Toyota Nation Forum banner
1 - 7 of 7 Posts

·
Super Moderator
Joined
·
9,394 Posts
Discussion Starter · #1 ·
Maybe this will be helpful to some:

BRAKE CONTROL SYSTEM 1. General
A brake management function, VDIM (Vehicle Dynamics Integrated Management), which delivers comprehensive vehicle movement control, is used.
An ECB (Electronically Controlled Brake System) is used. The brake control system is controlled by the skid control ECU.
2. VDIM (Vehicle Dynamics Integrated Management)
General The VDIM manages all functions, such as the ABS with EBD, the Brake Assist, the TRAC, and the VSC.
And is operated by the ECB (Electronically Controlled Brake System), which regulates brake fluid pressure. In addition, the regenerative brake cooperative control and power steering cooperative control functions are also available, thus allowing the VDIM to perform the comprehensive management.
Conventional brake control systems begin to control either the braking or motive force in order to stabilize the vehicle motion, when it becomes unstable due to loss of tire traction. In contrast, in order to maintain stable vehicle control, the VDIM commences controlling the brake, hybrid and steering systems in accordance with changes in balance before the vehicle becomes unstable. As a result, maintenance smooth vehicle control is achieved.
Conventional brake control systems manage all related functions, such as the ABS with EBD, the Brake Assist, the TRAC and the VSC, independently, according to the vehicle dynamics. In contrast, the VDIM provides smooth control by seamlessly integrating all brake control related functions.
Conventional Conventional brake control systems calculate vehicle motion based on signals transmitted by yaw rate
and deceleration sensors, the speed sensors and the steering sensor, and activates VSC systems when vehicles are determined to be skidding. If the driver brakes suddenly, brake control systems perform assisting control to stabilize the vehicle dynamics, by activating the ABS system when a locked wheel is detected, or by affecting the VSC system when skidding is detected.
VDIM The VDIM also calculates vehicle motion based on signals from the yaw rate and deceleration sensor,
speed sensors and steering sensor. When the calculations indicate that the vehicle is likely to skid, the VDIM begins vehicle control with the VSC function. In addition, if the driver brakes suddenly, the VDIM reduces vehicle instability to a minimum and assists in achieving optimum driving stability by seamlessly delivering a suitable combination of the VSC and ABS functions.
Regenerative Brake Cooperative Control

Controls hydraulic braking in order to recover electrical energy by utilizing the regenerative brake of the THS II as much as possible.

Power Steering Cooperative Control

Effects cooperative control with the EPS ECU in order to provide steering assist in accordance with the operating conditions of the vehicle.
This system electrically detects the operation information for the brake pedal and generates an appropriate amount of hydraulic brake.
Executes the hydraulic control of the brake control functions based on the VDIM.

Regenerative brake consists of a resistance force that is generated at the rotational axle in the reverse direction of the rotation of the generator (MG2) that is generating electricity. The greater the generated amperage (battery charging amperage), the greater will be the resistance force.
The drive axle and MG2 are joined mechanically. When the drive wheels rotate MG2 and cause it to operate as a generator, a regenerative brake force of MG2 is transmitted to the drive wheels. This force is controlled by the THS II, which controls the generation of electricity. The regenerative brake cooperative control does not rely solely on the braking force of the hydraulic brake system to supply the brake force required by the driver. Instead, by effecting cooperative control with the THS II, this control provides a joint braking force provided by the regenerative brake and the hydraulic brake. As a result, this control minimizes the loss of the kinetic energy associated with the normal hydraulic brake, and recovers this energy by converting it into electrical energy.
Apportioning of the Brake Force
The apportioning of the brake force between the hydraulic brake and the regenerative brake varies by the vehicle speed and time. The apportioning of the brake force between the hydraulic brake and the regenerative brake is accomplished by controlling the hydraulic brake so that the total brake force of the hydraulic brake and the regenerative brake matches the brake force required by the driver.
If the regenerative brake becomes inoperative due to a malfunction in the THS II, the brake system effects control so that the entire brake force required by the driver is supplied with the hydraulic brake system.
ECB (Electronically Controlled Brake System)
General In this system, the conventional brake booster portion has been discontinued. Instead, it consists of brake input, power supply, and hydraulic pressure control portions. During normal braking, the fluid pressure generated by the master cylinder does not directly actuate the wheel cylinders, but serves as a hydraulic pressure signal. Instead, the actual control pressure is obtained by regulating the fluid pressure of the hydraulic power source in the brake actuator, which actuates the wheel cylinders.
The ECB (Electronically Controlled Brake System) executes the hydraulic control of the ABS with EBD, brake assist, TRAC, and VSC function in accordance with information provided by the sensors and ECUs.
The power source backup unit is used as an auxiliary power source, to supply power to the brake system in a stable manner.

Stroke Simulator
The stroke simulator is mounted between the master cylinder and the brake actuator. The fluid pressure generated by the master cylinder is introduced to the stroke simulator through the built-in stroke simulator cut valve.
The stroke simulator generates a pedal stroke in accordance with the driver’s pedal effort during braking. Containing two types of coil springs with different spring constants, the stroke simulator provides pedal stroke characteristics in two stages in relation to the master cylinder pressure.

And this is why, boys and girls, you better NOT be trying to conventional bleed this system, with all it vlaves, accumulators, simulators, and what not:



 

·
Super Moderator
Joined
·
9,394 Posts
Discussion Starter · #3 ·
You REALLY need to find out if they were. As reason I posted this here is 2-fold.
1. some still believe bleeding the brakes is a he-hah DIY job (based on Autozone site), though Alldata, owned by Autozone, CLEARLY states very complex procedure for it.
2. some fella here had his car go nuts after a yahoo tech at dealership bled his brakes. Suspicion is - he didn't follow the proper procedure.
It's only $150 well spent, IMHO.
 

·
Reformed TDI'r
2008 Camty Hybrid
Joined
·
2 Posts
UKRKOZ,
So at what speed does the TCH actually start using its mechanical brakes (calipers and pads) to continue to slow the car down? Is it like at 20mph 10mph? Example: if you're at a speed of say 50, and the light a decent distance ahead turns yellow and red in front of you, and you start applying the brakes normally, I understand that the electric motor sort of acts like a vacuum or a braking system, also charging the batteries and uses all that tech and slows the car down for you without using the mechanical brakes at all (the calipers and the pads) but at some point the calipers and pads are used during that stop down to zero. Do you know at what speed it switches from the electric motor to the actual mechanical breaks?
 

·
Registered
Joined
·
368 Posts
At slow speeds, the regenerative braking becomes less effective and the car has to rely more on the mechanical brakes. But, it is a smooth transition -- there is no speed at which there is an abrupt shift from regenerative to mechanical braking.
 

·
Registered
Joined
·
115 Posts
You can tell sometimes when the friction brakes pull in, usually I can tell when it happens, you can tell the rears tend to grab after the fronts have been on regen braking, at high speed braking it almost seems to brake loose the grip on the rears for a fraction of a second.
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top