JPH0519508U - Variable valve operating system of engine - Google Patents

Abstract

(57) [Abstract] [Purpose] After engaging two types of rocker arms with high hydraulic pressure, lower the hydraulic pressure to the lowest hydraulic pressure at which the engaged state is maintained to facilitate disengagement. A cam switching mechanism 82 switches from one cam to another cam having different characteristics by engaging two types of rocker arms when the hydraulic switching valve 84 is opened and hydraulic oil is supplied.
When the opening / closing valve 87 is opened by the control means 89 immediately after this engagement, the hydraulic oil in the hydraulic passage 83 is released to the return passage 86, and the hydraulic pressure is reduced to the minimum hydraulic pressure that can maintain the engaged state of the rocker arm. After that, when the operating condition changes and there is a request to switch to the 1st cam, the hydraulic switching valve 84 is closed by the control means 85. At this time, since the hydraulic pressure in the hydraulic passage 83 is the lowest hydraulic pressure that can maintain the engaged state, the engaged state is released with good response.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a variable valve operating system for an engine, and more particularly to a system capable of selectively switching a plurality of cams having different characteristics.

[0002]

[Prior Art]

 As disclosed in Japanese Patent Application Laid-Open No. 63-167016, a plurality of cams having different cam characteristics (cam profiles) are provided, and the cams are switched according to the operating conditions, so that each valve operates at the optimum valve timing. A variable valve operating device that enables the operation has been proposed.

Explaining this with reference to FIGS. 10 to 12, the cams 6 and 7 for the low rotation range and the cam 8 for the high rotation range are provided on the same cam shaft 5, and two types of cams 6 for one cylinder are provided. 8 drives two types of rocker arms 2-4.

Two intake valves (or exhaust valves) 9 and 10 are driven by one of the rocker arms 2 and 3 located on both sides. The other rocker arm 4 located in the center does not have an arm for opening and closing the intake valve, and a lost motion spring 11 for pressing the rocker arm 4 against the high speed cam 8 is provided from below in the figure.

The switching of the valve timing and the lift amount is performed depending on whether two types of rocker arms, that is, the rocker arms 2 and 3 on both sides and the rocker arm 4 at the center are engaged.

When the hydraulic pressure is supplied to the hydraulic piston 12 in the high rotation range, the two pistons 12 and 13 are both pushed out in the direction in which the return spring 15 is compressed (right in FIG. 11), and as shown in FIG. The side and central rocker arms are engaged. In this state, both the valve operating angle and the lift amount are governed by the movement of the high speed cam.

When the engine speed is low, the hydraulic pressure applied to the hydraulic piston 12 is cut off. As a result, the hydraulic pistons 12 and 13 are pushed back to the left by the return spring 15 as shown in FIG. At this time, the dimensions of the hydraulic pistons 12 and 13 are set to a length that makes the relationship between the two types of rocker arms free. Therefore, the engagement between both sides and the rocker arm in the center is released, and the valve timing and lift amount follow the low speed cam.

[0008]

[Problems to be solved by the device]

 By the way, since the two types of cams with different characteristics are set according to the low speed range and the high speed range respectively, the operating condition changes rapidly from the low speed range to the high speed range or vice versa. Even when doing so, it is required that the vehicle be operated in a cam according to each driving range immediately after moving to each driving range. In other words, in the transition, the two types of rocker arms are engaged, so the hydraulic piston must be pushed out with good response, and the hydraulic piston must be pushed back with good response to release the engagement.

In this case, it is the supply hydraulic pressure that determines the pushing speed of the hydraulic piston, and when a high hydraulic pressure is supplied, the force that overcomes the return spring becomes strong and the two types of rocker arms can be engaged with good response. it can.

However, when the supply of the hydraulic oil is stopped, the piston is pushed back from the time when the force of the return spring is generated as the force for pushing the hydraulic piston due to the decreasing hydraulic pressure. The higher the hydraulic pressure, the more the delay in releasing the engagement.

If it takes time to release the engagement, the cam switching timing varies among the cylinders.

Therefore, an object of the present invention is to make it easy to release the engagement by engaging the rocker arm with a high hydraulic pressure and then lowering it to the lowest hydraulic pressure at which the engagement state is maintained. ..

[0013]

[Means for Solving the Problems]

 As shown in FIG. 1, this device has a plurality of cams 81 having cam profiles with different output characteristics, and two types of rocker arms that engage with each other when hydraulic pressure is supplied, so that one cam moves to another cam. If the hydraulic pressure is not supplied, the rocker arm is disengaged and the cam is switched to the opposite. At the same time, the cam switching mechanism 82 that transmits the motion of the cam to at least one of the intake and exhaust valves and the cam switching mechanism 82 A valve 84 provided in the hydraulic passage 83 for switching the supply and release of the hydraulic oil, and the hydraulic oil is supplied when the switching from one cam to another cam is judged from the operating condition. Further, in a variable valve operating system for an engine, which comprises means 85 for controlling the opening / closing of the hydraulic pressure switching valve 84 so that the hydraulic oil is released when the cam switching to the opposite is judged, the hydraulic pressure downstream of the hydraulic switching valve A return passage 86 that branches from the passage 83 and returns to the oil tank, an opening / closing valve 87 that opens and closes the return passage 86, and a hydraulic pressure of the working oil supplied to the hydraulic passage 83 is a minimum value that can maintain the engagement state of the rocker arm. When the hydraulic pressure switching valve 84 is opened, the orifice 88 for restricting the return flow rate so as to reduce the hydraulic pressure to the hydraulic pressure and the operation of the hydraulic pressure switching valve 84 are opened after a certain time, and then the hydraulic pressure switching valve 84 is opened. A means 89 for controlling the opening / closing valve 87 is provided so that the opening / closing valve 87 is held open even when the valve is closed.

[0014]

[Action]

 When the hydraulic switching valve 84 is opened to activate the other cam among the plurality of cams, the high-pressure hydraulic oil from the oil pump is supplied to the cam switching mechanism 82, and the two types of rocker arms engage with each other to make one cam. To another cam.

When the opening / closing valve 87 is opened immediately after this engagement, the hydraulic oil in the hydraulic passage 83 is released to the return passage 86, and the hydraulic pressure is reduced to the minimum hydraulic pressure that can maintain the engaged state of the rocker arm.

After that, when the operating condition changes and there is a request for switching to the cam 1, the hydraulic switching valve 84 is closed.

At this time, the hydraulic passage 83 has the lowest hydraulic pressure that can maintain the engaged state, so that the engaged state can be released with good response.

In the other cylinder engine, if it takes time to release the engagement, the cam switching timing varies among the cylinders. However, if the engagement release time becomes short, the cam switching becomes uniform and the cam switching does not occur. It is done continuously.

[0019]

【Example】

 First, FIGS. 2 and 3 show a specific configuration of the variable valve operating device of the embodiment, which has already been proposed by the present applicant as Japanese Patent Application No. 2-117261.

Reference numeral 21 is a fuel profile-oriented cam profile, the first cam (fuel consumption cam) has a small cam lift and a small lift section, and 22 is a cam profile that produces high torque in a low rotation range. The second cam (low speed type output cam), 23, which has a relatively larger cam lift than the first cam 21, is set to a cam profile that generates high torque in a high rotation range. Larger third cam (high speed type output cam), which are installed in parallel on the same camshaft.

Reference numeral 24 is an intake / exhaust valve (intake valve or exhaust valve), 25 is a main rocker arm that is in constant contact with the first cam 21 via a roller 26, and rocks around a rocker shaft 27 as a fulcrum. Open and close the intake / exhaust valve 24.

On the main rocker arm 25, two sub rocker arms 28 and 29 swinging around a shaft 30 as a fulcrum are supported in parallel with the roller 26, and one sub rocker arm 28 is connected to the second cam 22. The other sub-rocker arm 29 contacts the third cam 23.

When the sub rocker arms 28 and 29 are not engaged with the main rocker arm 25, they are constantly urged by the lost motion spring 31 to come into contact with the second and third cams 22 and 23, and the main rocker arms It moves (swings) independently of the arm 25.

In order to selectively engage the sub rocker arms 28 and 29 with the main rocker arm 25, first, a columnar pin 32 is provided at the swinging portion of the one sub rocker arm 28, and then the main rocker arm 28. A pin 34 is provided on the arm 25 coaxially with the pin 32 so as to be slidable in the camshaft direction, and the pins 32 and 34 are normally urged by a return spring 36 to be in the state of FIG. It is held and disengaged from the main rocker arm 25, but when pressure oil is introduced through the passage 40 to the hydraulic chamber 38 in which the pin 34 is housed, the pins 32 and 34 are moved by a predetermined amount. When pushed out, the sub rocker arm 28 engages with the main rocker arm 25.

The sub rocker arm 28 and the main rocker arm 25 are integrated with each other when the first cam 21 and the second cam 22 are in the base circle. After the integration, the second rocker arm 28 has a larger lift than the first cam 21. The valve timing is changed according to the cam 22.

That is, the characteristic of the first cam 21 that emphasizes fuel consumption is switched to the characteristic of the second cam 22 that emphasizes output in the low rotation range.

The other sub-rocker arm 29 is also configured similarly to this, and when pressure oil is introduced into the hydraulic chamber 39 through the passage 41, the pins 35 and 33 are pushed out against the return spring 37. By engaging the sub rocker arm 29 with the main rocker arm 25, the valve timing is switched so as to depend on the third cam 23, which has a larger lift amount and lift section than the first cam 21 as described above. It is possible to obtain output-oriented characteristics in the high rotation range.

FIG. 4 shows the valve lift characteristics from the first cam 21 to the third cam 23. The full-open output characteristics when each cam is used are as shown in Fig. 5. With the first cam, the generated torque is low but the fuel consumption is good, and with the second cam, the maximum torque in the low rotation range is Although the torque generated by the third cam 23 is the highest and the generated torque in the low rotation range is smaller than that of the second cam 22, the maximum torque in the high rotation range is the highest.

By the way, in order to control switching from the first cam 21 to the second and third cams 22 and 23 and vice versa, switching from the second and third cams 22 and 23 to the first cam 21 is illustrated. A control unit 51 as shown in 6 is provided, and the optimum cam is selected according to the operating condition.

The selection of this cam in the control unit 51 is based on the characteristics of FIG. 5, and when the required torque and rotational speed are within the range of the first cam 21, which is a fuel consumption cam, for example, this fuel consumption cam is used and this state is set. When the accelerator opening increases and the required torque deviates from the fuel consumption cam area to the area of the second cam 22 which is, for example, the low speed type output cam, the fuel consumption cam is switched to the low speed type output cam, and the rotation is changed. When the number rises from the low speed range to the high speed range, it is switched to the third cam 23 which is a high speed type output cam.

Therefore, the control unit 51 includes a crank angle sensor 52 for detecting the engine speed and a crank angle position, an accelerator operation amount sensor 53 for detecting an operation amount (depression amount) of an accelerator pedal, and an oil temperature sensor 54. When a signal is input and the switching of the cam is determined based on these signals, a solenoid valve (hydraulic switching valve) 45 for switching between supplying and releasing hydraulic oil to the two hydraulic chambers 38, 39 is selected. And control the actions of 46.

In other words, when one solenoid valve 45 is opened, pressure oil from the oil pump is introduced into the hydraulic chambers 38A, 38B in order to operate the low speed type output cam, and the other solenoid valve 46 is opened, which in turn increases the speed. High-pressure hydraulic oil is introduced into the hydraulic chambers 39A and 39B to activate the mold output cam.

In this embodiment, since the above-mentioned three cams are used for both the intake valve and the exhaust valve, the hydraulic passages are branched into two downstream of the solenoid valves 45 and 46, and the hydraulic chamber for the intake valve is divided into two. The hydraulic oil is led to 38 A and 39 A through hydraulic passages 61 and 63, and to the exhaust valve hydraulic chambers 38 B and 39 B through hydraulic passages 62 and 64.

Further, a return passage returning to the oil tank is branched from a hydraulic passage 61 directed to the intake valve hydraulic chamber 38 A, and an electromagnetic valve 66 for opening and closing the return passage 65 is provided.

The solenoid valve 66 is controlled by the control unit 51 in conjunction with the operation of the solenoid valve 45. When the solenoid valve 45 is opened, it is opened after a certain period of time, and then the solenoid valve 45 is closed. Is also kept open.

As shown in FIG. 7, the above-mentioned fixed time is a time in which there is a margin in the time of t2 + t3. Even if the solenoid valve (solenoid valve) 45 is opened, the cam switching does not end immediately, and by the time the engagement (pin coupling) of both the main and sub rocker arms ends, Since the operation delay time, the hydraulic pressure rising time, and the time when the pins 32 and 33 are pushed out have to elapse, the solenoid valve 66 is opened after these times elapse.

When the solenoid valve 66 is opened, oil (operating oil) escapes to the return passage 65, so that the hydraulic pressure decreases. An orifice 67 for restricting the return flow rate is provided downstream of the solenoid valve 66 so as to keep this decrease to some extent. Since the differential pressure before and after the orifice is determined by the oil flow rate flowing through the orifice 67, the orifice cross-sectional area is determined so that the minimum hydraulic pressure that can maintain the engaged state of both rocker arms is maintained.

Here, the operation of this example will be described.

When the solenoid valve 45 is opened to activate the low-speed output cam, high-pressure hydraulic oil is supplied from the oil pump, and the pins 32 and 33 are pushed out, so that both the intake valve and the exhaust valve have rocker arms for both the main and sub rockers. Engage.

When the solenoid valve 66 is opened immediately after this engagement (a certain time after the solenoid valve 45 is controlled to be opened), the hydraulic oil in the hydraulic passages 61 and 62 is released to the return passage 65, and the rocker arms of both rocker arms are opened. The hydraulic pressure drops to the lowest hydraulic pressure that can maintain the engaged state. However, the engagement is not released.

After that, when the operating condition changes and there is a request for switching to the fuel consumption cam or the high speed type output cam, the solenoid valve 45 is closed.

At this time, since the hydraulic chambers 38A, 38B have the lowest hydraulic pressure capable of maintaining the engaged state, the springs 36 quickly push back the pins 32, 33 to release the engaged state in a responsive manner.

In other words, the force for releasing the engagement between the main rocker arm and the sub rocker arm is the difference between the pushing force of the spring 36 and the hydraulic force acting in the opposite direction. The more it is disengaged, the more the disengagement force is relatively increased, which makes it possible to shorten the disengagement time as compared with the case where the hydraulic pressure is not decreased and is kept as it is. In addition, the load on the oil pump is reduced due to the decrease in hydraulic pressure.

Since switching of the cam can be performed only by the base circle of the cam, the time required for switching of the cam is shortened in the high rotation speed range, so that it is necessary to release the engagement. If it takes a long time, there is a cylinder in which the base circle disappears before the disengagement, and the disengagement is delayed until the next base circle occurs. For example, the cam switching timing varies among the cylinders.

On the other hand, in this embodiment, by shortening the time for releasing the engagement, the cam switching can be continuously performed without variation.

Although the oil remaining in the hydraulic passages 61 and 62 after the electromagnetic valve 45 is closed is returned to a small extent through the orifice 67, most of it is provided in the electromagnetic valve 45 itself and when the electromagnetic valve 45 is opened. Since it is returned through the opening drain hole (not shown), provision of the orifice 67 does not delay the release of the engagement. Also, if the hydraulic pressure of the hydraulic oil is lowered from the stage of engaging both rocker arms, the engagement may be released, but it takes time to engage. After all, a high hydraulic pressure when engaged and a low hydraulic pressure when disengaged are required to shorten the cam switching time.

By the way, when switching from the low speed type to the high speed type output cam, it is sufficient to switch at the rotational speed at which the output is the same, but in the case of the fuel consumption cam, the throttle opening is the same and the output torque is the same. Since they do not match, a large torque step occurs at the time of switching. In order to absorb the torque step generated before and after such switching, in this embodiment, the throttle valve 56 is separated from the accelerator pedal so that the opening can be controlled independently as shown in FIG. The throttle opening and the ignition timing of the ignition device 57 are automatically corrected as much as necessary to absorb the torque step difference determined from the throttle opening and the rotation speed, and the outputs are matched.

At the time of switching from the low speed type output cam to the fuel consumption cam, since the disengagement of both rocker arms is delayed and the timing of actual cam switching and output correction is deviated, the torque step can be absorbed. Disappear.

However, when the disengagement time is short as in this embodiment, the cam switching timing becomes stable and the timings of the two are less likely to deviate, so that the torque step can be reliably absorbed. ..

Next, FIG. 8 shows another embodiment in which the return passage 68 returning to the oil tank is branched from the hydraulic passage 63 directed to the other hydraulic chamber 39A for the intake valve, and the passage 68 is opened and closed. An electromagnetic valve 69 for controlling the flow rate and an orifice 70 for restricting the return flow rate are provided. The solenoid valve 69 also opens after the fixed time when the solenoid valve 46 is opened, and is kept open even if the solenoid valve 46 is closed thereafter.

According to this example, the cam switching time can be shortened when switching from the high speed type output cam.

FIG. 9 shows another embodiment. In the above two embodiments, the solenoid valves 66 and 69 and the orifices 67 and 70 provided in the return passages 65 and 68 respectively change the hydraulic pressure downstream of the solenoid valves 45 and 46 in two stages. The variable oil pump 75 such as an axial piston pump can perform the same function. That is, when opening the solenoid valves 45 and 46, a high oil pressure is supplied by the variable oil pump 75, and after a certain period of time, the oil pressure is lowered to the lowest oil pressure that can maintain the engaged state. However, with respect to the responsiveness, the above embodiment is superior.

[0053]

[Effect of the device]

 In this invention, when the hydraulic switching valve is opened, hydraulic oil is supplied, the two types of rocker arms engage with each other, and from one cam to another cam, and when the hydraulic switching valve is closed, the rocker arm engages. In the one that is released and the cam is switched in the opposite way, an on-off valve that opens and closes this return passage in the return passage that branches the hydraulic passage downstream of the hydraulic switching valve and returns to the oil tank, and the hydraulic oil supplied to the hydraulic passage. Has an orifice that lowers the hydraulic pressure of the hydraulic pressure to the lowest hydraulic pressure that can maintain the engagement state of the rocker arm.When the hydraulic pressure switching valve is opened in conjunction with the operation of the hydraulic pressure switching valve, the opening / closing valve opens after a certain time. Even if the hydraulic switching valve is opened and then closed, it remains open, which reduces the burden on the oil pump and shortens the cam switching time from the other cam to the one cam. Cylinder Without the variation in the cam switching can be carried out continuously respond well cam switching between cylinders in emissions.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a plan view of a variable valve operating device according to an embodiment.

3 is a sectional view taken along line XX of FIG.

FIG. 4 is a characteristic diagram of a valve lift of the device.

FIG. 5 is a characteristic diagram of full-open torque of the device.

FIG. 6 is a configuration diagram of a control system of the embodiment.

FIG. 7 is an explanatory diagram showing a cam switch response delay.

FIG. 8 is a configuration diagram of a control system of another embodiment.

FIG. 9 is a configuration diagram of a control system of another embodiment.

FIG. 10 is a perspective view of a conventional variable valve operating device.

FIG. 11 is a partial cross-sectional plan view showing an operating state of a conventional example at low rotation speed.

FIG. 12 is a partial cross-sectional plan view showing an operating state of a conventional example at high rotation.

[Explanation of symbols]

 21 1st cam (fuel consumption cam) 22 2nd cam (low speed type output cam) 23 3rd cam (high speed type output cam) 24 intake / exhaust valve 25 main rocker arm 28,29 sub rocker arm 32-35 pin 38A, 38B Hydraulic chamber 39A, 39B Hydraulic chamber 45, 46 Electromagnetic valve (hydraulic switching valve) 51 Control unit 52 Crank angle sensor (engine speed sensor) 53 Accelerator operation amount sensor 61-64 Hydraulic passage 65 Return passage 66 Electromagnetic valve (open / close valve) 67 orifice 68 return passage 69 solenoid valve (open / close valve) 70 orifice 75 variable oil pump 81 cam 82 cam switching mechanism 83 hydraulic passage 84 hydraulic switching valve 85 control means 86 return passage 87 opening / closing valve 88 orifice 89 opening / closing control means

Claims (1)

[Scope of utility model registration request] 1. A plurality of cams having cam profiles having different output characteristics, and two types of rocker arms engage with each other when hydraulic pressure is supplied, and the rocker from one cam to another cam, and when the hydraulic pressure is not supplied, the rocker is supplied. A cam switching mechanism that disengages the arm to switch the cam in the opposite direction, and transmits the motion of the cam to at least one of the intake and exhaust valves, and the supply of hydraulic oil provided in a hydraulic passage to the cam switching mechanism. A valve that switches between releasing hydraulic oil and hydraulic oil to be supplied when switching from one cam to another cam is determined based on operating conditions, and when switching to the reverse is determined. In a variable valve operating system for an engine, comprising: a means for controlling the opening / closing of the hydraulic pressure switching valve so that hydraulic oil is released, a return passage branched from a hydraulic passage downstream of the hydraulic switching valve and returning to an oil tank, An opening / closing valve that opens and closes the return passage, an orifice that regulates the return flow rate so that the hydraulic pressure of the hydraulic oil supplied to the hydraulic passage decreases to the lowest hydraulic pressure that can maintain the engaged state of the rocker arm, and A means for controlling the opening / closing valve so as to be linked to the operation of the hydraulic pressure switching valve and opened when the hydraulic pressure switching valve is opened after a certain period of time, and to be kept open even if the hydraulic pressure switching valve is subsequently closed. A variable valve operating system for an engine, characterized by being provided with.