Hydraulic braking system

Patent metadata

Field	Value
Publication number	US-9919687-B2
Application number	US-201414902664-A
Country	US
Kind code	B2
Filing date	May 12, 2014
Priority date	Jul 18, 2013
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

Vibrations of a hydraulic pressure in an upstream portion due to operations of a slip control device during anti-lock control are transmitted to a control pressure chamber via a pressurizing piston of a master cylinder and a control piston of a regulator. During anti-lock control, in contrast, a pressure-increase linear valve and a pressure-reduction linear valve are opened, allowing change in volume of the control pressure chamber, resulting in reduction in stiffness. This reduction suppresses vibrations of a hydraulic pressure in the control pressure chamber, resulting in suppression of vibrations of a hydraulic pressure in a front pressure chamber. As a result, it is possible to reduce the lowering in control accuracy for a hydraulic pressure in a brake cylinder in anti-lock control using the hydraulic pressure in the front pressure chamber, which can well avoid a long braking distance.

First claim

The invention claimed is:

1. A hydraulic braking system, comprising:
a plurality of brake cylinders respectively provided for a plurality of wheels of a vehicle;
a hydraulic-pressure producing device; and
a slip control device provided between the hydraulic-pressure producing device; and the plurality of brake cylinders and configured to control a hydraulic pressure in each of at least one of the plurality of brake cylinders to control a slipping state of each of the plurality of wheels,
the hydraulic-pressure producing device comprising a stiffness reducer configured to reduce stiffness in an upstream portion located upstream of the slip control device such that the stiffness is less when the slip control device is in an operating state than when the slip control device is in a non-operating state,
wherein the stiffness is a value obtained by dividing an amount of increase in force applied to the upstream portion, by an amount of change in volume of the upstream portion.

2. The hydraulic braking system according to claim 1 ,
wherein the hydraulic-pressure producing device comprises (i) a master cylinder comprising (a) a pressurizing piston fluid-tightly and slidably fitted in a housing, (b) a front pressure chamber provided in front of the pressurizing piston and connected to the upstream portion, and (c) a rearward chamber provided at a rear of the pressurizing piston, and (ii) a rear-hydraulic-pressure control device capable of controlling a hydraulic pressure in the rearward chamber, and
wherein the rear-hydraulic-pressure control device comprises a rearward chamber stiffness reducer configured to reduce stiffness in the rearward chamber to reduce stiffness in the front pressure chamber, and the rearward chamber stiffness reducer is comprised in the stiffness reducer.

3. The hydraulic braking system according to claim 2 , wherein the rearward chamber stiffness reducer comprises a volume-change allowing device configured to allow change in volume of the rearward chamber in a greater degree in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.

4. The hydraulic braking system according to claim 2 ,
wherein the rear-hydraulic-pressure control device comprises:
(i) a regulator comprising (a) a control piston fluid-tightly and slidably fitted in the housing, (b) a control pressure chamber provided at a rear of the control piston, and (c) a servo chamber provided in front of the control piston and connected to the rearward chamber;
(ii) a pressure-increase linear valve provided between the control pressure chamber and a high pressure source, the pressure-increase linear valve being an electromagnetic valve comprising a coil;
(iii) a pressure-reduction linear valve provided between the control pressure chamber and a low pressure source, the pressure-reduction linear valve being an electromagnetic valve comprising a coil:
(iv) a control-pressure-chamber hydraulic pressure controller configured to control a current to be supplied to the coil of the pressure-increase linear valve and a current to be supplied to the coil of the pressure-reduction linear valve to control a hydraulic pressure in the control pressure chamber to control a hydraulic pressure in the servo chamber, and

wherein the control-pressure-chamber hydraulic pressure controller comprises a control-pressure-chamber stiffness reducer configured to control a current to be supplied to at least one of the coil of the pressure-increase linear valve and the coil of the pressure-reduction linear valve to reduce stiffness in the control pressure chamber such that the stiffness in the control pressure chamber is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state, and the control-pressure-chamber stiffness reducer is comprised in the rearward chamber stiffness reducer.

5. The hydraulic braking system according to claim 4 ,
wherein the pressure-reduction linear valve comprises a characteristic in which the pressure-reduction linear valve is in an open state when the hydraulic pressure in the control pressure chamber is greater than an opening and closing switching pressure in a state in which the current to be supplied to the coil of the pressure-reduction linear valve is kept, and the opening and closing switching pressure is determined by the current to be supplied to the coil of the pressure-reduction linear valve, and
wherein the control-pressure-chamber stiffness reducer comprises a pressure-reduction linear valve controller configured to control the current to be supplied to the coil of the pressure-reduction linear valve to reduce the opening and closing switching pressure such that the opening and closing switching pressure is less in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.

6. The hydraulic braking system according to claim 5 ,
wherein the rear-hydraulic-pressure control device comprises a target hydraulic pressure determiner configured to determine a target hydraulic pressure in the control pressure chamber based on a brake request, and
wherein the pressure-reduction linear valve controller comprises a target-hydraulic-pressure-change-based pressure-reduction linear valve controller configured to reduce the opening and closing switching pressure such that the opening and closing switching pressure is less when a tendency of the target hydraulic pressure in the control pressure chamber which is determined by the target hydraulic pressure determiner is a decreasing tendency than when the tendency of the target hydraulic pressure in the control pressure chamber which is determined by the target hydraulic pressure determiner is an increasing tendency.

7. The hydraulic braking system according to claim 4 ,
wherein the pressure-increase linear valve comprises a characteristic in which the pressure-increase linear valve is in an open state when the hydraulic pressure in the control pressure chamber is less than an opening and closing switching pressure in a state in which the current to be supplied to the coil of the pressure-increase linear valve is kept, and the opening and closing switching pressure is determined by the current to be supplied to the coil of the pressure-increase linear valve, and
wherein the control-pressure-chamber stiffness reducer comprises a pressure-increase linear valve controller configured to control the current to be supplied to the coil of the pressure-increase linear valve to increase the opening and closing switching pressure such that the opening and closing switching pressure is greater in the case where the slip control device is in the operating state than in the case where the slip control device is in the non-operating state.

8. The hydraulic braking system according to claim 7 ,
wherein the rear-hydraulic-pressure control device comprises a target hydraulic pressure determiner configured to determine a target hydraulic pressure in the control pressure chamber based on a brake request, and
wherein the pressure-increase linear valve controller comprises a target-hydraulic-pressure-change-based pressure-increase linear valve controller configured to increase the opening and closing switching pressure in the pressure-increase linear valve such that the opening and closing switching pressure in the pressure-increase linear valve is greater when a tendency of the target hydraulic pressure in the control pressure chamber which is determined by the target hydraulic pressure determiner is an increasing tendency than when the tendency of the target hydraulic pressure in the con

Assignees

• Toyota Motor Co Ltd
• Advics Co Ltd

Inventors

• Kamiya Yusuke
• Komazawa Masaaki
• Uchida Kiyoyuki
• Ninoyu Masaki
• Nishio Akitaka
• Maruyama Masaki

Classifications

• F16D61/00

  Brakes with means for making the energy absorbed available for use (F16D57/00 takes precedence) · CPC title

• B60T2270/604

  Merging friction therewith; Adjusting their repartition · CPC title

• B60T13/686

  in hydraulic systems or parts thereof · CPC title

• B60T13/662

  characterised by specified functions of the control system components · CPC title

• B60T13/146

  Part of the system directly actuated by booster pressure · CPC title