Transcript Slide 1

Automatic Transmissions
and Transaxles
SIXTH EDITION
CHAPTER
11
Continuously
Variable
Transmissions
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–1a
A belt and pulley CVT uses variable-width pulleys to provide an infinite number of speed ratios.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–1b
A belt and pulley CVT uses variable-width pulleys to provide an infinite number of speed ratios.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–2 Engine speed and vehicle speed of a CVT transaxle compared to a typical six-speed conventional
automatic transaxle.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
Frequently Asked Question
What Is It Like to Drive a Vehicle Equipped with CVT?
For most people, driving a vehicle equipped with a
continuously variable transmission (CVT) is the same
as driving the vehicle equipped with a conventional
automatic transmission/transaxle. The vehicle creeps
slightly when the brake is released and accelerates
normally when the throttle is opened. Because no
shifts occur, the first thing the driver and passenger
notice is that it is very smooth. If the vehicle is
equipped with a tachometer, the driver may notice
that the engine speed increases when first
accelerating and often remains higher until the
vehicle speed increases. During periods of rapid
acceleration, the engine speed may be close to its
maximum and thereby create noise and vibration
often not experienced in a similar vehicle. Because
the vehicle speed slowly catches up to the engine
speed, this effect is often referred to as the “rubber
band effect” and is most noticeable only during
periods of rapid acceleration. However, the fuel
economy improvement of a CVT compared to a
conventional automatic transmission makes the
slight difference a reasonable trade-off.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–3 The drive pulley is wide while the driven pulley is narrow for a low ratio vehicle start (left). The
ratio changes by making the drive pulley narrow and the driven pulley wider.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–4
A Typical push-type CVT belt construction.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
Chart 11–1 Vehicles that use a CVT transaxle,
separated by type: either push-type (belt) or pulltype (chain). Check service information for the exact
years and types of transmissions used for each
model.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–5
The pull chain looks similar to a silent chain.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–6 Block diagram showing the relationship between the TCM, electrical actuators, valve body, and
hydraulic actuators for a CVT transmission.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–7 (a) The stepper motor and pulley ratio link with the CVT in low ratio. (b) The stepper motor has
extended, moving the ratio link and ratio control valve; this should cause the primary pulley to become narrower
to produce a higher ratio.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–8 Movement of either the stepper motor or primary floating sheave will move the ratio control
valve to add or remove fluid from the primary pulley. The secondary valve maintains the necessary pulley
pressure on the drive belt.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–9
Honda CVT power flow in park (P) and neutral (N).
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–10
Honda CVT operation in drive (D) or low (L).
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–11
Location of the Honda CVT start clutch.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–12
The pressure tap locations as found on a Dodge Caliber CVT transaxle.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
FIGURE 11–13 Using the exact fluid recommended by the vehicle manufacturer is the preferred choice when
servicing a CVT transaxles.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
Warning:
The pressure can exceed 1,000 PSI (6,900 kPa)
and a leak from the tester could cause personal
injury. Always uses a high-pressure gauge and
follow the vehicle manufacturer’s recommended
procedures.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
Chart 11–2 Typical continuously variable
transmission (CVT) diagnostic trouble codes (DTCs)
and code description. Transmission-related DTCs are
usually P07XX or P08XX, where XX represents the
specific fault code.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved
Chart 11–2 (continued) Typical continuously
variable transmission (CVT) diagnostic trouble codes
(DTCs) and code description. Transmission-related
DTCs are usually P07XX or P08XX, where XX
represents the specific fault code.
Automatic Transmissions and Transaxles, 6e
James D. Halderman | Tom Birch
Copyright © 2015 by Pearson Education, Inc.
All Rights Reserved