WO2020088532A1 - 冲程可变的可变压缩比机构及其控制方法 - Google Patents

冲程可变的可变压缩比机构及其控制方法 Download PDF

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Publication number
WO2020088532A1
WO2020088532A1 PCT/CN2019/114392 CN2019114392W WO2020088532A1 WO 2020088532 A1 WO2020088532 A1 WO 2020088532A1 CN 2019114392 W CN2019114392 W CN 2019114392W WO 2020088532 A1 WO2020088532 A1 WO 2020088532A1
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WIPO (PCT)
Prior art keywords
engine
compression ratio
variable
stroke
shaft
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PCT/CN2019/114392
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English (en)
French (fr)
Inventor
刘涛
林文
尹吉
刘俊杰
张树旻
杨乐
渠娜
刘君宇
张春辉
李树会
段景辉
马京卫
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长城汽车股份有限公司
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Application filed by 长城汽车股份有限公司 filed Critical 长城汽车股份有限公司
Publication of WO2020088532A1 publication Critical patent/WO2020088532A1/zh

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
    • F02B75/047—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of variable crankshaft position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D15/00—Varying compression ratio
    • F02D15/02—Varying compression ratio by alteration or displacement of piston stroke

Definitions

  • the invention relates to the technical field of engines, in particular to a variable compression ratio mechanism with variable stroke.
  • the invention also relates to a control method with the variable compression ratio mechanism with variable stroke.
  • the four strokes and compression ratio of the piston are invariable, which makes it difficult to meet the needs of the engine under different operating conditions.
  • the compression ratio at low loads, the compression should be made larger to improve the thermal efficiency of the engine to obtain lower fuel consumption, while at high loads, the compression should be made smaller to suppress knocking.
  • the traditional engine can only adopt a compromise solution for different loads, so that the above effects cannot be obtained.
  • the expansion stroke is long, the piston takes longer to work, and the engine does more work.
  • the expansion stroke and compression stroke of the traditional engine are the same and cannot be longer.
  • variable compression ratios In order to improve the running performance of the engine at different loads, current automobile manufacturers have proposed technical solutions with variable compression ratios.
  • this variable compression ratio scheme reduces the compression ratio to suppress knocking at high loads.
  • the expansion ratio of the piston also decreases, which leads to the problem that the piston has a short work time and the engine thermal efficiency decreases.
  • the present invention aims to propose a variable compression ratio mechanism with a variable stroke, so as to be able to adjust the compression ratio and the piston stroke, and improve the engine performance.
  • a variable stroke variable compression ratio mechanism is controlled by an engine control unit to adjust the engine piston stroke and compression ratio, and the variable stroke variable compression
  • the comparison mechanism includes a piston slidingly arranged in the engine block, rotating a crankshaft provided in the engine block and an eccentric shaft having an adjustment eccentric wheel, and rotating an adjustment link provided on the crank of the crankshaft, hinged to An execution link between one end of the adjustment link and the piston, and a drive link hinged to the other end of the adjustment link; further including:
  • a swing link is rotatably sleeved on the adjustment eccentric wheel, and one end of the swing link is hingedly connected to the drive link;
  • a control shaft is rotatably provided in the engine block, a control eccentric is provided on the control shaft, and the control shaft is drivingly connected to the crankshaft, and the phase between the crankshaft and the crankshaft is adjustable;
  • the follower link one end is rotated and sleeved on the control eccentric wheel, and the other end is hingedly connected to the swing link;
  • the eccentric shaft driving device is fixedly arranged relative to the engine cylinder, and is drivingly connected with the eccentric shaft to drive the eccentric shaft to rotate between two limit phases.
  • a follower with a phase adjuster is installed on the control shaft, and corresponding to the follower, a drive connection with the follower is installed on the crankshaft to drive the follower The active part that rotates with the crankshaft.
  • the driving part and the driven part are driven by a gear structure provided with meshing, or the driving part and the driven part are driven by a chain or a belt connected between the two.
  • the eccentric shaft driving device includes a motor fixed on the engine block, and a speed reduction mechanism connected to the power output end of the motor, and the power output end of the speed reduction mechanism is drivingly connected to the eccentric shaft.
  • the present invention has the following advantages:
  • the variable-stroke variable compression ratio mechanism of the present invention includes a control shaft having a control eccentric wheel, an eccentric shaft having an adjusting eccentric wheel, and a multi-link structure constituting the control shaft, the eccentric shaft, the crankshaft, and the piston.
  • the position of the top and bottom dead center of the piston can be changed by controlling the rotation of the control shaft, so that the compression and expansion stroke of the piston changes, and the stroke of the piston can be changed.
  • the position of the top dead center of the piston can also be changed, so that the volume of the combustion chamber can be changed, and thus the compression ratio of the engine can also be changed. Therefore, by changing the stroke and compression ratio of the piston, the relationship between the compression ratio and the expansion ratio of the engine can be changed, which can be adapted to the operating needs of different engine operating conditions, and ultimately can improve the performance of the engine.
  • the present invention also proposes a control method based on the variable compression ratio mechanism with variable stroke as described above, and the control method includes:
  • the phase between the control shaft and the crankshaft is controlled to be 0 ° to 60 °, so that the compression ratio of the engine is greater than the expansion ratio; or,
  • the phase between the control shaft and the crankshaft is controlled to be 180 ° to 250 °, so that the compression ratio of the engine is smaller than the expansion ratio; or,
  • the phase between the control shaft and the crankshaft is controlled to be 90 ° to 150 ° or 270 ° to 330 °, so that the compression ratio and the expansion ratio of the engine are the same.
  • control method also includes:
  • the eccentric shaft When the engine is running, the eccentric shaft is controlled to rotate between the two limit phases, so that the compression ratio and the expansion ratio of the engine are increased or decreased synchronously.
  • control method also includes:
  • the Atkinson cycle mode is adopted, and the phase between the control shaft and the crankshaft is controlled to be 180 ° to 250 °, so that the expansion ratio of the engine is greater than the compression ratio; and Controlling the rotation of the eccentric shaft between the two limiting phases, and as the engine load increases, the expansion ratio and compression ratio of the engine decrease, and as the engine load decreases, the engine compression ratio and The expansion ratio increases.
  • control method also includes:
  • the HCCI mode when the engine is running, the HCCI mode is adopted, and the phase between the control shaft and the crankshaft is controlled to be 90 ° to 150 °, so that the expansion ratio and compression ratio of the engine are the same;
  • the rotation of the eccentric shaft between the two limiting phases and as the engine load increases, the engine's expansion ratio and compression ratio decrease, and as the engine load decreases, the engine's compression ratio and expansion ratio decrease increase.
  • control method also includes:
  • the phase between the control shaft and the crankshaft is controlled to be 0 ° to 60 °, so that the expansion ratio of the engine is smaller than the compression ratio; and by controlling the eccentric shaft to the two limits
  • the control method of the variable-stroke variable compression ratio mechanism of the present invention can adjust the relationship between the compression ratio and the expansion ratio during engine operation to enable the engine to adapt to different operating modes and help the engine thermal efficiency Increase, reduce fuel consumption, or the realization of compression ignition in the cylinder, which can improve the running performance of the engine.
  • the control method of the present invention can reduce the expansion ratio while reducing the compression ratio, so that it can also ensure the working time of the piston and convert more combustion gas pressure into crankshaft power to improve the efficiency of the engine.
  • control method of the present invention can also facilitate the start of the engine and improve the emission performance at the start of the engine by the intake stroke, compression stroke greater than the expansion stroke, exhaust stroke, compression ratio greater than the expansion ratio when the engine starting temperature is low And, it can also reduce the compression ratio after the engine temperature is high, so as to prevent the damage of parts caused by the high temperature of the gas.
  • the use of a high compression ratio at a low load can reduce fuel consumption, and the use of a low compression ratio at a high load can also suppress knocking, which is very practical.
  • FIG. 1 is a schematic structural diagram of a variable compression ratio mechanism with variable stroke according to an embodiment of the present invention
  • FIG. 2 is a schematic structural diagram of a deceleration mechanism according to an embodiment of the invention
  • Figure 3 is a schematic diagram of the change of the top dead center of the piston when the eccentric shaft is controlled to rotate;
  • FIG. 5 is a schematic diagram of the piston top and bottom dead center and stroke when the phase of the control shaft and the crankshaft is ⁇ P1;
  • FIG. 6 is a schematic diagram of the piston top and bottom dead center and stroke when the phase of the control shaft and the crankshaft is ⁇ P2;
  • FIG. 7 is a schematic diagram of the piston top and bottom dead center and stroke when the phase of the control shaft and the crankshaft is ⁇ P3;
  • FIG. 8 is a schematic diagram of the piston top and bottom dead center and stroke when the phase of the control shaft and the crankshaft is ⁇ P4;
  • FIG. 10 is a schematic diagram of the piston top and bottom dead center and stroke when the engine adopts Atkinson cycle mode
  • FIG. 11 is a schematic diagram of the piston top and bottom dead center and stroke when the engine is started;
  • This embodiment relates to a variable compression ratio mechanism with variable stroke, which is controlled by an engine control unit to enable adjustment of the engine piston stroke and compression ratio, as shown in FIG. 1
  • the overall structure includes a piston 1, a crankshaft 4, an eccentric shaft 7, a control shaft 9, and an actuator connecting rod 2, an adjusting connecting rod 3, a driving connecting rod 5 and a swinging connecting rod provided between the above components 6 and the follower link 8 constitute a multi-link structure.
  • the piston 1 is slidably disposed in the cylinder of the engine cylinder, and can reciprocate up and down in the cylinder.
  • the crankshaft 4, the eccentric shaft 7, and the control shaft 9 are all rotatably disposed in the engine cylinder. Refer to the related structure in the existing engine, which will not be repeated here.
  • the eccentric shaft 7 is fixed with an adjustment eccentric wheel
  • the control shaft 9 is also fixed with a control eccentric wheel.
  • the structure of the shaft body with the eccentric wheel can still refer to the related structure in the existing engine. It will be repeated.
  • the adjusting link 3 is rotatably fitted on the crank of the crankshaft 4, one end of the executing link 2 is hingedly connected to the piston 1, and the other end of the implementing link 2 is connected to one end of the adjusting link 3.
  • the two ends of the execution link 5 are hingedly connected to the other end of the adjusting link 3 and the one end of the swing link 6, the swing link 6 rotates and is sleeved on the adjusting eccentric wheel in the eccentric shaft 7, and one end of the follow link 8
  • the other end of the swing link 6 is hingedly connected, and the other end of the follower link 8 is rotated and sleeved on the control eccentric wheel on the control shaft 9.
  • variable compression ratio mechanism with variable stroke in this embodiment further includes an eccentric shaft drive device fixedly arranged relative to the engine block.
  • the eccentric shaft drive device is drive-connected with the eccentric shaft 7 to drive the eccentric shaft 7 Rotate between two limit phases.
  • the above-mentioned control shaft 9 is also designed to be drivingly connected with the crankshaft 4, and the phase between the control shaft 9 and the crankshaft 4 is also adjustable.
  • a follower 10 having a phase adjuster is installed on the control shaft 9.
  • the crankshaft 4 is provided with a The driven part 10 drives the connected active part 11.
  • the driving part 11 and the driven part 10 can be driven by the gear structure shown in the figure, which is driven by the gear 11, so that the driven part 11 can drive the driven part 10, that is, the control shaft 9 to rotate with the crankshaft 4.
  • the driving part 11 and the driven part 10 can also be driven by a chain or belt connected between the two. Both of these transmission forms can be borrowed from the existing conventional The chain transmission structure or belt transmission structure is sufficient.
  • the driven part 10 provided with a phase adjuster it can draw on the mature structure of the phase adjustment part of the intake and exhaust camshafts in the existing engine.
  • the speed ratio between the two may generally be set to 2: 1.
  • the aforementioned eccentric shaft driving device for driving the eccentric shaft 7 specifically includes a motor fixed on the engine block, and a deceleration mechanism connected to the power output end of the motor.
  • the power output of the deceleration mechanism is connected to the eccentric shaft 7 to drive the eccentric shaft 7, and it should be noted that, preferably, the above deceleration mechanism may be a harmonic reducer, or the deceleration mechanism may also be visible In the circumstances, the two-stage deceleration structure is adopted, but the one-stage deceleration structure still adopts the harmonic reducer.
  • the overall structure of the deceleration mechanism includes a harmonic reducer, and the drive is connected to the harmonic
  • the output shaft 15 at the power output end of the reducer and the front-stage reduction unit drivingly connected to the power input end of the harmonic reducer, which is connected to the above-mentioned motor transmission, and constitutes the rotation of the motor 12 to drive the force
  • the transmission of the wave speed reducer, and the rotation axis of the motor 12 is set parallel to the axis of the output shaft due to the transmission of the pre-stage speed reduction unit.
  • the front stage reduction unit of this embodiment may use, for example, a gear reduction mechanism.
  • the gear reduction mechanism specifically includes a driving gear 16 fixedly connected to the rotating shaft 21 of the motor 12, and meshing with the driving gear 16 and fixing The driven gear 20 connected to the power input end of the harmonic reducer.
  • the gear reduction mechanism By using the gear reduction mechanism to constitute the front stage reduction unit, the overall volume of the reduction transmission mechanism can be reduced.
  • the front-stage reduction unit may also use a chain reduction mechanism or a belt reduction mechanism, and the installation method in the reduction transmission mechanism is the same as that of the gear reduction mechanism.
  • the specific structure of the harmonic reducer of this embodiment can refer to the prior art. In terms of specific structure, it mainly includes a harmonic reducer steel wheel 14 connected to an external member. Harmonic reducer steel wheel 14 meshes with connected harmonic reducer flex wheel 18 and harmonic reducer generator 19 with input shaft in harmonic reducer flex wheel 18, the input shaft is The moving gear 10 is fixedly connected, and the flexible gear 18 of the harmonic reducer is in driving connection with the aforementioned output shaft 15.
  • the housing 13 where the power supply machine 12 is installed is fixed to the side of the harmonic speed reducer steel wheel 14 close to the front stage speed reduction unit.
  • the driving gear 16 and the driven gear 20 are built in the housing 13.
  • the input shaft may be specifically fixed to the harmonic reducer generator 19 by screwing, welding, or interference press fitting.
  • a bearing unit 17 fixed on the steel wheel 14 of the harmonic reducer is provided on the output shaft 15 side.
  • the structure of the bearing unit 17 of this embodiment is similar to the existing structure, as shown in FIG. 2, which specifically includes an outer ring assembly 171 fixedly connected to the harmonic reducer steel wheel 14 to remain stationary, and rolling The assembly rotates the inner ring assembly 172 embedded in the outer ring assembly 171.
  • the aforementioned output shaft 15 is fixedly connected to the inner ring assembly 172, and at the same time, the inner ring assembly 172 also forms a fixed connection with the harmonic reducer flex wheel 18 to accept the harmonic reducer flex wheel 18 to rotate and then drive The output shaft 15 rotates, and the power output of the motor 12 is realized.
  • an oil storage cavity is formed between the housing 13, the harmonic reducer steel wheel 14 and the bearing unit 17 and opened on the harmonic reducer steel wheel 14 There are lubricating oil holes to fill the oil storage cavity.
  • a sealing structure is provided between the housing 13 and the motor 12, and between the housing 13 and the harmonic reducer steel wheel 14, the sealing structure may specifically be sandwiched between the housings
  • the sealing gasket between 13 and the motor 12 and between the housing 13 and the harmonic reducer steel wheel 14 may be a sealing ring clamped on one of the two.
  • both the phase adjuster in the follower 10 and the motor in the eccentric shaft drive device are electrically connected to the engine control unit to be controlled by the engine control unit to perform the corresponding action response.
  • the phase of the rotation of the aforementioned eccentric shaft 7 can be represented by “ ⁇ ”, and the two limit phases of the eccentric shaft 7 under the drive of the motor can be specifically defined by “ ⁇ 1” and “ ⁇ 2, respectively. "To express. At this time, in this embodiment, for example, ⁇ 1 may be 34 °, and ⁇ 2 may be -21 °, and the eccentric shaft 7 reciprocates between the two phases.
  • the piston 1 in this embodiment reciprocates up and down in the cylinder, and the crankshaft 4 can be driven to rotate by executing the connecting rod 2 and adjusting the connecting rod 3.
  • the crankshaft 4 makes two revolutions per working cycle, and the piston 1 moves up and down four times, which are the intake stroke, compression stroke, expansion stroke, and exhaust stroke, respectively.
  • the control shaft 9 makes one revolution every working cycle, and the position of the piston 1 changes in a high-medium-low-medium-high cycle.
  • the high and low positions of the piston 1 correspond to different top and bottom dead centers, and the piston 1 up and down
  • phase between the control shaft 9 and the crankshaft 4 can be represented by " ⁇ p", which can be distinguished by adding different Arabic numerals after " ⁇ p" for different phase values .
  • the phase ⁇ p1 between the control shaft 9 and the crankshaft 4 can be controlled from 90 ° to 150 °.
  • the intake bottom dead center D1 and the expansion bottom stop The point D1 'is the same, the exhaust top dead center T1 is lower than the compression top dead center T1', the intake stroke LI1, the exhaust stroke LE1 is less than the expansion stroke LD1, the compression stroke LC1, and the compression ratio is equal to the expansion ratio.
  • the phase ⁇ p2 between the control shaft 9 and the crankshaft 4 may be controlled to be 180 ° to 250 °.
  • the intake bottom dead center D2 is higher than the expansion bottom dead center D2 '
  • Exhaust top dead center T2 is the same as compression top dead center T2'
  • the intake stroke LI2 the compression stroke LC2 are smaller than the expansion stroke LD2
  • the exhaust stroke LE2 the compression ratio is smaller than the expansion ratio.
  • the phase ⁇ p3 between the control shaft 9 and the crankshaft 4 can be controlled to be 270 ° -330 °.
  • the phase ⁇ p4 between the control shaft 9 and the crankshaft 4 can be controlled to be 0 ° to 60 °.
  • the intake bottom dead center D4 is lower than the expansion bottom dead center D4 ′
  • the exhaust top dead center T4 is the same as the compression top dead center T4 '.
  • the intake stroke LI4, the compression stroke LC4 are greater than the expansion stroke LD4, and the exhaust stroke LE4.
  • the compression ratio is greater than the expansion ratio.
  • this embodiment needs to explain that, while the engine is operating, the eccentric shaft 7 is controlled between its two limit phases, that is, ⁇ 1- ⁇ 2 Rotating between them can also increase or decrease the engine's compression ratio and expansion ratio simultaneously.
  • the swing link 6 pushes the drive link 5 upward, the drive link 5 pushes the adjustment link 3 to rotate counterclockwise, and the link 2 is moved downward, pulling the piston 1 to move downward, and the bottom dead center of the piston 1 changes from D1 to D5 , Decreases by ⁇ D, the top dead center of piston 1 changes from T1 to T5, and decreases by ⁇ T.
  • the compression ratio and the expansion ratio decrease simultaneously, and the four strokes of the piston (LI1, LC1, LD1, LE1) are almost unchanged.
  • the angle of the eccentric shaft 7 changes accordingly.
  • the eccentric shaft 7 rotates clockwise, driving the swing link 6 to rotate clockwise, while the follower link 8 reverses The hour hand rotates and the angle changes.
  • the swing link 6 pulls the drive link 5 down, the drive link 5 pulls the adjustment link 3 to rotate clockwise, executes the link 2 to move upward, and pushes the position of the piston 1 upward, and the bottom dead center of the piston 1 changes from D5 to D1 and rises ⁇ D, the top dead center of piston 1 changes from T5 to T1, and rises by ⁇ T.
  • the compression ratio and expansion ratio increase simultaneously, but the four strokes of the piston (LI1, LC1, LD1, LE1) are almost unchanged.
  • the above-mentioned different operating states such as the compression ratio being greater than the expansion ratio, the compression ratio being less than the expansion ratio, and the compression ratio being equal to the expansion ratio can be achieved.
  • the transition state between any two of the above-mentioned states can generally be achieved as needed to adapt to more operating conditions of the engine.
  • the Atkinson cycle mode may be adopted in the normal operation of the engine.
  • the control shaft 9 and the crankshaft may be controlled.
  • the phase between 4 is ⁇ p2 (180 ° ⁇ 250 °), so that the expansion ratio of the engine is greater than the compression ratio, and in operation, by controlling the rotation of the eccentric shaft 7 between its two limit phases, it increases with the load of the engine.
  • the high makes the engine's expansion ratio and compression ratio decrease, or increases the engine's compression ratio and expansion ratio as the engine load decreases. This not only improves engine efficiency, but also suppresses knocking when the engine load is high.
  • the piston 1 has a long expansion stroke and a long work time, which can convert more gas pressure generated by combustion into the power of the crankshaft 4, which can improve the work efficiency of the gas in the cylinder and reduce fuel consumption.
  • the compression ratio is large, the temperature during ignition is high, the combustion efficiency is high, the fuel is burned more fully, and the fuel consumption is lower, and the emissions are cleaner.
  • the upper and lower dead center positions of the piston 1 are lowered, and the top dead center T6 / T6 'and the bottom dead center D6 / D6' become the top dead center T2 / T2 'and the bottom dead center D2 / D2'. Since the top dead center position is lowered, the compression ratio is lowered, the temperature of the gas in the cylinder is lowered during ignition, and the tendency of spontaneous combustion of the fuel is reduced, thereby suppressing the occurrence of knocking.
  • the expansion stroke LD6 is still long, the expansion ratio is large, and the work efficiency of the piston 1 is still high, and due to the long gas expansion time in the cylinder, the gas temperature is low at the end of the expansion stroke, and the exhaust temperature can be reduced to prevent exhaust parts Thermal damage has occurred.
  • the higher the engine load the closer the phase of the eccentric shaft 7 is to ⁇ 2 until the limit position is reached, otherwise, the closer the phase of the eccentric shaft 7 is to ⁇ 1.
  • variable compression ratio mechanism with variable stroke in this embodiment can also set the HCCI mode to be used when the engine is running normally.
  • the phase between the control control shaft 9 and the crankshaft 4 is ⁇ p1 (90 ° ⁇ 150 °), so that the expansion ratio and compression ratio of the engine are the same.
  • the expansion ratio and compression ratio of the engine are reduced as the engine load increases, or the compression ratio and expansion of the engine are reduced as the engine load decreases Than increase.
  • the phase of the eccentric shaft 7 is adjusted to ⁇ 1, and the position of the exhaust top dead center T1 of the piston 1 is lower than the position of the compression top dead center T1 ′
  • the position of the intake bottom dead center D1 is almost the same as the position of the expansion bottom dead center D1 ′, and the intake stroke LI1 and the exhaust stroke LE1 are smaller than the expansion stroke LD1 and the compression stroke LC1.
  • a long compression stroke LC1 a larger compression ratio can be obtained, and the gas pressure and temperature in the cylinder are higher at the end of compression.
  • the exhaust stroke LE1 is short, the exhaust top dead center T1 is low, and there is much residual high-temperature exhaust gas in the cylinder. Based on the above two points, a higher in-cylinder pressure and temperature can be obtained during ignition, which is conducive to gasoline compression ignition and can increase the achievable range of HCCI.
  • the expansion stroke of the piston 1 is long and the work time is long, which can convert more gas pressure generated by combustion into the power of the crankshaft 4, thereby also improving the work efficiency of the gas in the cylinder and reducing fuel consumption.
  • the top dead center of the piston 1 is lowered, and the compression ratio is lowered, so that the degree of compression of the gas near the top dead center is lowered, the temperature and pressure are lowered, and the tendency of spontaneous combustion of the fuel is reduced, thereby suppressing the occurrence of knock.
  • the phase of the eccentric shaft 7 can be made closer to ⁇ 2 until the limit position is reached, and conversely, the phase of the eccentric shaft 7 is closer to ⁇ 1.
  • the phase between the control shaft 9 and the crankshaft 4 can be controlled to be ⁇ p4 (0 ° -60 °), so that the engine
  • the expansion ratio is smaller than the compression ratio, and by controlling the rotation of the eccentric shaft 7 between its two limit phases, the expansion ratio and compression ratio of the engine decrease as the engine temperature increases. In order to improve the starting performance of the engine.
  • the phase between the control shaft 9 and the crankshaft 4 is ⁇ p4
  • the exhaust top dead center of the piston 1 is almost the same as the compression top dead center
  • the intake bottom dead center is lower than the expansion bottom dead center
  • the intake stroke LI4 compression stroke LC4 is greater than expansion stroke LD4, and exhaust stroke LE4.
  • the phase of the eccentric shaft 7 can be adjusted to ⁇ 1.
  • the intake lift is long, more fresh air can enter the cylinder, and the compression stroke is long, the compression ratio is large.
  • the pressure is higher. This can improve the combustion process at start-up, improve idle speed stability, make the fuel burn more fully, and reduce harmful gas emissions.
  • the temperature at the end of the expansion stroke is higher and the exhaust temperature is higher.
  • the catalyst light-off speed can also be greatly improved. And further improve the emission performance at startup.
  • the phase of the eccentric shaft 7 can be gradually adjusted from ⁇ 1 to ⁇ 2.
  • the top and bottom dead centers of the piston 1 descend, and the top dead center T4 / T4 ',
  • the bottom dead center D4 / D4 ' becomes the top dead center T7 / T7' and the bottom dead center D7 / D7 '.
  • the top dead center of the piston 1 is lowered, the compression ratio is lowered, the temperature and pressure during ignition are lowered, and the combustion temperature is lowered, so that it is possible to prevent parts from being damaged due to an excessively high gas temperature.

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  • Chemical & Material Sciences (AREA)
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Abstract

一种冲程可变的可变压缩比机构及其控制方法，该冲程可变的可变压缩比机构受控于发动机控制单元，以进行发动机活塞(1)冲程及压缩比的调节，且其包括滑动设于发动机缸体中的活塞(1)，转动设于所述发动机缸体中的曲轴(4)和具有调节偏心轮的偏心轴(7)，以及转动设于所述曲轴(4)的曲柄上的调节连杆(3)，铰接于所述调节连杆(3)的一端与所述活塞(1)之间的执行连杆(2)，和铰接于所述调节连杆(3)的另一端的驱动连杆(5)；还包括摆动连杆(6)，转动设于所述发动机缸体中的具有控制偏心轮的控制轴(9)，以及随动连杆(8)，和偏心轴驱动装置。所述的冲程可变的可变压缩比机构能够实现对压缩比及活塞(1)冲程进行调节，而可提升发动机的性能。

Description

冲程可变的可变压缩比机构及其控制方法 技术领域
本发明涉及发动机技术领域，特别涉及一种冲程可变的可变压缩比机构，本发明同时也涉及有该冲程可变的可变压缩比机构的控制方法。
背景技术
传统汽油发动机中活塞四个冲程和压缩比均是不可变的，难以满足发动机不同工况下的需求。对于发动机压缩比而言，在低负荷时，应使压缩比较大，以提高发动机热效率，而获得较低的油耗，而在高负荷时，则应使压缩比较小，以用于抑制爆震。不过传统发动机因压缩比的不可变，对于不同负荷只能采取折中方案，从而不能获得上述效果。对于活塞冲程来说，膨胀行程长，则活塞做功时间长，发动机做功更多，但受制于现有的曲柄连杆结构，传统发动机的活塞膨胀行程和压缩行程相同，无法做到更长。
为可于不同负荷时，提高发动机的运行性能，目前已有汽车厂家提出了压缩比可变的技术方案，但这种压缩比可变方案，在高负荷时为抑制爆震降低了压缩比，但活塞膨胀比也随之降低，从而存在导致活塞做功时间短，发动机热效率下降的问题。
发明内容
有鉴于此，本发明旨在提出一种冲程可变的可变压缩比机构，以能够对压缩比及活塞冲程进行调节，而提升发动机性能。
为达到上述目的，本发明的技术方案是这样实现的：
一种冲程可变的可变压缩比机构，该冲程可变的可变压缩比机构受控于发动机控制单元，以进行发动机活塞冲程及压缩比的调节，且所述冲程可变的可变压缩比机构包括滑动设于发动机缸体中的活塞，转动设于所述发动机缸体中的曲轴和具有调节偏心轮的偏心轴，以及转动设于所述曲轴的曲柄上的调节连杆，铰接于所述调节连杆的一端与所述活塞之间的执行连杆，和铰接于所述调节连杆的另一端的驱动连杆；还包括：
摆动连杆，转动套装于所述调节偏心轮上，且所述摆动连杆的一端与所述驱动连杆铰接相连；
控制轴，转动设于所述发动机缸体中，于所述控制轴上设有控制偏心轮，且所述控制轴与所述曲轴传动连接，并与所述曲轴间的相位可调设置；
随动连杆，一端转动套装于所述控制偏心轮上，另一端与所述摆动连杆铰接相连；
偏心轴驱动装置，相对于所述发动机缸体固定设置，并与所述偏心轴传动连接，以能够驱使所述偏心轴于两限位相位间转动。
进一步的，于所述控制轴上装设有具有相位调节器的从动部，对应于所述从动部，于所述曲轴上装设有与所述从动部传动连接、以驱使所述从动部随所述曲轴转动的主动部。
进一步的，所述主动部与所述从动部间由啮合设置的齿轮结构传动，或者，所述主动部与所述从动部通过连接设于两者之间的链条或皮带传动。
进一步的，所述偏心轴驱动装置包括固定于所述发动机缸体上的电机，以及连接于所述电机动力输出端的减速机构，所述减速机构的动力输出端与所述偏心轴传动相连。
进一步的，所述减速机构中至少有谐波减速器。
相对于现有技术，本发明具有以下优势：
本发明的冲程可变的可变压缩比机构，通过具有控制偏心轮的控制轴和具有调节偏心轮的偏心轴，以及构成上述控制轴、偏心轴与曲轴、活塞之间的多连杆结构的设置，可经由控制控制轴的转动改变活塞上下止点的位置，使得活塞压缩和膨胀行程发生变化，而实现对活塞冲程的改变。同时，经由控制偏心轴的转动亦可使活塞上止点位置变化，使得燃烧室容积变化，进而也能够实现对发动机压缩比的改变。由此，通过对活塞冲程和压缩比的改变，可使发动机压缩比与膨胀比的关系发生变化，以此能够适合不同发动机工况的运行需要，而最终可提升发动机的性能。
本发明同时也提出了基于如上所述的冲程可变的可变压缩比机构的控制方法，且该控制方法包括：
于发动机运行时，控制所述控制轴与所述曲轴之间的相位为0°～60°，而使所述发动机的压缩比大于膨胀比；或者，
于发动机运行时，控制所述控制轴与所述曲轴之间的相位为180°～250°，而使所述发动机的压缩比小于膨胀比；或者，
于发动机运行时，控制所述控制轴与所述曲轴之间的相位为90°～150°或270°～330°，而使所述发动机的压缩比与膨胀比相同。
进一步的，该控制方法还包括：
于所述发动机运行时，控制所述偏心轴于两所述限位相位间转动，而使所述发动 机的压缩比与膨胀比同步增加或减小。
进一步的，该控制方法还包括：
或者，于所述发动机运行时，采用阿特金森循环模式，并控制所述控制轴与所述曲轴之间的相位为180°～250°，使所述发动机的膨胀比大于压缩比；且通过控制所述偏心轴于两所述限位相位间的转动，而随发动机负荷的升高使所述发动机的膨胀比和压缩比减小，以及随发动机负荷的降低使所述发动机的压缩比和膨胀比增加。
进一步的，该控制方法还包括：
或者，于所述发动机运行时，采用HCCI模式，并控制所述控制轴与所述曲轴之间的相位为90°～150°，使所述发动机的膨胀比与压缩比相同；且通过控制所述偏心轴于两所述限位相位间的转动，而随发动机负荷的升高使所述发动机的膨胀比和压缩比减小，以及随发动机负荷的降低使所述发动机的压缩比和膨胀比增加。
进一步的，该控制方法还包括：
于所述发动机启动时，控制所述控制轴与所述曲轴之间的相位为0°～60°，使所述发动机的膨胀比小于压缩比；且通过控制所述偏心轴于两所述限位相位间的转动，而随发动机温度的升高使所述发动机的膨胀比和压缩比减小。
本发明的冲程可变的可变压缩比机构的控制方法，在发动机运行中可通过调整压缩比与膨胀比之间的关系，以能够使发动机适应不同的运行模式，并能够助于发动机热效率的提高，降低油耗，或者缸内压燃的实现，从而可提升发动机的运行性能。并且本发明的控制方法在降低压缩比的同时，可使膨胀比不降低，因而也能够保证活塞做功时长，将更多燃烧气体压力转化为曲轴动力，以改善发动机的效率。
此外，本发明的控制方法亦可在发动机启动温度较低时，通过进气行程、压缩行程大于膨胀行程、排气行程，压缩比大于膨胀比，而利于发动机的启动，改善启动时的排放性能，且还能够在发动机温度较高后，降低压缩比，以可防止气体高温造成零件损坏。
另外，本发明的控制方法中通过压缩比的可变，在低负荷使用高压缩比能够降低油耗，在高负荷使用低压缩比亦能够抑制爆震，而有着很好的实用性。
附图说明
构成本发明的一部分的附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1为本发明实施例所述的冲程可变的可变压缩比机构的结构示意图；
图2为本发明实施例所述的减速机构的结构示意图
图3为控制偏心轴转动时活塞上止点变化的示意图；
图4为控制偏心轴转动时活塞下止点变化的示意图；
图5为控制轴与曲轴相位为αP1时活塞上、下止点及行程的示意图；
图6为控制轴与曲轴相位为αP2时活塞上、下止点及行程的示意图；
图7为控制轴与曲轴相位为αP3时活塞上、下止点及行程的示意图；
图8为控制轴与曲轴相位为αP4时活塞上、下止点及行程的示意图；
图9为控制偏心轴在两限位相位间转动时活塞上、下止点及行程的示意图；
图10为发动机采用阿特金森循环模式时活塞上、下止点及行程的示意图；
图11为发动机启动时活塞上、下止点及行程的示意图；
附图标记说明：
1-活塞，2-执行连杆，3-调节连杆，4-曲轴，5-驱动连杆，6-摆动连杆，7-偏心轴，8-随动连杆，9-控制轴，10-从动部，11-主动部，12-电机，13-壳体，14-谐波减速器钢轮，15-输出轴，16-主动齿轮，17-轴承单元，171-外圈组件，172-内圈组件，18-谐波减速器柔轮，19-谐波减速器发生器，20-从动齿轮，21-转动轴。
具体实施方式
需要说明的是，在不冲突的情况下，本发明中的实施例及实施例中的特征可以相互组合。
下面将参考附图并结合实施例来详细说明本发明。
本实施例涉及一种冲程可变的可变压缩比机构，该冲程可变的可变压缩比机构受控于发动机控制单元，以能够进行发动机活塞冲程及压缩比的调节，且如图1中所示，其整体结构上包括活塞1、曲轴4、偏心轴7、控制轴9，以及设置于上述各部件之间的由执行连杆2、调节连杆3、驱动连杆5及摆动连杆6和随动连杆8构成的多连杆结构。
具体的，活塞1滑动设置于发动机缸体内的缸筒中，并可在缸筒中上下往复运动，曲轴4、偏心轴7和控制轴9均转动设置在发动机缸体中，其具体转动布置形式可参见现有发动机中的相关结构，在此对其不再赘述。在偏心轴7上套装固定有调节偏心轮，在控制轴9上亦套装固定有控制偏心轮，该具有偏心轮的轴体结构仍可参见现有发动机中的相关结构，本文也同样不再对其进行赘述。
上述多连杆结构中，调节连杆3转动套装在曲轴4上的曲柄处，执行连杆2的一端与活塞1铰接相连，执行连杆2的另一端则与调节连杆3的一端相连。执行连杆5的两端分别与调节连杆3的另一端以及摆动连杆6的一端铰接相连，摆动连杆6转动套装在偏心轴7中的调节偏心轮上，随动连杆8的一端与摆动连杆6的另一端铰接相连，随动连杆8的另一端则转动套装于控制轴9上的控制偏心轮上。
一般的，上述各连杆结构之间的铰接均可通过连接销结构实现。而本实施例的冲程可变的可变压缩比机构进一步的还包括有相对于发动机缸体固定设置的偏心轴驱动装置，该偏心轴驱动装置与偏心轴7传动连接，以可驱使偏心轴7于两个限位相位之间转动。此外，本实施例中上述的控制轴9亦被设计为与曲轴4传动连接，且控制轴9与曲轴4之间的相位也为可调设置。
详细来说，仍如图1中示出的，本实施例在控制轴9上装设有具有相位调节器的从动部10，对应于该从动部10，在曲轴4上则装设有与从动部10传动连接的主动部11。其中，主动部11与从动部10之间可采用图中所示的由啮合设置的齿轮结构进行传动，以可由主动部11驱使从动部10、也即控制轴9随曲轴4转动。
当然，除了采用齿轮啮合方式进行传动，主动部11与从动部10之间也可通过连接设于两者之间的链条或皮带传动，对于这两种传动形式均可借鉴于现有的常规链条传动结构或皮带传动结构便可。而对于设置有相位调节器的从动部10，其可借鉴现有发动机中的进、排气凸轮轴相位调节部分的成熟结构。
本实施例中，对于传动相连的曲轴4和控制轴9，一般可设置两者之间的转速比为2：1。而前述的用于驱使偏心轴7转动的偏心轴驱动装置具体包括固定于发动机缸体上的电机，以及连接于该电机的动力输出端的减速机构。减速机构的动力输出端与偏心轴7传动相连，以实现对偏心轴7的驱动，且需要说明的是，优选的，上述减速机构可为采用谐波减速器，或者，该减速机构也可视情形而采用两级减速结构，但其中的一级减速结构仍为采用谐波减速器。
而作为一种具体的实施方式，以上述减速机构采用两级减速结构为例，此时，结合于图2中所示的，该减速机构整体结构上包括谐波减速器，传动连接于谐波减速器的动力输出端的输出轴15，以及与谐波减速器的动力输入端传动连接的前级减速单元，该前级减速单元即与上述电机传动连接，并构成电机12的转动驱使力向谐波减速器的传递，且因前级减速单元的传动，而使电机12的转动轴线与输出轴的轴线平行设置。
为了提高传动平稳性，本实施例的前级减速单元例如可采用齿轮减速机构，该齿 轮减速机构具体包括固连于电机12转动轴21上的主动齿轮16，以及与主动齿轮16啮合、并固连于谐波减速器的动力输入端的从动齿轮20。通过利用齿轮减速机构构成前级减速单元，能够减小本减速传动机构的整体体积。而需要说明的是，前级减速单元除了采用齿轮减速机构，也可采用链条减速机构或皮带减速机构，其于该减速传动机构中的设置方式与齿轮减速机构的设置方式相同。
本实施例的谐波减速器的具体结构可参照现有技术，在具体构成上，其主要包括与外部构件连接的谐波减速器钢轮14，位于谐波减速器钢轮14内、并与谐波减速器钢轮14件啮合连接的谐波减速器柔轮18，以及于谐波减速器柔轮18内的具有输入轴的谐波减速器发生器19，该输入轴即与上述的从动齿轮10固连，而谐波减速器柔轮18即与前述的输出轴15传动连接。
具体而言，于谐波减速器钢轮14靠近于前级减速单元的一侧固连有供电机12装设的壳体13。为了避免灰尘杂质影响传动效果，主动齿轮16和从动齿轮20内置于壳体13中。另外，基于谐波减速器发生器19的现有结构，输入轴具体可为采用螺接、焊接或过盈压装等方式固连于谐波减速器发生器19上。此外，为实现谐波减速器柔轮18与输出轴15之间的传动连接，于输出轴15一侧设有固定于谐波减速器钢轮14上的轴承单元17。
本实施例的轴承单元17的结构与现有结构类似，由图2中所示，其具体包括与谐波减速器钢轮14固连、以保持静止不动的外圈组件171，以及经由滚动组件而转动嵌装于外圈组件171内的内圈组件172。前述的输出轴15即固连于内圈组件172上，同时，内圈组件172也与谐波减速器柔轮18构成固连，以承接谐波减速器柔轮18的驱使而转动，进而驱使输出轴15转动，而实现电机12动力的输出。
除此之外，本实施例为了提高传动性能，于壳体13、谐波减速器钢轮14及轴承单元17之间围构形成有储油腔，并于谐波减速器钢轮14上开设有以向储油腔中注油的润滑油孔。通过设置储油腔，可保证本减速传动机构的整体密封性，从而能够提高本减速传动机构的传动效果。此外，为了进一步提高密封效果，于壳体13与电机12之间，以及壳体13与谐波减速器钢轮14之间均设置有密封结构，该密封结构具体可为分别夹置于壳体13与电机12之间，以及壳体13与谐波减速器钢轮14之间的密封垫，或为卡装于两者其一上的密封圈。
本实施例中，前述从动部10中的相位调节器与偏心轴驱动装置中的电机均电联接于发动机控制单元，以由发动机控制单元控制而进行相应的动作反应。
其中，如图3中所示的，对于本实施例的冲程可变的可变压缩比机构，当通过电机驱使偏心轴7转动时，摆动连杆6的角度发生变化，推动驱动连杆5上下移动，使调节连杆3发生旋转。调节连杆3的旋转带动执连杆2上下移动，使活塞1的上止点位置上下改变ΔT，燃烧室的容积由之发生改变，从而可导致压缩比的改变。当然，在偏心轴7转动时，除了活塞1的上止点位置会发生变化，如图4所示的，活塞1的下止点的位置亦同样会相应的发生上、下变化ΔD。
本实施例为了便于描述，对于前述的偏心轴7转动的相位可用“β”进行表示，而在电机驱动下的偏心轴7的两个限位相位则具体的可分别由“β1”和“β2”进行表示。此时，本实施例中例如β1可为34°，而β2则可为-21°，偏心轴7即于此两个相位之间往复转动。
除了由控制偏心轴7的转动进行发动机压缩比的改变，本实施例活塞1在缸筒中上下往复运动，通过执行连杆2、调节连杆3可驱动曲轴4旋转。曲轴4每个工作循环转两圈，活塞1上下运动四次并分别为进气行程、压缩行程、膨胀行程和排气行程。在曲轴4的驱使下，控制轴9转动时，在控制偏心轮的带动下，随动连杆8推动摆动连杆摆动6，摆动连杆6推动驱动连杆5，使调节连杆3旋转一定的角度，调节连杆3旋转通过执行连杆2推动活塞1，即可改变活塞1上下止点的位置。
控制轴9每工作循环中转一圈，活塞1的位置进行高-中-低-中-高的循环变化，活塞1的高、低位置，对应不同上、下止点，且活塞1上、下止点的变化，会使压缩和膨胀行程、也即活塞1的冲程发生变化。由于压缩比＝(燃烧室容积+压缩行程*缸径^2*π/4)/燃烧室容积，膨胀比＝(燃烧室容积+膨胀行程*缸径^2*π/4)/燃烧室容积，从而便能够使发动机的压缩比与膨胀比之间的关系发生改变。
具体在针对于发动机运行的控制上，为便于描述，控制轴9与曲轴4之间的相位可由“αp”表示，其对于不同的相位值可通过在“αp”后添加不同的阿拉伯数字进行区别。
由此，本实施例在发动机运行时，可控制控制轴9与曲轴4之间的相位αp1为90°～150°，此时如图5中所示，进气下止点D1与膨胀下止点D1’相同，排气上止点T1低于压缩上止点T1’，进气行程LI1、排气行程LE1小于膨胀行程LD1、压缩行程LC1，压缩比等于膨胀比。
或者，也可在发动机运行时，控制控制轴9与曲轴4之间的相位αp2为180°～250°，此时如图6中所示，进气下止点D2高于膨胀下止点D2’，排气上止点T2与压缩 上止点T2’相同，进气行程LI2、压缩行程LC2小于膨胀行程LD2、排气行程LE2，压缩比小于膨胀比。
或者，还可在发动机运行时，控制控制轴9与曲轴4之间的相位αp3为270°～330°，此时如图7中所示的，进气下止点D3与膨胀下止点D3’相同，排气上止点T3高于压缩上止点T3’，进气行程LI3、排气行程LE3大于膨胀行程LD3、压缩行程LC3，压缩比等于膨胀比。
或者，在发动机运行时亦可控制控制轴9与曲轴4之间的相位αp4为0°～60°，此时如图8中所示，进气下止点D4低于膨胀下止点D4’，排气上止点T4与压缩上止点T4’相同，进气行程LI4、压缩行程LC4大于膨胀行程LD4、排气行程LE4，压缩比大于膨胀比。
而对于上述由不同的“αp”值区间所确定的发动机运行情形，本实施例需要说明的是，在发动机运行的同时通过控制偏心轴7于其两个限位相位间、也即β1-β2之间转动，也能够使得发动机的压缩比与膨胀比同步增加或减小。
具体来讲，结合于图1和图9所示的，当偏心轴7的角度由限位相位β1(34°)调整为限位相位β2(-21°)时，摆动连杆6的角度随之发生改变。以控制轴9与曲轴4之间的相位为αp1时为例，偏心轴7逆时针旋转，带动摆动连杆6逆时针旋转，同时随动连杆8顺时针旋转，角度发生改变。摆动连杆6将驱动连杆5上推，驱动连杆5推动调节连杆3逆时针旋转，执行连杆2下移，拉动活塞1位置向下移动，活塞1下止点由D1变为D5，下降ΔD，活塞1上止点由T1变为T5，下降ΔT。但压缩比与膨胀比同时减小，活塞四个行程(LI1、LC1、LD1、LE1)几乎不变。
而当偏心轴7的角度由限位相位β2(-21°)调整为限位相位β1(34°)时，摆动连杆6的角度随之发生改变。仍以控制轴9与曲轴4的相位为αp1时为例，同样可参见图1与图9所示，偏心轴7顺时针旋转，带动摆动连杆6顺时针旋转，同时随动连杆8逆时针旋转，角度发生改变。摆动连杆6将驱动连杆5下拉，驱动连杆5拉动调节连杆3顺时针旋转，执行连杆2上移，推动活塞1位置向上移动，活塞1下止点由D5变为D1，上升ΔD，活塞1上止点由T5变为T1，上升ΔT。压缩比与膨胀比同时增加，但活塞四个行程(LI1、LC1、LD1、LE1)几乎不变。
在控制轴9与曲轴4之间的相位αp为其他角度时，效果与上述相同。
本实施例中通过从动部10中的相位调节器对控制轴9相位的调整，可实现上述的压缩比大于膨胀比、压缩比小于膨胀比，以及压缩比等于膨胀比等不同的工作状态。当 然，除了这几种状态，通过相位调节器的调节，根据需要一般还能够实现上述任意两种状态之间的过渡状态，以可适应发动机的更多工况。
此外，对于本实施例的冲程可变的可变压缩比机构，在发动机正常工作中可为采用阿特金森循环模式，此时，可如图10中所示的，为控制控制轴9与曲轴4之间的相位为αp2(180°～250°)，以使发动机的膨胀比大于压缩比，且在运行中通过控制偏心轴7于其两限位相位间的转动，使得随发动机负荷的升高令发动机的膨胀比和压缩比减小，或是随发动机负荷的降低使发动机的压缩比和膨胀比增加。由此不仅可改善发动机效率，也可在发动机负荷高时抑制爆震的产生。
具体而言，对于该阿特金森循环模式，节气门开度较小时，发动机处于低负荷状态，偏心轴7调整至β1，活塞1排气上止点位置T2几乎等于压缩上止点T2’位置，进气下止点D2位置高于膨胀下止点D2’的位置，进气行程LI2、压缩行程LC2小于膨胀行程LD2、排气行程LE2。此时活塞1的上止点T6/T6’位置高，压缩比、膨胀比较高，由于膨胀行程长，膨胀比大于压缩比。活塞1膨胀行程长，做功时间长，可将更多的燃烧产生的气体压力转换为曲轴4的动力，进而可改善气缸内气体的做功效率，降低油耗。同时，压缩比大，点火时温度高，燃烧效率高，燃料燃烧也更充分，亦使得油耗更低，排放更清洁。
随节气门开度增加，发动机负荷升高进入缸内的气体增加，压缩终了时，缸内温度、压力进一步提高，燃料自发着火倾向提高，爆震倾向增加，可能会导致发动机零件损坏。此时，驱动偏心轴7旋转，其相位随负荷增加逐渐调整至β2。随着摆动连杆6、驱动连杆5、调节连杆3、执行连杆2的共同作用，相对于β1，进气行程LI6、压缩行程LC6、膨胀行程LD6、排气行程LE6基本不变，活塞1的上下止点位置下降，上止点T6/T6’、下止点D6/D6’变为上止点T2/T2’、下止点D2/D2’。由于上止点位置下降，压缩比降低，点火时缸内气体温度下降，燃料自发燃烧的倾向减少，便可抑制爆震的产生。
但此时膨胀行程LD6仍较长，膨胀比大，活塞1做功效率仍然较高，而且由于缸内气体膨胀时间长，膨胀行程终了时气体温度低，便能够降低排温，以防止排气零件出现热损坏。发动机负荷越高，可使得偏心轴7的相位越接近β2，直至达到限位位置，反之，则可使偏心轴7的相位越接近β1。
当然，除了采用阿特金森循环，本实施例中的冲程可变的可变压缩比机构亦能够设置发动机正常运行时采用HCCI模式，此时，控制控制轴9与曲轴4之间的相位为α p1(90°～150°)，以使发动机的膨胀比与压缩比相同。而且通过控制偏心轴7于其两限位相位间的转动，也为随发动机负荷的升高而使发动机的膨胀比和压缩比减小，或者，随发动机负荷的降低使得发动机的压缩比和膨胀比增加。
详细来说，对于HCCI模式，当节气门开度较小时，发动机处于低负荷状态，将偏心轴7相位调整至β1，活塞1的排气上止点T1位置低于压缩上止点T1’位置，进气下止点D1位置几乎与膨胀下止点D1’位置相同，进气行程LI1、排气行程LE1小于膨胀行程LD1、压缩行程LC1。压缩行程LC1长，可获得较大压缩比，压缩终了时气缸内气体压力、温度较高。排气行程LE1短，排气上止点T1低，气缸内残余高温废气多。基于以上两点，可在点火时获得较高的缸内压力与温度，利于汽油压燃，而能够增加HCCI可实现的范围。
同时，活塞1的膨胀行程长，做功时间长，可将更多的燃烧产生的气体压力转换为曲轴4的动力，由此也可改善气缸内气体的做功效率，而降低油耗。
随着发动机负荷提高，增压器开始工作，进入气缸内的气体增加，压缩终了时缸内温度、压力过高，爆震倾向增加。此时偏心轴7的相位由β1向β2旋转，随着摆动连杆6、驱动连杆5、调节连杆3、执行连杆2的共同作用，活塞1的上、下止点下降，由上止点T1/T1’、下止点D1/D1’变为上止点T5/T5’、下止点D5/D5’，进气行程LI5、压缩行程LC5、膨胀行程LD5、排气行程LE5基本不变。由此，活塞1的上止点降低，压缩比下降，便可使上止点附近气体被压缩程度降低，温度、压力下降，燃料自发燃烧的倾向减少，从而能够抑制爆震的产生。
在发动机负荷越高时，同样的可使偏心轴7的相位越接近β2，直至达到限位位置，反之，亦为使得偏心轴7的相位越接近β1。
另外，除了前述的发动机正常运行时的不同的控制方式，本实施例在发动机启动时，则可控制控制轴9与曲轴4之间的相位为αp4(0°～60°)，以使发动机的膨胀比小于压缩比，并且也通过控制偏心轴7于其两限位相位间的转动，而随发动机温度的升高使发动机的膨胀比和压缩比减小。由此以改善发动机的启动性能。
其具体的，启动时通过控制轴9与曲轴4间的相位为αp4，活塞1的排气上止点几乎与压缩上止点相同，进气下止点低于膨胀下止点，进气行程LI4、压缩行程LC4大于膨胀行程LD4、排气行程LE4。发动机温度较低时，可将偏心轴7相位调整至β1，此时进气升程长，可使更多的新鲜空气进入气缸，并且压缩行程长，压缩比大，点火时气缸内气体温度、压力较高。从而可改善启动时的燃烧过程，提高怠速稳定性，使燃料 燃烧更充分，而减少有害气体排放。与此同时，也由于膨胀行程短，气体膨胀不充分，膨胀行程终了时温度较高，排气温度高，较之启动时排气温度低的普通发动机，亦可大大提高催化器起燃速度，而进一步改善启动时的排放性能。
随着启动温度的提升，发动机温度较高，燃烧趋于稳定，催化器已开始工作，此时过高的温度会带来零件热损坏问题。因此，可将偏心轴7相位逐渐由β1调整至β2。参见图11所示，随着摆动连杆6、驱动连杆5、调节连杆3、执行连杆2的共同作用，活塞1的上、下止点下降，由上止点T4/T4’、下止点D4/D4’变为上止点T7/T7’、下止点D7/D7’。活塞1的上止点下降，压缩比降低，点火时温度、压力下降，燃烧温度降低，从而便能够防止因气体温度过高造成零件损坏。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (15)

  1. 一种冲程可变的可变压缩比机构，其特征在于：该冲程可变的可变压缩比机构受控于发动机控制单元，以进行发动机活塞冲程及压缩比的调节，且所述冲程可变的可变压缩比机构包括滑动设于发动机缸体中的活塞(1)，转动设于所述发动机缸体中的曲轴(4)和具有调节偏心轮的偏心轴(7)，以及转动设于所述曲轴(4)的曲柄上的调节连杆(3)，铰接于所述调节连杆(3)的一端与所述活塞(1)之间的执行连杆(2)，和铰接于所述调节连杆(3)的另一端的驱动连杆(5)；还包括：
    摆动连杆(6)，转动套装于所述调节偏心轮上，且所述摆动连杆(6)的一端与所述驱动连杆(5)铰接相连；
    控制轴(9)，转动设于所述发动机缸体中，于所述控制轴(9)上设有控制偏心轮，且所述控制轴(9)与所述曲轴(4)传动连接，并与所述曲轴(4)间的相位可调设置；
    随动连杆(8)，一端转动套装于所述控制偏心轮上，另一端与所述摆动连杆(6)铰接相连；
    偏心轴驱动装置，相对于所述发动机缸体固定设置，并与所述偏心轴(7)传动连接，以能够驱使所述偏心轴(7)于两限位相位间转动。
  2. 根据权利要求1所述的冲程可变的可变压缩比机构，其特征在于：于所述控制轴(9)上装设有具有相位调节器的从动部(10)，对应于所述从动部(10)，于所述曲轴(4)上装设有与所述从动部(10)传动连接以驱使所述从动部(10)随所述曲轴(4)转动的主动部(11)。
  3. 根据权利要求2所述的冲程可变的可变压缩比机构，其特征在于：所述主动部(11)与所述从动部(10)间由啮合设置的齿轮结构传动，或者，所述主动部(11)与所述从动部(10)通过连接设于两者之间的链条或皮带传动。
  4. 根据权利要求1所述的冲程可变的可变压缩比机构，其特征在于：所述偏心轴驱动装置包括固定于所述发动机缸体上的电机，以及连接于所述电机动力输出端的减速机构，所述减速机构的动力输出端与所述偏心轴(7)传动相连。
  5. 根据权利要求4所述的冲程可变的可变压缩比机构，其特征在于：所述减速机构中至少有谐波减速器。
  6. 根据权利要求5所述的冲程可变的可变压缩比机构，其特征在于：所述减速机构包括所述谐波减速器，传动连接于所述谐波减速器的动力输出端的输出轴(15)，以及与所述谐波减速器的动力输入端传动连接的前级减速单元，所述前级减速单元与所述电机传动连接，并构成所述电机的转动驱使力向所述谐波减速器的传递，且因所述前级减速单元的传动，而使所述电机的转动轴线与所述输出轴(15)的轴线平行设置。
  7. 根据权利要求6所述的冲程可变的可变压缩比机构，其特征在于：所述前级减速单元为齿轮减速机构、链条减速机构及皮带减速机构中的一种。
  8. 根据权利要求6所述的冲程可变的可变压缩比机构，其特征在于：所述谐波减速器包括用于与外部构件连接的谐波减速器钢轮(14)，位于所述谐波减速器钢轮(14)内并与所述谐波减速器钢轮(14)间啮合连接的谐波减速器柔轮(18)，以及设于所述谐波减速器柔轮(18)内的具有输入轴的谐波减速器波发生器；所述输入轴与所述前级减速单元传动连接，所述输出轴(15)和所述谐波减速器柔轮(18)传动连接。
  9. 根据权利要求8所述的冲程可变的可变压缩比机构，其特征在于：于所述谐波减速器钢轮(14)的靠近于所述前级减速单元的一侧固连有供所述外部旋转动力源装设的壳体(13)，且所述前级减速单元内置于所述壳体(13)中。
  10. 根据权利要求9所述的冲程可变的可变压缩比机构，其特征在于：于所述输出轴(15)一侧设有固定于所述谐波减速器钢轮(14)上的轴承单元(17)，所述轴承单元(17)包括与所述谐波减速器钢轮(14)固定连接的外圈组件(171)，以及经由滚动组件而转动嵌装于所述外圈组件(171)内的内圈组件(172)；所述谐波减速器柔轮(18)与所述内圈组件(172)传动连接，所述输出轴(15)固连在所述内圈组件(172)上。
  11. 基于权利要求1至10中任一项所述的冲程可变的可变压缩比机构的控制方法，其特征在于，该控制方法包括：
    于发动机运行时，控制所述控制轴(9)与所述曲轴(4)之间的相位为0°～60°，而使所述发动机的压缩比大于膨胀比；或者，
    于发动机运行时，控制所述控制轴(9)与所述曲轴(4)之间的相位为180°～250°，而使所述发动机的压缩比小于膨胀比；或者，
    于发动机运行时，控制所述控制轴(9)与所述曲轴(4)之间的相位为90°～150°或270°～330°，而使所述发动机的压缩比与膨胀比相同。
  12. 根据权利要求11所述的冲程可变的可变压缩比机构的控制方法，其特征在于，该控制方法还包括：
    于所述发动机运行时，控制所述偏心轴(7)于两所述限位相位间转动，而使所述发动机的压缩比与膨胀比同步增加或减小。
  13. 根据权利要求11所述的冲程可变的可变压缩比机构的控制方法，其特征在于，该控制方法还包括：
    或者，于所述发动机运行时，采用阿特金森循环模式，并控制所述控制轴(9)与所述曲轴(4)之间的相位为180°～250°，使所述发动机的膨胀比大于压缩比；且通过控制所述偏心轴(7)于两所述限位相位间的转动，而随发动机负荷的升高使所述发动机的膨胀比和压缩比减小，以及随发动机负荷的降低使所述发动机的压缩比和膨胀比增加。
  14. 根据权利要求11所述的冲程可变的可变压缩比机构的控制方法，其特征在于，该控制方法还包括：
    或者，于所述发动机运行时，采用HCCI模式，并控制所述控制轴(9)与所述曲轴(4)之间的相位为90°～150°，使所述发动机的膨胀比与压缩比相同；且通过控制所述偏心轴(7)于两所述限位相位间的转动，而随发动机负荷的升高使所述发动机的膨胀比和压缩比减小，以及随发动机负荷的降低使所述发动机的压缩比和膨胀比增加。
  15. 根据权利要求11所述的冲程可变的可变压缩比机构的控制方法，其特征在于，该控制方法还包括：
    于所述发动机启动时，控制所述控制轴(9)与所述曲轴(4)之间的相位为0°～60°，使所述发动机的膨胀比小于压缩比；且通过控制所述偏心轴(7)于两所述限位相位间的转动，而随发动机温度的升高使所述发动机的膨胀比和压缩比减小。
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