JPH04302751A - Output torque absorbing device for vehicle - Google Patents

Abstract

PURPOSE:To eliminate jump-out feeling and shock similar to engine stall at the time of starting by using a traction control device. CONSTITUTION:The controller 24 is provided, which includes pressure sensors 9b and 9c for detecting differential pressure between the high and low pressure sides of a fluid pressure circuit 9a so as to determine the change of rate DELTAP of differential pressure detected by these pressure sensors 9b and 9c while brake signals are being outputted to the duty valve 22 of a traction control device based on the change of rate, so that a band brake 20 is thereby operated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a hydraulic continuously variable transmission (H
The present invention relates to an output torque absorption device used to improve the starting characteristics of vehicles equipped with ST) or hydromechanical continuously variable transmissions (HMT).

0002

[Prior art] HST, HMT, etc. have a pair of pumps/
The motors are connected by a hydraulic circuit and one pump/motor
The pump/motor is configured to transmit engine power input to the motor to the other pump/motor and output it to the drive wheels. and,
When the vehicle starts, the pump/motor on the side directly connected to the drive wheels
The engine is controlled so that the volume of the pump/motor on the side driven by the engine is maintained at its maximum and the volume of the pump/motor driven by the engine is gradually increased from zero. For this reason, the engine side pump/
During the time lag between when the motor starts rotating and the pump/motor on the driving wheel side starts swallowing an appropriate amount of pressurized fluid, the pressure on the high pressure side of the hydraulic circuit transiently increases. It will rise. However, in reality, a relief valve is provided in the hydraulic circuit to release high-pressure fluid, so the pressure on the high-pressure side does not rise above the relief set pressure.

[0003] With such a configuration, HST and HM
At T, there is a characteristic that the output torque at the time of starting theoretically reaches the maximum value expressed by relief set pressure x maximum motor volume, regardless of the throttle valve opening. For this reason, there is an inconvenience that at the beginning of starting the vehicle, the driver feels as if the vehicle is jumping even though he or she has hardly stepped on the accelerator. Moreover, at the moment when the hydraulic pressure circuit reaches its maximum value and the relief valve opens, the sudden increase in output torque that had been up to that point immediately disappears, giving the driver a shock similar to engine stalling. become. Conventionally, in order to alleviate or eliminate these inconveniences, a new device was added to bypass the high-pressure fluid to the low-pressure side before the hydraulic circuit reached the relief pressure, thereby reducing the engine output energy. I tried to reduce the output torque while discarding it.

0004

[Problem to be Solved by the Invention] However, when such a device is provided, a bypass circuit that short-circuits the high pressure side and the low pressure side of the hydraulic circuit, a valve mechanism that selectively opens and closes this bypass circuit, etc. are required. This has the disadvantage that the hydraulic circuit becomes complicated.

[0005] Therefore, the present inventor investigated whether it is possible to suppress the output torque by conventional mechanical means, and focused on a traction control device. This device is conventionally installed in vehicles as a slip prevention means when the output torque becomes excessive when the vehicle starts, etc. It is a device that detects the rotation difference between the driving wheel and the driven wheel and makes a slip judgment. and a brake mechanism that can apply braking to a portion directly mechanically connected to the drive wheels. When a slip is determined, the brake mechanism is feedback-controlled to suppress rotation of the drive wheels.

However, this device only operates when the output torque increases to a value that causes the drive wheels to slip, and by that time the pressure on the high pressure side of the hydraulic circuit has already reached the relief set pressure. It is usual that it is reached. For this reason, with conventional traction control devices, it is impossible to prevent the above-mentioned jerky feeling at the beginning of the start or a shock similar to engine stalling.

The present invention has been made with attention to such problems, and is a torque absorbing device that can effectively reduce the output torque at the time of starting using a conventional traction control device. is intended to provide.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration.

That is, the output torque absorption device for a vehicle according to the present invention connects a pair of pumps/motors through a hydraulic circuit, and transfers engine power input to one pump/motor to the other pump/motor. - a continuously variable transmission that transmits the signal to the motor and outputs the signal to the drive wheels; and a traction control system that applies braking to the parts directly mechanically connected to the drive wheels using a brake mechanism when a brake signal is input. a pressure sensor for determining the rate of change in the differential pressure between the high pressure side and the low pressure side of the hydraulic pressure circuit; The present invention is characterized in that the traction control device is provided with a controller that outputs a brake signal.

In this case, preferably, the controller compares the differential pressure change rate with a threshold value corresponding to the throttle opening, and outputs a brake signal to the traction control device only when the threshold value is exceeded. It is best to configure it so that

[0011]

[Operation] It is generally difficult to detect the output torque in automatic vehicles, but in vehicles equipped with HST or HMT, the differential pressure between the high pressure side and the low pressure side of the hydraulic circuit is proportional to the output torque of the drive wheels. do. Therefore, by detecting the pressure, the output torque can be measured. However,
This invention uses a pressure sensor and a controller to output a brake signal to a traction control device in accordance with the rate of change in differential pressure between the high pressure side and the low pressure side. For this reason, for example, if the accelerator is hardly depressed, if the rate of change in the rise of the output torque is large, the greater the braking is applied to the drive wheels, the faster the brakes will jump out due to feedforward control. This is similar to an engine stall in that the hydraulic pressure circuit gradually increases toward relief pressure, and the moment it reaches that point, the change in output torque suddenly decreases. It also eliminates the shock that comes with it.

[0012] In particular, when the controller is configured to initiate control by making the rate of change in differential pressure correspond to a threshold value, the output torque is suppressed even though the driver has the intention of accelerating. Such inconveniences will also be resolved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a traction control device used in the present invention, and FIG. 2 shows a vehicle equipped with a hydromechanical continuously variable transmission equipped with the traction control device. The hydromechanical continuously variable transmission was proposed by the applicant in Japanese Patent Application No. 1-279439, and is composed of a sun gear 1, a planetary gear 2, and a ring gear 3, and an engine 6 is connected to the planetary gear 2 via an input shaft 4. a planetary gear mechanism 5, a low-speed mechanical transmission system a formed in the direction from the planetary gear 2 toward the sun gear 1, and the planetary gear 2, with the planetary gear mechanism 5 as the main body.
A high-speed mechanical transmission system b is formed in the direction from the to the ring gear 3, and one fluid pump/motor is provided near the transmission end of the low-speed transmission system a with respect to these mechanical transmission systems a and b.
By connecting the input/output shaft 7a of the motor 7 and the input/output shaft 8a of the other fluid pump/motor 8 near the transmission end of the high-speed transmission system b, A fluid transmission mechanism 9 mainly composed of a hydraulic circuit 9a forming variable speed fluid transmission systems A and B in parallel, and a transmission end of the low speed transmission system a are connected via a common rotating element 24 and a differential gear 11. A low-speed clutch CL that connects and disconnects the output shaft 10, and a high-speed clutch CH that connects and disconnects the transmission end of the high-speed transmission system b to the output shaft 10 via the common rotating element 24 and the differential gear 11. It will be equipped. CF is a forward clutch, and when moving forward, sun gear 1 is used.
is connected to the low-speed transmission system a, and serves to disconnect the sun gear 1 from the low-speed transmission system a only when reversing.

[0015] However, in this continuously variable transmission, the input shaft 4
Engine power is input to the output shaft 10, and drive torque is extracted from the output shaft 10, and the drive wheels 12 are driven by the drive torque. At that time, each clutch CL, CH,
By switching the CFs in a predetermined combination, it is possible to select either the low speed mode or the high speed mode. In other words, when moving forward at low speed, clutches CL and CF are "on" and clutch CH is "off" to divide the engine power in parallel at the time of input, and a portion is sent to the output shaft through the mechanical transmission system a on the low speed side. 10, and the rest can be transmitted to the output shaft 10 through the fluid transmission system A. Also, when driving at high speeds, by setting clutches CH and CF to "on" and clutch CL to "off", part of the engine power is transmitted to the output shaft 10 through the mechanical transmission system b on the high speed side, and the rest can be transmitted to the output shaft 10 through the fluid transmission system B.

In addition, the illustrated device is set to a top lock-up mode (a mode in which the vehicle runs while maintaining the speed ratio represented by the output rotation speed/input rotation speed at the maximum value), and the sun gear 1 is By applying braking, the hydraulic transmission system B is locked during high-speed running, and this causes the mechanical transmission system B on the high-speed side to lock.
It is possible to transmit power only through this system, achieving high efficiency through pure mechanical drive. Also, with this device,
Clutch CL is "engaged" when reversing at low speed, clutches CH, C
F is set to "off" so that all engine power is transmitted to the output shaft 10 only through the fluid transmission system A. At this time, in order to prevent power circulation from occurring and preventing proper output from being obtained, sun gear 1 is also braked to enable pure hydraulic drive with less loss. .

It should be noted that braking of the sun gear 1 is performed through a band brake 20. This band brake 20 includes a brake drum 20a that is rotatably provided on the sun gear 1.
A band 20b is wound around the braking surface of the ring gear 3 so as to surround the outer periphery of the ring gear 3, and the band 20b is tightened by an actuator 21, which will be described later. 30 is a boost pump that backs up the hydraulic circuit 9a.

[0018] The hydromechanical continuously variable transmission having such a configuration has traditionally had the problem that no matter how small the amount of accelerator depression, the output torque temporarily becomes excessive when starting, causing the drive wheels 12 to slip. It becomes. Therefore,
A traction control device shown in FIG. 1 is provided. This device was developed by the applicant in Japanese Patent Application No. 3-33297.
The band rake 20 was newly proposed in
A single-acting cylinder actuator 21 (also used for lock-up) tightens the band brake 20, and pressurized fluid is supplied to the actuator 21 to tighten the brake.
Pump 30 (boot of the hydraulic circuit 9a) that generates pressure
(using a stop pump) and a duty valve 2 for regulating the pressure fluid flowing from the pump 30 to the actuator 21.
2 are provided. Then, the rotational speeds of the driving wheel 12 and the driven wheel (not shown) are input from the rotational speed sensor 23 to the controller 24, and the controller 24 calculates the slip ratio of the driving wheel 12 with respect to the driving wheel. A duty pulse (brake signal) is sent to the duty valve 22 based on the ratio. That is, when the duty valve 22 is used, by changing the duty ratio as shown in FIG. 3, a pressure proportional to the duty ratio can be generated in the cylinder chamber of the actuator 21. Therefore, simply thinking about it, it is sufficient to input a brake signal having a larger duty ratio as the slip of the driving wheels 12 becomes more severe. In this way, from the band brake 20 to the sun gear 1.
When braking is applied, sun gear 1 and drive wheel 1 are
2 are directly connected via the differential gear 11, the braking force is also applied to the drive wheels 12, and as a result,
The rotation speed of the drive wheels 12 is suppressed, and slip prevention is effectively achieved.

The difference between this traction control device and the conventional device is that the band brake 20 is attached to the differential gear 11 which performs a torque amplifying action.
As a result, the pump 30 can be replaced with the existing low pressure boost pump 30 as described above. In addition, by eliminating the need for high-pressure liquid, the problem of noise generation caused by flow path switching can be solved. As a result, it becomes possible to use the duty valve 22 instead of the conventional solenoid valve, which simplifies piping and improves resolution related to traction control. Furthermore, when the band brake 20 is not operated, it is only necessary to slightly relieve low-pressure fluid through the relief valve 31, which reduces energy loss and improves the efficiency of the entire system. There are also advantages.

[0020] Therefore, the torque absorbing device of this embodiment has the following characteristics:
The traction control device is constructed as follows using such a traction control device. That is, the hydraulic circuit 9a
are provided with pressure sensors 9b and 9c for detecting pressure on the high pressure side and pressure on the low pressure side, and the differential pressure therebetween is input to the controller 24. In addition, although not shown in the drawings, signals relating to throttle opening, accelerator opening, vehicle speed, etc. are also input to the controller 24 as appropriate. And this controller 24
performs predetermined calculations according to a program stored inside, and inputs a duty pulse, which is a brake signal, to the duty valve 22.

FIG. 4 is a flowchart showing the outline of the program.
It is a chart diagram. The control performed by the controller 24 will be explained below with reference to this flowchart. Note that in this program, due to the accuracy of the vehicle speed sensor, if the detected value is 1 km/h or less, the vehicle is considered to be stopped. Additionally, it has been empirically known that the transient phenomenon in which the hydraulic pressure circuit 9a reaches the relief set pressure regardless of the throttle opening degree occurs concentratedly in the vehicle speed range from 0 to 5 km/h. Based on this, it is determined whether the control of the present invention is to be performed depending on whether the actual vehicle speed is within the vehicle speed range. Furthermore, the following control is configured based on the empirical rule that such a transient phenomenon always occurs once during normal driving operations and never occurs more than once.

When the program starts, first in step S1 it is determined whether or not the accelerator pedal is being depressed. If YES, the vehicle speed is set to 5km/h in step S2.
It is determined whether or not the pressure change rate ΔP is less than or equal to h. If YES here, it is determined in step S3 whether the pressure change rate ΔP is larger than the threshold value β. The pressure change rate ΔP is the pressure sensor 9
It is determined by the time differentiation of the differential pressure input through terminals b and 9c. Further, the threshold value β is predetermined as a function of the throttle opening, and the value corresponding to the actual throttle opening is extracted and used for comparison. If YES here, it indicates that the pressure change rate ΔP exceeds the driver's intention to accelerate by some extent. For this reason, step S
4, a duty pulse having a predetermined magnitude as a function of ΔP is outputted to the duty valve 21, and the tightening force of the band brake 20 is adjusted. Thereafter, a flag is set in step S11 and the process returns. Moreover, when it is determined NO in step S1, the process moves to step S5, and it is determined whether the vehicle speed is 1 km/h or less. If YES, the driver has no intention of accelerating,
In addition, since the vehicle is considered to be stopped, in preparation for when the pressure in the hydraulic circuit 9a rises transiently in the near future, there is a control delay until the pressure rises, and a control until the band brake 20 is activated. In order to avoid a delay, a slight duty pulse is applied to the duty valve 22 in step S6 (the band 20b is set in a state in which the band 20b is in slight sliding contact with the brake drum 20a or not). On the other hand, if the determination in step S5 is NO, this indicates that the vehicle is moving although the driver has no intention of accelerating. Therefore, it is necessary to determine in step S2 whether the vehicle speed is 5 km/h or not, and if YES, perform the same control as described above. Further, if the determination in step S2 is NO, this indicates that the transition period in which pressure abnormality occurs in the hydraulic circuit 9a regardless of the throttle opening has passed. Therefore, the process moves to step S7, where the duty pulse applied to the duty valve 22 is gradually reduced (meaning every time this step S7 is passed thereafter), and the tightening force is released. Thereafter, in step S8, the counter is decremented and the process returns. Note that when the count value becomes 0 in this step S8, the flag is reset. Further, if the determination in step S3 is NO, the hydraulic circuit 9a
This shows that the differential pressure change rate ΔP is within the range of the driver's intention to accelerate. Therefore, the process moves to step S9 to check whether the flag is set. If NO, as in step S6, a pressure abnormality in the hydraulic circuit 9a may occur in the near future, so a slight duty pulse is applied to the duty valve 22 in step S10. If the determination in step S9 is YES, it is assumed that the pressure abnormality will never occur again, so the process moves to step S7 and the same control as described above is performed.

According to such an output torque absorbing device,
As the differential pressure change rate ΔP of the hydraulic pressure circuit 9a increases, the tightening force of the band brake 20 can be increased, and greater braking can be applied to the drive wheels 12. The control is feed-forward to changes in output torque. For this reason,
It is possible to eliminate the feeling of jumping out when starting, and also eliminate the shock caused by the sudden decrease in output torque when the hydraulic pressure circuit 9a reaches the relief pressure. Also, using this device,
It can be easily constructed by simply using a conventional traction control device, and has the effect of eliminating the need for a bypass circuit and a valve mechanism provided in the hydraulic circuit 9a. Further, this controller 24 is configured to initiate control by making the differential pressure change rate ΔP correspond to the threshold value β. Therefore, it is possible to eliminate the inconvenience that the output torque is suppressed even though the driver has the intention of accelerating. Further, in this case, duty pulses related to conventional traction control control are inputted in parallel to the duty valve 22. Therefore, measures to be taken when the drive wheels 12 slip in a vehicle speed range of 5 km/h or more can be taken as before.

It should be noted that the present invention is not limited to the above embodiments. For example, instead of using the existing boost pump, a different pump can be used. In this case, it may be driven by an electric motor or the
It may also be connected to the output shaft of the engine in a two-stage arrangement with the stop pump. In addition, the actuator for tightening the band brake
It is also possible to provide a separate one for lock-up. Further, the traction control device applied to this torque absorbing device is not limited to the illustrated example, but includes, for example, a drum brake in which the brake mechanism is directly incorporated into the drive wheel. Furthermore, in the above embodiment, the rate of change in the differential pressure in the hydraulic circuit is actually obtained from the difference between the pressure on the high pressure side and the pressure on the low pressure side, but when the change in pressure on the low pressure side is small, There is no problem in extracting only the pressure on the high pressure side and finding its rate of change. Furthermore, although the above embodiment is an embodiment applied to HMT, it is of course applicable to HST. others,
Various modifications can be made without departing from the spirit of the invention.

[0025]

[Effects of the Invention] Since the torque absorbing device of the present invention has the above-mentioned configuration, it can reduce the shock caused by the feeling of jumping out when the vehicle starts and the transient pressure increase in the hydraulic circuit compared to the conventional traction control device. This can be easily and reliably resolved by using Therefore, it is possible to eliminate the need for complex components such as a bypass circuit that short-circuits high and low pressures and a valve mechanism that opens and closes this circuit, which have been conventionally provided in a hydraulic circuit.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing a traction control device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a vehicle equipped with a hydromechanical continuously variable transmission to which the embodiment is applied.

FIG. 3 is a characteristic diagram of the duty valve used in the same example.

FIG. 4 is a flowchart showing an overview of control performed in the embodiment.

[Explanation of symbols]

6...Engine 7, 8...Pump/motor 9a...Hydraulic pressure circuit 9b, 9c...Pressure sensor 12...Drive wheel 20...Brake mechanism (band brake) 24...Controller

Claims (1)

[Claims] Claim 1: A device in which a pair of pumps/motors are connected by a hydraulic circuit, and engine power input to one pump/motor is transmitted to the other pump/motor and output to drive wheels. A vehicle comprising a step-change transmission and a traction control device that applies braking to a portion directly mechanically connected to the driving wheels by a brake mechanism when a brake signal is input. A pressure sensor for determining the rate of change in the differential pressure between the high pressure side and the low pressure side of the hydraulic circuit, and outputting a brake signal to the traction control device according to the rate of change in the differential pressure determined through the pressure sensor. 1. An output torque absorption device for a vehicle, characterized in that it is provided with a controller.