JPH0447177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a power transmission system for a vehicle, and more particularly to a method for controlling oil pressure of a clutch engagement/disengagement actuator.

BACKGROUND OF THE INVENTION Vehicle power transmission devices in which gear shifting is performed automatically are already known. Conventionally, the transmission was commonly connected to the engine via a torque converter, but this type of power transmission device has limitations in improving transmission efficiency and acceleration, so in recent years Recently, power transmission systems in which the transmission is directly connected to the engine via a clutch without using a torque converter (hereinafter referred to as a direct power train) have been reconsidered.

However, with a torque converter, even if there is a certain degree of discrepancy in the rotational speed or torque between the engine and transmission sides, the torque converter's buffering action absorbs the discrepancy, resulting in a smooth start. Although it is easy to achieve gear changes, direct power trains do not have such a buffering effect, so smooth starts and gear changes cannot be achieved unless the control precision of each device is improved.

One of them is the control of a solenoid duty-controlled modulator. This modulator is a type of hydraulic control valve that is connected to an oil passage that supplies oil pressure to the actuator for clutch engagement and disconnection, and adjusts the oil pressure by draining hydraulic oil from the oil passage to the drain passage. By changing the duty ratio of the solenoid, the ratio between the open time and the closed time of the valve changes, thereby controlling the amount of hydraulic oil drained. In other words, statically, there is a one-to-one correspondence between the duty ratio of the modulating solenoid and the hydraulic pressure of the clutch engagement/disconnection actuator, and dynamically, the hydraulic pressure follows changes in the duty ratio with a certain time delay. It is something that changes. However, when we experimented by attaching such a modulator to a direct power train, we found that it can be used when a clutch that is engaged is temporarily disengaged for a gear shift and then reengaged, or when a clutch that is disengaged is disengaged when the vehicle is started. It was discovered that the clutch was not connecting smoothly enough when the clutch was in the closed state, and as a result of tracing the cause, it was found that the duty ratio of the modulating solenoid was 0% or
It has been found that this is because when the value is changed from 100% to another value, there is a significantly longer delay in changing the oil pressure of the clutch engagement/disengagement actuator than in other cases.

Problems to be Solved by the Invention As described above, the present invention, in a direct power train, uses the conventional actuator for clutch engagement and disengagement when changing the clutch from a disengaged state to an engaged state, or from an engaged state to a disengaged state. This was done to solve the problem that the hydraulic control is not ideal and therefore the clutch does not connect smoothly.

Means for Solving the Problems In order to solve the above problems, the present invention provides the following steps when controlling the hydraulic pressure of the clutch engagement/disconnection actuator using a solenoid duty control modulator in a direct power train. When the clutch is changed from the engaged state to the disengaged state or from the disengaged state to the engaged state, the duty ratio of the modulating solenoid of the modulator is set to a value that exceeds the target duty ratio from the previous duty ratio, that is, the previous duty ratio. is 0
%, the duty ratio is set to a value larger than the target duty ratio, and if the duty ratio was 100%, the duty ratio is set to a value smaller than the target duty ratio, and the stage is maintained at that value for a certain period of time. It was established.

It should be noted that the target duty ratio herein means a duty ratio obtained by approximating a curve representing an ideal oil pressure change of the clutch engagement/disengagement actuator, taking into account a constant time delay as a whole.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Figure 3 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,
If the planetary gear unit 14 of this embodiment is divided into a clutch that transmits or interrupts the rotation of the engine 10 and a transmission that controls speed change, we get
The forward clutch 40 and the reverse clutch 42 constitute a clutch, and the remaining portion constitutes a transmission.

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. Further, the rotation speed of the engine 10 is detected by a rotation sensor 64, and the vehicle speed is detected by a rotation sensor 66. In addition, although not shown, each sensor detects the accelerator opening, the load, the stroke of the inching pedal, the tilt angle of the vehicle body, whether the shift lever is in the neutral position, whether the brake pedal is being operated, etc. and based on those detection results, the clutch 40,
By selectively connecting any one of 42, 44, 46, and 48, the forklift truck is automatically started and shifted.

The hydraulic circuit for this purpose is shown in FIG. A pump 12 connected to the engine 10 sucks hydraulic oil from a tank 70 and pumps the clutches 40, 42,
44, 46 and 48 actuators 40a,
42a, 44a, 46a and 48a. The hydraulic pressure supplied to these is provided by the regulator 72.
The hydraulic pressure supplied to actuators 40a and 42a of forward clutch 40 and reverse clutch 42 is further controlled by modulator 74.

The modulator 74 includes the regulator 72 and the actuator 40a or 4, as shown in FIG.
A drain passage 78 is provided for draining hydraulic oil to the tank 70 from a main passage 76 that connects the tank 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 9
The oil pressure at 0 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 directional control valve 100 is connected to a shift lever (not shown), and when the shift lever is in the neutral position, hydraulic oil is not supplied to either of the actuators 40a, 42a, and the shift lever is operated to the forward or reverse position. When this happens, hydraulic fluid is supplied to the corresponding actuators.

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 operate in the drain passage 1 by energizing shift solenoids 106 and 108, respectively.
When the shift solenoids 106 and 112 are opened, the state shown in FIG. 4 is achieved, and the shift solenoids 106 and 1
08 are respectively switched to the opposite state when demagnetized. That is, depending on whether the solenoids 106, 108 are on or off, hydraulic oil is supplied to any of the actuators 44a, 46a, and 48a, thereby connecting the first clutch 44, second clutch 46, or third clutch 48. This is becoming more and more common.

The on/off states of the shift solenoids 106, 108 and the modulating solenoid 98 are controlled by a microcomputer based on a control program and signals from each sensor. Further, since it is not essential for understanding the present invention, illustration and detailed description will be omitted.

In a forklift truck equipped with a power train configured as described above, when the shift lever in the neutral position is operated toward the forward side and the accelerator pedal is depressed to start the forklift truck,
The duty ratio of the modulating solenoid 98 is changed over time as shown in FIG. In other words, when the forklift truck is stopped, the duty ratio of the modulating solenoid 98 is maintained at 100%;
At time t ₀ the duty ratio is reduced to D ₃ %,
After being held at that value until time t ₁ , D is increased to ₁ %, after which it is decreased at a constant rate until time t ₂ , and after reaching the duty ratio D ₂ % at time t ₂ , it is kept constant. It remains at that value for a time and is reduced to 0% at time _t3 . Along with this, the actuator 40a of the forward clutch 40
The oil pressure changes as shown in FIG. Although there is a slight delay from time t ₀ , the oil pressure rises relatively quickly to P ₁ , and then rises to P ₂ at a certain rate and is maintained at that value for a certain period of time, after which the oil pressure rises at the set oil pressure of the regulator 72. The oil pressure can be quickly raised to a certain maximum oil pressure _P3 . While the oil pressure is raised from P ₀ to P ₁ to P ₂ , the forward clutch 40 is smoothly connected and the forklift truck is smoothly started, and the oil pressure rise curve shown in FIG. 2 is as follows. Although ideal,
If the duty ratio is decreased at the same rate from time t ₀ to t ₁ as from time t ₁ to t ₂ , as shown by the dashed-dotted line A in FIG. 1, as shown by the dashed-dotted line B in FIG. As such, there is a large delay in the rise of the oil pressure, and thus an ideal oil pressure rise curve cannot be obtained. On the other hand, as shown in Figure 1, time
From t ₀ to t ₁ , the duty ratio is first set to a duty ratio D ₃ %, which is considerably smaller than the target value (the value represented by the dashed line A), and then kept constant at that duty ratio D ₃ %. After holding it for a short time, the ideal oil pressure fluctuation curve shown in Fig. 2 is obtained by resetting the target value to approximately D ₁ %, and the forward clutch 4
0 allows a smooth transition from the disconnected state to the connected state in a short period of time.

The loading load of the forklift truck is small,
In addition, if the road surface is level, the forward clutch 40 will be fully engaged if the hydraulic pressure of the actuator 40a is increased to _P2 , so even if the hydraulic pressure is immediately increased to _P3 from this state, However, if the load of the forklift truck is large, or if the running resistance is large, such as when the road surface is uphill, the forward clutch 40 may still be activated immediately after the oil pressure reaches _P2 . Since a considerable degree of slippage has occurred in the forklift truck, if the oil pressure is suddenly increased to _P3 in this state, the slippage of the forward clutch 40 will be abruptly stopped, and at this point an acceleration shock will occur in the forklift truck. Combined with the acceleration shock that occurs in the process of increasing the oil pressure from _P1 to _P2 , the shock occurs twice, resulting in poor riding comfort. Therefore, in this embodiment, the oil pressure is P ₂
After reaching P2, when the slippage of the forward clutch 40 can be practically ignored by maintaining the oil pressure _P2 for a certain period of time, the oil pressure is increased to _P3 and acceleration shocks occur twice. This is prevented.

As described above, when the shift lever is operated to the forward side and at the same time the accelerator pedal is depressed, the engine 10
We have explained a normal start in which the output torque of the engine is increased, but in the case of a so-called idling start in which the shift lever is operated to the forward side without the accelerator pedal being depressed, the duty ratio is 6th.
As shown in the figure, the duty ratio D ₄ % is maintained at a constant constant for a relatively long time from t ₀ to t ₁ , and then it is decreased in a constant comparison. By maintaining the duty ratio at a constant value for a relatively long time in this way, the hydraulic pressure supplied to the actuator 40a of the forward clutch 40 is relatively quickly applied, as shown in FIG.
It rises to P ₄ and then further rises to t ₂ as the duty ratio decreases, bringing the forward clutch 40 into the engaged state. In order to bring the forward clutch 40 from the disengaged state to the engaged state in the shortest possible time without applying a large load to the engine that may cause engine stop, the oil pressure is shown in FIG. It is desirable to raise the clutch in a nearly straight line, but if the duty ratio itself is reduced linearly from 100%, there will be a significant time delay in the rise of the oil pressure, causing the forward clutch 40 to engage. While it takes a long time to reach the state, as shown in Figure 6,
By keeping the duty ratio at a constant duty ratio _D4 smaller than the target value shown by the dashed-dotted line C for a relatively long time from t ₀ to t ₁ , the oil pressure is smoothly and quickly increased to P ₄ , and then the duty ratio is increased. By decreasing the constant comparison over time, the oil pressure can be increased to a value _P2 sufficient to engage the forward clutch 40, and eventually the oil pressure can be increased in a nearly ideal state to move forward. This makes it possible to quickly and smoothly bring the clutch 40 into the engaged state without applying an overload to the engine 10 that would cause the engine to stop.

The case where the forklift truck is started in the forward direction has been described above, but when the forklift truck is started in the reverse direction, the actuator 4 of the reverse clutch 42 is used instead of the forward clutch 40.
The oil pressure of 2a is controlled. Since this control is almost the same as that for forward movement, detailed explanation will be omitted.

FIGS. 8 and 9 show control when the forward clutch 40, which has been in the engaged state, is once disengaged for gear shifting and then brought back into the engaged state. In this case, it is necessary to reduce the oil pressure of the actuator 40a of the forward clutch 40 as quickly as possible, but as shown in FIG.
If the duty ratio is only approximated to the oil pressure change curve shown in FIG. 9 by taking into account a certain time delay as shown in FIG. 9, the oil pressure will decrease until the forward clutch 40 is completely disengaged. It takes a long time to do this, making it difficult to control the hydraulic pressure accurately. Therefore, in this embodiment, the duty ratio is set to a value larger than the target duty ratio indicated by the dashed line E.
D ₅ and is maintained at that value from time t ₀ to t ₁ , and the actuator 40
The oil pressure at a is quickly lowered. When the oil pressure has almost reached a value at which the forward clutch 40 is completely disengaged, the duty ratio is reset to the target duty ratio _D1 , and thereafter is decreased at a constant rate as time passes. The oil pressure also begins to rise at a constant rate, and the forward clutch 40 is brought into contact. After this stage, please refer to Figures 1 and 2.
As described above with reference to the figures, the explanation will be omitted here, but when the forward clutch 40 is disengaged, either of the directional control valves 102, 104 is switched and a gear change is performed.

Although one embodiment of the present invention has been described in detail above,
This is literally an example. For example, the transmission is not a constant mesh type but a selective sliding type, and the clutch is also a normal friction clutch that is commonly used in combination with the transmission. The present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, such as applying the present invention to the control of a direct power train in which the power train is only automated.

Effects of the Invention As detailed above, the present invention allows the duty ratio of the modulating solenoid to be adjusted to the target duty ratio when the clutch is changed from the engaged state to the disengaged state or from the disengaged state to the engaged state in a direct power train. Rather than setting the target duty ratio, it is set to a value that exceeds the target duty ratio and maintained at that value for a certain period of time, so if the duty ratio is changed from 0% or 100% to another value. The tendency for a particularly large time delay to occur in comparison with other cases is canceled out, and the oil pressure of the actuator for clutch engagement/disengagement is adjusted in a state close to an ideal curve, so that the clutch is smoothly engaged at the appropriate time. As a result, smooth gear shifting or starting can be achieved with less shock.

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of duty ratio control of a modulating solenoid in one embodiment of the present invention, and FIG. 2 is a graph showing corresponding changes in oil pressure of a clutch engagement/disconnection actuator. FIG. 3 is a conceptual diagram showing an example of a direct power train to which the method of the present invention can be applied. FIG. 4 is a circuit diagram showing a hydraulic circuit for actuating the actuator of each clutch in FIG. 3. FIG. 5 is an explanatory diagram showing the modulator in FIG. 4. FIG. 6 is a graph showing the duty ratio control during idling start in one embodiment of the present invention, and FIG. 7 is a graph showing the corresponding oil pressure change. FIG. 8 is a graph showing the duty ratio control during gear shifting, and FIG. 9 is a graph showing the corresponding oil pressure change. 12: pump, 14: planetary gear unit, 40: forward clutch, 40a, 42a: actuator, 42: reverse clutch, 72: regulator, 74: modulator, 76: main passage, 78: drain passage, 80: relief valve, 82: Benko, 84, 88: Spring, 8
6: Piston, 90: Hydraulic chamber, 92: Solenoid on-off valve, 94: Throttle, 96: Control passage, 98: Modulating solenoid, 100, 102, 1
04: Directional switching valve, 106, 108: Shift solenoid.

Claims (1)

[Scope of Claims] 1. In a vehicle power transmission system in which the engine and the automatic transmission are directly connected by a clutch without going through a torque converter, the hydraulic pressure of the actuator for connecting and disconnecting is controlled by a solenoid duplex. A control method using a clutch control type modulator, wherein when the clutch is changed from an engaged state to a disengaged state or from a disengaged state to an engaged state, the duty ratio of the modulating solenoid of the modulator is changed to the previous duty ratio. 1. A hydraulic control method for a clutch engagement/disconnection actuator, comprising a step of setting the duty ratio to a value that exceeds a target duty ratio and maintaining that value for a certain period of time.