JPH0441910A - Valve driving device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the deterioration of startability due to the dead volume by providing a hydraulic pump on a cylinder head, and rotatively driving it with a cam shaft in a system selectively controlling the pressure oil fed from the hydraulic pump to a hydraulic cylinder to open or close an engine valve. CONSTITUTION:A plunger plate 17 is installed above the retainer 8 of an intake valve 5, and a plunger 19 kept in contact with the upper end of the stem 5a of the intake valve 5 at the lower end is inserted into a cylinder chamber 18 formed in the plunger plate 17. A valve body 20 is installed above the plunger plate 17 in a head cover 16, a pressure oil feed valve 21 and a pressure oil discharge valve 43 constituting a selector valve are provided on the valve body 20, which is electrically controlled to open or close the intake valve 5. Pressure oil is fed to the cylinder chamber 18. A hydraulic pump 39 is installed on a cylinder head 1 while it is supported by a stay 47, and it is rotatively driven by a cam shaft 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a valve driving device for an internal combustion engine, and more particularly to a valve driving device that can arbitrarily change valve timing and lift amount.

[Prior Art] Many valve drive devices that change valve timing and lift amount have been proposed for the purpose of improving the performance of internal combustion engines. An example of this is JP-A-64-
A hydraulic valve driving device described in Japanese Patent No. 69707 can be mentioned.

This valve drive device supplies pressure oil from a hydraulic pump to a hydraulic cylinder installed in the cylinder head via a switching valve, and opens and closes the valve with the hydraulic cylinder in accordance with the switching operation of the switching valve. The opening/closing timing and lift amount can be changed as desired.

Further, although the above-mentioned publication does not describe a specific method for installing the hydraulic pump, for example, as shown in FIGS. It is considered that the crankshaft 54 is used to drive the rotation. In this installation method, the pressure oil discharged from the hydraulic pump 51 is supplied to the not-illustrated switching valve and hydraulic cylinder on the cylinder head 56 side through the high-pressure pipe 55.

[Problems to be Solved by the Invention] However, when the hydraulic pump 51 is installed in the cylinder block 52 as described above, the hydraulic pump 51 and the switching valve and hydraulic cylinder on the cylinder head 56 side are separated from each other, so that the high-pressure piping 55 becomes longer, and the pressure oil volume (hereinafter referred to as dead volume) within the high pressure pipe 55 increases.

FIG. 8 is a diagram showing changes in the oil pressure in the high-pressure piping and the engine rotational speed when the engine is started. Even if the starter starts driving the crankshaft (time 1+),
The pressure oil inside does not rise quickly. It can be seen that the hydraulic cylinder resists the biasing force of the valve spring and opens the valve, and the engine start is completed after a considerable time has elapsed from the start of the engine (time t2). Therefore, when the method of installing the hydraulic pump 51 shown in FIGS. 6 and 7 is adopted, a problem arises in that the time required to start the internal combustion engine becomes extremely long and the startability deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a valve driving device for an internal combustion engine that can prevent deterioration of startability due to dead volume while making it possible to arbitrarily change valve timing and lift amount.

[Means for Solving the Problems] The present invention provides a camshaft that is provided in a cylinder head of an internal combustion engine and is rotationally driven by a crankshaft via a transmission mechanism to open and close one of intake and exhaust valves; a hydraulic cylinder provided in the cylinder head and connected to the other valve of the intake and exhaust valves; a hydraulic pump that discharges pressure oil for driving the other valve to open and close by hydraulic pressure; A pump and the hydraulic cylinder are connected to each other, and a high-pressure pipe that supplies pressure oil from the hydraulic pump to the hydraulic cylinder is switched and controlled between a high-pressure pipe that supplies pressure oil from the hydraulic pump to the hydraulic cylinder via the high-pressure pipe, and the valve is controlled. The gist of the present invention is a valve drive device for an internal combustion engine, which includes a switching valve that opens and closes, and in which the hydraulic pump is installed in a cylinder head and rotated by a camshaft.

[Operation] When the crankshaft rotates, the camshaft is rotationally driven via the transmission mechanism, and one of the intake and exhaust valves is opened and closed. Further, a hydraulic pump is driven by this camshaft, and pressurized oil discharged from the pump is supplied to a hydraulic cylinder via a high-pressure pipe. This pressure oil is switched and controlled by a switching valve, and as a result, the other one of the intake and exhaust valves is opened and closed by the hydraulic cylinder. At this time, multiple values such as valve opening/closing timing, opening/closing speed, and lift amount are adjusted by the switching valve to values according to the operating status of the internal combustion engine.

In the above-mentioned valve drive device, since the hydraulic pump is provided in the cylinder head, the path length of the high-pressure piping connecting the hydraulic pump, the switching valve, and the hydraulic cylinder is shortened. Therefore, the amount of pressurized oil in the high-pressure piping, the so-called dead volume, is reduced, and the oil pressure is effectively transmitted to the hydraulic cylinder even when the engine speed is low and the discharge amount of the hydraulic pump is low, such as during startup.

[Embodiment] Hereinafter, an embodiment in which the present invention is embodied in a valve drive device for driving an intake valve side of an internal combustion engine will be described with reference to FIGS. 1 to 5.

FIG. 3 is a sectional view of a cylinder head of an internal combustion engine. As shown in this figure, a combustion chamber 2 and intake and exhaust ports 3 and 4 are formed in a cylinder head 1, and intake and exhaust valves 5 and 6 are movable up and down to open and close each intake and exhaust port 3 and 4. It is provided. The upper ends of the stems 5a and 6a of each valve 5 and 6 protrude into the mechanism chamber 7 and a retainer 8 is attached thereto, and a valve spring 9 is provided between the retainer 8 and the lower wall of the mechanism chamber 7.
is interposed to bias each valve 5, 6 toward the closing side.

FIG. 1 is a plan sectional view of the cylinder head 1, and FIG. 2 is a diagram showing the positional relationship between the camshaft and the crankshaft. As shown in these figures and FIG. 3, a lifter IO is attached to the retainer 8 of the exhaust valve 6, and the cam lla of the camshaft 11 is in contact with the lifter IO. The camshaft 11 is rotatably supported and is rotationally driven by a crankshaft 15 via a pair of timing pulleys 12, 13 and a timing belt 14. When the camshaft 11 rotates, the exhaust valve 6 opens and closes the exhaust port 4 while expanding and contracting the valve spring 9. Incidentally, a pair of head covers 16 are mounted on the cylinder head 1 to accommodate the above-mentioned camshaft 11 and a valve driving device described below. Further, in this embodiment, the timing pulleys 12 and 13
and the timing belt 14 constitute a transmission mechanism.

FIG. 4 is a diagram schematically showing the valve driving device.

As shown in this figure and FIG. 3, a plunger plate 17 is installed above the retainer 8 of the intake valve 5,
A cylinder chamber 18 is formed in this plunger plate 17 so as to correspond to the stem 5a of the intake valve 5. A plunger 19 is disposed within the cylinder chamber 18 so as to be movable up and down, and the lower end of the plunger 19 is in contact with the upper end of the stem 5a of the intake valve 5. In this embodiment, the cylinder chamber 18 and plunger 19 constitute a hydraulic cylinder.

Plunger plate 1 in the helad cover 16
A valve body 20 is installed above the valve 7, and this valve body 20 is provided with a pressure oil supply valve 21 that constitutes a switching valve. To explain this pressure oil supply valve 21, a valve chamber 22 is formed in the valve body 20.
A high pressure port 23 and an operating pressure port 24 are formed to open upward. Further, a distribution port 25 is formed in the valve chamber 22 so as to communicate with the cylinder chamber 18 of the plunger plate 17. A spool 26 is slidably disposed within the valve chamber 22, and this spool 26 connects and disconnects the high pressure port 23 and the distribution port 25. Further, one end of the spool 26 is located within the operating pressure port 24, and the other end faces into a pump chamber 27 formed in the valve body 20.

An inlet port 2 having a restriction is provided on one side of the pump chamber 27.
8 is formed. Further, this pump chamber 27 is closed by a cap 29, and a piston 30 is placed inside the pump chamber 27.
It is divided by. A piezo stack 31 is held between the piston 30 and the cap 29, and the piston 30 is urged toward the piezo stack 31 by a disc spring 32. This piezo stack 31 is manufactured by laminating several liters of piezoelectric plates with current-carrying electrodes arranged on both sides of a piezoelectric plate with a thickness of approximately 0.5 mm, which is made of lead zirconate titanate as a main component. It has the property of elongating several tens of μm depending on the size of the wire.

The piezo stack 31 is connected to an external computer 34 via a signal line 33. this computer 3
4 is connected to the vehicle's accelerator opening sensor 35, engine speed sensor 36, engine cooling water temperature sensor 37, etc., and the computer 34 controls the expansion and contraction operation of the piezo stack 31 based on detection signals from these sensors. It has become. The piston 30 reciprocates within the pump chamber 27 in accordance with the expansion and contraction of the piezo stack 31.

As shown in FIG. 4, the high pressure port 23 is connected to the high pressure piping 3.
8 to the hydraulic pump 39, and the working pressure port 2
4 and the inlet port 28 are connected to an operating pressure pipe 40. The oil pressure in the high pressure pipe 38 is adjusted to 60 liters by the pressure regulating valve 41.
~400kg/crl, working pressure piping 4
The oil pressure within 0 ranges from 10 to 100 kg/by the pressure regulating valve 42.
It is set to cJ.

On the other hand, as shown in FIGS. 3 and 4, the valve body 20 is provided with a pressure oil discharge valve 43 that constitutes a switching valve having the same configuration as the pressure oil supply valve 21 described above (part of which is shown in FIG. 3). show)
, both valves 21 and 43 are in communication via a distribution port 25. The spool 44 of the pressure oil discharge valve 43 connects to the distribution port 25, and the pressure oil in the distribution port 25 is transferred to the oil tank 45.
The drain pipe 46 (shown in FIG. 4) for returning to the original state is disconnected.

As shown in FIGS. 1 and 2, the hydraulic pump 39 is installed in the cylinder head 1 while being supported by a stay 47, is connected to the rear end of the camshaft 11, and is rotationally driven by the camshaft 11. It has become so. The high pressure piping 38 is formed within the stay 47 and a piping plate 48 (shown in FIG. 3), and pressure oil is supplied from the piping plate 48 to the high pressure port 23. still,
As shown in FIG. 3, the piping plate 48 includes high pressure piping 3.
8, the working pressure pipe 40 and the drain pipe 46 are also formed.

Next, the operation of the valve drive device for an internal combustion engine configured as described above will be explained.

When the camshaft 11 is rotationally driven by the crankshaft 15 via the timing belt 14, the cam l
The lifter 10 of the exhaust valve 6 is pushed down by la.
The exhaust valve 6 is opened against the urging force of the valve spring 9. In this way, the exhaust valve 6 is opened and closed according to the rotation of the camshaft 11, and its valve timing and lift amount are determined by the shape of the cam lla.

Further, as the camshaft 11 rotates, the hydraulic pump 39 is rotationally driven, and the pressure oil discharged from the hydraulic pump 39 is supplied to the pressure oil supply valve 21 via the high pressure pipe 38 and the working pressure pipe 40, respectively. .

The computer 34 outputs an actuation signal to the pressure oil supply valve 21, and the actuation signal causes the piezo stack 31 to expand and move the piston 30 in the pump chamber 27 to the right in FIG. At this time, the hydraulic pressure in the pump chamber 27 temporarily increases to move the spool 26 to the right, thereby establishing communication between the high pressure port 23 and the distribution port 25. the result,
Pressure oil from the high-pressure pipe 38 is introduced into the cylinder chamber 18 through the high-pressure port 23 and the distribution port 25, and the plunger 19 opens the intake valve 5 against the urging force of the valve spring 9.

Further, when the computer 34 stops outputting the actuation signal, the piezo stack 31 is stripped of its accumulated charge and contracts to its original form. Therefore, ``the piston 30 is the disc spring 3
2 to the left, and at the same time the spool 26 is moved to the left by the hydraulic pressure in the operating pressure port 24. As a result, the high-pressure port 23 and the distribution port 25 are cut off, and the pressure oil trapped in the cylinder chamber 18 causes the intake valve 5
is held open.

Further, when an actuation signal is input to the pressure oil discharge valve 43 by the computer 34, the spool 44 is moved as the piezo stack (not shown) extends, and the above-mentioned distribution port 2 is moved.
5 is connected to a drain pipe 46. Therefore, the pressure oil in the cylinder chamber 18 is collected into the oil tank 45 through the distribution port 25 and the drain pipe 46, and the intake valve 5 is returned to the closed state by the biasing force of the valve spring 9. In this way, the intake valve 5 has a pressure oil supply valve 21 and a pressure oil discharge valve 43.
It is opened and closed by its valve timing, opening and closing speed,
Multi-values such as the lift amount are always controlled to optimal values by the computer 34 based on the accelerator opening, engine speed, engine cooling water temperature, etc. detected by the sensors 35 to 37.

On the other hand, when the internal combustion engine is restarted after being stopped for a long time, the oil pressure in the high pressure pipe 38 has decreased to approximately atmospheric pressure due to the stoppage of the hydraulic pump 39. Now, when the crankshaft 15 is rotated by the starter (hereinafter referred to as cranking), the camshaft 11 is rotationally driven via the timing belt 14. Therefore, the camshaft 11
As the exhaust valve 6 is rotated, the exhaust valve 6 is opened and closed, and the hydraulic pump 39 is rotationally driven to discharge pressure oil. When the oil pressure in the high pressure pipe 38 increases, the computer 34 opens and closes the intake valve 5 at a speed corresponding to the cranking rotation speed.
As a result, the internal combustion engine is started. The engine speed during cranking is approximately 200 rpm, which is extremely low compared to idling. Therefore, the intake valve 5 is opened and closed after the oil pressure in the high-pressure pipe 38 rises to a predetermined value or more, and is slightly delayed from immediately after the start of cranking.

By the way, in the valve drive device of this embodiment, since the hydraulic pump 39 is provided in the cylinder head 1, the path length of the high pressure piping 38 connecting the hydraulic pump 39, the pressure oil supply valve 21, and the pressure oil discharge valve 43 is is very short. Therefore,
The amount of pressurized oil in the high-pressure pipe 38, the so-called dead volume, is small, and even when the above-mentioned engine speed is low (and the discharge amount of the hydraulic pump 39 is low), the oil pressure in the high-pressure pipe 38 quickly rises. Hydraulic pressure is effectively transmitted into the cylinder chamber 18.

FIG. 5 is a diagram showing changes in the oil pressure in the high pressure pipe 38 and the engine rotational speed at the time of startup, and as shown in this diagram,
The oil pressure in the high pressure pipe 38 starts cranking (time 1+)
It can be seen that the engine quickly rises thereafter, the intake valve 5 is opened and closed, and the engine is immediately started (time t2). Therefore, in the valve driving device of this embodiment, the time required for starting is very short, and as mentioned above, the high pressure piping 38 contains 60 to 400 kilometres.
Pressure oil with a high pressure of g/crl flows, and the pressure oil is accompanied by large pulsations according to the opening and closing operations of the pressure oil supply valve 2I and the pressure oil discharge valve 43. Therefore, if the high-pressure piping 38 is made of a material with low rigidity, such as a rubber hose, there is a risk that the pulsation of the pressure oil will resonate and cause noise. However, in the valve drive device of this embodiment, the high pressure pipe 38 is provided within the highly rigid pipe plate 48 and the stay 47, so the noise caused by the pressure oil is reduced.

As described above, in the valve drive device for an internal combustion engine of this embodiment, the hydraulic pump 39 is provided in the cylinder head 1 and is rotationally driven by the camshaft 11.

Therefore, the path length of the high-pressure pipe 38 that connects the hydraulic pump 39, the pressure oil supply valve 21, and the pressure oil discharge valve 43 is shortened, and the dead volume is reduced, so that the oil pressure in the high-pressure pipe 38 is quickly increased when the engine is started. The engine can be started immediately by raising the engine to Therefore, the time required for starting can be shortened and the startability of the internal combustion engine can be significantly improved.

Furthermore, since the high-pressure pipe 3B, which is a source of noise, is provided within the pipe plate 48 and the stay 47, noise caused by pressure oil can be reduced and the quietness of the internal combustion engine can be improved.

In addition, since the existing camshaft 11 is used to drive the hydraulic pump 39 as described above, for example, the hydraulic pump 39 on the cylinder head 1 side can be driven by the crankshaft 15 via a belt, chain, gear, etc. There's no need to. Therefore, the structure of the internal combustion engine can be simplified.

Note that the present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the camshaft 11 was rotationally driven via the timing belt 14, but this camshaft 1
1 may be driven via a chain or gears.

Further, in the above embodiment, the exhaust valve 6 was driven by the camshaft 11 and the intake valve 5 was driven by hydraulic pressure, but conversely, the intake valve 5 was driven by the camshaft 11 and the exhaust valve 6 was driven by hydraulic pressure. Good too.

[Effects of the Invention] As detailed above, according to the valve drive device for an internal combustion engine of the present invention, it is possible to arbitrarily change the valve timing and lift amount, and also prevent deterioration of startability due to dead volume. It has the excellent effect of being able to

[Brief explanation of the drawing]

Figure 1 is a cross-sectional plan view of a cylinder head incorporating the valve drive device of the embodiment, Figure 2 is a diagram showing the positional relationship between the camshaft and crankshaft, Figure 3 is a cross-sectional view of the cylinder head, and Figure 4 Figure 5 is a diagram showing the outline of the valve drive device, Figure 5 is a diagram showing the change in oil pressure in the high-pressure piping and engine speed at startup, and Figures 6 and 7 are how to install a hydraulic pump in a conventional valve drive device. FIG. 8 is a diagram showing changes in the oil pressure in the high-pressure pipe and the engine rotational speed at the time of starting the conventional valve driving device. ■ is the cylinder head, 5 is the intake valve, 6 is the exhaust valve, -11 is the camshaft, 12.13 is the timing pulley that makes up the transmission mechanism, 14 is the timing belt that makes up the transmission mechanism, 18 is the hydraulic cylinder A cylinder chamber, 19 a plunger constituting a hydraulic cylinder, 21 a pressure oil supply valve constituting a switching valve, 38 a high pressure pipe, 39 a hydraulic pump, and 43 a pressure oil discharge valve constituting a switching valve.

Claims (1)

[Claims] 1. A camshaft provided in a cylinder head of an internal combustion engine and rotationally driven by a crankshaft via a transmission mechanism to open and close one of the intake and exhaust valves; a hydraulic cylinder connected to the valve on the other side; a hydraulic pump that discharges pressure oil for opening and closing the valve on the other side using hydraulic pressure; and a hydraulic cylinder connecting the hydraulic pump and the hydraulic cylinder, and A valve drive device for an internal combustion engine, comprising: a high-pressure pipe that supplies pressure oil to a hydraulic cylinder; and a switching valve that opens and closes the valve by switching and controlling the pressure oil that is supplied from the hydraulic pump to the hydraulic cylinder via the high-pressure pipe. A valve drive device for an internal combustion engine, characterized in that the hydraulic pump is provided in a cylinder head and rotationally driven by a camshaft.