JPH0979015A - Engine braking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase engine braking force by providing a hydraulic circuit for supplying low oil pressure to actuate a piston member and lifting an exhaust valve in need, and by providing the hydraulic circuit with a valve means for closing the hydraulic circuit during the supply of low oil pressure to maintain high oil pressure in order to hold the lift. SOLUTION: When an operating switch is turned on at the time of increasing engine braking force, engine oil is fed to an oil intake part 30 of a housing 3, and a spool valve 6 is slided by this oil pressure. Then the engine oil enters a high oil pressure chamber 43 via a check valve 7 and the spool valve 6. When the oil pressure acts upon a piston head 33, a piston member 4 is pushed down so as to come in contact with an exhaust valve immediately before closing through an intermediate shaft 20, so that the exhaust valve is slightly opened. As a result, a piston of an engine in inertial motion makes negative work and speed is thereby reduced by that amount and engine braking force is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine braking device for releasing a compression pressure in a cylinder to increase an engine braking force.

[0002]

2. Description of the Related Art Recently, there has been proposed an engine brake device for increasing the engine braking force by releasing the compression pressure in the cylinder by lifting the exhaust valve other than the exhaust stroke when using the engine brake. There is. As a mechanism to forcibly lift the exhaust valve,
It is known that a housing having a hydraulic circuit is provided in the upper part of a valve operating mechanism and a high hydraulic pressure pushes a piston for an exhaust valve lift.

[0003]

However, in this hydraulic engine braking device, a hydraulic pressure generating piston driven by a push rod of a valve operating mechanism is provided at one end of a hydraulic circuit, and the hydraulic pressure is used for exhaust valve lift. Since it is supplied to the piston, there is a problem that the size of the entire apparatus becomes large and the engine height, weight and cost increase.

[0004]

In order to solve the above-mentioned problems, the present invention provides a piston member movably provided in a housing arranged above an exhaust valve, and a low hydraulic pressure formed in the housing. A hydraulic circuit for operating the piston member to lift the exhaust valve appropriately, and a hydraulic circuit that is provided in the hydraulic circuit to appropriately close the hydraulic circuit during low hydraulic pressure supply to maintain high hydraulic pressure, and to stop hydraulic pressure in the hydraulic circuit by stopping supply. And means for releasing the valve. With this configuration, the piston member operates when a low hydraulic pressure is supplied to the hydraulic circuit to come into contact with the exhaust valve and lift the exhaust valve by a predetermined amount. The valve means appropriately closes the hydraulic circuit when supplying low hydraulic pressure to maintain high hydraulic pressure that resists the reaction force from the exhaust valve, thereby holding the exhaust valve at a predetermined lift position and during the compression / expansion stroke. Always keep the valve open. When the supply of the low hydraulic pressure is released, the valve means releases the high hydraulic pressure in the hydraulic circuit to stop the pressing of the piston member so that the exhaust valve does not interfere with the normal opening / closing operation.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an engine braking device to which the present invention is applied. This engine braking device has a housing 3 arranged above the exhaust valves 1 and 2,
The piston member 4 is provided so as to be movable in the vertical direction, the hydraulic circuit 5 is formed in the housing 3, and the spool valve 6 and the check valve 7 that are valve means provided in the hydraulic circuit 5 are mainly configured. There is.

As shown in FIG. 2, a pair of exhaust valves 1 and 2 are provided in each cylinder 8 of the engine, and a valve element 11 is seated on an opening end (valve seat) 10 of an exhaust port 9 facing the inside of the cylinder. , And a valve shaft 12 attached to the axial center of the valve body 11 and extending upward. The valve shaft 12 is provided with a return spring 13 that urges the valve shaft 12 in the valve closing direction (upward), and the head 14 of the valve shaft 12 is connected to one end of a rocker arm 15 via a bridge 16. The rocker arm 15 has a central portion pivotally supported by a rocker shaft 17, and the other end is engaged with a valve operating cam 19 via a cam follower 18. That is, the pair of exhaust valves 1 and 2 are simultaneously lifted by the cam-driven rocker arm 15 at a predetermined timing during the exhaust stroke. Then, of the pair of exhaust valves 1 and 2, the valve shaft 12 of one exhaust valve 1 is provided with an intermediate shaft 20 which is located on the extension of the exhaust valve 1 and which vertically penetrates the end portion of the bridge 16 and the sleeve 21. It is slidably supported by the bridge 16 via the. A flange 22 that engages with the lower surface of the sleeve 21 is formed at the lower end of the intermediate shaft 20, and when the intermediate shaft 20 is pushed downward, the exhaust valve 1 is lifted regardless of the operation of the rocker arm 15, and the rocker arm 15 When is swung, the exhaust valve 1 is pushed integrally with the bridge 16. A nut 23 for adjusting the positional relationship with the bridge 16 (the upper limit of the intermediate shaft 20) is screwed onto the upper portion of the sleeve 21.

As shown in FIG. 4, the housing 3 is held above one exhaust valve 1 by a bracket 24 attached to the rocker shaft 17 with bolts 25. The bracket 24 is supported by a cam bracket 27 by bolts and nuts 26, and each cylinder 8
28 of the housing 3 of the rail extending in the longitudinal direction of the engine
Are linked together by. As shown in FIG. 1, the housing 3 has a cylindrical portion 3a for accommodating the piston member 4, and a rectangular parallelepiped portion 3b for accommodating the spool valve 6 and the check valve 7. The cylindrical portion 3a is located directly above the one exhaust valve 1, and the rectangular parallelepiped portion 3b is located radially outward of the cylindrical portion 3a. An oil intake portion 30 is provided at the outer end of the rectangular parallelepiped portion 3b.
Is provided, and a supply pipe 31 for supplying low-pressure engine oil is connected. This supply pipe 31
Extends in the longitudinal direction of the engine so as to connect the oil supply portions 30 of the respective housings 3, and is connected via an electromagnetic valve 59 to an oil gallery or an oil-dedicated pump serving as an oil supply source. In addition, as a support structure of the housing 3,
As shown in FIG. 3, each cylinder 8 may be held by an independent bracket member 32.

As shown in FIG. 6B, the piston member 4 has a columnar piston head 33, a disc-shaped flange 34 connected below the piston head 33, and a flange. 34
And a rod portion 35 extending downwardly of the above, and these are coaxially and integrally formed. The piston head 33 is formed so as to slide in a vertical cylinder chamber 36 provided in the cylindrical portion 3 a of the housing 3. A piston accommodating hole 37 that opens to the lower surface of the housing is continuously provided below the cylinder chamber 36, and the axial wall surface of the piston accommodating hole 37 engages with the upper surface of the flange portion 34 to determine the upper limit position of the piston member 4. . A piston mounting bolt 39 having a shaft hole 38 through which the rod portion 35 is inserted is screwed into the piston housing hole 37, and the upper end surface of the piston mounting bolt 39 locks the lower surface of the collar portion 34, thereby allowing the piston member 4 to move. Stipulates the lower limit position of. A nut 40 for adjusting the position with respect to the housing 3 (piston accommodating hole 37) is screwed into the lower portion of the piston mounting bolt 39. Further, the return spring 4 is attached to the enlarged diameter portion of the shaft hole 38 of the piston mounting bolt 39.
1 is provided to urge the piston member 4 upward.
The rod portion 35 extends below the piston mounting bolt 39, and its lower end at the lower limit position has the intermediate shaft 20.
The upper end of the exhaust valve 1 is brought into contact with the upper end of the exhaust valve 1, and the exhaust valve 1 is opened by a predetermined minute amount L by this contact. In addition, an air vent hole 42 is formed inside the piston member 4 so as to communicate with the hydraulic circuit 5 as appropriate. The air vent hole 42 is bent from the peripheral surface of the piston head 33 into an L-shape and extends along the axial center. Is penetrated to the lower end of.

As shown in FIGS. 5 and 6, the hydraulic circuit 5 is connected to an upper end of the cylinder chamber 36 and a high hydraulic chamber 43 extending in the radial direction thereof and an extension end of the high hydraulic chamber 43. Spool valve accommodating chamber 44 extending in a direction orthogonal to the lever
And a check valve storage chamber 45 connected to the spool valve storage chamber 44 and parallel to the cylinder chamber 36, and a branched communication passage that appropriately connects the oil intake portion 30, the spool valve storage chamber 44, and the check valve storage chamber 45. And 46. That is, the engine oil that has entered the oil intake portion 30 is guided to the spool valve accommodating chamber 44, and at the same time, the check valve 7 and the spool valve 6
The pressure is guided to the upper part of the cylinder chamber 36 via the pressure and the pressure is applied to the piston head 33. The passage of the high hydraulic chamber 43 and the pressure receiving surface 33a of the piston head 33
Is configured to push down the intermediate shaft 20 by a predetermined stroke against the urging force of the return spring 41 when low-pressure engine oil is supplied. Further, at the connection position with the high hydraulic pressure chamber 43, which is the center of the spool valve accommodating chamber 44 in the longitudinal direction, an enlarged diameter portion 47 having an appropriately enlarged diameter is formed.
Are formed. In addition, in the spool valve accommodating chamber 44, an oil drain port 48 is formed near the end on the side opposite to the oil intake portion 30 and opens radially outward thereof.

The check valve 7 is held by a check valve mounting bolt 49 screwed into the check valve accommodating chamber 45 and has an oil supply hole 7a connected to the communication passage 46. A ball 50 is provided at the end of the oil supply hole 7a so that engine oil can pass through only in the direction from the oil intake portion 30 to the spool valve accommodating chamber 44. As shown in FIG. 5, the spool valve 6 is a columnar body having a first groove 51 and a second groove 52 at a predetermined interval on the outer circumference, and is arranged in the spool valve accommodating chamber 47 along the longitudinal direction thereof. It is slidably accommodated. Further, inside the spool valve 6, a first through hole 53 penetrating along the axial center of the spool valve 6 and a first through hole which is orthogonal to the through hole 53 at the position of the second groove 52 and is parallel to the extending direction of the high hydraulic chamber 43. Two through holes 54 are formed. On the other hand, stoppers 55 and 56 that define the sliding range of the spool valve 6 are fitted on both ends of the spool valve accommodating chamber 44, respectively. Between the first stopper 55 on the oil drain 48 side and the shaft-side end surface of the spool valve 6, the spool valve 6 is urged to the opposite side, that is, the second stopper 56 on the oil supply side. A return spring 57 is provided.

Then, as shown in FIGS. 8 and 9, the return valve 57 causes the spool valve 6 to move to the second stopper 5.
In the state of being pressed against 6, the second groove 52 is located on the extension of the high hydraulic chamber 43, and the oil in the high hydraulic chamber 43 passes between the through holes 53, 54 and the first stopper 55, The oil is discharged from the oil drain port 48 to the outside of the housing (open to the atmosphere). Therefore, in this state, the hydraulic pressure does not act on the piston head 33 of the piston member 4,
It is pushed up to the upper limit position by the return spring 41. That is, as shown in FIG. 7, the valve body 11 of the exhaust valve 1
Is seated on the open end 10 of the exhaust port 9, the lower end of the rod portion 35 of the piston member 4 is separated from the upper end of the intermediate shaft 20 by a predetermined small distance S. At the upper limit position of the piston member 4, the pressure receiving surface 33a of the piston head 33 and the high hydraulic chamber 4
A gap for allowing oil to pass is formed with the upper wall surface of No. 3, and the upper opening of the air vent hole 42 faces the high hydraulic pressure chamber 43 and communicates therewith. A step portion 58 is formed on the end surface of the spool valve 6 on the second stopper 56 side, and even when the spool valve 6 is in contact with the second stopper 56, the step portion 58 faces the communication passage 46. Has been done. On the other hand, as shown in FIGS. 5 and 6, in the state where the spool valve 6 is pressed against the first stopper 55 against the return spring 57 by the hydraulic pressure of the engine oil, the first groove 51 is moved to the high hydraulic chamber 43. The engine oil is positioned so as to communicate with each other, and the engine oil is supplied to the high hydraulic pressure chamber 43 through the check valve 7 and the enlarged diameter portion 47. That is, this hydraulic pressure causes the piston member 4 to move down to the lower limit position and contact the exhaust valve 1 via the intermediate shaft 20 at a predetermined valve opening position.

In addition, as shown in FIG. 11, a solenoid valve 59 is provided in the oil supply system, and is turned on / off by operating a switch 60 provided in the driver's seat, so that the oil is sent by an engine oil gallery or a dedicated pump. The obtained oil is supplied or stopped to the oil intake portion 30 of the housing 3 arranged in each cylinder 8. The operation switch 60 is used when the engine brake is used.
In other words, it may be configured to be "ON" only when the accelerator pedal is not depressed.

When the engine braking device constructed as described above is used to increase the engine braking force, the operation switch 60 is turned on to supply engine oil to the oil intake portion 30 of the housing 3. This hydraulic pressure acts on the step portion 58 of the spool valve 6,
The spool valve 6 is slid until it abuts the first stopper 55, and the first groove 51 is positioned so as to communicate with the high hydraulic chamber 43. The engine oil now enters the high hydraulic chamber 43 via the check valve 7 and the spool valve 6. Since it is highly possible that the oil that first flows in contains air, this oil is removed from the air vent hole 42 in the piston member 4.
Thus, it is discharged from the gap S between the rod portion 35 and the intermediate shaft 20. Subsequently, when hydraulic pressure acts on the piston head 33, the piston member 4 is pushed down, and the air vent hole 4
2 is blocked by the wall surface of the cylinder chamber 36, and abuts on the exhaust valve 1 immediately before closing through the intermediate shaft 20,
The rocker arm 15 is held in a slightly depressed state regardless of the rocking position. That is, as shown in FIG. 10, the exhaust valve 1 is slightly opened by the amount (L) of the downward stroke of the piston member 4 minus the clearance S, and the compression stroke and expansion stroke including the overlap timing at the top dead center are included. Also, the cylinder 8 is always opened. With this, as shown in FIG. 12, the expansion pressure becomes significantly lower than the compression pressure, and the piston of the engine moving by inertia is decelerated by the negative work increasing accordingly. That is, as shown in FIG. 13, a brake effective pressure that provides greater braking performance than the exhaust brake is obtained. A large force in the valve closing direction is applied to the piston member 4 due to the compression pressure in the cylinder 8. However, when the piston member 4 is pushed down, the oil supply side of the high hydraulic chamber 43 is closed by the check valve 7. Since it is in a hermetically closed state due to the above, a high-pressure reaction force is rapidly generated in the high hydraulic chamber 43, and by maintaining this high pressure, the exhaust valve 1 is blocked from closing and the exhaust valve 1 is kept at a predetermined level. Held in the lift position.

When it is not necessary to increase the engine brake and the operation switch is turned "OFF", the supply of engine oil is stopped and the spool valve 6 is returned to the return spring 5
It slides by 7 and is pressed against the second stopper 56. As a result, the second groove 52 communicates with the high hydraulic pressure chamber 43 and the oil returns to the through holes 53 and 54, but the supply side of the first through hole 53 is blocked by the second stopper 56. Therefore, backflow to the oil intake is blocked, and the oil drain port 4
It is discharged to 8. The high hydraulic chamber 43 is now in a depressurized state, the piston member 4 is raised to the upper limit position by the return spring 41, and is separated from the intermediate shaft 20,
The exhaust valve 1 is returned to a position that does not interfere with the opening / closing operation in the normal combustion cycle.

As described above, the piston member 4 is provided in the housing 3 arranged above the exhaust valve 1, and low-pressure engine oil is supplied to the hydraulic circuit 5 in the housing 3 to operate the piston member 4 to exhaust the gas. Since the valve 1 is appropriately placed in the lift position and the spool valve 6 and the check valve 7 are used to maintain the high hydraulic pressure and supply and discharge the oil, the compression pressure in the cylinder 8 is released with a simple and compact structure. It is possible to obtain an increase in engine braking force. That is, the piston for generating hydraulic pressure is not required, and it is possible to prevent an increase in the overall height of the engine and an increase in weight, thereby achieving cost reduction. Further, since the lower limit position of the piston member 4 can be adjusted by the piston mounting valve 39, the normally open lift amount of the exhaust valve 1 can be easily changed.
Since the piston member 4 is located coaxially with the exhaust valve 1 and pushes it, the rocker arm 1
The valve operating system such as No. 5 is not subjected to any load due to the compression pressure releasing operation, and does not require a large change, so that the versatility is improved.

When the engine brake device of the present invention is used in combination with an exhaust brake, the compression start pressure can be increased by the exhaust gas backflow to increase the compression pressure by opening the exhaust valve when the intake valve is opened. It is possible to increase the portion (work) surrounded by the expansion pressure curve and the compression pressure curve by the normally open valve shown. Therefore, it is preferably used in combination with the exhaust brake.

[0018]

In summary, according to the present invention, the engine braking force can be increased by releasing the compression pressure in the cylinder, the overall height of the engine can be prevented from increasing and the weight can be prevented from being reduced by the simple and compact structure, and the cost can be reduced. It has the excellent effect of

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of an engine braking device showing an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a plan view showing another embodiment of FIG.

FIG. 4 is a side view showing the whole of FIG.

5A and 5B are views showing a main part of FIG. 1, in which FIG. 5A is a plan view and FIG. 5B is a cross-sectional view of the main part.

6A and 6B are diagrams showing a main part of FIG. 1, in which FIG. 6A is a front view and FIG. 6B is a sectional view thereof.

FIG. 7 is a side sectional view of an essential part for explaining the operation of FIG.

8A and 8B are views showing a main part of FIG. 7, in which FIG. 8A is a front view and FIG. 8B is a cross-sectional view of the main part.

9 is a front view showing a main part of FIG. 7. FIG.

FIG. 10 is a valve opening timing diagram of the exhaust valve for explaining the operation of the present invention.

FIG. 11 is a circuit diagram showing the oil supply system of FIG.

FIG. 12 is a diagram showing a relationship between in-cylinder pressure and cylinder volume showing a brake cycle curve of the present invention.

FIG. 13 is a relationship diagram between the effective brake pressure and the engine speed showing the braking performance characteristics of the present invention.

[Explanation of symbols]

 1, 2 Exhaust valve 3 Housing 4 Piston member 5 Hydraulic circuit 6 Spool valve (valve means) 7 Check valve (valve means)

Claims (1)

[Claims] 1. A piston member movably provided in a housing disposed above the exhaust valve, and a piston member formed in the housing and supplied with low hydraulic pressure to operate the piston member to appropriately lift the exhaust valve. And a valve means provided in the hydraulic circuit for appropriately closing the hydraulic circuit when supplying the low hydraulic pressure to maintain the high hydraulic pressure for holding the lift and releasing the high hydraulic pressure by stopping the supply. An engine braking device characterized by comprising: