JPH0435367B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive coupling device for four-wheel drive in which the front and rear wheels are driven by the same engine, and is capable of optimal control in accordance with changes in the vehicle over time. be.

In a four-wheel drive vehicle where the front and rear wheels are driven by the same engine, there is a slight difference in the effective diameter of the front and rear tires, and when driving in turns, the tire may slip due to the difference in the rolling path of the tire. As a result, an unreasonable force is applied to the drive system, so it is necessary to provide a means to prevent this.

For this reason, in conventional full-time four-wheel drive vehicles, even if there is a rotational speed difference between the first rotating shaft that transmits driving force to the front wheels and the second rotating shaft that transmits driving force to the rear wheels, the driving force is transmitted. A third differential device called a center differential is used to allow the vehicle to rotate, which is disadvantageous compared to a part-time 4-wheel drive vehicle in terms of weight, size, and cost. There are cases where four-wheel drive cannot be achieved when a drive is required, and the device becomes even more complex, such as requiring a deflock mechanism.

On the other hand, many part-time 4-wheel drive vehicles do not have a center differential, and if there are problems with 4-wheel drive such as tight corner braking caused by cornering, the driver must operate 2-wheel drive. This has the disadvantage that driving operations are complicated.

Therefore, a system using an electromagnetic clutch has been proposed as an equivalent to the conventional center differential (Japanese Patent Application Laid-open No. 15019/1986), and in order to eliminate the above drawback, the left and right drive of the differential device for the front wheels that is constantly driven has been proposed. A rotation sensor is installed on each shaft, and the left and right slip status of the front wheels is detected based on the rotation signal, or the engagement force of the electromagnetic clutch is adjusted based on signals from the vehicle speed sensor and steering angle sensor. It allows for speed differences, or controls the vehicle to use four-wheel drive when the vehicle is unable to travel due to front wheel slip.

However, the engagement force of the electromagnetic clutch is controlled in such a way that it has a fixed relationship with the steering angle, and this is due to changes over time due to vehicle use, such as changes in the effective diameter of the front and rear tires due to load distribution or tire wear. If the conditions in which slip occurs in the front and rear wheels change, the engagement force of the electromagnetic clutch will not be optimally controlled.
If the required rotational speed difference (slip) cannot be obtained between the front and rear wheels when turning, a braking phenomenon may occur, causing uneven tire wear, and the steering becomes heavy, which may impair steering stability.

The present invention eliminates such conventional drawbacks and enables optimum control at all times even when the vehicle changes over time.
The purpose of the present invention is to provide a drive coupling device for wheel drive. A first configuration of the present invention that achieves this object is to connect a first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels. The first rotating shaft and the second rotating shaft are connected to each other via a hydraulic pump that is driven by a rotational speed difference between the first and second rotating shafts and is capable of discharging an amount of oil corresponding to the rotational speed difference and transmitting driving force. A rotation sensor is provided to detect the rotational speed of the hydraulic pump, and a steering angle sensor is provided to detect the steering angle.A control valve is provided to control the discharge pressure of the hydraulic pump and adjust the transmitted driving force. A reference line is set in advance by the slip ratios of the first rotation shaft and the second rotation shaft, and when the slip ratio is larger than this reference line and positive, or when the slip ratio is smaller than the reference line and negative, the hydraulic pump The invention is characterized by comprising a control device that controls the control valve to increase the discharge pressure and to make the discharge pressure zero at other times, and further includes a first rotary shaft that transmits driving force to the front wheels. and a second rotating shaft that transmits driving force to the rear wheels are driven by the rotational speed difference between the first rotating shaft and the second rotating shaft, and are driven by discharging an amount of oil according to the rotational speed difference. A rotation sensor connected via a hydraulic pump capable of transmitting force and detecting the rotational speed of each of the first rotation shaft and the second rotation shaft is provided, and a steering angle sensor is provided to detect the steering angle;
A control valve is provided to control the discharge pressure of the hydraulic pump and adjust the transmitted driving force, and a reference line determined by the slip ratio of the first rotating shaft and the second rotating shaft with respect to changes in the steering angle is set when the steering angle is zero and the engine The slip ratio detected when the output torque of The present invention is characterized by comprising a control device that controls the control valve to increase the discharge pressure of the hydraulic pump when the slip rate is small and negative, and to make the discharge pressure zero at other times.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of a four-wheel drive drive coupling device of the present invention.

A transmission 2 is connected to an engine 1 placed horizontally, and driving force is taken out from a drive gear 4 attached to an output shaft 3 of the transmission, and an intermediate transmission shaft is provided with gears 6 and 7 at both ends via an idle gear 5. 8, and from one gear 7 of this intermediate transmission shaft 8 to the front wheel 9
The driving force is transmitted to the differential gear 10 for driving the front wheels 9, while the driving force transmitted to the front wheels 9 is directly transmitted to the first rotating shaft 11 via the gear 12 to form a four-wheel drive drive connection. The driving force is transmitted to the second rotating shaft 14 via the device 13, and is transmitted to the differential device 17 for the rear wheels 16 via the gear mechanism 15 that changes the direction of rotation. to drive.

As shown in FIG. 2, the four-wheel drive drive coupling device 13 includes a vane pump 20, which is a hydraulic pump, and a hydraulic control circuit 2 attached thereto.
1, the rotor 20a of the vane pump 20 is connected to the first rotating shaft 11 through which the driving force to the front wheels 9 is directly transmitted, and the cam ring 20b is connected to the second rotating shaft through which the driving force is transmitted to the rear wheels 16. It is connected to a shaft 14. The vane pump 20, which serves as a hydraulic pump, discharges an amount of oil proportional to its rotation speed, and has a rotor 20a and a cam ring 2.
0b, relative rotation, that is, the first rotation axis 11
When a relative rotation occurs between the shaft and the second rotating shaft 14, it functions as a hydraulic pump and generates hydraulic pressure, and the discharge port of the vane pump 20 (the suction and discharge port at the tip in the relative rotation direction corresponds to this). By blocking the rotor 20a and the cam ring 2, the static pressure is applied via oil.
0b become like a rigid body and are rotated together. For this reason, two pump chambers are formed at diagonal positions in the cam ring 20b, and four suction and discharge ports 22, 23, 24 and 25 are formed at almost diagonal positions, and the suction and discharge ports 22 and 24 and the suction and discharge ports 23 and 25, which are located diagonally and have the same function, respectively, send oil to the stationary side even when the cam ring 20b is rotating. The first oil passage 26 and the second oil passage 27 are in communication with each other via a mechanism that allows passage therethrough. Further, an oil reservoir 30 is communicated between the first oil passage 26 and the second oil passage 27 via check valves 28 and 29, respectively, and only flow from the oil reservoir 30 is allowed, and the first oil passage 27 Both oil passages 26 and 27 are communicated with each other through two check valves 31 and 32 facing each other, which allow only outflow, and an intermediate portion between these two check valves 31 and 32 is connected to the second oil passage 27. It communicates with the relief valve 33. A communication path 35 between the oil reservoir 30 and the intermediate portions up to the two check valves 28 and 29 is provided in the intermediate portion of the relief valve 33 on the spring 34 side.
A piston 36 is provided at the other end of the piston 36 for controlling the opening pressure of the relief valve 33 by a spring 34, and a control hydraulic pressure that is duty-controlled acts on the other end of the piston 36. Then, for duty control, a constant pressure of oil pressure supplied through an orifice 37 is applied to a solenoid valve 38.
This solenoid valve 38 is electrically connected to a computer 39, and is controlled by the computer 39.
The engine speed N _E input to the first rotating shaft 1
1 rotation speed N ₁ , rotation speed N ₂ of the second rotating shaft 14 , throttle opening β, brake operation detection switch S _wB ,
The hydraulic pressure acting on the other end of the piston 36 is controlled by the steering angle detection signal θ. Note that the constant pressure oil pressure supplied through the orifice 37 may be used as the control oil pressure if the transmission 2 is an automatic transmission, or an oil pump may be installed in the case of a manual transmission. Secure this oil pressure by etc.

With such a hydraulic control circuit 21, the discharge pressure always acts on the valve body of the relief valve 33 regardless of the relative rotation direction between the rotor 20a and the cam ring 20b, and the oil reservoir 30 communicates with the suction port. .

Next, the driving state of the four-wheel drive drive coupling device configured as described above will be explained.

The control computer 39 is programmed with the rotational speed N ₁ of the first rotating shaft 11 corresponding to the rotational speed of the front wheels 9 in advance.
and the second rotating shaft 14 corresponding to the rotational speed of the rear wheel 16.
The slip rate S is calculated from the rotational speed _N2 using the following equation, and the slip rate S required for the steering angle θ is stored.

S=N ₁ −N ₂ /N ₁ , that is, the slip rate S ₀ when the steering angle θ=O
is the reference value, and the first rotating shaft 11 and the second rotating shaft 14
The slip rate S required between
The relationship S=S ₀ +α·θ is stored as a reference line L, such as the one shown in FIG. 3, for example.

Then, based on such a reference line L, the steering angle θ
The discharge pressure of the hydraulic pump 20 is controlled by the actually measured values of the rotation speed N ₁ of the first rotation shaft 11 and the rotation speed N ₂ of the second rotation shaft 14 . This control is performed respectively in four ranges A, B, C, and D shown in FIG.

If the slip rate S ₁ actually measured in a certain driving state is above the reference line L (S ₁ >L), and if this slip rate S ₁ is positive (S ₁ >O), that is, the front wheels 9 move too quickly and In the range A where the rear wheels 16 are too slow, it is necessary to increase the torque transmitted to the rear wheels 16 and strengthen the four-wheel drive state so as to reduce the slip ratio _S1 .

Therefore, in this case, the computer 39 sends a signal to the duty control solenoid valve 38 to increase the discharge pressure of the hydraulic pump 20.

As a result, the first rotating shaft 11 and the second rotating shaft 14
The vane pump 20 functions due to the rotational speed difference generated between the vane pump 20 and the vane pump 20, which generates hydraulic pressure corresponding to the rotational speed difference.The rotor 20a and the cam ring 20b rotate as a unit, and this discharge pressure is controlled between the controlled hydraulic pressure and the vane pump. A driving force corresponding to the pressure receiving area is transmitted to the rear wheels 16, resulting in a four-wheel drive state.

In this case, the oil flow in the vane pump 20 is caused by the relative rotation of the rotor 20a, as shown in FIG.
3 and 25 serve as suction ports, and oil is sucked in from the oil reservoir 30 via the check valve 29, while the suction and discharge ports 22 and 24 serve as discharge ports, and the check valve 31 is closed at the same time as the check valves 28 and 32 are closed.
is guided to the relief valve 33 via. In the figure, solid line arrows indicate the flow of discharged oil, and broken line arrows indicate the flow of suction oil.

If the slip rate S ₁ actually measured in a certain driving state is above the reference line L (S ₁ >L), and the slip rate S ₁ is negative (S ₁ <O) and the rear wheel 16 is moving too quickly, In other words, in range B, such as when the front wheels 9 tend to lock up during steering and braking, if the discharge pressure is increased to create a four-wheel drive state, reverse drive will occur and the front wheels 9 and rear wheels 16 will change the driving force. The positive and negative are reversed.

Therefore, in such a state, the computer 39 sends a signal to the duty control solenoid valve 38 to prevent the relief valve 3 from entering the four-wheel drive state.
3 and set the discharge pressure to O, vane pump 20
Simply circulate the oil generated.

If the slip ratio S ₁ actually measured in a certain operating state is below the reference line L (S ₁ <L), and if the slip ratio S ₁ is positive (S ₁ >O), the slip ratio S 1 is below the reference line L. Range C, which is the case where the rear wheels 16 need to rotate somewhat faster because the steering angle is on the side, and the front wheels 9 have to rotate a little faster with respect to the steering angle θ because the slip rate _S1 is positive. Well then,
If the discharge pressure is increased to create a four-wheel drive state in the same way as in the above case, the polarity of the driving forces of the front wheels 9 and the rear wheels 16 will be opposite to each other.

Therefore, in order to avoid a four-wheel drive state in which a contradiction occurs between the front and rear wheels 9 and 16 even in this range of C, the computer 39 sends a signal to the duty control solenoid valve 38 to open the relief valve 33 and operate the vane pump. 20 discharge pressure to O
It has front two-wheel drive.

The slip rate S ₁ actually measured in a certain driving condition is below the reference line L (S ₁ <L), and therefore the rear wheels 16 need to rotate somewhat faster, and the slip rate S ₁ is lower than the reference line L (S 1 <L). D, which is negative (S ₁ < O) and the front wheel 9 is slow and the rear wheel 16 is somewhat fast.
In this range, unlike the above state, there is no contradiction such as the positive and negative polarity of the driving force being reversed even if this state is maintained, so the four-wheel drive state is defined.

Therefore, the computer 39 sends a signal to the duty control solenoid valve 38 to increase the opening pressure of the relief valve 38 to increase the discharge pressure of the vane pump 20 and increase the amount of driving force transmitted to the rear wheels 16.

In this case, for example, the brake state of the front wheels 9 is a little locked, and the first rotation shaft 11 and the second rotation shaft 1 of the four-wheel drive drive coupling device 13
4, a rotational speed difference occurs in the opposite direction to that described above, and in the vane pump 20, oil flows as shown in FIG. Oil is sucked from the oil reservoir 30 through the suction outlet 2
3 and 25 are discharge ports, and the check valves 29 and 31 are closed through the second oil passage 27, and the check valve 32 is led to the relief valve 33, where a large hydraulic pressure is applied.The pressure of this discharge oil is applied to the duty control solenoid valve. 38, a predetermined driving force is transmitted to the rear wheels 16, resulting in a four-wheel drive state, thereby increasing the brake torque to the rear wheels 16 to prevent the front wheels 9 from locking.

According to such a 4-wheel drive drive coupling device 13, when a part-time 4-wheel drive vehicle requires a 4-wheel drive state, the driver's operation is automatically required. Switching between wheel drive and two-wheel drive is performed, and a four-wheel drive state is obtained with a driving force corresponding to the rotational speed difference between the front wheels and the rear wheels. In addition, it can be made smaller and more compact than the center differential that is always installed in full-time four-wheel drive vehicles, and it also reduces weight and costs.

Furthermore, from the rotation speed N ₁ of the first rotation shaft 11 corresponding to the rotation speed of the front and rear wheels 9, 16, the rotation speed N ₂ of the second rotation shaft 14, and the steering angle θ, the operating state can be determined as 4.
By controlling the four-wheel drive state in three ranges A, B, C, and D, problems such as vertical corner braking, which is a problem with four-wheel drive vehicles, and the polarity of the driving force of the front and rear wheels are reversed, can be avoided. This eliminates the problem and provides a state where four-wheel drive and engine braking are required.

Next, other embodiments of the present invention will be described.

In the above embodiment, the driving state is divided into four ranges A, B, C, and D based on the reference line L, and the four-wheel drive drive coupling device 13 is controlled according to each state. When the effective diameter of the tire changes due to changes such as load distribution or tire wear, the steering angle θ and the corresponding slip will change at the reference line L determined in advance from the reference value S ₀ and the slope α as described above. The relationship with the rate S deviates from the optimal value.

Therefore, the reference value S ₀ is updated based on changes in the vehicle over time, and control is performed using the updated reference line.

First, the actual slip rate S ₁ is determined from the rotation speed N ₁ of the first rotation shaft 11 and the rotation speed N ₂ of the second rotation shaft 14 . At this time, it is necessary to know the slip ratio S ₁ obtained under the same conditions as the reference value S ₀ , so when the vehicle is running, the steering angle θ is O, that is, the straight-ahead state, and the output torque of the engine 1 is T _E When is O, the number of revolutions N ₁ of the first rotating shaft 11 and the number of revolutions of the second rotating shaft 14
N ₂ is detected, the actual slip rate S ₁ in this state is determined, and this is used as a new reference value. (If it is the same as the predetermined S ₀ , leave it as is.) Note that the steering angle θ=O is detected from the steering angle sensor, but the output torque T _E =O of the engine 1 means the running resistance of the vehicle. When it is assumed that the output torque T _E of engine 1 that can maintain a certain constant speed
is calculated from the relationship between the engine torque T _E (actually, it takes _a certain range) with respect to the predetermined engine speed N _E , or the throttle opening β (actually The output torque T _E =O is detected from the relationship (has a certain range).

After the reference value S ₀ is updated to S ₁ in this way, it is assumed that the rate of change of the slip rate S with respect to the steering angle θ remains constant, and the slope α is assumed to be the same.

Therefore, the new reference line L ₁ after updating the reference value to S ₁ becomes a straight line that satisfies the following equation.

L ₁ = S ₁ + α・θ In this way, once the new reference line L ₁ has been set, the four ranges A, B, C, and D or the new reference value S ₁ can be set according to the operating conditions as described above. S ₁ ≧O
In this case, the discharge pressure of the vane pump 20 is controlled in three ranges A, C, and D to obtain a four-wheel drive state or a two-wheel drive state. The fifth section shows control when such changes over time are taken into consideration.
This is a flowchart shown in the figure.

In this way, by controlling the four-wheel drive drive coupling device while updating the reference line L according to changes in the effective diameter of the tires, the actual slip rate S of the front and rear wheels can always be maintained even if the vehicle changes over time. ₁ , it is possible to obtain optimal driving conditions and maintain good steering stability without causing braking phenomena or uneven tire wear.

In the above embodiment, the four-wheel drive drive coupling device 1
In the explanation, a vane pump is used as the hydraulic pump in step 3, and it is a balanced type with four suction and discharge ports, but depending on the amount of driving force transmitted, an unbalanced type vane pump with two suction and discharge ports may be used. Possible, and other types of hydraulic pumps such as internal gear pumps, trochoid pumps, hypocycloid pumps, axial and radial plunger pumps, etc., can also be used, such as those whose discharge oil volume changes according to the difference in rotational speed. That's fine. Furthermore, the present invention is applicable not only to a type that drives the front wheels in a normal straight-ahead state but also to a type that drives the rear wheels. moreover,
The transmission may also be manual or automatic.

As described above in detail with the embodiments, according to the first configuration and operation of the present invention, the first rotating shaft that transmits the driving force to the front wheels and the second rotating shaft that transmits the driving force to the rear wheels are connected to each other. These are connected via a hydraulic pump that is driven according to the rotational speed difference and discharges an amount of oil according to the rotational speed difference, and the driving force is transmitted by the static hydraulic pressure to obtain a four-wheel drive state. The discharge pressure of the hydraulic pump is controlled based on a predetermined reference line representing the relationship between the steering angle and the slip ratio in accordance with the actually measured slip ratio between the rotating shaft and the second rotating shaft. An optimal four-wheel drive state or two-wheel drive state can be obtained depending on the ratio.

Further, according to the second configuration and operation of the present invention, the first rotating shaft that transmits driving force to the front wheels and the second rotating shaft that transmits driving force to the rear wheels are driven according to the rotational speed difference between them. and are connected via a hydraulic pump that discharges an amount of oil according to the difference in rotational speed, and the static hydraulic pressure transmits the driving force to obtain a four-wheel drive state and to connect the first rotating shaft and the second rotating shaft. In accordance with the actually measured slip rate, a reference line representing the relationship between a predetermined steering angle and the slip rate is updated with the slip rate actually measured under a predetermined operating condition, and the discharge pressure of the hydraulic pump is adjusted based on the new reference line. Since the control is performed, the optimum four-wheel drive state or two-wheel drive state can always be obtained even if the effective diameter of the tires changes due to changes in the vehicle over time.

Therefore, there is no braking phenomenon or uneven tire wear during 4-wheel drive, and the polarity of the driving force on the front and rear wheels does not become opposite to each other, making it necessary to drive in 4-wheel drive mode or use engine braking. Four-wheel drive is available only in certain situations.

In addition, in the case of any invention, part-time 4
In addition to eliminating problems such as tight corner braking in wheel drive vehicles and the complexity of driving operations, it is also smaller and lighter than the center differential conventionally equipped on full-time four-wheel drive vehicles, and has a simple structure. It will be cheaper.

[Brief explanation of drawings]

1 to 5 show an embodiment of the four-wheel drive drive coupling device of the present invention, and FIG. 1 is a schematic configuration diagram;
Fig. 2 is a detailed sectional view, Fig. 3 is an explanatory diagram showing the relationship between the slip rate S and the steering angle θ, and Fig. 4 a,
b is an explanatory diagram of the oil flow, and FIG. 5 is a flowchart showing the control contents. In the drawing, 9 is a front wheel, 10 is a differential gear for the front wheels,
11 is a first rotating shaft, 13 is a four-wheel drive drive coupling device, 14 is a second rotating shaft, 16 is a rear wheel, 17 is a differential device for the rear wheels, 20 is a vane pump, 20a is a rotor, and 20b is a cam ring. , 21 is a hydraulic control circuit, 22, 23, 24, 25 are suction and discharge ports, 2
6, 27 are the first and second oil passages, 28, 29, 3
1 and 32 are check valves, 30 is an oil reservoir, 33 is a relief valve, 36 is a piston, 37 is an orifice, 38 is a solenoid valve, and 39 is a computer.

Claims (1)

[Claims] 1. A first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels are controlled by a difference in rotational speed between the first rotating shaft and the second rotating shaft. The rotating shafts are connected via a hydraulic pump capable of transmitting a driving force by discharging an amount of oil according to the rotational speed difference, and detecting the respective rotational speeds of the first rotating shaft and the second rotating shaft. A steering angle sensor for detecting a steering angle is provided, and a control valve for controlling the discharge pressure of the hydraulic pump and adjusting the transmitted driving force is provided, and a control valve is provided for controlling a first rotation shaft and a second rotation shaft for changes in the steering angle. A reference line is set in advance based on the slip ratio of the rotating shaft, and when the slip ratio is larger than the reference line and positive, or when the slip ratio is smaller than the reference line and negative, the discharge pressure of the hydraulic pump is increased and A drive coupling device for four-wheel drive, comprising a control device that controls the control valve so that the discharge pressure is zero at other times. 2. A first rotating shaft that transmits driving force to the front wheels and a second rotating shaft that transmits driving force to the rear wheels are driven and rotated by the rotational speed difference between the first rotating shaft and the second rotating shaft. A rotation sensor is provided which is connected via a hydraulic pump capable of transmitting driving force by discharging an amount of oil according to the speed difference, and detects the rotation speed of each of the first rotation shaft and the second rotation shaft, and also includes a rotation sensor that detects the rotation speed of the first rotation shaft and the second rotation shaft. A steering angle sensor is provided to detect the steering angle, and a control valve is provided to control the discharge pressure of the hydraulic pump and adjust the transmitted driving force, and the slip rate of the first rotation shaft and the second rotation shaft is adjusted according to the change in the steering angle. A mechanism is provided for updating the determined reference line to a new reference line parallel to the reference line based on the slip rate detected when the steering angle is zero and the output torque of the engine is zero, and the slip rate is updated from this new reference line. a control device that controls the control valve to increase the discharge pressure of the hydraulic pump when the slip ratio is large and positive or when the slip ratio is smaller and negative than a reference line, and to make the discharge pressure zero at other times; A four-wheel drive drive coupling device characterized by: