# US 2018/0022332 A1 · Brake Apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0022332 A1 - Document ID: US20180022332A1 - Status: Published application - Kind: A1 - Application number: 15/549,754 - Filed: 2016-02-09 - Published: 2018-01-25 - Earliest claimed: 2015-02-17 - Assignees: Hitachi Automotive Systems, Ltd. - Applicants: Hitachi Automotive Systems, Ltd. - Inventors: Hiroki SONODA; Toshiya OOSAWA; Asahi WATANABE - Web page: https://patentgrep.com/patent/US20180022332A1 ## CPC - B60T 8/4081: {Systems with stroke simulating devices for driver input (B60T8/4077 takes precedence)} - B60T 7/042: {by electrical means, e.g. using travel or force sensors} - B60T 8/363: {in hydraulic systems (B60T8/3655, B60T8/3675 and B60T8/369 take precedence)} - B60T 8/3655: {Continuously controlled electromagnetic valves} - B60T 8/885: {using electrical circuitry} - B60T 11/20: Tandem, side-by-side, or other multiple master cylinder units - B60T 13/146: {Part of the system directly actuated by booster pressure} - B60T 13/662: {characterised by specified functions of the control system components} - B60T 13/686: {in hydraulic systems or parts thereof} - B60T 2220/04: Pedal travel sensor, stroke sensor; Sensing brake request - B60T 2270/404: Brake-by-wire or X-by-wire failsafe - B60T 2270/82: Brake-by-Wire, EHB - B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES ## Abstract An object of the present invention is to provide a brake apparatus capable of acquiring a sufficient braking force when an abnormality has occurred. The brake apparatus includes a stroke simulator. The stroke simulator is connected to a portion of an oil passage between a master cylinder and a valve. The oil passage connects the master cylinder and a wheel cylinder therebetween. The stroke simulator is configured to generate a brake operation reaction force due to an increase and a reduction in a volume of a positive pressure chamber formed inside the stroke simulator. Brake fluid contained in a first chamber of the master cylinder flows into the positive pressure chamber at the time of control by a by-wire control unit. A fluid amount that can be supplied from the first chamber is larger than a fluid amount that the positive pressure can absorb therein. ## Claims ### Claim at position 1 -17. (canceled) ### Claim 18 A brake apparatus comprising: an oil passage connecting a master cylinder and a wheel cylinder therebetween; a valve configured to switch a communication state of the oil passage; a by-wire control unit configured to close the valve to increase a pressure in the wheel cylinder by a hydraulic source provided separately from the master cylinder, according to a state of a brake operation performed by a driver; a pressing force brake unit configured to open the valve to increase the pressure in the wheel cylinder by the master cylinder; and a stroke simulator connected to a portion of the oil passage between the master cylinder and the valve, and configured to generate a brake operation reaction force due to an increase and a reduction in a volume of a positive pressure chamber formed inside the stroke simulator, wherein brake fluid contained in a first chamber of the master cylinder flows into the positive pressure chamber at the time of control by the by-wire control unit, and wherein a fluid amount that can be supplied from the first chamber is larger than a fluid amount that a positive pressure chamber can absorb therein. ### Claim 19 (depends on 18) The brake apparatus according to claim 18, wherein the fluid amount that can be supplied from the first chamber is equal to or larger than a sum of the fluid amount that the positive pressure chamber can absorb therein and a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit. ### Claim 20 (depends on 18) The brake apparatus according to claim 18, wherein the master cylinder includes a second chamber partitioned off from the first chamber and connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected, and wherein a fluid amount that can be supplied from the second chamber is smaller than the fluid amount that can be supplied from the first chamber. ### Claim 21 (depends on 20) The brake apparatus according to claim 20, wherein the fluid amount that can be supplied from the second chamber is a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit. ### Claim 22 (depends on 18) The brake apparatus according to claim 18, wherein the master cylinder is activated in response to a stroke of a brake operation member, and wherein a maximum stroke amount of the brake operation member, among stoke amounts including a stroke amount when the pressing force brake unit is activated, is set to a value acquired by multiplying, by a predetermined ratio, a sum of a value resulting from dividing the fluid amount that can be supplied from the first chamber by a cross-sectional area of the master cylinder, and a value resulting from dividing a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit by the cross-sectional area of the master cylinder. ### Claim 23 (depends on 18) The brake apparatus according to claim 18, wherein the master cylinder is activated in response to a stroke of a brake operation member, and wherein the fluid amount that the positive pressure chamber can absorb therein is a value acquired by multiplying, by a cross-sectional area of the master cylinder, a value resulting from dividing a maximum stroke amount of the brake operation member at the time of the control by the by-wire control unit by a predetermined ratio. ### Claim 24 (depends on 18) The brake apparatus according to claim 18, wherein the master cylinder is activated in response to a stroke of a stroke operation member, and includes a primary piston configured to be activated according to an operation of the brake operation member, and a secondary piston defining the first chamber while defining, together with the primary piston, a second chamber connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected, and wherein a maximum stroke amount of the brake operation member, among stoke amounts including a stroke amount when the pressing force brake unit is activated, is set to a value equal to or larger than a value acquired by multiplying, by a predetermined ratio, a sum of a required stroke amount of the primary piston and a required stroke amount of the secondary piston. ### Claim 25 (depends on 24) The brake apparatus according to claim 24, wherein the primary piston and the secondary piston have cross-sectional areas equal to each other, wherein the required stroke amount of the primary piston is a value acquired by dividing a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit by the cross-sectional area of the primary piston or the secondary piston, and wherein the required stroke amount of the secondary piston is a value acquired by dividing a sum of the fluid amount that the positive pressure chamber can absorb therein and the fluid amount required to generate the target wheel cylinder pressure by the pressing force brake unit by the cross-sectional area of the primary piston or the secondary piston. ### Claim 26 (depends on 25) The brake apparatus according to claim 25, wherein the fluid amount that the positive pressure chamber can absorb therein is a value acquired by multiplying, by the cross-sectional area of the primary piston or the secondary piston, a value resulting from dividing the maximum stroke amount of the brake operation member at the time of the control by the by-wire control unit by a predetermined ratio. ### Claim 27 (depends on 18) The brake apparatus according to claim 18, wherein the master cylinder is activated in response to a stroke of a stroke operation member, and includes a primary piston configured to be activated according to an operation of the brake operation member, and a secondary piston defining the first chamber while defining, together with the primary piston, a second chamber connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected. ### Claim 28 A brake apparatus comprising: an oil passage connecting a master cylinder and a wheel cylinder therebetween; a valve configured to switch a communication state of the oil passage; a by-wire control unit configured to close the valve to increase a pressure in the wheel cylinder by a hydraulic source provided separately from the master cylinder according to a state of a brake operation performed by a driver; a pressing force brake unit configured to open the valve to increase the pressure in the wheel cylinder by the master cylinder; and a stroke simulator connected to a portion of the oil passage between a first chamber of the master cylinder and the valve and including a piston therein, the stroke simulator being configured to generate a brake operation reaction force due to an increase and a reduction in a volume of a positive pressure chamber according to activation of the piston in an axial direction, wherein a brake fluid amount that can flow out from the first chamber at the time of control by the by-wire control unit is set to a larger amount than a brake fluid amount flowing into the positive pressure chamber until the piston is maximally stroked. ### Claim 29 (depends on 28) The brake apparatus according to claim 28, wherein the master cylinder includes a second chamber partitioned off from the first chamber and connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected, and wherein a fluid amount that can be supplied from the second chamber is smaller than a fluid amount that can be supplied from the first chamber. ### Claim 30 (depends on 28) The brake apparatus according to claim 28, wherein the fluid amount that can be supplied from the first chamber is equal to or larger than a sum of a fluid amount that the positive pressure chamber can absorb therein and a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit. ### Claim 31 (depends on 30) The brake apparatus according to claim 30, wherein the master cylinder includes a second chamber partitioned off from the first chamber and connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected, and wherein a fluid amount that can be supplied from the second chamber is a fluid amount required to generate a target wheel cylinder pressure by the pressing force brake unit. ### Claim 32 A brake apparatus comprising: a master cylinder including a first chamber connected to a first pipe system; a stroke simulator provided in a branch oil passage branching off from an oil passage connecting the first chamber and a wheel cylinder therebetween, and configured in such a manner that a piston dividing an inside of the stroke simulator is activated and a volume of a positive pressure chamber inside the stroke simulator is increased or reduced due to an inflow of brake fluid thereto; a by-wire control unit configured to close a valve provided in the oil passage to increase a pressure in the wheel cylinder by a pump provided separately from the master cylinder according to a state of a brake operation performed by a driver; and a pressing force brake unit configured to open the valve to increase the pressure in the wheel cylinder by the master cylinder, wherein a brake fluid amount in the first chamber when the master cylinder is deactivated is larger than a brake fluid amount in the positive pressure chamber when the piston is maximally stroked. ### Claim 33 (depends on 32) The brake apparatus according to claim 32, wherein the master cylinder is activated in response to a stroke of a stroke operation member, and includes a primary piston configured to be activated according to an operation of the brake operation member, and a secondary piston defining, together with the primary piston, the first chamber while defining a second chamber connected to the wheel cylinder via the oil passage to which the stroke simulator is not connected. ### Claim 34 (depends on 33) The brake apparatus according to claim 33, wherein a fluid amount that can be supplied from the second chamber is smaller than a fluid amount that can be supplied from the first chamber.