WO2015098219A1

WO2015098219A1 - Exhaust valve drive device and internal combustion engine equipped with same

Info

Publication number: WO2015098219A1
Application number: PCT/JP2014/075754
Authority: WO
Inventors: 石田　裕幸; 村田　聡; 直樹奥村; 晃洋三柳; 順之溝口; 潤柳; 浩二江戸
Original assignee: 三菱重工業株式会社
Priority date: 2013-12-25
Filing date: 2014-09-26
Publication date: 2015-07-02
Also published as: KR101727872B1; KR20160147070A; JP6092090B2; CN105814290B; CN105814290A; KR20160067918A; JP2015124631A

Abstract

The objective of the present invention is to enable the timing for closing an exhaust valve to be changed by means of a simple configuration suitable for an internal combustion engine for a ship, and to adapt the characteristic of the internal combustion engine to the operating state. This exhaust valve drive device (1) is equipped with: a piston (7) provided on an exhaust valve (5) of an internal combustion engine; a cylinder (9) in which the piston (7) is housed; an oil pressure supply device (13) that is driven by a cam (35) and intermittently supplies oil pressure to the cylinder (9) with a prescribed valve-opening timing, thereby pressing the piston (7) and opening the exhaust valve (5); an air spring device (15) that biases the exhaust valve (5) in the direction of closing; a convex part (7a), which is formed on the top surface of the piston (7), and the top surface area of which is smaller than the cross-sectional surface area of the piston (7); a concave part (9a), which is formed in the ceiling surface of the cylinder (9), and into which the convex part (7a) is inserted with a gap therebetween when the piston (7) rises; an actuator (17) that changes the depth of the concave part (9a); and a control device (19) that controls the actuator (17).

Description

Exhaust valve drive device and internal combustion engine equipped with the same

The present invention is a hydraulically operated exhaust valve drive apparatus in which a piston provided at a shaft end of an exhaust valve is pressed by a hydraulic pressure of hydraulic fluid discharged from a plunger driven by a cam to open the exhaust valve. And an internal combustion engine provided with the same.

This type of exhaust valve drive device can be controlled by operating the hydraulic pressure so that the open / close timing of the exhaust valve becomes optimal in accordance with the operation load of the internal combustion engine.
For example, in a large marine low-speed two-stroke cycle diesel engine, by delaying the timing at which the exhaust valve closes during high load operation, the internal cylinder pressure can be prevented from becoming too high for compression of the internal combustion engine. It can be enhanced. In addition, it is possible to reduce the speed at which the exhaust valve closes and prevent the exhaust valve from being hit against the valve seat, thereby suppressing damage, wear and the like of the exhaust valve and the valve seat.

On the other hand, in a general mechanical exhaust valve drive device in which the exhaust valve is directly driven by the cam, the movement of the exhaust valve depends on the profile of the cam, so to change the opening / closing timing of the exhaust valve , And requires a complicated configuration, such as providing a plurality of cams having different profiles, or interposing a rocker arm capable of changing the lever ratio. Therefore, it is not preferable as an exhaust valve drive device for a marine internal combustion engine that wants to avoid a fault at sea.

Patent Document 1 discloses a hydraulically operated exhaust valve drive device in which the timing at which the exhaust valve closes is delayed as described above. The same document, Fig. As shown in FIG. 1, the piston 10 provided at the axial end of the exhaust valve 5 and pressing the exhaust valve 5 in the valve opening direction is a two-stage piston provided with a large diameter portion and a small diameter portion. The cylinder 4 with which it slides is also a two-stage cylindrical shape provided with a large diameter bore and a small diameter bore.

The hydraulic oil pumped from the hydraulic pump driven by the cam is supplied to the small diameter bore of the cylinder 4 through the oil passage 11, and the hydraulic pressure depresses the piston 10 to open the exhaust valve 5. When the exhaust valve 5 is closed, the exhaust valve 5 is closed at a high speed until the small diameter portion of the piston 10 enters the small diameter bore of the cylinder 4, and the small diameter portion of the piston 10 enters the small diameter bore of the cylinder 4 When it begins to rush, the hydraulic oil sealed between the small diameter portion of the piston 10 and the large diameter portion of the cylinder 4 flows into the small diameter portion of the cylinder 4 through the gap between the cylinder 4 and the piston 10 At this time, the flow resistance at this time acts as a buffer on the movement of the piston 10, and the closing speed of the exhaust valve 5 decreases. For this reason, the exhaust valve 5 seats at a relatively slow speed and is protected from the impact due to the collision with the valve seat.

Japanese Patent Application Laid-Open No. 1-244111

However, in the exhaust valve drive device described in Patent Document 1, the degree to which the timing of closing the exhaust valve 5 is delayed is constant, and for example, the timing of closing the exhaust valve 5 is not delayed or delayed. I could not For this reason, it was difficult to change the characteristics of the internal combustion engine to match various operating conditions.

The present invention has been made in view of such circumstances, and it is possible to change the timing at which the exhaust valve closes with a simple configuration suitable for a marine internal combustion engine, and to adapt the characteristics of the internal combustion engine to the operating situation. Provided are an exhaust valve drive device and an internal combustion engine provided with the same.

In order to solve the above-mentioned subject, an exhaust valve drive of the present invention and an internal combustion engine provided with the same adopt the following means.
According to a first aspect of the present invention, a hydraulic pressure is intermittently supplied to the cylinder at a predetermined valve opening timing by being driven by a piston provided in an exhaust valve of an internal combustion engine, a cylinder in which the piston is accommodated, and a cam. A hydraulic pressure supply means for pressing the piston to open the exhaust valve, a valve closing means for biasing the exhaust valve in the valve closing direction, and a piston formed on the top surface of the piston A protrusion having a top area smaller than a cross sectional area, a recess formed on a ceiling surface of the cylinder and into which the protrusion is inserted via a gap when the piston is lifted, and an actuator for changing the depth of the recess And control means for controlling the actuator.

According to the above configuration, when the hydraulic pressure supply means is driven by the cam, the hydraulic pressure is supplied to the cylinder at a predetermined valve opening timing, whereby the piston inside the cylinder is pressed and the exhaust valve is opened. In addition, when the hydraulic pressure to the cylinder decreases, the exhaust valve is closed by the biasing force of the valve closing biasing means.

When the exhaust valve is closed, the piston moving integrally with the exhaust valve advances to the back of the cylinder, and at a high speed until the projection formed on the top surface of the piston is inserted into the recess formed on the cylinder ceiling surface The exhaust valve closes. Then, when the projection of the piston starts to penetrate into the recess of the cylinder, the hydraulic oil sealed between the projection and the cylinder will flow out of the cylinder through the narrow gap between the projection and the recess. The large flow resistance at this time acts as a buffer on the movement of the piston and reduces the closing speed of the exhaust valve. For this reason, the exhaust valve seats at a relatively slow speed and is protected from impact due to collision with the valve seat.

The recess of the cylinder can be varied in depth by the actuator and the control means. When the depth of the recess is small, the amount of hydraulic oil sealed between the protrusion and the cylinder decreases, so the shock absorbing action of the piston decreases and the exhaust valve is closed at the valve closing timing determined by the cam profile. Close, close at a relatively fast timing.

Further, when the depth of the recess is large, the amount of hydraulic oil sealed between the protrusion and the cylinder increases, so that it takes time to discharge the oil, and the shock absorbing action of the piston becomes large. Therefore, the exhaust valve closes at a timing later than the valve closing timing determined by the cam profile.

Thus, the timing at which the exhaust valve closes can be made earlier or later by changing the depth of the recess provided on the cylinder side, so that the characteristics of the internal combustion engine can be adapted to the operating situation.

In addition, since the change of the timing at which the exhaust valve closes can be achieved with a simple structure in which the depth of the recess provided in the cylinder is changed, it is suitable for a marine internal combustion engine that preferably has a simple structure.

In the above configuration, preferably, the control means controls the actuator such that the depth of the recess increases as the load on the internal combustion engine increases.
According to this configuration, as the load on the internal combustion engine increases, the timing at which the exhaust valve closes is delayed. Thus, the durability of the internal combustion engine can be enhanced by preventing the compression pressure of the in-cylinder gas from becoming too high during high load operation.

According to a second aspect of the present invention, a hydraulic pressure is intermittently supplied to the cylinder at a predetermined valve opening timing by being driven by a piston provided in an exhaust valve of an internal combustion engine, a cylinder in which the piston is accommodated, and a cam. Hydraulic pressure supply means for pressing the piston to open the exhaust valve, a valve closing biasing means for biasing the exhaust valve in the valve closing direction, and a leak for releasing the hydraulic pressure generated by the hydraulic pressure supply means It is an exhaust valve drive device which comprises a passage, flow rate adjustment means for changing the passage area of the leak passage, and control means for controlling the flow rate adjustment means.

According to the above configuration, as in the first aspect, when the hydraulic pressure supply means is driven by the cam, the hydraulic pressure is supplied to the cylinder at a predetermined valve opening timing, whereby the piston inside the cylinder is pressed and the exhaust valve Is opened. Further, when the hydraulic pressure supply to the cylinder is interrupted, the exhaust valve is closed by the biasing force of the valve closing and biasing means.

Part of the hydraulic oil (hydraulic pressure) supplied from the hydraulic pressure supply means leaks to the outside of the hydraulic path from the flow rate adjusting means provided in the leak passage. As a result, the amount of oil returned from the cylinder to the hydraulic pressure supply means at the time of closing the exhaust valve is smaller than the amount of oil pumped to the cylinder at the time of pressurization by the hydraulic pressure supply means. Can be returned to the inside of the cylinder so that the exhaust valve can be closed reliably.

By controlling the flow rate adjustment means, it is possible to adjust the amount of leakage of the hydraulic oil supplied from the hydraulic pressure supply means to the outside. When the leak amount is reduced, the closing speed of the exhaust valve is decreased, and when the leak amount is increased, the closing speed of the exhaust valve is increased.

As described above, by providing the flow rate adjustment means in the leak passage for releasing the hydraulic pressure generated by the hydraulic pressure supply means to the outside, the timing at which the exhaust valve closes can be made earlier or later. It can be adapted.

Moreover, since the change of the timing at which the exhaust valve closes can be achieved with a simple structure in which the leak path and the flow rate adjusting means are provided in the hydraulic path, cylinder, etc., it is suitable for marine internal combustion engines that preferably have a simple configuration. .

In the above configuration, preferably, the control means controls the flow rate adjusting means such that the passage area of the leak passage decreases as the load on the internal combustion engine increases.
According to this configuration, the timing at which the exhaust valve closes is delayed as the load on the internal combustion engine increases, and the compression pressure of the in-cylinder gas is prevented from becoming too high during high load operation to improve the durability of the internal combustion engine. it can.

A third aspect of the present invention is an internal combustion engine provided with the exhaust valve drive device described in any of the above.

As a result, it is possible to change the timing at which the exhaust valve closes, and to adapt the characteristics of the internal combustion engine to the operating condition, while having a simple configuration suitable for a marine internal combustion engine.

As described above, according to the exhaust valve drive device according to the present invention and the internal combustion engine provided with the same, the timing at which the exhaust valve closes can be changed by a simple configuration suitable as a marine internal combustion engine. The characteristics of the internal combustion engine can be adapted to the operating conditions, and the reliability and durability of the internal combustion engine can be enhanced, and also contributing to fuel saving and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows the exhaust valve drive device which concerns on 1st Embodiment of this invention. FIG. 2 is an enlarged view of a portion II of FIG. 1, in which (a) shows a state before the projection of the piston is inserted into the recess of the cylinder, and (b) shows a state where the projection of the piston starts to be inserted into the recess of the cylinder It is a longitudinal cross-sectional view which shows. It is a figure which shows the other shape example of the convex part of a piston, and the recessed part of a cylinder, (a) shows the state before the convex part of a piston is inserted in the recessed part of a cylinder, (b) shows the convex part of a piston It is a longitudinal cross-sectional view which shows the state which began to be inserted in the recessed part of a cylinder. (A) is a graph showing a cam lift amount in the first embodiment, (b) a working hydraulic pressure, and (c) a exhaust valve lift amount. It is a schematic block diagram which shows the exhaust valve drive device which concerns on 2nd Embodiment of this invention. (A) is a graph showing a cam lift amount in the second embodiment, (b) a working hydraulic pressure, and (c) a exhaust valve lift amount.

Hereinafter, an embodiment of an exhaust valve drive device according to the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a schematic configuration view showing an exhaust valve drive device according to a first embodiment of the present invention. The exhaust valve drive device 1 is provided in a diesel engine (internal combustion engine) for a ship main engine.

A diesel engine for ship's main engine (hereinafter referred to as "diesel engine") is, for example, a low-speed two-stroke cycle engine, and employs a uniflow type which scavenges unidirectionally so as to supply air from below and exhaust upward. ing. The output from the diesel engine is directly or indirectly connected to the screw propeller via a propeller shaft (not shown).

As shown in FIG. 1, the exhaust valve drive device 1 includes an exhaust valve 5 for opening and closing an exhaust flow path formed in a cylinder head 3 of a diesel engine, a piston 7 provided for the exhaust valve 5, and a piston The cylinder 9 in which 7 is accommodated, the hydraulic path 11 for supplying hydraulic pressure to the cylinder 9 and the hydraulic supply device (hydraulic supply means) 13, and an air spring for biasing the exhaust valve 5 in the valve closing direction (upward in FIG. 1) The apparatus (valve closing biasing means) 15, the actuator 17 and the control device (control means) 19 are provided.

The piston 7 is connected to the upper end of the shaft portion 5 a of the exhaust valve 5 extending in the vertical direction, and reciprocates in the cylinder 9 in the vertical direction as the exhaust valve 5 is opened and closed. One end 11 a of the hydraulic path 11 is connected to the hydraulic chamber 21 formed by the piston 7 and the cylinder 9. Further, an orifice path 25 extends from the hydraulic chamber 21. The orifice path 25 is provided with an orifice 27 which is a fixed throttle. The exhaust valve 5 is always urged in the valve closing direction (upward) by the air spring device 15.

The hydraulic pressure supply device 13 includes a plunger 31, a cylinder 33, and a cam 35. The plunger 31 is slidably inserted into the cylinder 33, and is in a pressure chamber 37 formed by the plunger 31 and the cylinder 33, which is always urged in the direction (downward) from the cylinder 33 by urging means not shown. Is connected to the other end 11 b of the hydraulic pressure passage 11.

A cam roller 41 is supported by a lower portion of the plunger 31 via a connecting shaft 39. The cam roller 41 rolls on the outer peripheral surface of the cam 35 disposed below, that is, the cam profile. The cam 35 is integrally provided on a cam shaft 43 that rotates in synchronization with the crankshaft of the diesel engine.

In the hydraulic path 11, a low pressure hydraulic oil supply path 45 is branched from a branch point 11c. A low pressure hydraulic oil source (not shown) is connected to the low pressure hydraulic oil supply path 45 via a check valve 47, and an oil pressure serving as a base used when opening and closing the exhaust valve 5 is supplied. When the hydraulic pressure in the hydraulic path 11 falls below a predetermined value, the check valve 47 is opened and the hydraulic oil (hydraulic pressure) is replenished from the low pressure hydraulic oil supply path 45. Further, the check valve 47 is closed when the pressure in the hydraulic path 11 is equal to or higher than a predetermined value, that is, at the time of the pressure stroke by the plunger 31.

As also shown in FIGS. 2 (a) and 2 (b), a cylindrical convex 7a is formed at the center of the top of the piston 7. As shown in FIG. The top area of the convex portion 7 a is smaller than the cross sectional area of the piston 7. For example, if the diameter of the piston 7 is 80 mm, the diameter of the convex portion 7a may be about 50 mm, and the height from the top surface of the convex portion 7 a may be about 60 mm. Or it is not limited to the ratio of this diameter.

On the other hand, on the ceiling surface of the cylinder 9, a recess 9a in the form of a cylindrical hole is formed at the center. The inner diameter of the recess 9a is set so that the protrusion 7a of the piston 7 is inserted through a gap of several millimeters when the piston 7 is lifted.

The depth h of the recess 9a can be changed in the range from zero to the same height as the height of the protrusion 7a. For example, the structure of the top portion of the cylinder 9 has a structure in which a cylindrical movable member 9c is densely provided around the cylindrical fixed member 9b located at the center and can be relatively moved up and down. A space below the fixed member 9b and on the inner peripheral side of the movable member 9c is a recess 9a. The hydraulic path 11 is open at the lower surface of the fixing member 9b.

Then, by moving the movable member 9c up and down with the actuator 17 shown in FIG. 1, the depth h of the recess 9a can be changed. For example, the movable member 9c is moved up and down by rotating the movable member 9c relative to the fixed member 9b with the power of the actuator 17 with a screw pair between the outer peripheral surface of the fixed member 9b and the inner peripheral surface of the movable member 9c. It is conceivable to change the depth of the recess 9a by moving it to. Note that a screw pair may be provided between the inner peripheral surface of the cylinder 9 and the outer peripheral surface of the movable member 9c.

Further, the control device 19 shown in FIG. 1 controls the actuator 17 to set the vertical position of the movable member 9c. For example, the controller 19 controls the actuator 17 so that the depth of the recess 9a increases as the load on the diesel engine increases.

Next, the operation of the exhaust valve driving device 1 configured as described above will be described.
When the cam 35 (cam shaft 43) of the hydraulic pressure supply device 13 rotates, the cam roller 41 moves up and down while rotating along the cam profile of the cam 35, and the up and down movement moves the plunger 31 through the connecting shaft 39. Slide up and down inside.

When the plunger 31 slides upward in the cylinder 33, the hydraulic oil filled in the pressure chamber 37 is pressurized, and this hydraulic oil passes through the hydraulic path 11 and the hydraulic chamber 21 between the cylinder 9 and the piston 7 It is pumped to The volume of the hydraulic chamber 21 is expanded by the hydraulic pressure of the hydraulic fluid, the piston 7 is pushed down against the biasing force of the air spring device 15, and the exhaust valve 5 is opened. The opening amount of the exhaust valve 5 is determined by the height of the cam 35 from the base circle 35 a.

In addition, when the cam 35 pivots downward, the plunger 31 is pushed back by the biasing means (not shown) and the hydraulic pressure applied to the pressure chamber 37 and the hydraulic chamber 21 is weakly supplied from the low pressure hydraulic oil supply path 45 Drop to base hydraulic pressure. Therefore, the exhaust valve 5 is pushed up and closed by the biasing force of the air spring device 15, whereby the piston 7 ascends to minimize the volume of the hydraulic chamber 21 and the hydraulic oil in the hydraulic chamber 21 Then, the pressure is returned to the pressure chamber 37 of the cylinder 33.

As described above, the hydraulic pressure supply device 13 is driven by the cam 35 to intermittently supply the hydraulic pressure to the cylinder 9 at a predetermined valve opening timing, and presses the piston 7 to open the exhaust valve 5.

When pressurized by the plunger 31, a small amount of hydraulic fluid in the hydraulic chamber 21 is discharged from the orifice 27 of the orifice path 25 to the outside of the hydraulic path 11. Thus, the amount of oil returned from the hydraulic chamber 21 to the pressurizing chamber 37 when the exhaust valve 5 is closed is smaller than the amount of oil sent from the pressurizing chamber 37 to the hydraulic chamber 21 when pressurized by the plunger 31 The exhaust valve 5 can be reliably closed by properly raising 7 to the top of the cylinder 9. The hydraulic oil discharged from the orifice 27 is replenished from the low pressure hydraulic oil supply path 45 to the hydraulic path 11 when the plunger 31 is not pressed by the cam 35.

FIG. 4 is a graph showing the relationship between the lift amount (a) of the cam 35, the hydraulic pressure (b) in the hydraulic pressure chamber 21, and the lift amount (c) of the exhaust valve 5. In FIGS. 4B and 4C, the solid line indicates the hydraulic pressure and the exhaust valve lift when the depth h of the recess 9a shown in FIG. 2A is zero.

When the cam lift amount increases according to the profile of the cam 35 at time t0 and the plunger 31 starts to be pushed up, the hydraulic pressure of the hydraulic chamber 21 starts to rise from the base pressure. When the cam lift amount reaches the maximum value at time t1, the plunger 31 is pushed up to the top dead center, and the hydraulic pressure reaches the maximum value, at time t2, the hydraulic pressure of the hydraulic chamber 21 is the biasing force of the air spring device 15 and Overcoming the pressure in the cylinder and pushing down the piston 7.

As a result, the lift amount of the exhaust valve 5 increases, and the exhaust valve 5 is fully opened at time t3. At this time, as the piston 7 is pushed down, the volume of the hydraulic chamber 21 expands, so the hydraulic pressure in the hydraulic chamber 21 sharply decreases, but the hydraulic pressure necessary to keep the exhaust valve 5 open is maintained. Be done. Therefore, while the plunger 31 is maintained at the top dead center according to the profile of the cam 35, the lift amount of the exhaust valve 5 is also maintained at the maximum, and the exhaust valve 5 is maintained in the open state.

When the cam lift amount decreases according to the profile of the cam 35 at time t5 and the plunger 31 starts to descend, the hydraulic pressure of the hydraulic chamber 21 also begins to decrease. When the hydraulic pressure falls below the predetermined value, the biasing force of the air spring device 15 and the pressure in the cylinder are overcome, and the lift amount of the exhaust valve 5 starts to be reduced by pushing up the piston 7 from time t6. When the lift amount of the cam 35 becomes zero and the plunger 31 is lowered to the bottom dead center, the exhaust valve 5 is fully closed at time t7. Also, the hydraulic pressure of the hydraulic path 11 returns to the base pressure.

As shown in FIG. 2A, when the movable member 9c is lowered relative to the fixed member 9b of the cylinder 9 to form a recess 9a of a depth h, the exhaust valve 5 is closed when the exhaust valve 5 is closed. As the integrally moving piston 7 advances to the back of the cylinder 9, the volume of the hydraulic chamber 21 is reduced, and the hydraulic oil filled in the hydraulic chamber 21 is discharged from the hydraulic path 11 and returned to the pressurizing chamber 37.

At this time, the hydraulic oil in the hydraulic chamber 21 smoothly flows into the hydraulic path 11 until the convex portion 7 a of the piston 7 is inserted into the concave portion 9 a of the cylinder 9. The exhaust valve 5 is closed at a high speed. Then, as shown in FIG. 2B, when the convex portion 7a starts to be inserted into the concave portion 9a, the hydraulic pressure chamber 21 is formed in the room 21a formed around the convex portion 7a and inside the concave portion 9a. It is divided into rooms 21b.

The hydraulic oil in the room 21b is smoothly discharged from the hydraulic path 11 as it is, but the hydraulic oil sealed in the room 21a flows into the room 21b through the narrow gap between the room 21a and the room 21b. Are discharged from the hydraulic pressure path 11. For this reason, a large flow resistance accompanied by the hydraulic oil passing through the gap acts as a buffer action (cushion action) on the movement of the piston 7, the valve closing speed of the exhaust valve 5 decreases, and the exhaust valve 5 completely closes. Timing is delayed.

If the depth h of the recess 9a is small, the amount of oil that has to flow from the room 21a to the room 21b decreases, so the time during which the cushioning action is added to the upward movement of the piston 7 becomes short. Therefore, the exhaust valve 5 closes at a relatively early timing close to the valve closing timing determined by the profile of the cam 35.

In addition, as the depth h of the recess 9a increases, the amount of oil that must flow into the room 21b from the room 21a increases, so it takes time to discharge the oil, and the upward movement of the piston 7 is buffered. The time to join will also be longer. Therefore, the exhaust valve 5 is closed at a timing largely delayed from the valve closing timing determined by the profile of the cam 35.

Thus, when the convex portion 7a of the piston 7 is inserted into the concave portion 9a of the cylinder 9 at the end of the upward stroke of the piston 7, a flow resistance of the hydraulic oil sealed in the chamber 21b is generated. The pressure in the chamber 21a (room 21a) rises sharply as shown by broken lines P1 and P2 in FIG. 4 (b). The broken line P1 indicates the pressure increase rate when the depth h of the recess 9a is small, and the broken line P2 indicates the pressure increase rate when the depth h of the recess 9a is large.

Thus, since the pressures P1 and P2 in the hydraulic pressure chamber 21 rapidly increase, as shown by the broken lines L1 and L2 in FIG. 4C, while the exhaust valve 5 is closing, the decreasing rate of the lift amount is moderate. It becomes inclination. The decreasing rate of the lift amount of the exhaust valve 5 is indicated by a broken line L1 when the pressure in the hydraulic chamber 21 is P1, and is indicated by a broken line L2 when the pressure in the hydraulic chamber 21 is P2. That is, as the depth h of the recess 9a becomes larger, the time until the exhaust valve 5 completely closes becomes longer (the valve closing timing becomes later). For this reason, the exhaust valve 5 is seated on the valve seat at a relatively slow speed, and is protected from an impact due to a collision with the valve seat.

Thus, by changing the depth of the recess 9a provided on the cylinder 9 side, the timing at which the exhaust valve 5 closes is made closer to the valve closing timing defined by the cam profile of the cam 35 or the valve closing specified. The characteristics of the diesel engine can be adapted to the operating situation, as it can be later than the timing.

Further, changing the timing at which the exhaust valve 5 closes changes the depth of the recess 9a provided in the cylinder 9, that is, moves the movable member 9c relative to the fixed member 9b of the cylinder 9 in the axial direction by the actuator 17. Since this can be achieved with such a simple structure, a structure suitable for marine diesel engines where a simple structure is desirable can be obtained.

Furthermore, the controller 19 controls the actuator 17 such that the depth h of the recess 9a increases as the load on the diesel engine increases. Therefore, as the load on the diesel engine increases, the timing at which the exhaust valve 5 closes is delayed. As a result, it is possible to prevent the compression pressure of the in-cylinder gas from becoming too high during high load operation, and to improve the durability of the diesel engine.

FIGS. 3A and 3B are longitudinal sectional views showing another example of the shape of the convex portion 7 a of the piston 7 and the concave portion 9 a of the cylinder 9.
Here, a convex portion 7 a provided on the top surface of the piston 7 is formed to cylindrically protrude from the periphery of the top surface of the piston 7. On the other hand, the recess 9a provided on the ceiling surface of the cylinder 9 is formed as a cylindrical recess around the ceiling surface. That is, the radial inside / outside positional relationship between the convex portion 7a and the concave portion 9a shown in FIGS. 2 (a) and 2 (b) is reversed.

The depth h of the recess 9a can be changed in the range from zero to the same height as the height of the protrusion 7a. For example, the cylindrical movable member 9d provided at the center of the top of the cylinder 9 can move up and down, and when the movable member 9d protrudes from the ceiling surface of the cylinder 9, the inner peripheral surface of the cylinder 9 A recess 9a is formed between the and the outer peripheral surface of the movable member 9d.

The outer diameter of the movable member 9d is set such that the convex portion 7a of the piston 7 surrounds the periphery of the movable member 9d with a gap of about several millimeters when the piston 7 ascends. The movable member 9d is driven up and down by the actuator 17 shown in FIG. 1, whereby the depth h of the recess 9a is changed. The hydraulic path 11 opens at the lower surface of the movable member 9d.

As shown in FIG. 3A, when the movable member 9d of the cylinder 9 is lowered to form the recess 9a of the depth h, the piston 7 which moves integrally with the exhaust valve 5 when the exhaust valve 5 is closed. By advancing to the back of the cylinder 9, the volume of the hydraulic pressure chamber 21 is reduced, and the hydraulic oil filled in the hydraulic pressure chamber 21 is discharged from the hydraulic pressure passage 11 and returned to the pressure chamber 37.

At this time, the hydraulic oil in the hydraulic chamber 21 smoothly flows into the hydraulic path 11 until the convex portion 7 a of the piston 7 is inserted into the concave portion 9 a of the cylinder 9. The exhaust valve 5 is closed at a high speed. Then, as shown in FIG. 3B, when the convex portion 7a starts to be inserted into the concave portion 9a, the hydraulic pressure chamber 21 is formed in the chamber 21a formed on the inner peripheral side of the convex portion 7a and inside the concave portion 9a. Divided into rooms 21b.

The hydraulic oil in the room 21a is smoothly discharged from the hydraulic path 11 as it is, but the hydraulic oil sealed in the room 21b flows into the room 21a through the narrow gap between the room 21b and the room 21a. Are discharged from the hydraulic pressure path 11. For this reason, a large flow resistance accompanied by the hydraulic oil passing through the gap acts as a buffer action (cushion action) on the movement of the piston 7, the valve closing speed of the exhaust valve 5 decreases, and the exhaust valve 5 completely closes. Timing is delayed. As a result, the exhaust valve 5 can be protected from impact due to collision with the valve seat, and the characteristics of the diesel engine can be adapted to the operating conditions.

The length of time during which the buffer action (cushion action) by the flow resistance of the hydraulic oil acts becomes longer as the depth h of the recess 9a becomes larger, as in the case of the structure of FIGS. 2 (a) and 2 (b). . That is, the valve closing timing of the exhaust valve 5 can be delayed as the depth h of the recess 9a is increased.

According to the configuration of FIGS. 3A and 3B, the structure for changing the height of the recess 9a can be simplified as compared with the structure shown in FIGS. 2A and 2B.

Second Embodiment
FIG. 5 is a schematic configuration view showing an exhaust valve drive device according to a second embodiment of the present invention. The exhaust valve drive device 51 differs from the exhaust valve drive device 1 of the first embodiment in that there are no convex portion on the top surface of the piston 7 and no concave portion on the ceiling surface of the cylinder 9, and a branch point of the hydraulic path 11 The leak passage 53 branches from 11 d, and a variable orifice (flow rate adjusting means) 55 for changing the passage area of the leak passage 53 is connected in the middle thereof. The configuration and operation of the other parts are the same as those of the exhaust valve drive device 1 of the first embodiment, and therefore the same reference numerals are given to the respective parts and the description will be omitted.

The throttling amount of the variable orifice 55 is controlled by a controller (control means) 57. The controller 57 controls the throttling amount of the variable orifice 55 so that the passage area of the leak passage 53 decreases as the load on the diesel engine increases. A flow control valve or the like may be provided instead of the variable orifice 55.

According to the exhaust valve drive device 51, as in the exhaust valve drive device 1 of the first embodiment, when the hydraulic pressure supply device 13 is driven by the cam 35, the hydraulic pressure is supplied to the cylinder 9 at a predetermined valve opening timing. As a result, the piston 7 inside the cylinder 9 is pressed and the exhaust valve 5 is opened. When the hydraulic pressure supply to the cylinder 9 is discontinued, the exhaust valve 5 is closed by the biasing force of the air spring device 15.

A part of the hydraulic oil (hydraulic pressure) supplied from the hydraulic pressure supply device 13 leaks to the outside of the hydraulic path 11 from the variable orifice 55 provided in the leak passage 53. As a result, the amount of oil returned from the cylinder 9 to the hydraulic pressure supply device 13 when the exhaust valve 5 is closed is smaller than the amount of oil pressure-fed to the cylinder 9 when pressurized by the hydraulic pressure supply device 13. Therefore, when the exhaust valve 5 is closed, the piston 7 can be properly raised to the top in the cylinder 9 to reliably close the exhaust valve 5.

By controlling the variable orifice 55, it is possible to adjust the amount of leakage of the hydraulic oil supplied from the hydraulic pressure supply device 13 to the outside. When the leak amount is reduced, the closing speed of the exhaust valve 5 is decreased, and when the leak amount is increased, the closing speed of the exhaust valve 5 is increased.

As described above, by providing the variable orifice 55 in the leak passage 53 branched from the hydraulic pressure passage 11 between the hydraulic pressure supply device 13 and the cylinder 9, the timing at which the exhaust valve 5 closes can be made earlier or later. Can be adapted to the driving situation.

Moreover, since the change of the timing at which the exhaust valve 5 closes can be achieved with a simple structure in which the leak passage 53 and the variable orifice 55 are provided in the hydraulic path 11, it is suitable for marine diesel engines where a simple configuration is desirable. ing. The leak passage 53 may not necessarily branch from the hydraulic pressure passage 11, and may branch from the cylinder 9, for example.

FIG. 6 is a graph showing the relationship between the lift amount (a) of the cam 35 in the exhaust valve drive device 51, the hydraulic pressure (b) in the hydraulic chamber 21 and the lift amount (c) of the exhaust valve 5. The basic operation is the same as that of the exhaust valve drive device 1 according to the first embodiment described with reference to FIG.

If the throttling amount of the variable orifice 55 of the leak passage 53 is minimum, the hydraulic oil in the hydraulic pressure chamber 21 is returned to the hydraulic pressure supply device 13 without leaking too much when the exhaust valve 5 is closed. It takes time for the piston 7 to ascend. Therefore, the reduction state of the hydraulic pressure in the hydraulic chamber 21 corresponds to the reduction amount of the lift amount of the cam 35, as shown by the solid line in FIG. 6 (b). Further, the reduction state of the lift amount of the exhaust valve 5 is as shown by a solid line in FIG. 6C, and the timing at which the exhaust valve 5 is closed is delayed.

Then, when the throttling amount of the variable orifice 55 is expanded, the amount of leakage of the hydraulic oil in the hydraulic chamber 21 increases, so the amount of hydraulic oil returned from the hydraulic chamber 21 to the hydraulic pressure supply device 13 decreases. Within 9, the time for the piston 7 to rise is reduced. Therefore, the reduction state of the hydraulic pressure in the hydraulic chamber 21 is reduced more quickly than the reduction amount of the lift amount of the cam 35, as shown by a broken line in FIG. 6 (b). Further, the reduction state of the lift amount of the exhaust valve 5 is as shown by a broken line in FIG. 6C, and the timing at which the exhaust valve 5 is closed becomes earlier.

As described above, the control device 57 controls the throttling amount of the variable orifice 55 so that the passage area of the leak passage 53 decreases as the load on the diesel engine increases. Therefore, as the load on the diesel engine increases, the timing at which the exhaust valve 5 closes can be delayed, and the compression pressure of the in-cylinder gas can be prevented from becoming too high during high load operation to improve the durability of the diesel engine.

As a modification, as indicated by a broken line in FIG. 5, a leak passage 53a connecting the hydraulic chamber 21 and the hydraulic passage 11 is provided, and a variable orifice 55a is provided in the leak passage 53a. It may be possible to adjust the time for the piston 7 to rise when the valve is closed.

As explained above, according to the exhaust

valve drive device

1, 51 according to the embodiment of the present invention and the diesel engine provided with the same, the timing at which the exhaust valve 5 is closed by the simple configuration suitable for marine diesel engines As a result, the characteristics of the diesel engine can be adapted to the operating conditions, the reliability and durability of the internal combustion engine can be enhanced, and fuel consumption can be improved.

The present invention is not limited to only the configuration of the above embodiment, and modifications and improvements can be made as appropriate without departing from the scope of the present invention, and such modifications and improvements can be made. The form is also included in the scope of the present invention.

1, 51 exhaust valve drive device 5 exhaust valve 7 piston 7 a convex portion 9 cylinder 9 a concave portion 11 hydraulic path 13 hydraulic pressure supply device (hydraulic pressure supply means)
15 Air spring device (valve closing biasing means)
17

actuators

19, 57 control devices (control means),
21 oil pressure chamber 31 plunger 35 cam 37 pressure chamber 53 leak passage 55 variable orifice (flow rate adjusting means)

Claims

A piston provided at an exhaust valve of the internal combustion engine,
A cylinder in which the piston is accommodated;
Hydraulic pressure supply means driven by a cam to intermittently supply hydraulic pressure to the cylinder at a predetermined valve opening timing, and pressing the piston to open the exhaust valve;
Valve closing means for urging the exhaust valve in the valve closing direction;
A projection formed on a top surface of the piston and having a top area smaller than a cross-sectional area of the piston;
A recess formed on a ceiling surface of the cylinder and into which the protrusion is inserted via a gap when the piston is lifted;
An actuator for changing the depth of the recess;
Control means for controlling the actuator;
An exhaust valve drive device comprising:
The exhaust valve drive apparatus according to claim 1, wherein the control means controls the actuator such that the depth of the recess increases as the load on the internal combustion engine increases.
A piston provided at an exhaust valve of the internal combustion engine,
A cylinder in which the piston is accommodated;
Hydraulic pressure supply means driven by a cam to intermittently supply hydraulic pressure to the cylinder at a predetermined valve opening timing, and pressing the piston to open the exhaust valve;
Valve closing means for urging the exhaust valve in the valve closing direction;
A leak passage for releasing the hydraulic pressure generated by the hydraulic pressure supply means;
Flow rate adjusting means for changing the passage area of the leak passage;
Control means for controlling the flow rate adjusting means;
An exhaust valve drive device comprising:
4. The exhaust valve driving apparatus according to claim 3, wherein the control means controls the flow rate adjusting means such that a passage area of the leak passage decreases as a load on the internal combustion engine increases.
An internal combustion engine comprising the exhaust valve drive device according to any one of claims 1 to 4.