JPH0545453B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a limited slip differential for a four-wheel drive vehicle that is equipped with a limited slip differential and can switch between a two-wheel drive state and a four-wheel drive state. Regarding a control device.

(Prior art) As a conventional limited slip differential, for example, 323 of "Automotive Engineering Complete Book Volume 9 Power Transmission Device" (published by Sankaido Co., Ltd. on November 15, 1980)
The ones shown in Figures 5 and 30 are known.

This conventional limited slip differential (differential limiting device) has a multi-plate clutch interposed between the differential case and the side gear, and applies the tightening force to the multi-plate clutch to the pinion shaft and pressure ring. This was applied by the thrust force generated by the formed cam mechanism.

Therefore, if one of the drive wheels slips on a road surface with a low coefficient of friction such as an icy road or sandy road, or if one wheel lifts when turning, both side gears of the limited slip differential should be Relative movement occurs between the clutch and the differential case, which increases the tightening force on the multi-disc clutch, limits the differential, and increases the torque transmitted to the low-speed rotation side.

(Problems to be Solved by the Invention) However, in the case of such a conventional limited slip differential, the transfer ratio characteristic (driving force distribution ratio characteristic to the left and right wheels)
is uniquely defined by the mechanical structure, and even when used in part-time 4-wheel drive vehicles, the driving state (2
Since the differential was limited regardless of whether the car was in good condition (wheel drive or four-wheel drive), if two-wheel drive was selected on a so-called good road, the limited slip differential would be in effect. However, there is a problem of strong understeer when cornering, and if differential restriction is activated between the drive wheels when turning with high lateral acceleration, the ground load on the inner drive wheels will decrease and it will flow out from the inner wheels. The problem was that all of the torque was transmitted to the road surface through the outer wheels, generating a moment that could cause the vehicle to spin. Additionally, when four-wheel drive is selected on a road with a low friction coefficient, there is a problem in that differential limiting does not work unless there is a rotational difference between the left and right wheels, even though differential limiting is required. It was hot.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and to achieve this purpose, the present invention employs the following solving means.

The solution of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. A limited slip differential 4 is provided between the drive shafts of the wheels 2, 2' on the driven side, which is equipped with a clutch element 3 that prevents the generation of a difference in the left and right rotational speeds of the wheels 2, 2' even in the state of the clutch. In the four-wheel drive vehicle, an actuator 5 is provided on the limited slip differential 4 to change the engagement state of the clutch element 3 by external input, and the actuator 5 is connected to the drive switching clutch 1.
Based on the switching operation, a release signal is output to shift the clutch element 3 to the disengaged side when in the two-wheel drive state, and an engagement signal is output to shift the clutch element 3 to the engaged side when in the four-wheel drive state. A state control means 6 is provided.

(Function) Therefore, in the differential limiting control device for a four-wheel drive vehicle of the present invention, by using the above-described means, the engagement state control means 6 controls the clutch element 3 in the two-wheel drive state. Since a release signal for shifting to the release side is output, the limited slip differential 4 becomes a normal differential without differential limiting action.

This prevents understeer at the beginning of a turn in a two-wheel drive state.

Furthermore, when turning with high lateral acceleration, torque is transmitted only to the outer drive wheels when the ground load of the inner drive wheels decreases, thereby preventing vehicle spin that occurs.

On the other hand, in the four-wheel drive state, the engagement state control means 6 outputs an engagement signal that moves the clutch element 3 to the engagement side, so the limited slip differential 4 exerts a differential limiting action. Ru.

This improves running performance on a low friction coefficient road in a four-wheel drive state.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.
In describing this embodiment, a part-time four-wheel drive vehicle based on rear-wheel drive will be taken as an example.

First, regarding the embodiments shown in FIGS. 2 to 4,
Its configuration will be explained.

The four-wheel drive vehicle A of the embodiment, as shown in FIG. , a rear wheel drive shaft 19, a limited slip differential 20, left and right drive shafts 21, 21', and rear wheels 22, 22'.

The drive switching lever 14 is a lever that switches between a four-wheel drive state and a two-wheel drive state by the driver's operation inside the vehicle.When the lever is pushed forward in FIG. , the drive switching clutch 13a of the transfer gear 13 is connected, and a four-wheel drive state is established in which the drive force from the transmission 12 is distributed between the front wheels and the rear wheels.

Furthermore, when the drive switching lever 14 is pulled toward the rear in FIG. It becomes a two-wheel drive state where the drive is distributed only to the sides.

The piston 15 is connected to the drive switching lever 14.
It is connected by a connecting rod 24 and reciprocates within the master cylinder 16 in accordance with lever operation of the drive switching lever 14.

The hydraulic pipe 17 has one end connected to the cylinder chamber 25 of the master cylinder 16 and the other end connected to the hydraulic port 26 of the limited slip differential 20.
The cylinder chamber 25 is filled with oil.

The operating force of the drive switching lever 14 toward the four-wheel drive side moves the piston 15 to increase the oil pressure and is converted into hydraulic pressure.

Limited slip differential 2 above
0 is a housing 27, as shown in FIG.
Differential case 28, ring gear 29, side gear 3
It includes a 0, 30' pinion shaft 31, pressure rings 32, 32', multi-plate clutches 33, 33', reaction plates 34, 34', needle bearings 35, 35', and a hydraulic piston 36.

In addition, in the figure, 37 and 38 are stud bolts for attaching to the vehicle body, 39 and 39' are tapered roller bearings that support the differential case 28, 40 is a pinion gear, 41 is a pinion mate gear, 42, 4
2' is a spacer, 43 is a push rod, and 44 is a pressure oil chamber.

As shown in FIG. 4, the end of the pinion shaft 31 is formed into a rectangular cross section 31a, and has square grooves 32a, 32 that engage with the rectangular cross section 31a.
a' is formed on the pressure rings 32, 32', and is a multi-plate clutch 33, 3 by cam action.
3' is configured so that no fastening force is generated.

The multi-plate clutches 33, 33' are interposed between the differential case 28 and the pressure rings 32, 32', and include a friction plate 32a fixed to the differential case 28 side in the rotational direction.
32a', and friction disks 33b, 33 fixed in the rotational direction to the side gears 30, 30'.
It is composed of b'.

In addition, the differential case 2 of the multi-plate clutch 33, 33'
Reaction plates 34, 34' are in contact with the 8 side, and are configured to apply the fastening force from the hydraulic piston 36 to the multi-plate clutches 33, 33' via the reaction plates 34, 34'. At the same time, the reaction force of the fastening force is supported by the housing 27.

Here, when comparing the configuration in the embodiment and the configuration in the claims, it is found that since the embodiment uses a mechanical configuration to perform control, the drive state detection means and the fastening force control means are driven. This corresponds to a lever operation of the switching lever 14, the fastening force release signal corresponds to a releasing hydraulic pressure (or low hydraulic pressure), the fastening force signal corresponds to a high hydraulic pressure, and the actuator corresponds to the hydraulic piston 36.

Further, in the embodiment, multi-plate clutches 33, 33' are used as friction clutch elements, a piston 15 and a master cylinder 16 are used as means for generating clutch engagement force, and the driving source for the engagement force is lever operation of the drive switching lever 14. It is power.

Next, the operation of the embodiment will be explained.

(b) When in two-wheel drive mode When the driver selects the drive switching lever 14 to the two-wheel drive side, the piston 1 is
5 moves in a direction to expand the volume of the cylinder chamber 25, so that the hydraulic pressure of the hydraulic pipe 17 becomes almost zero or an extremely low release pressure.

Therefore, no tightening force is generated on the multi-plate clutches 33, 33' due to hydraulic pressure supplied to the hydraulic piston 36, and the limited slip differential 20 becomes a normal differential without differential limiting action. .

Therefore, when cornering in a two-wheel drive state, it is possible to prevent a strong understeer tendency due to limited differential movement.

Additionally, when turning with high lateral acceleration, if the differential limiting action is activated, torque is transmitted only to the outer drive wheels when the ground load of the inner drive wheels decreases, causing vehicle spin. In this case, since there is no differential limiting effect, the above vehicle spin can be prevented.

(b) When in 4-wheel drive mode When driving on a road with a low friction coefficient such as a rough road, snowy road, or muddy road, the driver moves the drive switching lever 14 to 4-wheel drive.
When the wheel drive side is selected, the piston 15 moves in the direction of reducing the volume of the cylinder chamber 25 by operating the lever, so that the oil pressure in the cylinder chamber 25 increases, and the inside of the hydraulic pipe 17 enters a high oil pressure state. Become.

For this purpose, high hydraulic pressure is applied to the hydraulic piston 36 from the hydraulic pipe 17 through the hydraulic port 26 and the hydraulic chamber 44, and the multi-plate clutches 33, 33' are fastened by this high hydraulic pressure, and the limited The slip differential 20 is a differential that always exerts a differential limiting action.

Therefore, in a four-wheel drive state, due to the differential limiting effect, driving force is transmitted not only when one wheel slips, but also when both left and right wheels slip.
Driving performance on roads with low friction coefficients such as rough roads and snowy roads is improved.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, although electrical sensors, control units, and actuators were used in the embodiment, differential limiting control was performed using an entirely mechanical configuration. Some are equipped with a control unit that inputs a drive status signal using a switch or sensor, and outputs an electrical signal such as a fastening force release signal or a fastening force signal to an actuator such as a solenoid according to the input signal, or a mechanical It is also possible to use a combination of configuration and electrical configuration.

Further, the hydraulic pressure used as the clutch engagement force may also be the hydraulic pressure from an oil pump.

(Effects of the Invention) As explained above, in the differential limiting control device for a four-wheel drive vehicle of the present invention, in both the two-wheel drive state and the four-wheel drive state, the drive side In a four-wheel drive vehicle that is provided with a limited slip differential between the drive shafts of the wheels, the limited slip differential is provided with a clutch element that prevents the occurrence of a difference in the left and right rotational speed of the wheels. An actuator is provided that allows the engagement state of the clutch element to be varied by external input.
outputting a release signal to the actuator to shift the clutch element to the release side when in a two-wheel drive state based on the switching operation of the drive switching clutch;
By providing an engagement state control means that outputs an engagement signal to shift the clutch element to the engagement side when in a four-wheel drive state, it is possible to prevent understeer at the beginning of a turn in a two-wheel drive state and to prevent vehicle spin when turning with high lateral acceleration. , it is possible to improve running performance on a road with a low friction coefficient in a four-wheel drive state.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the limited slip differential control device for a four-wheel drive vehicle according to the present invention, Fig. 2 is an overall view showing an embodiment of the device, and Fig. 3 is a diagram showing the limited slip differential of the embodiment of the device. The sectional view shown in FIG. 4 is a view seen from the direction of arrow Z in FIG. 3. DESCRIPTION OF SYMBOLS 1... Drive switching clutch, 2, 2'... Wheels (normally driven wheels), 3... Clutch element, 4... Limited slip differential, 5... Actuator, 6... Engagement state control means.

Claims (1)

[Scope of Claims] 1. A drive switching clutch that switches between a two-wheel drive state and a four-wheel drive state, and a drive for the wheel that is driven in either the two-wheel drive state or the four-wheel drive state. In a four-wheel drive vehicle that is provided with a limited slip differential between the axles that is equipped with a clutch element that prevents the occurrence of a difference in the left and right rotational speed of the wheels, the limited slip differential is provided with a clutch element. An actuator whose engagement state is variable by external input is provided, and a release signal is output to the actuator to shift the clutch element to the release side when the two wheels are in the two-wheel drive state based on the switching operation of the drive switching clutch. 1. A differential limiting control device for a four-wheel drive vehicle, comprising engagement state control means for outputting an engagement signal for shifting a clutch element to an engagement side when in a wheel drive state.