Fluidic control system

Abstract

A fluidic control system (1) for controlling a vehicle, which includes a controller (2) and a closed fluidic circuit. The circuit includes a pump (3) for pressurizing fluid in the circuit, valve means (40, 50, 60), an actuator (4, 5, 6) and a precharge accumulator (7). The valve means (40, 50, 60) is fluidly connected to the inlet and outlet of the pump (3) and the actuator (4, 6) is fluidly connected to the valve means (40, 50, 60) for selectively receiving pressurized fluid therefrom. The precharge accumulator (7) includes a movable member (73, FIG. 2) that describes a variable volume (71) fluidly connected to the circuit between the valve means (40, 50, 60) and the inlet of the pump (3). The system (1) also includes a sensor (70) for determining the position of the movable member (73) for estimating the quantity of fluid and/or detecting an abnormal pressure variation within the circuit.

Claims

1. A fluidic control system comprising a controller and a closed fluidic circuit, the fluidic circuit comprising a pump having an inlet and an outlet, a valve assembly operatively connected to the controller and fluidly connected to the inlet and outlet of the pump, an actuator fluidly connected to the valve assembly for selectively receiving pressurised fluid therefrom and a bleed assembly fluidly connected between the valve assembly and the inlet of the pump, wherein the bleed assembly comprises an inlet port for fluidly connecting the inlet of the pump to a source of fluid, an outlet port for fluidly connecting the valve assembly to a discharge reservoir and a shutoff mechanism between the inlet port and the outlet port for selectively opening and closing fluid communication therebetween.

2. System according to claim 1 comprising a precharge accumulator, wherein the valve assembly comprises a high pressure inlet fluidly connected to an outlet of the pump and a low pressure outlet fluidly connected to an inlet of the pump such that the fluidic circuit is closed, the precharge accumulator being fluidly connected between the pump inlet and the low pressure outlet of the valve mechanism for maintaining a predetermined fluid pressure to the pump inlet.

3. System according to claim 2, wherein the precharge accumulator comprises a charging chamber fluidly connected to the fluidic circuit and a movable member for varying the volume of the charging chamber, the charging chamber of the precharge accumulator comprising a chamber inlet fluidly connected to the low pressure outlet of the valve mechanism and a chamber outlet fluidly connected to the pump inlet, the shutoff mechanism being provided at least in part by the movable member which comprises a bleed position in which it blocks the chamber inlet and the chamber outlet.

4. System according to claim 3, wherein the precharge accumulator comprises a sensor for determining the position of the movable member and the controller is configured to detect automatically, from a position of the movable member determined using the sensor, faults and/or leaks within the fluidic circuit by estimating the quantity of fluid within the fluidic circuit and/or by detecting an abnormal pressure variation within the fluidic circuit.

5. System according to claim 3, wherein the system is operable to move the movable member to the bleed position to enable the fluidic circuit to be bled.

6. System according to claim 2, wherein the precharge accumulator comprises a biaser acting on the movable member to generate a pressure in the charging chamber for maintaining the predetermined fluid pressure to the pump inlet.

7. System according to claim 6, wherein the biaser comprises a precharge chamber containing a second pressurised fluid therein.

8. System according to claim 7 comprising a pressure sensor for sensing the pressure within the precharge chamber for determining the position of the movable member and/or for estimating the pressure at the inlet of the pump.

9. System according to claim 6, wherein the biaser comprises a biasing mechanism or spring.

10. System according to claim 1, wherein the actuator comprises a first actuator and the valve assembly comprises a first valve assembly, the fluidic circuit comprising a second actuator fluidly connected to a second valve assembly operatively connected to the controller, the controller being configured to operate, in use, each valve assembly for controlling the supply of pressurised fluid to each actuator for the operation thereof.

11. System according to claim 10 comprising a third valve assembly and a third actuator fluid connected thereto, wherein the third valve assembly is operatively connected to the controller and the controller is configured to operate, in use, the third valve assembly for controlling the supply of pressurised fluid to the third actuator.

12. System according to claim 10, wherein the first actuator comprises a brake actuator for slowing or stopping a vehicle and the second actuator comprises a non-brake actuator.

13. System according to claim 1, wherein the actuator is one of a plurality of vehicle brake actuators, each brake actuator being fluidly connected to a respective first valve assembly, the controller being configured to operate each first valve assembly to control, in use, the supply of pressurised fluid to each brake actuator.

14. System according to claim 1, wherein the actuator comprises connector for mechanical connection to a master cylinder of a fluidic circuit of a vehicle and the controller is configured to operate the valve assembly in order to apply, in use, a mechanical force to the master cylinder.

15. System according to claim 1 comprising an electric motor coupled to the pump and operatively connected to the controller and the controller is configured to operate, in use, the motor to pressurise fluid in the fluidic circuit.

16. System according to claim 15, wherein the pump comprises a fixed displacement pump and the fluidic circuit comprises a pressure sensor downstream of the pump and operatively connected to the controller, the controller being configured to control, in use, the speed of the motor based on a pressure detected by the pressure sensor.

17. System according to claim 1 comprising one or more accumulators fluidly connected between the pump and the valve assembly for storing pressurised fluid.

18. System according to claim 1, wherein the controller is configured to operate a vehicle without driver input.

Description

THE DRAWINGS

(1) Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic representation of a fluidic control system according to an embodiment of the invention;

(3) FIG. 2 is a schematic representation of the bleed assembly of the system of FIG. 1;

(4) FIG. 3 is a schematic representation of the bleed assembly shown in FIG. 2 with the piston of the precharge accumulator shown in a bleed position; and

(5) FIG. 4 is a schematic representation of a fluidic control system according to another embodiment of the invention.

DETAILED DESCRIPTION

(6) Referring now to FIG. 1, there is shown a fluidic control system 1 incorporated into a vehicle 10 having front wheels 11a and rear wheels 11b. The system 1 uses a hydraulic operating fluid in this embodiment, but in certain circumstances that would be appreciated by the skilled person the preferred operating fluid may comprise a gas, such as air, or some other fluid. The vehicle 10 also includes a controller 2, which may be dedicated for controlling the hydraulic control system 1 or may form part of the onboard computer system of the vehicle 10. Whilst illustrated schematically as a single controller 2, it will be appreciated that the function carried out by the controller 2 may be implemented through one or more control units and/or one or more control modules incorporated within one or more such control units and the term “controller” is to be construed accordingly.

(7) The hydraulic circuit 1 includes a fixed displacement pump 3 mechanically coupled to a variable speed, brushless electric motor 30. The motor 30 is electrically connected to an energy storage device 31, a battery 31 in this embodiment, and is operatively connected to the controller 2. In this embodiment, the motor 30 and the battery 31 are both independent of the powertrain of the vehicle 10, although in embodiments it may be advantageous for the motor 30 to be connected to the same energy storage device as a powertrain of the vehicle 10. As such, the motor 30 and pump 3 are dedicated to pressurizing the fluidic control circuit 1 and are therefore sized and configured to be no larger, heavier or more complex than required for this purpose. This arrangement enables the weight of the system 1 to be minimized and the efficiency of the system 1 to be maximized. It will be appreciated that the battery 31 may comprise a lithium-ion, solid-state, lead-acid, nickel metal hydride or molten chloroaluminate sodium battery. Alternatively, the energy storage device 31 may comprise a fuel cell or any other appropriate energy storage device 31.

(8) The hydraulic circuit 1 also includes a first set of actuators 4 each fluidly connected to a respect first valve means 40, a second actuator 5 fluidly connected to a second valve means 50 and a third actuator 6 fluidly connected to a third valve means 60. Each of the valve means 40, 50, 60 is operatively connected to the controller 2. It will be appreciated by the skilled person that the valve means 40, 50, 60 illustrated schematically herein are non-limiting and may be implemented by any number of other valve arrangements. Such valve arrangements may, but need not, include a plurality of individual valves or any other arrangement or mechanism that controls the supply of pressurized fluid to the relevant actuator 4, 5, 6.

(9) In this embodiment, the hydraulic circuit 1 is closed. More particularly, each of the valve means 40, 50, 60 includes a respective high pressure inlet fluidly connected to an outlet of the pump 3 via a respective pressure accumulator 41, 51, 61 and a low pressure outlet fluidly connected to the inlet of the pump 3 via a precharge accumulator 7. Thus, the circuit is divided into a high pressure supply line 32 and a low pressure return line 33. Each pressure accumulator 41, 51, 61 includes a check valve 42, 52, 62 upstream thereof to prevent backflow to the pump 3. Each of the high pressure line 32 and the low pressure line 33 includes a respective pressure sensor 34, 35 for determining a pressure of the hydraulic fluid therein. The pressure sensors 34, 35 are operatively connected to the controller 2. The precharge accumulator 7 also includes a pressure sensor 70 operatively connected to the controller 2.

(10) The controller 2 determines the pressure in the high pressure line 32 using the pressure sensor 34 and controls the speed of the motor 30 to operate the pump 3 in order to maintain the pressure within a predetermined range, thereby to provide closed loop feedback control of the pressure within the system 1.

(11) In this embodiment, the first set of actuators 4 are brake calipers and each of the first valve means 40 is a 4/2 brake control valve 40, in which both of the actuator-side ports supply an inlet of the caliper 4. Each brake control valve 40 includes a first state, in which the high pressure line 32 is fluidly connected to the caliper 4, and a second state, in which the low pressure line 33 is fluidly connected to the caliper 4. The controller 2 is configured to move each brake control valve 40 between its first and second states.

(12) As such, when the controller 2 places the brake control valve 40 in the first state, the caliper 4 applies a braking force to each wheel 11a, 11b by actuating brake pads (not shown) to apply a friction force to brake discs (not shown) in the normal way. When the controller 2 places the brake control valve 40 in the second state, the pressure within the caliper 4 actuation system is relieved. Other arrangements are also envisaged and may be advantageous, for example the valve means 40 may comprise a valve operable to provide a variable pressure of hydraulic fluid to the caliper 4. Moreover, the caliper 4 may be replaced by a drum brake cylinder for actuating a brake shoe to engage a brake drum or any other suitable actuation means.

(13) In this embodiment, the second actuator 5 is a steering actuator and the second valve means 50 is a 4/3 steering control valve 50. The steering actuator 5 includes a piston 53 movable within a cylinder 54, thereby to describe first and second variable volumes 55a, 55b, and a steering arm 56a, 56b mechanically connecting each side of the piston 53 to the front side of one of the front wheels 11a of the vehicle 10. A first of the actuator-side ports of the steering control valve 50 is fluidly connected to the first variable volume 55a and a second of the actuator-side ports of the steering control valve 50 is fluidly connected to the second variable volume 55b. The steering control valve 50 includes first, second and third states and the controller 2 is configured to move the steering control valve 50 between its states.

(14) When the controller 2 places the steering control valve 50 in its first state, the high pressure line 32, the low pressure line 33 and the actuator-side ports are all isolated, the piston 53 is kept stationary and the direction of the front wheels 11 a is maintained. When the controller 2 places the steering control valve 50 in its second state, the high pressure line 32 is fluidly connected to the first variable volume 55a and the low pressure line 33 is fluidly connected to the second variable volume 55b, thereby causing the piston 53 to move to the right and the front wheels 11a to pivot clockwise causing the vehicle change direction toward the right. When the controller 2 places the steering control valve 50 in its third state, the high pressure line 32 is fluidly connected to the second variable volume 55b and the low pressure line 33 is fluidly connected to the first variable volume 55a, thereby causing the piston to move to the left and the front wheels 11a to pivot counter-clockwise causing the vehicle change direction toward the left. Other arrangements are also envisaged and may be advantageous, as will be appreciated by the skilled person. It will be appreciated that the system 1 may incorporate closed loop steering feedback, for example in which one or more sensors are provided for determining one or more of the position of the piston 53 of the steering actuator 5, the pressure in each of the variable volumes 55a, 55b, the position of the front wheels 11a, movement sensors, e.g. accelerometers or GPS receivers, for determining a direction of movement of the vehicle and/or any other feature of the steering system.

(15) In this embodiment, the third brake actuator 6 is a clutch assembly actuator and the third valve means 60 is a 4/2 clutch control valve 60, in which both of the actuator-side ports supply an inlet of the clutch actuator 6. The clutch control valve 60 includes a first state, in which the high pressure line 32 is fluidly connected to the clutch actuator 6, and a second state, in which the low pressure line 33 is fluidly connected to the clutch actuator 6. The controller 2 is configured to move the clutch control valve 60 between its first and second states.

(16) As such, when the controller 2 places the clutch control valve 60 in the first state, the clutch actuator 6 causes the clutch (not shown) to disengage the gearbox (not shown) from the engine (not shown) to enable the gear ratio to be changed in the normal way. When the controller 2 places the clutch control valve 60 in the second state, the pressure within the clutch actuator 6 is relieved. Other arrangements are also envisaged and may be advantageous, for example the valve means 60 may comprise a valve operable to provide a variable pressure of hydraulic fluid to the clutch actuator 6. It will be appreciated that the system 1 may incorporate closed loop clutch feedback, for example in which one or more sensors are provided for determining the position or condition of the clutch actuator 6.

(17) In this embodiment, the precharge accumulator 7 includes a variable volume charging chamber 71 fluidly connected to the low pressure line 33 of the circuit 1 and biasing means 72 acting on the charging chamber 71 to generate a pressure therein for maintaining a predetermined fluid pressure to the inlet of the pump 3. The precharge accumulator 7 includes a movable member in the form of a piston 73, which is movable within a cylinder 74 and describes with the cylinder 74 the charging chamber 71. The biasing means 72 is in the form of a pressurized secondary fluid, air in this embodiment, which is contained within a precharge chamber 75 on the other side of the piston 73 to the charging chamber 71 and acts on the piston 73 to apply a force to the charging chamber 71. The precharge accumulator 7 includes an air inlet 76 for charging or discharging the precharge chamber 75. It will be appreciated that the piston 73 may be replaced by any other suitable movable member, such as a bladder member, and/or the biasing means may be provided by any other suitable means, such as a spring.

(18) The pressure sensor 70 is configured to determine the air pressure within the precharge chamber 75. As such, with the precharge chamber 75 charged to a predetermined pressure, the controller 2 is able to monitor the air pressure based on readings from the pressure sensor 70 during operation of the system 1. This feedback enables the controller 2 monitor the state of the circuit 1. In this embodiment, the controller 2 incorporates a diagnostic module, which analyses pressure readings from all of the pressure sensors 34, 35, 70 on a regular basis. The pressure within the precharge chamber 75 is indicative of the position of the piston 73. As such, this reading may be used to estimate the quantity of hydraulic fluid within the circuit 1. A sustained reduction, or gradual decrease, in pressure within the precharge chamber 75 could therefore indicate a reduction of hydraulic fluid within the circuit 1. The controller 2 is configured to generate an alert or warning if the estimated volume deviates from a predetermined value or range.

(19) As an alternative to, or in addition to, the pressure sensor 70, the precharge accumulator 7 may include a position sensor for detecting directly the position of the piston 73. The pressure sensor 70 and/or position sensor may also be used to estimate the pressure within the low pressure line 33, for example instead of or in addition to the pressure sensor 35.

(20) In this embodiment, the precharge accumulator 7 also forms part of a bleed assembly 8, which includes a bleed inlet port 80, a bleed inlet valve 81, a bleed outlet port 82 and a bleed outlet valve 83. The bleed inlet valve 81 and the bleed outlet valve 83 are both operatively connected to the controller 2 in this embodiment. In other embodiments, these valves 81, 83 are operated manually. The bleed inlet port 80 is fluidly connected to the low pressure line 33 immediately downstream of the charging chamber 71 of the precharge accumulator 7, specifically between the charging chamber 71 and the inlet of the pump 3. The bleed inlet valve 81 selectively opens and closes fluid communication between the low pressure line 33 and the bleed inlet port 80. The bleed outlet port 82 is fluidly connected to the low pressure line 33 immediately upstream of the charging chamber 71 of the precharge accumulator 7 and the bleed outlet valve 83 selectively opens and closes fluid communication between the low pressure line and the bleed outlet port 82.

(21) As shown in FIGS. 2 and 3, the bleed assembly 8 may be operated to bleed the hydraulic system 1 and/or to replace the hydraulic fluid therein. This is achieved by first deactivating the pump 3, placing each of the brake control valves 40 and clutch control valve 60 to their second state, placing the steering control valve 50 in its first state, connecting a discharge reservoir DR to the outlet port 82 and opening the bleed outlet valve 83 to depressurize the low pressure line 33. This reduction in pressure causes the piston 73 to move toward the ports coupled to the low pressure line 33 (to the right in FIGS. 1-3) such that the piston 73 closes off the low pressure line 33, as shown more clearly in FIG. 3. If appropriate, air A may be introduced into the air inlet 76 of the precharge accumulator 7 to cause the piston 73 to seal off the ports.

(22) The bleed inlet port 80 is then connected an external source of fluid FS, the bleed inlet valve 81 is opened, the pump 3 is activated to draw fluid from the fluid source FS and the control valves 40, 50, 60 are operated to create fluid flow through the circuit 1 to bleed the hydraulic system 1 and/or to replace the hydraulic fluid therein. The bleed outlet valve 83 may then be closed whilst the system 1 continues to be operated in order to re-pressurize the low pressure line 33. Additionally or alternatively, at least some of the air 72 in the precharge chamber 75 of the precharge accumulator 7 may be evacuated to allow the charging chamber 71 to refill with hydraulic fluid and, if appropriate, air A may be re-introduced thereafter to bring the precharge chamber 75 back to the predetermined pressure for normal operation. It will be appreciated that several variations to this method are envisaged and may be preferable. Moreover, a separate shutoff means, e.g. a valve, may be provided instead of using the precharge accumulator 7 to close off the low pressure line 33.

(23) The skilled person will appreciate from the aforementioned disclosure that the system 1 of the present invention enables the use of a common fluidic circuit for the operation of both the brakes and one or more other actuation systems, which makes use of the advantages of fluidic control systems whilst benefiting from the efficiencies derived from the aforementioned integration of multiple control systems. The present invention also provides a simple, inexpensive and efficient means of generating pressure within the system on demand and independent of, for example, the operation of the powertrain of the vehicle. The actuator may comprise a brake actuator or a non-brake actuator. The present invention further enables the fluid in the fluidic system to be bled and/or replaced easily and effectively and is able to estimate the quantity of fluid within the circuit and/or detect an abnormal pressure variation within the circuit. Several other advantages will be apparent to the skilled person.

(24) Referring now to FIG. 4, there is shown a hydraulic control system 100 similar to the system 1 of FIGS. 1 to 3, wherein like references depict like features that will not be described herein. The hydraulic control system 100 according to this embodiment differs from that of the previous embodiment in that each of the brake actuators 4 and clutch actuator 6 is operated via a secondary fluidic circuit.

(25) The hydraulic control system 100 includes a brake master cylinder actuator 104 and a clutch master cylinder actuator 106 each fluidly connected to the high and low pressure lines 32, 33 via a respective control valve 140, 160. Each master cylinder actuator 104, 106 is mechanically connected to or integral with a respective master cylinder 141, 161 that selectively pressurizes the secondary fluidic circuit. Each control valve 140, 160 is operatively connected to the controller 2 and is a 4/3 control valve similar to the steering control valve 50. Each master cylinder actuator 104, 106 includes a piston movable within a cylinder to describe first and second variable volumes, similar to the steering actuator 5. The piston of each master cylinder actuator 104, 106 is connected to the master cylinder 141, 161 such that movement of the piston causes the master cylinder 141, 161 to selectively pressurize or depressurize the secondary fluidic circuit.

(26) More particularly, a first of the actuator-side ports of each of the control valves 140, 160 is fluidly connected to the first variable volume of the master cylinder actuator 104 and a second of the actuator-side ports thereof is fluidly connected to the second variable volume. Each control valve 140, 160 includes a first state in which the high pressure line 32, the low pressure line 33 and the actuator-side ports are all isolated. Each control valve 140, 160 also includes a second state in which the high pressure line 32 is fluidly connected to one side of the piston of the master cylinder actuator 104 to cause the master cylinder 141, 161 to pressurize the secondary fluidic circuit. Each control valve 140, 160 also includes a third state, in which the low pressure line 33 is fluidly connected to the other side of the piston to cause the master cylinder 141, 161 to depressurize the secondary fluidic circuit.

(27) Thus, the invention also enables conventional brake circuits and clutch circuits to be operated by the fluidic circuit 100. As such, the versatility of the present invention is such that existing vehicles may be retrofitted with a fluidic control circuit 100 according to the invention. The present invention also facilitates the integration of autonomous or semi-autonomous functionality in existing vehicle systems.

(28) Indeed, it is envisaged that the fluidic system 1, 100 of the invention may be particularly useful in an autonomous or semi-autonomous vehicle 10. The system 1, 100 or controller 2 may be configured to control or operate the vehicle 10, e.g. one or more functions thereof, at least partially independent of driver input, for example autonomously or semi-autonomously. The system 1, 100 or controller 2 may be configured to operate one or more, for example each, valve means 40, 50, 60, 140, 160 at least partially independent of driver input. The system 1, 100 or controller may be incorporated into an autonomous or semi-autonomous vehicle control system.

(29) It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, the fluidic circuit 1, 100 and/or the secondary fluidic brake and/or clutch circuits of the fluidic circuit 100 of FIG. 4 may comprise a gas or pneumatic operating fluid. In addition, the system 1, 100 may comprise one or more additional valve means and/or one or more additional actuators, e.g. non-brake actuators. The controller 2 may be configured to operate, in use, the or each additional valve means, e.g. for controlling the supply of pressurized fluid to the or each additional actuator. The additional actuators may include any one or more of a gear shift actuator for changing a gear ratio of the vehicle, a torque vectoring actuator for varying the torque to one or more wheels of the vehicle, a suspension actuator for changing a suspension characteristic of the vehicle, an aerodynamic or aerofoil actuator for moving an aerodynamic element of the vehicle and an auxiliary actuator.

(30) It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.