JP5341041B2 - Hydraulically driven vehicle and method and apparatus for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation of fuel consumption and excessive acceleration when a sudden and big accelerator operation is executed for the start or the acceleration in a vehicle such as a forklift in which power from an engine is transmitted to driving wheels via an HST (a closed circuit in which a variable displacement hydraulic pump and a hydraulic motor are connected to each other). <P>SOLUTION: In the forklift 1 provided with a power train 10 having the HST 21, an accelerator operation control unit 15a inputs the actual accelerator operation quantity 5a, and generates the accelerator operation quantity 11b for control in which the rate of increase per unit time of the actual accelerator operation quantity 5a is limited to the predetermined limit value. The accelerator operation quantity 11b for control is increased more smoothly during the sudden increase of the actual accelerator operation quantity 5a. An engine controller 11 controls an engine 13 based on the accelerator operation quantity 15c for control. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a hydraulically driven vehicle (for example, a forklift) and its control.

  A vehicle having an engine, a hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device (for example, driving wheels) driven by the hydraulic motor is known (for example, a patent) Reference 1). Typical examples are found in industrial vehicles, agricultural machinery and construction machinery. In such a vehicle, for example, in its power train (driving power transmission device), a hydrostatic transmission (hereinafter referred to as HST) is used to transmit the power from the engine to the drive wheels. The In general, an HST is composed of a variable displacement hydraulic pump (hereinafter referred to as “HST pump”) and a variable or fixed displacement hydraulic motor (hereinafter referred to as “HST pump”) interconnected to form a closed hydraulic circuit. HST motor "). In principle, HST has advantages such as energy loss is extremely small compared to HDT (Hydrodynamic Transmission) typified by a torque converter, the gear can be steplessly shifted, and has a braking function.

  The HST incorporated in the vehicle powertrain transmits the power from the engine to the drive wheels of the vehicle as follows. When the engine is driven, the HST pump mechanically connected to the engine is driven. When the hydraulic fluid is supplied from the HST pump to the HST motor, the HST motor rotates. Further, the HST motor drives and rotates the drive wheels of the vehicle.

  A vehicle having an HST further has a control system. In recent years, electronic control systems have been favored. The control system controls the fuel injection amount to the engine and the capacity of the HST pump in response to an accelerator operation such as an accelerator pedal provided in the vehicle. Thereby, the pressure and flow rate of the HST pump are controlled, and the torque and rotational speed of the drive wheels of the vehicle are controlled.

  The control system disclosed in Patent Document 1 determines whether the accelerator operation amount is smaller or larger than a predetermined limit value for the purpose of improving fuel efficiency when the vehicle speed is in a low speed range and improving vehicle speed response. When the accelerator operation amount is smaller than the predetermined limit value, the rate of change of the engine rotation speed according to the change in the accelerator operation amount is comparatively small, and when the accelerator operation amount is larger than the predetermined limit value, The engine is controlled so that the rate of change of the engine rotation speed due to the change in the accelerator operation amount becomes relatively large. This control system also controls the capacity of the HST pump according to the rotational speed of the engine.

JP-A-9-301016

  A typical example of a vehicle having an HST is a forklift. When starting or greatly accelerating a forklift, the driver may suddenly perform a large accelerator operation (typically depressing the accelerator pedal to the maximum at a stroke).

  However, in the case of a forklift having an HST, if such a sudden and large accelerator operation is performed, the following two problems arise. One of them is that the actual fuel consumption is worse than that expected for the design of the vehicle. The other is that excessive acceleration occurs so that the driver feels that the vehicle “jumps out”. Acceleration that feels like “jumping out” causes inconveniences such as load collapse and difficulty in approaching when loading on a fork.

  These problems will occur not only with forklifts but also with other types of vehicles. However, forklifts often stop and start frequently during unloading work, etc., and to prevent damage and damage to the load, forklifts carry extra impacts and loads on the load carried by the fork. It is necessary to avoid collapse. Therefore, the solution of the above two problems is particularly important in forklifts.

  Accordingly, an object of the present invention is to start a vehicle at low speed or start at low speed in a hydraulically driven vehicle, such as a forklift, configured to transmit power to a load device through hydraulic power transmission represented by HST. This is to prevent deterioration of fuel consumption and excessive acceleration that is too strong even when a sudden and large accelerator operation is performed, such as during acceleration from the state.

  A vehicle provided according to an embodiment of the present invention includes an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor. (For example, driving wheels), an actual accelerator operation amount is input, and an increase rate per hour of the actual accelerator operation amount is limited to a preset limit value, thereby controlling the accelerator operation for control. In accordance with the accelerator operation control means for generating the amount and the control accelerator operation amount from the accelerator operation control means, the larger the control accelerator operation amount, the higher the engine speed at which the same engine output torque can be obtained. And an engine control means for controlling the engine.

  According to this vehicle, the accelerator pedal is suddenly depressed for sudden start or acceleration of the vehicle, and the actual accelerator operation amount increases rapidly (especially at an increase rate per hour higher than the predetermined upper limit value). Even in such a case, the control accelerator operation amount used for engine control increases more slowly than the actual accelerator operation amount (that is, at an increase rate per hour corresponding to the upper limit value). Along with the slow increase in the control accelerator operation amount, the engine speed increases at an increase rate per hour such that the increase in the absorption torque of the hydraulic pump can follow. Therefore, the absorption torque of the hydraulic pump increases along the expected increase characteristic line as the engine speed increases. As a result, an excessive increase in the rotational speed of the engine at the time of start is suppressed, fuel efficiency is improved, and excessive acceleration is also improved.

  Further, according to one embodiment of the present invention, the accelerator operation control means compares the actual accelerator operation amount with a value obtained by adding the limit value to the control accelerator operation amount, and determines the smaller value. Can be output as a new accelerator operation amount for control. Alternatively, as a modified example, the accelerator operation control means compares the actual accelerator operation amount with the control accelerator operation amount, and if the former is larger than the latter, sets the limit value to the control accelerator operation amount. The added value may be output as a new control accelerator operation amount. Otherwise, the former may be output as a new control accelerator operation amount.

  According to the vehicle configured as described above, the control accelerator operation amount can be generated by simple arithmetic processing such as comparison and addition.

  Further, in one embodiment of the present invention, the limit value is the increase in the engine rotation speed caused by the increase in the control accelerator operation amount at an increase rate per hour corresponding to the limit value. It is set within a range where the increase in HST pump capacity can be followed.

  As a result, even when the accelerator pedal is stepped on deeply due to sudden start or acceleration, the absorption torque of the hydraulic pump follows the increasing speed of the engine speed and the increase characteristic expected for its design The fuel consumption increases along the line, and deterioration of fuel consumption due to an excessive increase in engine rotation speed (so-called “engine blow-up”) can be prevented.

  In one embodiment of the present invention, the limit value is set such that the limit value increases as the current actual accelerator operation amount increases in accordance with the current actual accelerator operation amount.

  As a result, if the actual accelerator operation amount is large, the amount of increase in the control accelerator operation amount per hour also increases, so that the engine can be controlled according to the driver's intention.

  One embodiment of the present invention can be configured as a forklift. In a forklift, when the accelerator pedal is stepped on greatly at the time of starting, it is possible to reliably obtain a fuel-saving effect by suppressing an increase in engine speed and an effect of suppressing excessive acceleration (feeling of popping out). .

  The present invention also provides a control method and control apparatus for a hydraulically driven vehicle.

  According to the present invention, in a hydraulically driven vehicle configured to transmit power to a load device through hydraulic power transmission as typified by HST, such as a forklift, at the time of starting or in a low-speed traveling state It is possible to reduce fuel consumption deterioration and excessive acceleration when a sudden and large accelerator operation is performed, such as during acceleration from the vehicle.

The side view which shows the schematic external appearance of a forklift. 1 is a block diagram illustrating an example configuration of a powertrain with HST (several systems adjacent to the powertrain are also shown). The graph which shows the rotational speed-torque characteristic of the engine and HST pump of the vehicle with the power train which has HST, typically a forklift. The block diagram which shows the functional structural example of the power train with which the vehicle concerning one Embodiment of this invention is provided. In this embodiment, the graph which shows the mode of the increase in the amount of control accelerator operation when the actual amount of accelerator operation increases rapidly. The graph which shows the example of a setting of the limit value of the increase rate per hour of the accelerator operation amount in this embodiment. The graph which shows an example of the change of the actual accelerator operation amount 5a with progress of time, and an example of the change of the control accelerator operation amount 11b according to it. The flowchart which shows the process for determining the accelerator operation amount for control. The flowchart which shows the modification of the process for determining the accelerator operating amount for control.

  Prior to the description of the embodiments of the present invention, forklifts will be taken as an example to explain two problems that occur when performing the aforementioned sudden start or rapid acceleration.

  FIG. 1 shows a schematic appearance of a forklift. As shown in FIG. 1, the forklift 1 includes a drive wheel 3, an accelerator pedal 5, a forward / reverse switching lever 7, and the like.

  FIG. 2 shows a configuration example of a power train (power transmission mechanism for traveling) of a hydraulically driven vehicle (for example, forklift), in particular, a power train having an HST (in the figure, not only the power train, Several adjacent systems are also shown).

  As shown in FIG. 2, the powertrain 10 includes an accelerator pedal 5, a forward / reverse switching lever 7, an engine 13, an engine controller 11, an HST 21, an HST controller 15, a drive wheel system (differential, axle, and drive wheel) 31. . The HST 21 has a variable displacement type HST pump 23 (typically a swash plate type variable displacement pump is used) and a variable or fixed displacement type (variable displacement type in the illustrated example) HST motor 25. Both 23 and 25 are connected to each other via a hydraulic pipe 22 through which hydraulic oil flows to form a closed hydraulic circuit. The HST pump 23 is connected to the output shaft 9 of the engine 13 and is driven by the engine 13 to rotate. When hydraulic fluid is supplied from the HST pump 23 to the HST motor 25, the HST motor 25 is driven to rotate. The drive wheel system 31 is connected to the output shaft of the HST motor 25, and the HST motor 25 drives and rotates the drive wheel 3. Note that the output shaft 9 of the engine 13 is not limited to the HST pump 23 but also other hydraulic pumps (for example, in the case of a forklift, a hydraulic pump 27 for raising and lowering and tilting the fork and a brake device for driving the brake device). A hydraulic pump 29 etc.) can also be connected. The engine 13 may be one driven by various fuels such as a gasoline engine, a diesel engine, or an LPG engine.

  An example of a control operation that has been conventionally performed under such a configuration example of the power train 10 will be described below.

  An operation amount (actual accelerator operation amount) of the accelerator pedal 5 by the driver is detected as an electric signal by a sensor (for example, a potentiometer) (not shown) provided on the accelerator pedal 5. Further, the rotational speed of the engine 13 is detected as an electrical signal by a rotational speed sensor 14 provided on the output shaft 9 of the engine 13. The engine controller 11 receives an actual accelerator operation amount detection signal from the accelerator pedal 5 and a rotational speed detection signal from the rotational speed sensor 14. The engine controller 11 controls the fuel injection amount to the engine 13 in response to the detected accelerator operation amount and engine rotational speed, thereby controlling the output torque of the engine 13. Further, the engine controller 11 transmits a detection signal of the engine rotation speed detected by the rotation speed sensor 14 to the HST controller 15.

  The HST controller 15 determines the maximum absorption torque of the HST pump 23 based on the detection signal of the engine rotation speed received from the rotation speed sensor 14 through the engine controller 11, and outputs a maximum absorption torque command for instructing the maximum absorption torque. The electric signal is output to EPC (Electric Proportional Control) valves 17 and 18 for the HST pump. Here, one EPC valve 17 is a forward EPC valve 17 that functions when forward movement is selected by the forward / reverse switching lever 7, and the other EPC valve 18 is selected for backward movement by the forward / backward switching lever 7. It is a reverse EPC18 valve that works sometimes. The pump EPC valves 17 and 18 operate by receiving the maximum absorption torque command input from the HST controller 15 as an electrical signal, and hydraulically drive the HST pump capacity variable unit 20. The variable capacity unit 20 of the HST pump 23 has a capacity of the HST pump 23 (typical) so that the absorption torque of the HST pump 23 becomes an appropriate value within the range having the maximum absorption torque instructed by the maximum absorption torque command as an upper limit. Specifically, the angle of the swash plate is controlled.

  In the illustrated example, the capacity of the HST motor 25 is also controlled through the motor EPC valve 19 and the HST motor capacity variable unit 24 according to a command from the HST controller 15, but detailed description thereof is omitted here.

  FIG. 3 shows a typical example of rotational speed-torque characteristics of an engine 13 and an HST pump 23 of a vehicle, typically a forklift, having a power train 10 having an HST 21.

  A solid characteristic line (maximum output torque characteristic line) 51 shows a typical characteristic example of the maximum output torque corresponding to the rotational speed of the engine 13. Here, the maximum output torque of the engine 13 means the maximum torque that the engine 13 can output in a full throttle state where the accelerator operation amount is maximum.

  The operating point Li is a low idle point (that is, an operating point when the engine 13 operates at the minimum rotational speed, the accelerator operation amount is zero, and the transmission torque to the drive wheels 3 is also zero). The operating point Hi is a high idle point (that is, an operating point when the engine operates at the maximum rotational speed, the accelerator operation amount is maximum, and the transmission torque to the drive wheels 3 is zero).

  An alternate long and short dash line characteristic line (maximum absorption torque characteristic line) 53 is a typical characteristic of the maximum absorption torque of the HST pump 23 in accordance with the engine rotation speed, which is determined by the HST controller 15 as described with reference to FIG. An example is shown. The HST controller 15 outputs a torque value corresponding to the current engine speed on the maximum absorption torque characteristic line 53 as a maximum absorption torque command. Thereby, the absorption torque of the HST pump 23 is controlled within the range of the maximum absorption torque characteristic line 53 or less. The occasional absorption torque of the HST pump 23 varies within the range of the maximum absorption torque characteristic line 53 or less depending on the load applied to the drive wheels 3. However, when the forklift starts, the load applied to the drive wheels 3 is considerably large, and therefore the absorption torque of the HST pump 23 is often a value on or close to the maximum absorption torque characteristic line 53.

  A broken characteristic line (output torque characteristic line) 55 shows a typical characteristic example of the output torque of the engine 13 according to the rotational speed of the engine 13 when the actual accelerator operation amount is constant. That is, as described with reference to FIG. 2, the engine controller 11 controls the fuel injection amount to the engine 13 according to the accelerator operation amount and the engine rotation speed. Thus, the engine output torque is controlled so as to follow one output torque characteristic line 55 in the figure corresponding to the accelerator operation amount at each time. Such control is so-called all speed governor (ASG) control, and when the accelerator operation amount increases, the output torque characteristic line 55 moves to the right in the figure. That is, as the accelerator operation amount increases, the engine output torque increases at the same engine rotation speed, and the engine rotation speed increases under conditions where the same output torque is required. As one feature of ASG control in a forklift or construction machine, the gradient of the output torque characteristic line 55 (ratio of torque change to change in rotational speed) is set to a large value as shown in the figure. As a result, even if the external load fluctuates abruptly (even if the torque fluctuates abruptly), fluctuations in engine speed are small, and high workability is achieved for forklifts and construction machines with a large load fluctuation Can be secured. When the gradient of the output torque characteristic line 55 is set to be large in this way, the engine rotation speed is substantially determined according to the accelerator operation amount, and the engine rotation speed increases as the accelerator operation amount increases.

  A dotted characteristic line (fuel consumption characteristic line) 57 shows a typical characteristic example of the engine output torque according to the engine speed under the condition that the fuel consumption of the engine 13 is constant at a certain value. The fuel efficiency improves as the fuel efficiency characteristic line 57 is located on the upper left side in FIG. 3, and conversely, the fuel efficiency decreases as the characteristic line 57 is located on the lower right side in FIG. .

  Now, with reference to FIG. 2, a conventional control operation will be described on the assumption that the vehicle starts from a state where the accelerator operation amount is zero and the forklift is stopped. Initially, the operating point of the engine 13 is at a low idle point Li in FIG. Next, it is assumed that the driver depresses the accelerator pedal 5 at a maximum to start the forklift. In response to the rapid increase in the accelerator operation amount, the engine controller 11 rapidly increases the throttle opening or the fuel injection amount of the engine 13. As a result, the output torque characteristic line 55 of the engine 13 moves from the position passing through the first low idle point Li to the right in the drawing at once (that is, the engine output torque increases). As a result of the surplus torque generated, the rotational speed of the engine 13 increases. As the rotational speed of the engine 13 increases, the HST controller 15 increases the maximum absorption torque command of the HST pump 23 along the characteristic line 53. As a result, the capacity of the HST pump 23 increases.

  Since the load applied to the drive wheels 3 is considerably large at the time of starting, the absorption torque of the HST pump 23 is often a value on the maximum absorption torque characteristic line 53 or a value close thereto. Therefore, the matching operation point between the engine 13 and the HST pump 23 should shift from the first low idle point Li to the upper right in FIG. 3 along the maximum absorption torque characteristic line 53 of the HST pump 23. As a result, the rotational speed of the engine 13 does not increase to a very high value, the torque of the engine 13 increases rapidly, and the vehicle should start within a relatively fuel-efficient operating region.

  However, in practice, the expected result as described above does not occur.

  That is, there is a time delay that cannot be ignored after the maximum absorption torque command is issued from the HST controller 15 and before the capacity of the HST pump 23 is actually changed to the expected value based on the command. As a result of this time delay, the actual absorption torque increase characteristic line of the HST pump 23 becomes like the two-dot chain characteristic line 59 in FIG. 3, and has a gentler gradient than the maximum absorption torque characteristic line 53. It becomes. As a result, the rotational speed of the engine 13 increases to a very high value at a stretch, whereas the absorption torque of the HST pump 23 increases gently. Therefore, the actual fuel consumption at the time of start is worse than that expected for the vehicle design. That is, so-called engine squirting occurs and fuel is wasted. This is the first problem of the prior art described above.

  The second problem of the prior art is as follows. For comparison, in the forklift provided with the power train 10 having a torque converter instead of the HST 21, when the abrupt and large accelerator operation as described above is performed at the time of starting, the absorption characteristic increase characteristic line of the torque converter is This is indicated by another two-dot chain characteristic line 61 in FIG. The increase in the absorption torque of the torque converter indicated by the torque increase characteristic line 61 has a gentler slope than that of the HST pump 23 indicated by the characteristic line 59. However, when the forklift starts, a gentle increase in the absorption torque as shown in the torque increase characteristic line 61 rather generates an acceleration of an appropriate magnitude. The reason is that a gradual increase in torque as shown in the torque characteristic line 61 prevents accidents such as extra impact on the load supported on the fork and collapse of the load. Therefore, in the increase characteristic of the absorption torque of the HST pump 23 indicated by the torque increase characteristic line 59, the forklift having the HST may be excessively accelerated at the time of starting as compared with the forklift having the torque converter.

  From the above description, the occurrence mechanism of two problems in the prior art has been described. It will be apparent that the above two problems occur not only when starting, but also when accelerating from a low-speed running state.

  Next, a vehicle according to an embodiment of the present invention will be described.

  The vehicle of this embodiment (typically a forklift) also includes a power train 10 having the configuration shown in FIG. However, in this embodiment, the engine controller 11 and the HST controller 15 shown in FIG. 2 perform a control operation different from the conventional control operation already described with reference to FIG. The control operation in the present embodiment can be realized by a computer incorporated in the engine controller 11 and the HST controller 15 executing a computer program stored therein, or the engine controller 11 and It can be realized by a wired logic circuit incorporated in the HST controller 15 or can be realized by a combination of execution of a computer program and a wired logic circuit.

  FIG. 4 shows a configuration example of the power train 10 provided in the vehicle according to the present embodiment.

  Each of the engine controller 11 and the HST controller 15 includes a CPU, a memory, and other attached circuits that are programmed to perform a control operation described later. As shown in FIG. 4, the engine controller 11 includes an engine control unit 11a. The engine control unit 11a of the engine controller 11 receives the engine rotation speed 14a detected by the rotation speed sensor 14 and the control accelerator operation amount 11b output from the accelerator control unit 15a. The engine control unit 11a (particularly the ASG) increases the engine rotation speed at which the same output torque is output as the control accelerator operation amount 11b from the accelerator operation control unit 15a increases (in other words, More simply, as the control accelerator operation amount 11b is larger, the engine output torque characteristic line 55 is shifted to the right in FIG. 3, so that the engine speed increases as the control accelerator operation amount 11b increases. 2), the fuel injection amount of the engine 13 is controlled in accordance with the control accelerator operation amount 11b and the engine speed 14a.

  Here, the control accelerator operation amount 11b will be briefly described. When the driver suddenly depresses the accelerator pedal 5 to start or accelerate the forklift, the actual accelerator operation amount 5a increases at a very high rate of increase per hour in response to the rapid depressing of the accelerator pedal 5. On the other hand, the control accelerator operation amount 11b generated by the HST controller 15 increases at a preset rate of increase per time. Therefore, in this case, the control accelerator operation amount 11b increases more slowly than the actual accelerator operation amount 5a. The engine control unit 11a controls the engine 13 based on the control accelerator operation amount 11b.

  The HST controller 15 includes an accelerator operation control unit 15a and a pump control unit 15b. The actual accelerator operation amount 5 a detected by the accelerator pedal 5 is input to the accelerator operation control unit 15 a of the HST controller 15. (Here, in the present embodiment, the actual accelerator operation amount 5a is input to the engine controller 11 and notified to the HST controller 15 from there, but this is merely an example, and the actual accelerator operation amount 5a is It may be directly input to the HST controller 15.) The accelerator operation control unit 15a generates the control accelerator operation amount 11b based on the actual accelerator operation amount 5a. The generation method will be described later.

  The engine speed 14 detected by the speed sensor 14 and the forward, neutral or reverse command selected by the forward / reverse switching lever 7 are input to the pump controller 15b of the HST controller 15. (Here, in this embodiment, the engine rotation speed 14a is input to the engine controller 11 and notified from there to the HST controller 15, but this is merely an example, and the engine rotation speed 14a is directly set to HST. The pump control unit 15b may be configured so that the maximum absorption torque of the HST pump 23 increases as the engine rotational speed 14a increases in accordance with the maximum absorption torque characteristic line 53 shown in FIG. The maximum absorption torque of the HST pump 23 is determined according to the rotational speed 14a, and the maximum absorption torque command is output to the EPC valves 17 and 18 for the HST pump. Based on the maximum absorption torque command, the capacity of the HST pump 23 is controlled.

  By the way, the configurations of the engine controller 11 and the HST controller 15 shown in FIG. 4 are merely examples for explanation, and different configurations may be adopted. For example, the accelerator operation control unit 15a described above may exist in the engine controller 11 instead of the HST controller 15, or a part of the accelerator operation control unit 15a exists in the HST controller 15 and other parts. May be present in the engine controller 11. Alternatively, the engine controller 11 and the HST controller 15 may be configured as a single controller. However, the following description is based on the configuration shown in FIG.

  Next, the accelerator operation control unit 15a of the HST controller 15 described above will be described in more detail.

  The accelerator operation control unit 15a of the HST controller 15 generates the control accelerator operation amount 11b based on the actual accelerator operation amount 5a. The control accelerator operation amount 11b is smaller than the actual accelerator operation amount 5a in the time interval shown below, and is equal to the actual accelerator operation amount 5a in other cases. This time interval (that is, a time interval in which the control accelerator operation amount 11b is smaller than the actual accelerator operation amount 5a) is the time when the control accelerator operation amount 11b is equal to the actual accelerator operation amount 5a. The operation amount is started when the operation amount starts increasing at an increase rate per time higher than a preset limit value. The actual accelerator operation amount 5a increases at an increase rate per hour higher than the above limit value, whereas the control accelerator operation amount 11b has an increase rate per time corresponding to the above limit value (rather than the actual accelerator operation amount 5a). (Slowly) increase. Therefore, the control accelerator operation amount 11b is smaller than the actual accelerator operation amount 5a. Thereafter, when the control accelerator operation amount 11b increases and reaches the actual accelerator operation amount 5a, the increase in the control accelerator operation amount 11b stops and this time interval ends. Once the control accelerator operation amount 11b becomes equal to the actual accelerator operation amount 5a, thereafter, unless the actual accelerator operation amount 5a increases again at an increase rate per time higher than the limit value (in other words, the actual accelerator operation amount 5a). Even if the operation amount 5a is constant, decreases, or increases at an increase rate per hour equal to or less than the above limit value), the control accelerator operation amount 11b becomes equal to the actual accelerator operation amount 5a.

  In short, it can be said that the control accelerator operation amount 11b is a value obtained by limiting the rate of increase of the actual accelerator operation amount 5a per time to a predetermined limit value. When the actual accelerator operation amount 5a suddenly increases due to start or acceleration, the control accelerator operation amount 11b given to the engine control unit 11a gradually increases. Therefore, in this case, the absorption torque of the HST pump 23 follows the gradual increase of the control accelerator operation amount 11b, and rises substantially along the maximum absorption torque characteristic line 53 shown in FIG. As a result, the engine 13 can operate in a relatively good fuel efficiency region (a region of high output torque at a relatively low engine speed in FIG. 3). Further, when the forklift is suddenly started or accelerated, the engine speed does not increase, so that the problem of excessive acceleration is also improved.

  FIG. 5 illustrates an increase in the control accelerator operation amount 11b when the actual accelerator operation amount 5a increases at an increase rate per hour higher than the limit value.

  For example, when the actual accelerator operation amount 5a and the control accelerator operation amount 11b are both 0%, the actual accelerator operation amount 5a increases from 0% to 100% at a stretch as shown in the characteristic line 41. Assume that the rate increases at a rate. This is the case, for example, when the driver depresses the accelerator pedal from 0% to a maximum of 100%. In this case, as shown in the characteristic line 43, the control accelerator operation amount 11b increases at a rate of increase corresponding to a preset limit value (in the illustrated example, an increase step per unit time such as 100 milliseconds). In 43a), the acceleration gradually increases from the actual accelerator operation amount 5a, and when the actual accelerator operation amount 5a (for example, 100%) is reached, the increase is stopped.

  Next, it is assumed that the actual accelerator operation amount 5a increases at a rapid increase rate per hour between 0% and 40% as indicated by the characteristic line 45. This is the case, for example, when the driver steps on the accelerator pedal at a stretch from 0% to 40%. In this case, as shown in the characteristic line 47, the control accelerator operation amount 11b is a rate of increase per hour corresponding to a preset limit value (in the example shown, the actual accelerator operation is performed in the increase step 47a per unit time). When the actual accelerator operation amount 5a (for example, 40%) is reached thereafter, the increase is stopped gradually.

  Here, the limit value may be set to a constant value regardless of the current actual accelerator operation amount 5a, or the current actual accelerator operation as shown in the example of FIG. It may be variably set according to the amount 5a.

  A setting example in the case where the limit value is variably set in accordance with the current actual accelerator operation amount 5a will be described with reference to FIG.

  As exemplified by a characteristic line (limit value characteristic line) 49 in FIG. 6, the limit value (that is, the rate of increase in the accelerator operation amount per hour) increases as the current actual accelerator operation amount 5a increases. A limit value is set according to the current actual accelerator operation amount 5a. For example, the limit value when the current actual accelerator operation amount 5a is 100% is 0.7% / unit time, and the limit value when the current actual accelerator operation amount 5a is 40% is 0.46%. / Unit time, and so on. Generally, the driver wants the forklift to start or accelerate as the accelerator pedal operation amount 11b increases more quickly as the accelerator pedal is depressed more greatly. Therefore, as shown in FIG. 6, the limit value characteristic line 49 is set so that the limit value (that is, the rate of increase of the accelerator operation amount per hour) becomes larger as the actual accelerator operation amount 5a is larger. Has been.

  The limit value characteristic line 49 as shown in FIG. 6 can be implemented in the accelerator operation control unit 15a of the HST controller 15 as, for example, a function or a lookup table for determining the limit value.

  Here, according to the limit value characteristic line 49 shown in FIG. 6, the limit value increases linearly with respect to the actual accelerator operation amount. Good. In any case, this limit value is caused by an increase in the engine speed caused by the increase in the control accelerator operation amount 11b at an increase rate per hour corresponding to the limit value. (Increase) is set within a range of a low rate of increase per hour so that it follows sufficiently.

  When the limit value shown in FIG. 6 is used, the actual accelerator operation amount increases to a certain value at a high speed at a stroke as in the example shown in FIG. 5 (so-called “stepping” of the accelerator pedal). In this case, the control accelerator operation amount increases at a constant rate of increase per time corresponding to the certain value. On the other hand, when the actual accelerator operation amount increases over time (so-called “depressing the accelerator pedal”), the control accelerator operation amount increases at an increasing rate per time. It will follow.

  FIG. 7 shows an example of a change in the actual accelerator operation amount 5a over time and an example of a change in the control accelerator operation amount 11b corresponding to the change.

  For example, the actual accelerator operation amount 5a has increased from time t0 at a high rate of increase per hour (that is, higher than a preset limit value) such that the operation of the HST pump 23 cannot follow without delay. (For example, when the vehicle is started or accelerated with the accelerator pedal 5 fully depressed). Then, the control accelerator operation amount 11b increases at an increase rate per hour corresponding to the limit value described above. As described above, the rate of increase per hour (that is, the limit value) is a low value that can follow the operation of the HST pump 23 without delay. Therefore, the control accelerator operation amount 11b increases more slowly than the actual accelerator operation amount 5a.

  Thereafter, for example, when the control accelerator operation amount 11b reaches the current actual accelerator operation amount 5a at time t1, the increase in the control accelerator operation amount 11b stops.

  Thereafter, if the actual accelerator operation amount 5a does not increase again at a higher rate of increase than the limit value, that is, for example, the actual accelerator operation amount 5a is constant (for example, time intervals t1 to t2, t3 to t4). If there is a decrease (for example, a time interval t2 to t3), or if it increases at an increase rate per hour equal to or less than the limit value, the control accelerator operation amount 11b becomes a value equal to the actual accelerator operation amount 5a.

  Further, for example, at time t4, if the actual accelerator operation amount 5a increases again at a high rate of increase per hour that the HST pump 23 cannot follow without delay, the control accelerator operation amount 11b again corresponds to the limit value. (Ie, the operation of the HST pump 23 is low so that the operation can be followed without delay) and increases toward the current actual accelerator operation amount 5a at an increasing rate per time.

  In this way, whenever the actual accelerator operation amount 5a increases at a high rate of increase per hour so that the operation of the HST pump 23 cannot follow without delay, the control accelerator operation amount 11b is always set to the HST pump. 23 increases at a low rate of increase per hour that can be followed without delay.

  In order to generate the control accelerator operation amount 11b as described above, the accelerator operation control unit 15a of the HST controller 15 can perform, for example, a process as shown in FIG.

  That is, the current actual accelerator operation amount 5a is input to the accelerator operation control unit 15a in step S1, and based on the current actual accelerator operation amount 5a in step S2, as illustrated in FIG. In accordance with the limit value characteristic line 49, a limit value of the control accelerator operation amount (that is, a limited rate of increase per hour) is determined. In step S3, the accelerator operation control unit 15a compares the value obtained by adding the limit value obtained in step S2 to the control accelerator operation amount 11b with the actual accelerator operation amount 5a. Is smaller than the actual accelerator operation amount 5a (YES in step S3), the added value is set as a new control accelerator operation amount in step S4. This means that the control accelerator operation amount 11b is increased toward the actual accelerator operation amount 5a at an increase rate per time corresponding to the limit value determined in Step 2. As a result of step S3, if the control accelerator operation amount 11b is not smaller than the actual accelerator operation amount 5a (that is, if it is equal or larger) (NO in step S3), the accelerator operation control unit 15a determines in step S5. The current actual accelerator operation amount 5a is set as a new control accelerator operation amount 11b. This means that the control accelerator operation amount 11b is matched with the current actual accelerator operation amount 5a. In step S6, the accelerator operation control unit 15a outputs the new accelerator operation amount 5a determined as described above to the engine controller 11.

  As a result of the above processing, when the actual accelerator operation amount 5a is decreased from the state where the control accelerator operation amount 11b is equal to the actual accelerator operation amount 5a or increased at an increase rate per hour equal to or less than the limit value, The control accelerator operation amount 11b changes with the actual accelerator operation amount 5a and maintains the same state. For example, when the actual accelerator operation amount 5a increases at an increase rate per hour that is higher than the limit value, the control accelerator operation amount 11b is set to an increase rate per hour corresponding to the limit value (that is, the actual accelerator operation amount). Increase more slowly than 5a).

  As a modification, the accelerator operation control unit 15a can perform the process shown in FIG. 9 instead of the process shown in FIG.

  That is, the current actual accelerator operation amount 5a is input to the accelerator operation control unit 15a in step S11, and based on the current actual accelerator operation amount 5a in step S12, as illustrated in FIG. In accordance with the limit value characteristic line 49, a limit value of the control accelerator operation amount (that is, a limited rate of increase per hour) is determined. In step S13, the accelerator operation control unit 15a compares the control accelerator operation amount 11b with the actual accelerator operation amount 5a. As a result, the current control accelerator operation amount 11b is greater than the current actual accelerator operation amount 5a. If it is smaller, in step S14, the rate of increase per unit time (the above limit value) determined in step S12 is added to the current control accelerator operation amount, and the added value becomes the new control accelerator operation amount. This means that the control accelerator operation amount 11b is increased by the limit value (the rate of increase per limited time) determined in Step 12. As a result of step S13, if the control accelerator operation amount 11b is not smaller than the actual accelerator operation amount 5a (that is, if it is equal or larger), the accelerator operation control unit 15a determines in step S15 the current actual accelerator operation amount. The operation amount 5a is set as a new control accelerator operation amount 11b. This means that the control accelerator operation amount 11b is matched with the current actual accelerator operation amount 5a. In step S16, the accelerator operation control unit 15a outputs the new accelerator operation amount 5a determined as described above to the engine controller 11.

  Reference is again made to FIG. The engine controller 11a of the engine controller 11 controls the maximum absorption torque of the HST pump 23 along the maximum absorption torque characteristic line 53 shown in FIG. 3 according to the control accelerator operation amount 11b. Therefore, when the actual accelerator operation amount 5a suddenly increases due to start or acceleration, the control accelerator operation amount 11b increases at a low rate of increase per hour so that the HST pump 23 can follow up. Therefore, in this case, the actual absorption torque of the HST pump 23 rises substantially along the maximum absorption torque characteristic line 53 shown in FIG. 3, following the gradual increase in the control accelerator operation amount 11b. . As a result, there is no so-called blow-up of the engine 13, and the engine 13 can operate in a relatively good fuel efficiency region (region of high engine output torque at a relatively low engine speed in FIG. 3). In addition, since the engine speed does not increase to a very high value, the problem of excessive acceleration at the start is also improved.

  In particular, in a forklift, when the power train 10 according to the present embodiment is applied, the effect of solving the two problems described above is clear. The forklift equipped with the powertrain 10 according to the present embodiment has little popping feeling (excessive acceleration feeling) at the time of starting even if such an accelerator pedal operation is performed at the time of starting, and obtains a fuel efficiency effect. be able to.

  As mentioned above, although preferred embodiment of this invention was described, this is an illustration for description of this invention, and is not the meaning which limits the scope of the present invention only to this embodiment. The present invention can be implemented in various modes different from the above-described embodiments without departing from the gist thereof. For example, a plurality of functions of the engine controller 11 and the HST controller 15 of the above embodiment may be performed centrally by a single controller, or may be performed in a distributed manner by more controllers. . In addition, some functions of the engine controller 11 of the above embodiment may be moved to the HST controller 15, or some functions of the HST controller 15 of the above embodiment may be moved to the engine controller 11. Also good. Moreover, the same problem can be solved by applying the present invention not only to forklifts but also to cargo handling vehicles such as wheel loaders and crane cars. Furthermore, not only vehicles that are configured to be able to use power from the engine for driving wheels via a hydraulic pump and a hydraulic motor, but also a device that requires some rotational drive for power from the engine via a hydraulic pump and a hydraulic motor. The present invention can also be applied to an industrial machine configured to transmit to the machine.

DESCRIPTION OF SYMBOLS 1 Forklift 3 Drive wheel 5 Accelerator pedal 5a Actual accelerator operation amount 7 Forward / reverse switching lever 9 Output shaft 10 Vehicle 11 Engine controller 11a Engine controller 11b Accelerator operation amount for control 13 Engine 14 Rotational speed sensor 15 HST controller 15a Accelerator operation control Part 15b Pump control part 17, 18 EPC valve for HST pump 20 Pump capacity variable unit 21 HST
23 HST pump 25 HST motor 31 Drive wheel system

Claims (13)

In a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Wherein in response to the control accelerator operation amount from the accelerator operation control means, and a engine control means for controlling said engine
The accelerator operation control means compares the actual accelerator operation amount with a value obtained by adding the limit value to the control accelerator operation amount, and outputs the smaller value as a new control accelerator operation amount. A vehicle configured as follows . In a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means.
The accelerator operation control means includes
The actual accelerator operation amount is compared with the control accelerator operation amount. If the former is larger than the latter, a value obtained by adding the limit value to the control accelerator operation amount is set as the new control accelerator operation amount. A vehicle configured to output, otherwise output the former as a new control accelerator operation amount. In a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means.
The limit value is a range in which an increase in the capacity of the hydraulic pump can follow an increase in the engine rotational speed caused by an increase in the control accelerator operation amount at an increase rate per hour corresponding to the limit value. The vehicle set in. In a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means.
The vehicle, wherein the limit value is set such that the limit value increases as the current actual accelerator operation amount increases in accordance with the current actual accelerator operation amount. The vehicle according to any one of claims 1 to 4 , wherein the vehicle is configured as a forklift. In a control method for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control step for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
An engine control step for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control step, and
In the accelerator operation control step, the actual accelerator operation amount is compared with a value obtained by adding the limit value to the control accelerator operation amount, and the smaller value is output as a new control accelerator operation amount. , Control method. In a control method for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control step for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
An engine control step for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control step , and
In the accelerator operation control step,
The actual accelerator operation amount is compared with the control accelerator operation amount. If the former is larger than the latter, a value obtained by adding the limit value to the control accelerator operation amount is set as the new control accelerator operation amount. A control method for outputting, and otherwise outputting the former as a new control accelerator operation amount . In a control method for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control step for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
An engine control step for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control step, and
The limit value is a range in which an increase in the capacity of the hydraulic pump can follow an increase in the engine rotational speed caused by an increase in the control accelerator operation amount at an increase rate per hour corresponding to the limit value. Control method set in In a control method for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control step for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
An engine control step for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control step, and
The control method is such that the limit value is set such that the limit value increases as the current actual accelerator operation amount increases in accordance with the current actual accelerator operation amount. In a control device for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means, and
The accelerator operation control means compares the actual accelerator operation amount with a value obtained by adding the limit value to the control accelerator operation amount, and outputs the smaller value as a new control accelerator operation amount. A control device configured as described above. In a control device for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means, and
The accelerator operation control means includes
The actual accelerator operation amount is compared with the control accelerator operation amount. If the former is larger than the latter, a value obtained by adding the limit value to the control accelerator operation amount is set as the new control accelerator operation amount. A control device configured to output, otherwise output the former as a new control accelerator operation amount. In a control device for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means, and
The limit value is a range in which an increase in the capacity of the hydraulic pump can follow an increase in the engine rotational speed caused by an increase in the control accelerator operation amount at an increase rate per hour corresponding to the limit value. Control device set in. In a control device for a vehicle having an engine, a variable displacement hydraulic pump driven by the engine, a hydraulic motor driven by the hydraulic pump, and a load device driven by the hydraulic motor,
An accelerator operation control means for generating a control accelerator operation amount by inputting an actual accelerator operation amount and limiting an increase rate per hour of the actual accelerator operation amount to a preset limit value;
Engine control means for controlling the engine in accordance with the control accelerator operation amount from the accelerator operation control means, and
The control device, wherein the limit value is set so that the limit value increases as the current actual accelerator operation amount increases, according to the actual actual accelerator operation amount.

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