Device for determining the state of a vehicle's center of gravity and vehicle behavior control system

Abstract

Vehicle center of gravity state determination device (1) comprising: a load-sensitive proportional valve (LSPV) (26) configured to change a rear wheel brake pressure according to a rear axle load; a front wheel brake pressure sensor (27) configured to detect a brake pressure of a front wheel; a rear wheel brake pressure sensor (28) configured to detect a brake pressure of the rear wheel on a side downstream of the load-sensitive proportional valve (LSPV) (26); a rear axle load estimation unit (3) as part of an ECU configured to estimate a rear axle load, characterized in that the rear axle load estimation unit (3) as part of an ECU estimates the rear axle load on the basis of a relationship between front and rear brake pressures detected during braking and a rear axle load characteristic of the load-sensitive proportional valve (LSPV) (26);and by a vehicle center of gravity state determination device as part of an ECU (3) configured to determine a center of gravity state of a vehicle in a vehicle width direction based on the estimated rear axle load, wherein the rear axle load estimation unit as part of an ECU (3) is configured to estimate each of the rear axle loads in a case in which braking is performed in one of at least two states, including straight-ahead driving, right-turn driving and left-turn driving.

Description

Area The present provision relates to a device for determining the state of a vehicle's center of gravity, a vehicle behavior control system, and a method for determining the state of a vehicle's center of gravity that determines the state of a vehicle's center of gravity. background Vehicle behavior control (VSC) systems, which control a vehicle's behavior by controlling or regulating at least the braking force, operate under the assumption that the vehicle's center of gravity, one of the parameters determining a controlled variable, is constant. Among vehicles, there is a loaded vehicle whose load varies significantly between a light load and maximum load, and whose center of gravity position shifts between the front and rear of the vehicle. Even if the vehicle behavior control for such a loaded vehicle is performed under the assumption that the center of gravity position is constant, there is a possibility that the provision of sufficient control power will fail. Traditionally, considering the change in the vehicle's center of gravity from front to rear caused by the load change between light and maximum load, a device is used to perform brake power control. For example, as disclosed in JP 2010-284 990 A, a device performs brake power control to increase the proportion of rear brake power distributed when the rear brake power reaches the ideal front-to-rear brake power distribution for light loads, provided the rear wheel is not slipping. EP 2 069 171 B1 discloses a device according to the preamble of claim 1 and a method according to the preamble of claim 4. A system according to claim 3 comprises the device according to claim 1. Brief explanation Technical problem In a loaded vehicle, luggage or cargo can be arranged at any given position not only in a front-to-rear direction but also in a width-to-width direction. Consequently, the position of the center of gravity changes along the vehicle's front-to-rear and longitudinal directions, as well as along its width, depending on the position of the loaded goods. The vehicle behavior control system, which includes brake performance control, must be a system that takes the center of gravity's position in the width-to-width direction into account. The present invention was carried out in view of the circumstances described above, and it is an object of the present invention to provide a device for determining a state of a vehicle center of gravity, a vehicle behavior control system and a method for determining a state of a vehicle center of gravity in order to be able to determine a state of a center of gravity position in the vehicle width direction. Solution to the problem To solve the problem explained above and to achieve the result described above, a device for determining the state of the vehicle's center of gravity according to the present invention comprises the following: a rear wheel brake pressure change unit configured to change a rear wheel brake pressure to match a rear axle load; a front wheel brake pressure detector configured to detect a brake pressure of a front wheel; a rear wheel brake pressure detector configured to detect a brake pressure of the rear wheel on a downstream side of the orto detect the rear brake pressure change unit; a rear axle load estimation unit designed to estimate a rear axle load based on a relationship between front and rear brake pressures detected during braking and a rear axle load characteristic of the rear brake pressure change unit; and a vehicle center of gravity state determination device designed to determine a vehicle center of gravity state in a vehicle width direction based on the estimated rear axle load. The rear axle load estimation unit is designed to estimate each of the rear axle loads in a case where braking is performed in one of at least two states, including straight-ahead driving, right-turning driving, and left-turning driving. Furthermore, in the vehicle center of gravity state determination device, it is preferable that the center of gravity state of the vehicle in the vehicle width direction is a magnitude of the displacement of a center of gravity position of a vehicle in the vehicle width direction, the rear axle load estimation unit is designed to estimate the rear axle loads in a case in which braking is carried out in a state during a left turn and during a right turn, as the respective first rear axle load and second rear axle load, and the vehicle center of gravity state determination device is designed to estimate the magnitude of the displacement of the center of gravity position of the vehicle in the vehicle width direction due to the first rear axle load and the second rear axle load. Furthermore, a vehicle behavior control system according to the present invention comprises the following: the vehicle center of gravity state determination device described above; and a vehicle behavior control system designed to control or regulate at least the braking performance based on the center of gravity state of the vehicle in the vehicle width direction in order to control or regulate vehicle behavior. Furthermore, a vehicle center of gravity state determination method according to the present invention comprises the following: a step of changing a rear wheel brake pressure depending on a rear axle load; a step of detecting a brake pressure for a front wheel; a step of detecting a brake pressure for a rear wheel on a downstream side with respect to or behind a rear wheel brake pressure change unit, wherein the rear wheel brake pressure change unit is configured to change a brake pressure for the rear wheel depending on the rear axle load; a step of estimating a rear axle load based on a relationship between front and rear brake pressures detected during braking and a rear axle load property of the rear wheel brake pressure change unit; and a step of determining a center of gravity state of a vehicle in a vehicle width direction based on the estimated rear axle load.The rear axle load is estimated in a case where braking is performed in one of at least two states, including driving straight ahead, turning right and turning left. Advantageous effects of the invention The vehicle center of gravity state determination device and the vehicle center of gravity state determination method according to the present invention create an advantageous effect that can determine the center of gravity state of a vehicle in a vehicle width direction with a simple setup. The vehicle behavior control system according to the present invention can control or regulate vehicle behavior based on a detected center of gravity state of the vehicle in the vehicle width direction. Accordingly, the vehicle behavior control system creates an advantageous effect of ensuring suitable control or regulation of the vehicle behavior even if the center of gravity state of the vehicle changes in the vehicle width direction. Brief explanation of the characters Fig. 1 illustrates an exemplary setup of a vehicle comprising a vehicle center of gravity state determination device according to a first embodiment. Fig. 2 illustrates a relationship between front wheel brake pressure, rear wheel brake pressure, and load capacity or load. Fig. 3 is a flowchart illustrating a method for determining a vehicle center of gravity state using the vehicle center of gravity state determination device according to the first embodiment. Fig. 4 illustrates a relationship between front wheel brake pressure, rear wheel brake pressure, and rear axle load with a centered load. Fig. 5 illustrates a relationship between front wheel brake pressure, rear wheel brake pressure, and rear axle load with a left-biased load.Figure 6 illustrates a relationship between the front brake pressure, the rear brake pressure, and the rear axle load under a right-biased load. Figure 7 is a flowchart of a vehicle behavior control procedure of a vehicle behavior control system according to a second embodiment. Explanation of embodiments With reference to the accompanying figures, a description of various configurations (embodiments) illustrating the present invention is now given. The contents of the embodiments described below do not limit the invention. The essential elements described below include those essential elements that are obviously equivalent to those skilled in the art, or the so-called equivalence range thereof. Furthermore, the configurations described below can be suitably combined. Various omissions, additions, or modifications disclosed herein can be implemented without departing from the fundamental concept of the present invention. First embodiment A vehicle center of gravity state determination device 1 according to the first embodiment is described below. Fig. 1 illustrates an exemplary setup of a vehicle comprising a vehicle center of gravity state determination device according to one embodiment. Fig. 2 illustrates a relationship between front wheel brake pressure, rear wheel brake pressure, and load capacity or load. Fig. 3 is a flowchart illustrating a method for determining a vehicle center of gravity state of the vehicle state determination device according to the embodiment. Fig. 4 illustrates a relationship between the front wheel brake pressure, the rear wheel brake pressure, and a rear axle load with a centered load. Fig. 5 illustrates a relationship between the front wheel brake pressure, the rear wheel brake pressure, and the rear axle load with a left-side load.Figure 6 illustrates a relationship between the front brake pressure, the rear brake pressure and the rear axle load when loaded on the right side. This embodiment describes the case in which a loading platform 11 is arranged at the rear of the vehicle and the vehicle center of gravity state determination device 1 is arranged in a truck 10, such as a lorry, van, delivery truck, garbage truck, or the like, which can load goods 12 onto the loading platform 11. However, this should not be considered a limitation. The vehicle center of gravity state determination device 1 is applicable to all vehicles as long as the vehicle has a rear wheel brake pressure modulation unit. The rear wheel brake pressure modulation unit changes the brake pressure at the rear wheel according to a rear axle load described later. In the following description, "right and left" corresponds to right and left in the vehicle width direction as seen from the front of the truck 10. The vehicle center of gravity state determination device 1 comprises an LSPV or load-sensitive proportional valve 26, a front wheel brake pressure sensor 27 and a rear wheel brake pressure sensor 28, which are contained in a brake device 2, and an ECU 3. The braking device 2 generates the braking force in the truck 10 and is described in this embodiment as a hydraulic braking device. However, this should not be understood as a limitation. The braking device 2 can also be a hydropneumatic or a pneumatic braking device. The braking device 2 comprises a master cylinder 21, a brake actuator 22, right and left front wheel tubes or lines 23R and 23L, right and left rear wheel tubes or lines 24R and 24L, wheel cylinders 25FL, 25FR, 25RL and 25RR, each arranged to match wheels 13FL, 13FR, 13RL and 13RR, the LSPV 26, the front wheel brake pressure sensor 27, the rear wheel brake pressure sensor 28 and a brake ECU (not illustrated). The master cylinder 21 generates fluid pressure in response to a driver actuation of the brake pedal. The master cylinder 21 then supplies this fluid pressure to the wheel cylinders 25FR to 25RL via the right and left front wheel lines 23R and 23L, respectively, and the right and left rear wheel lines 24R and 24L. The master cylinder 21 includes a master cylinder pressure sensor 21a. The master cylinder pressure sensor 21a detects the fluid pressure, specifically the master cylinder pressure Pm. The master cylinder pressure sensor 21a outputs the detected master cylinder pressure Pm to the electrically coupled or connected brake ECU and ECU 3. The fluid pressure can be generated directly by the pedal force applied when the brake pedal is actuated. Alternatively, the fluid pressure can be generated indirectly, corresponding to the degree of brake pedal actuation. The brake actuator 22 can individually (right and left front wheels 13FR and 13FL and right and left rear wheels 13RR and 13RL, right front and rear wheels 13FR and 13RR and left front and rear wheels 13FL and 13RL, one left front wheel and one right rear wheel 13FL and 13RR, or one right front wheel and one left rear wheel 13FR and 13RL) or independently adjust the braking force generated at the respective wheels 13FR to 13RL for vehicle stability control (VSC) regulation, which is a slip suppression control by the ECU 3 and the like, and for anti-lock braking system (ABS) regulation, which is a brake slip suppression control by the brake ECU. The brake actuator 22 is arranged between the master cylinder 21 and the respective wheel cylinders 25FL to 25RR. The brake actuator 22 is coupled to the wheel cylinders 25FL on the side of the left front wheel by a left front wheel tube or a left front wheel line 23L.The brake actuator 22 is coupled to the wheel cylinder 25FR on the right side of the front wheel via a right front wheel tube or line 23R. The brake actuator 22 is coupled to the wheel cylinder 25RL on the left side of the rear wheel via a left rear wheel tube or line 24L. The brake actuator 22 is coupled to the wheel cylinder 25RR on the right side of the rear wheel via a right rear wheel tube or line 24R. The brake actuator 22 comprises an oil pump, an oil reservoir, and various valves (not illustrated) (a fluid holding valve, a pressure reducing valve, and the like). The brake actuator 22 can regulate a cylinder pressure Ps, which is the pressure of each of the wheel cylinders 25FL to 25RR, to adjust the braking performance individually or independently as described above. Here, in normal operation, that is, in a state where the brake power control, the VSC control, or...- If the ABS control and the like are not carried out, the brake actuator 22 supplies the wheel cylinders 25FR and 25FL on the right and left sides of the front wheels with a front wheel brake pressure Pf (the cylinder pressure Ps on the right and left sides of the front wheels) and can supply the wheel cylinders 25RR and 25RL on the right and left sides of the rear wheels with a rear wheel brake pressure Pr (the cylinder pressure Ps on the right and left sides of the rear wheels) such that a brake power distribution to the right and left front wheels 13FR and 13FL and the right and left rear wheels 13RR and 13RL becomes a predetermined distribution. Wheel cylinders 25FL to 25RR are located on the respective wheels 13FL to 13RR. These wheel cylinders are hydraulic actuators that drive a braking mechanism which generates the braking force. The braking mechanism is, for example, a disc brake mechanism consisting of a brake disc and a brake pad, or a drum brake mechanism. The load-sensitive proportional valve (LSPV) 26 is a rear brake pressure modulating unit. The LSPV 26 modifies the rear brake pressure Pr according to the rear axle load WR, that is, it changes the brake force distribution to the right and left front wheels 13FR and 13FL and the right and left rear wheels 13RR and 13RL according to a rear axle load WR. The LSPV 26 is located between the brake actuator 22 and the wheel cylinders 25RL and 25RR on the rear wheel side. The LSPV 26 controls a flow rate to the rear right and left wheel lines 24R and 24L to change the rear brake pressure Pr. Here, the rear axle load of the truck 10 changes when the goods 12 are loaded onto the loading platform 11. Furthermore, the distance between the right and left rear wheels 13RR and 13RL and the loading platform 11 is smaller compared to a state in which the loaded goods 12 are not loaded onto the loading platform 11.Even when a passenger or occupant sits in the driver's seat and the front passenger seat of the truck 10, the front wheel load changes, but the rear wheel load hardly changes. The LSPV 26 is, for example, arranged between a vehicle body and a (not illustrated) rear axle. Due to a change in the distance between the vehicle body and the rear axle corresponding to the load of the goods 12 loaded onto the loading platform 11, i.e., the change in the rear wheel load, the LSPV 26 regulates the flow rate at the right and left rear wheel lines 24R and 24L, and changes the rear wheel brake pressure Pr. As illustrated in Fig. 2, the LSPV 26 creates a setting such that the change in the rear wheel brake pressure Pr to the front wheel brake pressure Pf (brake distribution or...)The brake pressure distribution from front to rear (for the first half of the cycle) remains constant from the moment the brake pressure is generated until the front brake pressure Pf, depending on a load capacity L, reaches an arbitrarily defined change point. If the front brake pressure Pf exceeds this arbitrarily defined change point, depending on the load capacity L, the LSPV 26 creates a setting such that the distribution differs from the front-to-rear brake pressure distribution for the first half of the cycle (brake distribution or front-to-rear brake pressure distribution for the second half). The front-to-rear brake pressure distribution for the second half is adjusted so that the magnitude of the change in the rear brake pressure Pr relative to the change in the front brake pressure Pf is smaller than the front-to-rear brake pressure distribution for the first half of the cycle.Accordingly, the braking power increases the ground contact pressure of the right and left front wheels 13FR and 13FL on the road surface in the case of a high master cylinder pressure Pm, that is, in the braking condition in which the driver depresses the brake pedal firmly. Furthermore, the ground contact pressure of the right and left rear wheels 13RR and 13RL on the road surface decreases. This may lead to slippage of the right and left rear wheels 13RR and 13RL in the front-to-rear brake pressure distribution for the first half. Therefore, the LSPV 26 sets the front-to-rear brake pressure distribution, in which the rear wheel brake pressure Pr decreases, in the brake pressure distribution for the second half from front to rear, thereby limiting the slippage of the right and left rear wheels 13RR and 13RL. The front wheel brake pressure Pf at the arbitrarily defined change point is adjusted according to the load capacity.The load L increases in conjunction with an increase in the load capacity L, for example, in the following order: from the low load (L = min), 50% of the maximum load (L = 0.5), 75% of the maximum load (L = 0.75), and the maximum load (L = max = 1). However, the magnitude of the change in rear brake pressure Pr relative to the change in front brake pressure Pv remains constant, regardless of the load capacity L. The LSPV 26 can be positioned in the center, on the left side, or on the right side of the vehicle's width. In this embodiment, the LSPV 26 is positioned in the center (approximately at the midpoint).In the case where the LSPV 26 is located on the left or right side, the distance between the right and left rear wheels 13RR and 13RL and the loading platform 11 is greater when roll occurs due to cornering to the right and left, compared to the case where the LSPV 26 is located in the center of the vehicle's width direction. This allows for a greater change in the estimated rear axle load WR during braking. The front brake pressure sensor 27 is a front brake pressure detector for detecting the front brake pressure Pf. In this embodiment, the front brake pressure sensor 27 is arranged in the center of the left front brake line 23L, as illustrated in Fig. 1. The front brake pressure sensor 27 detects the cylinder pressure Ps of the wheel cylinder 25FL on the left front wheel side as the front brake pressure Pf. The front brake pressure sensor 27 outputs the detected front brake pressure Pf to the brake ECU and the ECU 3. The front brake pressure sensor 27 can be arranged in the center of the right front brake line 23R or installed upstream of or near the brake actuator 22. The front brake pressure sensor 27 can detect one or both cylinder pressures Ps of the wheel cylinders 25FR and 25FL on the right and left front wheel sides. The rear brake pressure sensor 28 is a rear brake pressure detector used to detect the rear brake pressure Pr. Here, the rear brake pressure sensor 28 is located between the LSPV 26 and the wheel cylinder 25RR on the right rear wheel side, on the right rear brake line 24R. This means that the rear brake pressure sensor 28 is located downstream of the LSPV 26 (the side of the fluid pressure supply, the side opposite the brake actuator 22 and the master cylinder 21, and upstream of the LSPV 26, i.e., the side where the fluid pressure is generated). The rear brake pressure sensor 28 detects the rear brake pressure Pr downstream of the LSPV 26. The rear brake pressure sensor 28 detects the rear brake pressure Pr as it is changed by the LSPV 26. The electronic control unit (ECU) 3 is a control unit for determining the state of the vehicle's center of gravity in the vehicle's width direction. The ECU 3 functions as a rear axle load estimation unit and a vehicle center of gravity state determination device. The ECU 3 estimates the rear axle load WR based on the relationship between the front and rear brake pressures detected during braking and the rear axle load distribution of the LSPV 26. In this embodiment, the ECU 3 estimates the rear axle load WR based on the relationship between the front and rear brake pressures detected during braking, the load capacity L based on the rear axle load characteristic of the LSPV 26, and the rear axle load during an unloaded state, which is predetermined by the specification of the load vehicle 10. The ECU 3 estimates the load capacity L from the relationship between the detected front brake pressure Pf and rear brake pressure Pr, namely the front-to-rear brake pressure distribution, in particular the front-to-rear brake pressure distribution in the second half.The ECU 3 adds the rear axle load during an unloaded state to the estimated load capacity to estimate the rear axle load WR. This is done based on the rear axle load characteristic, when the rear axle load during the unloaded state is added to a load characteristic or loading characteristic of the LSPV 26, which mechanically determines the front-to-rear brake pressure distribution according to the load capacity or loading L (relationship between the front-to-rear brake pressure distribution in the second half and the load capacity L).The ECU 3 estimates the rear axle load WR during braking from at least two states: braking while driving straight ahead (where the vehicle 10 brakes in a straight-ahead state), braking while turning left (where the vehicle 10 brakes while turning left), and braking while turning right (where the vehicle 10 brakes while turning right). This means that the ECU 3 estimates the rear axle load WR in different vehicle driving states during braking. Here, the rear axle load WR changes during braking depending on the loading position of the goods 12 in the vehicle's width direction. This is because, unlike driving straight ahead, the truck 10's right-left turning motion causes it to roll. When the truck 10 rolls, the load on the inside wheel decreases, depending on the direction of travel, which increases the load on the outside wheel. For example, when turning left, the loads on the left front and rear wheels 13FL and 13RL decrease, while the loads on the right front and rear wheels 13FR and 13RR increase. Conversely, when turning right, the loads on the right front and rear wheels 13FR and 13RR decrease, while the loads on the left front and rear wheels 13FL and 13RL increase.This magnitude of the load change varies depending on a center of gravity position Gx in the lateral direction, which is a center of gravity position of the load vehicle 10 in the vehicle width direction, a cornering speed and a cornering radius. For example, during a central load distribution, where the cornering speed and radius are constant and the cargo 12 is loaded in the central section (which includes the approximate center) of the vehicle's width, as illustrated in Fig. 4, the braking effect is somewhat weak compared to straight-line driving with a rear axle load WRS (which is the rear axle load WR during braking while driving straight), a rear axle load WRL during a left turn (which is the rear axle load WR during braking in the left turn), and a rear axle load WRR during a right turn (which is the rear axle load WR during braking in the right turn). This is due to the following reason: With a central load, the influence of the center of gravity position Gx in the width direction is small, even if body roll occurs during right- and left-hand turns.However, the loading platform 11 dips significantly on the outer wheel side of the curve due to an increase in load on the outer wheel. The loading platform 11 rises only slightly on the inner wheel side of the curve due to a reduction in load on the inner wheel. In the center of the vehicle's width, the loading platform 11 dips slightly. During loading on the left side, with constant cornering speed and radius, and the load 12 being loaded on the left side relative to the central section (viewed in the vehicle's width direction), as illustrated in Fig. 5, the load WRL on the rear axle becomes small during left-hand turns compared to the load WRS during straight-ahead driving, while the load WRR on the rear axle becomes large during right-hand turns. This is because, during loading on the left side, the loading platform 11 has already sunk on the left side during straight-ahead driving, as the center of gravity Gx is located on the left side in the width direction. Therefore, the sinking of the loading platform on the side of the outside wheel due to the increased load on the outside wheel is minimal when the roll occurs during the left-hand turn.The loading platform 11 barely rises on the side of the inside wheel due to the reduction in load on that side. The loading platform 11 dips inwards in the middle, across the width of the vehicle. When the roll occurs in a right turn, the loading platform 11 barely dips inwards on the side of the outside wheel due to the increase in load on the outside wheel. The loading platform 11 rises significantly on the inside wheel side due to the reduction in load on that side. The loading platform 11 rises inwards in the middle, across the width of the vehicle. During loading on the right side, with constant cornering speed and radius, and the goods 12 loaded as shown in Fig. 6 on the right side of the central section in the vehicle's width direction, the axle load WRL for the left rear wheel turning becomes large compared to the axle load WRS for the rear wheel traveling straight ahead, and the axle load WRR for the right rear wheel turning ahead becomes small. This is because, during loading on the right side, the loading platform 11 has already sunk on the right side when traveling straight ahead, since the center of gravity position Gx is located on the right side in the width direction. Therefore, the sinking of the loading platform 11 on the outside wheel side of the curve due to the increased load on the outside wheel hardly occurs when the roll occurs during the left turn.The loading platform 11 rises significantly on the side of the inner wheel due to the reduction in load on the inner wheel. The loading platform 11 rises upwards in the center along the vehicle's width. When the roll occurs during a right turn, the sinking of the loading platform 11 on the side of the outer wheel due to the increase in load on the outer wheel is minimal. The rising of the loading platform 11 on the side of the inner wheel due to the reduction in load on the inner wheel is minimal. The loading platform 11 sinks downwards in the center along the vehicle's width. Here, during braking while driving straight ahead, the LSPV 26 is positioned in the center (approximately the center). Accordingly, the center of gravity position Gx in the width direction is almost unaffected by the loading position of the goods 12 in the vehicle's width direction. Therefore, the estimated rear axle load WRS is approximately constant during braking while driving straight ahead.The ECU 3 determines the state of the vehicle's center of gravity in the width direction based on the estimated rear axle load. Based on at least two of the estimated rear axle loads (WRS when driving straight ahead, WRL when turning left, and WRR when turning right), the ECU 3 determines whether the vehicle's center of gravity in the width direction is in a half-loaded state, where the load is either on the left or on the right. For example, the ECU 3 determines the half-loaded state using positive / negative values.The ECU 3 can determine the half-loaded condition by the sign and magnitude of the difference between the rear axle load WRS when driving straight ahead and the rear axle load WRL when turning left, the difference between the rear axle load WRS when driving straight ahead and the rear axle load WRR when turning right, or the difference between the rear axle load WRL when turning left and the rear axle load WRR when turning right.For example, in the case where the vehicle's center of gravity state in the vehicle width direction is determined by the difference between the rear axle load WRL during left-hand turning and the rear axle load WRR during right-hand turning (WRL-WRR), ECU 3 determines that the load state is the center load if the difference is 0 (approximately 0); if the difference is a negative value, ECU 3 determines that the load state is the left-side loaded state, and if the difference is a positive value, ECU 3 determines that the load state is the right-side loaded state. The hardware of the ECU 3 consists of a central processing unit (CPU), which mainly performs arithmetic operations, memory for storing programs and information (RAM or random access memory such as SRAM and read-only memory (ROM) such as an EEPROM), input / output interfaces, and the like. Because the hardware structure is similar to that of an ECU installed in the known truck 10, a detailed description is omitted. The ECU 3 is electrically connected to a drive device 4, which is an internal combustion engine, motor, or the like, installed on the truck 10, and causes drive power or braking power to act on the truck 10, the brake device 2 described above, a steering device, or...The ECU 3 is connected to a steering gear 5, such as an electric power steering (EPS) system, and various sensors arranged in the truck 10, including an accelerator pedal sensor, a brake pedal sensor (not illustrated), and the like. The ECU 3 can receive information from each of the devices 2 and 4 and the device 5, for example, the front wheel brake pressure Pf, the rear wheel brake pressure Pr, and the drive power F. The ECU 3 can also receive vehicle information about the driving state of the truck 10, such as acceleration A and a driving request, a braking request, and the like, from various sensors or the like.Here the ECU 3 is electrically connected to sensors, the front wheel brake pressure sensor 27, the rear wheel brake pressure sensor 28 and the like, and to each of the devices 2 and 4 and the device 5 by a communication system, which is, for example, a typical CAN communication system. The procedure for determining the state of the vehicle's center of gravity by the vehicle center of gravity state determination device according to the first embodiment is described below. Here, the ECU 3 repeatedly performs the procedure for determining the vehicle's center of gravity state in each predefined control cycle. First, as illustrated in Fig. 3, the ECU 3 calculates the gross vehicle weight Wm (step St11). Here, the ECU 3 calculates the gross vehicle weight Wm based on the longitudinal acceleration Afr from the drive power F and the acceleration A of the load vehicle 10, which the ECU 3 receives. Subtracting a vehicle weight W and a weight of the vehicle occupants (a value found by multiplying a number of vehicle occupants, calculated by a (not illustrated) seat sensor, by a predefined weight), which are subtracted from the gross vehicle weight Wm according to the specifications of the load vehicle 10, allows the calculation of an actual load capacity L that is loaded onto the loading platform 11. Next, ECU 3 estimates the straight-ahead rear axle load WRS, which is the rear axle load WR during braking while driving straight ahead (step ST12). Here, ECU 3 estimates the straight-ahead rear axle load WRS based on the front brake pressure Pf and the rear brake pressure Pr when the front brake pressure Pf occurs, where the rear axle load characteristic of the LPSV 26 is based on the calculated load capacity L for front-to-rear brake pressure distribution in the second half, and the rear axle load characteristic of the LSPV 26.This means that during braking while driving straight ahead, ECU 3 determines whether the rear axle load characteristic of the LSPV 26, based on the calculated load capacity L, generates a predefined front brake pressure Pfx that is greater than at the change point where the brake pressure distribution changes from front-to-rear for the first half of the journey to front-to-rear for the second half. If ECU 3 determines that the front brake pressure Pf will be equal to or greater than the predefined brake pressure Pfx, ECU 3 records the current front brake pressure Pf and rear brake pressure Pr to estimate the rear axle load WRS while driving straight ahead.Considering the changes in the rear axle loads WRL and WRR during left and right turns compared to the rear axle load WRS during straight-ahead driving, the value of the pre-defined front brake pressure Pfx is preferably slightly larger than the front brake pressure Pf at the change point, which depends on the calculated load capacity L. Next, ECU 3 estimates the rear axle load WRL during left-hand cornering, which is the rear axle load WR when braking in a left-hand corner (step S13). Here, during braking in a left-hand corner, the ECU determines whether the detected front brake pressure Pf is equal to or greater than the preset front brake pressure. If the ECU determines that the front brake pressure Pf is equal to or greater than the preset front brake pressure Pfx, the ECU detects the current front brake pressure Pf and rear brake pressure Pr. The ECU then estimates the rear axle load WRL in the left-hand corner based on the detected front brake pressure Pf and rear brake pressure Pr and the rear axle load characteristic of the LSPV 26. Next, ECU 3 estimates the rear axle load WRR during a right turn, which is the rear axle load WR during braking in a right turn (step ST14). Here, during braking in the right turn, the ECU determines whether the detected front brake pressure Pfx is equal to or greater than the preset front brake pressure. If the ECU determines that the front brake pressure Pfx is equal to or greater than the preset front brake pressure Pfx, the ECU detects the current front brake pressure Pfx and rear brake pressure Prx. ECU 3 then estimates the rear axle load WRR during the right turn based on the detected front brake pressure Pfx and rear brake pressure Prx and the rear axle load characteristic of the LSPV 26.To estimate the rear axle load WRS during straight-ahead driving, the rear axle load WRL during a left turn, and the rear axle load WRR during a right turn, the conditions regarding cornering speed and cornering radius, apart from the position Gx of the center of gravity in the lateral direction, are preferably equal under the factors that change the loads for the right and left rear wheels 13RR and 13RL (which includes approximately equal). Next, the ECU 3 detects the half-loaded condition based on the estimated rear axle load WRS when driving straight, the rear axle load WRL in a left turn, and the rear axle load WRR in a right turn (step ST15). Here, the ECU 3 determines whether the half-loaded condition occurs or not, based on at least two of the estimated rear axle load WRS when driving straight, the rear axle load WRL in a left turn, and the rear axle load WRR in a right turn.For example, ECU 3 determines from a difference between the rear axle load WRL in the left turn and the rear axle load WRR in the right turn (WRL-WRR) that the load condition is the center load if the difference is 0 (approximately 0); if the difference is a negative value, the ECU determines that the load condition is the left-side loaded condition, and if the difference is a positive value, ECU 3 determines that the load condition is the right-side loaded condition. As described above, the vehicle center of gravity state determination device 1, according to the embodiment, estimates each of the rear axle loads WRS, WRR, and WRL in the case where braking is performed in one of at least two states, including straight-ahead driving, right-turning driving, and left-turning driving, based on the relationship between the detected front and rear brake pressures Pf and Pr and the rear axle load characteristic of the LSPV 26. The vehicle center of gravity state determination device 1 then determines the half-loaded state, which is the center of gravity state of the vehicle in the vehicle width direction, based on the estimated rear axle loads WRS, WRR, and WRL. This allows the half-loaded state to be determined based on the characteristics of the existing device mounted on the loaded vehicle 10.This allows the determination of the half-loaded condition with a simple setup, which makes it possible to attract the driver's attention and to implement vehicle behavior control based on the half-loaded condition. Second embodiment A vehicle behavior control system according to the second embodiment is described below. Fig. 7 is a flowchart of the vehicle behavior control procedure of a vehicle behavior control system according to a second embodiment. The vehicle behavior control system according to the second embodiment is essentially structured as follows. The vehicle behavior control system is structured such that it includes vehicle behavior control, wherein in this embodiment the vehicle behavior control comprises at least the brake device 2, which controls the braking performance, the drive device 4, the steering device 5, or the like in the vehicle center of gravity state determination device according to the first embodiment. The ECU 3 functions as a vehicle behavior control system. This means that, in this embodiment, the ECU 3 controls or regulates the braking force, at least through the brake device 2, based on the vehicle's center of gravity position in the vehicle's width direction, a displacement X, in order to control the vehicle's behavior. The vehicle behavior control system includes VSC control, ABS control, and the like. Since the vehicle behavior control system described here is already generally known, this embodiment omits further explanation. The vehicle behavior control procedure of the vehicle behavior control system according to the second embodiment is described below. In the vehicle behavior control procedure of the vehicle behavior control system according to the second embodiment, the explanation of a process similar to the procedure for determining the state of the vehicle's center of gravity by the vehicle center of gravity state determination device, as in the first embodiment, is omitted or simplified. First, the ECU 3 calculates the gross vehicle weight Wn (step ST21) as illustrated in Fig. 7 and estimates the rear axle load WRS when driving straight ahead (step ST22). Then, the ECU 3 estimates the rear axle load WRL when turning left (step ST23) and estimates the rear axle load WRR when turning right (step ST24). Next, ECU 3 estimates the magnitude of the shift in the center of gravity position of the estimated rear axle load WRS when driving straight ahead, the rear axle load WRL when turning left, and the rear axle load WRR when turning right, in the vehicle width direction (step ST25). Here, ECU 3 estimates the magnitude of the shift X based on at least two of the estimated rear axle loads WRS when driving straight ahead, WRL when turning left, and WRR when turning right. For example, ECU 3 estimates the magnitude of the shift X based on the difference between the rear axle load WRL when turning left, which is a first rear axle load, and the rear axle load WRR when turning right, which is a second rear axle load (WRL-WRR), and the gross vehicle weight Wm. Here, the magnitude of the shift X can be a distance from the center in the vehicle width direction.Alternatively, the magnitude of the displacement X can be an index derived from the distance. For example, the index can be a multitude of levels set to increase as they move away from the center of the vehicle's width direction. The ECU 3 can temporarily store in a map a relationship between the difference between at least two values ​​derived from the estimated rear axle load WRS when driving straight ahead, the rear axle load WRL when turning left, and the rear axle load WRR when turning right, and the gross vehicle weight Wm, a speed V associated with the cornering speed and radius, a steering angle δ, a lateral acceleration Gc, a yaw rate R, or the like, in order to estimate the magnitude of the displacement X based on the difference in the estimated rear axle load WR.In this case, the time required to estimate the magnitude of the shift can be reduced, enabling highly sensitive and responsive vehicle behavior control. Next, ECU 3 performs vehicle behavior control based on the estimated magnitude of the displacement X (step ST26). Here, ECU 3 uses the estimated magnitude of the displacement X as an input parameter to execute vehicle behavior control. That is, ECU 3 performs vehicle behavior control appropriate to the extent of the half-loaded state when the state of charge is defined as a half-loaded state. As described above, according to the embodiment, the vehicle behavior control system performs vehicle behavior control based on the vehicle's center of gravity state in the lateral direction, which is estimated by the vehicle center of gravity state determination device 1, and the magnitude of the displacement X. Accordingly, the vehicle behavior control system can suitably perform vehicle behavior control even in cases where the center of gravity position Gx changes in the lateral direction, in cases of a half-loaded state during vehicle behavior control, in cases of a half-loaded state caused by movement of the loaded goods during vehicle behavior control, and the like.In particular, the vehicle behavior control, which takes into account the magnitude of the displacement X, allows for an early limitation of a rollover of the load vehicle 10, which may be generated during cornering in a half-loaded state. Reference symbol list 1 Vehicle center of gravity status determination device 2 Brake device 21 Master cylinder 22 Brake actuator 23R, 23L Right and left front wheel lines 24R, 24L Right and left rear wheel lines 25FL to 25RR Wheel cylinders 26 LSPV (Load-sensitive proportional valve) 27 Front wheel brake pressure sensor 28 Rear wheel brake pressure sensor 3 ECU 4 Drive device 5 Steering device 10 Truck 11 Loading area 12 Loaded goods 13FL to 13RR Wheel

Claims

Vehicle center of gravity state determination device (1) comprising: a load-sensitive proportional valve (LSPV) (26) configured to change a rear wheel brake pressure according to a rear axle load; a front wheel brake pressure sensor (27) configured to detect a brake pressure of a front wheel; a rear wheel brake pressure sensor (28) configured to detect a brake pressure of the rear wheel on a side downstream of the load-sensitive proportional valve (LSPV) (26); a rear axle load estimation unit (3) as part of an ECU configured to estimate a rear axle load, characterized in that the rear axle load estimation unit (3) as part of an ECU estimates the rear axle load on the basis of a relationship between front and rear brake pressures detected during braking and a rear axle load characteristic of the load-sensitive proportional valve (LSPV) (26);and by a vehicle center of gravity state determination device as part of an ECU (3) configured to determine a center of gravity state of a vehicle in a vehicle width direction based on the estimated rear axle load, wherein the rear axle load estimation unit as part of an ECU (3) is configured to estimate each of the rear axle loads in a case in which braking is performed in one of at least two states, including straight-ahead driving, right-turn driving and left-turn driving. Vehicle center of gravity state determination device according to claim 1, wherein the center of gravity state of the vehicle in the vehicle width direction is a magnitude of the displacement of a center of gravity position of a vehicle in the vehicle width direction, the rear axle load estimation unit as part of an ECU (3) is configured to estimate the rear axle loads in a case in which braking into a state during a left turn and during a right turn is performed as the respective first rear axle load and second rear axle load, and the vehicle center of gravity state determination device is configured to estimate the magnitude of the displacement of the center of gravity position of the vehicle in the vehicle width direction on the basis of the first rear axle load and the second rear axle load. Vehicle behavior control system comprising the vehicle center of gravity state determination device (1) according to claim 1 or 2; and a vehicle behavior control as part of an ECU (3) designed to control at least one braking force based on the center of gravity state of the vehicle in the vehicle width direction in order to control vehicle behavior. Vehicle center of gravity state determination method, comprising: a step of changing the rear wheel brake pressure according to a rear axle load; a step of sensing a front wheel brake pressure; a step of sensing a rear wheel brake pressure on a downstream side with respect to a load-sensitive proportional valve (LSPV) (26), wherein the rear wheel brake pressure changing unit is configured to change a rear wheel brake pressure according to the rear axle load; a step of estimating a rear axle load, characterized in that the estimation of the rear axle load is based on a relationship between front and rear brake pressures sensed during braking and a rear axle load property of the rear wheel brake pressure changing unit;and further by a step of determining a center of gravity state of a vehicle in a vehicle width direction based on the estimated rear axle load, wherein the rear axle load is estimated in a case in which braking is carried out in one of at least two states, including driving straight ahead, turning right and turning left.

Images