JPH07117148B2 - Hydraulic control device for continuously variable transmission for vehicles - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a vehicle continuously variable transmission, and particularly to a technique for promptly operating the continuously variable transmission to the maximum gear ratio side when the vehicle is suddenly braked. It is about.

BACKGROUND ART A pair of variable pulleys provided on an input shaft and an output shaft and having a variable effective diameter, a transmission belt wound around the pair of variable pulleys, and a pair of hydraulic actuators for changing the effective diameter of the variable pulleys. In a continuously variable transmission for a vehicle equipped with a hydraulic control device of a type in which hydraulic gear is supplied to the hydraulic actuator to reduce the gear ratio and hydraulic oil is discharged from the hydraulic actuator to increase the gear ratio. Are known. In such a type of hydraulic control device, in order to start the vehicle with the continuously variable transmission set to the maximum gear ratio, it is necessary to hold the continuously variable transmission to the maximum gear ratio side in advance when the vehicle is stopped. Therefore, normally, when the input shaft rotation speed of the continuously variable transmission falls below a predetermined value, the hydraulic oil in the hydraulic actuator on the input side (drive side) of the continuously variable transmission is released (maximum gear ratio holding valve). Thus, the gear ratio of the continuously variable transmission is preferentially set to the maximum value by being released. For example, JP-A-60-14
This is the hydraulic control device for a belt-type continuously variable transmission described in No. 9551.

Problems to be Solved by the Invention By the way, in such a conventional hydraulic control device, the release valve is released based on the input shaft rotation speed of the continuously variable transmission. If the line resistance until opening and the friction between the transmission belt and the variable pulley are large, there will be a delay from the time the opening valve is opened until the speed ratio of the continuously variable transmission changes to the actual maximum speed ratio side. Sometimes it is unavoidable. Therefore, in the case where the wheel rotation rapidly stops in a sudden braking state of the vehicle, particularly when the wheel is locked by braking on a slippery road surface, the transmission of the continuously variable transmission can be maintained even when the vehicle is stopped. In some cases, the maximum gear ratio cannot be reached, and when the vehicle restarts after such sudden braking, there is a drawback that sufficient driving force cannot be obtained.

Means for Solving Problems The present invention has been made against the above circumstances.
The gist thereof is that a pair of variable pulleys provided on the input shaft and the output shaft and having a variable effective diameter, a transmission belt wound around the pair of variable pulleys, and an effective diameter of the variable pulley are changed. In a continuously variable transmission for a vehicle having a pair of hydraulic actuators, the hydraulic oil is supplied to one of the hydraulic actuators to reduce the gear ratio, and the hydraulic oil is discharged from the hydraulic actuators through a plurality of valves. (1) A drain release valve which is directly connected to the hydraulic actuator and is capable of releasing the hydraulic oil in the hydraulic actuator to a drain. Control means for releasing the drain release valve when the deceleration of the vehicle exceeds a predetermined value and the vehicle speed becomes equal to or less than a predetermined value The lies in the fact that contain.

Action and Effect of the Invention It is possible to detect a sudden braking state at a low vehicle speed prior to the stop of the vehicle based on the fact that the deceleration of the vehicle exceeds the predetermined value and the vehicle speed becomes equal to or less than the predetermined value. Therefore, the drain opening valve can be opened earlier to open the hydraulic actuator to the drain than in the case where the opening valve is opened based on the rotation speed of the drive pulley of the continuously variable transmission. Therefore, the gear ratio of the continuously variable transmission is set to the maximum gear ratio even when the vehicle is suddenly braked on a road surface having a low friction coefficient, so that sufficient driving force can be obtained even when the vehicle restarts after the sudden braking.

The control means is preferably a suitable engine based on the vehicle speed and the accelerator pedal operation amount when the vehicle speed is equal to or higher than a predetermined value even if the deceleration of the vehicle exceeds a predetermined value. The gear ratio for obtaining the braking action is determined, and the gear ratio of the continuously variable transmission is changed to this gear ratio.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 2, the power of the engine 8 includes a fluid coupling 10, a belt type continuously variable transmission (hereinafter, referred to as CVT) 12, an auxiliary transmission 14,
Drive shaft 20 through intermediate gear unit 16 and differential gear unit 18
Is transmitted to the drive wheel 21 connected to the.

The fluid coupling 10 is fixed to the pump 24 connected to the crankshaft 22 of the engine 8 and the input shaft 26 of the CVT 12, and is connected to the pump 24.
A turbine 28 rotated by oil from the engine and a lockup clutch 32 fixed to the input shaft 26 via a damper 30 are provided. The lockup clutch 32 is operated, for example, when the vehicle speed, the engine rotation speed, or the rotation speed of the turbine 28 becomes a predetermined value or more, and directly connects the crankshaft 22 and the input shaft 26.

The CVT 12 includes variable pulleys 36 and 38 provided on the input shaft 26 and the output shaft 34, respectively, and the variable pulleys 36 and 38.
And a transmission belt 40 wound around 38. The variable pulleys 36 and 38 are provided on the fixed rotating bodies 42 and 44 fixed to the input shaft 26 and the output shaft 34, respectively, and on the input shaft 26 and the output shaft 34 so as to be movable in the axial direction and non-rotatable around the shaft. The movable rotors 46 and 48 are moved by the hydraulic cylinders 50 and 52 to change the width of the V groove, that is, the hanging diameter (effective diameter) of the conduction belt 40. Gear ratio γ (= rotation speed N _in of input shaft 26 / rotation speed N of output shaft 34
_out ) is changed. Therefore, when the hydraulic oil is made to flow into the hydraulic cylinder 50 or the hydraulic oil in the hydraulic cylinder 50 is made to flow out, the gear ratio γ of the CVT 12 is changed and the inflow speed or the outflow speed of the hydraulic oil is changed. The speed of change of the gear ratio γ is changed by the adjustment. In addition, the hydraulic cylinder 52 is operated by the hydraulic pressure adjusted in accordance with the actual throttle valve opening and the gear ratio γ so that the minimum narrow pressure can be obtained exclusively in the range where the transmission belt 40 does not slip. To be The oil pump 54 constitutes a hydraulic pressure source of a hydraulic control device which will be described later, and is constantly rotatably driven by the engine 8 connected to the crankshaft 22 via a connecting shaft (not shown) that longitudinally passes through the input shaft 26. It

The auxiliary transmission 14 includes a planetary gear device and reverses the rotational torque transmitted from the output shaft 34 of the CVT 12 in response to a shift operation for moving the vehicle backward. Output gear of sub transmission 14
60 is connected to the differential gear device 18 via the intermediate gear device 16, and the power of the engine is distributed to the left and right drive shafts 20 in the differential gear device 18 and then transmitted to the left and right drive wheels 21. It

FIG. 3 is a hydraulic control circuit for controlling the vehicular power transmission system shown in FIG. 2, and shows only a portion related to the present invention. In the figure, a control oil passage 62 guides the control oil pressure generated by a pressure adjusting valve (not shown) for driving the spool valve element of each valve. The gear ratio control valve device 64 for controlling the gear ratio of the CVT 12 is a shift direction switching valve.
It consists of a speed changeover valve 68 and a speed changeover valve 68. Speed change direction valve 66
Is to connect the hydraulic oil supplied from the line oil passage 74 to the inflow oil passage 70 and to close the outflow oil passage 72, the outflow oil passage 72 to the drain port 76, and the inflow oil passage 70. A spool valve element 78 that can be selectively positioned between the closed second position, a spring 80 that biases the spool valve element 78 toward the second position, and a spring of the spool valve element 78.
Control oil chamber that applies the control oil pressure to the end surface opposite to 80
82 and. The control oil chamber 82 is connected to the control oil passage 62 via the throttle 84, and an electromagnetic opening / closing valve 86 that opens the downstream side of the throttle 84 to the drain for controlling the operating position of the spool valve 78 is a control oil chamber. Connected with 82. On the other hand, the speed change valve 68 includes a communication passage 88 communicating with the hydraulic cylinder 50 and the inflow oil passage 70, and a throttle passage 92 communicating with the communication passage 88 via a throttle 90 and the outflow oil passage 72. A first position for controlling the flow of hydraulic oil between the first passage and the communication passage 88 and the inflow oil passage 70 and closing the throttle passage 92 and the outflow oil passage 72. A spool valve member 94 that is located at a second position that closes the communication passage 88 and the inflow oil passage 70 and opens the throttle passage 92 and the outflow oil passage 72, and the spool valve member 94 Spring biasing toward 1 position
96 and a control oil chamber 98 for applying the control oil pressure to the end surface of the spool valve element 94 opposite to the spring 96.
The throttle 90 imparts a relatively small flow resistance in order to set the maximum oil outflow amount from the hydraulic cylinder 50. The control oil passage 98 is connected to the control oil passage 62 through the throttle 100, and the electromagnetic opening / closing valve 102 that opens the downstream side of the throttle 100 to the drain in order to control the operating position of the spool valve 94 is a control oil chamber. Connected with 98.

Therefore, when the spool valve element 78 of the speed change direction switching valve 66 is moved to the first position or the second position in response to turning on or off of the electromagnetic opening / closing valve 86, the inside of the hydraulic cylinder 50 on the input side (driving side). The hydraulic oil is made to flow into the hydraulic cylinder 50 or hydraulic oil is made to flow out of the hydraulic cylinder 50 to reduce or increase the speed change ratio γ of the CVT 12. In addition, the solenoid valve 10
When the spool valve 78 of the speed changeover valve 68 is moved to the first position and the second position in response to turning on and off of 2, the hydraulic oil flow rate that is flown into the hydraulic cylinder 50 is the maximum flow rate or the minimum flow rate. Flow rate or hydraulic cylinder 50
The flow rate of the hydraulic oil discharged from the inside is the minimum flow rate or the maximum flow rate. The minimum flow rate of the hydraulic oil that flows into the hydraulic cylinder 50 is substantially determined by the throttle 104 formed in the spool valve element 94, and the minimum flow rate of the hydraulic oil that flows out from the hydraulic cylinder 50 is the operation within the hydraulic cylinder 50. The oil is substantially determined by the gap formed between the movable rotary body 46 and the input shaft 26 by a predetermined amount. The solenoid on-off valve 102 is normally duty-controlled to continuously change the working oil between the maximum flow rate and the minimum flow rate.

Further, the communication passage 88 is provided with a drain release valve 106 that directly releases the hydraulic oil in the hydraulic cylinder 50 to the drain. The drain release valve 106 has a second position for opening the communication passage 88 to the drain port 108 and the drain port 108 of the communication passage 88.
To the first position for closing the opening to the valve, a spring 112 for biasing the spool valve 110 toward the second position, and a spring 112 for the spool valve 110 A control oil chamber 114 for applying a control oil pressure is provided on the side end surface. The control oil chamber 114 has a throttle
An electromagnetic opening / closing valve 118, which is connected to the control oil passage 62 via 116 and opens the downstream side of the throttle 116 to the drain in order to control the operating position of the spool valve element 110, is connected to the control oil chamber 114. . Therefore, when the solenoid on-off valve 118 is in the off state, the spool valve element 110 can be moved to the first position, so that the hydraulic oil in the hydraulic cylinder 50 cannot flow directly to the drain, but the solenoid on-off valve 118 is in the on state. Spool valve 1
Since 10 is moved to the second position, the hydraulic oil in the hydraulic cylinder 50 is directly discharged to the drain.

FIG. 4 shows an electronic circuit for controlling the operation of the above hydraulic control device. An electronic control unit 120 provided with a so-called microcomputer including a CPU, a RAM, a ROM, etc. corresponds to the control means of the present embodiment, in which the throttle valve opening θ _th (%) from each sensor, CVT12 output shaft 34
Rotation speed of N _out (rotation speed of input side rotary shaft of auxiliary transmission 14
n _in ), a rotational speed N _in of the input shaft 26 of the CVT 12, an engine cooling water temperature T _w , and a shift lever operating position P, respectively. The CPU in the electronic control unit 120 processes an input signal according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM, and the shift direction switching electromagnetic on-off valve 86, the shift speed switching electromagnetic on-off valve 102, Drain release valve 1
A signal for driving the electromagnetic on-off valve 118 for controlling 06 is output via the amplifier 122, respectively.

In the electronic control unit 120, by executing a main routine (not shown), initialization is performed and input signals from each sensor are read, and then the input shaft 26 of the CVT 12 is read based on the read signals. Rotation speed
N _in , the rotational speed N _out of the output shaft 34, the vehicle speed V, the throttle valve opening θ _th , the shift lever operating position P, etc. are determined, and various controls are selectively or sequentially executed according to the input signal conditions. It With the gear ratio control of CVT12, the engine 8
To operate on the minimum fuel consumption curve, a target rotation speed is determined based on the actual throttle valve opening θ _th and the vehicle speed V based on the relationship obtained in advance, and the target rotation speed and the actual input shaft rotation speed N _in The electromagnetic open / close valves 86 and 102 are operated to change the gear ratio γ so that FIG. 1 shows a part of the above gear ratio control related to the present invention, in which the CVT12 is provided in preparation for restarting the vehicle even during sudden braking.
7 shows a control flowchart for surely setting the gear ratio of 1 to the maximum value.

The operation will be described below with reference to the flowchart of FIG. First, in step S1, the vehicle deceleration α is calculated based on the rate of change of the vehicle speed V, and
At S2, it is determined whether the deceleration α of the vehicle is larger than a predetermined value α ₀ . This step S2 is for judging sudden braking of the vehicle, and the value α ₀ is selected to a value at which the gear ratio γ cannot be changed to the maximum value in the conventional hydraulic control device. When the deceleration α is not larger than the predetermined value α ₀ , the maximum gear ratio can be obtained when the vehicle is stopped even by the normal gear ratio control.
In step S3, the gear ratio control during rapid deceleration is released and the content of the flag F indicating the control is reset to "0", and in step S4 the normal gear ratio control is returned. As a result, as described above, the target rotational speed and the actual input shaft rotational speed N determined based on the actual throttle valve opening θ _th and the vehicle speed V from the relationship obtained in advance.
_The gear ratio γ is controlled so that in matches.

If it is determined in step S2 that the vehicle deceleration α is greater than the preset value α ₀ , step S2
In step 5, the execution of the gear ratio control during sudden deceleration is commanded, the content of the flag F is set to "1", and it is determined in step S6 whether the vehicle speed V is higher than a predetermined value V _0. To be done. If the vehicle speed V is still higher than V ₀ , in step S7, the actual throttle valve opening θ _th and the gear ratio γ (θ _th , V) determined based on the vehicle speed V are actually calculated from the relationship obtained in advance. The gear ratio γ of is changed. The above value V ₀ is set to a low vehicle speed of, for example, about 5 to 8 km / h. Further, the above relationship is shown in, for example, FIG. 5, and the gear ratio γ is forcibly forced during the sudden braking.
Before the maximum gear ratio, that is, the vehicle speed is still V ₀
It is determined that a proper engine braking effect can be obtained in a larger condition.

While the above steps are repeatedly executed, the vehicle speed V decreases, and when it is determined in step S6 that the vehicle speed V becomes equal to or lower than the predetermined value V ₀ , the solenoid opening / closing valve 118 is turned on in step S8. As a result, the drain opening valve 106 is opened to release the operating oil pressure in the hydraulic cylinder 50 through the drain opening valve 106, and the gear ratio γ of the CVT 12 is set to the operating state of the gear ratio control valve device 64 for restarting. Regardless, the maximum value is set preferentially and rapidly.

As described above, according to the present embodiment, when the vehicle speed V becomes lower than V ₀ during the sudden braking of the vehicle, the hydraulic oil in the hydraulic cylinder 50 is released through the drain release valve 106, and the gear ratio γ of CVT 12 is increased. Since it is preferentially set to the maximum value, compared to the conventional case in which the hydraulic oil in the hydraulic cylinder 50 is released based on the rotation speed of the drive side pulley becoming equal to or lower than a predetermined value,
The hydraulic oil in the hydraulic cylinder 50 can be released early. Therefore, the gear ratio of the continuously variable transmission is set to the maximum gear ratio even when the vehicle is suddenly braked on a road surface having a low friction coefficient, so that sufficient driving force can be obtained even when the vehicle restarts after the sudden braking.

Further, according to the present embodiment, when the vehicle speed V is higher than V ₀ when the vehicle is suddenly braked, the gear ratio determined based on the actual throttle valve opening θ _th and the vehicle speed V from the relationship obtained in advance. Since the gear ratio of the CVT 12 is changed so as to be γ (θ _th , V), there is an advantage that a suitable engine braking action can be obtained before the gear ratio of the CVT 12 is maximized.

The embodiment of the present invention has been described above with reference to the drawings.
The present invention also applies to other aspects.

For example, in the above-described embodiment, the deceleration α of the vehicle is calculated based on the rate of change of the vehicle speed V, but the deceleration may be detected by an accelerometer.

Further, although the CVT 12 in the above-mentioned vehicle is a single-row belt type, it may be a double-row belt type CVT or a cone type other type CVT.

The above description is merely one embodiment of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining an essential part of the operation of one embodiment of the present invention. FIG. 2 is a skeleton diagram showing a power transmission device according to an embodiment of the present invention. FIG. 3 is a diagram showing a main part of a hydraulic control circuit in the apparatus shown in FIG. Figure 4 is second
FIG. 3 is a block diagram showing a circuit provided in the device shown in the figure.
FIG. 5 is a diagram showing the relationship used in the flowchart of FIG. 12: Belt type continuously variable transmission 26: Input shaft, 34: Output shaft 36, 38: Variable pulley 40: Transmission belt 50: Hydraulic cylinder (hydraulic actuator) 106: Drain release valve 120: Electronic control unit (control means)

Claims (2)

[Claims] 1. A pair of variable pulleys having variable effective diameters provided on an input shaft and an output shaft, a transmission belt wound around the pair of variable pulleys, and a pair of variable pulleys for changing the effective diameters of the variable pulleys. In a continuously variable transmission for a vehicle equipped with a hydraulic actuator, by supplying hydraulic oil to one of the hydraulic actuators to reduce the gear ratio, and discharging hydraulic oil from the hydraulic actuator through a plurality of valves. A hydraulic control device of a type for increasing a gear ratio, the drain release valve being directly connected to the hydraulic actuator, capable of releasing hydraulic oil in the hydraulic actuator to a drain, and a deceleration of the vehicle being predetermined. A control means for releasing the drain release valve when the vehicle speed exceeds a predetermined value and becomes lower than a predetermined value. Hydraulic control device for a continuously variable transmission. 2. The control means, when the vehicle speed is equal to or higher than a predetermined value even if the deceleration of the vehicle exceeds a predetermined value, engine braking is performed based on the vehicle speed and the accelerator pedal operation amount. The hydraulic control device for a vehicle continuously variable transmission according to claim 1, wherein a gear ratio for obtaining the action is determined, and the gear ratio of the continuously variable transmission is changed to this gear ratio.