Valve train of an internal combustion engine

Abstract

The purpose is to reduce the load on the internal combustion engine during startup, regardless of the engine's operating state. [Solution] The valve train 30 of the internal combustion engine of the present invention includes a circular cam lobe 51 that rotates integrally with the exhaust cam 31 and has a convex portion 52 with a curved shape, a control member 53 provided on the rocker arm 34 that can contact the convex portion 52 and transitions between a first state in which contact with the convex portion 52 causes the rocker arm 34 to open the exhaust valve 19 and a second state in which contact with the convex portion 52 is not possible, and a pin member 58 that pushes the control member 53 from the first state to the second state when hydraulic pressure is applied from the lash adjuster 39. When the control member 53 is in the first state, it contacts the convex portion 52, causing the rocker arm 34 to open the exhaust valve 19, thereby reducing the burden on the internal combustion engine during startup.

Description

Technical Field

[0001] The present invention relates to a valve operating device for an internal combustion engine.

Background Art

[0002] Conventionally, a valve operating device provided with a decompression mechanism for reducing the load when starting an internal combustion engine is known. In Patent Document 1, a single control shaft is rotated by a centrifugal mechanism including a centrifugal weight and a return spring, so that a first lift pin and a second lift pin provided on an exhaust cam are sequentially actuated to exhibit a decompression function and an exhaust reflux function. A valve operating device for an internal combustion engine is disclosed. Specifically, at the time of cranking, the centrifugal weight is held at the contracted position by the return spring, so that the control shaft projects the first lift pin beyond the base surface of the exhaust cam. Therefore, when the exhaust valve is opened at a minute opening degree by the first lift pin, the rise of the compression pressure in the cylinder bore is suppressed, and the load when starting the internal combustion engine is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the valve operating device of the internal combustion engine of Patent Document 1, the timing for projecting the first lift pin by operating the first lift pin by the centrifugal mechanism cannot be controlled. Therefore, before the internal combustion engine stops, the first lift pin may project beyond the base surface, and there is a risk of pinching and damaging the first lift pin between the exhaust cam and the rocker arm. In addition, since the first lift pin projects more steeply than the base surface of the exhaust cam, there is a risk of generating abnormal noise due to the collision between the first lift pin and the rocker arm.

[0005] This invention has been made in view of the above-mentioned problems, and aims to reduce the burden on the internal combustion engine during startup, regardless of the operating state of the internal combustion engine. [Means for solving the problem]

[0006] The present invention relates to a valve train for an internal combustion engine in which one end of a lifter is pivotably supported via a hydraulic lash adjuster, and the lifter opens a valve when pressed by a cam, and is characterized by comprising: a circular cam lobe that rotates integrally with the cam and has a convex portion in the shape of a mountain; a control member provided on the lifter that can contact the convex portion and transitions between a first state in which the lifter opens the valve by contacting the convex portion and a second state in which it cannot contact the convex portion; and a pin member that pushes the control member from the first state to the second state when hydraulic pressure is applied from the lash adjuster. [Effects of the Invention]

[0007] According to the present invention, the burden on the internal combustion engine during startup can be reduced without being affected by the operating state of the internal combustion engine. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing an example of an engine configuration. [Figure 2] This is a perspective view showing an example of the configuration of a decompression mechanism. [Figure 3] This is a perspective view showing an example of a rocker arm configuration. [Figure 4] This is a diagram illustrating the operation of the valve train. [Modes for carrying out the invention]

[0009] The valve train 30 for an internal combustion engine according to the present invention is configured such that one end of a rocker arm 34 is pivotably supported via a hydraulic lash adjuster 39, and the rocker arm 34 opens the exhaust valve 19 when pressed by an exhaust cam 31. The valve train 30 also includes a circular cam lobe 51 that rotates integrally with the exhaust cam 31 and has a convex portion 52 with a curved shape, a control member 53 provided on the rocker arm 34 that transitions between a first state in which the rocker arm 34 opens the exhaust valve 19 by contacting the convex portion 52 and a second state in which it cannot contact the convex portion 52, and a pin member 58 that pushes the control member 53 from the first state to the second state when hydraulic pressure is applied from the lash adjuster 39. [Examples]

[0010] The valve train of the internal combustion engine according to the present invention will be described below with reference to the drawings. Figure 1 shows an example of the configuration of engine 1 as an internal combustion engine. Engine 1 functions, for example, as a power source to drive a vehicle. Engine 1 comprises an engine body 10 and a valve train 30.

[0011] First, let me explain the engine body 10. The engine body 10 performs a series of strokes consisting of an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. For the sake of ease of understanding, the engine body 10 will be described as a single-cylinder engine, but it may also be a multi-cylinder engine.

[0012] The engine body 10 is constructed by integrally joining a cylinder block 11 and a cylinder head 12. The cylinder block 11 has a crank chamber formed inside, and the crankshaft is rotatably supported within the crank chamber. A piston 13 is fitted into the cylinder of the cylinder block 11, and the crankshaft rotates via a connecting rod 14 as the piston 13 reciprocates along the cylinder axis Cy. A combustion chamber 15 is formed between the cylinder block 11 and the cylinder head 12. A spark plug is positioned in the cylinder head so that its tip is located inside the combustion chamber 15.

[0013] The cylinder head 12 has an intake port 16 and an exhaust port 17 that communicate with the combustion chamber 15. The intake port 16 guides intake air taken in from outside the engine body 10 into the combustion chamber 15. The intake outlet of the intake port 16 that is on the side of the combustion chamber 15 is called the intake outlet 16a. On the other hand, the exhaust port 17 discharges the exhaust gas burned in the combustion chamber 15 to the outside of the engine body 10. The exhaust inlet of the exhaust port 17 that is on the side of the combustion chamber 15 is called the exhaust inlet 17a. Note that the intake port 16 and exhaust port 17 are not limited to one, but may be multiple.

[0014] An intake valve 18 is provided in the intake port 16, which, when opened, draws intake air from the intake port 16 into the combustion chamber 15. An exhaust valve 19 is provided in the exhaust port 17, which, when opened, discharges exhaust gas from the combustion chamber 15 to the exhaust port 17. The intake valve 18 and exhaust valve 19 are constantly biased by valve springs, each arranged to surround the valve stem 20, so that the valve heads 21 contact the intake outlet 16a and exhaust inlet 17a, respectively. Note that the intake valve 18 and exhaust valve 19 are not limited to a single valve but may be multiple.

[0015] Furthermore, a fuel injector is provided in the intake pipe connected to the intake port 16. When the fuel injector injects fuel, it is mixed with the intake air to create a fuel-air mixture, which then flows into the combustion chamber 15.

[0016] The engine body 10 also includes an oil pan for storing oil and an oil pump for supplying oil to the lubrication parts of the engine body 10. The oil pump is driven in conjunction with the rotation of the crankshaft of the engine body 10, drawing up the oil stored in the oil pan and pressurizing it to the lubrication parts. The oil pump also supplies oil to the lash adjuster 39, which will be described later.

[0017] Next, the valve operating device 30 will be described. The valve operating device 30 opens and closes the intake valve 18 and the exhaust valve 19. In the following, the valve operating device that opens and closes the exhaust valve 19 will be described, but the valve operating device that opens and closes the intake valve 18 can be configured in the same manner.

[0018] The valve operating device 30 includes an exhaust cam 31 as a cam for opening and closing the exhaust valve 19, a rocker arm 34 as a lifter, and a hydraulic lash adjuster 39. The exhaust cam 31 rotates integrally with a camshaft 33 rotatably supported by the cylinder head 12. The exhaust cam 31 has a convex portion 32 having a mountain shape. The camshaft 33 is connected to the crankshaft via a cam chain and rotates in conjunction with the rotation of the crankshaft.

[0019] One end of the rocker arm 34 is swingably supported via the lash adjuster 39, and the other end is connected to the tip of the valve stem 20 of the exhaust valve 19. A roller 35 as a pressing portion pressed by the convex portion 32 of the exhaust cam 31 is rotatably supported between one end and the other end of the rocker arm 34. When the exhaust cam 31 rotates and the roller 35 is pressed by the convex portion 32, the rocker arm 34 swings with one end as the center and the other end moves toward the combustion chamber 15 side against the biasing force of the valve spring, so that the valve head 21 of the exhaust valve 19 moves away from the exhaust inlet portion 17a and opens. On the other hand, when the exhaust cam 31 rotates and the pressing by the convex portion 32 is released, the exhaust valve 19 is returned to its original position by the biasing force of the valve spring, and the valve head 21 of the exhaust valve 19 contacts the exhaust inlet portion 17a to close the valve. By the operation of such a rocker arm 34, the opening and closing timing of the exhaust valve 19 is controlled in the intake stroke, compression stroke, combustion stroke, and exhaust stroke of the engine body 10.

[0020] The lash adjuster 39 is disposed at one end of the rocker arm 34. The spherical portion 40 formed at the tip of the lash adjuster 39 serves as the swing fulcrum of the rocker arm 34. Further, the lash adjuster 39 is a hydraulic type and adjusts the valve clearance of the exhaust valve 19 using the hydraulic pressure of the oil supplied by the oil pump. Specifically, while oil is being supplied, the lash adjuster 39 presses the rocker arm 34 against the exhaust cam 31 side, thereby setting the valve clearance on the exhaust valve side to zero. Note that when the operation of the engine 1 is stopped and oil is not supplied to the lash adjuster 39, the oil inside the lash adjuster 39 gradually leaks out.

[0021] In order to reduce the burden at the start of the engine 1 in the engine 1 configured as described above, the valve operating device 30 of the present embodiment has a decompression mechanism 50.

[0022] FIG. 2 is a perspective view showing an example of the configuration of the decompression mechanism 50. The decompression mechanism 50 includes a cam lobe 51, a control member 53, an elastic member 57, and a pin member 58. Here, the cam lobe 51 is disposed on the exhaust cam 31 side, and the control member 53, the elastic member 57, and the pin member 58 are disposed on the rocker arm 34 side.

[0023] The cam lobe 51 is provided on the camshaft 33 and rotates integrally with the exhaust cam 31. Specifically, the cam lobe 51 is adjacent to the side of the exhaust cam 31 and is offset in the axial direction of the camshaft 33 so as to face the control member 53 and not face the roller 35 of the rocker arm 34. Further, the cam lobe 51 is formed in a circular shape and has a convex portion 52 having a mountain shape. When viewed from the axial direction of the camshaft 33, the convex portion 52 of the cam lobe 51 is positioned so as not to overlap with the convex portion 32 of the exhaust cam 31. In the example shown in FIG. 1, when viewed from the axial direction of the camshaft 33, the convex portion 52 of the cam lobe 51 and the convex portion 32 of the exhaust cam 31 are located on opposite sides of each other across the axis Oc of the camshaft 33.

[0024] The control member 53 is provided on the rocker arm 34 and is capable of transitioning between a first state in which it can contact the protrusion 52 of the cam lobe 51 and a second state in which it cannot contact the protrusion 52. The control member 53 is positioned offset from the roller 35 in the axial direction of the camshaft 33. The control member 53 is substantially plate-shaped and formed in a substantially rectangular shape when viewed from the axial direction of the camshaft 33. The control member 53 has a pivot point Op on one short side, a contact portion 54 on the other short side, and a curved recess 55 on one long side. The control member 53 is supported by the rocker arm 34 at the pivot point Op, causing the contact portion 54 to pivot about the pivot point Op. The pivot point Op is located on the opposite side of the axis Oc of the camshaft 33, with the rotation center of the roller 35 in between. Furthermore, the swing range of the control member 53 is restricted by the pin support portion 36 and the stopper portion 37 formed on the rocker arm 34. The first state is when the control member 53 swings and comes into contact with the pin support portion 36. In the first state, the contact portion 54 of the control member 53 can come into contact with the protrusion 52 of the cam lobe 51. On the other hand, the second state is when the control member 53 swings and comes into contact with the stopper portion 37. In the second state, the control member 53 cannot come into contact with the protrusion 52 of the cam lobe 51.

[0025] The elastic member 57 biases the control member 53 to always be in the first state. The elastic member 57 can be, for example, a torsion spring, and is disposed on the rocker arm 34 by supporting the coil portion on the pivot axis of the control member 53, engaging one arm with the control member 53, and engaging the other arm with the stopper portion 37.

[0026] The pin member 58 is supported so as to be able to move back and forth by the hole 38 of the pin support portion 36 of the rocker arm 34, and its tip is positioned to face the curved surface of the recess 55 of the control member 53. When hydraulic pressure is applied from the lash adjuster 39, the pin member 58 advances toward the control member 53 by the hydraulic force. The pin member 58 pushes the control member 53 from the first state to the second state against the restoring force of the elastic member 57. On the other hand, when the hydraulic pressure is no longer applied from the lash adjuster 39, the control member 53 is biased by the restoring force of the elastic member 57 to return to the first state, and the pin member 58 is pushed back by the control member 53 and retracts into the hole 38.

[0027] Figure 3 is a perspective view showing an example of the configuration of the rocker arm 34. As shown in Figure 3, the rocker arm 34 has an oil passage 60 that passes from the spherical portion 40 of the lash adjuster 39 to the hole 38. The oil passage 60 is formed inside one end of the rocker arm 34 so as to follow the width direction of the rocker arm 34. A portion of the oil supplied to the lash adjuster 39 travels from the spherical portion 40 through the oil passage 60 to the hole 38, causing the oil to push out the pin member 58 that had retracted into the hole 38. On the other hand, if oil is not supplied to the lash adjuster 39, the oil in the oil passage 60 and the hole 38 gradually leaks out along with the oil supplied to the lash adjuster 39.

[0028] Next, the operation of the valve train 30 in the engine 1 configured as described above, both when it is stopped and when it is running, will be explained with reference to Figure 4.

[0029] Figure 4(a) is a diagram illustrating the operation of the valve train 30 while the engine 1 is stopped. When engine 1 is stopped, the oil pump is not driven, and therefore oil is not supplied to the lash adjuster 39. Consequently, because no hydraulic pressure is applied from the lash adjuster 39, the control member 53 is biased by the elastic member 57 to return to the first state, causing the pin member 58 to be pushed back from the control member 53 and retract into the hole 38. In this way, when the control member 53 is in the first state, the convex portion 52 of the cam lobe 51 can contact the contact portion 54 of the control member 53. Therefore, even if the exhaust valve 19 were normally stopped in the position where the convex portion 32 of the exhaust cam 31 would not press against the roller 35 of the rocker arm 34, the convex portion 52 of the cam lobe 51 is in contact with the contact portion 54 of the control member 53, causing the rocker arm 34 to be pushed down toward the combustion chamber 15 via the control member 53. As a result, as shown in Figure 4(a), the exhaust valve 19 can maintain an open state.

[0030] Therefore, when starting the engine 1, a decompression process is performed to release the compressed air inside the cylinder of the cylinder block 11 through the exhaust port 17 as the piston 13 moves toward top dead center, thereby reducing the load on the engine 1 during startup.

[0031] Figure 4(b) is a diagram illustrating the operation of the valve train 30 when the engine 1 is started. When engine 1 starts and operates, the oil pump is driven and oil is supplied to the lash adjuster 39. A portion of the oil supplied to the lash adjuster 39 travels from the spherical part 40 through the oil passage 60 to the hole 38, pushing out the pin member 58 that had retracted into the hole 38, causing the pin member 58 to advance toward the control member 53. The pin member 58 pushes out the control member 53 against the restoring force of the elastic member 57, causing the control member 53 to transition to the second state and the decompression process to end. In the second state, the control member 53 cannot contact the protrusion 52 of the cam lobe 51, so the rocker arm 34 can open and close the exhaust valve 19 in accordance with the rotation of the exhaust cam 31 without being affected by the protrusion 52 of the cam lobe 51.

[0032] Next, the operation of the valve train 30 when the engine 1 is stopped from an operating state will be explained. The control member 53 does not transition from the second state to the first state at the moment the engine 1 stops, but rather transitions to the first state after a time lag from the stopping of the engine 1. In other words, when engine 1 stops, the oil pump is not driven and therefore oil is not supplied to the lash adjuster 39. However, oil remains inside the oil passage 60 and hole 38 of the rocker arm 34, and the pin member 58 remains extended toward the control member 53 due to the residual pressure, and the control member 53 maintains the second state. Subsequently, the oil inside the oil passage 60 and hole 38 of the rocker arm 34 gradually leaks out, and the restoring force of the elastic member 57 exceeds the force of the residual pressure, causing the pin member 58 to be pushed back by the elastic member 57 and retract, and the control member 53 transitions to the first state.

[0033] In this way, since the control member 53 transitions from the second state to the first state after a time lag following the stopping of the engine 1, the transition to the first state does not occur while the exhaust cam 31 is rotating at a high speed, thus preventing damage due to collision between the control member 53 and the cam lobe 51. Furthermore, even if the control member 53 and the cam lobe 51 collide when the engine 1 is stopped or started, the control member 53 will collide with the protrusion 52 that smoothly protrudes from the base surface of the cam lobe 51. Therefore, the generation of abnormal noise can be suppressed more effectively than in the conventional case where a steeply protruding lift pin collides with a rocker arm.

[0034] As described above, the valve train 30 of the internal combustion engine in this embodiment is configured such that one end of the rocker arm 34 is pivotably supported via a hydraulic lash adjuster 39, and the rocker arm 34 opens the exhaust valve 19 when pressed by the exhaust cam 31. The valve train 30 also includes a circular cam lobe 51 that rotates integrally with the exhaust cam 31 and has a convex portion 52, a control member 53 provided on the rocker arm 34 that transitions between a first state in which the rocker arm 34 opens the exhaust valve 19 by contacting the convex portion 52 and a second state in which it cannot contact the convex portion 52, and a pin member 58 that pushes the control member 53 from the first state to the second state when hydraulic pressure is applied from the lash adjuster 39.

[0035] In the first state, the control member 53 contacts the protrusion 52 of the cam lobe 51, causing the rocker arm 34 to open the exhaust valve 19, thereby reducing the load on the engine 1 during startup. Furthermore, the control member 53 transitions to the first state in accordance with the hydraulic pressure of the lash adjuster 39, regardless of the operating state of the engine 1. Therefore, according to the valve train 30 of this embodiment, the load on the engine 1 during startup can be reduced regardless of the operating state of the engine 1.

[0036] Furthermore, in this embodiment, the pin member 58 continuously pushes the control member 53 to the second state by applying hydraulic pressure from the lash adjuster 39 while the engine 1 is running. In this way, by the pin member 58 continuously pushing the control member 53 while the engine 1 is running, the control member 53 can be maintained in the second state in which it does not come into contact with the protrusion 52 of the cam lobe 51, thereby preventing interference with the opening and closing operation of the exhaust valve 19.

[0037] Furthermore, in this embodiment, the valve train 30 has an elastic member 57 that biases the control member 53 to a first state. The elastic member 57 pushes the control member 53 back to the first state when the engine 1 is stopped and hydraulic pressure is no longer applied to the pin member 58 from the lash adjuster 39. As the residual pressure in the rocker arm 34 gradually decreases and the restoring force of the elastic member 57 exceeds it, the elastic member 57 pushes the control member 53 back to the first state, thus allowing the engine 1 to transition to the first state after a time lag from the engine stopping.

[0038] In the above-described embodiment, the valve train 30 of the exhaust valve 19 was explained, but the valve train 30 of the intake valve 18 can be configured in the same way. Furthermore, although the above-described embodiment described the case where the elastic member 57 is a torsion spring, it is not limited to this case, and the elastic member 57 only needs to be able to bias the control member 53 to the first state, and may be made of, for example, rubber.

[0039] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and modifications can be made within the scope of the present invention. [Explanation of Symbols]

[0040] 1: Engine (internal combustion engine) 10: Engine body 18: Intake valve 19: Exhaust valve 30: Valve train 34: Rocker arm (lifter) 38: Hole 39: Lash adjuster 50: Decompression mechanism 51: Cam lobe 52: Protrusion 53: Control member 54: Contact part 55: Recess 57: Elastic member 60: Oil passage

Claims

1. A valve train for an internal combustion engine, wherein one end of a lifter is pivotably supported via a hydraulic lash adjuster, and the lifter opens the valve when pressed by a cam, A circular cam lobe that rotates integrally with the cam and has a convex portion with a mountain-like shape, A control member provided on the lifter, which is capable of contacting the protrusion and transitions between a first state in which the lifter opens the valve by contacting the protrusion, and a second state in which it cannot contact the protrusion, A valve train for an internal combustion engine, characterized by having a pin member which pushes the control member from the first state to the second state when hydraulic pressure is applied from the lash adjuster.

2. The valve train for an internal combustion engine according to claim 1, characterized in that the pin member continues to push the control member to the second state by applying hydraulic pressure from the lash adjuster while the internal combustion engine is in operation.

3. The control member has an elastic member that biases it to the first state, The valve train for an internal combustion engine according to claim 1 or 2, characterized in that the elastic member pushes the control member back to the first state when the operation of the internal combustion engine is stopped and hydraulic pressure is no longer applied to the pin member from the lash adjuster.

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