Toyota’s sticky gas pedal, part 1

05Feb10

The president of Toyota today apologized for the automaker’s quality problems that have led to the recall of more than nine million cars around the world and promised to soon announce steps that would address them.

Akio Toyoda, grandson of Toyota’s founder, took personal responsibility for the problems and vowed Toyota will do its utmost to regain the trust of its customers.
Prominent among the safety problems that have hounded Toyota in the last few months are its accelerator pedals that have been reported to stick. Last month, a total of 4.5 million vehicles representing eight models were recalled to fix this problem.
…………………………………………………………………………………………………………………………………..

INTERACTIVE: GAPS IN THE DRUG APPROVAL PROCESS

………………………………………………………………………………………………………………………………….

Missing in the news coverage of Toyota’s quality woes are the exact details of the gas pedal problem – why does it get stuck, what causes it to stick, what parts are involved and which one is malfunctioning, and in what stage of the process does the problem occur?

Visual Storyteller will try to make sense of the mechanics involved and present the details that matter to millions of people in an information graphic. And we will do it by starting with what we already know and work from there.

What we know
1. The gas pedal unit is designed to allow a certain amount of friction – referred to as hysteresis – between “teeth” that come in contact with each other during normal operation. Friction works in conjunction with spring pressure, a kind of counterbalancing force that returns the pedal to its original positon. This design makes the actual effort of stepping on the pedal less tiring for the driver.
2. The critical point here is the amount of friction allowed so that the pedal returns as soon as pressure is reduced, or removed, as is the case when a driver’s foot is taken off the pedal. It is established that the relationship between the spring pressure and built-in friction must be consistent.
3. According to Toyota, pedals made by Chinese parts maker CTS have not been able to maintain stability between friction and pressure. With the CTS pedals, friction can increase over time due to wear or condensation, or both. Here is when friction becomes greater than the pressure from the return spring, causing the pedal to slow down on the return motion, return in an uneven path, or not return at all to its original position.

In real life terms, here is what happens: A driver steps on the gas. This action squeezes the spring in the block and allows the “teeth” to come in contact inside the pedal unit. When the driver lets go of the pedal, the spring action kicks in but its force is overpowered by the friction, hence the pedal stays in a stuck position. The car  does not slow down , or does not stop at all.

In our next post, Part 2, we will diagram the pedal assembly in greater detail and show the interplay between friction and spring action.

……………………………………………………………………………………………………………………..

Also in this blog:
A biodiesel project
The world’s richest oil deposit
Treating gunshot wounds
The promise of E-paper
Recalling the Nimrod air crash in Lake Ontario

……………………………………………………………………………………………………………………………………

Advertisements


No Responses Yet to “Toyota’s sticky gas pedal, part 1”

  1. Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: