Brakes hydro accumulator internals? (1 Viewer)

[akshimassar]

Hey, guys! I'm new to the forum and I'd like to know how. How is it made. I'm thrilled to discuss some technical details about Land Cruiser.
I'm an engineer. Technically programmer but I prefer engineer since it better reflects my desire to understand how things work and rely on facts during the process. So I'm trying to back up my opinion with arguments and physics (I love physics).

I'm new to driving, traveling by car and overlanding. But not new camping / hiking. Currently we are building (with my spouse and doggo) overlanding rig for traveling to the remote parts of Russia (and hopefully other countries). It's green and big If you are interested in details I can make a separate thread with brief description of mods. Something we do by ourselves other thing we don't have time and/or equipment.


I have an argument about brake booster with one user from Russia. And during this argument he stated that pressure accumulator has elastic membrane (elastic rubber) which separates gas chamber from brake fluid. And I highly doubt that it is made like that. Did anyone dissemble that part?

Here is what I think about accumulator. It could be made using elastic membrane separating gas chamber using gas as pressure provider but. First, leaking gas into brake fluid is dangerous (and this might happen due to membrane fail). Second, the shape of accumulator is not optimal for gas chamber. Her is one with gas chamber.

I think that instead it's a cylinder with piston. Pressure of fluid moves piston which compresses the spring. Piston is probably sealed with couple of o-rings. Second chamber might be filled with gas or left opened, dunno.

Here is one more related question. Leaking the pressure over time. Like you leave a car with ignition off for a day and next day you switch it on and brake booster motor pumps pressure for some time. BTW I checked mine and did not lost any significant pressure over 18 hours (no pumping after start). Sooo that process usually referred here (in Russia) as accumulator leaking. But there is no real ways for accumulator to leak (unless it does not have rust hole). The only thing it can do is loose volume (but then it would build up pressure extremely fast). So I think the leaking happens elsewhere, probably in the part connecting booster (accumulator and rotor) or around the main cylinder. What do you think? Does anyone knows for sure?

 

[2001LC]

Not sure if first pictures is for example. But to be clear, that has nothing to do with brakes. It is 1 of, 4 of the damping force control actuator of AHC suspension. It's gas chamber is commonly call a "globe". There is also 1 height control accumulator.

The second picture above, looks to be the brake booster accumulator.

All are gas filled. The FSM gives specific instruction on discharging the gas, before disposing of them.

 

[akshimassar]

Yes, first picture is an example of pressure accumulator based on elastic membrane, not related to brakes. Second one is my thoughts about internals of brake booster accumulator used in 100 series.

Thanks for referring to the manual, here is the link Toyota Land Cruiser: Disposal - Hydraulic brake booster - Brake
It seems service manual can be a source of information about internals however not describing it directly. I'm still wonder how loss of booster pressure happens.

 

[2001LC]

It's all sun power!

The pressure is created by the booster pump. Which pump is turned/powered by the booster motor. The gas (nitrogen, or so I've heard) chamber has membrane of some sort, that keeps gas and brake fluid separated. The pump builds pressure by forcing brake fluid against the membrane, storing the energy in the gas (compressed gas). We press on brake pedal and the stored energy force brake fluid into chambers in the master cylinder, by way the red hard brake line. That red hard line, is a ~3,000 PSI rated line.

Typically when this type of booster assist brake master, sit idle overnight. Some pressure is lost. So when IG key turned to ON. The booster motor receives 12 volts from battery, and motor turns (runs). Newer booster motors are very hard to hear running. Some I need hood open with no other sounds around, to hear it running.

IDK, if this "pressure loss" is all/or mostly from bleeding into the brake system, through master. But that has been my assumption most lose is from fluid leaking past the seals (O-rings in master). It is commonly believed however, that all these gas chambers lose their charge of gas over time. They then weaken in ability to store energy. The prime example is the AHC globes and height accumulator need replacing at some point.

The energy is from the sun. That energy is actually stored in carbon. In that the fuel source is petroleum. Which engine uses to produce energy by detonation of the carbon with oxygen, releasing its stored energy. Which alternator takes from engine revolution, some of this energy, expressed in HP. To generate 12 volts for the brake booster motor and many uses like starting. The accumulator is just a gas filled storage device, a battery of sorts.

 

[akshimassar]

I like the thought that I have a bit of sun inside my car

I recently replaced brake booster and later entire master cylinder assembly (with brake booster). Initial reason for that was brake booster loosing pressure over night. Unfortunately I didn't have time to properly check first replacement to know if it fixed the leakage. I later had to replace it due to motor problems.

Leaking through main cylinder seems logical to me. Brake booster works without electricity meaning that no solenoids being open, at least I think so (I didn't check it with electrical accumulator removed). And only thing that is moved when you press on the pedal is supposed to be mater piston. So some part of master cylinder should be under constant pressure from brake booster and that might lead to leaks.

Oh, look! I found amazing description for Pajero IV hydraulic brake booster, the unit looks very similar, even electrical plugs are looking the same. Gonna read it through and try to understand. HYDRAULIC BRAKE BOOSTER

 

[IndroCruise]

Hey, guys! I'm new to the forum and I'd like to know how. How is it made. I'm thrilled to discuss some technical details about Land Cruiser.
I'm an engineer. Technically programmer but I prefer engineer since it better reflects my desire to understand how things work and rely on facts during the process. So I'm trying to back up my opinion with arguments and physics (I love physics).

I'm new to driving, traveling by car and overlanding. But not new camping / hiking. Currently we are building (with my spouse and doggo) overlanding rig for traveling to the remote parts of Russia (and hopefully other countries). It's green and big If you are interested in details I can make a separate thread with brief description of mods. Something we do by ourselves other thing we don't have time and/or equipment.


I have an argument about brake booster with one user from Russia. And during this argument he stated that pressure accumulator has elastic membrane (elastic rubber) which separates gas chamber from brake fluid. And I highly doubt that it is made like that. Did anyone dissemble that part?

Here is what I think about accumulator. It could be made using elastic membrane separating gas chamber using gas as pressure provider but. First, leaking gas into brake fluid is dangerous (and this might happen due to membrane fail). Second, the shape of accumulator is not optimal for gas chamber. Her is one with gas chamber.
View attachment 2468958

I think that instead it's a cylinder with piston. Pressure of fluid moves piston which compresses the spring. Piston is probably sealed with couple of o-rings. Second chamber might be filled with gas or left opened, dunno.
View attachment 2468979

Here is one more related question. Leaking the pressure over time. Like you leave a car with ignition off for a day and next day you switch it on and brake booster motor pumps pressure for some time. BTW I checked mine and did not lost any significant pressure over 18 hours (no pumping after start). Sooo that process usually referred here (in Russia) as accumulator leaking. But there is no real ways for accumulator to leak (unless it does not have rust hole). The only thing it can do is loose volume (but then it would build up pressure extremely fast). So I think the leaking happens elsewhere, probably in the part connecting booster (accumulator and rotor) or around the main cylinder. What do you think? Does anyone knows for sure?

You have received some good answers already. The Slideshow at the first link below gives some idea of the internal arrangements in a typical Toyota brake system with hydraulic accumulator and booster, in this case for a Toyota Prius. The LC100/LX470 systems were designed much earlier and so obviously they are not quite the same. However, you can get an idea of the arrangements and the internal parts from some of the cross-sections shown in the slides.

Contents Click a Section Tab New Model PRIUS ppt download

As already mentioned by others and you have found already, some details of the hydraulic brake accumulator as used in many Lexus LX470 vehicles and many Toyota Landcruiser 100 series models can be seen at the following reference:

https://lc100e.github.io/manual/
Then use the tabs at the Index Panel on the left hand side of the opening page as follows:
Repair Manual > Hydraulic Brake Booster >

Just to be sure that we are all discussing the same thing, some photographs of the brake accumulator can be found at the following link:

Brake Master/Booster Pic?

As you mentioned, the picture in your post is part of the combined electro-hydraulic suspension systems called Active Height Control (AHC) and Toyota Electronic Modulated Suspension (TEMS). This is not like the brake system which is a completely different design. These AHC/TEMS systems were fitted to all Lexus LX470 vehicles. These systems were fitted only to selected Toyota Landcruiser “100 series” models in some markets. Many Landcruiser models have a conventional suspension system without AHC and TEMS.

For your interest, a description of AHC and TEMS can be found at the next reference:
https://lc100e.github.io/manual/
Then use the tabs at the Index Panel on the left hand side of the opening page as follows:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension and Skyhook TEMS