Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
1999-08-27
2001-09-04
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
Reexamination Certificate
active
06283561
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a brake force control apparatus and, more particularly, to a brake force control apparatus which generates, when an emergency brake operation is performed in a vehicle, a relatively large brake force as compared to that generated during a normal brake operation.
BACKGROUND ART
Conventionally, as disclosed in Japanese Laid-Open Patent Application No.4-121260, a brake force control apparatus is known which increases a power ratio of a brake booster when a brake pedal is depressed at a speed exceeding a predetermined speed.
A driver of a vehicle operates a brake pedal at a high speed when a rapid increase in a brake force is desired (hereinafter, this operation is referred to as an emergency brake operation). According to the above-mentioned brake force control apparatus, it is determined that the emergency brake operation is performed if an operating speed of the brake pedal is larger than a predetermined value, and a brake force larger than that of a normal time is obtained by increasing a pressure of brake fluid stored in a reservoir and supplying the brake fluid to wheel cylinders. Hereinafter, this control is referred to as a brake assist control (abbreviated as BA control).
According to the above-mentioned brake force control apparatus, a power ratio larger than that of a normal time can be generated when an emergency brake operation is performed so that an advantageous state is established in rapidly increasing a brake force. Accordingly, when the driver performs an emergency brake operation, a brake force which appropriately responds to a request of the driver can be generated.
In order to generate a brake force larger than that of a normal time when the driver performs an emergency brake operation, means for increasing brake fluid must be provided to the brake force control apparatus. Various means can be considered as such means for increasing the pressure of the brake fluid. A pump is considered to be one of the various means. It is appropriate to change a tendency of rising of a brake force.
The conventional brake force control apparatus generates a brake force larger than that applied in a normal condition by always changing the power ratio of the brake booster in the same manner when an emergency brake operation is performed. Thus, when an emergency brake operation is performed, a brake force to which the driver's intention is reflected cannot be generated by the above-mentioned conventional brake force control apparatus.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a brake force control apparatus which can generate a brake force to which a driver's intention is reflected when an emergency brake operation is performed by the driver.
The above-mentioned object can be achieved by a brake force control apparatus for generating an increased brake fluid pressure which is greater than that generated in a regular brake operation when an emergency brake operation is performed by a driver, the brake force control apparatus characterized by:
operating speed detecting means for detecting a brake operating speed;
emergency brake operation detecting means for detecting execution of an emergency brake operation; and
brake fluid pressure increasing means for generating the increased brake fluid pressure by adding an assist pressure corresponding to the brake operating speed generated in a process of the emergency brake operation, when the emergency brake operation is detected.
According to the above-mentioned invention, it can be determined that the driver intends to moderately increase the brake force when the brake operating speed is relatively low during a process of an emergency brake operation. On the other hand, if the brake operating speed is relatively high during an emergency brake operation, it can be determined that the driver intends to rapidly increase the brake force. The brake fluid pressure increasing means increases the assist pressure, which is in addition to the brake fluid pressure when an emergency brake operation is performed, in response to the brake operating speed detected during the emergency brake operation when the brake operating speed is high, and decreases the assist pressure when the brake operating speed is low. When the brake fluid pressure is thus controlled, the brake force is immediately increased to a pressure which is intended by the driver after an emergency brake operation is performed.
In the brake force control apparatus according to the present invention, the brake fluid pressure increasing means may comprise:
assist pressure generating means for increasing the brake fluid pressure with a predetermined change rate irrespective of whether a brake operation is present; and
assist time control means for controlling, when the emergency brake operation is detected, the assist pressure generating means to increase the brake fluid pressure only for a pressure increasing period corresponding to the brake operating speed generated in the process of the emergency brake operation.
According to this invention, the assist pressure to be added to the brake fluid pressure when en emergency brake operation is performed is generated by first assist pressure generating means. The pressure increasing period used by the first assist pressure generating means is set to be a longer time based on the brake operating speed generated in a process of the emergency brake operation when the brake operating speed is high, and is set to be a shorter time when the brake operating speed is low. In this case, the brake force is immediately increased to a level requested by the driver after the emergency brake operation is performed.
Additionally, the first assist pressure generating means may include an accumulator storing a predetermined fluid pressure as a fluid pressure source of the assist pressure; and
the brake force control apparatus may further comprise pressure increasing period correcting means for correcting the pressure increasing period used by the first assist pressure generating means based on the brake fluid pressure when an increase of the brake fluid pressure is started by the first assist pressure generating means.
In this invention, the pressure increasing period used by the first assist pressure generating means is corrected to be longer as the brake fluid pressure is higher based on the brake fluid pressure when the increase of the brake fluid pressure is started, and corrected to be shorter as the brake fluid pressure is lower. The first assist pressure generating means increases the brake fluid pressure by using the accumulator as a fluid power source. When the brake fluid pressure is increased by using the accumulator as a fluid power source, the brake fluid pressure is increased by a steeper slope of the increasing rate as a difference between the brake fluid pressure and a pressure in the accumulator. When the pressure increasing period used by the first assist pressure generating means is corrected as described above, a substantially constant assist pressure is maintained irrespective of whether the brake fluid pressure when the increase of the brake fluid pressure is started is higher or lower. In this case, the brake force is immediately increased to a level intended by the driver after the emergency brake operation is performed.
Additionally, in the brake force control apparatus according to the present invention, the brake fluid pressure increasing means may comprise:
second assist pressure generating means for increasing the brake fluid pressure irrespective of whether a brake operation is present; and
assist time control means for controlling, when the emergency brake operation is detected, the second assist pressure generating means to increase the brake fluid pressure by a pressure increasing slope corresponding to the brake operating speed generated in the process of the emergency brake operation.
In this invention, the assist pressure added to the brake fluid pressure when an emergency brake operation is detected is generated by the second
Bartz C. T.
Kenyon & Kenyon
Schwartz Christopher P.
Toyota Jidosha & Kabushiki Kaisha
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