Item name | Spare part number | Description |
1 | - | master cylinder |
2 | - | Tank |
3 | - | Brake booster |
4 | - | Brake pedal |
5 | - | HCU (hydraulic control unit) |
6 | - | Pressure meter |
7 | - | Priming valve |
8 | - | control valve |
9 | - | Return pump motor |
10 | - | return pump |
11 | - | Inlet valve |
12 | - | bypass valve |
13 | - | Receiver |
14 | - | Exhaust valve |
15 | - | The brake mechanism of the left forward wheel |
16 | - | Brake mechanism of the right forward wheel |
17 | - | Brake mechanism of the right back wheel |
18 | - | Brake mechanism of the left rear wheel |
HCU block (hydraulic control unit) has three operating modes: Normal braking / EBD (electronic brake force distribution), ABS braking (anti-lock braking system) and active braking.
Normal braking mode/EBD
Initially, no voltage is applied to any solenoid valve. When changing the position of the brake pedal, the pressure in the brake mechanisms increases or decreases through the open control and intake valves. If the ABS module (anti-lock braking system) specifies to enable EBD (electronic brake force distribution), it energizes the intake valves of the rear axle brakes to prevent further increase in hydraulic pressure in them.
ABS braking mode
If the ABS module (anti-lock braking system) determines that ABS braking is required (anti-lock braking system), it energizes the intake and exhaust valves of the corresponding brake mechanism and activates the return pump. The intake valve closes to isolate the brake mechanism from brake fluid pressure; the exhaust valve opens to relieve pressure from the brake mechanism and into the receiver and return pump circuit; the reduction in pressure allows the wheel to increase its rotational speed. Then the ABS module (anti-lock braking system) controls intake and exhaust valves, adjusting brake pressure to provide maximum braking force without wheel lockup. The valves of each wheel are controlled separately.
Active braking mode
Active braking mode is used to create and regulate hydraulic pressure in the brake mechanisms for functions other than braking with ABS (anti-lock braking system), such as DSC, EBA (emergency brake assist), ETC, HDC and dynamic parking brake.
For active braking ABS module (anti-lock braking system) energizes the pilot and prime valves, turns on the return pump, and energizes all inlet valves. Brake fluid, taken from the reservoir through the master cylinder and filling valve, is supplied under pressure by a return pump to the intake valves. Then the ABS module (anti-lock braking system) controls the intake and exhaust valves by adjusting the pressure in the individual brakes. Noise may be heard during active braking.
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