JPH0583771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a power transmission system for a vehicle, particularly a power transmission system for a vehicle in which an automatic transmission type transmission is directly connected to an engine by a clutch without going through a torque converter. , relates to a method for automatically controlling a clutch.

Conventional Technology In the past, it was common for power transmission systems for vehicles equipped with automatic transmissions to be equipped with a torque converter, but in this case there were limits to the improvement of vehicle acceleration and fuel consumption. Therefore, in recent years, vehicle power transmission systems in which an automatic transmission is connected directly to the engine via a clutch without going through a torque converter (hereinafter referred to as direct powertrain) have been developed.
started to be reviewed.

In a vehicle power transmission system equipped with a torque converter, when the load on the transmission side is large relative to the engine output, slippage of the torque converter increases and engine stall is prevented from occurring. In a direct powertrain, if the clutch is not disengaged, engine stall will occur.

However, if the clutch is completely disengaged, the vehicle becomes completely unrestrained and unstable.
For example, if the clutch is disengaged when the road surface is sloping, the vehicle will begin to move backwards, but the driver does not necessarily expect the clutch to be disengaged, so if the vehicle begins to move backwards, the driver will You will be surprised. In addition, since no torque is applied to the direct power train, play occurs in the meshing portions of the gears in the direct power train, which causes a collision noise when the gears mesh again, causing an increase in driving noise.

Problems to be Solved by the Invention In view of the above-mentioned circumstances, the present invention has been developed to provide a vehicle with a direct power train in which the clutch is activated in order to prevent engine stalling when the engine speed drops significantly. This was done to solve the problem that the vehicle would become unstable if the clutch was disengaged.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides, in a direct power train, when the brakes of a vehicle are in a non-applied state, (a) the engine rotational speed at which engine stall occurs; (b) Based on the detection signal, the clutch transmits torque to the hydraulic pressure of the actuator that connects and disconnects the clutch. (c) performing control to lower the engine oil pressure to a first set oil pressure that is preset to a level at which the engine speed slips to an extent that allows the engine speed to recover from the first reference speed; A step of controlling the oil pressure of the actuator to increase the oil pressure to a second setting oil pressure that is preset to a value higher than the first setting oil pressure when the rotation speed has recovered to a second reference rotation speed that is higher than the first reference rotation speed. While repeating each process,
When the brake is in an applied state, the clutch is kept in a disengaged state.

The process of controlling the oil pressure to lower it to the first set oil pressure and the process of controlling it to raise it to the second set oil pressure are called the steps of controlling the oil pressure to lower it to the first set oil pressure and raise it to the second set oil pressure, respectively. This does not mean that the oil pressure actually needs to decrease to the first set oil pressure or increase to the second set oil pressure. For example, as will be explained in connection with the embodiments later, even if control is performed to increase the oil pressure to the second set oil pressure, the engine speed will rise to the first level before the actual oil pressure reaches the second set oil pressure due to a response delay. There is a possibility that the engine speed decreases to the reference rotation speed and control to lower the oil pressure to the first set oil pressure is started, and this is okay.

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

Figure 2 shows an example of a direct power train for a forklift truck.
is the engine. The engine 10 has a pump 12
and a planetary gear unit 14, and the planetary gear unit 14 is connected to the sun gear 1.
6, 18, 20, 22, planetary gear 24, 2
6, 28, 30, ring gear 32, 34, 36,
38, forward clutch 40, reverse clutch 4
2, a first clutch 44, a second clutch 46, a third clutch 48, etc. In the third clutch 48, both of the two clutch elements connected to each other are rotatable, but in other clutches, one clutch element is not rotatable. When the forward clutch 40 or the reverse clutch 42 is in the engaged state, any one of the first, second, and third clutches is brought into the engaged state, thereby moving forward 3.
3 speeds or 3 reverse speeds. That is,
In this embodiment, the transmission is composed of a sun gear, a planetary gear, etc., and shift clutches such as a first clutch 44, a second clutch 46, and a third clutch 48.
This and the engine 10 are connected by a forward clutch 40 or a reverse clutch 42, which are main clutches.

A reduction gear 58 consisting of pinions 50, 52 and gears 54, 56 is connected to the planetary gear unit 14, and left and right drive wheels 62 are connected to the reduction gear 58 via a differential gear 60.

A pump 12 connected to the engine 10 sucks hydraulic oil from a tank 70 as shown in FIG.
a, 46a and 48a. The hydraulic pressure supplied to these is always kept at a constant value by the regulator 72, but the hydraulic pressure supplied to the actuators 40a and 42a of the forward clutch 40 and reverse clutch 42 is further controlled by a modulator 74. It is becoming more and more like this.

Modulator 74 includes regulator 72 and actuator 40a or 4, as shown in FIG.
A drain passage 78 is provided for draining hydraulic oil into the tank 70 from a main passage 76 that connects to the main passage 2a. A relief valve 80 is provided at the connection portion of the drain passage 78 to the main passage 76. The relief valve 80 includes a valve element 82, a spring 84,
It is equipped with a piston 86, a spring 88, etc.
The opening pressure of this relief valve 80 is the piston 86
It is designed to change according to the change in the position of.
The position of this piston 86 is the position of the spring 8
8 and 84 and the operating force of the piston 86 based on the hydraulic pressure in the hydraulic chamber 90, and the hydraulic pressure in the hydraulic chamber 90 is controlled by an electromagnetic on-off valve 92. It's summery. Hydraulic oil in the main passage 76 is led to the hydraulic chamber 90 via a control passage 96 having a throttle 94, and an electromagnetic on-off valve 92 for the hydraulic oil in the hydraulic chamber 90 is introduced.
By controlling the flow rate from the hydraulic chamber 90
The hydraulic pressure of the engine is now controlled.
The electromagnetic on-off valve 92 closes when the modulating solenoid 98 is off, that is, when no current is supplied, and opens when the modulating solenoid 98 is on. The amount of hydraulic oil flowing out from the hydraulic chamber 90 is controlled by changing the duty ratio of the pulsed current.

The hydraulic oil whose hydraulic pressure is controlled by the modulator 74 is selectively supplied to the actuator 40a of the forward clutch 40 and the actuator 42a of the reverse clutch 42 by a manual directional control valve 100. ing. That is, the direction switching valve 100 is connected to a shift lever 101 as an operating member for determining the traveling direction of the vehicle, and when the shift lever 101 is in the neutral position, either actuator 40a, 42
Hydraulic oil is not supplied to the actuators a, and when the shift lever 101 is operated to the forward or reverse position, the hydraulic oil is supplied to the corresponding actuators. That’s all, pump 1
2. A clutch connection/disconnection device is constituted by the regulator 72, the modulator 74, the directional control valve 100, and the like.

On the other hand, the regulator 72 and the first
In the middle of the oil passage connecting the actuators 44a, 46a and 48a of the second and third clutches, directional control valves 102 and 104 are provided.
is installed. These directional control valves 102 and 104 are connected to the drain passage 11 by energizing shift solenoids 106 and 108, respectively.
When the shift solenoids 106 and 112 are open, the state shown in FIG.
8 can be switched to the opposite state when each is demagnetized. That is, depending on whether the shift solenoids 106, 108 are on or off, the actuators 44a, 46a, and 48
Hydraulic oil is supplied to either the first clutch 44 or the second clutch 4.
6 or third clutch 48 is connected.

The shift solenoids 106, 108 and the modulating solenoid 98 are controlled by a microcomputer 116 via a solenoid drive circuit 114, as shown in FIG. The microcomputer 116 is equipped with a CPU (central processing unit) 118, and a sensor 12 is connected to the microcomputer 116.
A signal from 0 is input. The sensor 120 is disposed close to the outer periphery of the gear 122 and generates an alternating current signal as the gear 122 rotates. This AC signal is shaped into a rectangular wave by the waveform shaping circuit 124, and the CPU 1
18. Since the gear 122 is connected to the engine 10 as shown in FIG. 2, the frequency of the square wave is proportional to the rotational speed of the engine 10.
Therefore, the CPU 118 can calculate the rotational speed of the engine 10, that is, the number of rotations per minute (hereinafter simply referred to as the engine rotational speed) from the frequency of the rectangular wave.

The CPU 118 also has a brake switch 126
is connected. This brake switch 126
emits a different electrical signal depending on whether the brake pedal 128 is in the original position or in the depressed state, and the CPU 118 determines whether the brake is in the applied state or not based on the output signal of the brake switch 126. can be detected.

The microcomputer 116 is equipped with a memory 130 in addition to the CPU 118, and this memory 13
0 stores a control program for the CPU 118 as well as a control pattern for the modulating solenoid 98. In other words, when changing gears, the hydraulic pressure of the actuator 40a (42a is the same) is
After first disengaging the forward clutch 40 by changing the clutch as shown in the figure, the second clutch 46 is simultaneously engaged while disengaging one of the transmission clutches, for example, the first clutch 44, and then the forward clutch is slowly disengaged. 40, and the duty ratio control pattern of the modulating solenoid 98 for that purpose is stored.

The memory 130 also stores a control pattern for the modulating solenoid 98 for preventing engine stall. That is, as shown in FIG. 1, the duty ratio is maintained at 0% and the forward clutch 40 (reverse clutch 42
) are fully connected,
If the load on the transmission side is excessive relative to the engine output, the engine speed will drop as shown in , but if the speed falls below a certain level, engine stall will occur, so Slightly higher first reference rotation speed, e.g. 400rpm
When the engine speed drops to , the duty ratio is suddenly increased to 60% as shown in
Thereafter, as shown in , the engine speed is gradually decreased as the engine speed recovers, and when the engine speed has recovered to a second reference speed, for example 700 rpm, which is a certain value higher than the first reference speed and slightly lower than the idling speed, A control pattern for the duty ratio that is reduced to 0% is stored as shown in FIG.

In the device configured as above, the CPU
118 is a solenoid drive circuit 114 that operates in different ways depending on the signal from the brake switch 126.
control.

First, control in a state where the brake switch 126 is issuing a signal indicating that the brake pedal 128 is not depressed will be described. In this case, if the duty ratio is rapidly increased as shown by , the actuator oil pressure is rapidly reduced to 3 kg/cm ² as shown by . This oil pressure of 3Kg/ ^cm2 is applied to the forward clutch 40
Rather than completely disengaging the reverse clutch 42 (the same applies to the reverse clutch 42), the engine 10 is kept in a state where it can transmit a certain amount of torque, and the load on the engine 10 is lowered by slipping the forward clutch 40, causing the engine to rotate. The value has been selected to allow for recovery in numbers. Therefore, the engine speed recovers, but as the duty ratio decreases with this recovery, the actuator oil pressure increases as shown in FIG. increases. Then, when the engine speed recovers to the second reference speed 700 rpm, the duty ratio is rapidly increased as shown in FIG. Transmissible torque increases. As a result, the load on the engine 10 becomes excessive compared to the output of the engine 10, so that the engine speed decreases again as shown in FIG. 1 and 2.

As is clear from the above explanation, in this embodiment, control to increase the duty ratio to 60% is performed by setting the actuator oil pressure to 2.
The control is to reduce the duty ratio to ⁰ %, and the control to reduce the duty ratio to 0% is the control to increase the actuator oil pressure to 15Kg/cm ² as the second set oil pressure.

However, in the example shown in Fig. 1, even if control is performed to reduce the duty ratio to 0%, due to the response delay, the actuator oil pressure will not actually rise to the second set oil pressure of 15 kg/ ^cm2 . The engine speed drops to the first reference speed of 400 rpm,
Since control to lower the actuator oil pressure is started, the actuator oil pressure does not actually rise to the second set oil pressure.

In this way, each time the engine speed reaches the first reference speed and the second reference speed, the actuator oil pressure decreases and increases repeatedly, and the torque that can be transmitted by the forward clutch 40 repeatedly decreases and increases. It will be. This prevents engine stall from occurring and also ensures that a certain amount of torque is always applied from the engine 10 to the direct power train. This torque repeatedly increases and decreases as described above, but since this increase and decrease is controlled in relation to the engine speed, for example, when the road surface is steeply sloped, the driver must press the accelerator pedal. By depressing the pedal more or less if the slope is gentle, the vehicle can be maintained in a state where it neither moves forward nor backward. That is,
This allows the forward clutch 40 or the reverse clutch 42 to play a role similar to a torque converter in a direct power train. In addition, as mentioned above, even when the actuator oil pressure is at its lowest, a certain amount of torque is transmitted from the engine, so there is no play in the meshing parts of the gears that make up the direct power train. The resulting increase in operating noise is also avoided.

Note that if the output of the engine 10 is increased by depressing the accelerator pedal while the forklift truck is stopped as described above, the engine speed will increase.
Even if the actuator oil pressure reaches 700 rpm and is increased, the engine speed does not decrease, so the actuator oil pressure is increased to the maximum oil pressure and kept in contact, and the forklift truck starts moving.

Above, we have explained the operation when the brake pedal 128 is not depressed, but when the brake pedal 128 is depressed, the CPU 1
18 detects this fact based on a signal from brake switch 126 and reduces the actuator oil pressure to a minimum level. That is, the modulator 74 is so controlled via the solenoid drive circuit 114 that the forward clutch 40 (or reverse clutch 42) is disengaged. As a result, the forward clutch 40 or reverse clutch 42 is kept in a half-clutch state until it is not necessary because the brake is being applied, and unnecessary wear on these clutches is avoided. .

Although one embodiment of the present invention has been described in detail above,
This is literally an example, and the present invention may be implemented in other embodiments.

For example, in the above embodiment, the transmission is of a constant mesh type, and a forward clutch 40 and a reverse clutch 42 are provided as clutches that connect and disconnect power transmission from the engine to the transmission. However, even if the transmission is of the selective sliding type and only has one clutch that connects and disconnects the transmission of power from the engine to the transmission, it is necessary to The present invention can be applied to any device that is automatically operated by.

Furthermore, although the present invention is most effective when applied to power transmission devices for industrial vehicles such as forklift trucks, it can also be widely applied to power transmission devices for various vehicles such as trucks and passenger cars.

Furthermore, in the embodiment described above, the duty ratio is gradually decreased and the actuator oil pressure is increased while the engine speed recovers from the first reference speed to the second reference speed, so that the clutch transmission The advantage is that the time in which the possible torque is extremely small is the shortest. It is also possible that the duty ratio is kept constant during recovery and then gradually reduced.

Furthermore, in the above embodiment, the second reference rotation speed was set to a rotation speed slightly lower than the idling rotation speed, but the first reference rotation speed and the second reference rotation speed may be set to the idling rotation speed as the second reference rotation speed. The rotation speed can be appropriately selected depending on surrounding conditions.

Further, in the above embodiment, whether or not the brake is in the operating state is detected based on the position of the brake pedal, but for example, if the brake device is a hydraulic brake device, the hydraulic pressure It is possible to detect whether the brake is applied by other means, such as by using a pressure switch to detect that the pressure has increased above a certain level.

Although not illustrated in detail, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

Effects of the Invention As is clear from the above description, the present invention reduces the oil pressure of the actuator that engages and disengages the clutch when the engine speed drops to the first reference speed when the brake is not applied. As a result, when the engine speed recovers to the second reference speed, the actuator oil pressure is increased, and as the actuator oil pressure increases, the engine speed increases. When the actuator oil pressure decreases, the process of lowering the actuator oil pressure is repeated, which prevents the engine speed from dropping beyond the reference speed and prevents the occurrence of engine stall. be able to.

Moreover, since the clutch is maintained in a state where it can transmit a certain amount of torque, the vehicle is not completely unrestrained and becomes unstable. In other words, a state similar to when the torque converter is slipping can be obtained by controlling the actuator hydraulic pressure, and the vehicle will not move backwards even on a sloped road surface, regardless of the driver's awareness. This also prevents play from occurring in the meshing portions of the gears, which would cause operational noise.

In addition, hysteresis is provided between the engine rotation speed at which the actuator oil pressure is reduced (first reference rotation speed) and the engine rotation speed at which the actuator oil pressure is increased (second reference rotation speed), so that the clutch is extremely short. The occurrence of hunting, which repeatedly disconnects and disconnects over time, is avoided.

In addition, when the engine speed drops to the first reference speed, control is performed to lower the oil pressure to a preset first setting, and when the engine speed recovers to the second reference speed, the oil pressure is lowered to the preset oil pressure. All you have to do is control the oil pressure to raise it to the second set oil pressure.
In order to control the actuator oil pressure, it is sufficient to detect the engine rotation speed, and the occurrence of engine stall can be prevented with a simple device.

Additionally, when the brakes are activated,
The actuator oil pressure is not controlled as described above, and the clutch is disengaged when the actuator oil pressure is sufficiently lowered, thereby avoiding unnecessary slippage of the clutch and wear and shortening of its life.

[Brief explanation of the drawing]

1 and 2 are graphs showing the state of clutch control of a power transmission system (direct power train) for a forklift truck, which is an embodiment of the present invention. FIG. 2 is a diagram conceptually showing the entire power transmission device. FIG. 3 is a circuit diagram showing a hydraulic circuit of the power transmission device. FIG. 4 is a diagram schematically showing details of the modulator shown in FIG. 3. FIG. 5 is a block diagram showing the electrical control portion of the power transmission device. FIG. 6 is a graph showing the control status of the actuator oil pressure at the time of starting in the power transmission device. 12... Pump, 14... Planetary gear unit, 40... Forward clutch, 40a, 42
a, 44a, 46a, 48a... Actuator, 42... Reverse clutch, 72... Regulator, 74... Modulator, 98... Modulating solenoid, 100, 102, 104
... Directional switching valve, 106, 108 ... Shift solenoid, 114 ... Solenoid drive circuit, 116
... Microcomputer, 118 ... CPU (Central Processing Unit), 120 ... Sensor, 122 ... Gear, 124 ... Waveform shaping circuit, 126 ... Brake switch, 128 ... Brake pedal, 130
……memory.

Claims (1)

[Scope of Claims] 1. A method for automatically controlling a clutch in a vehicle power transmission system in which an automatic transmission is directly connected to an engine by a clutch without using a torque converter, the method comprising: When the brake is in a non-applied state, (a) detecting that the engine speed has decreased to a first reference speed that is set slightly higher than the engine speed at which engine stall occurs; and (b) ) Based on the detection signal, the hydraulic pressure of the actuator that connects and disconnects the clutch is in a state in which the clutch transmits torque, but slips to an extent that allows the engine speed to recover from the first reference speed. (c) when the engine rotation speed has recovered to a second reference rotation speed higher than the first reference rotation speed, the oil pressure of the actuator is lowered to the first reference rotation speed; the clutch is maintained in a disengaged state when the brake is in an applied state, while repeating the step of controlling the oil pressure to increase to a second set oil pressure that is preset to a higher value than the first set oil pressure. A clutch automatic control method for a vehicle power transmission device.