Patent Application
20180345928
A way to allow indefinite hold of fluid pressure at wheel ends using existing components of a vehicle braking system is provided.
U.S. Pat. No. 7,780,244 B2 to Inagaki et al. discloses a system utilizing recognition that keeping normally open control valves closed for hours for parking brake purposes is thermally disadvantageous, and proposes primary and secondary valve arrangements in which primary and secondary valves are electrically controlled for placement in half-opened states over extended terms due to changes in driving circuits and coil thermal capacity. Other documents of interest are U.S. Pat. No. 4,568,131 to Blomberg et al., U.S. Pat. No. 6,305,759 B1 to Ho et al., U.S. Pat. No. 6,386,649 B1 to Ross, U.S. Pat. No. 6,741,922 B2 to Holler, U.S. Pat. No. 8,494,745 B2 to Schneider et al., U.S. Pat. No. 8,857,787 B2 to Zula, U.S. Pat. No. 8,869,831 B2 to Haehn et al., U.S. Pat. No. 8,938,346 B2 to Oliveira et al., U.S. Pat. No. 9,031,754 B2 to Matoy et al., Chinese Publication 104097621 A to Foitzik et al. (or its U.S. equivalent, U.S. Patent Application Publication 2014/0306514 A1), U.S. Patent Application Publication 2007/0046098 A1 to Grolle et al., U.S. Patent Application Publication 2011/0233993 A1 to Sakai, and Japanese Publication 2002-178901 to Araki, identifying as its applicant Daihatsu Motor Co. Ltd. Certain additional background information is available from a pair of Bendix Service Data publications, BENDIX WINGMAN ACB (Active Cruise with Braking), SD-13-3333, published May 2012, and BENDIX ESP EC-80 Controller, SD-13-4986, published July 2015.
Advanced driver assistance systems are now required to bring a vehicle to a stop. The duration over which the vehicle must remain stopped may be indefinite. Currently, modulators (i.e. modulator valves or traction valves) used in vehicle braking should only be activated for brief periods of time to prevent thermal damage. Accordingly, one object of the present invention is to provide a simple process for permitting indefinite pressure control of a stopped vehicle. The present invention proposes a way to allow indefinite hold of fluid pressure via modulators by handing off which modulators are active. This operation involves changing activation of front and rear circuits to hold the system in a parked state, and no structural changes are necessary to existing modulator valves. A control strategy for switching off modulators to ensure that no one modulator is in a hold state for longer than is necessary, allowing essentially indefinite pressure control of a stopped vehicle, is realized accordingly.
According to one preferred embodiment, a fluid brake system permitting a vehicle to remain in a stopped condition indefinitely includes a first fluid circuit by which fluid pressure is applicable to brake chambers of a first set of vehicle wheels, as well as a second fluid circuit by which fluid pressure is applicable to brake chambers of a second set of vehicle wheels. An electronic control unit or other such control device is provided to repeatedly alternate fluid pressure application to the brake chambers of the first set of vehicle wheels, without fluid pressure application to the brake chambers of the second set of vehicle wheels, and fluid pressure application to the brake chambers of the second set of vehicle wheels, without fluid pressure application to the brake chambers of the first set of vehicle wheels. In one configuration, the first and second fluid circuits include respective pressure modulator valves providing the fluid pressure application to the brake chambers of the first and second vehicle wheel sets, while in another configuration, the fluid circuits include respective traction valves providing the fluid pressure application to the brake chambers of the vehicle wheel sets.
To assure the vehicle remains stationary, fluid pressure application to the brake chambers of the first set of vehicle wheels and the fluid pressure application to the brake chambers of the second set of vehicle wheels overlap by a predetermined period of time. According to the arrangements particularly described here, this predetermined period of overlap lasts 1-2 seconds, while the fluid pressure application to the brake chambers of the first and second sets of vehicle wheels occurs for periods of 150 seconds or less. The first set of vehicle wheels, for example, may include vehicle drive wheels, while the second set of vehicle wheels may include vehicle steer wheels. An overall vehicle operation process is also described.
The particular fluid brake system 32 for the vehicle 10 shown in
A primary circuit fluid supply line 56 connects the supply reservoir 54 to a rear axle service reservoir 58, which, in turn, is connected by a fluid line 60 to the inlet of an appropriate valve 62, such as a double check valve, having a pair of outlets. One outlet of the valve 62 is interconnected by a fluid line 64 to a relay valve 66, while the other outlet of the valve 62 is interconnected by a fluid line 68 to a drive axle traction control valve 70. As explained by way of example in the Haehn et al. (831) patent mentioned above, the entire disclosure of which is incorporated herein by reference as non-essential material, traction control valves such as the valve 70 normally operate to provide controlled delivery of fluid to service brakes in traction control situations, such as when an excessive torque for given road conditions is commanded by a vehicle operator. The drive axle traction control valve 70 is in fluid communication with the relay valve 66 by way of a line 126.
A secondary circuit fluid supply line 72 connects the supply reservoir 54 to a front axle service reservoir 74, which, in turn, is connected to the inlet of an appropriate valve 76, such as a double check valve, having a pair of outlets. One outlet of the valve 76 is connected by a fluid line 78 to a trailer control valve 80, while the other outlet of the valve 76 is connected by a fluid line 82 to a pedal operated service brake valve 84. The rear axle service reservoir 58 is also connected by way of a fluid line 86 to the pedal operated service brake valve 84. In another example, the first circuit could be connected diagonally, i.e. with a front right wheel plus a rear left wheel connected, and the second circuit could be connected oppositely diagonally, i.e. with a front left wheel plus a rear right wheel connected.
A fluid line 88 interconnects the front axle service reservoir 74, by way of the pedal operated service brake valve 84, to the inlet of an appropriate valve 90, such as a double check valve, having a pair of outlets. One outlet of the valve 90 is connected by a fluid line 92 to an inlet of another appropriate valve 94, while a fluid line 96 interconnects the other outlet of the valve 90 to a steer axle traction control valve 104, similar to the valve 70, leading to a relay valve 98, similar to the valve 66. Fluid is directed from the relay valve 98 both through a fluid line 100 towards the brake chamber 34 associated with the right steer wheel 12 and through a fluid line 102 towards the brake chamber 36 associated with the left steer wheel 14. The steer axle traction control valve 104 operates similarly to the drive axle traction control valve 70 mentioned previously. A right steer axle pressure modulator valve 106 is interposed in the fluid line 100 between the relay valve 98 and the brake chamber 34 associated with the wheel 12, while a left steer axle pressure modulator valve 108 is similarly interposed in the fluid line 102 between the relay valve 98 and the brake chamber 36 associated with the wheel 14. As the Haehn et al. (831) patent mentioned above notes, modulator valves such as the valves 106 and 108 normally control the delivery of fluid pressure to and the exhaust of fluid pressure from respective brake chambers, in this case, the chambers 34 and 36. The Ho et al. (759) and Ross (649) patents mentioned above, the entire disclosures of which are incorporated herein by reference as non-essential material, supply concrete examples of pressure modulator valve structures and operation. Drive axle modulator valves 146 and 150 and additional axle modulator valves 148 and 152, described below, normally operate in the same way as the steer axle pressure modulator valves 106 and 108 to control delivery of fluid pressure to and exhaust of fluid pressure from their respective brake chambers.
An outlet of the pedal operated service brake valve 84 communicates fluid supplied through the line 86 from the rear axle service reservoir 58, via a fluid line 110, to the inlet of an appropriate valve 112, such as a double check valve, having a pair of outlets. One outlet of the valve 112 passes fluid through the line 114 to the drive axle traction control valve 70, while the other outlet of the valve 112 passes fluid through a line 116 leading to a connector 118 for a trailer supply/service line 120. An outlet of the valve 94 similarly communicates via a line 122 with the connector 118 such that, with appropriate operation of the trailer control valve 80, fluid from the front axle service reservoir 74 can pass through the lines 78 and 124, through the valve 94, and to the line 122. As mentioned previously, another outlet of the pedal operated service brake valve 84 communicates fluid supplied from the front axle service reservoir 74 through the line 82, via the line 88, to the valve 90. From the valve 90, fluid passes by way of the fluid line 96 past the traction control valve 104 and the relay valve 98 towards the brake chambers 34 and 36 associated with the steer wheels 12 and 14.
Fluid provided from the rear axle service reservoir 58 through the fluid lines 60 and 64 and/or through the fluid line 86, the service brake valve 84, and the fluid lines 110, 114, and 126 to the relay valve 66 is transmitted, through valves 130 and 132, respectively, to connectors 134 and 136, which feed that fluid to lines 138, 140, 142, and 144. Lines 138 and 140 respectively communicate the connector 134 to the brake chamber 38 and the brake chamber of the arrangement 42, while lines 142 and 144 respectively communicate the connector 136 to the brake chamber 40 and the brake chamber of the arrangement 44. In the fluid line 138, a right drive axle pressure modulator valve 146 is interposed between the connector 134 and the brake chamber 38 associated with the right drive wheel 16, and in the fluid line 140, a right additional axle pressure modulator valve 148 is interposed between the connector 134 and the brake chamber of the arrangement 42 associated with the right additional wheel 20. Similarly, in the fluid line 142, a left drive axle pressure modulator valve 150 is interposed between the connector 136 and the brake chamber 40 associated with the left drive wheel 18, and in the fluid line 144, a left additional axle pressure modulator valve 152 is interposed between the connector 136 and the brake chamber of the arrangement 44 associated with the left additional wheel 22.
The present invention is contemplated as particularly useful in a situation in which the vehicle 10 shown in
Referring now to
At a time t3, the ECU represented in
By way of example only, it is contemplated that once the vehicle 10 is brought to a stop either by an operator or automatically at a time t1, the actual CIRCUIT 1 application interval from t1 to t4 could be a predetermined time, from about 30 seconds up to approximately 150 seconds, the CIRCUIT 1 to CIRCUIT 2 handoff interval from t3 to t4 would be between 1 and 2 seconds, the CIRCUIT 2 application interval from t3 to t6, again, could be the same predetermined time, from about 30 seconds up to approximately 150 seconds, and the CIRCUIT 2 to CIRCUIT 1 handoff interval from t5 to t6, again, would be between 1 and 2 seconds, with this cycle being repeated indefinitely. However, each circuit could be applied for different predetermined times.
When modulator valves are deenergized, they allow pressure pass through. As one modification to the procedure discussed above, instead of controlling the pressure modulator valves 106, 108, 146, 148, 150, and 152 individually as described, the traction control valves could be employed to provide transition. Transition in this case conceivably could be accomplished while removing modulator valve action entirely, e.g. by using the ECU shown in
If, at any time during the routine, motion of the vehicle is detected (e.g. by wheel speed sensors), the routine will be discontinued, and pressure in response to the original deceleration request will be applied to all circuits.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
