GB2283289A

GB2283289A - Immobilising valve for a vehicle hydraulic brake circuit

Info

Publication number: GB2283289A
Application number: GB9320834A
Authority: GB
Inventors: David Bramley; Peter Robert Wayman
Original assignee: BRAMLEY DAVID ENG Ltd
Current assignee: BRAMLEY DAVID ENG Ltd
Priority date: 1993-10-09
Filing date: 1993-10-09
Publication date: 1995-05-03
Also published as: GB9320834D0

Abstract

A valve (10) for use in a hydraulic braking circuit of a vehicle as an immobiliser comprises: a housing (12) including a first port (14) for connection to the master cylinder of a braking circuit, and a second port (16) for connection to at least one wheel cylinder of the braking circuit; a first valve means (28, 30) disposed in a first major passage (18) connecting the first and second ports and rotated by the locking and unlocking of a key-operated lock, the first valve means (as shown) being operable when the lock is locked to block only liquid flowing along the first major passage (18) from the second port (16) to the first port (14), and when the lock is unlocked to permit bidirectional liquid flow along the first major passage (18); and a first bleed-back means including a path (42) along which liquid can seep from the second port (16) to the first port (14) when the lock is locked. <IMAGE>

Description

HYDRAULIC VALVE The present invention relates to an hydraulic valve for use in an hydraulic braking circuit of a vehicle as an immobiliser.

Aspects of the present invention are given in the appended claims.

Exemplary embodiments of the invention are herein described with reference to the accompanying drawings, in which: Figure 1 shows a valve of the present invention in cross-section in its unlocked state; Figure 2 shows the valve of Figure 1 in its locked state; and Figure 3 shows a valve of the present invention, in use, in a vehicle braking system.

The preferred embodiments of the invention which are hereinafter described are either two or four port valves.

A two port valve of the present invention is generally denoted 10 and featured in Figures 1 and 2. The valve comprises a cylindrical housing 12 having first and second ports 14, 16 which are connected by a first major passage 18. In a central portion 19 of the first major passage 18, the housing is shaped such that the first major passage is generally cylindrical shaped. The valve 10 further comprises a cylindrical body portion 20 which is mounted for rotation in the central portion 19 of the first major passage 18. The body portion 20 includes first and second intersecting channels 22, 24 and can be rotated by the locking or unlocking of a key-operated lock, which is not illustrated but forms part of the valve 10, such that either, as in Figure 1, the first channel 22 is colinear with the first major passage 18 or, as in Figures 2, the second channel 24 is co-linear with the first major passage 18.

Within the second channel 24, a first valve means in the form of a oneway check valve comprising a spring 28 and associated ball 30. A seat 26 is provided to co-operate with the ball 30 as shown in Figure 2.

The valve 10 also includes a first bleed-back means 40. The bleed-back means includes a first minor passage 42 having both its end portions 42a, 42b in communication with the first major passage 18. The portion 42c of the passage intermediate the end portions 42a, 42b houses a bleed plug 44 having a conical nose 45. The bleed plug 44 is mounted for radial movement in the portion 42c of the passage 42 on screw threads 46. By adjusting the radial position of the plug 44 the extent of penetration of the nose 45 into the end portion 42a can be altered, whereby the amount of liquid which can seep between the nose 45 and the end portion 42a can be controlled.

The four port valve, mentioned earlier, effectively comprises two of the two port valves axially spaced from one another and housed in the same cylindrical housing 12. The housing 12 thus also includes third and fourth ports; a second major passage connecting the third and fourth ports, the valve further comprising a second valve means disposed in the second major passage, the second valve means being operable when the lock is locked to block only liquid flowing along the second major passage from the fourth port to the third port and when the lock is unlocked to permit bidirectional liquid flow along the second major passage, the valve further comprising a second bleed-back means including a second minor passage which has both its end portions in communication with the second major passage, the second minor passage defining a path along which liquid can seep from the forth port to the third port when the lock is locked. The first major and minor passages are isolated from the second major and minor passages using seals (not shown). In the four port valve, the single lock serves to rotate both the first and second body portions, each valve means being in its locked or unlocked position at the same time.

In order explain the operation of the present invention, Figure 3 shows a four port valve fitted into a conventional dual circuit braking system.

The system comprises a tandem master cylinder 100 including a pedal 102, each fluid output 104,106 being connected to two wheel cylinders 108,110,112,114 via an automatic braking system (ABS) 116, if one is fitted. The operation of such a system ( without the valve of the present invention ) is well known to the man skilled-in-the-art and so need not be described in detail here. However, by way of brief summary, when the pedal 102 is depressed, the two pistons within the master cylinder are actuated causing the fluid pressure in each fluid output 104,106 to increase, which pressurises the respective wheel cylinders 108,110,112,114 and activates the brakes. On releasing the pedal, the pressure in each fluid output 104,106 falls and the wheel cylinders are depressurised, thereby releasing the brakes.

The valve 10, in this case a four port valve, is fitted to the hydraulic braking system as shown in Figure 3, the first port being connected to the fluid outlet 104, the third port being connected to fluid outlet 110, the second port 16 being connected to the wheel cylinders 108,110 and the fourth port being connected to the wheel cylinders 112,114.

As the four port valve, as previously explained, effectively comprises two two port valves which operate in an identical manner, the operation of only one of the two port valves will be discussed in detail.

When the valve is unlocked, as shown in Figure 1, it will be appreciated that fluid from the master cylinder 100 can flow unhindered along the first major passage 18 and thus the operation of the wheel cylinders and hence the braking performance is completely normal.

When the lock is locked using the key, the valve adopts the Figure 2 configuration. On depressing the pedal 102, it can be seen that fluid from the master cylinder 100 passes along the first major passage 18 from the first port 14 to the second port 16, and thus through the first valve means 28,30, and pressurises the wheel cylinders 108,110 thereby locking the brakes. On releasing the pedal 102, fluid is blocked from passing along the first major passage 18 from the second port 16 to the first port 14 keeping the wheel cylinders 108,110 pressurised and thus the brakes locked.

The only way fluid can then pass from the wheel cylinders 108, 110 back to the master cylinder 100 is through the first minor passage 42. The fluid passes between the body portion 20 and the housing 12 into the end portion 42a of the first minor passage 42 and then seeps between the very small gap between the bleed plug nose 45 and the end portion 42a, thence back to the master cylinder 100.

The time taken for sufficient fluid to seep past the bleed plug nose 45 in this manner to release the brakes is controlled by the position of the bleed plug 44. Screwing the plug inwardly reduces the fluid flow rate and increases the length of time the wheel cylinders remain under pressure and screwing the plug outwardly increases the flow rate, decreasing the time the wheel cylinders are pressurised.

From the foregoing, it will be appreciated that once the valve is locked and the brake pedal 102 depressed, the brake cylinders remain pressurised for a time dependant on the setting of the bleed plug 44. This means that for this pre-set time, the brakes are locked on thereby preventing any attempt to drive or tow the vehicle without first unlocking the valve 10.

After this period, the brake cylinders are depressurised and the brakes released. However, while the valve remains locked, one actuation of the brakes will again lock on the brakes for the pre-set time period.

An advantage of the present invention is that it immobilises a vehicle without continually applying the brakes, which is generally understood as being undesirable.

The pre-set time period can be, for example, one hour or as long as forty eight hours.

It is preferred that the pre-set time period is set and sealed in the manufacture's factory to prevent tampering.

In addition, the valve may incorporate an electrical device to cut the power to the starter circuit and set an LED flashing on the dashboard as a warning that the vehicle is immobilised when the valve is locked. This has two functions (i) as an additional hurdle to be overcome by a would-be thief and (ii) as a means to prevent accidental attempts to drive away whilst the brakes are locked on by the authorised driver of the vehicle.

The valve may include additional electrical devices which allow it to be interfaced with any alarm and/or electrical immobiliser. Preferably, when the valve is set in either the locked or unlocked positions, the key is ejected and may not be left in the lock - in this way preventing accidental switching.

Claims

1. A valve for a hydraulic braking circuit of a vehicle comprising: a housing including a first port for connection to the master cylinder of a braking circuit; a second port for connection to at least one wheel cylinder of the braking circuit; and a first major passage connecting the first and second ports; a first valve means disposed in the first major passage; a lock, the first valve means being operable when the lock is locked to block only liquid flowing along the first major passage from the second port to the first port, and when the lock is unlocked to permit bidirectional liquid flow along the first major passage, the valve further comprising; a first bleed-back means including a first minor passage which has both its end portions in communication with the first major passage, the first minor passage defining a path along which liquid can seep from the second port to the first port when the lock is locked.

2. A valve as in Claim 1, including a body portion mounted for rotation in the first major passage, the body portion having first and second intersecting channels, the first valve means being disposed in the second channel, the body portion being rotated by the activation of the lock such that either the first or second channel extends between the first and second ports.

3. A valve as in Claim 1 or 2, wherein the first valve means comprises a spring and ball.

4. A valve as in any preceding claim, wherein the end portion of the first minor passage adjacent the second port is adjacent the body portion.

5. A valve as in any preceding claim, wherein the bleed-back means includes a bleed-plug which is located in the first minor passage and controls the rate of liquid flow therethrough.

6. A valve as in Claim 1, wherein the housing includes a third port for connection to the master cylinder, a fourth port for connection to at least one wheel cylinder; and a second major passage connecting the third and fourth ports, the valve further comprising a second valve means disposed in the second major passage, the second valve means being operable when the lock is locked to block only liquid flowing along the second major passage from the fourth port to the third port and when the lock is unlocked to permit bidirectional liquid flow along the second major passage, the valve further comprising a second bleed-back means including a second minor passage which has both its end portions in communication with the second major passage, the second minor passage defining a path along which liquid can seep from the forth port to the third port when the lock is locked, the first major and minor passages being isolated from the second major and minor passages.

7. A valve constructed, arranged and adapted to operate substantially as herein described in conjunction with the accompanying drawings.