Combined hydraulic and regenerative brake system in an electric vehicle

A brake system in an electric vehicle including driven wheels which are connected to and driven by an electric motor using a battery as an energy source and which driven wheels are capable of being liquid-pressure braked and regeneratively braked, comprising:

• a liquid pressure braking means for liquid pressure braking said driven wheels in response to the operation of a brake pedal connected to a master cylinder for supplying a liquid pressure;
• a regenerative braking means for regenerative braking said driven wheels in response to the operation of said brake pedal;
• a pressure sensor for sensing the liquid pressure supplied by said master cylinder;
• a liquid pressure control means for controlling the braking liquid pressure transferred from the master cylinder to the liquid pressure braking means during a regenerative braking;
• and
• a braking control means for controlling both said liquid pressure control means and said regenerative braking means based on the master cylinder liquid pressure sensed by said pressure sensor, as follows:
• (a) to cause said liquid pressure control means to supply to said liquid pressure braking means the full master cylinder liquid pressure and to cause said regenerative braking means to produce no regenerative braking when said sensed pressure is less than a predetermined value,
• (b) to cause said liquid pressure control means to supply to said liquid pressure braking means a predetermined magnitude of liquid pressure and to cause said regenerative braking means to produce a regenerative braking force progressively increasing from zero to a maximum amount when and as said sensed pressure increases from said predetermined value to an intermediate value, and
• (c) to cause said liquid pressure control means to supply to said liquid pressure braking means with a progressively increasing liquid pressure above said predetermined magnitude as said sensed pressure progressively increases beyond said intermediate value and to cause said regenerative braking means to produce a constant regenerative braking force of said maximum amount when said sensed pressure exceeds said intermediate value;
• said braking control means also controlling both said liquid pressure control means and said regenerative braking means for causing a sum of said braking liquid pressure braking force generated by said liquid pressure braking means and said regenerative braking force generated by said regenerative braking means to be varied at a predetermined fixed rate in response to a change in the amount of the operation of said brake pedal.