UNIT 2
ENGINE MECHANICAL
TEXT B
Valve Systems
PROFESSIONAL ENGLISH
UNIT 2
ENGINE MECHANICAL
TEXT B
Valve Systems
Operation of Valve System
VVT— Toyota's Continuously Variable Valve Timing
VTEC— Honda Variable Valve Timing and Lift Electronic Control
MIVEC— Mitsubishi Innovative Valve timing Electronic Control
Electronic Valve Control System
Smart Valves
本次课学习内容本次课学习目标
掌握可变气门定时机构主要部件的英文名称
掌握可变气门定时机构的基本原理
掌握常用术语（ phrases and
expressions）
了解相关术语（ related terms）
NEW WORDS
bump [b?mp]n.撞击，（因撞击而起的）肿块； v.碰，撞，
颠簸
cam [k?m]n.凸轮
lobe [loub]n.凸起
integral ['intigr?l]a.完整的，整体的，积分的
stem [stem]n.杆，茎
powertrain ['pau?trein]n.动力系统，动力装置，传动系统
dyno ['dainou]n.=dynamometer测功机，测力计
breathe [bri:e]v.呼吸，发出
certification [s?:tifi'kei∫?n]n.证明，鉴定，检验证明书
compromise ['k?mpr?maiz]v,& n.妥协，折衷
essence ['esns] n.基本，本质，实质，精华，要素
pulley ['puli] n.滑轮，带轮
helical ['helik?l] a.螺旋状的
spline [splain] n.花键，方栓
spool [spu:l] n.线轴，卷轴；滑阀；线圈
mpg = mile per gallon（英里 /加仑）
actuator ['?ktjueit?] n.执行器，执行元件
strategy ['str?ti?i] n.策略，谋略
flexibility [fleks?'biliti] n.灵活性，柔性，适应性
eager ['i:g?] v.渴望着，热心于
multiplex ['m?tipleks] a.多元的，多重的，多样的； n.多路传输，多路通信
nominal ['n?min?l] a,有名无实的；极微小的；标定的，额定的
bus [b?s] n.总线
innovation [inou'vei∫?n] v.改进，革新，创新，新发明 [技术，方法 ]
residual [ri'zidju?l] a.剩余的，残余的
cam lobe 凸轮的凸起部分
valve stem 气门杆
variable valve timing（ VVT）可变气门定时
in essence 本质上，实质上
spool valve 滑阀
electronic valve control (EVC) 电子式气门控制
centralized system 集中系统
distributed system 分布系统
camless engine 无凸轮发动机
smart valve 智能气门
PHRASES AND EXPRESSIONS
Valve Systems
Operation of Valve System
You have seen that the intake valve must be opened for
the intake stroke,both valves must remain closed during the
compression and power strokes,and the exhaust valve
opens during the exhaust stroke,The designer must design a
device to open and close the valves at the proper times.
The shaft will have an egg-shaped bump called a cam
lobe,The cam lobe is machined as an integral part of the
shaft,This shaft is called a camshaft.
The distance the valve will be raised,how long it will stay
open,and how fast it opens and closes can all be controlled
by the height and shape of the lobe [1],
As you will see later,it is impractical to have the cam lobe
contact the end of the valve stem itself,You have placed the
camshaft some distance above the end of the valve stem.
When the camshaft is turn,the lobes will not even touch
the valve stem,The lifter is installed between the cam lobe
and the valve stem,The upper end rides on the lobe and
the lower end almost touches the valve stem,The lifter
slides up and down in a hole bored in the head metal that
separates the valve stem from the camshaft [2].
You have developed a method of opening and closing
the valves,The next problem is how and at what speed to
turn the camshafts,Each valve must be open for one
stroke,The intake valve is open during the intake stroke
and remains closed during the compression,power,and
exhaust strokes,This would indicate that the cam lobe
must turn fast enough to raise the valve every fourth stroke.
You can see that it takes one complete revolution of the
cam lobe for every four strokes of the piston.
Remember that four strokes of the piston require two
revolutions of the crankshaft,You can say that for every two
revolutions of the crankshaft,the camshaft must turn once,If
you are speaking of the speed of the camshaft,you can say that
the camshaft must turn at one-half crankshaft speed.
If the crankshaft is turning and the camshaft must turn at one-
half crankshaft speed,it seems logical to use the spinning
crankshaft to turn the camshaft,One very simple way to drive
the camshaft would be by means of gears and a belt,One gear
is fastened on the end of the crankshaft,and the other is
fastened on the end of the camshaft,The large camshaft gear
drives the smaller crankshaft gear through the belt.
If,for instance,the small gear on the crankshaft has 10 teeth
and the large gear on the camshaft has 20 teeth,the crankshaft
will turn the camshaft at exactly one-half crankshaft speed,
VVT-Toyota's Continuously Variable Valve Timing
The most significant and satisfying changes to the Lexus GS
line are in the area of powertrain,In the case of the GS300,
Lexus breathes new life into last year's 3.0L inline six,by
introducing VVT— continuously variable valve timing system,On
the dyno,VVT shows up as only five additional horsepower and
10 lb-ft of torque,But in the car it means fuel economy
improvements of 1.6 mpg,smoother idle,California TLEV
(transitional low-emissions vehicle) certification and zero-to-60
mph a half second quicker,
Toyota eliminates the compromise of conventional valve
timing with the introduction of VVT,By continuously varying
intake valve timing (up to 60 crank angle degrees),Toyota
optimizes low- to mid-speed torque,improves fuel economy and
lowers emissions without having a negative impact on idle.
In essence,the system controls valve overlap,which
means it can eliminate it completely for a glass smooth idle,
or maximize it to boost volumetric efficiency and reduce
pumping losses— this translates into power,economy and
cleaner running at all engine speeds.
The heart of the system is the intake cam pulley,which
consists of an inner and outer section,The inner portion is
fixed to the camshaft and nests inside the belt-driven outer
pulley via helical spline gears,An electronically controlled
hydraulic piston moves the pulley halves relative to one
another,causing the cam portion to rotate within the outer
pulley.
This rotation advances or retards intake valve timing,A
spool valve reacting to signals from the ECU controls
hydraulic pressure.
VTEC-Honda Variable Valve Timing and Lift Electronic Control
By designing a higher valve lift,wider valve-timing,and
larger valve diameter,it is possible to obtain a higher
volumetric efficiency to cope with higher output engine speeds,
The VTEC is used to improve volumetric efficiency from low
engine speed to high engine speed,With VTEC,the valve
timing and lift can be adjusted at low engine rotation to
increase torque and prevent air from being forced back through
the intake,
VTEC Layout
In Fig.2-3 the structure of the VTEC is shown,The engine
has one extra cam profile and rocker arm (mid rocker arm) for
high engine speed,The cam has 3 different profiles located at
the intake and exhaust of each cylinder,The center cam is
used exclusively for high speed and the 2 outside cams for low
speed.
The rocker arm assembly is composed of a mid rocker
arm with primary and secondary rocker arms on each side,
Inside the rocker arms are 2 hydraulic pistons,a stopper
pin,and a return spring,which make up the change over
mechanism.
The mid rocker arm has a lost motion spring so that the
valve operates smoothly at high speeds and also stops the
arm at low speeds.
The whole system is operated by a hydraulic actuator
which is controlled by the Engine-Control Unit (ECU).
1 Camshaft
2 Cam Lobe for Low
Speed Range
3 Cam Lobe for High
Speed Range
4 Primary Rocker Arm
5 Mid Rocker Arm
6 Secondary Rocker
Arm
7 Hydraulic Piston A
8 Hydraulic Piston B
9 Stopper Pin
10 Lost-motion Spring
11 Exhaust Valve
12 Intake Valve
Fig.2-3 VTEC System Construction
VTEC Operation
Fig.2-4 shows the VTEC mechanism while operating at low
engine speeds,In the low-speed mode the 3 rocker arms are
separated and use cams A & B only,At this time the mid
rocker arm is in contact with the high speed cam due to the
spring force in the lost motion mechanism,It is separated from
the primary and secondary rocker arm and thus is not
actuating the valves,Fig.2-5 shows the VTEC mechanism
while operating in the high speed mode,During high speed
engine operation the 3 rocker arms are connected and move
together due to the 2 hydraulic pistons which have moved over
due to increased hydraulic pressure.
Fig.2-4 Rocker Arm Operation (Low Speed Range)
Fig.2-5 Rocker Arm Operation (High Speed Range)
MIVEC— Mitsubishi Innovative Valve Timing Electronic
Control System
The MIVEC dual-intake valve camshaft enables changing
between low-speed and high-speed modes （ Fig.2-6）,
resulting in easy operation from low to high rpms,improving
the driving experience when starting from a stop light,
merging onto the freeway,or accelerating to overtake
another car,In pursuit of pure driving enjoyment,potentially
incompatible goals like fuel economy,environment-
friendliness,and clean driving have all been achieved.
Low-speed Mode
The difference in the dual-intake valve lift (low lift and
medium lift) and enhanced in-cylinder streaming further
stabilize combustion without compromising fuel economy,
emissions,and torque.
High-speed Mode
Extending the injection valve opening time and
expanding the valve lift range increases intake air mass
and achieves output close to best in class.
The Grandis is equipped with the 2.4L MIVEC and the
Colt is equipped with the 1.3 and 1.5L MIVEC [3].
Fig,2-6 Mitsubishi MIVEC
Electronic Valve Control System
An electronic valve control (EVC) system replaces the
mechanical camshaft,controlling each valve with actuators
for independent valve timing,The EVC system controls the
opening and closing time and lift amount of each intake and
exhaust valve with independent actuators on each valve,
Changing from a mechanical camshaft driven valve into
independently controlled actuator valves provides a huge
amount of flexibility in engine control strategy,Vehicles
utilizing EVC can realize several benefits including:
1) increases engine power and fuel economy.
2) allows centralized and distributed EVC systems to
perform at their full potential.
3) adapts to engines of varied cylinder counts.
With all of the improved efficiencies and consumer benefits,
auto manufacturers are eager to get their first EVC systems on
the road,The EVC system is targeted to operate in
temperatures up to 125℃,while the actuator is targeted to run
up to 6 000 r/min,The actuator can be controlled in a centralized
system with a high-speed multiplex bus (up to 10Mbps) or in a
distributed system with a nominal speed bus.
EVC systems must be compact in size,specifically the
actuators that must be small enough to fit in the engine space,A
vehicle that uses a 42V system is ideal for EVC because it
requires high voltage to control the valve actuators,and EVC is
targeted for V8 and V12 engines.
Smart Valves
Valeo is actively developing technology for reducing fuel
consumption and emissions with an engine cylinder-head design
that uses its Smart Valve Actuation (SVA) in place of
conventional mechanical operation of engine valves by the cam
belt,camshaft,and hydraulic cam followers [4],
SVA is the first of many innovations that Valeo intends to
actively develop and market to meet increasing demand for
better fuel economy and reduced pollution following its
acquisition of Johnson Controls’ Engine Electronics
Division [5],In a camless engine,each engine valve is
operated by an actuator mounted above the valve guides,
Each actuator is linked to an engine-mounted valve control
unit that ensures optimal positioning of all valves and
performs the power drive function.
By controlling residual gases,minimizing pumping losses,
and deactivating cylinders and valves,this technology can
reduce fuel consumption and pollutant emissions by 20%,
Consumers will benefit from enhanced performance from
increases in low-end engine torque,The SVA development
program is supported by several car manufacturers and is
scheduled for volume production in 2009.
小结
VVT
Toyota VVT
Continuously variable valve timing
Honda VTEC
Variable valve timing & lift
Mitsubishi MIVEC
Variable valve timing & lift
EVC
Smart Valves
作业
熟记相关专业词汇
P40 EXERCIES Ⅰ to Ⅲ
ENGINE MECHANICAL
TEXT B
Valve Systems
PROFESSIONAL ENGLISH
UNIT 2
ENGINE MECHANICAL
TEXT B
Valve Systems
Operation of Valve System
VVT— Toyota's Continuously Variable Valve Timing
VTEC— Honda Variable Valve Timing and Lift Electronic Control
MIVEC— Mitsubishi Innovative Valve timing Electronic Control
Electronic Valve Control System
Smart Valves
本次课学习内容本次课学习目标
掌握可变气门定时机构主要部件的英文名称
掌握可变气门定时机构的基本原理
掌握常用术语（ phrases and
expressions）
了解相关术语（ related terms）
NEW WORDS
bump [b?mp]n.撞击，（因撞击而起的）肿块； v.碰，撞，
颠簸
cam [k?m]n.凸轮
lobe [loub]n.凸起
integral ['intigr?l]a.完整的，整体的，积分的
stem [stem]n.杆，茎
powertrain ['pau?trein]n.动力系统，动力装置，传动系统
dyno ['dainou]n.=dynamometer测功机，测力计
breathe [bri:e]v.呼吸，发出
certification [s?:tifi'kei∫?n]n.证明，鉴定，检验证明书
compromise ['k?mpr?maiz]v,& n.妥协，折衷
essence ['esns] n.基本，本质，实质，精华，要素
pulley ['puli] n.滑轮，带轮
helical ['helik?l] a.螺旋状的
spline [splain] n.花键，方栓
spool [spu:l] n.线轴，卷轴；滑阀；线圈
mpg = mile per gallon（英里 /加仑）
actuator ['?ktjueit?] n.执行器，执行元件
strategy ['str?ti?i] n.策略，谋略
flexibility [fleks?'biliti] n.灵活性，柔性，适应性
eager ['i:g?] v.渴望着，热心于
multiplex ['m?tipleks] a.多元的，多重的，多样的； n.多路传输，多路通信
nominal ['n?min?l] a,有名无实的；极微小的；标定的，额定的
bus [b?s] n.总线
innovation [inou'vei∫?n] v.改进，革新，创新，新发明 [技术，方法 ]
residual [ri'zidju?l] a.剩余的，残余的
cam lobe 凸轮的凸起部分
valve stem 气门杆
variable valve timing（ VVT）可变气门定时
in essence 本质上，实质上
spool valve 滑阀
electronic valve control (EVC) 电子式气门控制
centralized system 集中系统
distributed system 分布系统
camless engine 无凸轮发动机
smart valve 智能气门
PHRASES AND EXPRESSIONS
Valve Systems
Operation of Valve System
You have seen that the intake valve must be opened for
the intake stroke,both valves must remain closed during the
compression and power strokes,and the exhaust valve
opens during the exhaust stroke,The designer must design a
device to open and close the valves at the proper times.
The shaft will have an egg-shaped bump called a cam
lobe,The cam lobe is machined as an integral part of the
shaft,This shaft is called a camshaft.
The distance the valve will be raised,how long it will stay
open,and how fast it opens and closes can all be controlled
by the height and shape of the lobe [1],
As you will see later,it is impractical to have the cam lobe
contact the end of the valve stem itself,You have placed the
camshaft some distance above the end of the valve stem.
When the camshaft is turn,the lobes will not even touch
the valve stem,The lifter is installed between the cam lobe
and the valve stem,The upper end rides on the lobe and
the lower end almost touches the valve stem,The lifter
slides up and down in a hole bored in the head metal that
separates the valve stem from the camshaft [2].
You have developed a method of opening and closing
the valves,The next problem is how and at what speed to
turn the camshafts,Each valve must be open for one
stroke,The intake valve is open during the intake stroke
and remains closed during the compression,power,and
exhaust strokes,This would indicate that the cam lobe
must turn fast enough to raise the valve every fourth stroke.
You can see that it takes one complete revolution of the
cam lobe for every four strokes of the piston.
Remember that four strokes of the piston require two
revolutions of the crankshaft,You can say that for every two
revolutions of the crankshaft,the camshaft must turn once,If
you are speaking of the speed of the camshaft,you can say that
the camshaft must turn at one-half crankshaft speed.
If the crankshaft is turning and the camshaft must turn at one-
half crankshaft speed,it seems logical to use the spinning
crankshaft to turn the camshaft,One very simple way to drive
the camshaft would be by means of gears and a belt,One gear
is fastened on the end of the crankshaft,and the other is
fastened on the end of the camshaft,The large camshaft gear
drives the smaller crankshaft gear through the belt.
If,for instance,the small gear on the crankshaft has 10 teeth
and the large gear on the camshaft has 20 teeth,the crankshaft
will turn the camshaft at exactly one-half crankshaft speed,
VVT-Toyota's Continuously Variable Valve Timing
The most significant and satisfying changes to the Lexus GS
line are in the area of powertrain,In the case of the GS300,
Lexus breathes new life into last year's 3.0L inline six,by
introducing VVT— continuously variable valve timing system,On
the dyno,VVT shows up as only five additional horsepower and
10 lb-ft of torque,But in the car it means fuel economy
improvements of 1.6 mpg,smoother idle,California TLEV
(transitional low-emissions vehicle) certification and zero-to-60
mph a half second quicker,
Toyota eliminates the compromise of conventional valve
timing with the introduction of VVT,By continuously varying
intake valve timing (up to 60 crank angle degrees),Toyota
optimizes low- to mid-speed torque,improves fuel economy and
lowers emissions without having a negative impact on idle.
In essence,the system controls valve overlap,which
means it can eliminate it completely for a glass smooth idle,
or maximize it to boost volumetric efficiency and reduce
pumping losses— this translates into power,economy and
cleaner running at all engine speeds.
The heart of the system is the intake cam pulley,which
consists of an inner and outer section,The inner portion is
fixed to the camshaft and nests inside the belt-driven outer
pulley via helical spline gears,An electronically controlled
hydraulic piston moves the pulley halves relative to one
another,causing the cam portion to rotate within the outer
pulley.
This rotation advances or retards intake valve timing,A
spool valve reacting to signals from the ECU controls
hydraulic pressure.
VTEC-Honda Variable Valve Timing and Lift Electronic Control
By designing a higher valve lift,wider valve-timing,and
larger valve diameter,it is possible to obtain a higher
volumetric efficiency to cope with higher output engine speeds,
The VTEC is used to improve volumetric efficiency from low
engine speed to high engine speed,With VTEC,the valve
timing and lift can be adjusted at low engine rotation to
increase torque and prevent air from being forced back through
the intake,
VTEC Layout
In Fig.2-3 the structure of the VTEC is shown,The engine
has one extra cam profile and rocker arm (mid rocker arm) for
high engine speed,The cam has 3 different profiles located at
the intake and exhaust of each cylinder,The center cam is
used exclusively for high speed and the 2 outside cams for low
speed.
The rocker arm assembly is composed of a mid rocker
arm with primary and secondary rocker arms on each side,
Inside the rocker arms are 2 hydraulic pistons,a stopper
pin,and a return spring,which make up the change over
mechanism.
The mid rocker arm has a lost motion spring so that the
valve operates smoothly at high speeds and also stops the
arm at low speeds.
The whole system is operated by a hydraulic actuator
which is controlled by the Engine-Control Unit (ECU).
1 Camshaft
2 Cam Lobe for Low
Speed Range
3 Cam Lobe for High
Speed Range
4 Primary Rocker Arm
5 Mid Rocker Arm
6 Secondary Rocker
Arm
7 Hydraulic Piston A
8 Hydraulic Piston B
9 Stopper Pin
10 Lost-motion Spring
11 Exhaust Valve
12 Intake Valve
Fig.2-3 VTEC System Construction
VTEC Operation
Fig.2-4 shows the VTEC mechanism while operating at low
engine speeds,In the low-speed mode the 3 rocker arms are
separated and use cams A & B only,At this time the mid
rocker arm is in contact with the high speed cam due to the
spring force in the lost motion mechanism,It is separated from
the primary and secondary rocker arm and thus is not
actuating the valves,Fig.2-5 shows the VTEC mechanism
while operating in the high speed mode,During high speed
engine operation the 3 rocker arms are connected and move
together due to the 2 hydraulic pistons which have moved over
due to increased hydraulic pressure.
Fig.2-4 Rocker Arm Operation (Low Speed Range)
Fig.2-5 Rocker Arm Operation (High Speed Range)
MIVEC— Mitsubishi Innovative Valve Timing Electronic
Control System
The MIVEC dual-intake valve camshaft enables changing
between low-speed and high-speed modes （ Fig.2-6）,
resulting in easy operation from low to high rpms,improving
the driving experience when starting from a stop light,
merging onto the freeway,or accelerating to overtake
another car,In pursuit of pure driving enjoyment,potentially
incompatible goals like fuel economy,environment-
friendliness,and clean driving have all been achieved.
Low-speed Mode
The difference in the dual-intake valve lift (low lift and
medium lift) and enhanced in-cylinder streaming further
stabilize combustion without compromising fuel economy,
emissions,and torque.
High-speed Mode
Extending the injection valve opening time and
expanding the valve lift range increases intake air mass
and achieves output close to best in class.
The Grandis is equipped with the 2.4L MIVEC and the
Colt is equipped with the 1.3 and 1.5L MIVEC [3].
Fig,2-6 Mitsubishi MIVEC
Electronic Valve Control System
An electronic valve control (EVC) system replaces the
mechanical camshaft,controlling each valve with actuators
for independent valve timing,The EVC system controls the
opening and closing time and lift amount of each intake and
exhaust valve with independent actuators on each valve,
Changing from a mechanical camshaft driven valve into
independently controlled actuator valves provides a huge
amount of flexibility in engine control strategy,Vehicles
utilizing EVC can realize several benefits including:
1) increases engine power and fuel economy.
2) allows centralized and distributed EVC systems to
perform at their full potential.
3) adapts to engines of varied cylinder counts.
With all of the improved efficiencies and consumer benefits,
auto manufacturers are eager to get their first EVC systems on
the road,The EVC system is targeted to operate in
temperatures up to 125℃,while the actuator is targeted to run
up to 6 000 r/min,The actuator can be controlled in a centralized
system with a high-speed multiplex bus (up to 10Mbps) or in a
distributed system with a nominal speed bus.
EVC systems must be compact in size,specifically the
actuators that must be small enough to fit in the engine space,A
vehicle that uses a 42V system is ideal for EVC because it
requires high voltage to control the valve actuators,and EVC is
targeted for V8 and V12 engines.
Smart Valves
Valeo is actively developing technology for reducing fuel
consumption and emissions with an engine cylinder-head design
that uses its Smart Valve Actuation (SVA) in place of
conventional mechanical operation of engine valves by the cam
belt,camshaft,and hydraulic cam followers [4],
SVA is the first of many innovations that Valeo intends to
actively develop and market to meet increasing demand for
better fuel economy and reduced pollution following its
acquisition of Johnson Controls’ Engine Electronics
Division [5],In a camless engine,each engine valve is
operated by an actuator mounted above the valve guides,
Each actuator is linked to an engine-mounted valve control
unit that ensures optimal positioning of all valves and
performs the power drive function.
By controlling residual gases,minimizing pumping losses,
and deactivating cylinders and valves,this technology can
reduce fuel consumption and pollutant emissions by 20%,
Consumers will benefit from enhanced performance from
increases in low-end engine torque,The SVA development
program is supported by several car manufacturers and is
scheduled for volume production in 2009.
小结
VVT
Toyota VVT
Continuously variable valve timing
Honda VTEC
Variable valve timing & lift
Mitsubishi MIVEC
Variable valve timing & lift
EVC
Smart Valves
作业
熟记相关专业词汇
P40 EXERCIES Ⅰ to Ⅲ
