JP2008157201A - Variable valve gear for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To feed hydraulic pressure which can resist camshaft drive torque in advancing valve opening timing of an exhaust valve toward a compression stroke top dead center. <P>SOLUTION: The device is provided with a phase variable mechanism 6 provided between a cam sprocket and a camshaft to vary the phase of the camshaft in accordance with a feed/exhaust state of working fluid pressurized, an auxiliary chamber type pump 10 comprising a first pressurization source 101 to pressurize engine lubricant, and a second pressurization source 102 to pressurize working fluid fed to the phase varying mechanism, an opening/closing valve 23 provided on a drain passage 22 to drain working fluid fed from the second pressurization source 102, and a control means 18 to control the opening/closing state of the opening/closing valve 23. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable valve operating apparatus for an engine, in which a valve timing can be changed by controlling a supply / discharge state of a working fluid.

2. Description of the Related Art Conventionally, as one of engine brake devices, an exhaust brake device in which an on-off valve provided in an exhaust passage is closed to increase exhaust pressure to increase engine brake capability has been widely put into practical use.
In addition to this, a third valve different from the intake / exhaust valve is provided when the accelerator is off, and the operation state of the third valve is controlled to control the pressure state in the cylinder so as to increase the engine braking capability. A compression-release engine auxiliary brake device (so-called power tard) has been developed and put into practical use.

There is also known a power tard that increases the engine braking ability by controlling the pressure state in the cylinder by opening and closing the exhaust valve at a timing different from the normal exhaust timing without providing the third valve.
Here, the operation principle of the compression pressure release type engine auxiliary brake device using the exhaust valve will be briefly described. When the brake device is operated, the fuel injection is stopped and the exhaust valve is driven to open and close as follows.

That is, during the intake stroke, the intake valve is opened as usual to take in the intake air. Next, during the compression stroke, both the intake valve and the exhaust valve are closed as in normal operation to compress the intake air in the cylinder. The compression force at this time acts as a force that hinders engine rotation.
Next, immediately before the transition from the compression stroke to the expansion stroke (that is, near the top dead center), the exhaust valve is opened, and the compressed intake air is discharged to the exhaust port. Then, an expansion stroke is performed with the exhaust valve open, and air is sucked from the exhaust valve side at this time.

Thereafter, the exhaust valve is closed from the expansion stroke to the exhaust stroke, and the exhaust stroke is executed with both the intake and exhaust valves closed. Therefore, similarly to the above-described compression stroke, the compression force acts on the piston and the rotation of the engine is hindered. After that, when the piston reaches the vicinity of the top dead center again, the intake valve is opened to release the compressed air, and the intake stroke is started again.
Then, the braking force in the compression stroke and the exhaust stroke continuously acts on the piston, so that the engine braking capability is greatly increased. In other words, the kinetic energy of the vehicle is absorbed and converted into braking force by causing the engine to perform pump operation as negative work. The force that is absorbed by the engine and acts as a braking force (engine braking force) is called absorption horsepower.

In the above description, the operation of the two-cycle type power tard in which one braking force is applied every crankshaft rotation (360 °) has been described. However, one braking force is applied every two crankshaft rotations (720 °). There is also known a four-cycle power tard in which
By the way, in addition to the compression pressure release type engine auxiliary brake device (power tard) as described above, a variable valve mechanism that changes the opening / closing timing and lift amount of the intake and exhaust valves for the purpose of improving engine performance or Various variable valve timing mechanisms (hereinafter referred to as VVT mechanisms) have been developed.

As an example of such a VVT mechanism, a camshaft is equipped with a plurality of cams having different valve opening / closing timings and valve lift amounts (that is, a plurality of cams having different cam profiles), and any one of these cams is provided. A mechanism is known in which the opening / closing timing of the intake / exhaust valve can be changed stepwise by selecting and using.
In recent years, besides the cam switching type VVT mechanism, the cam and camshaft phases with respect to the crankshaft are continuously changed to advance or retard the opening / closing timing of the intake and exhaust valves. The VVT mechanism is widely put into practical use.

As such a phase change type VVT mechanism, for example, as disclosed in Patent Document 1 below, a camshaft and a cam sprocket are coupled via a helical spline, and the end of the camshaft is connected to the cam sprocket. On the other hand, a technique is known in which the phase between the cam sprocket and the camshaft is changed by moving forward and backward.
In addition to this, a vane type VVT mechanism as disclosed in Patent Documents 2 and 3 is also widely known as a phase change type VVT mechanism. In this vane-type VVT mechanism, a housing having a plurality of wall surfaces extending in the radial direction is formed on the inner peripheral surface side of the cam sprocket, and a rotor having vanes is provided at the end of the camshaft. The rotor is housed in the housing so as to be positioned between them.

In addition, a hydraulic chamber is formed in a space defined by the vane and the wall surface of the housing, and the vane can move between the wall surfaces of the housing by controlling the supply and discharge state of the hydraulic oil to the hydraulic chamber. Within the range, the phase of the camshaft relative to the cam sprocket can be advanced or retarded, thereby changing the valve opening / closing timing.
Patent Documents 2 and 3 disclose techniques in which a compression pressure release type engine auxiliary brake device (power tard) is configured using such a vane type VVT mechanism. Specifically, when the driver's accelerator off is detected, fuel injection is stopped and the opening / closing timing of the exhaust valve is advanced by about 180 ° by the VVT mechanism. As a result, the exhaust valve is opened near the top dead center of the compression stroke, and the engine can be operated as a two-cycle power tard as described above.
JP 57-24431 A JP 2004-108217 A JP-A-1-92504

However, when the engine braking force is obtained by advancing the valve opening timing of the exhaust valve to the vicinity of the top dead center of the compression stroke by the vane type VVT mechanism, the conventional technique has the following problems.
That is, the cylinder internal pressure is very high near the top dead center of the compression stroke, and a very high camshaft driving torque is required to open the exhaust valve near the top dead center. In this case, in order to hold the camshaft in the advanced state, a supply hydraulic pressure capable of generating a torque higher than the camshaft driving torque by the VVT mechanism is required. There is a problem that the valve opening timing cannot be advanced to the top dead center of the compression stroke.

In order to solve such a problem, it is conceivable to simply increase the capacity of the oil pump, but in this case, the oil pump becomes larger and the driving horsepower of the oil pump increases, so that the fuel consumption deteriorates. There is.
The present invention has been devised in view of such problems, and minimizes deterioration of the fuel consumption of the engine when the valve opening timing of the exhaust valve is advanced to the vicinity of the top dead center of the compression stroke by the vane type VVT mechanism. It is an object of the present invention to provide a variable valve operating device for an engine that can supply hydraulic pressure that is not defeated by a camshaft driving torque with a simple system.

  For this reason, the variable valve operating apparatus for an engine according to the present invention includes a cam sprocket that is rotationally driven by the crankshaft of the engine, a camshaft that has a cam that opens and closes at least an exhaust valve of the engine, the cam sprocket, and the cam The phase of the camshaft relative to the cam sprocket is set between a phase corresponding to a normal operation state and a phase corresponding to an engine brake state according to the supply / discharge state of the pressurized working fluid interposed between the shaft and the shaft. A sub-chamber having a phase change mechanism that can be changed between, a first pressure source that pressurizes the lubricating oil of the engine, and a second pressure source that pressurizes the working fluid supplied to the phase change mechanism An on-off valve interposed on a drain passage for draining the working fluid supplied from the second pressurizing source, and a control means for controlling the on-off state of the on-off valve It is characterized in that it withered (claim 1).

  The control means opens the on / off valve fully below a predetermined vehicle speed, controls the on / off valve to a predetermined opening when the vehicle speed exceeds the predetermined vehicle speed, and then detects the engine brake request and opens the on / off valve. It is preferable to switch the supply state of the hydraulic oil to the phase change mechanism so that the phase of the camshaft becomes a phase corresponding to the engine brake state while being fully closed.

Further, the control means switches the supply state of the hydraulic oil to the phase change mechanism so that the phase of the camshaft becomes a phase corresponding to a normal operation state when the engine brake request is eliminated, and thereafter Preferably, the opening / closing valve is fully opened when the vehicle speed is lower than the predetermined vehicle speed, and the opening / closing valve is controlled to a predetermined opening degree when the vehicle speed is higher than the predetermined vehicle speed.
The phase corresponding to the engine brake state is such that the exhaust valve starts to open at the end of the compression stroke or the early stage of the expansion stroke, and corresponds to the engine brake state when the engine brake request is detected. It is preferable to advance the phase of the camshaft toward the adjusted phase.

  The first pressure source is preferably connected to the main gallery of the engine.

According to the variable valve operating apparatus of the present invention, it is possible to supply the hydraulic pressure that does not lose the camshaft driving torque without affecting normal lubrication to the phase changing mechanism. Further, it is possible to reduce the size and weight as compared with the case where one large-capacity pump is provided, and to improve the fuel consumption.
Further, since the opening / closing valve of the drain passage is fully opened at a speed lower than the predetermined vehicle speed, the drive loss of the pump can be suppressed as much as possible. In addition, when the vehicle speed exceeds a predetermined vehicle speed, the supply hydraulic pressure to the phase change mechanism can be increased in advance by opening the on-off valve by a predetermined opening, and the camshaft phase can be changed quickly when an engine brake is required. (Claim 2).

When the engine brake request is canceled, the camshaft phase is changed to a phase corresponding to the normal operating state, and then the opening / closing valve is set to an opening degree corresponding to the vehicle speed. It is possible to quickly shift to normal operation without inviting, and to prepare for the next engine brake request.
When the engine brake request is detected, the camshaft phase is advanced to change the phase so that the exhaust valve opens at the end of the compression stroke or at the beginning of the expansion stroke. The auxiliary device can be easily realized (claim 4).

  Further, since the first pressurizing source is connected to the main gallery of the engine, it does not affect normal lubrication (Claim 5).

  Hereinafter, a variable valve operating apparatus for an engine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are schematic views showing the configuration of essential parts, and FIG. 3 shows the operation of the engine to which the present invention is applied. FIG. 4 is a cam lift diagram for explaining the operation of the apparatus, FIG. 5 is a schematic block diagram showing the control system, and FIGS. 6 and 7 are flowcharts for explaining the operation.

  As shown in FIG. 3, the engine 1 is provided with a vane type variable valve mechanism (variable valve timing mechanism or VVT mechanism) 2 that can change the opening / closing timing of intake valves and exhaust valves (not shown). . The VVT mechanism 2 includes an exhaust side VVT mechanism (exhaust VVT) 2a for changing the valve timing of the exhaust valve and an intake side VVT mechanism (intake VVT) 2b for changing the valve timing of the intake valve. The operation of the VVT 2a and the intake VVT 2b can be controlled independently.

In the present embodiment, the VVT mechanism 2 is provided for both intake and exhaust. However, the VVT mechanism 2 may be provided at least on the exhaust side, and may not be provided on the intake side. Further, in the following, when the same member is distinguished between the intake side and the exhaust side, a and b are respectively added to the end of the reference numeral, and when the distinction between intake and exhaust is omitted, only the numerals are indicated.
In the present embodiment, when the engine brake is required, the fuel injection is stopped, and the VVT mechanism 2a is operated to change the operation timing of the exhaust valve. The engine brake force is obtained by operating as a so-called power tard.

  As shown in FIG. 3, the VVT mechanism 2 includes a cam sprocket 4 (4a, 4b) that is rotationally driven by the crankshaft 3 and a cam (not shown) that drives the intake and exhaust valves of the engine 1 to open and close. And a phase change mechanism 6 that can change the phase of the camshaft 5 relative to the cam sprocket 4 from a phase corresponding to a normal operation state to a phase corresponding to an engine brake state. (6a, 6b). The phase changing mechanism 6 is interposed between the cam sprocket 4 and the camshaft 5 and continuously advances the camshaft 5 according to the supply / discharge state of pressurized hydraulic oil (working fluid). It is configured so that it can be angled or retarded.

  Further, in this embodiment, when the phase of the camshaft 5 is the most retarded angle, the exhaust valve is set to have an operation timing suitable for normal operation of the engine 1, and from this state, the camshaft 5 Can be changed to the exhaust valve operation timing corresponding to the engine brake state by advancing the angle of about 90 ° at the maximum with respect to the cam sprocket 4 (about 180 ° in crankshaft angle).

As a result, as shown in FIG. 4, when the camshaft 5 is at the most advanced angle, the exhaust valve opens at the end of the compression stroke, and the exhaust valve closes at the beginning of the exhaust stroke. Can be changed to a phase corresponding to the engine brake state.
The opening timing of the exhaust valve at the maximum advance angle is not limited to the end of the compression stroke, and may be from the end of the compression stroke to the beginning of the expansion stroke. Similarly, the closing timing of the exhaust valve is not limited to the initial stage of the exhaust stroke, but may be from the end of the expansion stroke to the initial stage of the exhaust stroke.

  As shown in FIG. 3, the exhaust-side sprocket 4a and the intake-side sprocket 4b are connected to the crankshaft 3 of the engine 1 via a timing belt (or timing chain) 7, and the crankshaft 3 is The speed of the crankshaft 7 is reduced by half so that the cam sprocket 4 and the camshaft 5 make one rotation when they are rotated twice, and are transmitted to the cam sprocket 4. The timing belt 7 is given an appropriate tension by a tensioner 8.

  By changing the relative phase between the exhaust side sprocket 4a and the exhaust camshaft 5a and the relative phase between the intake side sprocket 4b and the intake camshaft 5b independently by the phase changing mechanism 6, the crankshaft 3 The opening / closing timing of the exhaust valve and the intake valve can be changed / adjusted with respect to the rotation phase of the valve. The phase changing mechanism 6 is provided with a lock mechanism (not shown) that holds the relative phase between the cam sprocket 4 and the camshaft 5 at the most retarded angle at the most retarded angle.

In addition, the phase change of the camshaft 5 in the traveling direction of the timing belt 7 is a phase change to the advance side, and the phase change in the direction opposite to the traveling direction of the timing belt 7 is the phase change to the retard side. .
In addition, the configuration of the phase changing mechanism 6 applied to the vane-type VVT mechanism 2 is already widely known. For example, the configuration is similar to that disclosed in Patent Documents 2 and 3 described above. Detailed description is omitted.

A hydraulic circuit 9 as shown in FIGS. 1 and 2 is connected to the phase changing mechanism 6, and a hydraulic pump 10 driven by the engine 1 is connected to the hydraulic circuit 9.
Here, the hydraulic pump 10 is a sub-chamber pump having two pressurizing sources 101 and 102, and one of the sub-chamber pumps 10 (first pressurizing source) 101 is the engine 1. The other pressurization source (second pressurization source) 102 is connected to the phase change mechanism 6 via the hydraulic oil supply passage 11.

The first pressure source 101 and the second pressure source 102 are connected to a common oil tank (not shown), and the second pressure source 102 applies the lubricating oil stored in the oil tank. The pressure is supplied to the phase changing mechanism 6. That is, the lubricating oil of the engine 1 is used as the hydraulic oil for the phase change mechanism 6.
Further, the sub-chamber pump 10 is a gear-type pump as illustrated in the present embodiment. That is, the pump 10 has one drive gear 13 and two driven gears 14 and 15, and here, the central gear is configured as the drive gear 13 driven by the engine 1. Any one of the three gears shown in the figure may be a drive gear, and the drive gear 13 is not particularly limited to the central gear. Moreover, the pump applied to this invention should just have two pressurization sources, and is not limited to a gear type pump.

  The phase change mechanism 6 is provided with an oil control valve (OCV) 16 for switching its operating state. Further, an advance oil path 61, a retard oil path 62, and a discharge oil path 63 of the phase change mechanism 6 are connected to the output side (downstream) port of the OCV 16, and the OCV 16 input side (upstream) A drain passage 17 communicating with the hydraulic oil supply passage 11 and the oil tank is connected to the side port.

  The OCV 16 is a hydraulic or electromagnetic spool valve that switches the connection state of each passage based on a control signal from a controller (ECU) 18 serving as a control means described later. When the exhaust valve is advanced, The hydraulic oil supply passage 11 and the advance oil passage 61 are connected, and the drain passage 17 and the discharge oil passage 63 are connected. As a result, high-pressure hydraulic oil is supplied to the advance oil passage 61, and the phase of the camshaft 5 with respect to the cam sprocket 4 is changed to the advance side.

Further, by connecting the hydraulic oil supply passage 11 and the retard oil passage 62, the high-pressure hydraulic oil is supplied to the retard oil passage 62, and the phase of the camshaft 5 with respect to the cam sprocket 4 is changed to the retard side. It has become so.
Incidentally, the hydraulic oil supply passage 11 is provided with a pressure regulating valve 19 and an oil filter 20 in order from the upstream side, and a check valve 21 is provided in parallel with the oil filter 20. Then, impurities in the hydraulic oil supplied from the pump 10 are removed by the oil filter 20, and when the pressure in the oil filter 20 becomes higher than the set pressure of the check valve 21 due to accumulation of the impurities, this check The valve 21 is opened to bypass the hydraulic oil.

The pressure regulating valve 19 is a valve whose set pressure is set to be relatively high. When the pressure in the hydraulic oil supply passage 11 is excessively increased for some reason, the pressure regulating valve 19 is opened to discharge the hydraulic oil. The phase change mechanism 6 and the hydraulic circuit 9 are protected.
Further, on the downstream side of the oil filter 20, a drain passage 22 is branched from the hydraulic oil supply passage 11, and excess hydraulic oil in the hydraulic oil supply passage 11 is returned to the oil tank via the drain passage 22. It has come to be.

  Further, a relief valve (open / close valve) 23 whose opening degree is changed based on an operation signal from the controller 18 is provided on the drain passage 22. Here, the relief valve 23 is an on / off type electromagnetic valve that takes either a fully open state or a fully closed state, and the opening degree of the drain passage 22 is reduced to 0 by controlling the duty of the electromagnetic valve. It can be freely controlled between ˜100%. In addition, as a relief valve, you may use the valve of an opening degree adjustment type which can set an opening degree linearly besides what was mentioned above.

Further, the first pressurizing source 101 of the sub chamber type pump 10 is connected to the main gallery 12 through an oil passage 31, and a pressure regulating valve 32, an oil filter 33, a check valve 34, An oil cooler 35 is interposed. The configuration downstream of the first pressure source 101 is the same as that of a general engine lubrication structure, and thus the description thereof is omitted.
By the way, as described above, the VVT mechanism 2 on the exhaust side advances the phase of the camshaft 5 with respect to the cam sprocket 4 to a phase corresponding to the engine brake. Specifically, when the accelerator off of the driver is detected. The opening and closing timing of the exhaust valve is advanced by about 180 ° by the VVT mechanism 2, and the exhaust valve is opened near the top dead center of the compression stroke.

However, since the cylinder internal pressure is very high near the compression stroke top dead center, a very large camshaft drive torque is required to drive the exhaust valve to open near the compression stroke top dead center. Therefore, when a sufficiently high hydraulic pressure cannot be supplied to the phase change mechanism 6, the valve opening timing of the exhaust valve cannot be advanced to the top dead center of the compression stroke.
For such a problem, it is conceivable to simply increase the capacity of the oil pump, but when configured in this way, the oil pump becomes larger and the driving horsepower of the oil pump increases. The fuel consumption will deteriorate. Further, since the exhaust brake is not always used, it is not efficient to pressurize the hydraulic oil with a large oil pump at all times in order to obtain such a temporarily required hydraulic pressure.

Therefore, in this apparatus, the sub chamber type pump as described above is used, and the relief valve 23 of the drain passage 12 branched from the hydraulic oil supply passage 111 is duty-controlled to reduce the drive loss of the pump 10 as much as possible. The opening timing of the exhaust valve is advanced.
That is, the second pressurizing source 102 of the sub-chamber pump 10 is configured to be able to generate a hydraulic pressure sufficiently higher than the camshaft driving torque necessary for opening the exhaust valve near the top dead center of the compression stroke. Thus, the opening / closing timing of the exhaust valve can be surely advanced to the vicinity of the top dead center of the compression stroke. Further, when the engine brake is not necessary, the relief valve 23 is fully opened to avoid the drive loss of the pump 10 as much as possible.

  Hereinafter, the configuration and operation of the control system of the present apparatus will be described with reference to FIG. 5. A vehicle on which the engine 1 is mounted has a vehicle speed sensor (vehicle speed detection means) 40 for detecting the speed of the vehicle and an accelerator on / off. The idle switch 41 for detecting the cam and the cam sensors 42 for detecting the phase of the camshaft 6 are provided, and these sensors 40 to 42 are all connected to the input side of the ECU 18.

Here, the idle switch 41 is a means for detecting the presence or absence of an engine brake request. When the accelerator pedal opening is fully closed, the idle switch 41 is turned on and it is determined that an engine brake request has been made. Yes.
Further, the OCV 16 and the relief valve 23 are connected to the output side of the ECU 18, and control signals for the OCV 16 and the relief valve 23 are set based on information from the sensors 40 to 42.

  Specifically, while the accelerator switch 41 detects that the accelerator is on (the idle switch 41 is off), the vehicle travels normally. In this case, as shown in FIG. A control signal for the OCV 16 is set so as to connect the retard oil path 62 to the retard angle oil path 62. Thereby, the exhaust valve is set to the most retarded angle, and the phase of the exhaust valve is set to a phase suitable for normal operation of a normal engine. Further, even when the relief valve 23 is fully open, the oil pressure necessary for maintaining the most retarded state during normal operation can be supplied to the phase changing mechanism 6a via the OCV 16 so that the relief valve 23 can be supplied. The size is set.

Further, when the idle switch 41 is off, the opening / closing control for the relief valve 23 is performed based on the vehicle speed obtained by the vehicle speed sensor 40. Specifically, when the detected vehicle speed is less than a predetermined vehicle speed V ₀ set in advance, the ECU 18 sets a control signal for the relief valve 23 so that the relief valve 23 is fully opened. .
Thus, when the vehicle speed is lower than the predetermined vehicle speed V ₀ , the hydraulic oil supplied from the second pressurizing source 102 of the pump 10 is returned to the oil tank through the drain passage 22. The hydraulic oil supply passage 11 and the drain passage 22 have a sufficiently large cross-sectional area so that the passage itself does not become a resistance. By opening the relief valve 23 fully, the second pressure source The drive loss at 102 can be minimized, and the deterioration of fuel consumption can be suppressed.

In addition, when the vehicle speed becomes equal to or higher than the predetermined vehicle speed V ₀ , the relief valve 23 is opened to a predetermined opening (in this embodiment, 50%
). Thereby, the hydraulic pressure in the hydraulic oil supply passage 11 is increased to a pressure corresponding to the opening degree of the relief valve 23, and the engine brake is ready. Note that the predetermined vehicle speed V ₀ described above is a speed that is equal to or higher than a medium speed range that requires an engine braking force immediately when the accelerator is off, and is set to 50 km / h in the present embodiment, for example.

  When the idle switch 41 is turned on, it is determined that there is a request for engine braking, the relief valve 23 is fully closed, and the OCV 16 is switched to connect the hydraulic oil supply passage 11 and the advance oil passage 61. . As a result, the hydraulic pressure of the hydraulic oil supply passage 11 is sufficiently increased, the phase of the exhaust valve can be advanced by approximately 180 °, and the engine braking force can be reliably obtained. At this time, fuel injection is prohibited.

In this way, when the vehicle speed becomes equal to or higher than the predetermined vehicle speed V ₀ , the relief valve 23 is set to a predetermined opening that is not fully opened in advance and is prepared for when the accelerator is off. The hydraulic pressure can be increased.
Further, as described above, the second pressurizing source 102 can generate a hydraulic pressure sufficiently higher than the camshaft driving torque when the exhaust valve is driven to open in the vicinity of the compression stroke top dead center. The phase of the exhaust valve can be rapidly advanced.

Note that the on the idle switch 14 is less than the predetermined vehicle speed V ₀ is detected, since the relief valve 23 is fully opened → fully closed than when more than a predetermined vehicle speed V ₀ (the relief valve 50% closed → fully closed) The response is slightly delayed, but in this case, the vehicle speed is originally low, so there is almost no effect.
On the other hand, when the idle switch 41 is turned off (the accelerator pedal is depressed), the ECU 18 determines that the engine brake is to be released, switches the operating state of the OCV 16 to release the engine brake, and retards the hydraulic oil supply passage 11 and the retarded angle. The oil passage 62 is connected. As a result, the phase of the exhaust valve can be changed to the most retarded position and can be switched to the normal operation state.

When it is determined that the advance amount of the cam shaft is equal to or less than the predetermined angle θ ₀ based on the information of the cam angle sensor 42, the relief valve 32 is opened.
Note that when retarding the phase of the exhaust valve, the camshaft 5a can be retarded from the relationship with the cam sprocket 4a relative to the cam sprocket 4a as shown in FIG. 3 without supplying high-pressure hydraulic fluid. Although the angle can be returned to the angle, the phase of the exhaust camshaft 5a must be retarded as soon as possible when there is no engine brake request. If the delay in the opening / closing timing of the exhaust valve is delayed, after the vehicle stops Acceleration failure occurs when the engine is stalled when the clutch is disengaged or when shifting to reacceleration with the clutch engaged.

For this reason, when the engine brake request is released, by switching only the OCV 16 while keeping the relief valve 23 fully closed, high-pressure hydraulic oil can be quickly supplied to the phase changing mechanism 6a, and the phase of the camshaft 5a can be quickly adjusted. Can be retarded.
Thereafter the advancing amount of the cam shaft 5 at the time of release of the engine braking at a predetermined angle theta ₀ or less, the relief valve 23 is fully opened is less than the predetermined vehicle speed V _0, the relief valve if the predetermined vehicle speed greater than or equal _to V ₀ 23 Is set to a predetermined opening (50%) to meet the next engine brake request. Even in the accelerator-off state where the engine brake is on, immediately before the vehicle stops or when the clutch is disengaged, the phase of the camshaft 5a is quickly retarded so as not to cause an engine stall. It is like that.

Since the variable valve operating apparatus for an engine according to an embodiment of the present invention is configured as described above, its operation will be described below with reference to the flowcharts of FIGS.
First, the operation when the engine brake is operated will be described with reference to FIG. 6. In step S1, it is determined whether the accelerator is on or off. If the accelerator is off, it is determined that there is an engine brake request, and the process proceeds to step S5 and subsequent steps. Further, if the accelerator-on, the process proceeds to step S2, it compares the current vehicle speed and a predetermined vehicle speed V _0. Then, the vehicle speed in step S2 unless the predetermined vehicle speed greater than or equal _to V _0, then the process proceeds to step S4.

If the current vehicle speed is greater than or equal to the predetermined vehicle speed V ₀ in step S2, then the process proceeds to step S3, the opening of the relief valve 23 is set to a predetermined opening (50%), and then the process proceeds to step S4.
Then, in step S4, it is determined again whether the accelerator is on or off. If it is determined that the accelerator is off, it is determined that there is an engine brake request, and the process proceeds to step S5. In step S5, the relief valve 23 is fully closed, and then in step S6, the OCV 16 is switched to advance the phases of the exhaust camshaft 5a and the exhaust valve. If the accelerator is off in step S4, the process returns as it is and the flow after step S1 is repeated.

  Further, after the engine brake is operated, the subroutine of FIG. 7 is started, and it is determined whether the accelerator is on or off in step S11. If the accelerator is off, the routine returns and the engine brake operation continues. On the other hand, when the accelerator is turned on, it is determined that the engine brake is to be released, and the OCV 16 is switched in step S12 to retard the phases of the exhaust camshaft 5a and the exhaust valve.

Next, in step S13, based on the information from the cam angle sensor 42, it is determined whether or not the advance amount of the cam shaft 5a has become equal to or less than a predetermined advance amount θ _0, and the advance amount of the cam shaft 5a is increased by a predetermined amount. greater than the angular amount theta ₀ until a predetermined advancing amount theta ₀ or less, and repeats the determination in step S13.
On the other hand, when the camshaft advance amount is determined to a predetermined advancing amount theta ₀ or less at step S13, the process proceeds to step S14, reduced drive loss of the pump 10 by opening the relief valve 23. Thereafter, the process proceeds to the flowchart of FIG. 6, so that the opening degree of the relief valve 23 is an opening degree corresponding to the vehicle speed.

  As described above, according to the present apparatus, the engine brake (power tard) is operated using the VVT mechanism 2, and the pump 10 is configured as a sub-chamber type pump having two pressurization sources, and one pressurization source By using the (second pressurizing source) 102 exclusively for the VVT mechanism 2, it is possible to supply hydraulic oil to the VVT mechanism 2 without affecting normal lubrication. Further, it is possible to reduce the size and weight as compared with the case where one large-capacity pump is provided, and it is possible to improve fuel consumption.

Further, since the dedicated hydraulic pressure supply passage 11 is provided between the second pressurizing source 102 and the exhaust-side VVT 2a, for example, the operating oil flows smoothly even in a state where the operating oil is highly viscous at a low temperature, and the engine brake The opening / closing timing of the exhaust valve can be surely advanced when required.
Further, since the relief valve 23 of the drain passage 22 is fully opened when the vehicle speed is lower than the predetermined vehicle speed V ₀ , the drive loss of the pump can be suppressed as much as possible. In addition, when the vehicle speed exceeds the predetermined vehicle speed V ₀ , the relief valve 23 is opened by a predetermined opening, so that the hydraulic pressure in the hydraulic pressure supply passage 11 can be increased in advance, and the phase of the exhaust valve can be changed promptly when an engine brake is required. can do.

  When the engine brake request is canceled, the OCV 16 is switched so that the phase of the camshaft 5 becomes a phase corresponding to a normal driving state, and then the relief valve 23 is set to an opening degree corresponding to the vehicle speed. Therefore, it is possible to promptly shift to normal operation without incurring acceleration failure or engine stall. Further, by setting the opening of the relief valve 23 to an opening corresponding to the vehicle speed, it is possible to prepare for the next engine brake request.

Moreover, since the 1st pressurization source 101 of the pump 10 is connected to the main gallery 12 of the engine 1, there exists an advantage that there is no influence on normal lubrication.
The present invention is not limited to such an embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in this embodiment, during normal running, is less than a predetermined vehicle speed V ₀ to the relief valve 23 is fully closed, but the relief valve 23 becomes the predetermined vehicle speed greater than or equal _to V ₀ is set to a predetermined opening degree, the rotation of the engine The opening control of the relief valve may be executed using the number as a parameter. This is because the hydraulic pressure of the hydraulic oil discharged from the pump 10 depends on the engine speed. In addition to this, the opening degree of the relief valve may be linearly controlled based on any of the parameters of vehicle speed, hydraulic oil pressure, or engine speed.

  Further, in the present embodiment, the variable valve mechanism is controlled by determining whether or not to operate the engine brake only by the accelerator on / off determination by the idle switch 41. However, if the engine brake request can be detected, Instead of the switch 41, another sensor may be applied. For example, an accelerator opening sensor or a brake switch may be used, or an engine brake switch that is turned on / off by a driver's operation may be used.

  For example, when the engine brake switch is combined, the engine brake request by the idle switch 41 may be allowed only when the engine brake is turned on by the engine brake switch. With this configuration, the engine brake can be deactivated by turning off the engine brake switch when the engine brake is not required, such as when coasting, and the engine brake can be deactivated when the engine brake is required. The driver can select the operation mode of the engine brake, such as the engine brake can be operated by turning on the switch.

1 is a schematic diagram showing a configuration of a main part of a variable valve operating apparatus for an engine according to an embodiment of the present invention, showing a state at a most advanced angle (when an engine brake is activated). FIG. 1 is a schematic diagram showing a configuration of a main part of a variable valve operating apparatus for an engine according to an embodiment of the present invention, showing a state at the most retarded angle (during normal operation). It is a figure shown about the valve operating system of the engine to which the variable valve operating apparatus of the engine which concerns on one Embodiment of this invention is applied. It is a cam lift diagram explaining the effect | action of the variable valve operating apparatus of the engine which concerns on one Embodiment of this invention. It is a typical block diagram shown about the principal part structure of the variable valve operating apparatus of the engine which concerns on one Embodiment of this invention. It is a flowchart explaining the effect | action of the variable valve operating apparatus of the engine which concerns on one Embodiment of this invention. It is a flowchart explaining the effect | action of the variable valve operating apparatus of the engine which concerns on one Embodiment of this invention.

Explanation of symbols

1 Engine 2 VVT mechanism (Vane variable valve mechanism)
DESCRIPTION OF SYMBOLS 3 Crankshaft 4 Cam sprocket 5 Camshaft 6 Phase change mechanism 10 Sub chamber type pump 101 1st pressurization source 102 2nd pressurization source 18 ECU (control means)
22 Drain passage 23 Relief valve (open / close valve)

Claims (5)

A cam sprocket that is rotationally driven by the crankshaft of the engine;
A camshaft having a cam for opening and closing at least an exhaust valve of the engine;
The phase of the camshaft with respect to the cam sprocket corresponding to the normal operating state and the engine brake state according to the supply / discharge state of the pressurized working fluid interposed between the cam sprocket and the camshaft A phase change mechanism that can change between the phase corresponding to
A sub-chamber pump having a first pressurizing source for pressurizing the engine lubricating oil and a second pressurizing source for pressurizing the working fluid supplied to the phase change mechanism;
An on-off valve interposed on a drain passage for draining the working fluid supplied from the second pressurizing source;
A variable valve operating apparatus for an engine, comprising control means for controlling an open / closed state of the open / close valve. The control means includes
When the vehicle speed is lower than the predetermined speed, the on-off valve is fully opened.
When the vehicle speed exceeds the predetermined vehicle speed, the opening / closing valve is controlled to a predetermined opening degree. After that, when the engine brake request is detected, the opening / closing valve is fully closed and the phase of the camshaft corresponds to the engine brake state. 2. The variable valve operating apparatus for an engine according to claim 1, wherein the supply state of hydraulic oil to the phase changing mechanism is switched so as to be in phase. The control means includes
When the engine brake request disappears, the hydraulic oil supply state is switched to the phase change mechanism so that the phase of the camshaft becomes a phase corresponding to a normal driving state. 3. The variable valve operating apparatus for an engine according to claim 2, wherein the on-off valve is fully opened, and the on-off valve is controlled to a predetermined opening degree when the speed is equal to or higher than the predetermined vehicle speed. The phase corresponding to the engine brake state is
When the exhaust valve starts to open at the end of the compression stroke or early in the expansion stroke and the engine brake request is detected, the phase of the camshaft is advanced toward the phase corresponding to the engine brake state. The variable valve operating apparatus for an engine according to claim 2, wherein the valve is angled. The variable valve operating apparatus for an engine according to any one of claims 1 to 4, wherein the first pressurizing source is connected to a main gallery of the engine.

Images