JPH0526016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention The present invention is an internal combustion engine for a vehicle, in which the compression ratio can be changed by adjusting the relative position of a piston, which is slidably fitted in a cylinder thereof, with respect to a crankshaft. The present invention relates to a variable compression ratio device of the above type.

(2) Conventional technology Conventionally, the compression ratio of an internal combustion engine is varied, for example, the compression ratio is increased when the engine is operating at low load, and the compression ratio is lowered when the engine is operated at high load, thereby preventing the occurrence of abnormal combustion such as knocking. A device that aims to improve fuel consumption and output performance while reducing fuel consumption is known (see, for example, Japanese Patent Laid-Open No. 58-38344).

(3) Problems to be Solved by the Invention However, in the above-mentioned conventionally known pistons, there is a pair of lock pin holes for locking the piston in the high compression ratio position and the low compression ratio position, and neither of the pin holes is connected to the lock pin holes. A locking device is made up of a common locking pin that can be fitted into the piston, and when switching the compression ratio, the locking device is first deactivated and the piston and piston pin move between the high compression ratio position and the low compression ratio position due to inertia. The lock pin is left in a state where it can move freely, and when both of them reach the desired compression ratio position, the lock pin is hydraulically actuated instantaneously.

However, the timing at which the common lock pin can engage with the lock pin hole on the high compression ratio side is only for a very short period at the end of the exhaust stroke during one cycle of an internal combustion engine, and it cannot engage with the lock pin hole on the low compression ratio side. Since the timing is very short compared to the timing when the lock pin can be engaged with the lock pin hole on the high compression ratio side, it is necessary to control the introduction timing of the hydraulic pressure to be applied to the lock pin with high precision. If the engine is operated at high speed, the cost will increase, and if the timing of introduction is even slightly different (this deviation becomes more likely to occur as the engine is operated at higher speeds), the lock pin cannot be immediately engaged with the lock pin hole on the high compression ratio side. Not only that, but there is also the risk of accidentally engaging the lock pin hole on the low compression ratio side, making it impossible to quickly and accurately switch the compression ratio depending on the operating condition of the engine. There are various problems such as the area being narrowed accordingly.

The present invention was proposed in view of the above, and includes a lock device exclusively for high compression ratios that locks the piston in a high compression ratio position, and a lock device exclusively for low compression ratios that locks the piston in a low compression ratio position. By providing the two locking devices independently from each other and selectively operating both locking devices according to the engine operating state, the above-mentioned problems of the conventional device can be solved. An object of the present invention is to provide a variable compression ratio device for a vehicle internal combustion engine that can always smoothly and accurately switch the compression ratio.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention improves the compression ratio by adjusting the relative position of the piston, which is slidably fitted into the cylinder, with respect to the crankshaft. The variable compression ratio device for a vehicle internal combustion engine is configured to include a first lock device that locks the piston at a low compression ratio position when activated, and a first lock device that is independent of this first lock device and that locks the piston at a low compression ratio position when activated. a second locking device that locks the piston at a high compression ratio position; and a second locking device that is connected to the first and second locking devices, and that is connected to the first and second locking devices so that the engine speed is lower than the first set value and the engine is at idle speed lower than the first set value. The first and second locking devices are selectively actuated depending on the engine operating condition only when the engine speed is higher than a second set value, and when the engine speed is lower than the second set value, the first and second locking devices are selectively activated. The invention is characterized in that it includes a control device that operates only one lock device.

(2) Effect A locking device exclusively for high compression ratios capable of locking the piston at a high compression ratio position and a locking device exclusively for low compression ratios capable of locking the same piston at a low compression ratio position are provided independently from each other. Since both lock devices are configured to operate selectively depending on the engine operating condition, when switching the compression ratio position, the lock device corresponding to the compression ratio to be switched is activated, and the other lock devices are activated. By simply holding the locking device in an inoperative state, lock switching can be effected quickly and accurately, thereby eliminating the risk of erroneous switching as in the prior art devices.

In particular, since the switching operation between the high compression ratio position and the low compression ratio position is possible only in the limited predetermined rotation range, the switching operation can always be performed smoothly and accurately. In addition, especially when the engine speed is lower than the second set value and the intake negative pressure fluctuates greatly even with the slightest movement of the accelerator, at or near the idle speed, the piston is held at the low compression ratio position. Since the switching operation can be restricted, problems (for example, deterioration of drivability and engine performance) caused by poor responsiveness of compression ratio switching compared to negative pressure fluctuations can be avoided.

(3) Examples Examples of the present invention will be described below with reference to the drawings.

1, 2A, and 2B show the engine at a low compression ratio and at the end of compression. A piston 2 that is slidably fitted into a cylinder 1 is formed with left and right pin bosses 3 and 4 that form a pair in the diametrical direction. It is rotatably suspended horizontally via 6. The piston pin P consists of left and right journal parts 7, 8 at both ends and a crank part 9 in the center, and the center _O2 of the crank part is located between the left and right journal parts 7, 8.
It is eccentric with respect to the center O ₁ of 8 by an eccentric amount e.

A disk-like flange portion 10 is integrally formed at the end of one journal portion, and this flange portion 1
0 is housed in an annular recess 11 formed on the outer end surface of the one pin boss. As shown in FIG. 1, the flange portion 10 has a high compression ratio side lock pin hole 12 and a low compression ratio side lock pin hole 13 on the top and bottom.
The lock pin hole 13 is provided with a lock pin 20 ₁ of a first lock device L ₁ (described later), and the lock pin hole 12 is provided with a lock pin 20 ₂ (third and fourth A) of a second lock device L ₂ (described later). (Fig.) are fitted in such a way that they can be inserted and removed.

A halved small end 14a of a connecting rod 14 is rotatably connected to the crank portion 9 of the piston pin P, and a halved large end 14b of the connecting rod 14 is rotatably connected to a crank pin 15a of a crankshaft 15. Can be freely connected.

Between the piston 2 and the piston pin P, a second A,
As shown in FIG. 2B, a first locking device is provided that can lock the crank portion 9 of the piston pin P in an upward position with respect to its left and right journal portions 7 and 8, that is, the piston 2 with respect to the piston pin P in a low compression ratio position.
_L1 , and as shown in FIGS. 4A and 4B, the crank part 9 of the piston pin P is in a downward position relative to the left and right journal parts 7 and 8, that is, the piston pin P
On the other hand, a second locking device _L2 capable of locking the piston 2 in the high compression ratio position is provided symmetrically with respect to the longitudinal center line l--l of the cylinder 1.

Next, the structure of the first locking device _L1 will be explained with reference to FIGS. 1, 2A, and 2B. One pin boss 4 of the piston 2 has a cylinder hole ₁₇₁ parallel to the piston pin P. This cylinder 17 ₁
A lock piston 18 ₁ is slidably fitted therein, and a hydraulic chamber 19 ₁ is defined by the lock piston 18 ₁ . The lock piston 18 ₁ is integrally provided with a lock pin 20 ₁ that can protrude and retract from the outer end surface _of the pin boss 4.
is projected in response to the hydraulic pressure in the hydraulic chamber 19 ₁ and retracted into the pin boss 4 by a return spring 21 ₁ provided in the cylinder 17 ₁ .

The hydraulic chamber 19 ₁ of the cylinder 17 ₁ communicates with an oil supply passage 23 ₁ formed in the connecting rod 14 via an oil passage 22 ₁ formed in the piston pin P, and furthermore, this oil supply passage 23 ₁ is formed in the crankshaft 15. The distribution oil passage 24 1 is connected to the distribution oil passage 24 ₁ . The distribution oil passage 24 ₁ is
It is communicated with the oil pump Pu via a switching valve V and a regulator R, as will be described in detail later.

As shown in FIG. 1, the oil passage 22 ₁ has a bifurcated shape when viewed from the cross-sectional direction of the piston pin P, and both opening ends thereof communicate with the hydraulic chamber 19 ₁ and the oil supply passage 23 ₁ . It's summery. When the switching valve V is switched to the low compression ratio side, the pressure oil from the oil pump Pu passes through the distribution oil passage 24 ₁ , the oil supply passage 23 ₁ and the oil passage 22 ₁ to the cylinder 17.
₁ hydraulic chamber 19 ₁ .

Next, the configuration of the second lock device _L2 on the high compression ratio side will be explained with reference to FIGS. 3, 4A, and 4B. This is similar to the first lock device L2 on the low compression ratio side.
It is constructed independently from L ₁ and has the same structure as L ₁ , and the longitudinal centerline l-l of cylinder 1.
symmetrically provided. That is, one pin boss 4 is formed with a cylinder 17 ₂ , and a lock piston 18 ₂ is slidably fitted into this cylinder 17 ₂ , and this lock piston 18 ₂ opens the hydraulic chamber 1 .
9 ₂ is defined. A _lock pin 20 ₂ is integrally provided with the lock piston 18 2 , and this lock pin 20 ₂ protrudes in response to the hydraulic pressure in the hydraulic chamber 19 ₂ , and is moved into the pin boss 4 by a return spring 21 ₂ provided in the cylinder 17 ₂ be immersed in.

The hydraulic chamber 19 ₂ of the cylinder 17 ₂ communicates with an oil supply passage 23 ₂ formed in the connecting rod 14 via an oil passage 22 ₂ formed in the piston pin P, and furthermore, this oil supply passage 23 ₂ is formed in the crankshaft 15. It passes through the distribution oil passage 24 ₂ and communicates with the oil pump Pu via the switching valve V. When the piston pin P rotates to the high compression ratio position, the oil passage 22 ₂ is communicated with the hydraulic chamber 19 ₂ and the oil supply passage 23 ₂ . When the switching valve V is switched to the high compression ratio side, the pressure oil from the oil pump Pu is transferred to the distribution oil path 24 ₂ and the oil supply path 2.
3 ₂ and the oil passage 22 ₂ to the hydraulic chamber 19 ₂ of the cylinder 17 ₂ .

FIG. 5 shows an oil supply system for supplying pressure oil to the cylinders 17 ₁ . . . , 17 _{2 .} . . in a four-cylinder engine. Here, the low compression ratio side oil supply system S ₁ is shown by a solid line, and the high compression ratio side oil supply system S ₂ is shown by a dotted line.

First, to explain the low compression ratio side oil supply system S ₁ (solid line), the main oil supply passage 25 ₁ connected to the switching valve V is branched into two distribution oil passages 24 ₁ () and 24 ₁ (), and one distribution The oil passage 24 ₁ () is the low compression ratio side oil supply passage 23 ₁ (), 23 ₁ () for the two cylinders on the left half.
The other distribution oil passage 24 ₁ () is connected to the low compression ratio side oil supply passage 23 ₁ () of the two cylinders in the right half,
23 ₁ ().

Next, to explain the high compression ratio side oil supply system S ₂ (dotted line), the other main oil supply passage 25 ₂ connected to the switching valve V is branched into two distribution oil passages 24 ₂ (), 24 ₂ (); The distribution oil passage 24 ₂ () is the high compression ratio side oil supply passage 23 ₂ (), 23 ₂ () for the two left cylinders.
The other distribution oil passage 24 ₂ () is connected to the high compression ratio side oil supply passage 23 ₂ () of the two cylinders in the right half,
23 ₂ ().

An inlet port of the switching valve V is communicated with an oil pump Pu via a regulator R.

The switching valve V is controlled by an output signal from a logic circuit 26. The logic circuit 26 includes a starter switch 27, a throttle opening 28,
Parameters for detecting the operating state of the engine, such as manifold negative pressure 29, vehicle speed 30, transmission shift position 31, and engine speed 32, are input.

The oil pump Pu, the regulator R,
The switching valve V, the logic circuit 26, and the oil passages connecting the switching valve V and each of the hydraulic cylinders 17 ₁ and 17 ₂ cooperate with each other to constitute the control device C of the present invention.

[] Low compression ratio (compression ratio approximately 9.5) operation of the engine When the switching valve V is switched to the low compression ratio side in response to the signal from the logic circuit 26, the valve V switches the oil pump Pu to the main oil supply path 25 ₁ communicate with.

Now the piston pin is the first and second lock device L ₁ ,
Not locked to any of L ₂ . In other words, assuming that the engine is operating with the piston pin P free, the piston enters the suction stroke and the piston descends, and when the acceleration gradually decreases and exceeds the point where it becomes zero, the piston 2 Since negative acceleration is applied until the piston reaches the dead center, braking is applied to the piston 2 during this period. However, since the piston 2 tries to move downward due to inertia due to its mass, the piston pin P, which is in an unstable state, is affected by the inertia and moves toward the low compression ratio side, that is, its crank portion as shown in Figures 2A and 2B. 9 is the left, right journal part 7,
Rotate it so that it faces upward relative to 8. At the end of suction of the piston 2, the oil passage 22 ₁ provided in the piston pin P communicates the oil supply passage 23 ₁ with the hydraulic chamber 19 ₁ in the cylinder 17 ₁ of the first lock device L ₁ and also connects the low compression ratio side lock pin. The hole 13 coincides with the lock pin 20 ₁ of the lock piston 18 ₁ (7th
Figure A). Therefore, the lock pin ₂₀₁ is the hydraulic chamber 19.
The _lock pin protrudes outward under the hydraulic pressure in the lock pin hole 13 and fits into the lock pin hole 13. As a result, the piston pin P is locked and moved to the low compression ratio position (1st, 2A, 2B
(Fig.) is maintained. As long as pressure oil is acting in the hydraulic chamber ₁₉₁ , the lock pin ₂₀₁ will not come out of the lock pin hole 13, so the piston 2 will remain at the low compression ratio position as shown by the chain line in FIG. Draw a motion curve C ₁ , and while the piston pin is held at the low position l (dashed line), inhale,
The engine is operated at a low compression ratio by repeating compression, explosion, and exhaust strokes.

Also, during the compression and explosion strokes, the internal pressure inside the cylinder 1 is high, so the piston 2 is biased downward by that pressure and tends to stay on the low compression ratio side, resulting in compression as shown in Figure 7 B and C. Even near the end of the explosion stroke, there is a chance that the lock pin ₂₀₁ can fit into the lock pin hole 13. Therefore, the timing for locking to the low compression ratio side by the first locking device _L1 is as shown in Fig. 7 A, B, and C. Inhalation as shown,
Three times near the end of each compression and explosion stroke.

Furthermore, if the supply of pressure oil to the first locking device _L1 is cut off in order to shift the engine from high-load operation to low-load operation, the acceleration of the piston 2 will be close to zero during the suction or exhaust stroke. When the force thereon becomes minimum, the friction between the lock pin ₂₀₁ of the first locking device and the lock pin hole 13 decreases, and the lock pin ₂₀₁ returns to the lock pin hole by the elastic force of the return spring ₂₁₁ . 13 and sinks into the pin boss 4, the piston pin P automatically becomes free.

[] Operation of the engine at a high compression ratio (compression ratio approximately 13) When the switching valve V is switched to the high compression ratio side in response to a signal from the logic circuit 26, the valve V
connects the oil pump Pu to the main oil supply path ₂₅₂ .
Now the piston pin P is connected to the first and second locking devices L ₁ ,
When the engine is running with the piston pin P free and not locked by any of _L2 , when the engine enters the exhaust stroke and nears its end, the internal pressure in the cylinder 1 drops to atmospheric pressure. Since the piston 2 is close to the piston 2 due to its own inertia, the piston 2 moves independently upwards with respect to the conrod 14, and at this time the piston pin P rotates approximately 180 degrees to the high compression ratio side, that is, Figs. 3, 4A, and 4B. As shown in , the crank portion 9 is rotated downward relative to the left and right journal portions 7 and 8. During the rotation process of the piston 2, the oil passage 22 provided in the piston pin P
₂ communicates the oil supply passage 23 ₂ with the hydraulic chamber 19 2 in the cylinder 17 ₂ of the second lock device L ₂ , and the lock pin hole ₁₂ coincides with the lock pin 20 ₂ of the lock piston 18 ₂ (see FIG. 8). ). Therefore, the lock pin ₂₀₂ fits into the lock pin hole 12, and the piston pin P is locked and held at the high compression ratio position (FIGS. 3, 4A, and 4B). As long as the pressure oil is acting in the hydraulic chamber ₁₉₂ of the second lock device _L2 , the lock pin ₂₀₂ will be locked in the lock pin hole 1.
2, the piston 2 remains at the high compression ratio position and draws a motion curve C ₂ as shown by the dotted line in Figure 6, and the piston 2 remains at the high position h (dotted line). The process of suction, compression, explosion and exhaust is repeated. When the piston 2 reaches the top dead center, the top dead center position of the piston 2 is 2 of the eccentricity e compared to the top dead center position during the compression ratio operation described above.
The engine is operated at a high compression ratio.

Incidentally, in the states shown in FIG. 8A to 8C, the piston pin P has no chance of being locked at the high compression ratio position.

When the supply of pressure oil to the cylinder ₁₇₂ of the second locking device _L2 is released, the acceleration of the piston 2 is close to zero, and the locking pin is locked in the middle of the suction or exhaust stroke, when the acceleration is close to zero. 20 ₂ sinks into the piston 2 by the elastic force of the return spring 21 ₂ , and the locked state between the piston pin P and the piston 2 is automatically released, and the piston 2 becomes free.

Therefore, from the low compression ratio operation mentioned above to the high compression ratio operation,
Or, while switching to the opposite, the piston pin P is temporarily in a free state, but when the engine is operated in this state, the position of the piston pin P changes, so the piston 2 is moved to the solid line in Figure 6. Draw a motion curve C ₃ as shown, and the piston pin P is high,
It reciprocates while fluctuating up and down (solid line) between the low positions h and l, but this curve changes depending on the engine speed and load and is not necessarily constant.

The low and high compression ratio operations are switched and controlled depending on the engine speed.

As shown in the graph of Figure 9 (horizontal axis - engine speed, vertical axis - intake pipe pressure, θth - throttle fully closed curve), the first set value A on the high-speed side of the engine speed (engine speed approximately 2500 rpm) and A second set value B (engine speed slightly less than 100 rpm) lower than that and higher than the idle speed of the engine is determined, and a speed higher than the first set value A and lower than the second set value B is determined. In this case, the engine is switched to at least the low compression ratio side so as to operate in the low compression zone Zl.
The reason for this will be explained below. When the engine is rotated at high speed, that is, when the speed is higher than the first set value A, the reciprocating speed of the piston in each stroke is fast and after switching of the switching valve V, the pressure oil flows into the cylinder 17 ₁ ,17 ₂
Due to the time delay in reaching lock pin 2
0, 20 ₁ coincides with the lock pin holes 12, 13 and the timing at which the pressure oil acts on the hydraulic chambers 19 ₁ , 19 ₂ are often slightly different from each other, and the above-mentioned compression ratio switching operation may be delayed. In addition, the inertial force applied to the piston 2 increases in proportion to the engine speed, and the piston pin P
After connecting the lock pins 20 ₁ and 20 ₂ , the piston 2
This is because when the lock pins 20 ₁ and 20 ₂ are operated, an excessive shearing force is applied to the lock pins 20 1 and 20 2 .
Furthermore, when the vehicle is starting, slowing down, or when the engine is idling (that is, when it is lower than the second set value B, which is higher than the idle speed), the engine's intake negative pressure is relatively high and the accelerator is not pressed. Even with a small amount of action, the intake negative pressure fluctuates greatly, and the cycle interval is relatively long, so the responsiveness of compression ratio switching is poor compared to the negative pressure fluctuations, and drivability and engine performance are affected by compression ratio switching. may worsen,
Therefore, it is desirable to hold the compression ratio at a low compression ratio position.

On the other hand, as shown in FIG. 9, an area where the engine speed is lower than the first setting value and higher than the second setting value B is a high compression ratio area Zh, and this area Zh
In this case, the engine is mainly operated at a high compression ratio to increase engine output and improve thermal efficiency.

Note that even in the high compression ratio operation region Zh, when the pressure inside the intake pipe is high, the engine is switched to low compression ratio operation for the above-mentioned reason. In addition, when the vehicle is running at high speed by shifting the settings to lower the engine speed, such as when operating at an over-pressure ratio, there is actually less demand for switching to high compression ratio operation, and even a slight movement of the accelerator will increase the engine speed. In such a case, since the engine speed changes and the frequency of compression ratio switching increases, the engine is switched to operation in the low compression ratio area Zl even if the engine speed is in the high compression ratio area Zh.

C. Effects of the Invention As described above, according to the present invention, there is provided a first lock device exclusively for low compression ratios that can lock the piston in a low compression position, and a first lock device exclusively for high compression ratios that can lock the piston in a high compression ratio position. The second lock device and the second lock device are provided independently from each other, and both lock devices are operated selectively depending on the engine operating condition, so when changing the compression ratio position, the compression ratio position to be changed is By simply holding the corresponding locking device in the active state and the other locking device in the inactive state, the lock switching can be performed quickly and accurately, and the control for the lock switching can therefore be performed. It is extremely simple and contributes to cost reduction, and in addition, there is no risk of switching errors as in the conventional device, and the compression ratio is always switched responsively according to the operating condition of the engine. It is possible to secure as wide an operating range of good combustion as possible.

In particular, selectively operating the first and second lock devices according to the engine operating conditions as described above is
Since the engine rotational speed is only in a limited predetermined rotational range between the first and second set values, the switching operation can always be performed smoothly and accurately. Moreover, when the engine speed is lower than the second set value and the engine speed is at or near the idle speed where even the slightest movement of the accelerator causes large fluctuations in intake negative pressure, the piston is held at the low compression ratio position and the piston is held at the low compression ratio position. Since the switching operation can be restricted, it is possible to avoid problems such as deterioration of drivability and engine performance due to poor responsiveness of compression ratio switching compared to negative pressure fluctuations.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a side view of the piston portion of the engine with the piston held at a low compression ratio position, and FIG. 2A is a sectional view taken along the line A-A in FIG. 1. , FIG. 2B is a schematic diagram of FIG. 2A, FIG. 3 is a side view of the piston portion of the engine with the piston held at a high compression ratio position, FIG. 4A is a sectional view taken along the line A-A in FIG. Figure 4B is Figure 4A
Figure 5 is a schematic diagram of the oil supply system, Figure 6 is a diagram showing the movement curve of the piston at high and low compression ratio positions and in the free state, and the position of the piston pin. FIG. 8 is a schematic diagram showing the low compression ratio lock timing, FIG. 8 is a schematic diagram showing the high compression ratio lock timing, and FIG. 9 is a graph showing the high and low compression ratio movement areas depending on the engine speed and intake pipe negative pressure. 1... Cylinder, 2... Piston, 15... Crankshaft, A, B... First and second setting values, C...
Control device, L ₁ , L ₂ . . . first and second lock devices.

Claims (1)

[Claims] 1 In a compression ratio variable device for a vehicle internal combustion engine, the compression ratio can be changed by adjusting the relative position of a piston 2 slidably fitted into a cylinder 1 with respect to a crankshaft 15. a first locking device _L1 that locks the piston 2 in a low compression ratio position; and a second locking device _L1 that is configured independently of the first locking device L1 and locks the piston 2 in a high compression ratio position when activated. ₂ and connected to the first and second locking devices L ₁ , L ₂ ,
Only when the engine speed is lower than the first set value A and higher than the second set value B, which is lower than the first set value A and higher than the idle speed, the first and second
a control device C that selectively operates the lock devices L ₁ and L ₂ according to the engine operating state, and operates only the first lock device L ₁ when the engine speed is lower than the second set value B; A variable compression ratio device for a vehicle internal combustion engine, comprising: