Kia Soul EV: AHB(Active Hydraulic Boost) System / Description and Operation

Kia Soul EV (PS EV) 2015-2020 Service Manual / Brake System / AHB(Active Hydraulic Boost) System / Description and Operation

Description

Regeneration Brake System

During deceleration or braking of an electric vehicle or HEV, the drive motor acts as an alternator and charges the battery by converting the vehicle’s kinetic energy generated during braking into electrical energy.

Regenerative braking amount depends on the vehicle speed, battery SOC, etc.

Achieve significant improvement in fuel efficiency in city driving with repeated acceleration and deceleration.

Regenerative Braking Cooperation Control (RBC)

The brake force application is distributed by controlling hydraulic braking. The total brake force output that the driver demands is achieved by combining hydraulic and regenerative brakes. In the case of regenerative brake failure, the total brake force that the driver demands is supplied by the hydraulic brake system.

The AHB system is composed of the Pressure Source Unit (PSU) and the Integrated Brake Actuation Unit (IBAU).

First, the PSU generates the hydraulic pressure required for braking.

Similar to the boosting effect when the driver steps on the brake pedal in a system equipped with a vacuum booster, the hydraulic pressure stored in the cylinder is supplied to provide pressure throughout the entire brake line.

Second, the IBAU delivers pressure generated by the PSU to a caliper on each wheel. Also, it is connected to the brake pedal to detect the brake force demanded by the driver and to generate the braking feeling.

The IBAU carries out the ABS, TCS, and ESC functions as in conventional vehicles.

AHB System Operation Principles

1. Initial Status

High pressure (180 bar) is generated between the PSU and the IBAU at all times. Therefore, before removing the PSU or the IBAU, high pressure between them should be reduced for safety by conducting"High pressure releasemode" of GDS connected to SOUL EV.

2. Brake operation

Apply Mode: When the driver presses down the brake pedal, the IN valve turns ON, delivering the high pressure generated from PSU to the caliper by IBAU to engage in brake operation.

The level of brake force is determined by the pedal simulator according to the measurement of the pedal stroke sensor signal.Release Mode: When the driver releases the brake pedal, the OUT valve opens and the IN valve closes, returning the high pressure of brake oil back to PSU. At the same time, the CUT valve turns ON to prevent backflow of brake oil into the IBAU.

2. Brake malfunction

When either PSU or IBAU is faulty, both IN and OUT valves will close and the CUT valve will turn off. In this case, brake force can only be generated by pressing down the brake pedal manually.

Integrated Brake Actuation Unit (IBAU) System (1)

Integrated Brake Actuation Unit (IBAU) System (2)

Integrated Brake Actuation Unit (IBAU) System (3)

Integrated Brake Actuation Unit (IBAU) System (4)

IBAU connector input/output

		Description			Description
1.	R	E/R Junction Block (Fuse - IBAU 1)	24.	-	-
2.	R	PSU Motor (+)	25.	-	-
3.	-	-	26.	-	-
4.	B	PSU Motor (Shield Ground 2)	27.	G	Rear Wheel Sensor LH (SIG)
5.	G	Smart Junction Block (Fuse - IBAU)	28.	B	Front Wheel Sensor LH (SIG)
6.	R	Brake Pedal Sensor(PDT Input (Power))	29.	L	Smart Junction Block(IPS Control Module)
7.	P	Brake Pedal Sensor(PDF Input (Power))	30.	Y	E/R Junction Block (Fuse - IBAU 2)
8.	G/O	Stop Signal Electronic Module(HAC Signal)	31.	B	Brake Pedal Sensor(PDF (Ground))
9.	-	-	32.	-	-
10.	G/Y	Brake Pedal Sensor(PDT (Ground))	33.	O	Rear Wheel Sensor LH (VCC)
11.	B	PSU Motor (Shield Ground 1)	34.	Y	Rear Wheel Sensor RH (VCC)
12.	-	-	35.	-	-
13.	W	PSU Motor (-)	36.	G	Stop Signal Electronic Module (Stop Lamp Signal)
14.	B	Ground (GE06)	37.	L	Stop Signal Electronic Module(Stop Lamp)
15.	-	-	38.	G	SRS Control Module(Local CAN (High))
16.	O/B	Crash Pad Switch(ESC OFF Switch)	39.	Br	SRS Control Module(Local CAN (Low))
17.	P	Front Wheel Sensor LH (VCC)	40.	Y	Smart Key Control Module (Wheel Sensor Signal)
18.	Br	Front Wheel Sensor RH (VCC)	41.	-	-
19.	W	C-CAN (High)	42.	P	Front Wheel Sensor RH (SIG)
20.	Br	C-CAN (Low)	43.	B	Rear Wheel Sensor RH (SIG)
21.	-	-	44.	L	Stop Lamp Switch (B)
22.	W	Brake Pedal Sensor(PDT Output (Signal))	45.	-	-
23.	Br	Brake Pedal Sensor(PDF Output (Signal)	46.	B	Ground (GE06)

Operation and Leakage Check

Check all of the following items:

Component	Procedure
Integrated Brake Actuation Unit (IBAU) (A) and Pressure Source Unit (PSU) (B)	Check brake operation by applying the brakes during a test drive. If the brakes do not work properly, check the IBAU and PSU. Replace IBAU and PSU as an assembly if it does not work properly or if there are signs of leakage.
Piston cup and pressure cup inspection (B)	Check brake operation by applying the brakes. Look for damage or signs of fluid leakage. Replace the IBAU as an assembly if the pedal does not work properly or if there is damage or signs of fluid leakage.
Brake hoses (C)	Look for damage or signs of fluid leakage. Replace the brake hose with a new one if it is damaged or leaking.
Caliper piston seal and piston boots (D)	Check brake operation by applying the brakes. Look for damage or signs of fluid leakage. If the pedal does not work properly, the brakes drag, or there is damage or signs of fluid leakage, disassemble and inspect the brake caliper. Replace the boots and seals with new ones whenever the brake caliper is disassembled.

AHB(Active Hydraulic Boost) System

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