engine by using the braking air inlet rocker arm to generate the braking air inlet valve lift of the engine.

9. The engine braking method according to claim 8, characterized in that: the four rocker arms are fixed chain type mechanisms and transmit the motion of the engine cam to the valve of the engine in a solid connection mode.

10. The engine braking method according to claim 8, characterized in that: the engine braking air inlet valve lift is opened after the compression top dead center of the engine and closed near the expansion bottom dead center of the engine, and the height of the engine braking air inlet valve lift is smaller than the air inlet valve lift when the engine is ignited.

11. The engine braking method according to claim 8, characterized in that: the braking air inlet rocker arm comprises a half rocker arm, and the half rocker arm drives a conventional air inlet rocker arm to generate the air inlet valve lift for engine braking.

12. The engine braking method according to claim 8, characterized in that: the engine braking exhaust valve lift includes:

13. The engine braking method according to claim 8 or 10, characterized in that: the engine braking exhaust valve lift is from a single exhaust valve of the engine.