JP4900296B2 - Variable phase valve mechanism for internal combustion engine - Google Patents

Description

  The present invention relates to a variable phase valve mechanism for an internal combustion engine, and more particularly to a variable phase valve mechanism that can move hydraulic oil using torque fluctuations of a camshaft.

  A device is known that can change the phase of a valve by moving hydraulic oil between an advance chamber and a retard chamber using torque fluctuations of the cam shaft (see, for example, Patent Document 1).

JP 2005-147153 A

  However, when the internal combustion engine is at a low temperature, the friction increases because the viscosity of the working oil (lubricating oil) increases or the clearance decreases due to the difference in thermal expansion coefficient between the camshaft and its bearing. As a result, the negative torque that acts on the camshaft required to advance the phase is reduced. For this reason, it may be impossible to change the phase advance angle of the valve.

  The present invention has been made to solve the above-described problems, and provides a variable phase valve mechanism for an internal combustion engine that can reliably perform phase advance control even at low temperatures. With the goal.

In order to achieve the above object, the first invention can change the phase of the valve by moving the working oil between the advance chamber and the retard chamber using the torque fluctuation of the cam shaft of the internal combustion engine. A variable phase valve mechanism for an internal combustion engine,
The phase variable valve mechanism includes negative torque urging means capable of urging negative torque to the camshaft,
When the negative torque of the cam shaft is reduced, the negative torque of the cam shaft is compensated by the negative torque urging means ,
The negative torque biasing means is a spring member whose spring constant decreases as the temperature increases.
The phase variable valve mechanism further includes an attachment member for attaching the spring member,
The mounting member is displaced at a high temperature so as to reduce a negative torque compensated by the spring member as compared with a low temperature .

  A first aspect of the present invention is a variable phase valve mechanism for an internal combustion engine capable of changing the phase of a valve by moving hydraulic oil between an advance chamber and a retard chamber using torque fluctuation of a cam shaft of the internal combustion engine. About. According to the first aspect of the present invention, when the negative torque of the camshaft is reduced, such as when the temperature is low, the negative torque is biased against the camshaft by the negative torque biasing means. Therefore, since the negative torque used for the phase advance control can be ensured even at a low temperature, the phase advance control can be executed reliably.

According to the first aspect of the invention, the phase advance angle control at a low temperature can be surely executed. However, when negative torque is energized by the negative torque energizing means even at a high temperature, the phase advance angle control at a high temperature is used. May cause a reduction in the positive torque. Further, according to this invention, the smaller the spring constant of the spring member as a negative torque biasing means becomes hot. Therefore, the negative torque supplemented by the spring member at high temperatures is made smaller than at low temperatures. Thereby, the fall of the positive torque used for phase retardation control at the time of high temperature can be suppressed, and the fall of the responsiveness of the phase retardation control at the time of high temperature can further be suppressed.

Further, according to this invention, since the mounting member for mounting the spring member at a high temperature displacement, the negative torque is compensated by the spring member at a high temperature is smaller than the low temperature. Thus, it is possible to suppress a decrease in the positive torque used for the phase retardation control of the on-high temperature, it is possible to further suppress the decrease in the responsiveness of the phase retarding control at high temperatures.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram showing an example of a system configuration according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an in-line four-cylinder gasoline engine (spark ignition internal combustion engine) as the engine 1. The engine 1 may be a diesel engine (compression ignition internal combustion engine). The piston of each cylinder 2 of the engine 1 is connected to the crankshaft 3 via a crank mechanism. A crank angle sensor 4 that detects the crank angle CA is provided in the vicinity of the crankshaft 3.

  Each cylinder 2 of the engine 1 is provided with an injector 5 that directly injects fuel into the cylinder. Each injector 5 is connected to a common common rail 6. The common rail 6 stores fuel pressurized by the supply pump 7. The injector 5 can inject fuel into the cylinder at an arbitrary timing during one cycle. Each cylinder 2 of the engine 1 is provided with a spark plug 8 that ignites the air-fuel mixture in the cylinder 2.

  Each intake port 9 of the engine 1 is provided with two intake valves 10. That is, two intake valves 10 are provided for each cylinder. The intake valve 10 is connected to a variable phase valve mechanism 11. The phase variable valve mechanism 11 is configured to be able to change the phase of the intake valve 10. The intake port 9 is connected to an intake passage 13 via an intake manifold 12. A throttle valve 14 is provided in the middle of the intake passage 13. The throttle valve 14 is an electronically controlled valve that is driven by a throttle motor 14a. The throttle valve 14 is driven based on the accelerator opening AA detected by the accelerator opening sensor 16. A throttle opening sensor 15 that detects the throttle opening TA is provided in the vicinity of the throttle valve 14. An air flow meter 17 for detecting the intake air amount Ga is provided upstream of the throttle valve 14. An air cleaner 18 is provided upstream of the air flow meter 17.

  Each exhaust port 19 of the engine 1 is provided with two exhaust valves 20. That is, two exhaust valves 20 are provided for each cylinder. The exhaust valve 20 is connected to a phase variable valve mechanism 21. The phase variable valve mechanism 21 has the same configuration as the variable valve mechanism 11 of the intake system. The exhaust port 19 is connected to the exhaust passage 23 via the exhaust manifold 22. The exhaust passage 23 is provided with an exhaust purification catalyst 24 that purifies the exhaust gas. An air-fuel ratio sensor 25 that detects the exhaust air-fuel ratio is provided upstream of the catalyst 24.

  One end of an external EGR passage 26 is connected to the exhaust manifold 22. The other end of the external EGR passage 26 is connected to the intake passage 13 in the vicinity of the intake manifold 12. Through this external EGR passage 26, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 13, that is, external EGR (Exhaust Gas Recirculation) can be performed. Further, an EGR cooler 27 for cooling the external EGR gas is provided in the middle of the external EGR passage 26. An EGR valve 28 is provided downstream of the EGR cooler 27. As the opening degree of the EGR valve 28 is increased, the external EGR amount (or the external EGR rate) can be increased.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 30 as a control device. An injector 5, a supply pump 7, variable valve mechanisms 11 and 21, a throttle motor 14 a, an EGR valve 28, and the like are connected to the output side of the ECU 30. In addition to the crank angle sensor 4, the throttle opening sensor 15, the accelerator opening sensor 16, the air flow meter 17, and the air-fuel ratio sensor 25, a water temperature sensor 29 that detects the cooling water temperature of the engine 1 is connected to the input side of the ECU 30. Yes.

(Configuration of variable phase valve mechanism)
Next, with reference to FIGS. 2 and 3, the configuration of the variable phase valve mechanisms 11 and 21 mounted in the system will be described. FIG. 2 is a diagram showing the configuration of the phase variable valve mechanisms 11 and 21 mounted in the system shown in FIG. FIG. 3 is an enlarged view of the assist spring 35 shown in FIG.
As shown in FIG. 2, a sprocket 32 is provided around the cam shaft 31. A housing cover 33 is fixed to the sprocket 32. A spring retainer 34 is provided at the end of the cam shaft 31. An assist spring 35 is provided between the spring retainer 34 and the housing cover 33. The assist spring 35 biases the camshaft 31 with a negative torque at a low temperature (particularly at an extremely low temperature) when the friction of the camshaft 31 increases. The assist spring 35 is preferably a shape memory spring such as a torsion spring or a coil spring whose spring constant decreases as the temperature increases, and can be formed of, for example, a titanium-based material. As shown in FIG. 3, the assist spring 35 is wound around the same diameter portion of the spring retainer 34 a plurality of times, and its end is hooked on the fixing member 36. The assist spring 35 does not necessarily have to be wound with the same diameter, and may be wound a plurality of times with different diameters. For example, the fixing member 36 can be provided at another fixing position of the cam shaft 31 in addition to the spring retainer 34.

  A rotor 39 is connected in the housing 33. The rotor 39 has a vane 40 that engages with the housing 33 and partitions the advance chamber 41 and the retard chamber 42 (see FIGS. 4 and 5). Further, the rotor 39 accommodates check valves 43 and 44 that prevent backflow of the working oil, and a spool 45 that slides in the axial direction on the hollow portion at the end of the cam shaft 31. The spool 45 is formed with a recess 45a for communicating a plurality of oil passages. The spool 45 is driven by a variable solenoid 46. The variable solenoid 46 is connected to the output side of the ECU 30.

[Operation of variable phase valve mechanism]
Next, the operation of the variable phase valve mechanism will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram for explaining the operation of the phase variable valve mechanism at the time of phase advance control. FIG. 5 is a diagram for explaining the operation of the variable phase valve mechanism during phase retardation control.

(Phase advance control)
As indicated by an arrow A1 in FIG. 4, a negative camshaft torque acts on the vane 40, and the variable solenoid 46 is driven so that the oil passages 48 and 49 are in communication with each other by the recess 45a. Then, the working oil moves from the retard chamber 42 to the advance chamber 41. Specifically, the working oil in the retard chamber 42 flows in the order of the oil passage 49, the recess 45 a, and the oil passages 48 and 47 and flows into the advance chamber 41. Thereby, the phase of the camshaft 31 with respect to the crankshaft 3 is advanced, and the phase of the intake valve 10 and / or the exhaust valve 20 is advanced.
When a reverse camshaft torque is generated during the control, the check valve 43 prevents the backflow of the working oil.

(Phase retardation control)
When the variable solenoid 46 is driven so that the camshaft torque in the positive direction acts on the vane 40 and the position of the pool 45 where the oil passages 47 and 48 communicate with each other by the recess 45a, as indicated by an arrow A2 in FIG. Then, the working oil moves from the advance chamber 41 to the retard chamber 42. Specifically, the working oil in the advance chamber 41 flows in the order of the oil passage 47, the recess 45 a, and the oil passages 48 and 49 and flows into the retard chamber 42. Thereby, the phase of the camshaft 31 with respect to the crankshaft 3 is retarded, and the phase of the intake valve 10 and / or the exhaust valve 20 is retarded.
When a reverse camshaft torque is generated during control, the check valve 44 prevents backflow of the working oil.

  Further, the hydraulic oil that leaks from the gap between the housing 33 and the rotor 39 can be replenished via the oil passage 50 by driving the pump 51.

FIG. 6 is a diagram for explaining the phase advance angle control of the intake and exhaust valves 10 and 20 realized by the variable phase valve mechanism. Specifically, FIG. 6 (A) is a diagram for explaining phase advance angle control during cold start, and FIG. 6 (B) is a diagram for explaining phase advance angle control during low / medium speed WOT.
As shown by the solid line L1 in FIG. 6A, the actual compression ratio can be lowered and the fuel efficiency at light load can be improved by performing a so-called Atkinson cycle in which the intake and exhaust valves 10, 20 are closed slowly. It is known that it can be. When the engine 1 is stopped at this timing (for example, the closing timing of the intake valve 10 is 100 ° after the bottom dead center BDC) and then started at a low temperature (especially, an extremely low temperature of −35 ° C. or lower), the cylinder There is a possibility that the amount of intake air is insufficient and startability deteriorates.
Therefore, at the time of such low temperature start, the phase advance angle control by the phase variable valve mechanisms 11 and 21 described above is executed. Thereby, as shown by the broken line L2 in FIG. 6A, the phases of the intake and exhaust valves 10 and 20 can be advanced by, for example, 30 ° CA or more. As a result, the in-cylinder intake air amount can be increased, and the startability in the cold state can be improved.
Here, as shown in FIG. 7, the friction torque increases at a low temperature as compared with a high temperature. FIG. 7 is a diagram showing the friction torque that increases at a low temperature. The increase in the friction torque is due to an increase in the viscosity of the working oil and a reduction in the clearance between the cam shaft 31 and its bearings when cold as compared to when the temperature is high. Due to the increase of the friction torque, the negative torque of the camshaft necessary for the phase advance angle control is reduced. However, according to the phase variable valve mechanisms 11 and 21, a negative torque is applied to the camshaft 31 by the assist spring 35 at a low temperature. This makes it possible to reliably execute the phase advance angle control even at a low temperature.

  After the engine is started, at the time of low / medium speed WOT, a larger amount of intake air is required than at the time of starting. Therefore, as shown by a solid line L3 in FIG. 6B, the phases of the intake and exhaust valves 10, 20 can be further advanced as compared to the cold start shown by the broken line L2. For example, the intake valve 10 can be advanced 40 ° or less after bottom dead center BDC by advancing the angle by 30 ° CA or more.

As described above, the variable phase valve mechanisms 11 and 21 according to the first embodiment move the vane 40 using the torque fluctuation of the cam shaft 31 to transfer the working oil between the advance chamber 41 and the retard chamber 42. The phase of the intake and exhaust valves 10 and 20 is changed by moving between them. At low temperatures (particularly at low temperatures), the friction of the camshaft 31 increases, so the negative torque of the camshaft 31 decreases. Therefore, in the first embodiment, a negative torque is urged against the cam shaft 31 by the assist spring 35. Thereby, since the negative torque of the camshaft 31 is compensated by the assist spring 35 at a low temperature, the phase advance angle control can be surely executed even at a low temperature.
Furthermore, since the spring constant of the assist spring 35 becomes smaller as the temperature becomes higher, it is possible to suppress a decrease in the positive torque of the camshaft 31 at a high temperature. Therefore, it is possible to prevent the responsiveness of the phase retardation control at high temperatures from being lowered.

In the first embodiment, the engine 1 is the “engine” in the first invention, the camshaft 31 is the “camshaft” in the first invention, and the advance chamber 41 is the “advanced” in the first invention. In the corner chamber, the retard chamber 42 is the “retard chamber” in the first invention, the intake and exhaust valves 10 and 20 are the “valves” in the first invention, and the phase variable valve mechanisms 11 and 21 are the first. the "phase variable valve mechanism" in one of the invention, the assist spring 35 to the "negative torque biasing means"及beauty "spring member" in the first aspect of the present invention, corresponding respectively.

(Modification)
In the first embodiment, a mode has been described in which the negative torque of the camshaft, which decreases at low temperatures, is compensated by the spring. However, instead of this spring, the negative torque of the camshaft may remain at low temperatures by the following method. Good. That is, an increase in friction torque at a low temperature may be suppressed by a modification described below.

(First modification)
As the bearing of the cam shaft, a sliding bearing is usually adopted from the viewpoint of cost. In the first modification, a rolling bearing is employed instead of the sliding bearing. As a result, the coefficient of static friction of the camshaft at a low temperature can be reduced, so that an increase in camshaft friction at a low temperature can be suppressed.

(Second modification)
Usually, the camshaft is made of a ferrous material. On the other hand, the rolling bearing is made of an aluminum-based material. Aluminum-based materials have a larger linear thermal expansion coefficient than iron-based materials. For this reason, when the temperature is low, the clearance between the camshaft and the bearing is reduced as compared to when the temperature is high. Therefore, in the second modification, the cam cap is made of an iron-based material, and an aluminum sliding layer is provided on the surface thereof. As a result, an increase in camshaft friction at low temperatures can be suppressed.

(Third Modification)
As described above, when the temperature is low, the clearance between the cam shaft and the bearing is reduced. Therefore, in the third modification, the clearance between the cam shaft and the bearing is set so that the friction of the cam shaft does not increase at low temperatures. When the clearance is set as described above, a hitting sound may be generated due to an increase in the clearance at a high temperature. In the third modification, a vibration isolating member is disposed around the cam cap in order to suppress such hitting sound. As a result, an increase in camshaft friction at low temperatures can be suppressed.

  You may combine the 1st thru | or 3rd modification mentioned above with the said Embodiment 1. FIG. As will be described in Embodiment 2 described later, if the spring constant of the assist spring 35 is increased too much to compensate for the negative torque of the camshaft 31 that decreases at extremely low temperatures, the positive torque at high temperatures is reduced. there is a possibility. If it does so, the responsiveness of the retardation control at the time of high temperature will fall. By combining the modified examples, the spring constant of the assist spring 35 can be suppressed, so that it is possible to prevent the responsiveness of the retard control at a high temperature from being lowered.

  In this embodiment, an example of a direct injection engine that directly injects fuel into a cylinder is disclosed, but an internal combustion engine to which the present invention can be applied is not limited to this. That is, the present invention can also be applied to a port injection engine that injects fuel into an intake port. This also applies to other embodiments described below.

  In the present embodiment, the internal combustion engine includes a system for recirculating exhaust gas (EGR system). However, the internal combustion engine to which the present invention is applicable is not limited to this. That is, the present invention can also be applied to an internal combustion engine that does not recirculate exhaust gas. This also applies to other embodiments described below.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment, the camshaft 31 is biased with a negative torque by the assist spring 35 whose spring constant decreases as the temperature increases.
By the way, if the spring constant of the assist spring 35 is determined so as to bias a desired negative torque to the camshaft 31 at an extremely low temperature, the positive torque of the camshaft 31 at a high temperature may be reduced. If so, there is a possibility that the responsiveness of the phase retardation control at a high temperature is lowered. Under the load KL that causes knocking, the engine speed NE, and the temperature conditions, there is a need to rapidly retard the phase of the intake valve 10 to lower the compression end temperature.

  Therefore, in the second embodiment, as shown in FIG. 8, an attachment member 37 for attaching the assist spring 35 is provided. FIG. 8 is a diagram showing the attachment member 37 for the assist spring 35 in the second embodiment. The attachment member 37 is made of a resin having a large thermal expansion coefficient (for example, wax). For this reason, at high temperature, as shown in FIG. 8, it expands and displaces. As a result, the fixing position 36a of the assist spring 35 is shifted in the direction in which the negative torque compensated by the assist spring 36 is reduced. Therefore, it is possible to prevent a decrease in the positive torque of the camshaft 31 at a high temperature, and it is possible to prevent a decrease in response of phase retardation control at a high temperature.

  By the way, in the second embodiment, the mounting member 37 is displaced by thermal expansion at a high temperature so that the spring constant of the assist spring 35 at a high temperature is reduced. However, the mounting member 37 is moved and displaced. You may make it make it. That is, the position of the attachment member 37 may be controlled using hydraulic pressure or a motor.

In the second embodiment, the attachment member 37 corresponds to the “attachment member” in the first invention.

It is a figure which shows an example of a structure of the system by Embodiment 1 of this invention. It is a figure which shows the structure of the phase variable valve mechanisms 11 and 21 mounted in the system shown in FIG. It is an enlarged view of the assist spring 35 shown in FIG. It is a figure for demonstrating operation | movement of the phase variable valve mechanism at the time of phase advance control. It is a figure for demonstrating operation | movement of the phase variable valve mechanism at the time of phase retardation control. It is a figure for demonstrating the phase advance angle control of the intake and exhaust valves 10 and 20 implement | achieved by the phase variable valve mechanism. It is a figure which shows the friction torque which increases at the time of low temperature. In Embodiment 2, it is a figure which shows the attachment member 37 for the assist spring 35. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 10 Intake valve 11, 21 Variable phase valve mechanism 20 Exhaust valve 30 ECU
31 Cam shaft 35 Assist spring 37 Fixing member

Claims (1)

A variable phase valve mechanism for an internal combustion engine capable of changing the phase of a valve by moving hydraulic oil between an advance chamber and a retard chamber using torque fluctuation of a cam shaft of the internal combustion engine,
The phase variable valve mechanism includes negative torque urging means capable of urging negative torque to the camshaft,
When the negative torque of the cam shaft is reduced, the negative torque of the cam shaft is compensated by the negative torque urging means ,
The negative torque biasing means is a spring member whose spring constant decreases as the temperature increases.
The phase variable valve mechanism further includes an attachment member for attaching the spring member,
The variable phase valve mechanism for an internal combustion engine, wherein the mounting member is displaced at a high temperature so as to reduce a negative torque compensated by the spring member as compared with a low temperature .

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