Engine valve valvetrain

Abstract

Provided is an engine valve valvetrain (1) comprising: rocker arms (3), each having a tip portion (3a) that is caused to oscillate and rotate by a cam (2); a valve bridge (11) that is supported to be able to oscillate in a reciprocating manner within a cylinder head (8), and that has a lash adjuster (6) on each of arm portions (11a, 11b); engine valves (5) that are in contact with the lash adjusters (6); and a valve spring (7) that biases the valve bridge (11) toward the tip portions of the rocker arms. Each lash adjuster (6) comprises: a cylindrical plunger (13) that is internally provided with a first oil reservoir chamber (13a); a body (14) that slidably supports the plunger (13) via a plunger spring (15) provided in a second oil reservoir chamber (18); and a check ball (16) that is disposed within the second oil reservoir chamber (18) and that is biased, via a ball spring (17), against an inner edge (13c) of a hole (13b) in a bottom portion of the plunger (13). Each of the arm portions (11a, 11b) has a first oil supply port (19) formed to open on a top surface and reach an upper portion of the plunger (13). The first oil supply port (19) is formed to have substantially the same inner diameter as the first oil reservoir chamber (13a). The upper portion of the plunger (13) has a second oil supply port (20) that opens toward the first oil reservoir chamber (13a).

Description

Engine valve train

[0001] This technology relates to an engine valve operating mechanism that uses a lash adjuster to eliminate the clearance that occurs between a valve bridge that has a pair of engine valves and a cam that moves the valve bridge back and forth via a rocker arm to open and close the engine valves.

[0002] Among engine valve operating mechanisms that use a rotating cam and rocker arms to open and close a pair of engine valves provided on a valve bridge, one having a mechanism for eliminating the clearance that occurs between the cam and the rocker arm is shown in FIG. 1 of Patent Document 1.

[0003] The engine valve valve operating mechanism shown in FIG. 1 of Patent Document 1 has a mechanism that, when a clearance is about to occur between the right end of the rocker arm and the cam when the valve is closed, applies oil pressure from a hydraulic pump to an oil reservoir, an oil passage, and an oil reservoir above the valve stem, which are provided from the inside of the leg of the crosshead to the arm, thereby lowering the piston and gasoline valve and urging the center of the crosshead (valve bridge) toward the left end of the rocker arm, thereby eliminating the clearance.

[0004] Japanese Patent Application Publication No. 9-112233

[0005] The clearance elimination mechanism in the valve train of Patent Document 1 has an oil reservoir and oil passages throughout the entire arm and leg section of the crosshead (valve bridge), and also has a hydraulic pump, resulting in high manufacturing costs. On the other hand, in a valve train with multiple engine valves on a valve bridge without a clearance elimination mechanism, some valve trains supply oil from the atmosphere in the cylinder head to the valve stems in the valve bridge. Therefore, even in a valve train with a clearance elimination mechanism, it is conceivable to omit large-scale oil passages and a hydraulic pump and reduce costs by supplying oil from the atmosphere in the cylinder head to the clearance elimination mechanism. However, using oil from the atmosphere in the cylinder head poses a problem, as there is a risk of insufficient oil being supplied to the clearance elimination mechanism.

[0006] In view of the above problems, the present invention provides a valve train for an engine valve that is capable of supplying sufficient oil from the atmosphere in the cylinder head to a lash adjuster (clearance elimination mechanism).

[0007] The valve bridge has a rocker arm whose tip end swings and rotates in accordance with the rotation of a cam, a valve bridge supported in a cylinder head so as to be able to swing back and forth and having a pair of arms each provided with a lash adjuster, an engine valve whose base end contacts the lash adjuster, and a valve spring which biases the valve bridge to the tip end of the rocker arm via the engine valve, the lash adjuster having a first oil reservoir inside and a cylindrical plunger integrated with the valve bridge and a plunger spring provided in a second oil reservoir formed between the plunger and the valve bridge. and a check ball arranged in the second oil reservoir and biased against the inner edge of the hole in the bottom of the plunger via a check ball spring. In this valve mechanism for an engine valve, the pair of arms each have a first oil supply port that opens to a top surface and is formed so as to reach from the top surface to an upper part of the plunger, the first oil supply port is formed to have approximately the same inner diameter as the first oil reservoir, and the upper part of the plunger has a second oil supply port that opens toward the first oil reservoir.

[0008] The valve bridge arms reciprocate along the central axis of the first oil supply port, which opens into the top surface, when the engine valves are opened and closed, thereby directing oil present in the atmosphere within the cylinder head into the first oil supply port. Because the first oil supply port is formed to have approximately the same inner diameter as the first oil chamber of the plunger, oil present in the atmosphere within the cylinder head is easily directed from the first oil supply port through the second oil supply port to the first oil chamber.

[0009] It is also preferable that a through hole be formed in the inner wall of the first oil supply port, which penetrates to the outside of the valve bridge.

[0010] (Operation) The through holes allow the oil present in the atmosphere inside the cylinder head to easily pass into the first oil supply port, and the oil is supplied sufficiently to the first oil supply port.

[0011] Furthermore, in the valve mechanism of the engine valve, it is desirable that the first oil supply port has an oil passage formed extending laterally from the arm portion, one end of which opens to the side and the other end of which is formed at a position offset laterally from above the second oil supply port, and an oil pocket formed so as to open from the other end of the oil passage toward the top surface of the arm portion.

[0012] (Operation) When the valve bridge reciprocates, oil present in the atmosphere within the cylinder head is guided to the oil pocket that opens in the direction of the reciprocating motion, and its flow is promoted by the oil passage that opens further to the side from the base end of the oil pocket, promoting its flow into the first oil supply port and leading to the first oil reservoir within the plunger. Furthermore, when the valve closes, the oil guided into the first oil reservoir is prevented from flowing out of the valve bridge from the second oil supply port to the oil passage by the oil passage that extends to the side.

[0013] In addition, in the valve mechanism of the engine valve, it is desirable to provide the second oil supply port with a check valve that opens only when the oil pressure in the first oil chamber exceeds the oil pressure in the second oil chamber.

[0014] (Operation) Oil in the atmosphere within the cylinder head is guided from the second oil supply port into the first oil reservoir in the plunger by the check valve, which opens when the valve bridge is opened, and the oil guided into the first oil reservoir is prevented from being discharged from the second oil supply port by the check valve, which closes when the valve bridge is closed.

[0015] According to the engine valve operating mechanism, oil present in the atmosphere within the cylinder head of the valve bridge is sufficiently guided to the first oil supply port as the valve bridge reciprocates along the central axis of the first oil supply port, and therefore a sufficient amount of oil is supplied from the second oil supply port into the plunger of the lash adjuster.

[0016] Furthermore, with the engine valve operating mechanism, the oil present in the atmosphere within the cylinder head of the valve bridge is encouraged to flow into the first oil supply port by the through hole that opens from within the first oil supply port to the outside of the valve bridge, further ensuring a sufficient amount of oil in the first oil reservoir.

[0017] In addition, according to the engine valve mechanism, the oil present in the atmosphere within the cylinder head of the valve bridge is promoted to flow into the first oil supply port by the oil pocket first oil supply port that opens in the direction of reciprocating motion of the valve bridge, and further promoted to flow into the oil passage by the oil passage that opens sideways from the bottom of the first oil supply port, thereby ensuring a sufficient amount of oil in the first oil reservoir. Also, because the oil pocket does not open above the second oil supply port, the oil in the first oil reservoir of the plunger is prevented from moving upward by the oil passage that extends sideways when the engine valve is closed via the valve bridge, making it difficult for the oil to be discharged outside the plunger, thereby ensuring a sufficient amount of oil in the first oil reservoir.

[0018] Furthermore, with the engine valve operating mechanism, the oil present in the atmosphere within the cylinder head is encouraged to flow into the first oil reservoir within the plunger by the first oil supply port, which has one end opening upward and the other opening to the side, and furthermore, the oil passage extending laterally during the valve closing operation of the valve bridge prevents the oil from flowing out of the second oil supply port into the oil passage, making it difficult for the oil to be discharged outside the valve bridge, ensuring a sufficient amount of oil within the first oil reservoir.

[0019] Furthermore, according to the engine valve valve operating mechanism, the oil guided into the first oil chamber of the plunger is prevented from being discharged outside the plunger by a check valve that closes when the engine valve is closed via the valve bridge, ensuring a sufficient amount of oil in the first oil chamber.

[0020] 1 is a partial cross-sectional view showing a first embodiment of a valve train for an engine valve; FIG. 2 is an enlarged cross-sectional view of a valve bridge and a lash adjuster shown in FIG. 1; FIG. 3 is an enlarged cross-sectional view of a first modified example of the valve bridge shown in FIG. 2; FIG. 4 is an enlarged cross-sectional view of a second modified example of the valve bridge and a first modified example of the lash adjuster shown in FIG. 2;

[0021] A preferred first embodiment of an engine valve valve train 1 according to the present application will be described with reference to Figure 1. In Figures 1 to 4, the engine valve valve train will be described with the directions indicated as (upper: lower: left: right: front: rear = Up: Lo: Le: Ri: towards the front of the paper: towards the back of the paper). Note that the shape of a valve bridge 11 is omitted in Figure 1, and will be described in conjunction with detailed cross-sectional views in Figures 2 to 4.

[0022] The engine valve valve train 1 in Figure 1 includes a cam 2, a rocker arm 3, a shaft 4, a pair of engine valves (5, 5), a pair of lash adjusters (6, 6), a pair of valve springs (7, 7), a pin 10, a valve bridge 11, and a bolt 12. The cam 2, the rocker arm 3, the engine valves (5, 5), and the valve bridge 11 are each supported inside a cylinder head 8. The atmosphere inside 8a of the cylinder head 8 contains oil.

[0023] 1 is supported rotatably around an axis 3b of a base 3c that holds the cylinder head. A pin 10 is fixed to a base end 3d of the rocker arm, and a semispherical lower end 10a of the pin 10 is held in a semispherical recess in the upper end of the shaft 4. When the cam 2 rotates, the rocker arm 3 swings and rotates back and forth around the axis 3b in accordance with the up and down movement of the tip of the shaft 4, and the tip end 3a of the rocker arm 3 moves back and forth up and down.

[0024] As shown in Figure 2, the valve bridge 11 integrally comprises a left arm 11a and a right arm 11b extending to the left and right from near the upper end of the leg 11c, and the left arm 11a and the right arm 11b are provided with cylindrical portions 11a1 and 11b1 with top surfaces, respectively, to which the lash adjusters (6, 6) are attached. The valve bridge 11 is fixed by screwing it into the female thread portion 8b of the cylinder head via the bolt 12 shown in Figure 1. The lash adjusters (6, 6) have the same configuration.

[0025] As shown in FIG. 1 , the engine valves (5, 5) are identical valves each having a head portion 5b and a stem portion, and each stem end portion 5a is urged toward the bottom of the body 14 of the lash adjuster 6 by valve springs (7, 7) held in the cylinder head 8. The valve bridge 11 is urged toward the tip end 3a of the rocker arm 3 by the valve springs (7, 7) via the engine valves (5, 5) and the lash adjusters (6, 6). When the tip end 3a of the valve bridge 11 descends with the rotation of the cam 2, the valve bridge 11 descends together with the engine valves (5, 5), opening the valve and supplying the air-fuel mixture in the intake passage (or exhaust passage) 9 into the combustion chamber 8c (or exhausting it in the case of an exhaust passage). As the cam 2 continues to rotate, the valve bridge 11 ascends together with the engine valves (5, 5) due to the urging force of the valve springs (7, 7), closing the valve.

[0026] As shown in Figure 2, each lash adjuster 6 has a plunger 13, a body 14, a plunger spring 15, a check ball 16, a check ball spring 17, and a ball cage 29. The plunger 13 has a cylindrical shape with a bottom, a first oil reservoir 13a inside, a circular hole 13b at the bottom, and a ball cage 29 fixed below the bottom. The body 14 also has a cylindrical shape with a bottom, and the plunger 13 is slidably held inside by a plunger spring 15 consisting of a compression spring provided at the bottom. A second oil reservoir 18 is formed between the plunger 13 and the body 14. The bodies (14, 14) of the lash adjusters (6, 6) are inserted and held in a freely slidable state in the top-faced cylindrical portions (11a1, 11b1) of the valve bridge 11, and the plungers (13, 13) are urged toward the top surfaces (11a2, 11b2) of the top-faced cylindrical portions (11a1, 11b1) by plunger springs (15, 15). The check ball 16 is urged toward the inner edge portion 13c of the hole 13b at the bottom of the plunger 13, inside the ball cage 29, by a check ball spring 17 held at the bottom of the ball cage 29.

[0027] 1 and 2 closes the hole 13b during a valve-opening operation in which the valve bridge 11 and the engine valves (5, 5) descend, and opens the hole 13b based on the oil pressure difference generated between the first oil chamber 13a and the second oil chamber 18 when the valve-closing operation is completed and the valve bridge 11 and the engine valves (5, 5) stop rising. As the hole 13b opens, each plunger (14, 14) receives the biasing force of the plunger spring 15, which raises the valve bridge 11 relative to the body (14, 14) and the engine valves (5, 5) and biases it toward the tip end 3a of the rocker arm, thereby eliminating the clearance generated between the tip end 3a and the valve bridge 11 when the valve is completely closed.

[0028] 2, the upper portion of the plunger (13, 13) is open, and this opening constitutes a circular hole-shaped second oil supply port (20, 20) having the same inner diameter d2 as the first oil reservoir chamber (13a, 13a). Furthermore, a pair of arms (11a, 11b) of the valve bridge 11 each have a circular hole-shaped first oil supply port (19, 19) that opens upward and is continuous with the second oil supply port (20, 20). The first oil supply port (19, 19) is disposed concentrically with the second oil supply port (20, 20), and the inner diameter d1 of the first oil supply port (19, 19) is formed so as to be approximately the same as or the same as the inner diameter d2 of the first oil reservoir chamber (13a, 13a) (either d1 or d2 may be smaller).

[0029] In addition, through holes (31, 31) that open from the inside of the first oil supply ports (19, 19) toward the outside of the valve bridge 11 are provided above the second oil supply ports (20, 20) on the inner wall of the first oil supply ports (19, 19) in Figure 2.

[0030] 2 is formed to have approximately the same inner diameter as the first oil reservoir chamber (13a, 13a) of the plunger (13, 13), oil present in the atmosphere inside the inside 8a of the cylinder head 8 is easily guided from the first oil supply port (19, 19) to the first oil reservoir chamber (13a, 13a) via the second oil supply port (20, 20) which has the same inner diameter as the first oil reservoir chamber (13a, 13a). Furthermore, the through-holes (31, 31) above the second oil supply port (20, 20) make it easier for the oil to flow through the first oil supply port (19, 19), further facilitating the oil being guided to the first oil reservoir chamber, and oil in the atmosphere is sufficiently guided into the lash adjuster 6. The first oil supply ports (19, 19) do not necessarily have to be provided with the through holes (31, 31), but it is better to provide them in order to improve the fluidity of the oil.

[0031] Also, Figure 3 shows a valve bridge 11' which is a modified example of the valve bridge 11 in Figure 1. The valve bridge 11' has a configuration in common with the valve bridge 11 in Figure 1, except that the shape of the first oil supply ports (21, 22) is different from the first oil supply ports (19, 19) of the valve bridge 11. Also, the lash adjusters 6 in Figures 1 and 3 are the same.

[0032] The valve bridge 11′ shown in FIG. 3 has a first oil supply port 21 in the left arm portion 11a′ and a first oil supply port 22 in the right arm portion 11b′. The first oil supply port 21 has a left end 28b that opens to a side of the valve bridge 11, and an other end 28a that has an oil passage 24 provided at a position offset to the right from above the second oil supply port 20, and an oil pocket 23 that connects to the oil passage 24 at the other end 28a and opens upward toward the top surface of the left arm portion 11a′. The first oil supply port 22 has a right end 28d that opens to a side of the valve bridge 11, and an other end 28c that has an oil passage 26 provided at a position offset to the left from above the second oil supply port 20, and an oil pocket 25 that connects to the oil passage 26 at the other end 28c and opens upward toward the top surface of the left arm portion 11a′.

[0033] 3, the bodies (14, 14) of the plungers (6, 6) are slidably inserted into the arm portions (11a1′, 11b1′), and the top surfaces (11a2′, 11b2′) of the cylindrical portions (11a1′, 11b1′) with top surfaces are formed inside the oil passages (24, 26). The top surfaces (13d, 13d) of the plungers (13a, 13a) are biased toward the top surfaces (11a2′, 11b2′), so that the second oil supply ports (20, 20) open to the inside of the oil passages (24, 26), respectively.

[0034] The oil present in the atmosphere inside 8 a of cylinder head 8 is easily guided to the oil pockets (23, 25) that open in the same vertical direction as the valve bridge 11′ reciprocates up and down. Furthermore, the flow is promoted by the oil passages (24, 26) that open laterally from the lower end (other ends 28 a and 28 c) of the oil pocket 23, thereby promoting the flow of oil into the first oil supply ports (20, 20) and leading it to the first oil reservoir chambers (13 a, 13 a) in the plungers (13, 13). When the engine valves (5, 5) are closed, the oil introduced into the first oil reservoir (13a, 13a) is prevented from moving upward in the direction of valve closing of the valve bridge 11′ by the oil passages (24, 26) that extend laterally without opening upward, and thus is prevented from flowing out from the second oil supply ports (20, 20) to the oil passages (24, 26), making it difficult for the oil to be discharged to the outside of the valve bridge 11. As a result, a sufficient amount of oil is supplied and maintained in the first oil reservoir (13a, 13a).

[0035] FIG. 4 shows a valve bridge 11″ that is a modified example of the valve bridge 11 of FIG. 1. The valve bridge 11″ has a configuration in common with the valve bridge 11 of FIG. 1, except that no through-holes are formed in the inner walls of the first oil supply ports (19′, 19′). The lash adjusters (6′, 6′) are provided with check valves (27, 27) in the second oil supply ports (20′, 20′), and have a configuration in common with the lash adjusters (6, 6) of FIG. 1.

[0036] The check valves (27, 27) in Figure 4 are arranged so as to open only when the internal pressure on the first oil supply port (19', 19') side is higher than the internal pressure on the first oil reservoir (13a', 13a') side, and to be kept in a closed state when the internal pressure on the first oil supply port (19', 19') side is lower than the internal pressure on the first oil reservoir (13a', 13a') side. The check valves (27, 27) open when the intake passage (or exhaust passage) 9 is completely closed by the engine valves (5, 5) to guide the oil present in the atmosphere inside 8a of the cylinder head 8 into the first oil reservoir chamber (13a', 13a'), but close when the intake passage (or exhaust passage) 9 is completely opened by the engine valves (5, 5) to prevent the oil in the first oil reservoir chamber (13a', 13') from flowing out of the valve bridge 11'' through the first oil supply ports (19', 19') above, so that a sufficient amount of oil is kept supplied to the first oil reservoir chamber (13a, 13a).

[0037] Note that, in the inner wall of the first oil supply ports (19', 19') in Fig. 4, a through-hole equivalent to the through-hole 31 that penetrates to the outside of the valve bridge 11'' as in the first oil supply ports (19, 19) in Fig. 1 may be provided above the second oil supply ports (20', 20'). In this case, the flow of oil to the first oil supply ports (19', 19') is further improved, and the inflow of oil into the first oil reservoir chambers (13a', 13a') is further promoted.

[0038] REFERENCE SIGNS LIST 1 Engine valve valve operating mechanism 2 Cam 3 Rocker arm 3a Tip portion 5 Engine valve 6 Lash adjuster 7 Valve spring 8 Cylinder head 11 Valve bridge 11a Left arm portion 11b Right arm portion 13 Plunger 13a First oil reservoir chamber 13b Hole at bottom of plunger 13c Inner edge portion of hole 14 Body 15 Plunger spring 16 Check ball 17 Check ball spring 18 Second oil reservoir chamber 19 First oil supply port 20 Second oil supply port 21, 22 First oil supply port 23, 25 Oil pocket 24, 26 Oil passage 28b, 28d One end of oil passage 28a, 28c Other end of oil passage 27 Check valve 31 Through hole D0 Outer diameter of cemented carbide metal rod and inner diameter of first shaft portion D3: Outer diameter of the first shaft portion and the outer peripheral distance of the cylindrical outer peripheral surface; d1: Inner diameter of the first oil passage; d2: Inner diameter of the first oil reservoir;

Claims

1. A valve train for an engine valve comprising: a rocker arm whose tip end swings and rotates in response to rotation of a cam; a valve bridge supported within a cylinder head so as to be capable of swinging back and forth and having a pair of arms each provided with a lash adjuster; an engine valve whose base end contacts the lash adjuster; and a valve spring which biases the valve bridge towards the tip end of the rocker arm via the engine valve, wherein the lash adjuster has a first oil reservoir on the inside, a cylindrical plunger integrated with the valve bridge, a body which slidably supports the plunger via a plunger spring provided in a second oil reservoir formed between the plunger and the body, and a check ball which is disposed within the second oil reservoir and biased via a check ball spring against the inner edge of a hole in the bottom of the plunger; wherein the pair of arms each have a first oil supply port which opens to a top surface and is formed so as to reach from the top surface to the top of the plunger, and the first oil supply port is formed to have approximately the same inner diameter as the first oil reservoir, a second oil supply port that opens toward the first oil chamber, the second oil supply port being disposed in an upper portion of the plunger; 2. The engine valve train as set forth in claim 1, wherein a through hole is formed on the inner wall of the first oil supply port, the through hole penetrating to the outside of the valve bridge.

3. The engine valve operating mechanism as described in claim 1, characterized in that the first oil supply port has an oil passage formed extending laterally of the arm portion, one end of which opens to the side and the other end of which is formed in a position offset laterally from above the second oil supply port, and an oil pocket formed so as to open from the other end of the oil passage toward the top surface of the arm portion.

4. A valve mechanism for an engine valve as described in claim 1, characterized in that the second oil supply port is provided with a check valve which opens only when the oil pressure in the first oil chamber exceeds the oil pressure in the second oil chamber.

Images