Brake System - General Information: Overview Ford Escape I рестайлинг

Principles of Operation

Applying the brake pedal uses lever action to push a rod into the brake booster, which through the use of vacuum, boosts the force of the rod and then transmits this force into the master cylinder. This produces hydraulic pressure in the master cylinder. The hydraulic pressure is transmitted by brake fluid through the brake lines to the individual brake calipers or wheel cylinders. The brake calipers or wheel cylinders use hydraulic pressure to apply the pads or shoes. The application of the brake pads or shoes will cause the rotation of the wheels to slow or stop depending on how much brake pressure is applied. The parking brakes carry out the same function except that they are mechanically actuated by a cable that connects only to the rear brakes.

Brake Booster - Operation Check

1. Inspect all vacuum hoses and connections. All unused vacuum connections must be capped. Hoses and their connections must be correctly secured and in good condition with no holes, cracks, or collapsed areas.
2. Check the brake hydraulic system for leaks or insufficient brake fluid. Repair as necessary.
3. With the engine off, place the transaxle in PARK (A/T) or NEUTRAL (M/T) and apply the parking brake.
4. Apply and hold the brake pedal several times to exhaust all of the vacuum reserve from the system.
5. Apply and hold the brake pedal.
6. Start the engine. If the vacuum system is operating, the brake pedal will move downward slightly under constant foot pressure. If no movement occurs, the power brake booster system is not functioning. Turn the engine off.
7. Remove the vacuum hose from the power brake booster.
8. Place the transaxle in PARK (A/T) or NEUTRAL (M/T) and apply the parking brake. Start the engine. Manifold vacuum should be available from the vacuum booster hose. If manifold vacuum is not available, inspect all of the hoses and hose connections. Repair as necessary.
9. Connect the vacuum booster hose and run the engine at fast idle for 10 seconds.
10. Turn off the engine and let the vehicle stand for 10 minutes.
11. Apply the brake pedal with approximately 89 Newtons (20 lbs) of force. The brake pedal feel should be the same as normal power-assisted brake operation for at least one brake pedal application. If the brake pedal feel is normal, the power brake booster is OK. If the brake pedal feels hard, continue with the test.
12. Remove the vacuum booster hose from the power brake booster. Apply 57.3 kPa (17 in-Hg) of vacuum to the vacuum booster hose. If the vacuum does not leak off after 10 minutes, install a new power brake booster. If the vacuum does leak off, install a new check valve and/or new vacuum booster hoses.

The hydraulic control unit (HCU) controls the brake assist function as well as the anti-lock functions. The HCU contains an accumulator, driven by an electric motor, to supply pressurized brake fluid to the disc brake calipers during brake application. The electric motor begins to build pressure in the accumulator whenever the vehicle doors are opened or when the dome light is activated. The electric motor also charges the accumulator and initiates the brake system self-test whenever the ignition switch is turned to the ON position or the brake pedal is applied. During this time, 12 mm (0.47 in) of brake fluid is drawn from the master cylinder reservoir into the accumulator. The accumulator discharges 4 minutes after the ignition switch is turned to the OFF position and the vehicle dome light turns off, returning the brake fluid used during the charging of the accumulator to the master cylinder reservoir.

The regenerative braking system recovers the vehicle kinetic energy during deceleration to replace the high voltage traction battery energy. A certain level of regenerative braking is commanded by releasing the accelerator pedal. Further regenerative braking is commanded by applying the brake pedal. Whenever the anti-lock brake system (ABS) is activated, the affects of regenerative braking are reduced until the ABS event is over and the accelerator is applied.

The series of regenerative braking feature provides isolation of the driver brake demand from the friction brakes in order to provide a portion of the braking through negative torque request to the electric drive motor. In addition, this torque request results in a change in the flow of energy. The energy flows into, rather than out of, the battery. The motor's change from drive motor to generator is referred to as regeneration.

Regenerative braking logic is as follows

1. The ABS module determines the total torque request from accelerator pedal and brake pedal input.
2. The ABS module compares the drivers total request for a reduction of speed to the powertrain control module's (PCM) ability to slow the vehicle or negative "torque limit."
3. The ABS module requests the reduction in speed up to the torque limit from the PCM, via a torque modification request message sent to the PCM.
4. The ABS module applies the friction brakes beyond the torque limit.

Normal Operation

The red brake warning indicator, located on the instrument cluster, illuminates at prove out when the brake fluid in the brake master cylinder reservoir is below an acceptable level, when the parking brake is engaged, or if DTCs are present.

The ABS module internally monitors the HCU internal pressure and the hydraulic brake pressure to each wheel. If the pressure drops below acceptable limits, the ABS module sets a DTC and the red brake warning indicator and ABS light illuminate.

The ABS module sends voltage to the brake pedal travel sensor through circuit 3601 (WH/RD) and circuit 3603 (RD). The sensor is grounded through the ABS module on circuit 3600 (RD/WH) and circuit 1904 (GY/BK). The ABS module sends a reference signal to the brake pedal travel sensor on circuit 1905 (GY) and circuit 1820 (RD/YE).

The ABS module sends voltage to the brake pedal travel sensor through circuit 3601 (WH/RD) and circuit 3603 (RD). The sensor is grounded through the ABS module on circuit 3600 (RD/WH) and circuit 1904 (GY/BK). The ABS module sends a reference signal to the brake pedal travel sensor on circuit 1905 (GY) and circuit 1820 (RD/YE).