JP2009281158A - Sealed hydraulic tappet for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed hydraulic tappet for an engine capable of completely eliminating a valve head clearance without relying on an oil pump. <P>SOLUTION: This hydraulic tappet T includes a cylinder 30, a piston 32 slidably fitted with the inner peripheral face of the cylinder 30 and partitioning the inner side thereof into a first oil chamber 33 on a first end wall 30a side and a second oil chamber 34 on a second end wall 30b side, a piston rod 36 fixed to the piston 32 and penetrating a shaft hole 31 of the second end wall 30b, a spring 37 for urging the piston 32 to the second oil chamber 34 side by a set load smaller than a set load of a valve spring 15, a one-way valve 38 for allowing only the flow of oil in one direction from the second oil chamber 34 to the first oil chamber 33, a volume change absorbing means 40 for absorbing the change in volume of the piston rod 36 occupying the cylinder 30, and a throttle passage 39 for connecting the first and second chambers 33, 34 to allow slow movement of the piston 32 to the first oil chamber 33 side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in a sealed hydraulic tappet for an engine that is interposed between two members of a valve operating device that mutually exchange operating force in order to make the valve head clearance of the engine zero.

Such a valve operating device for an internal combustion engine is already known as disclosed in Patent Document 1 below.
JP-A-10-54213

  In conventional closed type hydraulic tappets for such engines, an oil pump for constantly replenishing oil leakage is required in the oil chamber between the cylinder and the piston, and a long oil is introduced from the oil pump to the hydraulic tappet. I need a road. Therefore, it could not be applied to a small engine without an oil pump.

  SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is intended to provide a sealed hydraulic tappet for an engine that can make the valve head gap zero without relying on an oil pump and without forming a long oil passage. The purpose is to provide.

  In order to achieve the above-described object, the present invention provides a sealed hydraulic pressure for an engine that is interposed between two members of a valve operating device that exchange valve operating force with each other in order to make the valve head clearance of the engine zero. In the tappet, a cylinder having a first end wall closed at one end in the axial direction and a second end wall with a shaft hole at the other end, and a slidably fitted to the inner peripheral surface of the cylinder, A piston that partitions the first oil chamber on the first end wall side and a second oil chamber on the second end wall side, and a piston that is fixed to the piston and slidably and liquid-tightly penetrates the shaft hole A rod, a spring that biases the piston toward the second oil chamber with a set load smaller than the set load of the valve spring, and the flow of oil in only one direction from the second oil chamber to the first oil chamber is allowed. A one-way valve that absorbs changes in the volume of the piston rod that occupies the cylinder And a throttle passage communicating between the first and second chambers to allow slow movement of the piston toward the first oil chamber, and the cylinder and piston rod are connected between the two members. The first feature is that it is interposed.

  In addition to the first feature, the present invention provides the one-way valve, a valve chamber provided in the piston and opened to the first oil chamber, and a valve communicating the valve chamber with the first oil chamber. A second feature is that it is constituted by a hole and a valve body provided in the valve chamber, which closes the valve hole when the first oil chamber is pressurized and opens the valve hole when the second oil chamber is pressurized. To do.

  Furthermore, in addition to the first feature, the present invention has a third feature that the throttle passage is configured by a sliding gap between the cylinder and the piston.

  Furthermore, in addition to the first feature, the present invention is such that, as a volume change absorbing means, an elastic seal member that seals the shaft hole in close contact with the outer peripheral surface of the piston rod is attached to the cylinder. According to a fourth feature of the present invention, a change in volume of the piston rod occupying the cylinder is absorbed by elastic deformation of the cylinder.

  According to the first feature of the present invention, the hydraulic tappet is configured to be a hermetically sealed type, so that the piston and the piston rod can be raised and lowered without using an oil pump, and the valve head clearance of the engine valve can be made zero. Can contribute to the reduction of engine noise.

  According to the second feature of the present invention, the one-way valve can be entirely accommodated in the piston, and therefore, it is not necessary to form an oil passage for the one-way valve in the cylinder, which contributes to the compactness of the hydraulic tappet. obtain.

  According to the third aspect of the present invention, it is not necessary to form orifices in the cylinder and the piston, which can contribute to the compactness of the hydraulic tappet.

  According to the fourth feature of the present invention, it is not necessary to provide special volume change absorbing means in the cylinder, which can contribute to the compactness of the hydraulic tappet.

  Embodiments of the present invention will be described below based on preferred embodiments of the present invention shown in the drawings.

  FIG. 1 is a longitudinal sectional front view of a main part of a general-purpose engine having a sealed hydraulic tappet according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along line 2-2 in FIG. 1, and FIG. 4 and 4 are cross-sectional views taken along line 4-4 of FIG. 2, FIG. 5 is an operation explanatory diagram corresponding to FIG. 2, and FIG. 6 is another operation explanatory diagram corresponding to FIG.

  First, in FIG. 1, an engine body 1 of a general-purpose engine E is joined to a crankcase 2, a cylinder block 3 extending obliquely upward from one side of the crankcase 2, and an upper end of the cylinder block 3. It is composed of a cylinder head 4. In the crankcase 2, the crankshaft 6 is accommodated and supported, and the crankshaft 6 is connected via a connecting rod 8 to a piston 7 fitted in the cylinder bore 3 a of the cylinder block 3. An oil dipper 9 is attached to the large end of the connecting rod 8. The oil dipper 9 scatters the lubricating oil stored at the bottom of the crankcase 2 when the crankshaft 6 rotates, and lubricates each part in the engine E with the generated oil droplets. Therefore, this engine E is not provided with an oil pump.

  The cylinder head 4 is formed with a combustion chamber 10 connected to the cylinder bore 3a, and an intake port 11 and an exhaust port (not shown) that open the inner end of the combustion chamber 10, and the intake port 11 and the exhaust port. An intake valve 12 and an exhaust valve (not shown) for opening and closing the valve are provided. Hereinafter, the intake valve 12 and the exhaust valve are collectively referred to as the engine valve 12.

  The engine valve 12 is provided with a valve spring 15 for urging it in the valve closing direction. A valve operating device 16 that opens and closes the engine valve in cooperation with the valve spring 15 is disposed from the crankcase 2 to the cylinder head 4. Reference numeral 17 denotes a spark plug.

  The engine valve 12 is opened and closed by a valve gear 16 that cooperates with the valve spring 15. The valve gear 16 includes a cam shaft 20 that is received and supported in the crankcase 2 and disposed below the crankshaft 6. The crankshaft 6 rotates between the crankshaft 6 and the camshaft 20. Is provided with a gear-type timing transmission 21 that decelerates the gear to a half and transmits it.

  On the other hand, a rocker arm 22 is swingably supported on the cylinder head 4 via a fulcrum member 23. The rocker arm 22 has one end abutting against the valve head of the engine valve 12 and the other end pushed to a push rod. 24 so as to be in contact with 24. The push rod 24 is disposed in the guide hole 25 formed on the cylinder block 3 and the cylinder head 4 and adjacent to the lower side of the cylinder bore 3a, and between the push rod 24 and the cam 20a of the cam shaft 20. The sealed hydraulic tappet T of the present invention (hereinafter simply referred to as a hydraulic tappet) is interposed.

  Therefore, if the cam 20a lifts the hydraulic tappet T by the rotation of the cam shaft 20, the lift force is transmitted to the rocker arm 22 via the intake push rod 24, and this is shaken in the valve opening direction of the engine valve 12. When the lift force of the cam 20a with respect to the hydraulic tappet T is released, the repulsive force of the valve spring 15 closes the engine valve 12 and swings the intake rocker arm 22 in the opposite direction to the previous time. Thus, the hydraulic tappet T is pressed against the base surface of the cam 20a, and the engine valve 12 is opened and closed by repeating this operation.

  By the way, the engine body 1 is made of an aluminum alloy, and the push rod 24 is made of iron having a smaller thermal expansion coefficient than the aluminum alloy. Therefore, the valve head gap, that is, the gap between the engine valve 12 and the rocker arm 22 tends to increase during normal operation when the engine E is at a high temperature due to the difference in coefficient of thermal expansion of these materials. As E cools down after shutdown, the valve gap tends to decrease.

  Thus, the hydraulic tappet T is configured as follows so that the valve head gap is always zero even when the temperature of the engine E changes.

  2 and 3, the hydraulic tappet T includes a cylinder 30 having a flange-shaped first end wall 30a closed at one end in the axial direction, a second end wall 30b with a shaft hole 31 at the other end, A piston 32 that is slidably fitted to the inner peripheral surface and partitions the inside of the cylinder 30 into a first oil chamber 33 on the first end wall 30a side and a second oil chamber 34 on the second end wall 30b side; The piston 32 is fixed to the piston 32 and slidably and liquid-tightly penetrates the shaft hole 31, and the piston 32 is moved toward the second oil chamber 34 with a set load smaller than the set load of the valve spring 15. A biasing spring 37, a one-way valve 38 that allows oil to flow from the second oil chamber 34 to the first oil chamber 33 in only one direction, and a cylinder 30 for sealing the shaft hole 31 are mounted. An annular elastic seal member 40 and the first of the piston 32 Constituted by the throttle passage 39 communicating between the first and second chambers 33 and 34 to permit a slow transfer to the chamber 33 side.

  The annular elastic seal member 40 surrounds the piston rod 36 and is sandwiched between the second end wall 30b of the cylinder 30 and the annular partition wall 31c protruding from the intermediate portion of the inner peripheral surface of the cylinder 30. Is mounted on the cylinder 30. An inner lip 40a that is in close contact with the outer peripheral surface of the piston rod 36 on the inner peripheral side and an outer lip 40b that is in close contact with the inner peripheral surface of the cylinder 30 on the outer peripheral side are provided at the end of the elastic seal member 40 on the partition wall 31c side. Between the inner peripheral surface of the elastic seal member 40 and the outer peripheral surface of the piston rod 36, and between the outer peripheral surface of the elastic seal member 40 and the inner peripheral surface of the cylinder 30 so as to be adjacent to the lips 40a and 40b. Are provided with gaps 42, 42. These gaps 42 and 42 allow the elastic seal member 40 to be compressed and deformed to absorb the change in the volume of the piston rod 36 that occupies the cylinder 30.

  Thus, the cylinder 30 is slidably fitted into the guide hole 25, the cam 20a is slidably contacted with the first end wall 30a of the cylinder, and is pushed into the engaging recess 44 formed at the outer end of the piston rod 36. The end of the rod 24 is engaged. Thus, the cylinder 30 and the piston rod 36 are interposed between the cam 20a and the push rod 24.

  The one-way valve 38 is provided in a valve chamber 46 provided in the piston 32, a valve hole 47 communicating the valve chamber 46 with the first oil chamber 33, and the valve chamber 46. The valve hole 47 is closed and is configured by a valve body 48 that opens the valve hole 47 when the pressure of the second oil chamber 34 is increased. The valve chamber 46 is connected to the second through a plurality of through holes 49, 49... (See FIG. 4). The oil chamber 34 is open. A lateral hole 43 that communicates the valve hole 47 with the second oil chamber 34 is provided at the base of the piston rod 36.

  Further, as shown in FIG. 2, the throttle passage 39 is constituted by a sliding gap (for example, 20 μm) between the cylinder 30 and the piston 32. As an alternative, the first and second oil chambers 33 and 34 can be communicated with each other by an orifice provided in the piston 32.

  Next, the operation of this embodiment will be described.

  When the temperature of the engine E after start-up rises with time, the cam 20a supports the first end wall 30a of the cylinder 30 of the hydraulic tappet T at its base circle, so that the engine valve 12 becomes a valve spring. When closed with an urging force of 15, the difference in thermal expansion coefficient between the aluminum alloy engine body 1 and the iron push rod 24 causes the valve head gap of the engine valve 12, that is, between the engine valve 12 and the rocker arm 22. A gap is generated, and as a result, the hydraulic tappet T becomes unloaded. Then, as shown in FIG. 2, in the hydraulic tappet T, when the spring 37 pushes up the piston 32 to the second oil chamber 34 side by the set load, and the second oil chamber 34 is boosted as the piston 32 rises. At the same time, since the first oil chamber 33 is depressurized, the one-way valve 38 opens, the oil in the second oil chamber 34 flows through the one-way valve 38 to the first oil chamber 33, and the hydraulic tappet T Elongate as. As a result, the piston rod 36 integral with the piston 32 pushes up the push rod 24, so that the rocker arm 22 swings so as to make the valve head gap zero, that is, contact the valve head of the engine valve 12.

  When the valve head clearance becomes zero in this way, the rotation of the cam 20a proceeds and the nose portion lifts the cylinder 30, and the lift force acts as an axial compressive load between the cylinder 30 and the piston rod 36. As shown in FIG. 5, when the piston 32 is pressed toward the first oil chamber 33, the first oil chamber 33 is pressurized and simultaneously the second oil chamber 34 is depressurized. Close and stop the flow of oil from the first oil chamber 33 to the second oil chamber 34. As a result, the piston 32 is in a hydraulic lock state, and the hydraulic tappet T does not contract in the axial direction. Therefore, the lift force of the cam 20a is reliably transmitted from the hydraulic tappet T to the push rod 24 and the rocker arm 22 to The valve 12 can be opened accurately.

  Next, when the temperature of the engine E decreases due to heat dissipation after the operation is stopped, the load of the valve spring 15 is resisted by the difference in thermal expansion coefficient between the engine body 1 made of aluminum alloy and the push rod 24 made of iron. In this case, the hydraulic tappet T receives a compressive load from the cam 20a and the push rod 24, and this state continues for a long time. Become. Then, as shown in FIG. 6, since the piston 32 continues to be pressed against the load of the spring 37 toward the first oil chamber 33, the first oil chamber 33 becomes high pressure and the oil in the first oil chamber 33 is throttled. The hydraulic tappet T is gradually moved through the passage 39, that is, the sliding gap 39 between the cylinder 30 and the piston 32, and the hydraulic tappet T is contracted. When there is no more, the movement of the piston 32 stops. As a result, it is possible to ensure the closed state of the engine valve 12 while maintaining the zero state of the valve head gap, and it is possible to cope with the next engine start. It should be noted that the throttle passage 39 exhibits a great throttle resistance when an instantaneous pressure difference is generated between the first and second oil chambers 33, 34, and the first and second oil chambers 33, 34 are displayed. Therefore, the instantaneous hydraulic lock state of the hydraulic tappet T during operation of the engine E is not affected.

  By the way, in the above action of the hydraulic tappet T, when the piston rod 36 moves up and down in the cylinder 30 together with the piston 32, the volume of the piston rod 36 occupying the cylinder 30 changes. It is absorbed by the elastic deformation of the elastic seal member 40 that seals the shaft hole 31 of the cylinder 30 in close contact with the surface and the outer peripheral surface of the piston rod 36. Therefore, the elastic seal member 40 corresponds to the volume change absorbing means 40 that absorbs the change in the volume of the piston rod 36 in the cylinder 30.

  Thus, the hydraulic tappet T is configured to be a hermetically sealed type, so that the piston 32 and the piston rod 36 can be raised and lowered without using an oil pump, the valve head clearance of the engine valve 12 can be reduced to zero, and the engine E This can contribute to reduction of operating noise.

  The one-way valve 38 includes a valve chamber 46 provided in the piston 32 and opened to the first oil chamber 33, a valve hole 47 that communicates the valve chamber 46 with the first oil chamber 33, and a valve chamber 46. It is provided with a valve body 48 that closes the valve hole 47 when the pressure of the first oil chamber 33 is increased and opens the valve hole 47 when the pressure of the second oil chamber 34 is increased. Therefore, it is not necessary to form an oil passage for the one-way valve 38 in the cylinder 30, which can contribute to the compactness of the hydraulic tappet T.

  Furthermore, since the throttle passage 39 is constituted by the sliding gap 39 between the cylinder 30 and the piston 32, it is not necessary to form an orifice in the cylinder 30 and the piston 32, and can contribute to the compacting of the hydraulic tappet T.

  Furthermore, an elastic seal member 40 that seals the shaft hole 31 in close contact with the inner peripheral surface of the cylinder 30 and the outer peripheral surface of the piston rod 36 is attached to the cylinder 30 as the volume change absorbing means 40. Since the elastic deformation causes the change in the volume of the piston rod 36 in the cylinder 30 to be absorbed, it is not necessary to provide a special volume change absorbing means in the cylinder 30, which can contribute to the compactness of the hydraulic tappet T.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the sealed hydraulic tappet T of the present invention can be applied to various types of valve gears. For example, in an overhead camshaft type valve gear, it can be interposed between the rocking end of the rocker arm and the valve head, and is installed at the fulcrum of the rocker arm as disclosed in Patent Document 1. You can also.

The principal part longitudinal section front view of a general purpose engine provided with the enclosed hydraulic tappet concerning the example of the present invention. 2-2 line expanded sectional view of FIG. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. Action explanatory drawing corresponding to FIG. Another operation explanatory view corresponding to FIG.

Explanation of symbols

E .... Internal combustion engine T ..... Closed hydraulic tappet 16 ... Valve-operated device 20a, 24 ... Two members of valve-operated device (cam, push rod)
30 ... Cylinder 30a ... First end wall 30b ... Second end wall 31 ... Shaft hole 32 ... Piston 33 ... First oil chamber 34 ... Second oil chamber 35 ... Piston rod 37 ... Spring 38 ... One-way valve 39 ... Throttle passage (sliding gap)
40... Volume change absorbing means (elastic seal member)
46 ... Valve 47 ... Valve 48 ... Valve

Claims (4)

In order to make the valve head clearance of the engine (E) zero, the engine closed hydraulic tappet interposed between the two members (20a, 24) of the valve operating device (16) that exchange valve operating force with each other. In
A cylinder (30) having a first end wall (30a) closed at one end in the axial direction, a second end wall (30b) with a shaft hole (31) at the other end, and an inner peripheral surface of the cylinder (30) The first oil chamber (33) on the first end wall (30a) side and the second oil chamber (34) on the second end wall (30b) side inside the cylinder (30) are movably fitted. Set load of a piston (32) that is divided into a piston rod, a piston rod (36) fixed to the piston (32) and penetrating through the shaft hole (31) in a fluid-tight manner, and a valve spring (15) A spring (37) for urging the piston (32) toward the second oil chamber (34) with a smaller set load, and one direction from the second oil chamber (34) to the first oil chamber (33) A one-way valve (38) that allows only oil flow, and the piston rod (36) that occupies the cylinder (30). Volume change absorbing means (40) for absorbing the volume change of the first and second chambers (33, 33) to allow slow movement of the piston (32) toward the first oil chamber (33). 34) A closed hydraulic pressure for an engine comprising a throttle passage (39) communicating with each other, wherein the cylinder (30) and the piston rod (36) are interposed between the two members (20a, 24). Tappet. The sealed hydraulic tappet for an engine according to claim 1,
The one-way valve (38) is provided in the piston (32) and opened to the first oil chamber (33), and the valve chamber (46) is connected to the first oil chamber (33). ) And a valve hole (47) that communicates with the valve chamber (46). When the pressure of the first oil chamber (33) is increased, the valve hole (47) is closed and the second oil chamber (33) A sealed hydraulic tappet for an engine characterized by comprising a valve body (48) that opens the valve hole (47) at the time of pressure increase. The sealed hydraulic tappet for an engine according to claim 1,
A sealed hydraulic tappet for an engine, wherein the throttle passage (39) is constituted by a sliding gap (39) between the cylinder (30) and the piston (32). The sealed hydraulic tappet for an engine according to claim 1,
As the volume change absorbing means (40), an elastic seal member (40) that seals the shaft hole (31) in close contact with the outer peripheral surface of the piston rod (36) is mounted on the cylinder (30). A sealed hydraulic tappet for an engine, wherein the change in volume of the piston rod (36) in the cylinder (30) is absorbed by elastic deformation of the member (40).

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